Overview

We are in the business of discovering, developing, manufacturing and commercializing small molecule drugs for the treatment of serious diseases. Our two products are INCIVEK™ (telaprevir), which is approved in the United States and Canada for the treatment of adults with genotype 1 hepatitis C virus, or HCV, infection, and KALYDECO™ (ivacaftor), which is approved in the United States and European Union for the treatment of patients six years of age or older with cystic fibrosis, or CF, who have a specific mutation that is referred to as the G551D mutation. Our collaborator, Janssen Pharmaceutica, N.V., or Janssen, markets telaprevir in Europe and its other territories under the brand name INCIVO™, and our collaborator, Mitsubishi Tanabe Pharma Corporation, or Mitsubishi Tanabe, markets telaprevir in Japan under the brand name TELAVIC™. We obtained approval to market KALYDECO in the United States in January 2012 and in the European Union in July 2012.

As of June 30, 2012, we had cash, cash equivalents and marketable securities, excluding Alios' cash and cash equivalents, of $1.2 billion. In the first and second quarters of 2012, we had net product revenues of $375.4 million and $373.3 million, respectively. Our net product revenues from INCIVEK and KALYDECO were $327.7 million and $45.5 million, respectively, in the second quarter of 2012. The slight decrease in total net product revenues in the second quarter of 2012 as compared to the first quarter of 2012 was the result of a decrease in INCIVEK net product revenues offset by an increase in KALYDECO net product revenues. We expect these trends to continue with KALYDECO revenues increasing as a result of its recent approval in the European Union and INCIVEK revenues decreasing in future periods. Although our net product revenues in the second quarter of 2012 were similar to our net product revenues in the first quarter of 2012, we incurred a net loss attributable to us in the second quarter of 2012 of $(64.9) million as compared to net income attributable to us in the first quarter of 2012 of $91.6 million because we incurred two significant charges in the second quarter of 2012. These charges were $78.0 million related to excess and obsolete INCIVEK inventories, and $56.2 million related to an increase in the fair market value of our liabilities pursuant to our Alios collaboration due to positive clinical data we received from a Phase 1 clinical trial evaluating ALS-2200.

We believe that our long-term success will depend on our ability to continue to generate and develop innovative molecules for the treatment of serious diseases. We have ongoing clinical programs involving drug candidates intended for the treatment of HCV infection, CF, rheumatoid arthritis, epilepsy and influenza. Our HCV clinical programs are focused on fulfilling INCIVEK post-marketing commitments to regulatory agencies and on developing all-oral, interferon-free combinations of HCV drugs and drug candidates that have the potential to further improve treatment options available to patients with HCV infection. In July 2012, we announced positive data from a Phase 1 clinical trial evaluating ALS-2200's activity against genotype 1 HCV infection over a seven-day dosing period. In this clinical trial, there was a median 4.54 log10 reduction in HCV RNA levels in eight treatment-naïve patients after seven days of dosing with 200 mg of ALS-2200 once daily. ALS-2200 was well-tolerated and no patients discontinued due to adverse events. Based on these results, we plan to initiate Phase 2 clinical trials in 2012 to evaluate 12-week all-oral regimens including ALS-2200 in patients with genotype 1 HCV infection, pending discussions with regulatory agencies. In our CF program, we are investigating the use of KALYDECO as a monotherapy in additional populations of patients with CF, and combinations of KALYDECO and our other CF drug candidates, with the goal of expanding the group of patients with CF who can benefit from our medicines. In June 2012, we announced final data from Part 2 of a Phase 2 clinical trial of VX-809 in combination with KALYDECO. We plan to initiate a pivotal clinical program to evaluate KALYDECO in combination with VX-809 in CF patients with two copies of the F508del mutation in the cystic fibrosis transmembrane conductance regulatory, or CFTR, gene, pending discussions with regulatory agencies. We expect to continue investing in research

programs directed toward the identification of new drug candidates and to develop and commercialize selected drug candidates that emerge from those programs, alone or with third-party collaborators.

