July 21 (Reuters) - Gilead Sciences (GILD.O) and Merck (MRK.N) said on Tuesday their experimental once-weekly HIV pill kept the virus suppressed in two late-stage trials, supporting regulatory filings for what could become the first regimen of its kind for the disease.

Here are some details:

The combination of Merck’s islatravir and Gilead’s lenacapavir was tested as a single-tablet regimen in adults whose HIV was already controlled with daily antiretroviral therapy.
HIV attacks the body’s immune system and, if left untreated, can progress to acquired immunodeficiency syndrome (AIDS), the most advanced stage of infection.
In one trial, none of the patients who switched to the weekly pill had detectable viral levels at 48 weeks, compared with 0.3% of those who remained on Gilead’s daily Biktarvy.
In a second trial, 0.3% of patients taking the weekly pill had detectable HIV levels or higher at 48 weeks, compared with 1.3% of those who remained on standard daily HIV regimens.
Investors are closely watching the rollout of lenacapavir, branded as Yeztugo, which was approved last year, as Gilead seeks to strengthen its HIV franchise alongside blockbuster treatment Biktarvy.
The companies said the weekly treatment was non-inferior to Biktarvy and other daily HIV regimens in the two studies, meaning it performed at least as well by the studies’ main measure.
Side effects were generally similar to the daily treatments studied, and no new safety concerns were identified. The most common treatment-related side effects included headache, nausea and diarrhea.
Merck’s once-daily HIV pill combo Idvynso was approved by the U.S. Food and Drug Administration in April, bringing another treatment option for patients suffering from the condition.