The 100% cure rates from Gilead Sciences' (GILD) and Bristol-Myers Squibb's (BMY) all-oral combination might have taken centre stage day one at the EASL liver conference, but data from other studies of GS-7977 to emerge make equally comforting reading for the drug's proud new owner.
Stronger than expected results emerged from both the Electron and Quantum studies, making it almost certain that the potent nucleotide analogue will form the backbone of the first all-oral hepatitis C therapy to reach the market. Gilead shares soared 14% to $53.31 in early trade.
Data has gradually emerged from the phase II Electron study since Gilead bought Pharmasset and GS-7977 late last year, for an eye watering $11bn. The multi-arm study has looked at a variety of patients and pitted the drug in several combinations, with and without interferon, in an attempt to define its strengths and weaknesses.
Limitations to the drug's effectiveness were revealed earlier this year when the virus returned in four patients who had completed 12 weeks of treatment. These patients had previously failed to respond to interferon, a tough group to treat but disappointing all the same (Expectations reined in as Gilead hits bump on the hep C road, February 17, 2012).
The data released at EASL was the first look at its potential, in combination with ribarivin, in treatment naïve genotype 1 patients - the largest group and therefore biggest commercial opportunity. Of the 25 patients who completed 12 weeks of treatment with GS-7977 plus ribavirin, 88% has undetectable virus four weeks after completion of treatment. Three patients experienced viral relapse after treatment was completed.
The results prompted Professor Edward Gane, of Auckland City Hospital in New Zealand and principal investigator of the Electron study, to predict that this 12 week regimen may be enough to cure hepatitis C in many genotype 1 patients, including those who are currently not candidates to receive interferon.
All oral the buzz word
In a press release timed to coincide with the conference, Gilead also released data from a similar phase II called Quantum, which tested 12 and 24-week treatment duration of GS-7977 plus ribavirin, in treatment-naive patients with a range of genotypes. Of 17 genotype one patients in the 12 week arm 59% were virus free at four weeks, with seven relapses. The weaker efficacy has been blamed on a higher proportion of patients with a strain of genotype one that is harder to treat.
Back at the conference data from another '7977 study was released, called Atomic, this time combining the drug with interferon and ribavirin in a variety of genotypes. With a 90% cure rate at 12 weeks, the investigators concluded that regimen was potent and highly safe.
With all-oral now the buzz word, the Atomic data makes for strong confirmation of the drug's effectiveness, rather than pointing to future protocols. Meanwhile the Electron data confirms the drug's potential in future all oral regimens; stunning results today from the combination of '7977 and Bristol-Myers' daclatasvir suggests the potency of the Gilead drug can be boosted further by using a newer class of anti-viral, over ribavirin (EASL - Gilead-BMS score all-oral hep C win but will pairing last?, April 19, 2012).
"7977 is the front runner at the moment," Dr Mark Thursz, secretary-general of EASL and a hepatology professor at Imperial College in London told EP Vantage. "When I say I think there will be interferon free combinations on the market in two years I'm assuming that '7977 will be at that stage - but that will change and other combinations will emerge."
It might be positioned as the potent oral direct acting anti-viral at the moment, but equally or more promising agents could still emerge, from the same class or others. However GS-7977 now looks certain to reach the market as part of one of the first all oral combinations - what the other component of the combination will be, has yet to be confirmed.