With two-drug combo data, GSK primes for an HIV market-share steal, but don't count out Gilead

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GSK could grab HIV market share from Gilead with a two-drug combo that's turning in promising phase 3 data.

GlaxoSmithKline (GSK) thought it might spin off its HIV business, ViiV Healthcare, last year, but decided against it as the unit continued churning out sales growth. Now the company is one step closer to a new FDA approval that could hone its edge in the competition against rival HIV drugmakers.

GSK and Gilead Sciences were among the headliners at the first major HIV confab of the year, the Conference on Retroviruses and Opportunistic Infections (CROI) in Seattle, and they kicked off the show with data on two drug regimens that analysts predict will be dueling blockbusters.

The ViiV approach combines its own HIV med Tivicay and Johnson & Johnson's (J&J) Edurant into a single pill. Gilead's data focused on a three-drug regimen that includes an as-yet-unapproved competitor to Tivicay, bictegravir. ViiV's two-drug combo, predicted to be "less risky" than cocktails with three or four meds, could be a new tool in GSK's ongoing battle with Gilead.

In a late-day announcement Monday, ViiV presented data from two phase 3 trials in which patients were switched from a three—or four—drug regimen to the single-pill combo. Viiv developed Tivicay which brought in sales of £953 million ($1.2 billion) last year while J&J's Janssen unit marketed Edurant. After 48 weeks, the two-drug regimen beat the virus down to undetectable levels in 95% of patients, making it non-inferior to treatments containing three or four medicines, GSK said.

Physicians who treat HIV have long held that when it comes to suppressing the virus, the more drugs the better. New data from trials called SWORD 1 and SWORD 2 suggest otherwise, said John Pottage, ViiV’s chief scientific and medical officer, in the announcement. “The results from these studies may change our understanding of how HIV can be managed,” Pottage said.

GSK is planning to submit the new pill for regulatory approvals this year.

Dominique Limet, ViiV’s CEO, told the Financial Times that the two-drug combo should be “less harmful and less hassle” than more involved treatments. The trials actually showed more side effects among the patients on the two-drug regimen, but Limet said that often happens when HIV patients switch treatments.

Limet predicted that, over the long term, the two-drug combo would prove to be “less risky.” During a press conference at the conference Monday, study investigator Josep Llibre of Hospital Universitari Germans Trias in Barcelona said, “there were no new side effects identified with the combination of these two drugs.”

During the conference, Gilead stole some of GSK’s thunder by announcing positive phase 2 results from a trial comparing its experimental compound bictegravir against GSK’s Tivicay. Both drugs are among the emerging class of integrase inhibitors, though some analysts predict that GSK’s two-drug combo could help it steal HIV market share from Gilead, which has long been the leading player.

Gilead’s data didn’t disappoint: When given as part of a three-drug regimen in newly diagnosed patients, bictegravir was as effective as a Tivicay combo and seemed to be slightly less toxic to the kidneys, said Evercore ISI analyst Mark Schoenebaum in a note to investors.

The data make it likely that Gilead “launches an unboosted integrase inhibitor that is competitive with GSK’s,” Schoenebaum wrote. Shares of Gilead, which had faltered amid plummeting sales of its hepatitis C drugs, bumped up about a percent (to $68.66) in pre-market trading Tuesday.

Gilead’s data prompted some questions during the CROI about how Tivicay and bictegravir compare in both potency and potential for drug resistance, a spokeswoman told FiercePharma via e-mail. She said that based on the data, bictegravir will need to be dosed at 100 mg per day to equal Tivicay’s 50 mg dose. In terms of resistance, she said, “we do not see currently meaningful differences between ViiV Healthcare’s medication and the other compound.”

Gilead’s data came from a small phase 2 trial, so “any comparison about efficacy or safety is premature,” she said.