This Quarterly Report on Form 10-Q contains forward-looking statements based on our current expectations. The forward-looking statements are contained principally in this section entitled "Management's Discussion and Analysis of Financial Condition and Results of Operations" and "Risk Factors." Words such as "expect," "anticipate," "target," "goal," "project," "intend," "plan," "could," "should," "might," "believe," "seek," "estimate," "continue," "may," variations of such words and similar expressions are intended to identify such forward-looking statements. In addition, any statements that refer to projections of our future financial performance, our anticipated trends in our businesses and other characterizations of future events or circumstances are forward-looking statements. These statements are not guarantees of future performance and involve risks, uncertainties and assumptions that are difficult to predict. Our actual results may differ materially from those suggested by these forward-looking statements for various reasons, including those identified below under "Risk Factors." Given these risks and uncertainties, you are cautioned not to place undue reliance on forward-looking statements. The forward-looking statements included in this report are made only as of the date hereof. Except as required under federal securities laws and the rules and regulations of the Securities and Exchange Commission, we do not undertake any obligation to update publicly any forward-looking statements after the distribution of this report, whether as a result of new information, future events, changes in assumptions or otherwise. In evaluating our business, you should carefully consider the risks described in the section entitled "Risk Factors" under Part II, Item 1A below, in addition to the other information in this Quarterly Report on Form 10-Q. Any of the risks contained herein could materially and adversely affect our business, results of operations and financial condition.

You should read the following management's discussion and analysis of our financial condition and results of operations in conjunction with our audited Consolidated Financial Statements and related notes thereto included as part of our Annual Report on Form 10-K for the year ended December 31, 2008 and our unaudited Condensed Consolidated Financial Statements for the three months ended March 31, 2009 and other disclosures (including the disclosures under "Part II. Item 1A. Risk Factors") included in this Quarterly Report on Form 10-Q. Our Condensed Consolidated Financial Statements have been prepared in accordance with U.S. generally accepted accounting principles and are presented in U.S. dollars.

Management Overview

We are a biopharmaceutical company that discovers, develops and commercializes innovative therapeutics in areas of unmet medical need. Our mission is to advance the care of patients suffering from life threatening diseases worldwide. Headquartered in Foster City, California, we have operations in North America, Europe and Australia. We market Truvada® (emtricitabine/tenofovir disoproxil fumarate), Atripla® (efavirenz 600 mg/emtricitabine 200 mg/tenofovir disoproxil fumarate 300 mg), Viread® (tenofovir disoproxil fumarate) and Emtriva®
(emtricitabine) for the treatment of human immunodeficiency virus (HIV)
infection; Hepsera® (adefovir dipivoxil) and Viread for the treatment of chronic hepatitis B virus (HBV); AmBisome® (amphotericin B) liposome for injection for the treatment of severe fungal infections; Letairis ® (ambrisentan) for the treatment of pulmonary arterial hypertension (PAH); and Vistide® (cidofovir injection) for the treatment of cytomegalovirus infection. F. Hoffmann-La Roche Ltd (together with Hoffmann-La Roche Inc., Roche) markets Tamiflu® (oseltamivir phosphate) for the treatment and prevention of influenza under a royalty-paying collaborative agreement with us. OSI Pharmaceuticals, Inc. markets Macugen® (pegaptanib sodium injection) in the United States and Europe for the treatment of neovascular age-related macular degeneration under a royalty-paying collaborative agreement with us. GlaxoSmithKline Inc. (GSK) markets Volibris® (ambrisentan) outside of the United States for the treatment of PAH under a royalty-paying collaborative agreement with us.

Business Highlights

In March 2009, we signed an agreement to acquire CV Therapeutics, Inc. (CV Therapeutics) for $20.00 per share. This transaction, valued at approximately $1.4 billion, closed on April 17, 2009, at which time CV Therapeutics became our wholly-owned subsidiary. The results of operations of CV Therapeutics are not

included in our Condensed Consolidated Financial Statements as of and for the three months ended March 31, 2009. CV Therapeutics was a publicly held biopharmaceutical company based in Palo Alto, California, primarily focused on applying molecular cardiology to the discovery, development and commercialization of small molecule drugs for the treatment of cardiovascular diseases. CV Therapeutics has two marketed products as well as several product candidates currently being evaluated for the treatment of atrial fibrillation, pulmonary diseases and diabetes. We believe the acquisition will provide us with an opportunity to further expand into the cardiovascular therapeutic area.

