IDIX / Idenix Pharmaceuticals Inc - SEC-arkiveringar, Årsredovisning, Fullmaktsutlåtande

Idenix Pharmaceuticals Inc
US ˙ NASDAQ
DENNA SYMBOL ÄR INTE LÄNGRE AKTIV

Grundläggande statistik
CIK 1093649
SEC Filings
All companies that sell securities in the United States must register with the Securities and Exchange Commission (SEC) and file reports on a regular basis. These reports include company annual reports (10K, 10Q), news updates (8K), investor presentations (found in 8Ks), insider trades (form 4), ownership reports (13D, and 13G), and reports related to the specific securities sold, such as registration statements and prospectus. This page shows recent SEC filings related to Idenix Pharmaceuticals Inc
SEC Filings (Chronological Order)
Denna sida innehåller en komplett, kronologisk lista över SEC-arkiveringar, exklusive ägande-arkiveringar som vi tillhandahåller på andra ställen.
August 15, 2014 15-12G

IDIX / Idenix Pharmaceuticals Inc 15-12G - - FORM 15

Form 15 UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 15 CERTIFICATION AND NOTICE OF TERMINATION OF REGISTRATION UNDER SECTION 12(g) OF THE SECURITIES EXCHANGE ACT OF 1934 OR SUSPENSION OF DUTY TO FILE REPORTS UNDER SECTIONS 13 AND 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934. Commission File Number: 000-49839 Idenix Pharmaceuticals, Inc. (Exact name of registrant as

August 12, 2014 SC 13D/A

IDIX / Idenix Pharmaceuticals Inc / NOVARTIS AG - SC 13D/A Activist Investment

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13D Under the Securities Exchange Act of 1934 (Amendment No. 11)* Idenix Pharmaceuticals, Inc. (Name of Issuer) Common Stock (Title of Class of Securities) 45166R204 (CUSIP Number) Rebecca Weston Novartis Pharma AG Lichtstrasse 35 CH-4056 Basel, Switzerland +41 61 324 7015 With a copy to: Peter Harwich Allen & Overy L

August 12, 2014 SC 13D/A

IDIX / Idenix Pharmaceuticals Inc / Baupost Group LLC/MA - IDIX13DAMEND2.PDML Activist Investment

SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13D Under the Securities Exchange Act of 1934 (Amendment No. 2) Idenix Pharmaceuticals, Inc. (Name of Issuer) Common Stock (Title Class of Securities) 45166R204 (Cusip Number) Seth A. Klarman The Baupost Group, L.L.C. 10 St. James Avenue, Suite 1700 Boston, Massachusetts 02116 (617) 210-8300 With a copy to: Jeffrey R. Katz, Esq Rop

August 6, 2014 SC TO-T/A

IDIX / Idenix Pharmaceuticals Inc / Merck & Co., Inc. - AMENDMENT NO. 8 TO SCHEDULE TO

Amendment No. 8 to Schedule TO UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE TO TENDER OFFER STATEMENT UNDER SECTION 14(D)(1) OR 13(E)(1) OF THE SECURITIES EXCHANGE ACT OF 1934 (Amendment No. 8) IDENIX PHARMACEUTICALS, INC. (Name of Subject Company (Issuer)) IMPERIAL BLUE CORPORATION (Offeror) a wholly owned subsidiary of MERCK & CO., INC. (Offeror) (Names of Fil

August 5, 2014 8-K

Changes in Control of Registrant, Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers, Amendments to Articles of Incorporation or Bylaws; Change in Fiscal Year, Material Modification to Rights of Security Holders, Notice of Delisting or Failure to Satisfy a Continued Listing Rule or Standard; Transfer of Listing, Financial Statements and Exhibits, Completion of Acquisition or Disposition of Assets

Form 8-K UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): August 4, 2014 IDENIX PHARMACEUTICALS, INC. (Exact name of registrant as specified in its charter) Delaware 000-49839 45-0478605 (State or other jurisdiction of incorporation

August 5, 2014 S-8 POS

IDIX / Idenix Pharmaceuticals Inc S-8 POS - - S-8 POS

S-8 POS As filed with the Securities and Exchange Commission on August 5, 2014 Registration No.

August 5, 2014 SC 14D9/A

IDIX / Idenix Pharmaceuticals Inc SC 14D9/A - - AMENDMENT NO. 7 TO SCHEDULE 14D-9

Amendment No. 7 to Schedule 14D-9 UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14D-9 SOLICITATION/RECOMMENDATION STATEMENT UNDER SECTION 14(d)(4) OF THE SECURITIES EXCHANGE ACT OF 1934 (Amendment No. 7) Idenix Pharmaceuticals, Inc. (Name of Subject Company) Idenix Pharmaceuticals, Inc. (Names of Persons Filing Statement) COMMON STOCK, PAR VALUE $0.001 PER SHARE

August 5, 2014 S-8 POS

IDIX / Idenix Pharmaceuticals Inc S-8 POS - - S-8 POS

S-8 POS As filed with the Securities and Exchange Commission on August 5, 2014 Registration No.

August 5, 2014 EX-3.1

RESTATED CERTIFICATE OF INCORPORATION IDENIX PHARMACEUTICALS, INC.

EX-3.1 Exhibit 3.1 RESTATED CERTIFICATE OF INCORPORATION OF IDENIX PHARMACEUTICALS, INC. FIRST: The name of the corporation is Idenix Pharmaceuticals, Inc. (hereinafter, the “Corporation”). SECOND: The address of the corporation’s registered office is Corporation Trust Center, 1209 Orange Street, Wilmington, New Castle County, Delaware 19801, and the name of its registered agent at such address is

August 5, 2014 S-8 POS

IDIX / Idenix Pharmaceuticals Inc S-8 POS - - S-8 POS

S-8 POS As filed with the Securities and Exchange Commission on August 5, 2014 Registration No.

August 5, 2014 S-8 POS

IDIX / Idenix Pharmaceuticals Inc S-8 POS - - S-8 POS

S-8 POS As filed with the Securities and Exchange Commission on August 5, 2014 Registration No.

August 5, 2014 EX-99.(A)(1)(J)

Merck Completes Tender Offer to Acquire Idenix

EX-99.(a)(1)(J) Exhibit 99.(a)(1)(J) News Release FOR IMMEDIATE RELEASE Media Contacts: Pamela Eisele (267) 305-3558 Steve Cragle (908) 423-3461 Investor Contacts: Joe Romanelli (908) 423-5185 Justin Holko (908) 423-5088 Merck Completes Tender Offer to Acquire Idenix WHITEHOUSE STATION, N.J., Aug. 5, 2014 – Merck (NYSE: MRK), known as MSD outside the United States and Canada, announced the success

August 5, 2014 SC TO-T/A

IDIX / Idenix Pharmaceuticals Inc / Merck & Co., Inc. - AMENDMENT NO. 7

Amendment No. 7 UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE TO TENDER OFFER STATEMENT UNDER SECTION 14(D)(1) OR 13(E)(1) OF THE SECURITIES EXCHANGE ACT OF 1934 (Amendment No. 7) IDENIX PHARMACEUTICALS, INC. (Name of Subject Company (Issuer)) IMPERIAL BLUE CORPORATION (Offeror) a wholly owned subsidiary of MERCK & CO., INC. (Offeror) (Names of Filing Persons (id

August 5, 2014 S-8 POS

IDIX / Idenix Pharmaceuticals Inc S-8 POS - - S-8 POS

S-8 POS As filed with the Securities and Exchange Commission on August 5, 2014 Registration No.

August 5, 2014 S-8 POS

IDIX / Idenix Pharmaceuticals Inc S-8 POS - - S-8 POS

S-8 POS As filed with the Securities and Exchange Commission on August 5, 2014 Registration No.

August 5, 2014 EX-3.2

THIRD AMENDED AND RESTATED BYLAWS IDENIX PHARMACEUTICALS, INC. ARTICLE I - STOCKHOLDERS

EX-3.2 Exhibit 3.2 THIRD AMENDED AND RESTATED BYLAWS OF IDENIX PHARMACEUTICALS, INC. ARTICLE I - STOCKHOLDERS Section 1. Annual Meeting. An annual meeting of the stockholders, for the election of directors to succeed those whose terms expire and for the transaction of such other business as may properly come before the meeting, shall be held at such place, on such date, and at such time as the Boa

July 31, 2014 8-K

Financial Statements and Exhibits, Results of Operations and Financial Condition

Form 8-K UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): July 31, 2014 Idenix Pharmaceuticals, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 000-49839 45-0478605 (State or Other Jurisdiction of Incorporation (Com

July 31, 2014 EX-10.1

THIRD AMENDMENT TO LEASE

EX-10.1 Exhibit 10.1 THIRD AMENDMENT TO LEASE THIS THIRD AMENDMENT TO LEASE (this “Amendment”) is entered into as of this 29th day of May, 2014, by and between BMR-ROGERS STREET LLC, a Delaware limited liability company (“Landlord”), and IDENIX PHARMACEUTICALS, INC., a Delaware corporation (“Tenant”). RECITALS A. WHEREAS, Landlord and Tenant entered into that certain Lease dated as of September 25

July 31, 2014 EX-99.1

IDENIX PHARMACEUTICALS REPORTS SECOND QUARTER AND SIX MONTH 2014 FINANCIAL RESULTS

EX-99.1 Exhibit 99.1 FOR IMMEDIATE RELEASE Idenix Pharmaceuticals Contact: Teri Dahlman (617) 995-9807 IDENIX PHARMACEUTICALS REPORTS SECOND QUARTER AND SIX MONTH 2014 FINANCIAL RESULTS CAMBRIDGE, Mass., July 31, 2014 — Idenix Pharmaceuticals, Inc. (NASDAQ: IDIX), a biopharmaceutical company engaged in the discovery and development of drugs for the treatment of human viral diseases, today reported

July 31, 2014 10-Q

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

Form 10-Q Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.

July 29, 2014 SC 13D/A

IDIX / Idenix Pharmaceuticals Inc / NOVARTIS AG - SC 13D/A Activist Investment

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13D Under the Securities Exchange Act of 1934 (Amendment No. 10)* Idenix Pharmaceuticals, Inc. (Name of Issuer) Common Stock (Title of Class of Securities) 45166R204 (CUSIP Number) Rebecca Weston Novartis Pharma AG Lichtstrasse 35 CH-4056 Basel, Switzerland +41 61 324 7015 With a copy to: Peter Harwich Allen & Overy L

July 24, 2014 SC TO-T/A

IDIX / Idenix Pharmaceuticals Inc / Merck & Co., Inc. - SC TO-T/A

SC TO-T/A UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE TO TENDER OFFER STATEMENT UNDER SECTION 14(D)(1) OR 13(E)(1) OF THE SECURITIES EXCHANGE ACT OF 1934 (Amendment No. 6) IDENIX PHARMACEUTICALS, INC. (Name of Subject Company (Issuer)) IMPERIAL BLUE CORPORATION (Offeror) a wholly owned subsidiary of MERCK & CO., INC. (Offeror) (Names of Filing Persons (identify

July 24, 2014 SC 14D9/A

IDIX / Idenix Pharmaceuticals Inc SC 14D9/A - - SC 14D9/A

SC 14D9/A UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14D-9 SOLICITATION/RECOMMENDATION STATEMENT UNDER SECTION 14(D)(4) OF THE SECURITIES EXCHANGE ACT OF 1934 (Amendment No. 6) Idenix Pharmaceuticals, Inc. (Name of Subject Company) Idenix Pharmaceuticals, Inc. (Names of Persons Filing Statement) COMMON STOCK, PAR VALUE $0.001 PER SHARE (Title of Class of Secur

July 21, 2014 SC TO-T/A

IDIX / Idenix Pharmaceuticals Inc / Merck & Co., Inc. - SC TO-T/A

SC TO-T/A UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE TO TENDER OFFER STATEMENT UNDER SECTION 14(D)(1) OR 13(E)(1) OF THE SECURITIES EXCHANGE ACT OF 1934 (Amendment No. 5) IDENIX PHARMACEUTICALS, INC. (Name of Subject Company (Issuer)) IMPERIAL BLUE CORPORATION (Offeror) a wholly owned subsidiary of MERCK & CO., INC. (Offeror) (Names of Filing Persons (identify

July 21, 2014 SC 14D9/A

IDIX / Idenix Pharmaceuticals Inc SC 14D9/A - - SC 14D9/A- AMENDMENT NO. 5

SC 14D9/A- Amendment No. 5 UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14D-9 SOLICITATION/RECOMMENDATION STATEMENT UNDER SECTION 14(d)(4) OF THE SECURITIES EXCHANGE ACT OF 1934 (Amendment No. 5) Idenix Pharmaceuticals, Inc. (Name of Subject Company) Idenix Pharmaceuticals, Inc. (Names of Persons Filing Statement) COMMON STOCK, PAR VALUE $0.001 PER SHARE (Title

July 11, 2014 SC TO-T/A

IDIX / Idenix Pharmaceuticals Inc / Merck & Co., Inc. - AMENDMENT NO. 4

Amendment No. 4 UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE TO TENDER OFFER STATEMENT UNDER SECTION 14(D)(1) OR 13(E)(1) OF THE SECURITIES EXCHANGE ACT OF 1934 (Amendment No. 4) IDENIX PHARMACEUTICALS, INC. (Name of Subject Company (Issuer)) IMPERIAL BLUE CORPORATION (Offeror) a wholly owned subsidiary of MERCK & CO., INC. (Offeror) (Names of Filing Persons (id

July 11, 2014 SC 14D9/A

IDIX / Idenix Pharmaceuticals Inc SC 14D9/A - - SC 14D9/A - AMENDMENT NO. 4

SC 14D9/A - Amendment No. 4 UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14D-9 SOLICITATION/RECOMMENDATION STATEMENT UNDER SECTION 14(d)(4) OF THE SECURITIES EXCHANGE ACT OF 1934 (Amendment No. 4) Idenix Pharmaceuticals, Inc. (Name of Subject Company) Idenix Pharmaceuticals, Inc. (Names of Persons Filing Statement) COMMON STOCK, PAR VALUE $0.001 PER SHARE (Title

July 3, 2014 SC 14D9/A

IDIX / Idenix Pharmaceuticals Inc SC 14D9/A - - SC 14D9/A (AMENDMENT NO. 3)

SC 14D9/A (Amendment No. 3) UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14D-9 SOLICITATION/RECOMMENDATION STATEMENT UNDER SECTION 14(d)(4) OF THE SECURITIES EXCHANGE ACT OF 1934 (Amendment No. 3) Idenix Pharmaceuticals, Inc. (Name of Subject Company) Idenix Pharmaceuticals, Inc. (Names of Persons Filing Statement) COMMON STOCK, PAR VALUE $0.001 PER SHARE (Title

July 3, 2014 SC TO-T/A

IDIX / Idenix Pharmaceuticals Inc / Merck & Co., Inc. - SC TO-T/A

SC TO-T/A UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE TO TENDER OFFER STATEMENT UNDER SECTION 14(D)(1) OR 13(E)(1) OF THE SECURITIES EXCHANGE ACT OF 1934 (Amendment No. 3) IDENIX PHARMACEUTICALS, INC. (Name of Subject Company (Issuer)) IMPERIAL BLUE CORPORATION (Offeror) a wholly owned subsidiary of MERCK & CO., INC. (Offeror) (Names of Filing Persons (identify

June 27, 2014 SC 14D9/A

- SC 14D9/A (AMENDMENT NO. 2)

