Peripheral selectivity of the novel cannabinoid receptor antagonist TM38837 in healthy subjects.

Aim: Cannabinoid receptor type 1 (CB1 ) antagonists show central side effects, whereas beneficial effects are most likely peripherally mediated. In this study, the peripherally selective CB1 antagonist TM38837 was studied in humans.

Methods: This was a double-blind, randomized, placebo-controlled, crossover study. On occasions 1-4, 24 healthy subjects received 5 × 4 mg THC with TM38837 100 mg, 500 mg or placebo, or placebos only. During occasion 5, subjects received placebo TM38837 + THC with rimonabant 60 mg or placebo in parallel groups. Blood collections and pharmacodynamic (PD) effects were assessed frequently. Pharmacokinetics (PK) and PD were quantified using population PK-PD modelling.

Results: The TM38837 plasma concentration profile was relatively flat compared with rimonabant. TM38837 showed an estimated terminal half-life of 771 h. THC induced effects on VAS feeling high, body sway and heart rate were partly antagonized by rimonabant 60 mg [-26.70% [90% confidence interval (CI) -40.9, -12.6%]; -7.10%, (90%CI -18.1, 5.3%); -7.30%, (90% CI -11.5%, -3.0%) respectively] and TM38837 500 mg [-22.10% (90% CI -34.9, -9.4%); -12.20% (90% CI -21.6%, -1.7%); -8.90% (90% CI -12.8%, -5.1%) respectively]. TM38837 100 mg had no measurable feeling high or body sway effects and limited heart rate effects.

Conclusions: Rimonabant showed larger effects than TM38837, but the heart rate effects were similar. TM38837 100 mg had no impact on CNS effects, suggesting that this dose does not penetrate the brain. This TM38837 dose is predicted to be at least equipotent to rimonabant with regard to metabolic disorders in rodent models. These results provide support for further development of TM38837 as a peripherally selective CB1 antagonist for indications such as metabolic disorders, with a reduced propensity for psychiatric side effects.