First, a word of caution -- both legacy Schering-Plough's Victrelis® (boceprevir), and Vertex Pharma's Incivek® (telaprevir) are still "investigational" drugs -- when we speak about treating HCV/HIV co-infected patients. That is, FDA has not approved either drug for use in such patients -- the companies' drugs are only labeled to treat Hep C (or HCV), at present. [So, technically speaking, their use in co-infected patients is "off-label", but under study, i.e. -- "investigational" in FDA parlance.]
Thus, both companies are running trials to determine whether either one will be allowed to be marketed as useful for treating patients with both HIV and Hep C -- a rather common occurence in the current US patient population. So far -- as was true with the overall efficacy studies on Hep C alone -- it seems that Incivek is posting more impressive cure rates, with (thus far) no HIV viral breakthroughs.
You'll recall that a month ago, FDA specifically warned about not treating HIV/HCV co-infected patients with a combination of Merck's Victrelis, and any ritonavir-boosted protease inhibitor -- as it seemed as though that combination (in some not-well understood way) weakened the anti-HIV regimen (a statistically-significant rate of HIV breakthroughs were observed, in patients on such a combination-laden therapy). Merck has concurred with this assessment, and has openly said that Victrelis shouldn't be used in such settings.
Significantly, no such drug-interaction/side-effect has been seen in any of Vertex's Incivek trials. The two base molecules are different enough (see at right), that it would be plausible to believe that Incivek (telaprevir) doesn't suffer the same defect, structurally, that Victrelis (boceprevir) does. Of course, we don't know exactly why this breakthough effect is happening -- but it does reinforce the notion that, in the science of biology (and thus evolution), even slight variations often make significant differences, over the vast multiples of generations that are the engine of evolution. Remember that HIV virus types (and, for that matter, HCV virus types) may transition through hundreds of thousands of such "generations" in just a few weeks' time, inside a human host.
What it all means, in my opinion, is that Vertex holds the lead in current Hep C regimens -- at least for the next few years -- to early 2016 (especially since Gilead's next-gen Hep C setback). And Vertex rose over 2 percent yesterday, on the NYSE, while Merck declined throughout the day -- dropping below $37, in the early going, only to make it most of the way back to flat, by day's end.
Here is a bit of the Reuters reporting, with the data, out of the conference in Seattle, late Tuesday -- do go read it all:
. . . .Vertex said 74 percent of trial patients treated with Incivek followed by the standard regimen of interferon and ribavirin were free of the hepatitis C virus, or HCV, 12 weeks after ending treatment, compared with 45 percent of patients given interferon and ribavirin alone.
There were no instances of a rebound of HIV for patients in the Incivek trial. Side effects seen more frequently with that drug were itching, headache, nausea, rash, fever and depression. No cases of severe rash were reported.
Merck's mid-stage trial found that 63.9 percent of patients treated with Victrelis and the standard hepatitis C therapy were free of HCV at 48 weeks of treatment, compared with 29.4 percent of patients treated only with interferon and ribavirin.
Two patients on Victrelis and three in the control group had an increase in HIV. . . .
So -- will Merck's (which is actually legacy Schering-Plough's) Hep C drug, Victrelis, ever reach 20 percent share, in the US market? I personally doubt it.