Gilead strikes back at GSK with positive HIV head-to-head trial data for expected blockbuster

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Gilead CEO John Milligan has told investors he's confident his company can maintain its leading position in the HIV market. (Screenshot: Biotechnology Innovation Organization Fireside Chat / YouTube)

The only obstacle standing in the way of Gilead’s new HIV combo drug Biktarvy becoming a blockbuster is competition from a rival that’s so intent on stealing market share away from the longtime HIV leader it filed a patent lawsuit to try to stall the new drug. That rival is GlaxoSmithKline, which also answered Gilead’s FDA approval of Biktarvy in February by launching its eighth phase 3 study of two HIV drugs developed by GSK unit ViiV Healthcare, Tivicay and Epivir.

Now Gilead is striking back, releasing data from a head-to-head clinical trial showing that Biktarvy is noninferior to a treatment containing Tivicay and Epivir, plus another ViiV drug, Ziagen. The trial tracked 563 HIV patients for 48 weeks, some of whom switched from GSK’s three-drug regimen to Biktarvy, which also contains three medicines. The data was released at the Conference on Retroviruses and Opportunistic Infections (CROI) in Boston.

Perhaps the most significant data from Gilead’s latest trial, at least from a marketing standpoint, concerned side effects. Patients taking Gilead’s drug had only an 8% incidence of treatment-related effects, as compared to 16% who were on the GSK cocktail.

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The data indicates “that Biktarvy may be appropriate for a wide range of people living with HIV who are either new to treatment or who choose to switch regimens,” said Norbert Bischofberger, Ph.D., Gilead’s chief scientific officer and executive VP of research and development in a statement.

Gilead’s rivalry with GSK in HIV kicked into high gear late last year, when ViiV won FDA approval for Juluca, the first two-drug combination treatment for HIV, which combines Tivicay and another medication called Edurant. But GSK’s new drug was not approved for patients who are new to antiretroviral drugs, whereas Gilead’s Biktarvy did get the green light for those treatment-naïve patients.

RELATED: Gilead's Biktarvy wins megablockbuster HIV nod, and rival GlaxoSmithKline strikes back

That marketing advantage is one reason Wall Street analysts have high hopes for Biktarvy. Consensus estimates place peak sales at about $6 billion. But some analysts are even more optimistic. Leerink Partners’ Geoffrey Porges, for one, is estimating the drug will peak at annual sales of $10 billion.

GSK is doing everything it can to give its two-drug combo Juluca an advantage, including that patent suit. The suit alleges that the only novel ingredient in Gilead’s Biktarvy—the integrase inhibitor bictegravir—infringes GSK’s patent on a novel chemical scaffolding that’s an essential element for integrase inhibitors.

Gilead is "steadfast in our opinion that Biktarvy does not infringe ViiV’s U.S. patent," a spokeswoman for the company told Fierce in February.

It may be a while before a winner can be called in the Gilead-GSK HIV market duel, but one thing can be said for certain: Gilead really needs Biktarvy to be a blockbuster. During the company’s fourth-quarter earnings announcement, it told analysts to expect sales in its hepatitis C franchise to come in between $3.5 billion and $4 billion this year—falling short of the average analyst projection of $5 billion. Gilead is facing tough competition from AbbVie, which launched its new HCV drug, Mavyret, at a deep discount to rival therapies last year.

RELATED: Dogged by AbbVie's new share-stealing Mavyret, Gilead's hep C forecast comes in far short

Gilead plans to churn out more data to support Biktarvy’s launch in HIV. The company is running one trial in women with HIV and another in children and adolescents. It is also releasing data from those studies at CROI. Gilead has also filed for approval of Biktarvy in the European Union.

John Milligan, CEO of Gilead, insists he’s not concerned about the competition in HIV from GSK. When asked about the risk that GSK might undercut Gilead on price during a conference call following the fourth-quarter earnings report, Milligan responded that pricing wars have “never happened” in HIV. “I can tell you in the U.S., we expect to maintain our market share,” he said.