Competition

HCV

The field of HCV infection treatment is highly competitive and characterized by rapid technological advances. We and Janssen are competing with Merck & Co., Inc.'s VICTRELIS™ (boceprevir), another HCV protease inhibitor that was approved for sale in the United States and Europe in 2011. Increased competition from currently approved drugs, the introduction of new competitive drugs or drug combinations, adverse information regarding the safety characteristics or efficacy of the drug, significant new information regarding potential future treatment regimens that are being evaluated in clinical trials or enrollment by patients in clinical trials being conducted by us or our competitors could result in abrupt shifts in the HCV market. Several of our competitors are conducting Phase 3 clinical trials evaluating their drug candidates for the treatment of genotype 1 HCV infection. For example, Janssen is evaluating an HCV protease inhibitor, TMC-435, in combination with pegylated-interferon, or peg-IFN, and ribavirin in Phase 3 clinical trials that were initiated in early 2011, and Gilead Sciences, Inc., or Gilead, initiated a Phase 3 clinical trial in June 2012 to evaluate its HCV nucleotide analogue, GS-7977, in combination with peg-IFN and ribavirin. We believe that final data from these Phase 3 clinical trials may become available within the next twelve months and that, if approved, these drugs will compete directly with INCIVEK.

We, along with a number of our competitors, are pursuing development programs involving all-oral combinations of HCV drugs and drug candidates with the goal of developing improved treatment regimens for HCV infection that could render current and future treatment regimens that include the administration of peg-IFN by injection uncompetitive. In particular, we and our competitors, Abbott Laboratories, Bristol-Myers Squibb Company and Gilead, are actively pursuing development of all-oral combination treatment regimens to treat HCV infection. To date, potential all-oral combination treatment regimens have been evaluated in Phase 2 clinical trials involving relatively small numbers of patients. However, we expect that one or more of our competitors may begin registration programs evaluating potential all-oral combination regimens for the treatment of genotype 1 HCV infection in the second half of 2012. While the development and regulatory timelines for these drug candidates are subject to risk and uncertainty, we believe that substantial additional clinical data regarding these drug candidates and potential all-oral treatment regimens will become available in 2012 and 2013 and that one or more all-oral treatment regimens could be commercially available as early as 2014.

CF

KALYDECO (ivacaftor) is approved in the United States and the European Union for the treatment of patients with CF six years of age or older who have the G551D mutation on at least one allele of the CFTR gene. We are focused on continuing our launch of KALYDECO in the United States and launching KALYDECO in Europe. KALYDECO has received Priority Review from the Therapeutic Product Directorate of Health Canada, and we have submitted a marketing authorization application for KALYDECO to the Therapeutic Goods Administration of Australia. We recently initiated two Phase 3 clinical trials to evaluate KALYDECO as a monotherapy in CF patients with mutations other than the G551D mutation, and are planning a Phase 3 clinical trial of KALYDECO as a monotherapy in CF patients two to five years of age who have a gating mutation in the CFTR gene. If these clinical trials are successful, we expect we would obtain approval for the use of KALYDECO in additional populations in 2013 or later.

We are aware of several companies that are engaged in researching and/or developing treatments for CF, including Genzyme Corporation, which has a research program directed at identifying CFTR

corrector compounds. We believe that the programs that could result in drugs that are directly competitive with KALYDECO or the combination treatment regimens that we are developing are several years behind our programs.

In addition to the factors described above, approved drugs continue to be subject to, among other things, numerous regulatory risks, post-approval safety monitoring and risks related to supply chain disruptions.

Drug Development

Discovery and development of a new pharmaceutical product is a difficult and lengthy process that requires significant financial resources along with extensive technical and regulatory expertise and can take 10 to 15 years or more. Potential drug candidates are subjected to rigorous evaluations, driven in part by stringent regulatory considerations, designed to generate information concerning efficacy, side-effects, proper dosage levels and a variety of other physical and chemical characteristics that are important in determining whether a drug candidate should be approved for marketing as a pharmaceutical product. Most chemical compounds that are investigated as potential drug candidates never progress into development, and most drug candidates that do advance into development never receive marketing approval. We cannot predict whether or not we will encounter problems with any of our completed, ongoing or planned clinical trials that could cause us or regulatory authorities to delay or suspend the clinical trial. Because our investments in drug candidates are subject to considerable risks, we closely monitor the results of our discovery research, clinical trials and nonclinical studies, and frequently evaluate our drug development programs in light of new data and scientific, business and commercial insights, with the objective of balancing risk and potential. This process can result in relatively abrupt changes in focus and priority as new information becomes available and we gain additional understanding of our ongoing programs and potential new programs, as well as our competitors' programs.