SC 14D9/A (Amendment No. 2) UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14D-9 SOLICITATION/RECOMMENDATION STATEMENT UNDER SECTION 14(d)(4) OF THE SECURITIES EXCHANGE ACT OF 1934 (Amendment No. 2) Idenix Pharmaceuticals, Inc. (Name of Subject Company) Idenix Pharmaceuticals, Inc. (Names of Persons Filing Statement) COMMON STOCK, PAR VALUE $0.001 PER SHARE (Title

June 27, 2014 SC TO-T/A

IDIX / Idenix Pharmaceuticals Inc / Merck & Co., Inc. - AMENDMENT NO. 2

Amendment No. 2 UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE TO TENDER OFFER STATEMENT UNDER SECTION 14(D)(1) OR 13(E)(1) OF THE SECURITIES EXCHANGE ACT OF 1934 (Amendment No. 2) IDENIX PHARMACEUTICALS, INC. (Name of Subject Company (Issuer)) IMPERIAL BLUE CORPORATION (Offeror) a wholly owned subsidiary of MERCK & CO., INC. (Offeror) (Names of Filing Persons (id

June 26, 2014 SC 14D9/A

- AMENDMENT NO.1 TO SCHEDULE 14D-9

Amendment No.1 to Schedule 14D-9 UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14D-9 SOLICITATION/RECOMMENDATION STATEMENT UNDER SECTION 14(d)(4) OF THE SECURITIES EXCHANGE ACT OF 1934 (Amendment No. 1) Idenix Pharmaceuticals, Inc. (Name of Subject Company) Idenix Pharmaceuticals, Inc. (Names of Persons Filing Statement) COMMON STOCK, PAR VALUE $0.001 PER SHARE (

June 26, 2014 SC TO-T/A

IDIX / Idenix Pharmaceuticals Inc / Merck & Co., Inc. - SC TO-T/A

SC TO-T/A UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE TO TENDER OFFER STATEMENT UNDER SECTION 14(D)(1) OR 13(E)(1) OF THE SECURITIES EXCHANGE ACT OF 1934 (Amendment No. 1) IDENIX PHARMACEUTICALS, INC. (Name of Subject Company (Issuer)) IMPERIAL BLUE CORPORATION (Offeror) a wholly owned subsidiary of MERCK & CO., INC. (Offeror) (Names of Filing Persons (identify

June 20, 2014 EX-99.(A)(1)(D)

Offer To Purchase For Cash All Outstanding Shares of Common Stock IDENIX PHARMACEUTICALS, INC. a Delaware corporation $24.50 NET PER SHARE Pursuant to the Offer to Purchase dated June 20, 2014 IMPERIAL BLUE CORPORATION a wholly-owned subsidiary of ME

Letter of Brokers, Dealers Exhibit (a)(1)(D) Offer To Purchase For Cash All Outstanding Shares of Common Stock of IDENIX PHARMACEUTICALS, INC.

June 20, 2014 EX-99.(A)(1)(C)

NOTICE OF GUARANTEED DELIVERY For Tender of Shares of Common Stock IDENIX PHARMACEUTICALS, INC. a Delaware corporation $24.50 NET PER SHARE Pursuant to the Offer to Purchase dated June 20, 2014 IMPERIAL BLUE CORPORATION a wholly-owned subsidiary of M

Notice of Guaranteed Delivery Exhibit (a)(1)(C) NOTICE OF GUARANTEED DELIVERY For Tender of Shares of Common Stock of IDENIX PHARMACEUTICALS, INC.

June 20, 2014 SC 14D9

- SCHEDULE 14D-9

Schedule 14D-9 Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.

June 20, 2014 EX-99.(A)(1)(F)

Notice of Offer to Purchase for Cash All Outstanding Shares of Common Stock IDENIX PHARMACEUTICALS, INC. a Delaware corporation $24.50 NET PER SHARE Pursuant to the Offer to Purchase dated June 20, 2014 IMPERIAL BLUE CORPORATION a wholly owned subsid

Summary Advertisement as published on June 20, 2014 Exhibit (a)(1)(F) This announcement is neither an offer to purchase nor a solicitation of an offer to sell Shares (as defined below), and the provisions herein are subject in their entirety to the provisions of the Offer (as defined below).

June 20, 2014 EX-99.(A)(1)(I)

Merck Begins Tender Offer to Acquire Idenix

Press Release dated June 20, 2014 Exhibit (a)(1)(I) News Release DRAFT: 6/18/2014 FOR IMMEDIATE RELEASE Media Contacts: Pamela Eisele Investor Contacts: Joe Romanelli (267) 305-3558 Steve Cragle (908) 423-3461 (908) 423-5185 Justin Holko (908) 423-5088 Merck Begins Tender Offer to Acquire Idenix WHITEHOUSE STATION, N.

June 20, 2014 EX-99.(A)(1)(E)

Offer To Purchase For Cash All Outstanding Shares of Common Stock IDENIX PHARMACEUTICALS, INC. a Delaware corporation $24.50 NET PER SHARE Pursuant to the Offer to Purchase dated June 20, 2014 IMPERIAL BLUE CORPORATION a wholly-owned subsidiary of ME

Letter to Clients for use by Brokers, Dealers Exhibit (a)(1)(E) Offer To Purchase For Cash All Outstanding Shares of Common Stock of IDENIX PHARMACEUTICALS, INC.

June 20, 2014 EX-99.(A)(1)(B)

LETTER OF TRANSMITTAL To Tender Shares of Common Stock IDENIX PHARMACEUTICALS, INC. a Delaware corporation $24.50 NET PER SHARE Pursuant to the Offer to Purchase dated June 20, 2014 IMPERIAL BLUE CORPORATION a wholly owned subsidiary of MERCK & CO.,

Letter of Transmittal Exhibit (a)(1)(B) LETTER OF TRANSMITTAL To Tender Shares of Common Stock of IDENIX PHARMACEUTICALS, INC.

June 20, 2014 EX-99.(A)(1)(A)

Offer to Purchase for Cash All Outstanding Shares of Common Stock Idenix Pharmaceuticals, Inc. $24.50 Net Per Share Imperial Blue Corporation a wholly-owned subsidiary of Merck & Co., Inc. THE OFFER AND WITHDRAWAL RIGHTS WILL EXPIRE AT 5:00 P.M. EAST

Offer to Purchase, dated June 20, 2014 Table of Contents Exhibit (a)(1)(A) Offer to Purchase for Cash All Outstanding Shares of Common Stock of Idenix Pharmaceuticals, Inc.

June 20, 2014 SC TO-T

- SCHEDULE TO

Schedule TO UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 SCHEDULE TO (RULE 14D-100) Tender Offer Statement Pursuant to Section 14(d)(1) or 13(e)(1) of the Securities Exchange Act of 1934 IDENIX PHARMACEUTICALS, INC. (Name of Subject Company) IMPERIAL BLUE CORPORATION (Offeror) MERCK & CO., INC. (Parent of Offeror) (Names of Filing Persons) COMMON STOCK, $0.001 PAR VALUE

June 17, 2014 8-K

Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers, Financial Statements and Exhibits

Form 8-K UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of The Securities Exchange Act of 1934 Date of report (Date of earliest event reported): June 17, 2014 IDENIX PHARMACEUTICALS, INC. (Exact name of registrant as specified in its charter) Delaware 000-49839 45-0478605 (State or other jurisdiction of incorporation

June 17, 2014 EX-10.1

Appendix A

EX-10.1 Exhibit 10.1 [IDENIX LETTERHEAD] November 23, 2010 CONFIDENTIAL Paul Fanning 17 Stable Way Medway, MA 02053 Dear Paul: This restatement to your Employment Letter of February 24, 2004, is made this 23rd day of November, 2010 between you and Idenix Pharmaceuticals, Inc., a corporation incorporated under the laws of the State of Delaware (together with its successors and assigns, the “Company

June 13, 2014 EX-99.1

Joint Filing Agreement

Exhibit 99.1 Joint Filing Agreement In accordance with Rule 13d-1(k)(1) under the Securities Exchange Act of 1934, as amended, the persons named below agree to the joint filing on behalf of each of them of a statement on Schedule 13D (including amendments thereto) with respect to the common stock, par value $0.001 per share, of Idenix Pharmaceuticals, Inc., a Delaware corporation, and further agre

June 13, 2014 SC 13D

IDIX / Idenix Pharmaceuticals Inc / Merck & Co., Inc. - SC 13D Activist Investment

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13D Under the Securities Exchange Act of 1934 Idenix Pharmaceuticals, Inc. (Name of Issuer) Common Stock, par value $0.001 (Title of Class of Securities) 45166R 20 4 (CUSIP Number) Copies to: Geralyn S. Ritter Senior Vice President, Global Public Policy and Corporate Responsibility, Secretary and Assistant General Cou

June 12, 2014 SC14D9C

- SC14D9C

SC14D9C UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14D-9 SOLICITATION/RECOMMENDATION STATEMENT UNDER SECTION 14(d)(4) OF THE SECURITIES EXCHANGE ACT OF 1934 Idenix Pharmaceuticals, Inc. (Name of Subject Company) Idenix Pharmaceuticals, Inc. (Names of Persons Filing Statement) COMMON STOCK, PAR VALUE $0.001 PER SHARE (Title of Class of Securities) 45166R204 (CU

June 12, 2014 SC TO-C

- SC TO-C

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE TO TENDER OFFER STATEMENT UNDER SECTION 14(D)(1) OR 13(E)(1) OF THE SECURITIES EXCHANGE ACT OF 1934 IDENIX PHARMACEUTICALS, INC. (Name of Subject Company (Issuer)) IMPERIAL BLUE CORPORATION (Offeror) a wholly owned subsidiary of MERCK & CO., INC. (Offeror) (Names of Filing Persons (identifying status as offeror, issue

June 9, 2014 EX-99.(A)(2)

Merck Announces Acquisition of Idenix

EX-99.(A)(2) 3 d740687dex99a2.htm EX-99.(A)(2) Exhibit (a)(2) Merck Announces Acquisition of Idenix June 9, 2014 Forward-Looking Statement This presentation includes “forward-looking statements” within the meaning of the safe harbor provisions of the United States Private Securities Litigation Reform Act of 1995. Forward looking statements include statements regarding the timing and closing of the

June 9, 2014 8-K

Entry into a Material Definitive Agreement, Financial Statements and Exhibits, Other Events

8-K 1 d740878d8k.htm 8-K UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): June 8, 2014 Idenix Pharmaceuticals, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 000-49839 45-0478605 (State or Other Jurisdiction of Inc

June 9, 2014 SC14D9C

- SC14D9C - Q&A

SC14D9C - Q&A UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14D-9 SOLICITATION/RECOMMENDATION STATEMENT UNDER SECTION 14(d)(4) OF THE SECURITIES EXCHANGE ACT OF 1934 Idenix Pharmaceuticals, Inc. (Name of Subject Company) Idenix Pharmaceuticals, Inc. (Names of Persons Filing Statement) COMMON STOCK, PAR VALUE $0.001 PER SHARE (Title of Class of Securities) 45166R2

June 9, 2014 SC14D9C

- SC14D9C

SC14D9C UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14D-9 SOLICITATION/RECOMMENDATION STATEMENT UNDER SECTION 14(d)(4) OF THE SECURITIES EXCHANGE ACT OF 1934 Idenix Pharmaceuticals, Inc. (Name of Subject Company) Idenix Pharmaceuticals, Inc. (Names of Persons Filing Statement) COMMON STOCK, PAR VALUE $0.001 PER SHARE (Title of Class of Securities) 45166R204 (CU

June 9, 2014 EX-99.1

SUPPORT AGREEMENT

EX-99.1 Exhibit 99.1 SUPPORT AGREEMENT This SUPPORT AGREEMENT (this “Agreement”), dated as of June 8, 2014, is entered into by and among Merck & Co., Inc., a New Jersey corporation (“Parent”), Imperial Blue Corporation, a Delaware corporation and a wholly-owned subsidiary of Parent (“Merger Sub”), and The Baupost Group, L.L.C., a Massachusetts limited liability corporation (the “Stockholder”). All

June 9, 2014 SC14D9C

- SC14D9C - LETTER TO EMPLOYEES

SC14D9C - Letter to Employees UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.

June 9, 2014 EX-99.(A)(1)

Merck to Acquire Idenix Acquisition Expands Portfolio of Promising Investigational Therapies for Hepatitis C

EX-99.(a)(1) Exhibit (a)(1) News Release FOR IMMEDIATE RELEASE Merck Media Contact: Pamela Eisele (267) 305-3558 Investor Contact: Joe Romanelli (908) 423-5185 Steve Cragle (908) 423-3462 Justin Holko (908) 423-5088 Idenix Media/Investor Contact: Teri Dahlman (617) 995-9807 Merck to Acquire Idenix Acquisition Expands Portfolio of Promising Investigational Therapies for Hepatitis C WHITEHOUSE STATI

June 9, 2014 EX-2.1

AGREEMENT AND PLAN OF MERGER IDENIX PHARMACEUTICALS, INC., MERCK & CO., INC. IMPERIAL BLUE CORPORATION Dated as of June 8, 2014 TABLE OF CONTENTS Page ARTICLE I The Offer and the Merger; Closing; Effective Time 1.1 The Offer 2 1.2 Company Action 4 1.

EX-2.1 Exhibit 2.1 AGREEMENT AND PLAN OF MERGER among IDENIX PHARMACEUTICALS, INC., MERCK & CO., INC. and IMPERIAL BLUE CORPORATION Dated as of June 8, 2014 TABLE OF CONTENTS Page ARTICLE I The Offer and the Merger; Closing; Effective Time 1.1 The Offer 2 1.2 Company Action 4 1.3 The Merger 6 1.4 Closing 6 1.5 Effective Time 6 ARTICLE II Certificate of Incorporation and Bylaws of the Surviving Cor

June 9, 2014 EX-99.2

Merck to Acquire Idenix Acquisition Expands Portfolio of Promising Investigational Therapies for Hepatitis C

EX-99.2 Exhibit 99.2 News Release FOR IMMEDIATE RELEASE Merck Media Contact: Pamela Eisele Investor Contact: Joe Romanelli (267) 305-3558 (908) 423-5185 Steve Cragle Justin Holko (908) 423-3462 (908) 423-5088 Idenix Media/Investor Contact: Teri Dahlman (617) 995-9807 Merck to Acquire Idenix Acquisition Expands Portfolio of Promising Investigational Therapies for Hepatitis C WHITEHOUSE STATION, N.J

June 9, 2014 SC TO-C

- SC TO-C

SC TO-C UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE TO TENDER OFFER STATEMENT UNDER SECTION 14(D)(1) OR 13(E)(1) OF THE SECURITIES EXCHANGE ACT OF 1934 Idenix Pharmaceuticals, Inc. (Name of Subject Company (Issuer)) IMPERIAL BLUE CORPORATION (Offeror) A Wholly Owned Subsidiary of MERCK & CO., INC. (Offeror) (Names of Filing Persons (identifying status as offero

June 6, 2014 EX-99.1

IDENIX PHARMACEUTICALS, INC. 2014 EMPLOYEE STOCK PURCHASE PLAN February 11, 2014

EX-99.1 Exhibit 99.1 IDENIX PHARMACEUTICALS, INC. 2014 EMPLOYEE STOCK PURCHASE PLAN February 11, 2014 The purpose of this Plan is to provide eligible employees of Idenix Pharmaceuticals, Inc. (the “Company”) and certain of its subsidiaries with opportunities to purchase shares of the Company’s common stock, $0.001 par value (the “Common Stock”), commencing on July 1, 2014. Two Million (2,000,000)

June 6, 2014 S-8

- FORM S-8

S-8 1 d730518ds8.htm FORM S-8 As filed with the Securities and Exchange Commission on June 6, 2014 Registration No. 333- UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM S-8 REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933 IDENIX PHARMACEUTICALS, INC. (Exact Name of Registrant as Specified in Its Charter) Delaware 45-0478605 (State or Other Jurisdiction of Incorp

June 6, 2014 8-K

Submission of Matters to a Vote of Security Holders - FORM 8-K

FORM 8-K UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of The Securities Exchange Act of 1934 Date of report (Date of earliest event reported): June 5, 2014 IDENIX PHARMACEUTICALS, INC. (Exact name of registrant as specified in its charter) Delaware 000-49839 45-0478605 (State or other jurisdiction of incorporation o

May 1, 2014 EX-99.1

IDENIX PHARMACEUTICALS REPORTS FIRST QUARTER 2014 FINANCIAL RESULTS AND HCV PIPELINE REVIEW

EX-99.1 2 d719370dex991.htm EX-99.1 Exhibit 99.1 FOR IMMEDIATE RELEASE Idenix Pharmaceuticals Contact: Teri Dahlman (617) 995-9807 IDENIX PHARMACEUTICALS REPORTS FIRST QUARTER 2014 FINANCIAL RESULTS AND HCV PIPELINE REVIEW CAMBRIDGE, Mass., May 1, 2014 — Idenix Pharmaceuticals, Inc. (NASDAQ: IDIX), a biopharmaceutical company engaged in the discovery and development of drugs for the treatment of h

May 1, 2014 8-K

Financial Statements and Exhibits, Results of Operations and Financial Condition

8-K 1 d719370d8k.htm FORM 8-K UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): May 1, 2014 Idenix Pharmaceuticals, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 000-49839 45-0478605 (State or Other Jurisdiction of

May 1, 2014 10-Q

Quarterly Report - 10-Q

10-Q Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.

