Once-a-year HIV Drug In Works

Drug company Merck & Co. Inc. (NYSE: MRK) is excited about one of its new HIV drugs: islatravir (pronounced IZ-lah-trah-veer), which until last week was known as EFdA or MK-8591. The reason for the excitement is that islatravir could be the first HIV drug that can be given as a once-a-year implant. The first results from human testing of the proposed implant are being presented at the annual meeting of the International AIDS Society in Mexico City.

Islatravir is the first in a new class of drugs called nucleoside reverse transcriptase translocation inhibitors. These drugs work by blocking movement of the enzyme responsible for cloning HIV’s DNA so that it can infect new cells. Dr. Roy D. Baynes, Merck’s chief medical officer, said Islatravir is 10 times as potent as any previous HIV drug.

One of the biggest benefits of islatravir is that the drug lingers in the body for a relatively long time. Testing found that after five days, half of the dose remains. Merck’s innovation is to deliver its new drug using a matchstick-sized plastic rod inserted just under the skin that slowly releases tiny doses of the medication, just like current long-acting birth control drugs. The new implant was tested in a dozen subjects for 12 weeks.

For the study, researchers implanted six patients with an implant with a 54-milligram dose of the drug, six with a 62-mg dose, and four with a placebo implant. They then looked at the levels of the drug in the blood over time. The researcher found that the blood levels indicated that the 54-mg implant could prove effective for between eight and 10 months. The 62-mg implant was found to potentially protect against HIV infection for a year.

Larger, longer studies will need to be completed to test the safety and efficiency of the new drug. A real-world test would mean giving the implant to thousands of sexually active or drug-using men and women, and tracking how many get infected. Dr. Baynes declined to discuss any details about the next trial or to speculate on how long it would take. He also declined to discuss the eventual cost.