If we believe the data from a completed registration program support approval of a drug candidate, we submit a New Drug Application, or NDA, to the United States Food and Drug Administration, or FDA, requesting approval to market the drug candidate in the United States. We also may seek analogous approvals from comparable regulatory authorities in foreign jurisdictions, such as a marketing authorization in the European Union. To obtain approval, we must, among other things, demonstrate with evidence gathered in nonclinical studies and well-controlled clinical trials that the drug candidate is safe and effective for the disease it is intended to treat and that the manufacturing facilities, processes and controls for the manufacture of the drug candidate are adequate. The FDA and foreign regulatory authorities have substantial discretion in deciding whether or not a drug candidate should be granted approval based on the benefits and risks of the drug candidate in the treatment of a particular disease, and could delay, limit or deny regulatory approval. If regulatory delays are significant or regulatory approval is limited or denied altogether, our financial results and the commercial prospects for the drug candidate involved will be harmed.

Drug Supply and INCIVEK Inventory Write-down

We rely on an international network of third parties to manufacture and distribute our products and for supplies of compounds for clinical trials, and we expect that we will continue to rely on third parties to provide these manufacturing services for the foreseeable future. Third-party contract manufacturers, including some in China, supply us with raw materials, and contract manufacturers in the European Union and the United States convert these raw materials into drug substance and convert the drug substance into final dosage form. Establishing and managing this global supply chain requires a significant financial commitment and the creation and maintenance of numerous third-party relationships. Although we believe we effectively manage the business relationships with companies in our supply chain, we do not have complete control over their activities. Also, we have limited flexibility

to adjust our supply of INCIVEK in response to changes in demand, due to the significant lead times required to manufacture INCIVEK.

In the second quarter of 2012, following a periodic assessment of the recoverability of capitalized costs, we recorded within cost of product revenues a $78.0 million charge for excess and obsolete INCIVEK inventories. Periodic assessments of the recoverability of capitalized costs involve significant estimates and judgments on the part of management. The charge and corresponding inventory write-down were based on our analysis of our INCIVEK inventory levels in relation to our commercial outlook for INCIVEK. As part of the analysis, we considered, among other factors, (i) recent decreases in demand for INCIVEK and our expectation the demand will decrease further in the second half of 2012,
(ii) the potential development by us and our competitors of other drugs and combination treatments for HCV infection, (iii) positive results released in the second quarter of 2012 from Phase 2 clinical trials of drug candidates being developed by our competitors and (iv) the recent initiation by our competitors of a number of additional Phase 2 and Phase 3 clinical trials of drug candidates for the treatment of HCV infection. We will continue to evaluate our INCIVEK inventories on a quarterly basis, and future changes in the outlook for commercial sales of INCIVEK, including changes due to future developments with respect to demand for INCIVEK or the advancement or approval of other drugs or combination treatments for HCV infection, could result in additional inventory write-downs and related charges in future periods.

Regulatory Compliance

Our marketing of pharmaceutical products, which began in May 2011, is subject to extensive and complex laws and regulations. We have a corporate compliance program designed to promote a culture of compliance and to actively identify, prevent and mitigate risk. Among other laws, regulations and standards, we are subject to various U.S. federal and state laws and comparable foreign laws pertaining to health care fraud and abuse, including anti-kickback and false claims statutes, and laws prohibiting the promotion of drugs for unapproved, or off-label, uses. Anti-kickback laws make it illegal for a prescription drug manufacturer to solicit, offer, receive or pay any remuneration in exchange for, or to induce, the referral of business, including the purchase or prescription of a particular drug. False claims laws prohibit anyone from presenting for payment to third-party payors, including Medicare and Medicaid, claims for reimbursed drugs or services that are false or fraudulent, claims for items or services not provided as claimed or claims for medically unnecessary items or services. We expect to continue to devote substantial resources to maintain, administer and expand these compliance programs globally.

Recent Developments

CF

KALYDECO-Phase 3 Clinical Trials of KALYDECO Monotherapy

In June 2012, we initiated a Phase 3 clinical trial to evaluate KALYDECO monotherapy in patients six years of age and older who have the R117H mutation on at least one allele of the CFTR gene. In July 2012, we initiated a Phase 3 clinical trial to evaluate KALYDECO monotherapy in patients six years of age and older with non-G551D gating mutations in the CFTR gene. In the second half of 2012, we plan to initiate a Phase 3 clinical trial to evaluate KALYDECO monotherapy in patients ages two to five years old with a gating mutation on at least one allele of the CFTR gene.

