Assistant Managing Editor

Gilead Sciences Inc.'s Viread gained FDA approval in adult patients with chronic hepatitis B virus, bolstering the company's HBV arsenal, which already includes the widely prescribed Hepsera.

The agency's decision, which came less than four months after Viread gained marketing authorization in HBV in Europe, was hardly a surprise given the drug's impressive Phase III data. As reported last year, preliminary results from the first Phase III trial showed that 71 percent of HBV e-antigen (HBeAg)-negative patients on Viread (tenofovir disoproxil fumarate) had a complete response at 48 weeks vs. 49 percent on Hepsera (adefovir dipivoxil), while data from a second Phase III study in HBe-Ag-positive patients demonstrated that 67 percent of those on Viread had a complete response at 48 weeks compared to 12 percent in the Hepsera arm. (See BioWorld Today, Oct. 15, 2007.)

The approval gave shares of Foster City, Calif.-based Gilead (NASDAQ:GILD) a barely perceptible bump Tuesday to close at $57.10, up 67 cents.

Nevertheless, analyst Michael Aberman, of Credit Suisse Securities, said in a research note that Viread's latest approval is expected to "reinforce Gilead as the market leader in chronic hepatitis B treatment," though he cautioned that the initial introduction of the drug might be "somewhat muted" because of a lower price compared to Hepsera and some likely cannibalization of Hepsera sales.

Second-quarter sales of Hepsera totaled $90.4 million.

Aberman said Credit Suisse's model projects Viread to pick up a 5 percent share of the HBV market this year and grow to 21 percent in 2012.

Gilead officials could not be reached for comment.

In the U.S., about 1.3 million people have HBV, a disease that can lead to liver cancer and cirrhosis, and the disease disproportionately affects Asian Americans, with an estimated one in 10 foreign-born Asian Americans living with the disease. Worldwide, more than 400 million have chronic HBV.

In addition to the U.S. and Europe, Viread is approved in HBV in Turkey, Australia and New Zealand. A marketing application is pending in Canada.

Viread, which is designed to treat HBV by blocking HBV DNA polymerase, previously gained approval in 2001 in HIV. It currently is marketed as a monotherapy and is part of fixed-dose combination treatments Truvada (with emtricitabine) and Atripla (with emtricitabine and Bristol-Myers Squibb Co.'s efavirenz).

Behind Viread in HBV is Pharmasset Inc.'s clevudine, a once-daily pyrimidine nucleoside analogue that started Phase III testing in October in both HBeAg-positive and HBeAg-negative patients.

HBeAg is a protein that appears later in the disease, after the surface antigen has been detected, but does not show up in all variations of HBV.

Princeton, N.J.-based Pharmasset and Gilead also recently agreed to assist the French National Agency for Research on AIDS and Viral Hepatitis in a head-to-head study of clevudine and Viread administered separately vs. in combination in non-cirrhotic HBV-infected patients.

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