April 30, 2014 CORRESP

-

Acceleration Request IDENIX PHARMACEUTICALS, INC. 320 Bent Street Cambridge, MA 02141 April 30, 2014 Via EDGAR Securities and Exchange Commission Division of Corporation Finance 100 F Street, N.E. Washington, D.C. 20549 Re: Idenix Pharmaceuticals, Inc. Registration Statement on Form S-3 File No. 333-194190 Request for Acceleration Ladies and Gentlemen: Pursuant to Rule 461 promulgated under the Se

April 29, 2014 DEF 14A

- DEF 14A

DEF 14A Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.

April 7, 2014 8-K

Financial Statements and Exhibits, Other Events - FORM 8-K

Form 8-K UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): April 7, 2014 Idenix Pharmaceuticals, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 000-49839 45-0478605 (State or Other Jurisdiction of Incorporation (Com

April 7, 2014 EX-99.1

Idenix Announces Promising Clinical Data and Continued Progress in Nucleotide Prodrug Development Programs for the Treatment of Hepatitis C

EX-99.1 Exhibit 99.1 FOR IMMEDIATE RELEASE Idenix Pharmaceuticals Contact: Teri Dahlman (617) 995-9807 Idenix Announces Promising Clinical Data and Continued Progress in Nucleotide Prodrug Development Programs for the Treatment of Hepatitis C • Idenix Reports Positive Proof-of-Concept Data for Lead Nucleotide Prodrug, IDX21437 • Idenix on Track to Initiate All-Oral Pan-Genotypic Phase II Combinati

April 3, 2014 SC 13D/A

IDIX / Idenix Pharmaceuticals Inc / NOVARTIS AG - SC 13D/A Activist Investment

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13D Under the Securities Exchange Act of 1934 (Amendment No. 9)* Idenix Pharmaceuticals, Inc. (Name of Issuer) Common Stock (Title of Class of Securities) 45166R204 (CUSIP Number) Julie Pender Novartis Pharma AG Lichtstrasse 35 CH-4056 Basel, Switzerland +41 61 696 4509 With a copy to: Peter Harwich Allen & Overy LLP

April 3, 2014 8-K

Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers - FORM 8-K

FORM 8-K UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of The Securities Exchange Act of 1934 Date of report (Date of earliest event reported): March 28, 2014 IDENIX PHARMACEUTICALS, INC. (Exact name of registrant as specified in its charter) Delaware 000-49839 45-0478605 (State or other jurisdiction of incorporation

March 24, 2014 8-K

Financial Statements and Exhibits, Other Events

8-K 1 d700554d8k.htm FORM 8-K UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): March 21, 2014 Idenix Pharmaceuticals, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 000-49839 45-0478605 (State or Other Jurisdiction

March 24, 2014 EX-99.1

Idenix Pharmaceuticals Intends to Appeal Norway District Court Decision Regarding Patent Invalidity Case

EX-99.1 Exhibit 99.1 FOR IMMEDIATE RELEASE Idenix Pharmaceuticals Contact: Teri Dahlman (617) 995-9807 Idenix Pharmaceuticals Intends to Appeal Norway District Court Decision Regarding Patent Invalidity Case CAMBRIDGE, Mass., March 24, 2014 — Idenix Pharmaceuticals, Inc. (NASDAQ: IDIX), a biopharmaceutical company engaged in the discovery and development of drugs for the treatment of human viral d

March 14, 2014 8-K

Financial Statements and Exhibits, Other Events

8-K 1 d695364d8k.htm FORM 8-K UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): March 14, 2014 Idenix Pharmaceuticals, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 000-49839 45-0478605 (State or Other Jurisdiction

March 14, 2014 EX-99.1

IDENIX PHARMACEUTICALS FILES PATENT INFRINGEMENT LAWSUITS AGAINST GILEAD SCIENCES IN EUROPE Granted European Patent Covering 2’-Methyl-2’-Fluoro Nucleosides for Treating Hepatitis C Virus

EX-99.1 Exhibit 99.1 FOR IMMEDIATE RELEASE Idenix Pharmaceuticals Contact: Teri Dahlman [email protected] IDENIX PHARMACEUTICALS FILES PATENT INFRINGEMENT LAWSUITS AGAINST GILEAD SCIENCES IN EUROPE Granted European Patent Covering 2’-Methyl-2’-Fluoro Nucleosides for Treating Hepatitis C Virus CAMBRIDGE, Mass., March 14, 2014 — Idenix Pharmaceuticals, Inc. (NASDAQ: IDIX), a biopharmaceutica

February 27, 2014 8-K

Financial Statements and Exhibits, Results of Operations and Financial Condition

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act Date of Report (Date of earliest event reported): February 27, 2014 Idenix Pharmaceuticals, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 000-49839 45-0478605 (State or Other Jurisdiction of Incorporation (Commission File

February 27, 2014 EX-4.2

IDENIX PHARMACEUTICALS, INC. Dated as of SUBORDINATED DEBT SECURITIES CROSS-REFERENCE TABLE(1) Section of Trust Indenture Act of 1939, as amended Section of Indenture 310(a) 6.09 310(b) 6.08 6.10 310(c) Inapplicable 311(a) 6.13 311(b) 6.13 311(c) Ina

EX-4.2 Exhibit 4.2 IDENIX PHARMACEUTICALS, INC. and Trustee INDENTURE Dated as of SUBORDINATED DEBT SECURITIES CROSS-REFERENCE TABLE(1) Section of Trust Indenture Act of 1939, as amended Section of Indenture 310(a) 6.09 310(b) 6.08 6.10 310(c) Inapplicable 311(a) 6.13 311(b) 6.13 311(c) Inapplicable 312(a) 4.01 4.04 312(b) 4.04(c) 312(c) 4.04(c) 313(a) 4.03 313(b) 4.03 313(c) 4.03 313(d) 4.03 314(

February 27, 2014 S-3

- FORM S-3

Form S-3 Table of Contents As filed with the Securities and Exchange Commission on February 27, 2014 Registration No.

February 27, 2014 EX-4.4

Form of Subordinated Note (FACE OF SECURITY)

EX-4.4 Exhibit 4.4 Form of Subordinated Note (FACE OF SECURITY) [Each Global Security shall bear substantially the following legend: UNLESS AND UNTIL IT IS EXCHANGED IN WHOLE OR IN PART FOR SECURITIES IN DEFINITIVE REGISTERED FORM, THIS SECURITY MAY NOT BE TRANSFERRED EXCEPT AS A WHOLE BY THE DEPOSITARY TO A NOMINEE OF THE DEPOSITARY OR BY A NOMINEE OF THE DEPOSITARY TO THE DEPOSITARY OR ANOTHER N

February 27, 2014 EX-10.46

Page 2 of 8

EX-10.46 Exhibit 10.46 [Idenix Letterhead] September 9, 2013 David Standring 205 Gun Hill Street Milton, MA 02186 Dear David: As we have discussed, your employment with Idenix Pharmaceuticals, Inc. (“Idenix” or the “Company”) will end on September 9, 2013. The Company will provide you with the severance benefits described in paragraph 2 below if you sign and return this letter agreement (the “Agre

February 27, 2014 10-K

Annual Report - 10-K

10-K Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.

February 27, 2014 EX-12

STATEMENT REGARDING COMPUTATION OF RATIO/DEFICIENCY OF EARNINGS TO FIXED CHARGES ( In Thousands) For the Year Ended December 31, 2013 2012 2011 2010 2009 Loss: Loss before income taxes $ (122,370 ) $ (32,489 ) $ (52,040 ) $ (61,595 ) $ (53,168 ) Add:

EX-12 7 d675389dex12.htm EX-12 Exhibit 12 STATEMENT REGARDING COMPUTATION OF RATIO/DEFICIENCY OF EARNINGS TO FIXED CHARGES ( In Thousands) For the Year Ended December 31, 2013 2012 2011 2010 2009 Loss: Loss before income taxes $ (122,370 ) $ (32,489 ) $ (52,040 ) $ (61,595 ) $ (53,168 ) Add: fixed charges 135 76 163 159 146 Total loss $ (122,235 ) $ (32,413 ) $ (51,877 ) $ (61,436 ) $ (53,022 ) Fi

February 27, 2014 EX-99.1

IDENIX PHARMACEUTICALS REPORTS FOURTH QUARTER AND YEAR ENDED 2013 FINANCIAL RESULTS

EX-99.1 Exhibit 99.1 FOR IMMEDIATE RELEASE Idenix Pharmaceuticals Contact: Teri Dahlman (617) 995-9807 IDENIX PHARMACEUTICALS REPORTS FOURTH QUARTER AND YEAR ENDED 2013 FINANCIAL RESULTS CAMBRIDGE, Mass., February 27, 2014 — Idenix Pharmaceuticals, Inc. (NASDAQ: IDIX), a biopharmaceutical company engaged in the discovery and development of drugs for the treatment of human viral diseases, today rep

February 27, 2014 EX-4.1

IDENIX PHARMACEUTICALS, INC. Dated as of SENIOR DEBT SECURITIES CROSS-REFERENCE TABLE(1) Section of Trust Indenture Act of 1939, as amended Section of Indenture 310(a) 6.09 310(b) 6.08 6.10 310(c) Inapplicable 311(a) 6.13 311(b) 6.13 311(c) Inapplica

EX-4.1 Exhibit 4.1 IDENIX PHARMACEUTICALS, INC. and Trustee INDENTURE Dated as of SENIOR DEBT SECURITIES CROSS-REFERENCE TABLE(1) Section of Trust Indenture Act of 1939, as amended Section of Indenture 310(a) 6.09 310(b) 6.08 6.10 310(c) Inapplicable 311(a) 6.13 311(b) 6.13 311(c) Inapplicable 312(a) 4.01 4.04 312(b) 4.04(c) 312(c) 4.04(c) 313(a) 4.03 313(b) 4.03 313(c) 4.03 313(d) 4.03 314(a) 4.0

February 27, 2014 EX-4.3

Form of Senior Note (FACE OF SECURITY)

EX-4.3 Exhibit 4.3 Form of Senior Note (FACE OF SECURITY) [Each Global Security shall bear substantially the following legend: UNLESS AND UNTIL IT IS EXCHANGED IN WHOLE OR IN PART FOR SECURITIES IN DEFINITIVE REGISTERED FORM, THIS SECURITY MAY NOT BE TRANSFERRED EXCEPT AS A WHOLE BY THE DEPOSITARY TO A NOMINEE OF THE DEPOSITARY OR BY A NOMINEE OF THE DEPOSITARY TO THE DEPOSITARY OR ANOTHER NOMINEE

February 27, 2014 EX-21.1

Subsidiaries of the Company Name of Subsidiary State or Other Jurisdiction of Incorporation or Organization Idenix (Massachusetts) Inc. Massachusetts Idenix Securities Corporation Massachusetts Idenix (Cayman) Limited Cayman Islands Idenix SARL** Fra

EX-21.1 Exhibit 21.1 Subsidiaries of the Company Name of Subsidiary State or Other Jurisdiction of Incorporation or Organization Idenix (Massachusetts) Inc. Massachusetts Idenix Securities Corporation Massachusetts Idenix (Cayman) Limited Cayman Islands Idenix SARL** France ** Wholly-owned by Idenix (Cayman) Limited

February 14, 2014 SC 13D/A

IDIX / Idenix Pharmaceuticals Inc / NOVARTIS AG - SC 13D/A Activist Investment

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13D Under the Securities Exchange Act of 1934 (Amendment No. 8)* Idenix Pharmaceuticals, Inc. (Name of Issuer) Common Stock (Title of Class of Securities) 45166R204 (CUSIP Number) Julie Pender Novartis Pharma AG Lichtstrasse 35 CH-4056 Basel, Switzerland +41 61 696 4509 With a copy to: Peter Harwich Allen & Overy LLP

February 14, 2014 8-K

Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers

Form 8-K UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of The Securities Exchange Act of 1934 Date of report (Date of earliest event reported): February 10, 2014 IDENIX PHARMACEUTICALS, INC. (Exact name of registrant as specified in its charter) Delaware 000-49839 45-0478605 (State or other jurisdiction of incorporat

February 11, 2014 SC 13G/A

IDIX / Idenix Pharmaceuticals Inc / PRICE T ROWE ASSOCIATES INC /MD/ - IDIX AS OF 12/31/2013 Passive Investment

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 (Amendment No. 4)* IDENIX PHARMACEUTICALS INC (Name of Issuer) COMMON STOCK (Title of Class of Securities) 45166R204 (CUSIP Number) December 31, 2013 (Date of Event which Requires Filing of Statement) Check the appropriate box to designate the Rule pursuant to which this S

February 4, 2014 SC 13D/A

IDIX / Idenix Pharmaceuticals Inc / BAUPOST GROUP LLC/MA - IDIX13DAMEND1 Activist Investment

SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13D Under the Securities Exchange Act of 1934 (Amendment No. 1) Idenix Pharmaceuticals, Inc. (Name of Issuer) Common Stock (Title Class of Securities) 45166R204 (Cusip Number) Seth A. Klarman The Baupost Group, L.L.C. 10 St. James Avenue, Suite 1700 Boston, Massachusetts 02116 (617) 210-8300 With a copy to: Jeffrey R. Katz, Esq Rop

January 30, 2014 EX-99.1

IDENIX PHARMACEUTICALS ANNOUNCES DECISION BY THE UNITED STATES PATENT AND TRADEMARK OFFICE PATENT TRIAL AND APPEAL BOARD IN THE FIRST PATENT INTERFERNCE

EX-99.1 2 d666307dex991.htm EX-99.1 Exhibit 99.1 FOR IMMEDIATE RELEASE Idenix Pharmaceuticals Contact: Teri Dahlman (617) 995-9807 IDENIX PHARMACEUTICALS ANNOUNCES DECISION BY THE UNITED STATES PATENT AND TRADEMARK OFFICE PATENT TRIAL AND APPEAL BOARD IN THE FIRST PATENT INTERFERNCE CAMBRIDGE, Mass., January 29, 2014 — Idenix Pharmaceuticals, Inc. (Nasdaq:IDIX), a biopharmaceutical company engaged

January 30, 2014 8-K

Financial Statements and Exhibits, Other Events

8-K 1 d666307d8k.htm FORM 8-K UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): January 29, 2014 Idenix Pharmaceuticals, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 000-49839 45-0478605 (State or Other Juris- dic

January 28, 2014 EX-99.1

IDENIX TO RAISE $106.7 MILLION THROUGH REGISTERED DIRECT OFFERING

EX-99.1 5 d665213dex991.htm EX-99.1 Exhibit 99.1 FOR IMMEDIATE RELEASE Idenix Pharmaceuticals Contact: Teri Dahlman (617) 995-9807 IDENIX TO RAISE $106.7 MILLION THROUGH REGISTERED DIRECT OFFERING CAMBRIDGE, Mass., Jan. 28, 2014 – Idenix Pharmaceuticals, Inc. (Nasdaq: IDIX), a biopharmaceutical company engaged in the discovery and development of drugs for the treatment of human viral diseases, tod

January 28, 2014 424B5

16,420,241 shares Common Stock

424B5 Prospectus Supplement Table of Contents Filed Pursuant to Rule 424(b)(5) Registration File No.