In January 2009, we completed the purchase of an office building and approximately 30 acres of land located in Foster City, California, for an aggregate purchase price of $140.1 million.

With regard to our antiviral research and development (R&D) efforts, in February 2009, we presented the data and results from two Phase 1 studies for GS 9350, our pharmacoenhancer that is in development as a boosting agent for certain HIV medicines. In April 2009, we initiated a Phase 2 study of the complete single-tablet fixed-dose regimen containing elvitegravir, GS 9350 and Truvada in treatment-naïve patients, and anticipate the study to be fully enrolled by the second quarter of 2009.

In the cardiovascular area, in March 2009, we began enrolling patients in a Phase 2 clinical trial of cicletanine hydrochloride, an oral agent in development for the treatment of PAH. In April 2009, we announced preliminary data from DAR-311 (DORADO), a Phase 3 study for darusentan for the treatment of resistant hypertension.

With regard to our respiratory efforts, in February 2009, we received a response from the U.S. Food and Drug Administration (FDA) to our appeal, submitted under the formal dispute resolution process, regarding the agency's complete response letter for our new drug application (NDA) for aztreonam for inhalation solution for the treatment of cystic fibrosis (CF) in the United States. Following its review under the dispute resolution process, the FDA reiterated its position outlined in the complete response letter, including the need for us to conduct an additional clinical study of aztreonam for inhalation solution before we can resubmit our NDA. In March 2009, the Committee for Medicinal Products for Human Use (CHMP), the scientific committee of the European Medicines Agency (EMEA), notified us that it had adopted a negative opinion on our Marketing Authorisation Application (MAA) for aztreonam for inhalation solution for the treatment of CF in the European Union. We are conferring with both regulatory bodies to determine what further studies would be required to address their concerns and support approval of this product.

Financial Highlights

Our operating results for the three months ended March 31, 2009 were led by total product sales of $1.45 billion. Antiviral product sales (Truvada, Atripla, Viread, Hepsera and Emtriva) increased 28% to $1.34 billion in the three months ended March 31, 2009 from the three months ended March 31, 2008, and were the key drivers for total product sales growth of 27% for the three months ended March 31, 2009 as compared to the three months ended March 31, 2008. Atripla contributed $509.9 million, or 38%, to our first quarter 2009 antiviral product sales. The growth of Atripla product sales and its increased proportion relative to our overall product sales caused our product gross margin to decrease to 77.2% for the three months ended March 31, 2009 from 79.0% in the same period of 2008, due primarily to the efavirenz component of Atripla sales which is recorded at zero gross margin. Truvada product sales for the three months ended March 31, 2009 comprised $590.4 million, or 44% of our first quarter 2009 antiviral product sales. Truvada product sales for the three months ended March 31, 2009 increased 23% from the three months ended March 31, 2008 primarily due to continued sales volume growth in the United States and Europe. Foreign currency fluctuations for the three months ended March 31, 2009 had an unfavorable impact of approximately $22.3 million on total revenues and $11.7 million on pre-tax income when compared to the three months ended March 31, 2008.

Royalty, contract and other revenues that we recognized from our collaborations with corporate partners were $82.9 million for the three months ended March 31, 2009, a decrease of 29% from the three months ended

March 31, 2008. The decrease was driven primarily by lower Tamiflu royalties from Roche of $33.2 million for the three months ended March 31, 2009 compared to Tamiflu royalties of $93.4 million in the same period in 2008 due to decreased sales related to pandemic planning initiatives worldwide. This decrease was partially offset by the recognition of approximately $24.0 million of previously deferred collaboration payments from a corporate partner as we no longer have substantive ongoing performance obligations.

Operating expenses which include R&D and selling, general and administrative (SG&A) expenses increased $42.5 million for the three months ended March 31, 2009, or 12%, compared to the three months ended March 31, 2008, reflecting the higher headcount required to support the continued growth of our business as well as the increased research and clinical study activity in our development pipeline. We expect to incur acquisition-related costs in 2009 for the acquisition of CV Therapeutics.