VX-809/KALYDECO-Phase 2 Clinical Trial

In June 2012, we announced the final data from Part 2 of a Phase 2 clinical trial of VX-809 and KALYDECO. This part of the clinical trial enrolled 109 people with CF ages 18 years and older with one (heterozygous) or two (homozygous) copies of the F508del mutation in the CFTR gene, who were

divided into five treatment groups of approximately 20 patients each. Three groups of homozygous patients were randomized to receive VX-809 alone (200mg, 400mg or 600mg) for 28 days and then in combination with KALYDECO (250mg) for an additional 28 days. One group of heterozygous patients received VX-809 alone
(600mg) for 28 days and then in combination with KALYDECO (250mg) for an additional 28 days. The placebo group included both homozygous and heterozygous patients.

The data from this Phase 2 clinical trial of VX-809 and KALYDECO showed statistically significant improvements in lung function, percent predicted forced expiratory volume in one second, or FEV1, in each of the homozygous treatment groups compared to placebo from Day 28 to Day 56. The greatest improvements in lung function were observed in patients who received 600mg of VX-809, the highest dose evaluated in this clinical trial, in combination with KALYDECO. Most adverse events observed during the 56-day clinical trial were mild to moderate in severity across all treatment groups and similar between treatment and placebo groups. We are preparing to initiate a pivotal clinical trial program, which is expected to evaluate VX-809 (600mg) in combination with KALYDECO (250mg) in homozygous patients and begin in early 2013, pending discussions with regulatory agencies.

     Lung Function

    Homozygous patients treated with the highest dose of VX-809 (600mg) in
combination with KALYDECO from Day 28 to Day 56 experienced a mean absolute
improvement in lung function of 8.6 percentage points compared to placebo
(p<0.001) and a mean absolute improvement of 6.1 percentage points within group
(p<0.001). The following table sets forth the mean absolute change in percent
predicted FEV1 for homozygous patients who received the highest dose of VX-809
and patients for the placebo treatment arm:

                                                      Day 0 to Day    Day 28 to Day
                                                           28               56
Placebo, including homozygous and heterozygous
patients, within group                                -0.9 (p=0.54)   -2.5 (p=0.08)
VX-809 alone (600mg; QD) for 28 days followed by
the addition of KALYDECO (250mg, q12h) for 28 days
within group                                          -2.9 (p=0.07)   +6.1 (p<0.001)
VX-809 alone (600mg; QD) for 28 days followed by
the addition of KALYDECO (250mg, q12h) for 28 days
compared to placebo                                   -2.0 (p=0.36)   +8.6 (p<0.001)

The following table sets forth the percentage of patients who received the highest dose of VX-809 and percentage of patients in the placebo group who experienced absolute improvements in lung function of 5 percentage points or more and 10 percentage points or more during the periods from Day 0 to Day 28 and from Day 28 to Day 56:

                                    Day 0 to Day 28               Day 28 to Day 56
                                                                              VX-809
                                                                           (600mg) and
                                            VX-809 (600mg)                   KALYDECO
                               Placebo       monotherapy       Placebo       (250mg)
† 5 percentage point                                                          55.0%
absolute improvement FEV1    13.0% (3/23)    10.0% (2/20)    9.5% (2/21)     (11/20)
† 10 percentage point
absolute improvement FEV1    4.3% (1/23)     5.0% (1/20)     0.0% (0/21)   25.0% (5/20)

From Day 0 to Day 56, patients receiving VX-809 (600mg) and KALYDECO experienced a mean absolute improvement in lung function of 6.7 percentage points compared to placebo (p=0.002) and a 3.4 percentage point improvement within group (p=0.03). Patients receiving placebo experienced a mean absolute decline in lung function of 3.3 percentage points (p=0.03) over the same time period.

The two primary endpoints in this clinical trial were safety and change in sweat chloride from Day 28 to Day 56 compared to placebo. Although not a clinically validated endpoint, a reduction in sweat chloride is considered to be a biomarker of improved CFTR function in the skin. There was no decrease in sweat chloride among those receiving placebo from Day 0 to Day 28 or from Day 28 to Day 56. In homozygous patients treated with 600mg of VX-809 alone for 28 days, there was a statistically significant mean decrease in sweat chloride of 6.4 mmol/L compared to placebo (p=0.01). In these patients, an additional mean decrease in sweat chloride of 3.7 mmol/L compared to placebo was observed with combination treatment between Day 28 and Day 56, which was not statistically significant.

A statistically significant reduction in sweat chloride was observed from Day 0 to Day 28 in homozygous patients treated with VX-809 (200mg, 400mg) alone compared to patients who received placebo, and additional reductions in sweat chloride were observed with the combination treatment between Day 28 and Day 56, but these reductions were not statistically significant.

