Development and validation of a LC-MS/MS method for the quantification of the E-type prostanoid receptor 4 antagonist HTL0039732 in human plasma, for a Phase I/IIa clinical trial

BACKGROUND: HTL0039732 (HTL) is a novel E-type prostanoid receptor 4 (EP4) antagonist for the treatment of advanced solid tumors. An analytical method was developed to facilitate the analysis of patient samples as part of an ongoing Phase I/IIa clinical trial. METHODS AND RESULTS: A LC-MS/MS method for quantifying HTL in human plasma was developed and validated per regulatory guidelines. The assay was selective, with a 2 ng/mL detection limit observed. It demonstrated good precision (CV ≤11.9%) and accuracy (86-101%), with linearity from 10 to 2000 ng/mL. Recovery was consistent, and no significant matrix, anticoagulant, or carryover effects were observed. CONCLUSIONS: A sensitive and selective method for measuring HTL in human plasma was successfully developed and applied to clinical samples, generating first‑in‑human pharmacokinetic data for HTL. The assay is now being utilized in an early‑phase clinical trial setting. CLINICAL TRIAL REGISTRATION: https://clinicaltrials.gov/study/NCT05944237.