Merck shares results of Islatravir as PrEP trial

Pharmaceutical company, Merck, presented the results of a Phase-II trial of islatravir, a long-acting drug, for the treatment and prevention of HIV, at the 11th International Scientific Conference IAS 2021 (IAS 2021).

Research

The small Phase-II trials looked at two doses of islatravir (ISL), 60mg and 120mg, for pre-exposure prophylaxis (PrEP) in 242 people. Two thirds of the study participants were women.

Participants received ISL orally once a month for six months. After six months the treatment was stopped, but researchers continued to monitor the participants. Even two months after the last dose of ISL there was still protective amounts of drug in participants blood samples. The researchers will continue to monitor the patients for a further eight months to assess the effectiveness of ISL and its elimination rate from the body.

Results 

No new HIV infections were recorded during the trial. Oral ISL at both 60mg and 120mg were well tolerated by participants for the 24 weeks of the trial and reached a predetermined threshold for HIV prevention.

Additionally, no serious adverse events were reported by participants, although more than half (60%) reported some side effects - the most common were headache (9%), diarrhoea (5%), and nausea (5%). However the frequency of side effects was higher in the placebo group than in both the combined ISL groups, which suggests that “these are things that occur in normal life and are not necessarily caused by the drug” said one expert.

Future plans

Merck are developing and testing various doses and dosing methods of islatravir for use both on its own and combined with other antiretroviral drugs for the treatment and prevention of HIV.

Merck has already partnered with Gilead Sciences to combine their long-acting drugs, islatravir and lenacapavir, into a single formulation for oral and injectable use. Clinical trials are expected to start in the second half of 2021.