Biotech Values

[iwfal]

HCV -

Gilead Sciences, Inc. (NASDAQ:GILD) announced today that the majority of hepatitis C genotype 1 patients with a prior “null” response to an interferon (IFN)-containing regimen enrolled in the ongoing ELECTRON study experienced viral relapse within four weeks of completing 12 weeks of treatment with GS-7977 plus ribavirin (RBV)

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I am somewhat surprised that the market and this board consider the above results a surprise. To date no two DAA (no ifn) has shown good efficacy in G1a patients (G1b is, apparently, a different matter - see #msg-67597202). So why would one DAA + rib (a relatively weak drug) be expected to be a cure? I'd agree it was a trial worth running on the off chance of a surprise - but the market reaction was as if it was expected to work.

Note also that to date all the SVR data in dual DAA (no PR) has been in null responders. I think there is a general tendency to believe that even a 30 or 40% SVR in nulls will map to >95% response in naives. Certainly this seems possible - but hardly a sure thing since resistance to ifn/rib is probably a somewhat different thing than being resistant to 2 DAAs. I.e. Null responders are a pool of HCV patients enriched with strains resistant to ifn/rib. It is NOT a pool of HCV patients enriched with strains resistant to 2 DAAs. Thus if, in the extreme case, resistance to ifn/rib and resistance to 2DAAs are entirely independent states you would expect to see the SVR rate of 2DAAs in inf/rib nulls be exactly the same as the SVR rate of 2DAAs in treatment naive patients.

(Obviously I do NOT expect resistance to ifn/rib and resistance to 2DAAs to be entirely independent - but I would expect some independence - how much is the question. We should run a quiz - in the G1a population what SVR rate should be expected of the best 2DAA option of the first 3 2DAA trials we see. I'd guess less than 85% - and think there is some small chance it is as low as 50%.)