Safety, Pharmacokinetics, and Biomarkers of an Amorphous Solid Dispersion of Genistein, a Radioprotectant, in Healthy Volunteers

A pharmaceutical formulation of genistein, produced as an amorphous solid dispersion by hot melt extrusion (genistein HME), has been developed that can be administered prophylactically to improve outcomes and survival following radiation exposure. Here, genistein HME was evaluated in a phase 1, open‐label, single ascending dose (SAD) and multiple single dose (MSD) study enrolling 34 healthy volunteers. In the SAD study, participants were administered a single dose (500, 1000, 2000, or 3000 mg) and in the MSD study, participants were administered a single daily dose for six consecutive days (3000 mg/day). The overall adverse event profile and pharmacokinetics of genistein HME were determined. Additionally, biomarkers of genistein HME were evaluated by profiling whole blood for changes in gene expression by RNA sequencing. Genistein HME was found to be safe at doses up to 3000 mg. Most toxicities were mild to moderate gastrointestinal events, and no dose‐limiting toxicities were reported. The maximum tolerated dose was not determined and the no observable adverse effect level was 500 mg. Genistein HME bioavailability greatly increased between the 2000 mg and 3000 mg doses. RNA sequencing analysis revealed that the majority of drug‐related changes in gene expression occurred 8–12 hours after the sixth dose in the MSD study. Based on these results, the putative effective dose in humans is 3000 mg.