Progress in the development of histamine H3 receptor antagonists/inverse agonists: a patent review (2013-2017)

INTRODUCTION

Since years, ligands blocking histamine H₃ receptor (H₃R) activity (antagonists/inverse agonists) are interesting targets in the search for new cures for CNS disorders. Intensive works done by academic and pharmaceutical company researchers have led to many potent and selective H₃R antagonists/inverse agonists. Some of them have reached to clinical trials.

AREAS COVERED

Patent applications from January 2013 to September 2017 and the most important topics connected with H₃R field are analysed. Espacenet, Patentscope, Pubmed, GoogleScholar or Cochrane Library online databases were principially used to collect all the materials.

EXPERT OPINION

The research interest in histamine H₃R field is still high although the number of patent applications has decreased during the past 4 years (around 20 publications). Complexity of histamine H₃R biology e.g. many isoforms, constitutive activity, heteromerization with other receptors (dopamine D₂, D₁, adenosine A_2A) and pharmacology make not easy realization and evaluation of therapeutic potential of anti-H₃R ligands. First results from clinical trials have verified potential utility of histamine H₃R antagonist/inverse agonists in some diseases. However, more studies are necessary for better understanding of an involvement of the histaminergic system in CNS-related disorders and helping more ligands approach to clinical trials and the market. Lists of abbreviations: hAChEI - human acetylcholinesterase inhibitor; hBuChEI - human butyrylcholinesterase inhibitor; hMAO - human monoamine oxidase; MAO - monoamine oxidase.

The European Medicines Agency review of pitolisant for treatment of narcolepsy: summary of the scientific assessment by the Committee for Medicinal Products for Human Use

On 31 March 2016, the European Commission issued a decision for a marketing authorisation valid throughout the European Union (EU) for pitolisant (Wakix) for the treatment of narcolepsy with or without cataplexy in adults. Pitolisant is an antagonist/inverse agonist of the human histamine H3 receptor. The dose should be selected using an up-titration scheme depending on individual patient response and tolerance and should not exceed 36 mg/day. The main evidence of efficacy of pitolisant was based on two Phase III clinical trials. The improvement on excessive daytime sleepiness was shown against placebo in the Harmony I study (-3.33 points; 95% confidence interval (CI) [-5.83; -0.83]; p = 0.024) and in Harmony CTP (-3.41 points; 95% CI [-4.95; -1.87]; p < 0.0001). The daily cataplexy rate in Harmony I improved against placebo with a rate ratio (rR) of 0.38 whilst in the Harmony CTP the ratio of improvement on weekly cataplexy rate against placebo was 0.512. The most commonly reported adverse reactions were headache, insomnia and nausea. This article summarizes the scientific review leading to approval of pitolisant in the EU. The assessment report and product information are available on the European Medicines Agency website (http://www.ema.europa.eu).