FOSTER CITY, Calif. (TheStreet) Gilead Sciences(GILD) just had its first stumble in the race to develop an all-oral therapy for hepatitis C. A two-drug regimen of Gilead's experimental GS-7977 plus ribavirin failed to suppress the hepatitis C virus in a group of difficult-to-treat patients who had also failed prior therapy, Gilead announced Friday. Gilead's GS-7977 streak as the ultimate, flawless hepatitis C drug has now ended. Friday's negative results are a setback and not a fatal blow to the drug's future. However, Gilead spent $11 billion to gain control of GS-7977 through the acquisition of Pharmasset so any failure, no matter how small, is sure to be magnified in the eyes of investors. Gilead shares plunged 19% to $44.50 in Friday pre-market trading. In this study, ten hepatitis C genotype 1 patients with a prior "null" response to interferon and ribavirin were treated with a combination of GS-7977 plus ribavirin for 12 weeks. Within four weeks of completing treatment, six of eight patients relapsed, meaning the hepatitis C virus, which had been suppressed, came roaring back. Two patients have not relapsed, however they have only reached the two week post-treatment time point, Gilead said.
Null responders are among the most difficult to treat hepatitis C patients because prior therapy has not worked for them. "These data answer an important question about the use of GS-7977 and ribavirin for the treatment of genotype 1 null responder patients, suggesting that additional direct acting antivirals may be necessary to effectively treat this patient population," said Norbert Bischofberger, Gilead's research chief, in a statement.
Further data on GS-7977 is coming soon, including important results from a study testing the drug in combination with ribavirin in genoptype 1 patients who have not been previously treated. A chink in the previous untarnished armor of GS-7977 may mean a boost for other companies developing new oral hepatitis C drugs, including Vertex Pharmaceuticals(VRTX_), Bristol-Myers Squibb(BMY_) and Idenix Pharmaceuticals(IDIX) .. Written by Adam Feuerstein in Boston.
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