Cash, cash equivalents and marketable securities increased by $369.3 million during the three months ended March 31, 2009, driven primarily by our operating cash flows of $641.3 million, partially offset by repurchases under the $3.00 billion stock repurchase program authorized by our Board of Directors (Board) in October 2007, which expires in December 2010. During the three months ended March 31, 2009, we received an additional 1.4 million shares of our common stock, bringing the total number of shares repurchased and retired under the accelerated share repurchase agreement entered into in October 2008 to 16.2 million shares at an average purchase price of $46.21 per share. In addition, we repurchased a total of $230.0 million of our common stock through open market purchases, or approximately 5.0 million shares. As of March 31, 2009, the remaining authorized amount of stock repurchases that may be made under our Board authorized stock repurchase program was $768.1 million.

Critical Accounting Policies, Estimates and Judgments

There have been no material changes in our critical accounting policies, estimates and judgments during the three months ended March 31, 2009 compared to the disclosures in Part II, Item 7 of our Annual Report on Form 10-K for the year ended December 31, 2008.

Adoption of New Accounting Pronouncements

On January 1, 2009, we adopted the provisions of Financial Accounting Standards Board Staff Position Accounting Principles Board Opinion No. 14-1, Accounting for Convertible Debt Instruments That May Be Settled in Cash upon Conversion (Including Partial Cash Settlement) (FSP APB 14-1) on a retrospective basis for our convertible senior notes. FSP APB 14-1 requires us to account for the liability and equity components of our convertible senior notes separately by bifurcating the conversion option from the debt instrument, classifying the conversion option in equity and then accreting the resulting discount on the debt as additional interest expense over the expected life of the debt. Accordingly, we reflected additional interest expense and a related benefit from income taxes of $12.9 million and $5.1 million, respectively, for the three months ended March 31, 2008 in our Condensed Consolidated Statement of Income, and recorded additional interest expense and a related benefit from income taxes of $13.6 million and $5.3 million, respectively, for the three months ended March 31, 2009. In addition, the retrospective adoption of FSP APB 14-1 decreased deferred tax assets and debt issuance costs included in other assets by an aggregate of $81.7 million, decreased convertible senior notes, net included in long-term liabilities by $201.8 million, and increased total stockholders' equity by $120.1 million after a charge of $82.6 million to retained earnings on our Condensed Consolidated Balance Sheet as of December 31, 2008.

On January 1, 2009, we adopted the provisions of Statement of Financial Accounting Standards (SFAS) No. 160, Noncontrolling Interests in Consolidated Financial Statements, an amendment of Accounting Research Bulletin No. 51, Consolidated Financial Statements (SFAS 160). Accordingly, we reclassified the noncontrolling interest (formerly minority interest) from liabilities to stockholders' equity on our Condensed Consolidated Balance Sheets on a retrospective basis, which resulted in the reclassification of the change in noncontrolling

interest from net cash provided by operating activities to net cash used in financing activities on our Condensed Consolidated Statements of Cash Flows. We also presented the noncontrolling interest on our Condensed Consolidated Statements of Income as net loss attributable to noncontrolling interest, a component of consolidated net income, on a retrospective basis.

Results of Operations

Total Revenues

We had total revenues of $1.53 billion for the three months ended March 31, 2009 compared to $1.26 billion for the same period in 2008. Included in total revenues were product sales, royalty revenues and contract and other revenues.

Product Sales

The following table summarizes the period over period changes in our product
sales (in thousands):



                                           Three Months Ended
                                                March 31,
                                           2009          2008       Change
             Antiviral products:
             Truvada                    $   590,353   $   479,385      23%
             Atripla                        509,883       324,217      57%
             Viread                         160,605       152,667       5%
             Hepsera                         72,714        83,022    (12)%
             Emtriva                          7,234         8,389    (14)%

             Total antiviral products     1,340,789     1,047,680      28%
             AmBisome                        64,271        71,028    (10)%
             Letairis                        39,580        20,337      95%
             Other                            2,940         2,261      30%

             Total product sales        $ 1,447,580   $ 1,141,306      27%

Total product sales increased by 27% for the three months ended March 31, 2009 compared to the same period in 2008, due primarily to an overall increase in our antiviral product sales, including the strong growth in sales of Atripla and Truvada. A significant percentage of our product sales continued to be denominated in foreign currencies. We used foreign currency exchange forward and option contracts to hedge a percentage of our forecasted international sales, primarily those denominated in Euro. This reduced, but did not eliminate, fluctuations in sales due to changes in foreign currency exchange rates.

