Gilead proves it’s one tough contender in HIV, but don’t count GSK out of the fight

Looking to defend itself against a new HIV drug from Gilead, GlaxoSmithKline’s $GSK ViiV posted a near mirror image of viral suppression for its two-drug combo of Tivicay (dolutegravir) tied to J&J’s rilpivirine compared with the results from the three- and four-drug cocktails it hopes to replace. But Gilead $GILD struck first, releasing the first look at some impressive Phase II data on their rival drug bictegravir.

Reporting out data from its two Phase III studies, SWORD-1 and SWORD-2, GSK revealed this evening that the current cocktails in use successfully suppressed the virus in 485 of 511 patients; 95%. Dolutegravir + rilpivirine managed to do the same in 486 of 513 patients, also 95% with an adjusted difference of -0.2%. Study results were presented at the annual Conference on Retroviruses and Opportunistic Infections in Seattle.

John Pottage

John C. Pottage, chief scientific and medical officer for ViiV commented:

The results from these studies may change our understanding of how HIV can be managed. For more than 20 years we thought that three or more drugs were required to maintain virologic suppression, but the SWORD studies provide compelling data that suppression may be maintained with a two drug regimen of dolutegravir and rilpivirine. These data mark an exciting first step towards making two drug regimens a reality in HIV treatment. We are planning regulatory submissions for this two-drug regimen as a single tablet in 2017.

Analysts who follow the field gave GSK’s combo a very close review, but it’s the Phase II data on bictegravir they were waiting for. Gilead hustled quickly into Phase III studies without waiting for their mid-stage data review. And late-stage data is expected to fall in Q2. But the Phase II preview Monday evening earned some rave reviews.

At 24 weeks, Gilead reported, HIV was undetectable in 97% of the patients taking bictegravir, compared to 94% for dolutegravir. At 48 weeks Gilead’s drug maintained that 97% rate, while GSK’s drug dropped to 91%.

This was a small mid-stage study, but analysts are hopeful that this will all play out the same way in Phase III, setting up a big showdown between two big players.

Brian Abrahams at Jefferies had this to say:

Given the small size of the study, this did not reach stat. sig., but we calculate that it would potentially be sufficient to be stat. sig. in ph.III if comparable virological suppression observed. Even if not, we believe hints at potential advantageous profile of bic vs. dolu. Notably, no patients on either regimen who had virological failure developed resistance. CD4 count increases also looked a bit better for bic (+258 vs. +192 for dolu).

For GSK, their Phase III success underscores the importance of ViiV as the main drug pipeline continues to leave analysts cold and generic Advair threatens to unload an avalanche of trouble. GSK is the big player at ViiV, with smaller stakes in the hands of Pfizer and Shionogi. And a two-drug regimen could offer a better way to soften side effects for patients and perhaps cut costs for payers in a competitive field.

Quite a few analysts, though, expect Gilead to come out on top of this latest dust-up.

The stakes for Gilead have grown considerably in the last 6 months, as its hepatitis C franchise has begun to melt away and a series of setbacks in the clinic wiped out much of the enthusiasm for the company’s pipeline. A win on bictegravir is essential.

Leerink’s Geoffrey Porges recently noted:

We believe that investor expectations are now that bictegravir is numerically better than dolutegravir in the head to head phase II trial being presented and disclosed publicly this week (Tuesday, February 14). Anything less than a numerical superiority and unblemished safety and tolerability would be a disappointment to investors, who are increasingly focused on HIV as Gilead’s foundation and value driver.

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Research Scientist - Immunology
Recursion Pharmaceuticals Salt Lake City, UT
Director of Operations
Atlas Venture Cambridge, MA

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