ViiV presses go on FDA filing for first-in-class HIV drug fostemsavir

ViiV Healthcare has fulfilled its pledge of submitting its new HIV drug fostemsavir for approval before year end, filing a dossier with the FDA.

The HIV specialist – majority-owned by GlaxoSmithKline – is seeking approval from the US regulator for fostemsavir for use as a rescue therapy for heavily pre-treated adults in whom the virus has developed resistance to multiple anti-retroviral drug therapies.

If approved, fostemsavir would be reserved for use in people with HIV who can’t be given a drug combination that suppresses HIV because of “resistance, intolerance or safety considerations,” said GSK in a statement.

Fostemsavir has both fast-track and breakthrough designations from the FDA, which should mean a rapid review by the regulator, and ViiV says it will file the drug in Europe and elsewhere in the coming months.

HIV’s notorious ability to mutate and develop resistance to current drugs means that while most people with HIV can expect long-term suppression with drug therapy, some experience treatment failures that progressively limit the drugs they can use to control the infection.

Fostemsavir is the lead candidate in a new class of HIV attachment inhibitors, which bind to glycoprotein 120 (gp120) on the envelope of HIV and stop the virus latching on to host cells. Its mechanism of action means there is no cross-resistance to other classes of  anti-retrovirals, according to ViiV.

The FDA filing is based on the phase 3 BRIGHTE study, which showed that fostemsavir was significantly better than placebo when added on to current therapy at reducing viral load in this hard-to-treat patient population.  

After 96 weeks’ treatment, almost two-thirds (60%) of patients in the fostemsavir group had viral suppression, and showed other benefits including an increase in CD4+ T-cell counts, the main cell type affected by HIV infection.

Fostemsavir is one of a series of new HIV therapies that ViiV is hoping will inject new momentum in its HIV franchise as it competes with arch-rival Gilead Sciences in the market, along with two-drug and depot injection products for newly-diagnosed HIV patients and those who may want to switch from other regimens.

Fostemsavir is expected to play a relatively minor role in that as the eligible patient population will be small, with analysts previously predicting it could be a $400 million-plus product whereas other new ViiV products like Juluca (dolutegravir/rilpivirine) are tipped to become blockbusters. That said, its significance for patients far outweighs its commercial prospects.

“We’ve made incredible strides in our understanding and treatment of HIV over the past 30 years. However, the complexities of the virus mean that unsuccessful treatment and antiviral resistance are still major concerns for certain people living with HIV,” said ViiV’s head of R&D Kimberly Smith.

“These individuals may soon have an entirely new way to target and treat HIV with fostemsavir, aiding them in their efforts to achieve viral suppression,” she added.