January 28, 2014 EX-10.2

Baupost Capital, L.L.C. 10 St. James Avenue, Suite 1700 Boston, MA 0211 January 27, 2014

EX-10.2 4 d665213dex102.htm EX-10.2 Exhibit 10.2 Baupost Capital, L.L.C. 10 St. James Avenue, Suite 1700 Boston, MA 0211 January 27, 2014 Idenix Pharmaceuticals, Inc. 320 Bent Street Cambridge, MA 02141 Attn: Ronald C. Renaud, Jr. Dear Mr. Renaud: Reference is made to that certain Subscription Agreement, dated as of January 27, 2014, by and between Idenix Pharmaceuticals, Inc., a Delaware corporat

January 28, 2014 8-K

Entry into a Material Definitive Agreement, Financial Statements and Exhibits, Other Events

8-K 1 d665213d8k.htm FORM 8-K UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): January 27, 2014 Idenix Pharmaceuticals, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 000-49839 45-0478605 (State or Other Jurisdicti

January 28, 2014 EX-10.1

[SIGNATURE PAGE TO SUBSCRIPTION AGREEMENT]

EX-10.1 3 d665213dex101.htm EX-10.1 Exhibit 10.1 January 27, 2014 Idenix Pharmaceuticals, Inc. 320 Bent Street Cambridge, Massachusetts 02141-2025 Ladies and Gentlemen: Each of the undersigned (each, an “Investor” and collectively, the “Investors”) hereby confirms and agrees, severally and not jointly, with you as follows: 1. This Purchase Agreement (together with the attached schedule and annexes

January 27, 2014 S-3MEF

- S-3MEF

S-3MEF 1 d667224ds3mef.htm S-3MEF As filed with the Securities and Exchange Commission on January 27, 2014 Registration No. 333- UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM S-3 REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933 IDENIX PHARMACEUTICALS, INC. (Exact name of registrant as specified in its charter) Delaware 45-0478605 (State or other jurisdiction o

January 13, 2014 EX-99.1

Idenix Pharmaceuticals Reports Sustained Virologic Response Rate (SVR4) for Phase II All-Oral Combination Study of Samatasvir (IDX719), a Potent, Pan-Genotypic HCV NS5A Inhibitor, and Simeprevir

EX-99.1 Exhibit 99.1 FOR IMMEDIATE RELEASE Idenix Pharmaceuticals Contact: Teri Dahlman, (617) 995-9807 Idenix Pharmaceuticals Reports Sustained Virologic Response Rate (SVR4) for Phase II All-Oral Combination Study of Samatasvir (IDX719), a Potent, Pan-Genotypic HCV NS5A Inhibitor, and Simeprevir CAMBRIDGE, Mass., Jan. 13, 2014 — Idenix Pharmaceuticals, Inc. (Nasdaq:IDIX), a biopharmaceutical com

January 13, 2014 8-K

Financial Statements and Exhibits, Other Events - FORM 8-K

FORM 8-K UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): January 13, 2014 Idenix Pharmaceuticals, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 000-49839 45-0478605 (State or Other Jurisdiction of Incorporation (

January 6, 2014 EX-10.1

[IDENIX LETTERHEAD]

EX-10.1 Exhibit 10.1 [IDENIX LETTERHEAD] December 30, 2013 CONFIDENTIAL Jacques Dumas 32 Suffolk Lane Carlisle, MA 01741 Dear Jacques: This employment letter (the “letter”) is made by and between Idenix Pharmaceuticals, Inc., a corporation incorporated under the laws of the State of Delaware (together with its successors and assigns, the “Company”), and you (and, together with the Company, the “Pa

January 6, 2014 8-K

Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers, Entry into a Material Definitive Agreement, Financial Statements and Exhibits

8-K 1 d654685d8k.htm FORM 8-K UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of The Securities Exchange Act of 1934 Date of report (Date of earliest event reported): December 30, 2013 IDENIX PHARMACEUTICALS, INC. (Exact name of registrant as specified in its charter) Delaware 000-49839 45-0478605 (State or other juris

December 9, 2013 EX-99.1

IDENIX PHARMACEUTICALS ANNOUNCES DECLARATION OF SENIOR PARTY IN A SECOND PATENT INTERFERENCE BY THE USPTO

EX-99.1 Exhibit 99.1 FOR IMMEDIATE RELEASE Idenix Pharmaceuticals Contact: Teri Dahlman (617) 995-9807 IDENIX PHARMACEUTICALS ANNOUNCES DECLARATION OF SENIOR PARTY IN A SECOND PATENT INTERFERENCE BY THE USPTO CAMBRIDGE, Mass., December 9, 2013 — Idenix Pharmaceuticals, Inc. (NASDAQ: IDIX), a biopharmaceutical company engaged in the discovery and development of drugs for the treatment of human vira

December 9, 2013 8-K

Financial Statements and Exhibits, Other Events

8-K 1 d639723d8k.htm FORM 8-K UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): December 9, 2013 Idenix Pharmaceuticals, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 000-49839 45-0478605 (State or Other Juris- dic

December 2, 2013 EX-99.1

IDENIX PHARMACEUTICALS FILES PATENT INFRINGEMENT AND INTERFERENCE LAWSUITS AGAINST GILEAD SCIENCES

EX-99.1 Exhibit 99.1 FOR IMMEDIATE RELEASE Idenix Pharmaceuticals Contact: Teri Dahlman, [email protected] IDENIX PHARMACEUTICALS FILES PATENT INFRINGEMENT AND INTERFERENCE LAWSUITS AGAINST GILEAD SCIENCES CAMBRIDGE, Mass., December 2, 2013 — Idenix Pharmaceuticals, Inc. (NASDAQ: IDIX), a biopharmaceutical company engaged in the discovery and development of drugs for the treatment of human

December 2, 2013 8-K

Financial Statements and Exhibits, Other Events - 8-K

8-K UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): December 2, 2013 Idenix Pharmaceuticals, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 000-49839 45-0478605 (State or Other Jurisdiction of Incorporation (Commi

November 1, 2013 SC 13D

IDIX / Idenix Pharmaceuticals Inc / BAUPOST GROUP LLC/MA - IDIX13DORIG Activist Investment

SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13D Under the Securities Exchange Act of 1934 Idenix Pharmaceuticals, Inc. (Name of Issuer) Common Stock (Title Class of Securities) 45166R204 (Cusip Number) Seth A. Klarman The Baupost Group, L.L.C. 10 St. James Avenue, Suite 1700 Boston, Massachusetts 02116 (617) 210-8300 With a copy to: Gregory D. Sheehan, Esq Ropes and Gray LLP

October 30, 2013 EX-99.1

IDENIX PHARMACEUTICALS REPORTS THIRD QUARTER AND NINE MONTH 2013 FINANCIAL RESULTS AND PROVIDES HCV PIPELINE UPDATE

EX-99.1 Exhibit 99.1 FOR IMMEDIATE RELEASE Idenix Pharmaceuticals Contact: Teri Dahlman (617) 995-9807 IDENIX PHARMACEUTICALS REPORTS THIRD QUARTER AND NINE MONTH 2013 FINANCIAL RESULTS AND PROVIDES HCV PIPELINE UPDATE • Enrollment initiated for a phase I/II clinical trial for IDX21437, a next-generation uridine nucleotide prodrug inhibitor for the treatment of hepatitis C virus infection (HCV) •

October 30, 2013 8-K

Financial Statements and Exhibits, Results of Operations and Financial Condition

8-K 1 d621388d8k.htm FORM 8-K UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): October 30, 2013 Idenix Pharmaceuticals, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 000-49839 45-0478605 (State or Other Jurisdicti

October 30, 2013 10-Q

Quarterly Report - FORM 10-Q

Form 10-Q Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.

October 30, 2013 EX-10.1

SECOND AMENDMENT TO LEASE

EX-10.1 Exhibit 10.1 SECOND AMENDMENT TO LEASE THIS SECOND AMENDMENT TO LEASE (this “Second Amendment”) is entered into as of this 3rd day of September, 2013, by and between BMR-ROGERS STREET LLC, a Delaware limited liability company (“Landlord”), and IDENIX PHARMACEUTICALS, INC., a Delaware corporation (“Tenant”). RECITALS A. WHEREAS, Landlord and Tenant entered into that certain Lease dated as o

September 10, 2013 8-K

Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers, Costs Associated with Exit or Disposal Activities, Other Events

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of The Securities Exchange Act of 1934 Date of report (Date of earliest event reported): September 9, 2013 IDENIX PHARMACEUTICALS, INC. (Exact name of registrant as specified in its charter) Delaware 000-49839 45-0478605 (State or other jurisdiction of incorporation or or

August 7, 2013 8-K

Financial Statements and Exhibits, Results of Operations and Financial Condition - FORM 8-K

Form 8-K UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): August 7, 2013 Idenix Pharmaceuticals, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 000-49839 45-0478605 (State or Other Jurisdiction of Incorporation (Co

August 7, 2013 10-Q

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q (Mark One) x QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the Quarterly Period Ended June 30, 2013 Or ? TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number 000

August 7, 2013 EX-99.1

IDENIX PHARMACEUTICALS REPORTS SECOND QUARTER AND SIX MONTH 2013 FINANCIAL RESULTS

EX-99.1 Exhibit 99.1 FOR IMMEDIATE RELEASE Idenix Pharmaceuticals Contact: Teri Dahlman (617) 995-9807 IDENIX PHARMACEUTICALS REPORTS SECOND QUARTER AND SIX MONTH 2013 FINANCIAL RESULTS CAMBRIDGE, Mass., August 7, 2013 — Idenix Pharmaceuticals, Inc. (NASDAQ: IDIX), a biopharmaceutical company engaged in the discovery and development of drugs for the treatment of human viral diseases, today reporte

August 7, 2013 EX-10.2

FIRST AMENDMENT to CLINICAL TRIAL COLLABORATION AGREEMENT between Idenix Pharmaceuticals, Inc. and Janssen Pharmaceuticals, Inc.,

EX-10.2 3 d558252dex102.htm EX-10.2 Exhibit 10.2 CONFIDENTIAL FIRST AMENDMENT to CLINICAL TRIAL COLLABORATION AGREEMENT between Idenix Pharmaceuticals, Inc. and Janssen Pharmaceuticals, Inc., This first Amendment (the “First Amendment”) to the Clinical Trial Collaboration Agreement (as defined below) shall be effective as of the last of the last signature affixed hereto (“First Amendment Effective

August 7, 2013 EX-10.1

FIRST AMENDMENT TO LEASE

EX-10.1 2 d558252dex101.htm EX-10.1 Exhibit 10.1 FIRST AMENDMENT TO LEASE THIS FIRST AMENDMENT TO LEASE (this “Amendment”) is entered into as of this 1st day of May, 2013, by and between BMR-ROGERS STREET LLC, a Delaware limited liability company (“Landlord”), and IDENIX PHARMACEUTICALS, INC., a Delaware corporation (“Tenant”). RECITALS A. WHEREAS, Landlord and Tenant entered into that certain Lea

June 10, 2013 EX-99.1

IDENIX PHARMACEUTICALS APPOINTS CHARLES ROWLAND TO ITS BOARD OF DIRECTORS

Exhibit 99.1 FOR IMMEDIATE RELEASE Idenix Pharmaceuticals Contact: Teri Dahlman, (617) 995-9807 IDENIX PHARMACEUTICALS APPOINTS CHARLES ROWLAND TO ITS BOARD OF DIRECTORS CAMBRIDGE, Mass., June 10, 2013 — Idenix Pharmaceuticals, Inc. (NASDAQ: IDIX), a biopharmaceutical company engaged in the discovery and development of drugs for the treatment of human viral diseases, today announced that it has ap

June 10, 2013 8-K

Submission of Matters to a Vote of Security Holders - FORM 8-K

Form 8-K UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of The Securities Exchange Act of 1934 Date of report (Date of earliest event reported): June 6, 2013 IDENIX PHARMACEUTICALS, INC. (Exact name of registrant as specified in its charter) Delaware 000-49839 45-0478605 (State or other jurisdiction of incorporation o

June 10, 2013 8-K

Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers, Financial Statements and Exhibits - FORM 8-K

Form 8-K UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of The Securities Exchange Act of 1934 Date of report (Date of earliest event reported): June 6, 2013 IDENIX PHARMACEUTICALS, INC. (Exact name of registrant as specified in its charter) Delaware 000-49839 45-0478605 (State or other jurisdiction of incorporation o

April 30, 2013 8-K

Financial Statements and Exhibits, Results of Operations and Financial Condition

Form 8-K UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): April 30, 2013 Idenix Pharmaceuticals, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 000-49839 45-0478605 (State or Other Jurisdiction of Incorporation (Co

April 30, 2013 EX-99.1

IDENIX PHARMACEUTICALS REPORTS FIRST QUARTER 2013 FINANCIAL RESULTS

Exhibit 99.1 FOR IMMEDIATE RELEASE Idenix Pharmaceuticals Contact: Teri Dahlman (617) 995-9807 IDENIX PHARMACEUTICALS REPORTS FIRST QUARTER 2013 FINANCIAL RESULTS CAMBRIDGE, Mass., April 30, 2013 — Idenix Pharmaceuticals, Inc. (NASDAQ: IDIX), a biopharmaceutical company engaged in the discovery and development of drugs for the treatment of human viral diseases, today reported unaudited financial r

April 30, 2013 EX-21.1

Subsidiaries of the Company Name of Subsidiary State or Other Jurisdiction of Incorporation or Organization Idenix (Massachusetts) Inc. Massachusetts Idenix Securities Corporation Massachusetts Idenix (Cayman) Limited Cayman Islands Idenix SARL** Fra

Exhibit 21.1 Subsidiaries of the Company Name of Subsidiary State or Other Jurisdiction of Incorporation or Organization Idenix (Massachusetts) Inc. Massachusetts Idenix Securities Corporation Massachusetts Idenix (Cayman) Limited Cayman Islands Idenix SARL** France ** Wholly-owned by Idenix (Cayman) Limited

April 30, 2013 10-Q

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q (Mark One) x QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the Quarterly Period Ended March 31, 2013 Or ? TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number 00

April 26, 2013 DEF 14A

- DEFINITIVE PROXY STATEMENT

Definitive Proxy Statement Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.

