Safety and Pharmacokinetics of HTL0018318, a Novel M(1) Receptor Agonist, Given in Combination with Donepezil at Steady State: A Randomized Trial in Healthy Elderly Subjects

INTRODUCTION: HTL0018318 is a selective muscarinic M(1) receptor partial agonist under development for the symptomatic treatment of dementias, including Alzheimer’s disease. Clinically, HTL0018318 would likely be used alone or in conjunction with cholinesterase inhibitors (e.g. donepezil). OBJECTIVE: We investigated the safety, tolerability, and pharmacokinetics of HTL0018318 given alone and in combination with donepezil. METHODS: This was a randomized, double-blind, placebo-controlled trial in 42 (to deliver 36 with combination treatment) healthy elderly subjects investigating the effects of oral HTL0018318 15 and 25 mg given alone and combined with donepezil 10 mg at steady state on adverse events (AEs), vital signs, saliva production, sleep quality, pulmonary function, subjective feelings, and pharmacokinetics. RESULTS: AEs were reported by lower percentages of subjects after HTL0018318 alone than after donepezil alone. There was no increase in the percentage of subjects reporting AEs after co-administration than after donepezil alone. Supine systolic blood pressure was 1.6 mmHg (95% confidence interval [CI] −3.1 to −0.1) lower after HTL0018318 alone than after combination treatment. This was comparable with results from placebo alone: 1.7 mmHg (95% CI −3.2 to 0.2) lower than with combination treatment. Supine pulse rate was 3.3 bpm (95% CI 1.5–5.1) higher after HTL0018318 alone than with co-administration. HTL0018318 and donepezil did not meaningfully affect each other’s pharmacokinetics. CONCLUSION: HTL0018318 was well tolerated when given alone and in combination with donepezil. HTL0018318 and donepezil do not demonstrate pharmacokinetic or pharmacodynamic interactions, indicating that HTL0018318 can be safely administered in combination with donepezil. CLINICAL TRIAL REGISTRATION: Netherlands Trial register identifier NL5915, registered on 28 October 2016. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s40268-021-00352-5.