Safety of the muscarinic receptor-antagonist (R,R)-penehyclidine fumarate in healthy subjects: A phase 1 randomized, double-blind, single-dose escalation study

Purpose: (R,R)-penehyclidine fumarate (R2PHF) is a highly selective muscarinic receptor antagonist used to suppress glandular secretions before general anesthesia or tracheal intubation and to treat organophosphorus poisoning. This is the first-in-human study to evaluate the safety, tolerability, and pharmacokinelics of R2PHF in healthy subjects. Materials and methods: In this single-center, double-blind, randomized study, 23 subjects received escalation doses of R2PFIF (0.0625 mg, 0.25 mg, 0.50 mg, and 1.0 mg), 4 received the parent drug penehyclidine hydrochloride (PHC, 1.0 mg) as a reference, and 4 received a placebo. The phannacokinetic parameters of R2PHF were determined. Tolerability was assessed based on adverse events and clinical laboratory tests. Results: Single doses of 0.0625 mg, 0.25 mg, and 0.50 mg R2PFIF were well-tolerated by healthy subjects. Delirium was set as the termination outcome and appeared in 1 case receiving 1.0 mg. For this reason, the escalation experiment was cut off. The mean half-life (T-1/2) ranged from 30.57 to 32.27 hours. Conclusion; R2PHF was safe and well-tolerated at doses ranging from 0.0625 to 0.50 mg. A single administration of 0.50 mg was determined to be the maximum tolerated dose of R2PHF. Further pharmacodynamics, safety, and efficacy testing is required to advance R2PHF to the next stage of clinical development and application.