March 25, 2013 8-K

Financial Statements and Exhibits, Other Events - FORM 8-K

Form 8-K UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): March 22, 2013 Idenix Pharmaceuticals, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 000-49839 45-0478605 (State or Other Jurisdiction of Incorporation (Co

March 25, 2013 EX-99.1

IDENIX PHARMACEUTICALS ANNOUNCES DECISION BY THE UNITED STATES PATENT AND TRADEMARK OFFICE PATENT TRIAL AND APPEAL BOARD IN THE FIRST PHASE OF THE INTERFERENCE

EX-99.1 Exhibit 99.1 FOR IMMEDIATE RELEASE Idenix Pharmaceuticals Contacts: Kelly Barry (617) 995-9033 (media) Teri Dahlman (617) 995-9807 (investors) IDENIX PHARMACEUTICALS ANNOUNCES DECISION BY THE UNITED STATES PATENT AND TRADEMARK OFFICE PATENT TRIAL AND APPEAL BOARD IN THE FIRST PHASE OF THE INTERFERENCE CAMBRIDGE, Mass., March 22, 2013 — Idenix Pharmaceuticals, Inc. (NASDAQ: IDIX), a biophar

February 26, 2013 8-K

Financial Statements and Exhibits, Results of Operations and Financial Condition - FORM 8-K

FORM 8-K UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act Date of Report (Date of earliest event reported): February 25, 2013 Idenix Pharmaceuticals, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 000-49839 45-0478605 (State or Other Jurisdiction of Incorporation (Commiss

February 26, 2013 EX-99.1

IDENIX PHARMACEUTICALS REPORTS FOURTH QUARTER AND YEAR ENDED 2012 FINANCIAL RESULTS

EX-99.1 Exhibit 99.1 FOR IMMEDIATE RELEASE Idenix Pharmaceuticals Contacts: Kelly Barry (617) 995-9033 (media) Teri Dahlman (617) 995-9807 (investors) IDENIX PHARMACEUTICALS REPORTS FOURTH QUARTER AND YEAR ENDED 2012 FINANCIAL RESULTS CAMBRIDGE, Mass., February 25, 2013 — Idenix Pharmaceuticals, Inc. (NASDAQ: IDIX), a biopharmaceutical company engaged in the discovery and development of drugs for

February 26, 2013 8-K

Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers - FORM 8-K

FORM 8-K UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of The Securities Exchange Act of 1934 Date of report (Date of earliest event reported): February 20, 2013 IDENIX PHARMACEUTICALS, INC. (Exact name of registrant as specified in its charter) Delaware 000-49839 45-0478605 (State or other jurisdiction of incorporat

February 25, 2013 EX-21.1

Subsidiaries of the Company Name of Subsidiary State or Other Jurisdiction of Incorporation or Organization Idenix (Massachusetts) Inc. Massachusetts Idenix Massachusetts Securities Corporation Massachusetts Idenix (Cayman) Limited Cayman Islands Ide

Exhibit 21.1 Subsidiaries of the Company Name of Subsidiary State or Other Jurisdiction of Incorporation or Organization Idenix (Massachusetts) Inc. Massachusetts Idenix Massachusetts Securities Corporation Massachusetts Idenix (Cayman) Limited Cayman Islands Idenix SARL** France ** Wholly-owned by Idenix (Cayman) Limited

February 25, 2013 10-K

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 Form 10-K

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 Form 10-K (Mark One) x ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31, 2012 or ? TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number 000-498

February 25, 2013 EX-10.24

Confidential Materials omitted and filed separately with the Securities and Exchange Commission. Asterisks denote omissions. CLINICAL TRIAL COLLABORATION AGREEMENT

Exhibit 10.24 Confidential Materials omitted and filed separately with the Securities and Exchange Commission. Asterisks denote omissions. CLINICAL TRIAL COLLABORATION AGREEMENT This CLINICAL TRIAL COLLABORATION AGREEMENT (the ?Agreement?) is made and entered into as of the date of the last signature affixed hereto (the ?Effective Date?) by and between Idenix Pharmaceuticals, Inc., a Delaware corp

February 14, 2013 SC 13G/A

IDIX / Idenix Pharmaceuticals Inc / Brookside Capital Trading Fund, L.P. - SC 13G/A Passive Investment

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G (Rule 13d-102) Information Statement Pursuant to Rules 13d-1 and 13d-2 Under the Securities Exchange Act of 1934 (Amendment No. 3)* Idenix Pharmaceuticals, Inc. (Name of Issuer) Common Stock, par value $0.001 (Title of Class of Securities) 45166R204 (CUSIP Number) December 31, 2012 (Date of Event Which Requires Fi

February 11, 2013 SC 13G/A

IDIX / Idenix Pharmaceuticals Inc / PRICE T ROWE ASSOCIATES INC /MD/ - IDIX AS OF 12/31/2012 Passive Investment

SC 13G/A 1 idix13gadec12.htm IDIX AS OF 12/31/2012 UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 (Amendment No. 3)* IDENIX PHARMACEUTICALS INC (Name of Issuer) COMMON STOCK (Title of Class of Securities) 45166R204 (CUSIP Number) December 31, 2012 (Date of Event which Requires Filing of Statement) Check the appropriate

February 8, 2013 SC 13G/A

IDIX / Idenix Pharmaceuticals Inc / BAUPOST GROUP LLC/MA - IDIX13GAMEND2 Passive Investment

CUSIP NO. 45166R204 13G PAGE 1 OF 11 SECURITIES AND EXCHANGE COMMISSION Washington, DC 20549 SCHEDULE 13G (Rule 13d-102) INFORMATION TO BE INCLUDED IN STATEMENTS FILED PURSUANT TO RULES 13d-1(b)(c), AND (d) AND AMENDMENTS THERETO FILED PURSUANT TO RULE 13d-2(b) (Amendment No. 2)* Idenix Pharmaceuticals, Inc. (Name of Issuer) Common Stock (Title of Class of Securities) 45166R204 (CUSIP Number) Janu

February 5, 2013 EX-99.1

IDENIX PHARMACEUTICALS PROVIDES UPDATE ON IDX184 AND IDX19368 DEVELOPMENT PROGRAMS - Management to host a conference call and webcast today at 4:30 pm ET -

EX-99.1 Exhibit 99.1 FOR IMMEDIATE RELEASE Idenix Pharmaceuticals Contacts: Teri Dahlman (617) 995-9807 or [email protected] IDENIX PHARMACEUTICALS PROVIDES UPDATE ON IDX184 AND IDX19368 DEVELOPMENT PROGRAMS - Management to host a conference call and webcast today at 4:30 pm ET - CAMBRIDGE, Mass., February 4, 2013 — Idenix Pharmaceuticals, Inc. (NASDAQ: IDIX), a biopharmaceutical company e

February 5, 2013 8-K

Financial Statements and Exhibits, Other Events - FORM 8-K

Form 8-K UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): February 4, 2013 Idenix Pharmaceuticals, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 000-49839 45-0478605 (State or Other Jurisdiction of Incorporation (

January 28, 2013 8-K

Entry into a Material Definitive Agreement - FORM 8-K

Form 8-K UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of The Securities Exchange Act of 1934 Date of report (Date of earliest event reported): January 25, 2013 IDENIX PHARMACEUTICALS, INC. (Exact name of registrant as specified in its charter) Delaware 000-49839 45-0478605 (State or other jurisdiction of incorporati

January 9, 2013 8-K

Other Events - FORM 8-K

Form 8-K UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): January 7, 2013 Idenix Pharmaceuticals, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 000-49839 45-0478605 (State or Other Jurisdiction of Incorporation (C

December 26, 2012 8-K

Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers - FORM 8-K

Form 8-K UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of The Securities Exchange Act of 1934 Date of report (Date of earliest event reported): December 19, 2012 IDENIX PHARMACEUTICALS, INC. (Exact name of registrant as specified in its charter) Delaware 000-49839 45-0478605 (State or other jurisdiction of incorporat

November 9, 2012 SC 13G/A

IDIX / Idenix Pharmaceuticals Inc / BAUPOST GROUP LLC/MA - IDIX13GAMEND1 Passive Investment

CUSIP NO. 45166R204 13G PAGE 1 OF 10 SECURITIES AND EXCHANGE COMMISSION Washington, DC 20549 SCHEDULE 13G (Rule 13d-102) INFORMATION TO BE INCLUDED IN STATEMENTS FILED PURSUANT TO RULES 13d-1(b)(c), AND (d) AND AMENDMENTS THERETO FILED PURSUANT TO RULE 13d-2(b) (Amendment No. 1) Idenix Pharmaceuticals, Inc. (Name of Issuer) Common Stock (Title of Class of Securities) 45166R204 (CUSIP Number) Octob

November 1, 2012 EX-99.1

IDENIX PHARMACEUTICALS REPORTS THIRD QUARTER AND NINE MONTH 2012 FINANCIAL RESULTS AND HCV PROGRAM UPDATE

EX-99.1 Exhibit 99.1 FOR IMMEDIATE RELEASE Idenix Pharmaceuticals Contacts: Kelly Barry (617) 995-9033 (media) Teri Dahlman (617) 995-9807 (investors) IDENIX PHARMACEUTICALS REPORTS THIRD QUARTER AND NINE MONTH 2012 FINANCIAL RESULTS AND HCV PROGRAM UPDATE CAMBRIDGE, Mass., November 1, 2012 - Idenix Pharmaceuticals, Inc. (NASDAQ: IDIX), a biopharmaceutical company engaged in the discovery and deve

November 1, 2012 8-K

Financial Statements and Exhibits, Results of Operations and Financial Condition - FORM 8-K

FORM 8-K UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): November 1, 2012 Idenix Pharmaceuticals, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 000-49839 45-0478605 (State or Other Jurisdiction of Incorporation (

November 1, 2012 10-Q

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q (Mark One) ? QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the Quarterly Period Ended September 30, 2012 Or ? TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file numbe

November 1, 2012 EX-21.1

Subsidiaries of the Company Name of Subsidiary State or Other Jurisdiction of Incorporation or Organization Idenix (Massachusetts) Inc. Massachusetts Idenix Massachusetts Securities Corporation Massachusetts Idenix (Cayman) Limited Cayman Islands Ide

EX-21.1 Exhibit 21.1 Subsidiaries of the Company Name of Subsidiary State or Other Jurisdiction of Incorporation or Organization Idenix (Massachusetts) Inc. Massachusetts Idenix Massachusetts Securities Corporation Massachusetts Idenix (Cayman) Limited Cayman Islands Idenix SARL** France ** Wholly-owned by Idenix (Cayman) Limited 56

September 28, 2012 8-K

Entry into a Material Definitive Agreement, Termination of a Material Definitive Agreement, Financial Statements and Exhibits

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of The Securities Exchange Act of 1934 Date of report (Date of earliest event reported): September 25, 2012 IDENIX PHARMACEUTICALS, INC. (Exact name of registrant as specified in its charter) Delaware 000-49839 45-0478605 (State or other jurisdiction of incorporation or o

September 28, 2012 EX-10.2

LEASE TERMINATION AGREEMENT

Termination Agreement Exhibit 10.2 LEASE TERMINATION AGREEMENT THIS LEASE TERMINATION AGREEMENT (this “Agreement”) is entered into as of this 25th day of September, 2012 (the “Execution Date”), by and between BMR-HAMPSHIRE LLC, a Delaware limited liability company (“Landlord,” as successor-in-interest to Metropolitan Life Insurance Company (“Prior Landlord”), as successor-in-interest to BHX, LLC,

September 28, 2012 EX-10.1

LEASE by and between BMR-ROGERS STREET LLC, a Delaware limited liability company IDENIX PHARMACEUTICALS, INC., a Delaware corporation

Lease Agreement Exhibit 10.1 LEASE by and between BMR-ROGERS STREET LLC, a Delaware limited liability company and IDENIX PHARMACEUTICALS, INC., a Delaware corporation LEASE THIS LEASE (this “Lease”) is entered into as of this 25th day of September, 2012 (the “Execution Date”), by and between BMR-ROGERS STREET LLC, a Delaware limited liability company (“Landlord”), and IDENIX PHARMACEUTICALS, INC.,

September 20, 2012 EX-99.1

EX-99.1

EX-99.1 Exhibit 99.1 1 Investor Presentation September 20, 2012 2 Building a Leading Antiviral Franchise Safe Harbor Statement This presentation includes forward-looking statements about Idenix and its business, including without limitation, statements regarding drug discovery, research and clinical development, regulatory approval processes and market opportunities. These forward- looking stateme

September 20, 2012 8-K

Regulation FD Disclosure, Financial Statements and Exhibits - FORM 8-K

Form 8-K UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): September 20, 2012 Idenix Pharmaceuticals, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 000-49839 45-0478605 (State or Other Juris-diction of Incorporatio

September 19, 2012 8-K

Amendments to Articles of Incorporation or Bylaws; Change in Fiscal Year, Financial Statements and Exhibits - FORM 8-K

Form 8-K UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): September 13, 2012 Idenix Pharmaceuticals, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 000-49839 45-0478605 (State or Other Jurisdiction of Incorporation

September 19, 2012 EX-3.1

SECOND AMENDED AND RESTATED BY-LAWS IDENIX PHARMACEUTICALS, INC. TABLE OF CONTENTS Page ARTICLE I STOCKHOLDERS 1.1 Place of Meetings 1 1.2 Annual Meeting 1 1.3 Special Meetings 1 1.4 Notice of Meetings 1 1.5 Voting List 2 1.6 Quorum 2 1.7 Adjournment

EX-3.1 Exhibit 3.1 SECOND AMENDED AND RESTATED BY-LAWS OF IDENIX PHARMACEUTICALS, INC. TABLE OF CONTENTS Page ARTICLE I STOCKHOLDERS 1.1 Place of Meetings 1 1.2 Annual Meeting 1 1.3 Special Meetings 1 1.4 Notice of Meetings 1 1.5 Voting List 2 1.6 Quorum 2 1.7 Adjournments 3 1.8 Voting and Proxies 3 1.9 Action at Meeting 3 1.10 Nomination of Directors. 4 1.11 Notice of Business at Annual Meetings.

