The US Phase 2a trial

A second Phase 2a trial of rentosertib has been running in the United States since February 2024, in parallel with the completed Chinese trial. It has never reported results, and its current status is genuinely unclear.

What was planned

The trial is registered as NCT05975983. It set out to enrol about 40 people with idiopathic pulmonary fibrosis (IPF) across 12 sites in the United States, randomised between rentosertib tablets taken once daily and placebo. The tablet strength has never been disclosed.

As in the Chinese trial, the main measure is the percentage of participants who have at least one side effect during treatment. Secondary measures include blood levels of two of the drug’s breakdown products, INS018_063 and INS018_095, neither of which has been publicly characterised.

The first participant was dosed on 8 February 2024.

Who is running it

The lead investigator is Professor Toby Maher, who is based at the Keck School of Medicine at the University of Southern California and was previously at the Royal Brompton Hospital in London. He is a paid investigator on this trial, and a supportive quotation from him about rentosertib appears in Insilico Medicine’s own press release.

Where it has got to

• ClinicalTrials.gov still lists the trial as recruiting.
• In June 2025, Insilico told Genetic Engineering & Biotechnology News that 22 people had been screened and 8 enrolled, against a target of 40.
• The registry’s estimated completion date of 28 February 2026 has passed without results being posted or the date being revised.
• Insilico’s 2025 annual results in March 2026 did not mention the trial.
• No update of any kind has appeared since November 2025.

Sixteen months after the first dose, the trial had enrolled a fifth of its target. Whether it is still recruiting, has been paused, or has been quietly abandoned is not known. Insilico has not said, and the registry entry has not been updated to clarify.

What this means

The Chinese Phase 2a trial was in an entirely Chinese population, and the authors of its published paper said that trials in more diverse populations were needed. This US trial was the obvious place for that to happen. Its apparent stall means that, as of September 2026, there is still no published data on rentosertib in anyone outside China, and the Phase 3 trial that began in September 2026 is also China-only.