Gilead HIV drug aces phase 2, teeing up tussle with GSK

Gilead has posted upbeat phase 2 data on its next-generation integrase inhibitor bictegravir in HIV patients. The drug more than held its own against GlaxoSmithKline’s dolutegravir, setting the stage for a larger-scale comparison in phase 3 and potential scrap for a multibillion-dollar market.

The trial gave 98 treatment naïve, HIV-infected adults emtricitabine and tenofovir alafenamide, the ingredients in Gilead’s Descovy, plus either the experimental bictegravir or GSK’s dolutegravir. After 24 and 48 weeks, viral loads in 97% of subjects in the bictegravir cohort had fallen to undetectable levels. That compared favorably to performance in the dolutegravir arm. After 24 weeks, 94% of patients in that cohort had undetectable viral loads. The figure fell to 91% by week 48.

What that means for the prospects of bictegravir and dolutegravir, which FDA approved as Tivicay in 2013, is a source of debate. Jefferies Analyst Brian Abrahams thinks the difference in efficacy could amount to a statistically-significant gap in phase 3, while his colleague Jeffrey Holford is less inclined to read much into the numerical superiority of bictegravir in the small study.

“Whilst the efficacy data with bictegravir were numerically superior to dolutegravir, we do not see this as meaningful, given the low number of patients in the study,” Holford wrote in a note to investors.

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Gilead will have a chance to put the debate to bed later this year when it publishes the first data from its four phase 3 trials of bictegravir. At the very least, the phase 2 data suggest Gilead has a drug that can hold its own against dolutegravir in terms of efficacy. And coming off a year of setbacks for its oncology pipeline and broader business, that goes down as a notable boost for the company.

How big a boost bictegravir delivers to Gilead’s $10 billion-plus HIV franchise will depend on the phase 3 efficacy data and, given the likely comparability in viral load suppression, the safety and tolerability of the two regimens.

Currently, the relative safety profiles are unknown. One patient withdrew from the bictegravir with hives, the suspected cause of which Gilead is yet to disclose. But overall the bictegravir patients performed marginally better on a check of how well their kidneys were working.

These factors could all come into play as Gilead looks to bictegravir to defend its HIV franchise in the face of competition from GSK’s ViiV. GSK has the advantage of data in the bank. Dolutegravir is already approved and data from two phase 3 trials released this week suggest it will pose stiff competition to Gilead. The phase 3 trials both found combinations of dolutegravir and Johnson & Johnson’s rilpivirine suppressed viral loads to undetectable levels in 95% of patients.

Gilead was up nearly 1% premarket on the news as it continues to slowly rebound after a fairly sharp fall in its share price since releasing its less-than-enthralling financials earlier this month.