Antiviral Products

Antiviral product sales increased by 28% for the three months ended March 31, 2009 compared to the same period in 2008, driven primarily by sales volume growth of Atripla and Truvada.

• Truvada

Truvada sales increased by 23% for the three months ended March 31, 2009 compared to the same period in 2008, driven primarily by sales volume growth in the United States and Europe. Truvada sales accounted for 44% of our total antiviral product sales for the three months ended March 31, 2009.

• Atripla

Atripla sales increased by 57% for the three months ended March 31, 2009 compared to the same period in 2008, driven primarily by its continued uptake in the United States and Europe. We consolidate 100% of Atripla product sales because we are the primary beneficiary of our joint venture with Bristol-Myers Squibb Company (BMS) in the United States. Outside of the United States, we also

recognize 100% of Atripla product sales. The efavirenz portion of our Atripla sales was approximately $187.5 million and $119.6 million for the three months ended March 31, 2009 and 2008, respectively. Atripla sales accounted for 38% of our total antiviral product sales for the three months ended March 31, 2009.

• Other Antiviral Products

Other antiviral product sales, which include product sales of Viread, Hepsera and Emtriva, decreased by 1% for the three months ended March 31, 2009 compared to the same period in 2008, driven primarily by increased Viread sales volume growth, offset by sales volume decreases in Hepsera product sales.

Letairis

Sales of Letairis for the treatment of PAH increased 95% for the three months ended March 31, 2009 compared to the same period in 2008, driven primarily by sales volume growth in the United States.

Royalty Revenues

The following table summarizes the period over period change in our royalty revenues (in thousands):

Three Months Ended March 31, 2009 2008 Change Royalty revenues $ 53,042 $ 109,452 (52)%

Our most significant source of royalty revenues for the three months ended March 31, 2009 and 2008 was from sales of Tamiflu by Roche.

Royalty revenues for the three months ended March 31, 2009 were $53.0 million, a decrease of 52% compared to the same period in 2008, driven primarily by the recognition of Tamiflu royalties from Roche of $33.2 million in the three months ended March 31, 2009 compared to Tamiflu royalties from Roche of $93.4 million recognized in the same period in 2008. The lower Tamiflu royalties were due primarily to decreased Roche sales related to pandemic planning initiatives worldwide. We recognize royalties on Tamiflu sales by Roche in the quarter following the quarter in which Tamiflu is sold.

Cost of Goods Sold and Product Gross Margin

The following table summarizes the period over period changes in our total
product sales (in thousands), cost of goods sold (in thousands) and product
gross margin:



                                         Three Months Ended
                                              March 31,
                                         2009          2008       Change
               Total product sales    $ 1,447,580   $ 1,141,306      27%
               Cost of goods sold     $   329,414   $   239,848      37%
               Product gross margin         77.2%         79.0%

Our product gross margin for the three months ended March 31, 2009 was 77.2%, compared to 79.0% for the same period in 2008. The decrease in our product gross margin was due primarily to the higher proportion of Atripla sales, which include the efavirenz component at zero product gross margin.

A higher mix of Atripla product sales decreases our overall product gross margin. Although we record 100% of Atripla product sales, we only benefit from the product gross margin on the Truvada portion of Atripla sales. The efavirenz portion of Atripla sales carries a zero product gross profit and gross margin since we purchase efavirenz from BMS at BMS's net selling price of efavirenz.

