SECURITIES AND EXCHANGE COMMISSION

Commission file number 000-49839

Idenix Pharmaceuticals, Inc.

Registrant’s telephone number, including area code: (617) 995-9800

     Indicate by check mark whether the registrant: (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports) and (2) has been subject to such filing requirements for the past 90 days. Yes [  ] No [X]

     Indicate by check mark whether the registrant is an accelerated filer (as defined in Rule 12b-2 of the Exchange Act). Yes [  ] No [X]

     As of August 15, 2004, the number of shares of the registrant’s common stock, par value $.001 per share, outstanding was 47,904,600 shares.

IDENIX PHARMACEUTICALS, INC.

INDEX

2

IDENIX PHARMACEUTICALS, INC.

CONDENSED CONSOLIDATED BALANCE SHEETS

(IN THOUSANDS, EXCEPT SHARE DATA)
(UNAUDITED)

The accompanying notes are an integral part of these condensed consolidated financial statements.

3

IDENIX PHARMACEUTICALS, INC.

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS

(IN THOUSANDS, EXCEPT PER SHARE DATA)
(UNAUDITED)

The accompanying notes are an integral part of these condensed consolidated financial statements.

4

IDENIX PHARMACEUTICALS, INC.

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS

(IN THOUSANDS, EXCEPT PER SHARE DATA)
(UNAUDITED)

The accompanying notes are an integral part of these condensed consolidated financial statements.

5

IDENIX PHARMACEUTICALS, INC.

The accompanying notes are an integral part of these condensed consolidated financial statements.

6

IDENIX PHARMACEUTICALS, INC.

NOTES TO THE CONDENSED CONSOLIDATED FINANCIAL STATEMENTS
(UNAUDITED)

1. DESCRIPTION OF BUSINESS

     Idenix Pharmaceuticals, Inc. (the “Company”) is a biopharmaceutical company engaged in the discovery and development of drugs for the treatment of human viral and other infectious diseases. The Company’s current focus is on the treatment of infections caused by hepatitis B virus (“HBV”), hepatitis C virus (“HCV”) and human immunodeficiency virus (“HIV”).

2. BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES

     The accompanying condensed consolidated financial statements are unaudited and have been prepared by the Company in accordance with accounting principles generally accepted in the United States of America.

     The accompanying condensed consolidated financial statements reflect the operations of the Company and its wholly owned subsidiaries. All significant intercompany accounts and transactions have been eliminated.

     Certain information and footnote disclosures normally included in the Company’s annual consolidated financial statements have been condensed or omitted. Certain prior year amounts have been reclassified to conform to current year presentation. The interim financial statements, in the opinion of management, reflect all adjustments (including normal recurring accruals) necessary for a fair statement of the financial position and results of operations for the interim periods presented.

     The results of operations for the interim periods are not necessarily indicative of the results of operations to be expected for any future period or the fiscal year. These interim financial statements should be read in conjunction with the audited financial statements for the year ended December 31, 2003, which are included in the Company’s Registration Statement No. 333-111157 on Form S-1, as amended, which has been filed with the Securities and Exchange Commission (the “SEC”).

Revenue Recognition

     The Company recognizes revenues in accordance with the SEC’s Staff Accounting Bulletin No. 104, “Revenue Recognition in Financial Statements,” which allows revenue to be recorded under the following conditions: there is persuasive evidence that an arrangement exists, the price is fixed and determinable and collectibility is reasonably assured. The Company records revenue earned under collaborative research and development arrangements and government grants.

     Collaborative Research and Development Revenue — Revenue related to collaborative research and development arrangements includes nonrefundable license fees, milestones and research and development payments from the Company’s collaborative partners. Where the Company has continuing performance obligations under the terms of a collaborative arrangement, nonrefundable license fees are recognized as revenue over the specified development period as the Company completes its performance obligations. When the Company’s level of effort is relatively constant over the performance period, the revenue is recognized on a straight-line basis. The determination of the performance period involves judgment on the part of management. If the Company cannot reasonably estimate its costs, then it recognizes the license fee revenue on a straight-line basis over the performance period. Payments received from collaborative partners for research and development efforts by the Company are recognized as revenue over the contract

7

IDENIX PHARMACEUTICALS, INC.

