Gilead's Descovy AdCom gets 'controversial' as panelists split over PrEP use in women

J.P. Morgan analysts expect Descovy to rack up $900 million in peak PrEP sales. (Gilead China)

As expected, Gilead’s Descovy had no problem securing backing from an FDA panel of experts for HIV prevention in men and transgender women. But beyond that, it ran into some issues.

On Wednesday, an advisory committee split over whether a PrEP approval for Descovy should include cisgender women, with 8 voting yes and 10 voting no. At issue was the absence of cisgender women in Gilead’s Discover trial, which formed the basis of its application.

“Panelists noted the concerns of vaginal/cervix tissue exposure and the inadequate amount of data used to extrapolate efficacy/safety more broadly,” J.P. Morgan analyst Cory Kasimov wrote in a note to clients.

They found it much easier to get behind Descovy in men who have sex with men and transgender women, voting 16-2 in favor of its safety and efficacy profile in that group. But there were some caveats, Kasimov noted.

RELATED: Gilead's Descovy snared its PrEP data, but can it stand up to Truvada generics?

Gilead is working to position Descovy as a safer option than Truvada, which is set to lose U.S. patent protection on Sept. 30. "We really believe that Descovy for PrEP could offer important safety advantages over Truvada as it shows superior safety for bone and renal as well as rapid onset and longer duration of preventative therapy than Truvada," commercial chief Johanna Mercier said on the company's second-quarter conference call last month.

But it doesn't have data showing that Descovy is actually superior to the elder drug, and "the panelists stressed … that the non-inferiority nature of the safety and efficacy profile between Descovy” and predecessor drug Truvada “needs to be adequately communicated in the commercial setting,” he wrote. They also voiced concerns about how representative the Discover trial’s population was of the broader population, especially for transgender women and minorities.

For both groups, experts recommended postmarketing studies to study Descovy in the populations in question.

“The AdCom for Descovy in PrEP was more controversial than the company anticipated,” Kasimov noted, calling out commentary from the second-quarter call.

“The FDA has the liberty to convene an advisory committee for a number of different reasons. And in this case for Descovy for PrEP, I think it's probably part of a larger effort to increase awareness and signal the commitments of the government to HIV PrEP efforts,” Diana Brainard, M.D., Gilead SVP and HIV head, said at the time.

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

But while things may have gotten interesting on Wednesday, Kasimov still sees “a good chance that Descovy will be approved” for PrEP in the fourth quarter, and he sees it racking up $900 million in the indication at its peak.

If it does snag the green light, “the key question going forward will be how quickly GILD can transition the bulk of its current Truvada PrEP patients to Descovy and penetrate the market more broadly” before copies of Truvada take hold, he wrote.