Heterozygous patients

In heterozygous patients who received 600mg of VX-809 in combination with KALYDECO, there was a mean absolute improvement in lung function from Day 28 to Day 56 compared to placebo. This improvement in lung function was smaller than the improvement seen in homozygous patients receiving 600mg of VX-809 in combination with KALYDECO. Based on these data, we plan to conduct additional clinical studies of VX-809 and KALYDECO in heterozygous patients.

VX-809 was generally well tolerated alone and in combination with KALYDECO. The most common adverse events were pulmonary in nature. Most adverse events were mild to moderate in severity and similar between treatment and placebo groups. The rate of serious adverse events was also similar between treatment and placebo groups.

VX-661/KALYDECO

A Phase 2 clinical trial of VX-661, a second CFTR corrector being evaluated in combination with KALYDECO for patients with CF homozygous for the F508del mutation, is ongoing, with final data expected in 2013.

HCV

Alios Nucleotide Analogues

In July 2012, we announced positive results from a Phase 1 clinical trial that evaluated the safety and tolerability of single ascending doses of ALS-2200 in healthy volunteers, and the safety, tolerability and effects on viral kinetics of multiple ascending doses of ALS-2200 in treatment-naïve patients with genotype 1 HCV infection. In this clinical trial, patients with HCV infection dosed with ALS-2200 had a dose-dependent, consistent and rapid decline in HCV RNA levels. In the treatment group in which patients with genotype 1 HCV infection received seven days of dosing with 200 mg of ALS-2200 once

daily, there was a median 4.54 log10 reduction in HCV RNA levels at the end of the dosing period. The results from each of the dose groups in this clinical trial are included in the following table:

                                                        Median Change     Median Change
                                          Median        From Baseline     From Baseline
                                         Baseline      After 3 Days of   After 7 Days of
                                      HCV RNA levels      Treatment         Treatment
                        Number of     (Log10 IU/mL)     (Log10 IU/mL)     (Log10 IU/mL)
Dose Group             Patients(1)      (Min, Max)       (Min, Max)        (Min, Max)
Placebo                           8        6.30             0.13              0.11
                                       (5.70, 6.90)     (-0.34, 1.22)     (-0.28, 0.66)
ALS-2200 alone
(15mg; once                                6.11             -0.49             -0.97
daily) for seven
days                              8    (5.46, 7.00)    (-0.20, -0.99)    (-0.17, -1.59)
ALS-2200 alone
(50mg; once                                6.19             -1.83             -3.02
daily) for seven
days                              8    (5.73, 7.21)    (-1.41, -2.20)    (-2.21, -3.57)
ALS-2200 alone
(100mg; once                               6.49             -2.60             -3.95
daily) for seven
days(2)                           8    (5.67, 7.00)    (-1.81, -3.78)    (-3.39, -4.51)
ALS-2200 alone
(200mg; once                               6.18             -3.85             -4.54
daily) for seven
days(3)                           8    (5.66, 6.72)    (-2.87, -4.17)    (-3.81, -5.08)


--------------------------------------------------------------------------------
   º (1)

º (2)
º One patient had an HCV RNA level below the limit of detection (Roche COBAS Taqman HCV test, Version 2) during the clinical trial.

º (3)
º Four patients had HCV RNA levels below the limit of quantification (<LOQ = < 25 IU/mL) during the clinical trial.

In this clinical trial, ALS-2200 was well-tolerated. There were no serious adverse events observed in patients dosed with ALS-2200 and no patients discontinued due to adverse events.

Based on these results, we plan to initiate Phase 2 clinical trials in 2012 to evaluate 12-week all-oral regimens incorporating ALS-2200 in patients with genotype 1 HCV infection, pending discussions with regulatory agencies. We expect these Phase 2 clinical trials to include a clinical trial evaluating ALS-2200 in combination with INCIVEK and a clinical trial evaluating ALS-2200 in combination with ribavirin.

We also are conducting a Phase 1 clinical trial to evaluate the safety, tolerability and effects on viral kinetics of ALS-2158, a second HCV nucleotide analogue that we are developing in collaboration with Alios. Data from this Phase 1 clinical trial are expected in the next few months.

INCIVEK

We have an ongoing pivotal clinical trial evaluating whether treatment with INCIVEK can be effectively reduced to twice-daily (BID) dosing instead of three-times-daily dosing. We expect to obtain data from this clinical trial in the second half of 2012 and, if supported by the data, plan to submit this revised dosing schedule to the FDA as part of a supplemental NDA. To fulfill post-marketing commitments, we also have several additional clinical trials ongoing to evaluate patients co-infected with HCV and HIV, patients with . . .