NOTES TO THE CONDENSED CONSOLIDATED FINANCIAL STATEMENTS
(UNAUDITED) — CONTINUED

term as the related costs are incurred. Revenues from milestones related to an arrangement under which the Company has continuing performance obligations, if deemed substantive, are recognized as revenue upon achievement of the milestone. Milestones are considered substantive if all of the following conditions are met: the milestone is nonrefundable; achievement of the milestone was not reasonably assured at the inception of the arrangement; substantive effort is involved to achieve the milestone; and the amount of the milestone appears reasonable in relation to the effort expended, the other milestones in the arrangement and the related risk associated with the achievement of the milestone. If any of these conditions are not met, the milestone payment is deferred and recognized as revenue as the Company completes its performance obligations.

     Where the Company has no continuing involvement under a collaborative arrangement, the Company records nonrefundable license fee revenue when the Company has the contractual right to receive the payment, in accordance with the terms of the license agreement, and records milestones upon appropriate notification to the Company of achievement of the milestones by the collaborative partner.

     In March 2003, the Company entered into a final settlement agreement with Sumitomo Pharmaceuticals Co., Ltd. (“Sumitomo”) under which the rights to develop and commercialize telbivudine, the Company’s lead drug candidate for the treatment of hepatitis B, in Japan, China, South Korea and Taiwan previously granted to Sumitomo were returned to the Company. This agreement became effective upon consummation of the collaboration with Novartis Pharma AG (“Novartis”) in May 2003. The Company repurchased these rights for $5,000,000 in the year ended December 31, 2003. The repurchase of these rights resulted in a $4,571,000 reversal of revenue previously recognized through the Company’s arrangements with Sumitomo. The remaining amount of $429,000 was recorded as a reduction of deferred revenue. The Company has $4,272,000 included in deferred revenue at each of December 31, 2003 and June 30, 2004 representing amounts received from Sumitomo that have not been included in revenue to date. The Company must pay an additional $5,000,000 to Sumitomo upon the first commercial sale of telbivudine in Japan. This payment will be recorded first as a reduction of the remaining deferred revenue, with the excess recorded as an expense. If and when the Company determines that it will not seek regulatory approval for telbivudine in Japan, the Company would have no further obligations under the settlement arrangement with Sumitomo and, therefore, the $4,272,000 of remaining deferred revenue would be recognized as revenue at that time.

     In November 2002, the Emerging Issues Task Force (“EITF”), reached a consensus on EITF No. 00-21, ’’Accounting for Revenue Arrangements with Multiple Deliverables,’’ (“EITF No. 00-21”). EITF No. 00-21 provides guidance on how to account for arrangements that involve the delivery or performance of multiple products, services and/or rights to use assets. The provisions of EITF No. 00-21 will apply to revenue arrangements entered into on or after July 1, 2003.

     Government Research Grant Revenue – Government research grants that provide for payments to the Company for work performed are recognized as revenue when the related expense is incurred and the Company has obtained governmental approval to use the grant funds for these expenses.

8

IDENIX PHARMACEUTICALS, INC.

NOTES TO THE CONDENSED CONSOLIDATED FINANCIAL STATEMENTS
(UNAUDITED) — CONTINUED

Stock-Based Compensation

     As permitted by Statement of Financial Accounting Standard (“SFAS”) No. 123, “Accounting for Stock-Based Compensation” (“SFAS No. 123”), the Company accounts for its stock-based awards to employees and directors using the intrinsic method prescribed in Accounting Principles Board Opinion No. 25 (“APB No. 25), “Accounting for Stock Issued to Employees,” and related interpretations. Subsequent changes to option terms can also give rise to compensation expense. The Company recognizes compensation expense for restricted stock sold and stock options granted to nonemployees in accordance with the requirements of SFAS No. 123 and Emerging Issues Task Force (“EITF”) Issue No. 96-18, “Accounting for Equity Instruments that Are Issued to Other than Employees for Acquiring, or in Conjunction with Selling Goods and Services” (“EITF 96-18”). EITF 96-18 requires that such equity instruments be recorded at their fair value at the measurement date, which is generally the vesting date of the instruments. Therefore, the measurement of stock-based compensation is subject to periodic adjustment as the underlying equity instruments vest.

     In December 2002, the Financial Accounting Standards Board (“FASB”) issued SFAS No. 148, “Accounting for Stock-Based Compensation – Transition and Disclosure – An amendment of FAS 123” (“SFAS No. 148”). This statement provides alternative methods of transition for a voluntary change to the fair value method of accounting for stock-based employee compensation. SFAS No. 148 also requires that disclosures of the pro forma effect of using the fair value method of accounting for stock-based compensation be displayed more prominently and in tabular format. Additionally, SFAS No. 148 requires disclosure of the pro forma effect in the interim financial statements. The Company applies the disclosure provisions of SFAS No. 123, as amended by SFAS No. 148, to include pro forma net income (loss) per share information as if the fair value based method of accounting had been used.

