Gilead Sciences and Merck (MSD) have reported data from a Phase II clinical trial where a combination of islatravir and lenacapavir demonstrated potential in maintaining viral suppression in virologically controlled adult HIV patients.

Islatravir is an investigational nucleoside reverse transcriptase translocation inhibitor while lenacapavir is a capsid inhibitor.

The active-controlled, open-label trial enrolled virologically suppressed adults who are receiving treatment with bictegravir 50mg, emtricitabine 200mg, and tenofovir alafenamide 25mg tablets (B/F/TAF or Biktarvy).

Participants were randomised into a 1:1 ratio to receive either the oral combination of islatravir and lenacapavir once a week or to continue with their daily oral Biktarvy treatment.

The primary endpoint focused on the level of HIV-1 RNA at ≥50 copies/mL in the blood at week 24.

Findings showed that 1.9% of the subjects in the islatravir plus lenacapavir arm had a viral load of more than 50 copies/mL at week 24 with the subject later suppressed on the treatment at week 30.

Furthermore, 94.2% of participants treated with islatravir and lenacapavir maintained viral suppression, a key secondary endpoint.

The trial's findings are boosted by the pharmacokinetic profiles of the two drugs, suggesting their viability as a once-weekly oral regimen.

Treatment-related adverse events were minimal, with only Grade 1 and 2 events such as dry mouth and nausea reported in the islatravir and lenacapavir group.

The study is set to continue in an open-label manner until week 48.

Sold under the brand name Sunlenca, lenacapavir is approved in several countries, including Australia, the EU, Canada, Japan, Switzerland, Israel, the UAE, the UK, and the US, for multi-drug resistant HIV, along with other antiretrovirals.

Gilead Sciences HIV Clinical Development vice-president Jared Baeten said: “HIV treatment is not one size fits all – developing once-weekly treatment options could help meet the needs of each individual, aiming toward maximising long-term outcomes for people with HIV.

“These promising data presented at CROI help bring us one step closer to our goal of providing a wide range of options that may help transform the HIV treatment landscape.” 

In March 2021, the companies entered an agreement for the joint development and marketing of long-acting treatments for HIV.