Vertex Pharmaceuticals Incorporated and its South San Francisco, California-based collaborator, Alios BioPharma have announced results from a viral kinetic study of the adenosine nucleotide analogue pro-drug ALS-2158 for the treatment of hepatitis C. Data showed that seven days of dosing with up to 900 mg of ALS-2158 was well-tolerated in people with genotype 1 chronic hepatitis C, but that there was insufficient antiviral activity to warrant proceeding with further clinical development.

The companies also announced new data from an additional cohort of an ongoing viral kinetic study of the uridine nucleotide analogue pro-drug ALS-2200 in combination with ribavirin. There was a median 4.18 log10 reduction from baseline in HCV RNA after seven days of dosing with a once-daily 200 mg dose of ALS-2200 in combination with ribavirin in people with genotype 1 chronic hepatitis C who were new to treatment (n=8). Five patients achieved HCV RNA levels below the limit of quantification ( < LOQ = < 25 IU/mL) and two of these five achieved HCV RNA levels below the limit of detection (Roche COBAS Taqman HCV test, Version 2) after seven days of treatment.

Similar to previously announced data from the monotherapy cohort, ALS-2200 was well-tolerated, no patients discontinued due to adverse events and there were no serious adverse events. Data from the ALS-2200 study will be presented in an oral presentation at The Liver Meeting, the 63rd Annual Meeting of the American Association for the Study of Liver Diseases (AASLD) in Boston, November 9 to 13, 2012.

"Our goal is to develop all-oral regimens that are well-tolerated and provide a high rate of viral cure in a broad population of people with chronic hepatitis C," said Robert Kauffman, M.D., Ph.D., senior vice president and chief medical officer at Vertex. "We're making good progress and expect to begin all-oral Phase 2 combination studies by the end of this year."

Pending discussions with regulatory agencies, Vertex is planning one phase 2 study to evaluate ALS-2200 (VX-135) in combination with ribavirin, and one to evaluate ALS-2200 (VX-135) in combination with Incivek (telaprevir), the company's approved protease inhibitor for people with genotype 1 chronic hepatitis C. These studies will evaluate 12 total weeks of treatment with a primary endpoint of SVR12 (sustained viral response: undetectable hepatitis C virus 12 weeks after the end of treatment) in people with genotype 1 chronic hepatitis C.

ALS-2200 is a uridine nucleotide analogue pro-drug that appears to have a high barrier to drug resistance based on in vitro studies. It is designed to inhibit the replication of the hepatitis C virus by acting on the NS5B polymerase. In vitro studies of the compound showed antiviral activity across all genotypes, or forms, of the hepatitis C virus, including genotypes more prevalent outside of the United States.

Vertex gained worldwide rights to ALS-2200 through an exclusive licensing agreement signed with Alios BioPharma, Inc. in June 2011. The agreement also includes a research program that will focus on the discovery of additional nucleotide analogues that act on hepatitis C polymerase. Vertex has the option to select additional compounds for development emerging from the research program.

Incivek (telaprevir) tablets is an oral medicine that acts directly on the hepatitis C virus protease, an enzyme essential for viral replication.

Incivek was approved by the US Food and Drug Administration (FDA) in May 2011 and by Health Canada in August 2011 for use in combination with pegylated-interferon and ribavirin for adults with genotype 1 chronic hepatitis C with compensated liver disease (some level of damage to the liver but the liver still functions), including cirrhosis (scarring of the liver). Incivek is approved for people who are new to treatment, and for people who were treated previously with interferon-based treatment but who did not achieve a sustained viral response, or viral cure (relapsers, partial responders and null responders).

Vertex developed telaprevir in collaboration with Janssen and Mitsubishi Tanabe Pharma. Vertex has rights to commercialize telaprevir in North America where it is being marketed under the brand name Incivek (in-SEE-veck). Janssen has rights to commercialize telaprevir in Europe, South America, Australia, the Middle East and certain other countries. In September 2011, telaprevir was approved in the European Union and Switzerland. Telaprevir is known as Incivo in Europe. Mitsubishi Tanabe Pharma has rights to commercialize telaprevir in Japan and certain Far East countries. In September 2011, telaprevir was approved in Japan and is known as Telavic.