Phase 1 clinical trial results of Achillion Pharmaceuticals' ACH-1625 to be presented at EASL meeting

Achillion Pharmaceuticals, Inc. (Nasdaq:ACHN) today presented data from the Company's ongoing Phase 1 clinical trial of ACH-1625 to treat hepatitis C (HCV) at the European Association for the Study of the Liver's (EASL) International Liver Congress taking place at the Reed Messe Wien Congress Center in Vienna, Austria from April 14-18, 2010.

The data were presented by Dr. Elizabeth Olek, Chief Medical Officer of Achillion, on April 15^th beginning at 8 a.m. local time in a poster presentation entitled, "Virological Response, Safety, and Pharmacokinetic Profile Following Single- and Multiple-Dose Administration of ACH-0141625 Protease Inhibitor to Healthy Volunteers and HCV Genotype-1 Patients" (Abstract #2012). The data demonstrated that treatment with ACH-1625 achieved a significant reduction in HCV RNA after five-day monotherapy in patients with HCV, showed sustained viral suppression in patients with HCV for at least seven days after dosing was completed, and was generally safe and well tolerated in patients with HCV and in healthy volunteers.

ACH-1625 is an inhibitor of HCV NS3 protease that was discovered and is being developed by Achillion.

"We are delighted to present this robust data set from our Phase 1 studies of ACH-1625 at this prestigious conference. These data show significant antiviral activity and demonstrate continued suppression of viral load after drug discontinuation while maintaining a safe and tolerable safety profile," said Dr. Olek. "The sustained suppression of viral load is important as it could be a distinguishing feature and competitive advantage for our compound in comparison to other HCV therapeutics in development, given the potential implications for patient compliance and the emergence of resistance."

"On the strength of these early data, we have initiated additional dose cohorts under this protocol to explore lower doses as well as a once-daily dose. We have now fully enrolled these additional cohorts and look forward to completing them and reporting results in the coming weeks," added Dr. Olek.

In addition to the aforementioned presentation, the following poster presentations highlighting ACH-1625 will be exhibited at the EASL meeting on April 16:

1. "Preclinical Antiviral Activity, Combination and Resistance of ACH-1625, A Potent HCV NS3 Protease Inhibitor" April 16 at 8 a.m. local time, Abstract #492, Presenter: Dr. Mingjun Huang, Executive Director, Virology of Achillion. Dr. Huang will present an analysis of the virology completed to date with ACH-1625 including potency, specificity and resistance profile.
    
2. "Characterization of the Hepatoselective Distribution of ACH-1625, a Potent, Clinical Stage HCV NS3 Protease Inhibitor" April 16 at 8 a.m. local time, Abstract #172, Presenter: Dr. Kathe Stauber, Director, Preclinical Candidate Selection of Achillion. Dr. Stauber will present an analysis of the selective liver distribution of ACH-1625 by hepatic uptake transporters, as well as a summary of the pharmacokinetics and metabolic stability of ACH-1625.

"We are very pleased to have this body of scientific and clinical data on ACH-1625 presented at this year's EASL meeting, as it continues to underscore the potential of ACH-1625 as a powerful protease inhibitor for the treatment of HCV," commented Michael D. Kishbauch, Chief Executive Officer of Achillion. "We look forward to advancing the development of this promising therapeutic, which R&D Directions magazine recently ranked among its 'Top 100' investigational drugs."

Poster Presentations

Copies of the EASL poster presentations will be available beginning Friday, April 16, 2010 on Achillion's website at www.achillion.com on the "Achillion Today" page.

Proof-of-Concept Study Results

In Phase 1a safety studies with ACH-1625, subjects in the single ascending dose (SAD) segment of the study received doses ranging from 50mg to 2000mg. Subjects in the Phase 1a multiple ascending dose (MAD) segment of the study received five days of ACH-1625 up to a maximal dose of 2000mg per day. Preliminary data from the SAD and MAD trial segments demonstrated ACH-1625 was well tolerated at all doses and there were no serious adverse events, and no clinically significant changes in vital signs, electrocardiograms or laboratory evaluations. All reported adverse events were classified as mild or moderate, were transient and showed no apparent dose relationship.

In December 2009, Achillion announced proof-of-concept data from the first dosing cohort in the Phase 1b study.

In January 2010, Achillion announced results from the second dosing cohort in the Phase 1b study.

SOURCE Achillion Pharmaceuticals, Inc.