GlaxoSmithKline scores new win for 2-drug HIV regimen, this time in long-acting version

GSK's strategy to roll out several two-drug HIV therapies just got a boost, as data on a long-acting injection showed a positive phase 3 result. (Eric Sagonowsky)

Pushing ahead with its ambition for two-drug HIV therapies to challenge archrival Gilead Sciences, GlaxoSmithKline’s ViiV Healthcare now has results to support a two-drug monthly injection co-developed with Johnson & Johnson.

The injection combines ViiV’s investigational integrase inhibitor cabotegravir with Janssen’s Edurant (rilpivirine), which is already paired with Tivicay (dolutegravir) in Juluca, the world’s first complete two-drug therapy.

In a phase 3 dubbed Atlas on patients already virally suppressed, the monthly regimen showed similar efficacy compared with a three-drug therapy at week 48, the two companies reported Wednesday.

“If approved, this regimen would give people living with HIV one month between each dose of antiretroviral therapy, changing HIV treatment from 365 dosing days per year, to just 12,” said John Pottage, M.D., ViiV’s chief scientific and medical officer, in a statement.

Detailed data from the Atlas study will be presented later, and another study called Flair that's testing previously untreated patients will deliver top-line results soon. In that study, patients start with traditional triplet treatment and then switch to the monthly injectable. GSK is also testing the regimen as a bimonthly injection in phase 3.

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GSK’s strategy is to rewrite the HIV care textbook and establish two-drug therapies as the new standard, because exposing patients to fewer drugs could mean fewer side effects would develop over time, during treatment that can last for decades.

The Atlas readout followed two closely watched results unveiled last month from oral two-drug regimens taken daily. In one study, a combo of Tivicay and Epivir (lamivudine) matched a three-drug regimen of Tivicay plus Gilead’s Truvada (tenofovir and emtricitabine) at containing treatment-naïve patients’ viral load through a year of therapy. No treatment-related viral resistance cropped up in the two-drug arm.

But as analysts have said, to challenge the three-drug market currently led by Gilead, GSK still needs more data to quell concerns about potential long-term resistance, especially in the real world. As new data on Juluca showed, 89% of participants who were on the two-drug therapy for 100 weeks maintained viral suppression, below the 93% who switched to it for only a year. In addition, three patients who didn't take their drugs as directed developed Edurant-specific resistance.

While Pottage at that time said resistance development was normal in clinical trials that long, doubters might see it as evidence of the approach’s lower potency in the long run.

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Thanks to Tivicay-based drugs, GSK's HIV franchise registered 11% sales growth at constant exchange rates during the second quarter, to reach £1.19 billion ($1.5 billion), with £24 million of that from Juluca. According to CEO Emma Walmsley, speaking on the earnings call, Juluca now has a 3.7% share of new-to-brand prescriptions; total weekly scripts in the U.S. exceed a thousand.

GSK’s current HIV growth plan faces a powerful rival in Gilead’s just-approved Biktarvy, a three-drug regimen. In the second quarter—the first full quarter it was on the market—Biktarvy sold $183 million in the U.S.

“Based on its current trajectory, we anticipate that Biktarvy will become the No.1 single tablet regimen for treatment-naïve patients and will overtake Genvoya as the most successful launch in HIV history,” said CFO Robin Washington on Gilead’s second-quarter earnings call. According to Washington, a quarter of switch-overs to Biktarvy came from Tivicay-based drugs.