FDA Places Clinical Hold on Gilead's HIV Combination Therapy Trials

Gilead Sciences faces a setback in its HIV drug development program as the U.S. Food and Drug Administration (FDA) has imposed a clinical hold on multiple trials testing the company's experimental HIV combination therapy. The decision, announced on June 10, 2025, has prompted a decline in Gilead's stock price and raised concerns about the future of these potential treatments.

Clinical Trials Affected and Safety Concerns

The FDA's clinical hold impacts five separate trials involving two investigational drugs: GS-1720, an integrase strand transfer inhibitor, and GS-4182, a capsid inhibitor. The affected studies include two phase 2/3 trials, known as WONDERS-1 and WONDERS-2, as well as three phase 1 studies.

Gilead reported that the hold was implemented following the identification of a safety signal in a subset of participants receiving the combination of GS-1720 and GS-4182. Specifically, decreases in CD4+T-cell (CD4) and absolute lymphocyte counts were observed, potentially indicating a compromise of the immune system and a possible worsening of the disease state.

Impact on Gilead and Future Plans

In response to the FDA's decision, Gilead's shares fell approximately 2% to $110.71 by mid-morning on the day of the announcement. The company has stated its intention to investigate the issues underlying the clinical hold and work with regulatory authorities to resolve them.

Gilead emphasized that this setback does not affect its clinical work on other long-acting oral and injectable investigational HIV treatment combinations. However, no timeline has been provided for the potential resumption of the halted trials.

The WONDERS-1 and WONDERS-2 trials were designed to compare the safety and efficacy of the GS-1720 and GS-4182 combination against Gilead's approved once-daily HIV pill, Biktarvy. WONDERS-1 focused on virologically suppressed individuals with HIV, while WONDERS-2 targeted HIV patients who had not previously received treatment.

As the pharmaceutical industry closely watches these developments, Gilead's ability to address the safety concerns and advance its HIV drug pipeline will be crucial for maintaining its position in the competitive HIV treatment market.