August 27, 2012 8-K

Financial Statements and Exhibits, Other Events

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): August 27, 2012 Idenix Pharmaceuticals, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 000-49839 45-0478605 (State or Other Jurisdiction of Incorporation (Commission

August 27, 2012 EX-99.1

IDENIX PROVIDES UPDATE ON IDX19368 DEVELOPMENT PROGRAM - IDX19368, for which Idenix has submitted an IND application, has been placed on clinical hold by FDA –

Exhibit 99.1 FOR IMMEDIATE RELEASE Idenix Pharmaceuticals Contacts: Kelly Barry (617) 995-9033 (media) Daniella Beckman (617) 224-4471 (investors) IDENIX PROVIDES UPDATE ON IDX19368 DEVELOPMENT PROGRAM - IDX19368, for which Idenix has submitted an IND application, has been placed on clinical hold by FDA – CAMBRIDGE, Mass., August 27, 2012 — Idenix Pharmaceuticals, Inc. (NASDAQ: IDIX), a biopharmac

August 17, 2012 EX-99.1

IDENIX PROVIDES UPDATE ON IDX184 CLINICAL DEVELOPMENT PROGRAM - IDX184 has been placed on partial clinical hold by FDA – Management to host a conference call webcast today at 8:30 am ET

EX-99.1 Exhibit 99.1 FOR IMMEDIATE RELEASE Idenix Pharmaceuticals Contacts: Kelly Barry (617) 995-9033 (media) Daniella Beckman (617) 224-4471 (investors) IDENIX PROVIDES UPDATE ON IDX184 CLINICAL DEVELOPMENT PROGRAM - IDX184 has been placed on partial clinical hold by FDA – Management to host a conference call webcast today at 8:30 am ET CAMBRIDGE, Mass., August 16, 2012 — Idenix Pharmaceuticals,

August 17, 2012 8-K

Financial Statements and Exhibits, Other Events

Form 8-K UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): August 16, 2012 Idenix Pharmaceuticals, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 000-49839 45-0478605 (State or Other Jurisdiction of Incorporation (C

August 10, 2012 EX-4

August 8, 2012

Exhibit 4 Novartis Novartis AG Lichtstrasse 35 CH 4056 Basel August 8, 2012 The undersigned hereby certifies that Dr. Martin Henrich and Knut Mager are authorized to execute Amendment No. 7 to Schedule 13D with respect to Idenix Pharmaceuticals, Inc., on behalf of Novartis AG. /s/ Peter Rupprecht Name: Peter Rupprecht Title: Senior Corporate Counsel

August 10, 2012 EX-2

Confidential Materials omitted and filed separately with the Securities and Exchange Commission. Asterisks denote omissions. TERMINATION AND REVISED RELATIONSHIP AGREEMENT

EX-2 2 a12-177991ex2.htm EX-2 Exhibit 2 EXECUTION VERSION Confidential Materials omitted and filed separately with the Securities and Exchange Commission. Asterisks denote omissions. TERMINATION AND REVISED RELATIONSHIP AGREEMENT This Termination and Revised Relationship Agreement (this “Agreement”), effective as of July 31, 2012 (the “Effective Date”), is made by and among Idenix Pharmaceuticals,

August 10, 2012 EX-3

LOCK-UP AGREEMENT

EX-3 3 a12-177991ex3.htm EX-3 Exhibit 3 LOCK-UP AGREEMENT July 31, 2012 J. P. MORGAN SECURITIES LLC As Representative of the several Underwriters listed in Schedule 1 to the Underwriting Agreement referred to below c/o J. P. Morgan Securities LLC 383 Madison Avenue New York, NY 10179 Re: Idenix Pharmaceuticals, Inc. — Public Offering Ladies and Gentlemen: The undersigned understands that you, as R

August 10, 2012 SC 13D/A

IDIX / Idenix Pharmaceuticals Inc / NOVARTIS AG - SC 13D/A Activist Investment

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13D/A Under the Securities Exchange Act of 1934 (Amendment No. 7)* Idenix Pharmaceuticals, Inc. (Name of Issuer) Common Stock (Title of Class of Securities) 45166R 20 4 (CUSIP Number) Thomas Lynch, Esq. Adam H. Golden, Esq. Novartis Pharma AG Kaye Scholer LLP Lichtstrasse 35 425 Park Avenue CH-4056 Basel, Switzerland

August 8, 2012 EX-10.2

Idenix Pharmaceuticals, Inc. Incentive Stock Option Agreement Granted Under 2012 Stock Incentive Plan

Exhibit 10.2 Idenix Pharmaceuticals, Inc. Incentive Stock Option Agreement Granted Under 2012 Stock Incentive Plan 1. Grant of Option. This agreement evidences the grant by Idenix Pharmaceuticals, Inc., a Delaware corporation (the ?Company?), on , 2012 (the ?Grant Date?) to [ ] (the ?Participant?), of an option to purchase, in whole or in part, on the terms provided herein and in the Company?s 201

August 8, 2012 10-Q

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q (Mark One) x QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the Quarterly Period Ended June 30, 2012 Or ¨ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number 000

August 8, 2012 EX-10.3

Idenix Pharmaceuticals, Inc. Nonstatutory Stock Option Agreement Granted Under 2012 Stock Incentive Plan

Exhibit 10.3 Idenix Pharmaceuticals, Inc. Nonstatutory Stock Option Agreement Granted Under 2012 Stock Incentive Plan 1. Grant of Option. This agreement evidences the grant by Idenix Pharmaceuticals, Inc., a Delaware corporation (the ?Company?), on , 2012 (the ?Grant Date?) to [ ], an [employee], [consultant], [director] of the Company (the ?Participant?), of an option to purchase, in whole or in

August 8, 2012 EX-10.1

IDENIX PHARMACEUTICALS, INC. 2012 STOCK INCENTIVE PLAN

Exhibit 10.1 IDENIX PHARMACEUTICALS, INC. 2012 STOCK INCENTIVE PLAN 1. Purpose The purpose of this 2012 Stock Incentive Plan (the ?Plan?) of Idenix Pharmaceuticals, Inc. a Delaware corporation (the ?Company?), is to advance the interests of the Company?s stockholders by enhancing the Company?s ability to attract, retain and motivate persons who are expected to make important contributions to the C

August 8, 2012 EX-10.4

TERMINATION AND REVISED RELATIONSHIP AGREEMENT

Exhibit 10.4 EXECUTION VERSION Confidential materials omitted and filed separately with the Securities and Exchange commission. Asterisks denote omissions. TERMINATION AND REVISED RELATIONSHIP AGREEMENT This Termination and Revised Relationship Agreement (this ?Agreement?), effective as of July 31, 2012 (the ?Effective Date?), is made by and among Idenix Pharmaceuticals, Inc., with offices at 60 H

August 3, 2012 EX-99.1

Idenix Pharmaceuticals Prices Public Offering of Common Stock

Exhibit 99.1 FOR IMMEDIATE RELEASE Idenix Pharmaceuticals Contacts: Kelly Barry (617) 995-9033 (media) Daniella Beckman (617) 224-4471 (investors) Idenix Pharmaceuticals Prices Public Offering of Common Stock CAMBRIDGE, Mass., August 2, 2012—Idenix Pharmaceuticals, Inc. (NASDAQ: IDIX), a biopharmaceutical company engaged in the discovery and development of drugs for the treatment of human viral di

August 3, 2012 8-K

Entry into a Material Definitive Agreement, Financial Statements and Exhibits, Other Events - FORM 8-K

Form 8-K UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of The Securities Exchange Act of 1934 Date of report (Date of earliest event reported): August 2, 2012 IDENIX PHARMACEUTICALS, INC. (Exact name of registrant as specified in its charter) Delaware 000-49839 45-0478605 (State or other jurisdiction of incorporation

August 3, 2012 EX-1.1

IDENIX PHARMACEUTICALS, INC. 22,000,000 Shares of Common Stock Underwriting Agreement

Underwriting Agreement Exhibit 1.1 Execution Version IDENIX PHARMACEUTICALS, INC. 22,000,000 Shares of Common Stock Underwriting Agreement August 2, 2012 J. P. Morgan Securities LLC As Representative of the several Underwriters listed in Schedule 1 hereto c/o J. P. Morgan Securities LLC 383 Madison Avenue New York, New York 10179 Ladies and Gentlemen: Idenix Pharmaceuticals, Inc., a Delaware corpo

August 2, 2012 424B5

CALCULATION OF REGISTRATION FEE Title of each class of securities to be registered Amount to be registered(1) Proposed maximum offering price per unit Proposed maximum aggregate offering price(1) Amount of registration fee(2) Common Stock; $.001 par

424B5 Table of Contents Filed Pursuant to Rule 424(b)(5) Registration File No. 333-182953 CALCULATION OF REGISTRATION FEE Title of each class of securities to be registered Amount to be registered(1) Proposed maximum offering price per unit Proposed maximum aggregate offering price(1) Amount of registration fee(2) Common Stock; $.001 par value 25,300,000 $ 8.00 $ 202,400,000 $ 23,195 (1) Assumes e

July 31, 2012 EX-99.1

EX-99.1

Exhibit 99.1 Changes to Collaboration with Novartis July 2012 Description 2003 Original Agreement Terms 2012 Termination & Revised Relationship Agreement Terms Pipeline Rights NVS had exclusive WW option to license all clinical products in IDIX pipeline if maintained above 30% ownership NVS had 50% co-marketing rights in US and Big 5 EU, exclusive commercialization ROW IDIX has WW rights to curren

July 31, 2012 EX-4.1

IDENIX PHARMACEUTICALS, INC. Dated as of SENIOR DEBT SECURITIES CROSS-REFERENCE TABLE(1) Section of Trust Indenture Act of 1939, as amended Section of Indenture 310(a) 6.09 310(b) 6.08 6.10 310(c) Inapplicable 311(a) 6.13 311(b) 6.13 311(c) Inapplica

Form of Senior Indenture Exhibit 4.1 IDENIX PHARMACEUTICALS, INC. and Trustee INDENTURE Dated as of SENIOR DEBT SECURITIES CROSS-REFERENCE TABLE(1) Section of Trust Indenture Act of 1939, as amended Section of Indenture 310(a) 6.09 310(b) 6.08 6.10 310(c) Inapplicable 311(a) 6.13 311(b) 6.13 311(c) Inapplicable 312(a) 4.01 4.04 312(b) 4.04(c) 312(c) 4.04(c) 313(a) 4.03 313(b) 4.03 313(c) 4.03 313(

July 31, 2012 EX-99.1

Risk Factors

EX-99.1 Exhibit 99.1 Risk Factors Our business faces many risks. The risks described below may not be the only risks we face. Additional risks we do not yet know of or which we currently believe are immaterial may also impair our business operations. If any of the events or circumstances described in the following risks actually occurs, our business, financial condition or results of operations co

July 31, 2012 EX-4.2

IDENIX PHARMACEUTICALS, INC. Dated as of SUBORDINATED DEBT SECURITIES CROSS-REFERENCE TABLE(1) Section of Trust Indenture Act of 1939, as amended Section of Indenture 310(a) 6.09 310(b) 6.08 6.10 310(c) Inapplicable 311(a) 6.13 311(b) 6.13 311(c) Ina

Form of Subordinated Indenture Exhibit 4.2 IDENIX PHARMACEUTICALS, INC. and Trustee INDENTURE Dated as of SUBORDINATED DEBT SECURITIES CROSS-REFERENCE TABLE(1) Section of Trust Indenture Act of 1939, as amended Section of Indenture 310(a) 6.09 310(b) 6.08 6.10 310(c) Inapplicable 311(a) 6.13 311(b) 6.13 311(c) Inapplicable 312(a) 4.01 4.04 312(b) 4.04(c) 312(c) 4.04(c) 313(a) 4.03 313(b) 4.03 313(

July 31, 2012 8-K

Entry into a Material Definitive Agreement, Termination of a Material Definitive Agreement, Financial Statements and Exhibits, Other Events - FORM 8-K

Form 8-K UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of The Securities Exchange Act of 1934 Date of report (Date of earliest event reported): July 31, 2012 IDENIX PHARMACEUTICALS, INC. (Exact name of registrant as specified in its charter) Delaware 000-49839 45-0478605 (State or other jurisdiction of incorporation

July 31, 2012 EX-4.4

Form of Subordinated Note (FACE OF SECURITY)

Form of Subordinated Note Exhibit 4.4 Form of Subordinated Note (FACE OF SECURITY) [Each Global Security shall bear substantially the following legend: UNLESS AND UNTIL IT IS EXCHANGED IN WHOLE OR IN PART FOR SECURITIES IN DEFINITIVE REGISTERED FORM, THIS SECURITY MAY NOT BE TRANSFERRED EXCEPT AS A WHOLE BY THE DEPOSITARY TO A NOMINEE OF THE DEPOSITARY OR BY A NOMINEE OF THE DEPOSITARY TO THE DEPO

July 31, 2012 8-K

Financial Statements and Exhibits, Other Events - FORM 8-K

Form 8-K UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of The Securities Exchange Act of 1934 Date of report (Date of earliest event reported): July 31, 2012 IDENIX PHARMACEUTICALS, INC. (Exact name of registrant as specified in its charter) Delaware 000-49839 45-0478605 (State or other jurisdiction of incorporation

July 31, 2012 EX-4.3

Form of Senior Note (FACE OF SECURITY)

Form of Senior Note Exhibit 4.3 Form of Senior Note (FACE OF SECURITY) [Each Global Security shall bear substantially the following legend: UNLESS AND UNTIL IT IS EXCHANGED IN WHOLE OR IN PART FOR SECURITIES IN DEFINITIVE REGISTERED FORM, THIS SECURITY MAY NOT BE TRANSFERRED EXCEPT AS A WHOLE BY THE DEPOSITARY TO A NOMINEE OF THE DEPOSITARY OR BY A NOMINEE OF THE DEPOSITARY TO THE DEPOSITARY OR AN

July 31, 2012 EX-10.1

IDENIX PHARMACEUTICALS, INC. SECOND AMENDED AND RESTATED STOCKHOLDERS’ AGREEMENT July 31, 2012 TABLE OF CONTENTS Page SECTION 1 DEFINITIONS 1 1.1 Definitions 1 SECTION 2 REGISTRATION RIGHTS 5 2.1 Requested Registration 5 2.2 Company Registration. 8 2

Exhibit 10.1 EXECUTION COPY IDENIX PHARMACEUTICALS, INC. SECOND AMENDED AND RESTATED STOCKHOLDERS’ AGREEMENT July 31, 2012 TABLE OF CONTENTS Page SECTION 1 DEFINITIONS 1 1.1 Definitions 1 SECTION 2 REGISTRATION RIGHTS 5 2.1 Requested Registration 5 2.2 Company Registration. 8 2.3 Expenses of Registration 8 2.4 Registration Procedures 9 2.5 Registration on Form S-3. 12 2.6 Indemnification. 13 2.7 I

July 31, 2012 EX-12

STATEMENT REGARDING COMPUTATION OF RATIO/DEFICIENCY OF EARNINGS TO FIXED CHARGES ( In Thousands) Three Months Ended For the Year Ended December 31, March 31, 2012 2011 2010 2009 2008 2007 Earnings (loss): Income (loss) before income taxes $ 11,450 $

Exhibit 12 STATEMENT REGARDING COMPUTATION OF RATIO/DEFICIENCY OF EARNINGS TO FIXED CHARGES ( In Thousands) Three Months Ended For the Year Ended December 31, March 31, 2012 2011 2010 2009 2008 2007 Earnings (loss): Income (loss) before income taxes $ 11,450 $ (52,040 ) $ (61,595 ) $ (53,168 ) $ (70,162 ) $ (82,269 ) Add: Fixed Charges 5 163 159 146 150 177 Total earnings (loss) $ 11,455 $ (51,877

July 31, 2012 S-3ASR

- S-3ASR

Table of Contents As filed with the Securities and Exchange Commission on July 31, 2012 Registration No.

July 31, 2012 424B5

Sole book-running manager J.P. Morgan Lead manager Leerink Swann

424B5 Table of Contents Filed Pursuant to Rule 424(b)(5) Registration File No. 333-182953 The information in this preliminary prospectus supplement is not complete and may be changed. This preliminary prospectus supplement and the accompanying prospectus are not an offer to sell these securities, and we are not soliciting offers to buy these securities in any jurisdiction where the offer or sale i

June 20, 2012 8-K

Financial Statements and Exhibits, Other Events - FORM 8-K

Form 8-K UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): June 19, 2012 Idenix Pharmaceuticals, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 000-49839 45-0478605 (State or Other Jurisdiction of Incorporation (Com

June 20, 2012 EX-99.1

Idenix Announces Positive Clinical Data for HCV Drug Candidates IDX184 and IDX719 — In an interim analysis from an ongoing phase IIb clinical trial of IDX184, an HCV nucleotide inhibitor, 89% of patients who completed an additional 12 weeks of pegyla

Press Release dated June 19, 2012 Exhibit 99.1 FOR IMMEDIATE RELEASE Idenix Pharmaceuticals Contacts: Kelly Barry (617) 995-9033 (media) Teri Dahlman (617) 995-9807 (investors) Idenix Announces Positive Clinical Data for HCV Drug Candidates IDX184 and IDX719 — In an interim analysis from an ongoing phase IIb clinical trial of IDX184, an HCV nucleotide inhibitor, 89% of patients who completed an ad

June 11, 2012 EX-99.1

IDENIX PHARMACEUTICALS, INC. 2012 STOCK INCENTIVE PLAN

Exhibit 99.1 IDENIX PHARMACEUTICALS, INC. 2012 STOCK INCENTIVE PLAN 1. Purpose The purpose of this 2012 Stock Incentive Plan (the “Plan”) of Idenix Pharmaceuticals, Inc. a Delaware corporation (the “Company”), is to advance the interests of the Company’s stockholders by enhancing the Company’s ability to attract, retain and motivate persons who are expected to make important contributions to the C

June 11, 2012 S-8

- FORM S-8

As filed with the Securities and Exchange Commission on June 11, 2012 Registration No.

