Selisistat, a selective SirT1 inhibitor is being developed as a potentially disease‐modifying therapeutic for Huntington's disease (HD). This was the first study of selisistat in HD patients and was primarily aimed at development of pharmacodynamic biomarkers.

This was a randomized, double‐blind, placebo‐controlled, multicentre exploratory study. Fifty‐five male and female patients in early stage HD were randomized to receive 10 mg or 100 mg of selisistat or placebo once daily for 14 days. Blood sampling, clinical and safety assessments were conducted throughout the study. Candidate pharmacodynamic markers included circulating soluble huntingtin and innate immune markers.

Selisistat was found to be safe and well tolerated, and systemic exposure parameters showed that the average steady‐state plasma concentration achieved at the 10 mg dose level (125 nm) was comparable with the IC₅₀ for SirT1 inhibition. No adverse effects on motor, cognitive or functional readouts were recorded. While circulating levels of soluble huntingtin were not affected by selisistat in this study, the biological samples collected have allowed development of assay technology for use in future studies. No effects on innate immune markers were seen.

Selisistat was found to be safe and well tolerated in early stage HD patients at plasma concentrations within the anticipated therapeutic concentration range.