2.244 PHARMACOKINETICS, PHARMACODYNAMICS AND TOLERABILITY OF OPICAPONE, A NOVEL COMT INHIBITOR, DURING FIRST ADMINISTRATION TO HEALTHY MALE SUBJECTS

Opicapone: a short lived and very long acting novel catechol-O-methyltransferase inhibitor following multiple dose administration in healthy subjects

AIMS

The aim of this study was to assess the tolerability, pharmacokinetics and inhibitory effect on erythrocyte soluble catechol-O-methyltransferase (S-COMT) activity following repeated doses of opicapone.

METHODS

This randomized, placebo-controlled, double-blind study enrolled healthy male subjects who received either once daily placebo or opicapone 5, 10, 20 or 30 mg for 8 days.

RESULTS

Opicapone was well tolerated. Its systemic exposure increased in an approximately dose-proportional manner with an apparent terminal half-life of 1.0 to 1.4 h. Sulphation was the main metabolic pathway. Opicapone metabolites recovered in urine accounted for less than 3% of the amount of opicapone administered suggesting that bile is likely the main route of excretion. Maximum S-COMT inhibition (Emax ) ranged from 69.9% to 98.0% following the last dose of opicapone. The opicapone-induced S-COMT inhibition showed a half-life in excess of 100 h, which was dose-independent and much longer than plasma drug exposure. Such a half-life translates into a putative underlying rate constant that is comparable with the estimated dissociation rate constant of the COMT-opicapone complex.

CONCLUSION

Despite its short elimination half-life, opicapone markedly and sustainably inhibited erythrocyte S-COMT activity making it suitable for a once daily regimen.

Catechol‐O‐Methyl‐Transferase Inhibitors: Present Problems and Relevance of the New Ones

Levodopa, in association with a DOPA decarboxylase inhibitor (e.g., carbidopa or benserazide) has for many years been the undisputed gold standard drug for the symptomatic treatment of Parkinson’s disease (PD). However, given its rapid disposition and elimination in the periphery, it was hypothesized that significant enhancements in levodopa bioavailability and clinical efficacy could be achieved through co‐adjuvant therapy with a catechol‐O‐methyl‐transferase (COMT) inhibitor. Early attempts, dating back to the late 1950s, to discover COMT inhibitors were generally hampered by their lack of in vivo efficacy, target selectivity or by considerable toxicity. It was not until the late 1990s that entacapone and tolcapone, representatives of a new class of potent COMT inhibitors (nitrocatechol derivatives), made their way to clinical practice for the treatment of PD. Even though these drugs have since contributed to an increase in the usefulness of levodopa therapy, each of them presents known limitations, namely concerning their clinical efficacy and safety. The unmet medical need for more efficacious and safer COMT inhibitors has motivated intense research in this field over the last decade. Opicapone is the first, third‐generation COMT inhibitor among the nitrocatechol derivatives under clinical development, and demonstrates superior pharmacodynamic and safety profiles in humans, over previous drugs. In this chapter, we review the major advances in this field, summarize the relevant non‐clinical and clinical human pharmacology and discuss new insights into the mechanism of action of opicapone.