Research and Development Expenses

The following table summarizes the period over period change in the major
components of our R&D expenses (in thousands):



                                               Three Months Ended
                                                   March 31,
                                                2009        2008      Change
            Research                         $   43,998   $  34,509      27%
            Clinical development                115,072      94,768      21%
            Pharmaceutical development           29,709      26,024      14%

            Total research and development   $  188,779   $ 155,301      22%

R&D expenses consist primarily of personnel costs, including salaries, benefits and stock-based compensation, clinical studies performed by contract research organizations, materials and supplies, license fees and overhead allocations consisting of various support and facilities related costs. Our R&D activities are separated into three main categories: research, clinical development and pharmaceutical development. Research costs typically consist of preclinical and toxicology costs. Clinical development costs include costs for Phase 1, 2, 3 and 4 clinical trials. Pharmaceutical development expenses consist of costs for product formulation and chemical analysis.

R&D expenses for the three months ended March 31, 2009 increased by $33.5 million, or 22%, compared to the same period in 2008, due primarily to increased compensation and benefit expenses of $13.8 million due largely to higher headcount, as well as increased clinical study expenses of $10.0 million driven primarily by the growth in our business.

Selling, General and Administrative Expenses

The following summarizes the period over period change in our SG&A expenses (in thousands):

Three Months Ended March 31, 2009 2008 Change Selling, general and administrative $ 203,951 $ 194,957 5%

SG&A expenses for the three months ended March 31, 2009 increased by $9.0 million, or 5%, compared to the same period in 2008, due primarily to increased compensation and benefit expenses of $12.6 million driven largely by higher headcount.

Purchased In-process Research and Development Expenses

In connection with our acquisitions of Myogen Inc. (Myogen) and Corus Pharma, Inc. (Corus) in 2006, we recorded purchased in-process research and development (IPR&D) expenses of $2.06 billion and $335.6 million, respectively, during the year ended December 31, 2006.

The purchased IPR&D expense for Myogen represented the estimated fair value of Myogen's incomplete R&D programs that had not yet reached technological feasibility and had no alternative future uses as of the acquisition date and, therefore, was expensed upon acquisition. A summary of these programs at the acquisition date, updated for subsequent changes in status of development, is as follows:

                                                                                Estimated
                                                                            Acquisition Date
                                                                               Fair Value
  Program              Description              Status of Development         (in millions)
Ambrisentan     An orally active,             Phase 3 clinical trials       $         1,413.7
                non-sulfonamide,              were completed prior to
                propanoic acid-class,         the acquisition date. We
                endothelin receptor           filed an NDA with the FDA
                antagonist (ERA) for the      in December 2006 and, in
                treatment of PAH.             June 2007, the FDA
                                              approved Letairis for the
                                              treatment of PAH in the
                                              United States.
                                              Additionally, in March
                                              2007, the EMEA validated
                                              the marketing
                                              authorization application
                                              for ambrisentan for the
                                              treatment of PAH, filed
                                              by our collaboration
                                              partner, GSK. In April
                                              2008, the European
                                              Commission granted GSK
                                              marketing authorization
                                              for ambrisentan for the
                                              treatment of PAH, which
                                              is marketed under the
                                              name Volibris by GSK.

Darusentan      An orally active              In Phase 3 clinical           $           644.5
                ETA-selective ERA for the     development as of the
                treatment of resistant        acquisition date and the
                hypertension.                 date of this filing.

The remaining efforts for completing the darusentan IPR&D program consist primarily of clinical trials, the cost, length and success of which are extremely difficult to predict, and obtaining necessary regulatory approvals. Numerous risks and uncertainties exist that could prevent completion of development, including the possibility of unfavorable results of our clinical trials and the risk of failing to obtain FDA and other regulatory body approvals. Feedback from regulatory authorities or results from clinical trials might require modifications to or delays in later stage clinical trials or additional trials to be performed. We cannot be certain that darusentan for the treatment of resistant hypertension will be approved in the United States or in countries outside of the United States or whether marketing approvals will have significant limitations on its use. Future discussions with regulatory agencies will determine the amount of data needed and timelines for review, which may differ materially from current projections. Darusentan may never be successfully commercialized. As a result, we may make a strategic decision to discontinue development of darusentan if, for example, we believe commercialization will be difficult relative to other opportunities in our pipeline. If this program cannot be completed on a timely basis or at all, then our prospects for future revenue growth may be adversely impacted. No assurance can be given that the underlying assumptions used to forecast the above cash flows or the timely and successful completion of this project will materialize as estimated. For these reasons, among others, actual results may vary significantly from estimated results.

. . .