Merck Halts Two Phase III Trials of HIV Drug Islatravir Due to Immune Cell Count Declines

Compiled by Aspirin

MSD is currently developing a once-a-month oral antiretroviral candidate drug, islatravir, for the treatment of HIV. Last month, MSD decided to suspend two Phase II and III trials related to the development of this HIV treatment drug after investigators conducting the clinical trials found that participants experienced a drop in immune cell counts due to the treatment.

On December 6, 2021, Eastern Time, MSD announced that it would suspend patient recruitment for two Phase III trials evaluating this drug.

This decision was made after MSD accepted the recommendation of the external data monitoring committee (eDMC) for islatravir as pre-exposure prophylaxis (PrEP), leading to the suspension of recruitment for the IMPOWER 22 and IMPOWER 24 clinical trials, allowing the company to conduct further analysis of these studies. In a statement, the company announced, "Based on the recommendation of the external data monitoring committee, MSD is implementing additional monitoring measures for study participants, including increasing the frequency of total lymphocyte and CD4+ T-cell assessments."

For MSD's Decision to Halt This Anti-AIDS Drug, Investors Were Not Surprised. In a statement on December 6, Mizuho Securities told investors, "In our view, the halt was not unexpected as MSD is working to determine the true risk profile of islatravir based on its clinical data. Given our consistently neutral stance on islatravir, we are maintaining our current outlook for its prospects."

Earlier last month, MSD halted a Phase II clinical study named IMAGINE-DR, raising the first alarm about the safety of the drug. The study is testing the combination of the weekly non-nucleoside reverse transcriptase inhibitor MK-8507 and the investigational nucleoside reverse transcriptase islatravir.

Another unfortunate piece of news in the field of anti-AIDS drug research is that Gilead, a pharmaceutical giant and partner of MSD in anti-AIDS efforts, has also announced the suspension of patient recruitment for a separate study out of caution. This study involves one of the investigational drugs used in MSD's standalone trial.

Islatravir is one of the two core drugs in the long-acting HIV therapy jointly developed by MSD and Gilead, with the other core drug being Gilead's capsid inhibitor lenacapavir.

Reference Source: MSD Pumps the Brakes on Two More PhIII Trials for Its Lead Anti-HIV Drug