Glaxo, Shionogi Say HIV Drug Beats Gilead Atripla in Test

An experimental treatment for HIV developed by GlaxoSmithKline Plc, Pfizer Inc. and Shionogi & Co. reduced the virus in more people than Gilead Sciences Inc.’s Atripla, suggesting it may supplant the world’s best-selling AIDS medicine as the preferred front-line therapy.

After 48 weeks of treatment, 88 percent of patients receiving a combination of dolutegravir and two other drugs in a study had undetectable levels of virus in their blood, compared with 81 percent of those getting Atripla, London-based Glaxo and Shionogi of Osaka, Japan, said in a joint statement today. The difference was primarily the result of more patients on Atripla dropping out because of side effects, they said.

The study, dubbed Single, is the second of four late-stage trials to be reported this year that Glaxo plans to use in filing for regulatory clearance of dolutegravir. If approved, dolutegravir would be the second in a new class of HIV medicines called integrase inhibitors that work by blocking the virus’s ability to replicate.

“It looks like it’s a very effective treatment,” said Graham Cooke, an infectious diseases researcher at Imperial College London who wasn’t involved in the trial. “Atripla is a very good drug, and we use it a lot, but it has a side-effect profile that causes a problem for a significant number of patients.”

Doubled Estimate

The results mean peak sales may reach $5 billion, double an earlier estimate, James Gordon, an analyst at JPMorgan Chase & Co., said in a report. He raised his estimate of the probability of regulatory approval to 100 percent from 50 percent.

“Glaxo announced surprisingly good data,” Gordon wrote. “This news is unexpected as we had thought the most likely outcome” was that dolutegravir would be shown to be statistically equal to Atripla.

Among the 414 patients getting the dolutegravir-based combination, 2 percent quit the trial because of side effects, compared with 10 percent of the 419 who received Atripla.

Forty-one percent of patients on Atripla had nervous-system side effects, compared with 15 percent of those getting dolutegravir, the companies said. The rate of gastrointestinal side effects was the same for both drugs.

Integrase Inhibitor

Atripla brought in $3.2 billion of revenue last year for Foster City, California-based Gilead. Merck & Co.’s raltegravir, marketed as Isentress, is the only approved integrase inhibitor. Gilead last month applied for U.S. regulatory approval of its own drug in the class, elvitegravir.

In the first of the four late-stage trials, Glaxo said in April that dolutegravir on its own suppressed the HIV virus in 88 percent of study participants, compared with raltegravir, which quelled the disease in 85 percent.

“It’s not going to be a huge success for them overnight, but it is looking good,” Alistair Campbell, an analyst at Berenberg Bank in London, said in an interview today. “The integrase inhibitor market is probably going to be quite competitive.” He recommends buying Glaxo’s stock.

Glaxo rose 0.1 percent to 1,455.5 pence as of 2:44 p.m. in London. Gilead dropped 2.4 percent to $50.34 in New York. The statement was published after the close of trading in Tokyo, where Shionogi fell 0.7 percent to 1,100 yen.

Dolutegravir is being developed by Glaxo and Pfizer’s ViiV Healthcare Ltd. joint venture with Shionogi. Shionogi and ViiV will split earnings from sales of dolutegravir. As Glaxo owns 85 percent of ViiV, it will take 42.5 percent of profit from the drug and New York-based Pfizer will receive 7.5 percent.

Dolutegravir was combined in the trial with abacavir and lamivudine, two approved drugs made by ViiV. Glaxo, the U.K.’s biggest drugmaker, introduced the first AIDS pill, known as AZT or retrovir, in 1987.

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