Gilead files Truvada follow-up Descovy for PrEP

Gilead Sciences has filed Descovy, its successor to HIV pre-exposure prophylaxis (PrEP) therapy Truvada, in the US, spending a priority review voucher (PRV) to set up a verdict within six months.

Why the urgency? Descovy (emtricitabine/tenofovir alafenamide) has some advantages over Truvada, such as fewer side effects, but Gilead needs to build momentum behind the new drug before Truvada (emtricitabine/tenofovir disoproxil fumarate) loses patent protection in 2021.

Truvada is the only FDA-approved PrEP regimen – given to individuals who are HIV-negative but at risk of HIV – and is a massively profitable drug for Gilead. Analysts suggest that upwards of $2 billion of its $3 billion sales last year came from use in PrEP, and according to Gilead approximately 202,000 people were taking Truvada for prevention as of the end of 2008, out of a potential eligible population of around 1.1 million.

The big question is whether Descovy’s clinical profile is sufficiently different from Truvada’s to compensate for the cost savings that will become available once generics of the latter product reach the US market.

Gilead revealed top-line results from the head-to-head DISCOVER trial of Descovy and Truvada last month, which showed that the newer drug was non-inferior when it came to preventing HIV infection, with numerically fewer cases (seven versus 15) that did not however reach statistical significance.

The company said that the safety data between the two drugs was important, with “statistically significant improvements in renal and bone laboratory parameters” for patients on Descovy versus Truvada. Descovy and Truvada were both well tolerated and had low discontinuation rates due to adverse events of 1.3% and 1.8%, respectively.

Given that PrEP is given to healthy individuals over a long period, that cleaner safety profile could be a big draw if Descovy is approved, at least while both products attract premium pricing – and that explains why Gilead has used a PRV to shorten the FDA’s review time to six months.

Of course, the balance could shift when cheaper generics become available, particularly if payers put up prescribing obstacles for the newer brand.

“Data have shown that when used in combination with other agents for HIV treatment, Descovy offers high efficacy and additional benefits with respect to renal and bone safety compared with Truvada,” commented Gilead’s head of R&D John McHutchison.

“The results from the DISCOVER trial suggest that Descovy may offer those same benefits for HIV prevention, which are important considerations for the potential long-term use of PrEP,” he added.