By Mackenzie Tatananni
With years to go before Merck loses patent protection for its biggest revenue driver, all eyes are on the company to find a new miracle drug. It seems Merck may be on the right path.
On Wednesday, the drugmaker presented results from Phase 3 trials evaluating the efficacy of its once-daily, oral regimen of doravirine and islatravir in adults with HIV-1. The trial evaluated the regimen's success in preventing HIV-1 replication using viral load, a measure of the amount of HIV genetic material in the blood.
The two-drug regimen was compared with Biktarvy, a three-drug regimen from Gilead Sciences, in a patient population that hadn't previously received antiretroviral treatment.
It ultimately showed non-inferiority and a similar safety profile to Biktarvy at 48 weeks of treatment, meaning it worked just as well as the world's best-selling HIV drug. In a world where pharmaceutical companies are racing to distinguish themselves from competitors, results like these are a big deal.
"We're seeing the need for more medicines that are easier to take, that are less likely to have adverse experiences, that have the kind of potency you need from modern HIV medicines," said Eliav Barr, Merck's chief medical officer and senior vice president and head of global clinical development, in an interview with Barron's.
The regimen combines two distinct medications, one fewer than Biktarvy, into a single treatment. While both drugs target the HIV-1 reverse transcriptase enzyme to prevent viral replication, they do so through entirely different biochemical pathways.
Doravirine belongs to a class called non-nucleoside reverse transcriptase inhibitors. Islatravir, meanwhile, is what's known as a nucleoside reverse transcriptase translocation inhibitor, a novel drug that is significantly more potent.
"It's got multiple ways of stopping the HIV from replicating and it's very potent, so all you need is a tiny dose," Barr explained. "In fact, every pill contains only 1/4 of a milligram," coupled with 100 milligrams of doravirine in the same pill.
Merck announced last July that the Food and Drug Administration had agreed to review a new drug application for doravirine/islatravir. Barr indicated that progress along the regulatory front has been steady. "It's been pretty routine," he said of the regulatory process. "Hopefully we'll hear good news."
It may seem like an attempt to go head-to-head with Gilead, but in reality, the companies have partnered to develop even more powerful drugs. These include a regimen combining islatravir with lenacapavir, a Gilead medication sold under the names Sunlenca for HIV treatment and Yeztugo for HIV prevention.
"Competition is not a dirty word," Barr said. "It is a terrific stimulant of a sense of urgency." Merck's "credo" is that "if it's good for the patient, it's good for the company and ultimately it's good for the shareholder," he added.
Merck currently has four HIV drug development programs including a once-daily oral treatment, two once-weekly oral treatments, and a once-monthly oral pre-exposure prophylaxis that's meant to prevent HIV infection.
The company evidently has more in the works, but its name is most often in the news in relation to its blockbuster cancer drug, Keytruda. Merck announced earlier this week that it would reorganize its human health business to create a separate division for its oncology medicines ahead of Keytruda's patent cliff.
Keytruda, a type of immunotherapy used in the treatment of melanoma and other cancers, directs the body's own immune cells toward cancer cells in order to destroy them. It was revolutionary when it was first approved for medical use in 2014, and has accounted for the bulk of revenue in Merck's pharmaceutical division for years.
However, with major patents set to expire in 2028, Merck must be on the defensive. The company has been building what is known as a patent wall for its top-selling cancer medicine to cover new indications and drug combinations.
Peter Dannenbaum, Merck's senior vice president of investor relations, clarified on the latest earnings call that certain patents had been extended through 2029. Still, the company is bracing for Keytruda's loss of exclusivity in 2028, in what Dannenbaum called a "conservative estimate."
"The pharma industry is the only industry where this happens," Barr told Barron's. "Every 10 or 12 years, you lose your drug. So we have to replenish the pipeline." As he sees it, the "green shoots" of a new pipeline are starting to emerge.
"The company obviously has to translate those into successful launches, but it's a different kind of mindset these days when I meet with analysts and investors," Barr continued. "The ability to speak about all these new pipeline medicines really changes the story and hand-wringing about what's going to happen with Keytruda's LOE."
Write to Mackenzie Tatananni at mackenzie.tatananni@barrons.com
This content was created by Barron's, which is operated by Dow Jones & Co. Barron's is published independently from Dow Jones Newswires and The Wall Street Journal.
(END) Dow Jones Newswires
February 25, 2026 12:38 ET (17:38 GMT)
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