- Gilead Sciences' newer HIV medication, Descovy, has proved non-inferior to one of its mainstay therapies, Truvada, in a late-stage trial that the big biotech says is the largest HIV prevention study conducted to date.
- Named DISCOVER, the two-year trial enrolled nearly 5,400 participants at risk for sexually acquired HIV infection. They received once-daily regimens of either Truvada or Descovy for HIV pre-exposure prophylaxis (PrEP). Investigators found seven HIV infections across 2,694 patients taking Descovy and 15 HIV infections across 2,693 participants receiving Truvada. Gilead noted that of the 22 HIV infections reported, five were likely acquired before the patients entered the study.
- The results mean Descovy met the study's primary endpoint. It also significantly outperformed Truvada on secondary endpoints of bone and renal safety. Gilead said the data support a supplemental regulatory filing for Descovy for PrEP, though the company didn't elaborate on when that filing would take place in a March 6 statement.
Gilead is the leader in HIV therapy, outfitted with six blockbuster treatments on the market. The biotech organizes its arsenal into two main groups: drugs with a Truvada (emtricitabine/tenofovir disoproxil fumarate) backbone, like Atripla and Stribild, and drugs with a Descovy (emtricitabine/tenofovir alafenamide) backbone, like Genvoya and Biktarvy.
Revenue from the groups have been moving in opposite directions as the company has introduced its newer medicines. Sales of Truvada-based products declined in recent years, from $9.5 billion in 2016 to $5.5 billion in 2018. Meanwhile, sales of Descovy-based therapies are on the rise, growing from $2.1 billion to $9 billion over those years.
Gilead explained the weaker sales from Truvada-based products last year stemmed largely from patients switching to regimens containing tenofovir alafenamide. The switching is a positive for Gilead's business, given that the primary patents protecting Truvada in the U.S. are set to expire in 2021. (The strategy has also brought Gilead criticism from patient advocacy groups.)
In Europe, Truvada is already facing generic competition.
Truvada first gained Food and Drug Administration approval in 2004 to treat HIV infection. Its label would later expand to include PrEP.
Now, data from DISCOVER should help Gilead as it works to secure a similar expansion for Descovy's label. The PrEP indication has been a boon to Truvada's sales, and could do the same for Descovy.
"The very low incidence of HIV in both treatment arms, combined with Descovy’s improved renal and bone safety as compared with Truvada, demonstrate that Descovy for PrEP may help build on the progress made by Truvada," said Brad Hare, chief of infectious diseases at Kaiser-Permanente, San Francisco, in the March 6 statement from Gilead.
Notably, a Descovy label expansion would provide another advantage as it competes with rival GlaxoSmithKline.
The British pharma and its subsidiary ViiV Healthcare are banking big on two-drug HIV regimens, arguing they can be just as effective as three-drug combinations without the risk of long-term side effects like renal problems and reduced bone mineral density.
So far, however, GSK's doublet Juluca (dolutegravir/rilpivirine) hasn't experienced nearly as much market success as Gilead's triplet Biktarvy, which is a mixture of Descovy and another active ingredient called bictegravir.
Success in DISCOVER is the first of two clinical milestones Gilead hopes to hit in March, which coincidentally is Daniel O'Day's first month as CEO of the biotech. Results from Phase 3 studies testing Gilead and partner Galpagos' rheumatoid arthritis drug filgotinib are also due, and could swing the company's stock in either direction depending on outcome.