Gilead's Descovy seems set for a PrEP nod in men, FDA review shows. But what about women?

As FDA panel experts gear up to debate the merits of Gilead’s Descovy for HIV prevention, the question doesn’t seem to be whether it’s worthy of an indication in men, the largest part of the market. It’s whether it should get a green light in women.

FDA reviewers said they were all for Descovy approval as PrEP in two groups of people, according to briefing documents filed Monday. "[T]he data support the proposed PrEP indication for Descovy" in men who have sex with men and transgender women, the reviewers wrote.

And that's obviously good for Gilead. "The most important insight and information from the briefing documents is that Descovy is clearly going to be approved for its most important indication," SVB Leerink analyst Geoffrey Porges wrote in a note to clients.

As he notes, men account for the "vast majority" of pre-exposure prophylaxis (PrEP) use for Gilead’s Truvada, a med rapidly approaching the end of its exclusivity and whose sales Gilead is seeking to replace.

But the reviewers weren't so sure about an OK in other women, which would be helpful to have, Porges noted. "[F]or Gilead’s purposes it is useful to have a broad label with all relevant at-risk populations included," he added—including cisgender women.

Securing a go-ahead in those women depends on whether the FDA finds two external pharmacokinetic studies sufficient to extrapolate Descovy results from a study that enrolled only men and transgender women.  

Getting "such an endorsement" from the FDA’s advisory committee, which is set to convene Wednesday, would give the Descovy PrEP launch "additional momentum," Porges wrote.

All in all, the way Porges sees it, "Gilead’s requested label is likely to be granted"—and that’s good news for the company’s sales ambitions. Porges, for his part, forecasts $3.8 billion in peak Descovy sales, which should be more than sufficient to eventually offset the nearly $3 billion Truvada pulled in last year. More than 80% of Truvada's 2018 haul came from its PrEP indication.

While a recent SVB Leerink survey indicated Descovy could "rapidly gain PrEP market share," Gilead’s success will depend on how well it can penetrate a market that’s still in its early stages. An estimated 212,000 U.S. citizens currently take medication for PrEP, though the CDC pegs the potential population at 1.1 million.