     If compensation expense for the Company’s stock-based compensation plan had been determined based on the fair value at the grant dates as calculated in accordance with SFAS No. 123, the Company’s net income (loss) attributable to common stockholders and earnings (loss) per common share would approximate the pro forma amounts below (in thousands, except per share data):

9

IDENIX PHARMACEUTICALS, INC.

NOTES TO THE CONDENSED CONSOLIDATED FINANCIAL STATEMENTS
(UNAUDITED) — CONTINUED

     The assumptions used are as follows:

Basic and Diluted Earnings (Loss) per Common Share

     The Company accounts for and discloses net income (loss) per common share in accordance with SFAS No. 128, “Earnings Per Share” (“SFAS No. 128”). Under the provisions of SFAS No. 128 and Staff Accounting Bulletin (“SAB”) No. 98, basic earnings (loss) per common share is computed by dividing the net income (loss) available to common stockholders by the weighted average number of common shares outstanding during the period. Diluted earnings (loss) per common share is computed by dividing the net income (loss) available to common stockholders by the weighted average number of common shares outstanding during the period plus additional weighted average common equivalent shares outstanding during the period when the effect is not anti-dilutive. Common equivalent shares consist of common shares issuable upon the assumed exercise of outstanding stock options and warrants (using the treasury stock method), issuance of contingently issuable shares subject to Novartis subscription rights (see Note 4), restricted stock awards, and the weighted-average conversion of redeemable convertible preferred stock into shares of common stock (using the if-converted method).

10

IDENIX PHARMACEUTICALS, INC.

NOTES TO THE CONDENSED CONSOLIDATED FINANCIAL STATEMENTS
(UNAUDITED) — CONTINUED

     The following table sets forth the computation of basic and diluted earnings (loss) per common share (in thousands, except per share amounts):

     The following potentially dilutive, common share equivalents were excluded from the calculation of diluted net loss per common share because their effect was anti-dilutive (in thousands):

11

IDENIX PHARMACEUTICALS, INC.

NOTES TO THE CONDENSED CONSOLIDATED FINANCIAL STATEMENTS
(UNAUDITED) — CONTINUED

3. COMPREHENSIVE INCOME (LOSS)

     For the three and six months ended June 30, 2004 and 2003, respectively, comprehensive income (loss) was as follows (in thousands):

4. NOVARTIS RELATIONSHIP

Overview

     In May 2003, the Company entered into a collaboration with Novartis relating to the worldwide development and commercialization of the Company’s drug candidates. Novartis paid the Company a license fee of $75,000,000 for its lead HBV drug candidates, telbivudine and valtorcitabine, has agreed to provide full development funding for these HBV drug candidates and will make milestone payments which could total up to $35,000,000 upon the achievement of regulatory approval milestones, as well as additional milestone payments based upon achievement of predetermined sales levels. Novartis also acquired an option to license the Company’s HCV and other drug candidates. If Novartis exercises its option to collaborate on the Company’s lead HCV drug candidate, NM 283, it would be required to provide full development funding for this drug candidate and pay the Company up to $525,000,000 in license fees and regulatory milestone payments, as well as additional milestone payments based upon achievement of predetermined sales levels. In June 2004, the Company earned and received a $25,000,000 milestone payment from Novartis based upon results from a clinical trial on its lead HCV drug candidate. The Company recognized the milestone payment as revenue in June 2004.

     Simultaneously with the collaboration described above, Novartis purchased, pursuant to a Stock Purchase Agreement (''Stock Purchase Agreement’’), approximately 54% of the Company’s outstanding capital stock from the Company’s stockholders for $255,000,000 in cash, with an additional aggregate amount of up to additional $357,000,000 contingently payable (in cash, or under certain circumstances, American Depository Shares of Novartis AG) to these stockholders if the Company achieves predetermined development milestones relating to an HCV drug candidate.

     To date, the Company has received from Novartis $75,000,000 as a license fee for its HBV drug candidates and a $5,000,000 reimbursement for reacquiring product rights from Sumitomo to develop and commercialize telbivudine in certain markets in Asia. The Company has included this reimbursement as part of the up-front license fee for accounting purposes because Novartis required the repurchase of these rights as a condition of entering into the development agreement. The Company has estimated that the performance period during which the development of the HBV drug candidates and NM 283 will be a period of approximately six and one-half years following the effective date of the development agreement

12