The Safety, Tolerability, Pharmacokinetics and Cognitive Effects of GSK239512, a Selective Histamine H3 Receptor Antagonist in Patients with Mild to Moderate Alzheimer’s Disease: A Preliminary Investigation

Pradeep      J. Nathan; Rebecca      Boardley; Nicola      Scott; Alienor      Berges; Paul      Maruff; Tharani      Sivananthan; Neil      Upton; Martin      T. Lowy; Peter      J. Nestor; Robert      Lai

doi:10.2174/1567205011310030003

Abstract

Background: The histamine H₃ receptor plays a critical role in the negative neuromodulation of neurotransmitters involved in cognitive function. H₃ receptor antagonists/inverse agonists have been shown to exert pro-cognitive effects in pre-clinical models. GSK239512 is a potent and selective H₃ receptor antagonist developed for the treatment of cognitive dysfunction in neurodegenerative disorders. In this study we examined the safety, tolerability, pharmacokinetics and pro-cognitive effects of GSK239512 (oral) in patients with mild to moderate Alzheimer’s disease using ascending dose titration regimens.

Methods: The study was conducted in two parts. Part A was a single-blind, placebo run-in, flexible dose titration over 9 days in two cohorts, each consisting of two patients. Part B was a double-blind, randomised, placebo controlled, parallel group, which investigated 3 flexible dose titration regimens over 4 weeks in 3 cohorts, each consisting of eight patients.

Results: Overall, the 5/10/20/40μg and 10/20/40/80μg regimens were well-tolerated. The regimen of 20/40/80/150μg showed the poorest tolerability likely due to the higher starting dose. There were no clinically significant abnormalities in haematology, clinical chemistry, urinalysis parameters and cardiovascular parameters. GSK239512 had positive effects on tasks of attention and memory with effect sizes between 0.56 and 1.37.

Conclusions: GSK239512 displayed asatisfactory level of tolerability in patients with Alzheimer’s disease with evidence for positive effects on attention and memory. The findings suggest that a titration regimen with a starting dose of 5-10μg and a maximum dose of 80μg is likely to be a well-tolerated and potentially efficacious regimen for future clinical trials in patients with Alzheimer’s disease. These findings await replication in a larger study.

Keywords: Alzheimer’s disease, attention, cognition, H₃ receptor, histamine, antagonist, memory, safety, tolerability