June 8, 2012 8-K

Submission of Matters to a Vote of Security Holders

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of The Securities Exchange Act of 1934 Date of report (Date of earliest event reported): June 7, 2012 IDENIX PHARMACEUTICALS, INC. (Exact name of registrant as specified in its charter) Delaware 000-49839 45-0478605 (State or other jurisdiction of incorporation or organiz

May 21, 2012 8-K

Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of The Securities Exchange Act of 1934 Date of report (Date of earliest event reported): May 15, 2012 IDENIX PHARMACEUTICALS, INC. (Exact name of registrant as specified in its charter) Delaware 000-49839 45-0478605 (State or other jurisdiction of incorporation or organiz

May 2, 2012 8-K

Financial Statements and Exhibits, Results of Operations and Financial Condition

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): May 2, 2012 Idenix Pharmaceuticals, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 000-49839 45-0478605 (State or Other Juris- diction of Incorporation (Commission F

May 2, 2012 EX-99.1

IDENIX PHARMACEUTICALS REPORTS FIRST QUARTER 2012 FINANCIAL RESULTS AND HCV DEVELOPMENT PROGRAM PROGRESS

Press Release Exhibit 99.1 FOR IMMEDIATE RELEASE Idenix Pharmaceuticals Contacts: Kelly Barry (617) 995-9033 (media) Teri Dahlman (617) 995-9807 (investors) IDENIX PHARMACEUTICALS REPORTS FIRST QUARTER 2012 FINANCIAL RESULTS AND HCV DEVELOPMENT PROGRAM PROGRESS CAMBRIDGE, Mass., May 2, 2012 — Idenix Pharmaceuticals, Inc. (NASDAQ: IDIX), a biopharmaceutical company engaged in the discovery and deve

May 2, 2012 10-Q

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q (Mark One) x QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the Quarterly Period Ended March 31, 2012 Or ? TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number 000-49839 Idenix Pha

April 25, 2012 DEF 14A

- DEFINITIVE PROXY STATEMENT

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A (Rule 14a-101) INFORMATION REQUIRED IN PROXY STATEMENT SCHEDULE 14A INFORMATION Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. ) Filed by the Registrant þ Filed by a Party other than the Registrant ¨ Check the appropriate box: ¨ Preliminary Proxy S

April 24, 2012 8-K

Financial Statements and Exhibits, Other Events

Form 8-K UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): April 19, 2012 Idenix Pharmaceuticals, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 000-49839 45-0478605 (State or Other Jurisdiction of Incorporation (Co

April 24, 2012 EX-99.1

IDENIX PHARMACEUTICALS PROVIDES UPDATE ON HEPATITIS C CLINICAL DEVELOPMENT PROGRAMS - IDX719 demonstrates pan-genotypic activity at single doses in HCV-infected patients achieving greater than 3 log10 viral load reductions in the 100 mg dose group ac

Press Release Exhibit 99.1 FOR IMMEDIATE RELEASE Idenix Pharmaceuticals Contacts: Kelly Barry (617) 995-9033 (media) Teri Dahlman (617) 995-9807 (investors) IDENIX PHARMACEUTICALS PROVIDES UPDATE ON HEPATITIS C CLINICAL DEVELOPMENT PROGRAMS - IDX719 demonstrates pan-genotypic activity at single doses in HCV-infected patients achieving greater than 3 log10 viral load reductions in the 100 mg dose g

March 29, 2012 8-K

Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers - FORM 8-K

Form 8-K UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of The Securities Exchange Act of 1934 Date of report (Date of earliest event reported): March 27, 2012 IDENIX PHARMACEUTICALS, INC. (Exact name of registrant as specified in its charter) Delaware 000-49839 45-0478605 (State or other jurisdiction of incorporation

March 6, 2012 EX-10.12

FIFTH AMENDMENT OF LEASE

Exhibit 10.12 Exhibit 10.12 FIFTH AMENDMENT OF LEASE THIS FIFTH AMENDMENT OF LEASE is made as of this day of , 2011 between RB KENDALL FEE, LLC, a Delaware limited liability company having a mailing address c/o The Beal Companies, LLP, 177 Milk Street, Boston, Massachusetts (“Landlord”) and IDENIX PHARMACEUTICALS, INC., having a mailing address at 60 Hampshire Street, Cambridge, Massachusetts 0213

March 6, 2012 EX-21.1

Subsidiaries Name of Subsidiary State or Other Jurisdiction of Incorporation or Organization Idenix (Massachusetts) Inc. Massachusetts Idenix (Cayman) Limited Cayman Islands Idenix SARL* France

Exhibit 21.1 Subsidiaries Name of Subsidiary State or Other Jurisdiction of Incorporation or Organization Idenix (Massachusetts) Inc. Massachusetts Idenix (Cayman) Limited Cayman Islands Idenix SARL* France * Wholly-owned by Idenix (Cayman) Limited

March 6, 2012 10-K

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 Form 10-K

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 Form 10-K (Mark One) x ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31, 2011 or ? TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number 000-498

March 6, 2012 EX-99.1

IDENIX PHARMACEUTICALS ELECTS THOMAS HODGSON AS CHAIRMAN OF THE BOARD AND APPOINTS MICHAEL WYZGA TO ITS BOARD OF DIRECTORS

EX-99.1 Exhibit 99.1 FOR IMMEDIATE RELEASE Idenix Pharmaceuticals Contacts: Kelly Barry (617) 995-9033 (media) Teri Dahlman (617) 995-9807 (investors) IDENIX PHARMACEUTICALS ELECTS THOMAS HODGSON AS CHAIRMAN OF THE BOARD AND APPOINTS MICHAEL WYZGA TO ITS BOARD OF DIRECTORS Cambridge, MA, March 1, 2012 - Idenix Pharmaceuticals, Inc. (NASDAQ: IDIX), a biopharmaceutical company engaged in the discove

March 6, 2012 8-K

Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers, Financial Statements and Exhibits - 8-K

8-K UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of The Securities Exchange Act of 1934 Date of report (Date of earliest event reported): February 29, 2012 IDENIX PHARMACEUTICALS, INC. (Exact name of registrant as specified in its charter) Delaware 000-49839 45-0478605 (State or other jurisdiction of incorporation o

February 23, 2012 EX-99.1

IDENIX PHARMACEUTICALS REPORTS FOURTH QUARTER AND YEAR END 2011 FINANCIAL RESULTS AND PROVIDES PIPELINE UPDATE

Exhibit 99.1 Exhibit 99.1 FOR IMMEDIATE RELEASE Idenix Pharmaceuticals Contacts: Kelly Barry (617) 995-9033 (media) Teri Dahlman (617) 995-9807 (investors) IDENIX PHARMACEUTICALS REPORTS FOURTH QUARTER AND YEAR END 2011 FINANCIAL RESULTS AND PROVIDES PIPELINE UPDATE CAMBRIDGE, Mass., February 23, 2012 — Idenix Pharmaceuticals, Inc. (NASDAQ: IDIX), a biopharmaceutical company engaged in the discove

February 23, 2012 8-K

Financial Statements and Exhibits, Results of Operations and Financial Condition, Other Events

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): February 23, 2012 Idenix Pharmaceuticals, Inc. (Exact name of registrant as specified in its charter) Delaware 000-49839 45-0478605 (State or other jurisdiction of incorporation) (Com

February 14, 2012 SC 13G/A

IDIX / Idenix Pharmaceuticals Inc / Brookside Capital Trading Fund, L.P. - AMENDMENT NO.2 TO SCHEDULE 13G Passive Investment

Amendment No.2 to Schedule 13G UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G (Rule 13d-102) Information Statement Pursuant to Rules 13d-1 and 13d-2 Under the Securities Exchange Act of 1934 (Amendment No. 2)* Idenix Pharmaceuticals, Inc. (Name of Issuer) Common Stock, par value $0.001 (Title of Class of Securities) 45166R204 (CUSIP Number) December 31, 2011 (

February 10, 2012 SC 13G

IDIX / Idenix Pharmaceuticals Inc / BAUPOST GROUP LLC/MA - IDIX13GORIG Passive Investment

CUSIP NO. 45166R204 13G PAGE 1 OF 10 SECURITIES AND EXCHANGE COMMISSION Washington, DC 20549 SCHEDULE 13G (Rule 13d-102) INFORMATION TO BE INCLUDED IN STATEMENTS FILED PURSUANT TO RULES 13d-1(b)(c), AND (d) AND AMENDMENTS THERETO FILED PURSUANT TO RULE 13d-2(b) Idenix Pharmaceuticals, Inc. (Name of Issuer) Common Stock (Title of Class of Securities) 45166R204 (CUSIP Number) December 31, 2011 (Date

February 10, 2012 SC 13G/A

IDIX / Idenix Pharmaceuticals Inc / PRICE T ROWE ASSOCIATES INC /MD/ - 12/31/2011 Passive Investment

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 (Amendment No. 2)* IDENIX PHARMACEUTICALS INC (Name of Issuer) COMMON STOCK (Title of Class of Securities) 45166R204 (CUSIP Number) December 31, 2011 (Date of Event which Requires Filing of Statement) Check the appropriate box to designate the Rule pursuant to which this S

February 6, 2012 8-K

Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers - FORM 8-K

Form 8-K UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): February 3, 2012 IDENIX PHARMACEUTICALS, INC. (Exact name of registrant as specified in its charter) Delaware 000-49839 45-0478605 (State or other jurisdiction of incorporati

February 3, 2012 EX-99.1

IDENIX ANNOUNCES REMOVAL OF THE PARTIAL CLINICAL HOLD ON HCV NUCLEOTIDE INHIBITOR, IDX184

EX-99.1 Exhibit 99.1 FOR IMMEDIATE RELEASE Idenix Pharmaceuticals Contacts: Kelly Barry (617) 995-9033 (media) Teri Dahlman (617) 995-9807 (investors) IDENIX ANNOUNCES REMOVAL OF THE PARTIAL CLINICAL HOLD ON HCV NUCLEOTIDE INHIBITOR, IDX184 CAMBRIDGE, Mass., February 3, 2012 — Idenix Pharmaceuticals, Inc. (NASDAQ: IDIX), a biopharmaceutical company engaged in the discovery and development of drugs

February 3, 2012 8-K

Financial Statements and Exhibits, Other Events - FORM 8-K

FORM 8-K UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): February 3, 2012 Idenix Pharmaceuticals, Inc. (Exact name of registrant as specified in its charter) Delaware 000-49839 45-0478605 (State or other jurisdiction of incorporati

January 9, 2012 EX-99.2

EX-99.2

Exhibit 99.2 Exhibit 99.2 1 Interim IDX184 Phase IIb Data and Development Pipeline Update Conference Call January 9, 2012 2 Building a Leading Antiviral Franchise Safe Harbor Statement This presentation includes forward-looking statements about Idenix and its business, including without limitation, statements regarding drug discovery, research and clinical development, regulatory approval processe

January 9, 2012 8-K

Financial Statements and Exhibits, Other Events - FORM 8-K

Form 8-K UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): January 9, 2012 Idenix Pharmaceuticals, Inc. (Exact name of registrant as specified in its charter) Delaware 000-49839 45-0478605 (State or other Jurisdiction of Incorporatio

January 9, 2012 EX-99.1

IDENIX REPORTS POSITIVE INTERIM DATA FOR HCV NUCLEOTIDE INHIBITOR, IDX184

Exhibit 99.1 FOR IMMEDIATE RELEASE Idenix Pharmaceuticals Contacts: Kelly Barry (617) 995-9033 (media) Teri Dahlman (617) 995-9807 (investors) IDENIX REPORTS POSITIVE INTERIM DATA FOR HCV NUCLEOTIDE INHIBITOR, IDX184 • No serious adverse events observed in phase IIb study of IDX184; Data Safety Monitoring Board (DSMB) recommends continuation of the clinical trial • In the 100 mg IDX184 arm, 73% of

December 22, 2011 8-K

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): December 16, 2011 IDENIX PHARMACE

Form 8-K UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): December 16, 2011 IDENIX PHARMACEUTICALS, INC. (Exact name of registrant as specified in its charter) Delaware 000-49839 45-0478605 (State or other jurisdiction of incorporat

December 15, 2011 EX-1

LOCK-UP AGREEMENT

Exhibit 1 LOCK-UP AGREEMENT November l5, 2011 J.P. MORGAN SECURITIES LLC 383 Madison Avenue New York, NY 10179 Re: Idenix Pharmaceuticals, Inc. ? Public Offering Ladies and Gentlemen: The undersigned understands that you propose to enter into an Underwriting Agreement (the ?Underwriting Agreement?) with Idenix Pharmaceuticals, Inc., a Delaware corporation (the ?Company?), providing for the public

December 15, 2011 SC 13D/A

UNITED STATES

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13D/A Under the Securities Exchange Act of 1934 (Amendment No. 6)* Idenix Pharmaceuticals, Inc. (Name of Issuer) Common Stock (Title of Class of Securities) 45166R 20 4 (CUSIP Number) Matt Owens, Esq. Adam H. Golden, Esq. Novartis Pharma AG Kaye Scholer LLP Lichtstrasse 35 425 Park Avenue CH-4056 Basel, Switzerland Ne

November 16, 2011 EX-1.1

IDENIX PHARMACEUTICALS, INC. 9,393,416 Shares of Common Stock Underwriting Agreement

exv1w1 EXHIBIT 1.1 Execution Version IDENIX PHARMACEUTICALS, INC. 9,393,416 Shares of Common Stock Underwriting Agreement November 16, 2011 J.P. Morgan Securities LLC 383 Madison Avenue New York, New York 10179 Ladies and Gentlemen: Idenix Pharmaceuticals, Inc., a Delaware corporation (the “Company”), proposes to issue and sell to you (the “Underwriter”), an aggregate of 9,393,416 shares of common

November 16, 2011 FWP

Issuer Idenix Pharmaceuticals, Inc. (NASDAQ: IDIX) Common stock offered by Idenix 9,393,416 shares of common stock. In addition, we have granted the underwriters a 30-day option to purchase up to 1,409,013 additional shares of common stock to cover o

FWP 1 b88933bfwp.htm FWP Issuer Free Writing Prospectus dated November 16, 2011 Filed Pursuant to Rule 433 Registration No. 333-177167 (Relating to Preliminary Prospectus Supplement dated November 15, 2011) We have filed with the Securities and Exchange Commission (the “SEC”) a registration statement and a preliminary prospectus supplement (together with the prospectus dated October 14, 2011, the

November 16, 2011 8-K

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): November 16, 2011 Idenix Pharmace

e8vk Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.

