Updated with new information, current stock price.
FOSTER CITY, Calif. (
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 being magnified in the eyes of investors.
Gilead shares plunged 16% to $45.85 in Friday pre-market trading while investors bid up share in other hepatitis C drug stocks, including
Achillion is the biggest gainer Friday, up 20% to $10.52, because the company is developing two drugs -- a protease inhibitor and an NS5A inhibitor -- that may now play more important roles in future all-oral hepatitis C regimens. Achillion, like Idenix, has been mentioned as a potential takeover target..
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.
GS-7977 is a so-called nucleotide polymerase inhibitor, a potent class of hepatitis C drug believed to have a high barrier to viral resistance. This means the virus has a difficult time mutating or changing into forms that can fight off the drug. Friday's negative data, however, has raised questions about just how effective these "nukes" might be.
Genotype 1 is the predominant form of hepatitis C found in North America and Europe. It's also the most difficult form of the disease to treat. On a call with investors Friday morning, Gilead executives said the company is exploring further ways of treating genotype 1 patients, including adding other direct-acting antiviral drugs to the GS-7977-ribavirin combination or perhaps treating patients longer.
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. Gilead is also studying GS-7977 in combination with an experimental drug from
--Written by Adam Feuerstein in Boston.
>To contact the writer of this article, click here:
>To follow the writer on Twitter, go to
>To submit a news tip, send an email to:
and become a fan on
Adam Feuerstein writes regularly for TheStreet. In keeping with company editorial policy, he doesn't own or short individual stocks, although he owns stock in TheStreet. He also doesn't invest in hedge funds or other private investment partnerships. Feuerstein appreciates your feedback;
to send him an email.