Preliminary data from Achillion Pharmaceuticals' Phase 1b clinical trial of ACH-1625 reported

Once-Daily Dose Achieves 3.81 log10 Viral Load Reduction With Continued Safety and Tolerability

Conference Call Begins Wednesday, May 12 at 1:15 p.m. Eastern Time

Achillion Pharmaceuticals, Inc. (Nasdaq:ACHN) today reported additional preliminary data from its Phase 1b clinical trial of ACH-1625, which demonstrated that both the third and fourth patient cohorts receiving treatment with ACH-1625 achieved meaningful reductions in HCV RNA after five-day monotherapy, with continued safety and tolerability in patients with hepatitis C (HCV). ACH-1625 is an inhibitor of HCV NS3 protease that was discovered and is being developed by Achillion.

Third Dosing Cohort Results (200mg Twice Daily)

Subjects in the third cohort of HCV-infected patients received doses of 200mg twice-daily>

Fourth Dosing Cohort Results (600mg Once Daily)

Subjects in the fourth cohort of HCV-infected patients received doses of 600mg once-daily>

"We continue to be pleased with the robust results from these additional cohorts of our ACH-1625 Phase 1b trial with HCV-infected patients," said Michael D. Kishbauch, Achillion's President and Chief Executive Officer. "It is impressive that at all dose levels ACH-1625 has shown meaningful viral load reduction and sustained viral suppression post treatment course. Importantly, we believe the results from these last two cohorts demonstrated that ACH-1625 was effective at a lower dosing level and in a once-daily dose, features that distinguish our drug and suggest it could offer improvements over other protease inhibitors currently in development."

He continued, "In summary, these data round out the phase 1b program for ACH-1625 very favorably. If these results are sustained through further development, we believe the combination of potency, safety/tolerability, dosing flexibility and durability of effect will position ACH-1625 as a potential best-in-class protease inhibitor, while strategically enhancing Achillion for a variety of options. We remain very encouraged by these compelling results and look forward to advancing the drug into Phase 2 studies in the coming months."