November 16, 2011 EX-99.1

Idenix Pharmaceuticals Prices Public Offering of Common Stock

exv99w1 Exhibit 99.1 Idenix Pharmaceuticals Contacts: Kelly Barry (617) 995-9033 (media) Eric Hoffman (617) 224-4485 (investors) Idenix Pharmaceuticals Prices Public Offering of Common Stock CAMBRIDGE, Mass., November 16, 2011 —Idenix Pharmaceuticals, Inc. (Nasdaq: IDIX), a biopharmaceutical company engaged in the discovery and development of drugs for the treatment of human viral diseases, today

November 16, 2011 SC 13G/A

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G (Rule 13d-102) Information Statement Pursuant to Rules 13d-1 and 13d-2 Under the Securities Exchange Act of 1934 (Amendment No. 1)* Idenix Pharmaceuticals, Inc. (Nam

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G (Rule 13d-102) Information Statement Pursuant to Rules 13d-1 and 13d-2 Under the Securities Exchange Act of 1934 (Amendment No. 1)* Idenix Pharmaceuticals, Inc. (Name of Issuer) Common Stock, par value $0.001 (Title of Class of Securities) 45166R204 (CUSIP Number) October 27, 2011 (Date of Event Which Requires Fil

November 16, 2011 424B5

Sole book-running manager J.P. Morgan

Table of Contents Filed Pursuant to Rule 424(b)(5) Registration File No. 333-177167 Prospectus supplement (To Prospectus dated October 14, 2011) 9,393,416 shares Common Stock We are offering 9,393,416 shares of common stock. Shares of our common stock trade on The NASDAQ Global Market under the symbol ?IDIX?. The last reported sale price on November 15, 2011 was $7.15 per share. Per Share Total Pu

November 15, 2011 424B5

Sole book-running manager J.P. Morgan

Table of Contents The information in this preliminary prospectus supplement is not complete and may be changed.

November 2, 2011 EX-99.1

IDENIX PHARMACEUTICALS REPORTS THIRD QUARTER AND NINE MONTH 2011 FINANCIAL RESULTS AND PROVIDES PIPELINE UPDATE

Exhibit 99.1 Exhibit 99.1 FOR IMMEDIATE RELEASE Idenix Pharmaceuticals Contacts: Kelly Barry (617) 995-9033 (media) Eric Hoffman (617) 224-4485 (investors) IDENIX PHARMACEUTICALS REPORTS THIRD QUARTER AND NINE MONTH 2011 FINANCIAL RESULTS AND PROVIDES PIPELINE UPDATE CAMBRIDGE, Mass., Nov. 2, 2011 /PRNewswire/ — Idenix Pharmaceuticals, Inc. (NASDAQ: IDIX), a biopharmaceutical company engaged in th

November 2, 2011 10-Q

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q (Mark One) ? QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the Quarterly Period Ended September 30, 2011 Or o TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file numbe

November 2, 2011 8-K

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 OR 15(d) of The Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): November 2, 2011 Idenix Pharmaceu

Form 8-K UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 OR 15(d) of The Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): November 2, 2011 Idenix Pharmaceuticals, Inc. (Exact name of registrant as specified in its charter) Delaware 000-49839 45-0478605 (State or other jurisdiction of incorporati

October 12, 2011 S-3/A

As filed with the Securities and Exchange Commission on October 12, 2011

S-3/A 1 b87938bsv3za.htm S-3/A As filed with the Securities and Exchange Commission on October 12, 2011 Registration No. 333-177167 UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 AMENDMENT NO 1. TO FORM S-3 REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933 IDENIX PHARMACEUTICALS, INC. (Exact name of registrant as specified in its charter) Delaware 45-0478605 (State o

October 4, 2011 S-3

As filed with the Securities and Exchange Commission on October 4, 2011

S-3 1 b87938sv3.htm FORM S-3 Table of Contents As filed with the Securities and Exchange Commission on October 4, 2011 Registration No. 333- UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 Form S-3 REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933 IDENIX PHARMACEUTICALS, INC. (Exact name of registrant as specified in its charter) Delaware 45-0478605 (State or other ju

September 8, 2011 SC 13G/A

SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G UNDER THE SECURITIES EXCHANGE ACT OF 1934 (Amendment No. 1)* IDENIX PHARMACEUTICALS INC. (Name of Issuer) COMMON STOCK (Title of Class of Securities) (CUSIP Number) August 31, 201

sc13gza SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G UNDER THE SECURITIES EXCHANGE ACT OF 1934 (Amendment No. 1)* IDENIX PHARMACEUTICALS INC. (Name of Issuer) COMMON STOCK (Title of Class of Securities) 45166R204 (CUSIP Number) August 31, 2011 (Date of Event Which Requires Filing of this Statement) Check the appropriate box to designate the Rule pursuant to which this Sch

August 9, 2011 10-Q

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q (Mark One) þ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the Quarterly Period Ended June 30, 2011 Or o TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number 000

August 9, 2011 EX-3.1

EX-3.1 Certificate of Amendment of Restated Certificate of Incorporation

Exhibit 3.1 CERTIFICATE OF AMENDMENT OF RESTATED CERTIFICATE OF INCORPORATION OF IDENIX PHARMACEUTICALS, INC. Idenix Pharmaceuticals, Inc. (the ?Corporation?), organized and existing under and by virtue of the General Corporation Law of the State of Delaware, does hereby certify as follows: The Board of Directors of the Corporation duly adopted at a meeting duly called, pursuant to Section 242 of

August 8, 2011 EX-99.1

IDENIX PHARMACEUTICALS REPORTS SECOND QUARTER AND SIX MONTH 2011 FINANCIAL RESULTS AND PROVIDES PIPELINE UPDATE

Exhibit 99.1 Exhibit 99.1 IDENIX PHARMACEUTICALS REPORTS SECOND QUARTER AND SIX MONTH 2011 FINANCIAL RESULTS AND PROVIDES PIPELINE UPDATE Cambridge, Mass., August 8, 2011 - • Lead nucleotide polymerase inhibitor IDX184 advancing clinically — The Company has initiated dosing of IDX184 in combination with pegylated interferon and ribavirin (Peg-IFN/RBV) in a Phase IIb hepatitis C virus (HCV) trial •

August 8, 2011 8-K

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): August 8, 2011 Idenix Pharmaceuti

Form 8-K UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): August 8, 2011 Idenix Pharmaceuticals, Inc. (Exact name of registrant as specified in its charter) Delaware 000-49839 45-0478605 (State or other Jurisdiction of Incorporation

June 24, 2011 EX-10.1

/s/ Daniella Beckman Daniella Beckman

Exhibit 10.1 Exhibit 10.1 June 20, 2011 CONFIDENTIAL Daniella Beckman Dear Daniella: On behalf of Idenix Pharmaceuticals, Inc. (“Idenix” or the “Company”), I am pleased to offer you the position of Vice President, Chief Financial Officer and Treasurer, reporting directly to me as President and Chief Executive Officer. The terms of our employment offer are set forth below. 1. Commencement. Your pro

June 24, 2011 8-K

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 OR 15(d) of The Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): June 20, 2011 IDENIX PHARMACEUTIC

Form 8-K UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 OR 15(d) of The Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): June 20, 2011 IDENIX PHARMACEUTICALS, INC. (Exact name of registrant as specified in its charter) Delaware 000-49839 45-0478605 (State or other jurisdiction of incorporation)

June 6, 2011 8-K

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): June 2, 2011 IDENIX PHARMACEUTICA

Form 8-K UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): June 2, 2011 IDENIX PHARMACEUTICALS, INC. (Exact name of registrant as specified in its charter) Delaware 000-49839 45-0478605 (State or other Jurisdiction of Incorporation)

April 28, 2011 10-Q

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q (Mark One) ? QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the Quarterly Period Ended March 31, 2011 Or o TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number 00

April 27, 2011 EX-99.1

IDENIX PHARMACEUTICALS REPORTS FIRST QUARTER 2011 FINANCIAL RESULTS

Exhibit 99.1 FOR IMMEDIATE RELEASE Idenix Pharmaceuticals Contacts: Kelly Barry (617) 995-9033 (media) Eric Hoffman (617) 224-4485 (investors) IDENIX PHARMACEUTICALS REPORTS FIRST QUARTER 2011 FINANCIAL RESULTS Cambridge, Mass., — April 27, 2011 - Idenix Pharmaceuticals, Inc. (NASDAQ: IDIX), a biopharmaceutical company engaged in the discovery and development of drugs for the treatment of human vi

April 27, 2011 8-K

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): April 27, 2011 Idenix Pharmaceuti

Form 8-K UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): April 27, 2011 Idenix Pharmaceuticals, Inc. (Exact name of registrant as specified in its charter) Delaware 000-49839 45-0478605 (State or other Jurisdiction of Incorporation

April 25, 2011 DEF 14A

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. )

Definitive Proxy Statement Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.

April 20, 2011 EX-99.1

GENERAL WAIVER AND CONSENT

EX-99.1 2 a11-104481ex99d1.htm EX-99.1 Exhibit 1 GENERAL WAIVER AND CONSENT This General Waiver and Consent is made and effective as of the 6th of April, 2011 (“Effective Date”) between Idenix Pharmaceuticals, Inc., with offices at 60 Hampshire Street, Cambridge, Massachusetts 02139, USA (“Idenix US”) and Novartis Pharma AG, with offices at Forum 1, Novartis Campus, 4056 Basel, Switzerland (“Novar

April 20, 2011 EX-99.6

LOCK-UP AGREEMENT

EX-99.6 3 a11-104481ex99d6.htm EX-99.6 Exhibit 6 LOCK-UP AGREEMENT April 6, 2011 J.P. MORGAN SECURITIES LLC 383 Madison Avenue New York, NY 10179 Re: Idenix Pharmaceuticals, Inc. — Public Offering Ladies and Gentlemen: The undersigned understands that you propose to enter into an Underwriting Agreement (the “Underwriting Agreement”) with Idenix Pharmaceuticals, Inc., a Delaware corporation (the “C

April 20, 2011 SC 13D/A

UNITED STATES

SC 13D/A 1 a11-104481sc13da.htm SC 13D/A UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13D/A Under the Securities Exchange Act of 1934 (Amendment No. 5)* Idenix Pharmaceuticals, Inc. (Name of Issuer) Common Stock (Title of Class of Securities) 45166R 20 4 (CUSIP Number) Matt Owens, Esq. Adam H. Golden, Esq. Novartis Pharma AG Kaye Scholer LLP Lichtstrasse 35 425

April 18, 2011 SC 13G

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G (Rule 13d-102) Information Statement Pursuant to Rules 13d-1 and 13d-2 Under the Securities Exchange Act of 1934 (Amendment No. )* Idenix Pharmaceuticals, Inc. (Name

Schedule 13G UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G (Rule 13d-102) Information Statement Pursuant to Rules 13d-1 and 13d-2 Under the Securities Exchange Act of 1934 (Amendment No. )* Idenix Pharmaceuticals, Inc. (Name of Issuer) Common Stock, par value $0.001 (Title of Class of Securities) 45166R204 (CUSIP Number) April 8, 2011 (Date of Event Which Req

April 11, 2011 8-K

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 OR 15(d) of The Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): April 8, 2011 Idenix Pharmaceutic

Form 8-K UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 OR 15(d) of The Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): April 8, 2011 Idenix Pharmaceuticals, Inc. (Exact name of registrant as specified in its charter) Delaware 000-49839 45-0478605 (State or other jurisdiction of incorporation)

April 11, 2011 EX-1.1

IDENIX PHARMACEUTICALS, INC. 18,310,000 Shares of Common Stock Underwriting Agreement

Exhibit 1.1 Exhibit 1.1 Execution Version IDENIX PHARMACEUTICALS, INC. 18,310,000 Shares of Common Stock Underwriting Agreement April 8, 2011 J.P. Morgan Securities LLC 383 Madison Avenue New York, New York 10172 Ladies and Gentlemen: Idenix Pharmaceuticals, Inc., a Delaware corporation (the “Company”), proposes to issue and sell to you (the “Underwriter”), an aggregate of 18,310,000 shares of Com

April 11, 2011 EX-10.1

CONCURRENT PRIVATE PLACEMENT STOCK PURCHASE AGREEMENT by and between NOVARTIS PHARMA AG IDENIX PHARMACEUTICALS, INC.

Exhibit 10.1 Exhibit 10.1 CONCURRENT PRIVATE PLACEMENT STOCK PURCHASE AGREEMENT by and between NOVARTIS PHARMA AG and IDENIX PHARMACEUTICALS, INC. Table of Contents Page 1. Purchase and Sale of Stock 1 1.1 Sale and Issuance of the Shares 1 1.2 Closing 1 1.3 Delivery 2 1.4 Further Assurances 2 2. Representations and Warranties of the Company 2 2.1 Organization; Good Standing; Qualification 2 2.2 Au

April 11, 2011 EX-99.1

Idenix Pharmaceuticals Prices Public Offering of Common Stock

Exhibit 99.1 DRAFT- NOT FOR IMMEDIATE RELEASE Idenix Pharmaceuticals Contacts: Kelly Barry (617) 995-9033 (media) Eric Hoffman (617) 224-4485 (investors) Idenix Pharmaceuticals Prices Public Offering of Common Stock CAMBRIDGE, Mass., April 8, 2011 —Idenix Pharmaceuticals, Inc. (Nasdaq: IDIX), a biopharmaceutical company engaged in the discovery and development of drugs for the treatment of human v

April 8, 2011 PRE 14A

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. )

pre14a Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.

April 8, 2011 FWP

Issuer Idenix Pharmaceuticals, Inc. (NASDAQ: IDIX) Common stock offered by Idenix 18,310,000 shares of common stock. In addition, we have granted the underwriters a 30-day option to purchase up to 2,746,500 additional shares of common stock to cover

FWP 1 b85926f1fwp.htm FWP Issuer Free Writing Prospectus dated April 8, 2011 Filed Pursuant to Rule 433 Registrations No. 333-153471 and 333-173374 (Relating to Preliminary Prospectus Supplement dated April 7, 2011) We have filed with the Securities and Exchange Commission (the “SEC”) a registration statement and a preliminary prospectus supplement (together with the prospectus dated October 17, 2

April 8, 2011 FWP

Issuer Idenix Pharmaceuticals, Inc. (NASDAQ: IDIX) Common stock offered by Idenix 18,310,000 shares of common stock. In addition, we have granted the underwriters a 30-day option to purchase up to 2,746,500 additional shares of common stock to cover

FWP 1 b85926f2fwp.htm FWP Issuer Free Writing Prospectus dated April 8, 2011 Filed Pursuant to Rule 433 Registrations No. 333-153471 and 333-173374 (Relating to Preliminary Prospectus Supplement dated April 7, 2011) We have filed with the Securities and Exchange Commission (the “SEC”) a registration statement and a preliminary prospectus supplement (together with the prospectus dated October 17, 2

April 8, 2011 S-3MEF

As filed with the Securities and Exchange Commission on April 8, 2011

S-3MEF 1 b85926mfsv3mef.htm S-3MEF Table of Contents As filed with the Securities and Exchange Commission on April 8, 2011 Registration No. 333- UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM S-3 REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933 IDENIX PHARMACEUTICALS, INC. (Exact name of registrant as specified in its charter) Delaware 45-0478605 (State or othe

April 8, 2011 424B5

Sole book-running manager J.P. Morgan

Table of Contents Filed Pursuant to Rule 424(b)(5) Registration No. 333-153471 Prospectus supplement (To Prospectus dated October 17, 2008) 18,310,000 shares Common Stock We are offering 18,310,000 shares of our common stock. Shares of our common stock trade on the Nasdaq Global Market under the symbol “IDIX”. The last reported sale price on April 7, 2011 was $3.24 per share. Concurrently with the

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