On October 28, 2009 and October 31, 2009, we announced data from two clinical trials of telaprevir. We announced data, including sustained viral response or SVR data, from a completed clinical trial, referred to as the C208 Trial, designed to explore the safety and antiviral activity of twice-daily-every twelve hours-dosing regimens of telaprevir compared with three times daily-every eight hours-dosing. We also announced interim data from a clinical trial, referred to as the 107 Trial, in patients who did not achieve an SVR in the control arms of the PROVE 1, PROVE 2 or PROVE 3 clinical trials.

The C208 trial was an exploratory open-label clinical trial that enrolled 161 treatment-naïve patients infected with genotype 1 HCV. The purpose of the C208 trial was to compare twice-daily dosing regimens of telaprevir-1,125 mg every 12 hours-in combination with pegylated-interferon, or peg-IFN, and ribavirin, or RBV, with three-times daily dosing regimens-750 mg every 8 hours-in combination with peg-IFN and RBV. A three-times daily dosing regimen is being used in the ongoing registration program for telaprevir and has been used in the other clinical trials for telaprevir.

Patients received telaprevir, peg-IFN and RBV for 12 weeks followed by an additional 12 or 36 weeks of peg-IFN and RBV alone in a response-guided trial design. Patients who achieved undetectable HCV RNA-<25 IU/mL, undetectable per Roche COBAS TaqMan HCV test- at week 4, which is referred to as a rapid viral response, or RVR, and who maintained undetectable HCV RNA through week 20, were able to stop all treatment after 24 weeks. Patients who did not meet the response-guided criteria received a total of 48 weeks of peg-IFN and RBV therapy. 18% of patients across the treatment arms were required to continue treatment for 48 weeks.

The following table summarizes the RVR and SVR data on an intent-to-treat basis from the C208 trial.

                                                                           RVR                 SVR
                                                         Total       (undetectable at    (undetectable 24
                                                        Number          week 4 on        weeks after end-
Telaprevir Dosing            Combination Therapy      of Patients       treatment)         of-treatment
1,125 mg every 12 hours     alfa-2a (PEGASYS)/RBV         40           83%  (n=33)         83%  (n=33)

1,125 mg every 12 hours    Alfa-2b (PEGINTRON)/RBV        39           67%  (n=26)         82%  (n=32)

750 mg every 8 hours        alfa-2a (PEGASYS)/RBV         40           80%  (n=32)         85%  (n=34)

750 mg every 8 hours       Alfa-2b (PEGINTRON)/RBV        42           69%  (n=29)         81%  (n=34)

The frequency and severity of adverse events and the rate of treatment discontinuations were similar to those reported in prior telaprevir trials. The most common adverse events reported in patients in this clinical trial were pruritis, nausea, rash, anemia, flu-like illness, fatigue and headache, and the adverse events were similar overall between the patient groups receiving three-times daily dosing and those receiving twice-daily dosing. Serious adverse events leading to permanent treatment discontinuation of all drugs occurred in 5% of patients (8 out 161) and were mainly related to rash (3%, 4/161) and anemia (2%, 3/161).

107 Trial

In the open-label 107 Trial, treatment-experienced patients with genotype 1 HCV were treated with telaprevir triple combination therapy for 12 weeks followed by 12 or 36 weeks of treatment with peg-IFN and RBV alone. In 2008, the protocol for the 107 Trial underwent several amendments, including important amendments that affected prior null-responders.

For the 107 Trial, patients were classified as prior null responders, prior partial responders, prior relapsers and prior viral breakthrough patients based on their response to treatment with peg-IFN and RBV alone in our Phase 2b clinical trials. Patients who had not achieved at least a 1 log10 decrease in HCV RNA levels at week 4 and at least a 2 log10 decrease in HCV RNA levels at week 12 with previous treatment were classified as prior null-responders; patients who had more than a 2 log10 decrease in HCV RNA levels at week 12, but who had detectable HCV RNA levels at week 24 were classified as prior partial responders; patients who had undetectable HCV RNA at the end of treatment with peg-IFN and RBV but subsequently relapsed were classified as prior relapsers; and patients who achieved undetectable HCV RNA but relapsed before the end-of-treatment were classified as prior viral breakthroughs. A 1 log10 decrease represents a 90% decrease in HCV RNA levels, and a 2 log10 represents a 99% decrease in HCV RNA levels.

The table below sets forth the interim data from 94 of the 117 patients enrolled in the 107 Trial, including SVR data and the percentage of patients who had undetectable HCV RNA levels at the end-of-treatment and remained undetectable through 24 weeks after the end-of-treatment.

                                                                        Viral Relapse
Patient Group               Treatment Regimen                 SVR           Rates
Prior Null         telaprevir triple combination for 12   57% (16/28)    20% (4/20)
Responders         weeks, followed by peg-IFN and RBV
                   alone for 36 weeks

Prior Partial      25 patients treated with telaprevir    55% (16/29)    22% (5/23)
Responders         triple combination therapy for 12
                   weeks, followed by peg-IFN and RBV
                   alone for 12 weeks
                   3 patients treated with telaprevir
                   triple combination therapy
                   combination for 12 weeks, followed
                   by peg-IFN and RBV alone for 36
                   weeks
                   1 patient who discontinued prior to
                   completing 12 weeks of telaprevir
                   triple combination therapy

Prior Relapsers    25 patients treated with telaprevir    90% (26/29)     4% (1/28)
                   triple combination therapy for 12
                   weeks, followed by peg-IFN and RBV
                   alone for 12 weeks
                   3 patients treated with telaprevir
                   triple combination therapy for 12
                   weeks, followed by peg-IFN and RBV
                   alone for 36 weeks
                   1 patient who discontinued prior to
                   completing 12 weeks of telaprevir
                   triple combination therapy

Prior Viral        7 patients treated with telaprevir      75% (6/8)      0% (0/6)
Breakthroughs      triple combination therapy for 12
                   weeks, followed by peg-IFN and RBV
                   alone for 12 weeks
                   1 patients treated with telaprevir
                   triple combination therapy for 12
                   weeks, followed by peg-IFN and RBV
                   alone for 36 weeks

The interim results reported in the table above reflect data from all prior partial responders, relapsers and viral breakthroughs and from the prior null responders who we considered to have received an appropriate treatment regimen based on their prior response to

peg-IFN and RBV, consistent with certain amendments made during the conduct of the 107 Trial. The table does not include data from 23 prior null responders, who, prior to protocol amendments, were designated to receive only 24 weeks of therapy, and a portion of whom met the strict stopping rule criteria at week 4. When the 107 Trial began, all patients were to receive 12 weeks of telaprevir in combination with peg-IFN and RBV followed by an additional 12 weeks of peg-IFN and RBV. Stopping rules required any patient who did not achieve undetectable HCV RNA by week 4 to stop all treatment. In 2008, the 107 Trial protocol was amended in several respects. The most important change to the protocol was to the week 4 stopping rules, as it became evident that treatment-failure patients had a somewhat slower viral response to treatment with telaprevir triple-combination therapy than did treatment-naïve patients. Therefore, following the protocol amendment patients who had detectable HCV RNA at week 4 were permitted to continue therapy. In addition, while the initial study protocol specified 24 weeks of total treatment for all patients, a longer total treatment duration of 48 weeks was determined to be warranted in prior null responders to provide a higher likelihood of achieving an SVR.

Discontinuation of all therapy due to adverse events occurred in eight patients in the 107 Trial. A complete safety analysis is still being performed and will be reported when the full data are presented at a medical conference expected in 2010.