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Merck's (MRK) HIV Studies on Islatravir Put on Clinical Hold

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Merck (MRK - Free Report) announced that the FDA has placed clinical holds on further studies evaluating its once-monthly investigational nucleoside reverse transcriptase translocation inhibitor, oral islatravir (MK-8591) for the treatment and prevention of HIV-1 infection.

The decision was taken based on observations of decreases in total lymphocyte and CD4+ T-cell counts in some study participants in previous clinical studies on islatravir.

Last month, Merck announced that dosing was stopped in the phase II study (IMAGINE-DR) evaluating the combination of MK-8507 and islatravir as a treatment for people living with HIV-1. The dosing was stopped at the recommendation of an eDMC, which observed decreases in total lymphocyte and CD4+ T-cell counts in study participants randomized to receive islatravir plus MK-8507, which the eDMC determined was related to treatment with the combination of islatravir+MK-8507.

Last week, Merck paused enrollment in two phase III studies evaluating islatravir for pre-exposure prophylaxis (PrEP) of HIV-1 infection. Enrollment in the IMPOWER 22 and IMPOWER 24 studies was also stopped at the recommendation of the ISL PrEP eDMC.

The latest clinical holds are on the investigational new drug applications (INDs) for the oral and implant formulations of islatravir for HIV-1 PrEP; the injectable formulation of islatravir for HIV-1 treatment and prophylaxis; and oral doravirine/islatravir (DOR/ISL) HIV-1 once-daily treatment. With the FDA’s clinical hold in place, no new studies can be initiated on islatravir.

While six studies on islatravir have been placed on full clinical hold, seven have been put on partial clinical hold. Merck was evaluating islatravir as a treatment for HIV-1 infection in combination with other antiretrovirals

Merck’s stock has declined 3.5% this year so far against an increase of 18.4% for the industry.

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This year, Merck collaborated with Gilead (GILD - Free Report) to evaluate the combination of islatravir with the latter’s lenacapavir to develop long-acting HIV treatment options. In October, Gilead and Merck initiated a phase II study evaluating the combination of a once-weekly treatment regimen of islatravir and lenacapavir in people living with HIV who are virologically suppressed on antiretroviral therapy.

Merck and Gilead have decided to stop all dosing of participants in the above-mentioned phase II study.

Glaxo (GSK - Free Report) is another key player in the HIV market other than Merck and Gilead. Glaxo has developed its PrEP candidate for HIV, cabotegravir. Glaxo has already submitted a regulatory application to the FDA seeking approval for cabotegravir for PrEP and expects to receive a decision in January 2022.

A long-acting injectable regimen of Glaxo’s cabotegravir and J&J’s (JNJ - Free Report) Edurant (rilpivirine) for the treatment of HIV-1 infection in virologically suppressed adults was approved by the FDA in January 2021. The combination is being marketed under the trade name Cabenuva.

Cabenuva has been co-developed by J&J’s pharmaceutical subsidiary, Janssen and Glaxo’s HIV subsidiary, ViiV Healthcare.

Merck currently carries a Zacks Rank #3 (Hold). You can see the complete list of today’s Zacks #1 Rank (Strong Buy) stocks here.