Tolcapone

Parkinson's disease is a chronic neurodegenerative disease entity characterized by heterogeneity of symptoms and progression. Levodopa is an efficacious and well tolerated dopamine substituting drug for its therapy. Its O-methylation and generation of 3-O-methyldopa is enhanced by levodopa/dopa decarboxylase inhibitor formulations. Additional inhibition of catechol-O-methyltransferase is the relevant add on therapy for levodopa application. This pharmacologic approach increases the plasma appearance of levodopa and reduces 3-O-methyldopa synthesis. Available marketed compounds are entacapone, tolcapone and opicapone. Data on their effects on levodopa pharmacokinetics in patients are rare.

This review describes the impact of this add-on therapy on the pharmacokinetic profile of levodopa and 3-O-methyldopa in plasma. The rationale was to perform a comparison with data from previously published pharmacokinetic trials with a standardized one time intake of levodopa/carbidopa without and with the available catechol-O-methyltransferase inhibitors.

Results of this analysis identified opicapone as the most efficacious inhibitor of catechol-O-methyltransferase in terms of changes of levodopa plasma concentrations. Opicapone induced higher levodopa plasma levels compared with the ones following application of levodopa/carbidopa alone or combined with entacapone or tolcapone. Co-administration of opicapone with its once daily intake regimen may support the efficacy of subcutaneous and intrajejunal levodopa infusions.

Comprehending early amyloidogenesis is essential for the development of effective therapeutic strategies. In tauopathies like Alzheimer's disease (AD), the abnormal accumulation of tau protein is initiated by pathological tau seeds. Mounting evidence implies that the microtubule binding domain, consisting of three to four repeats, plays a pivotal role in this process, yet the exact region driving the formation of pathogenic species needs to be further scrutinized. Here, we chemically synthesized individual tau repeats to identify those exhibiting pathogenic prion‐like characteristics. Notably, repeat 3 (R3) displayed a remarkable propensity to polymerize, form toxic filaments, and induce cognitive impairment, even in the absence of an aggregation‐promoting inducer, highlighting its physiological relevance. Additionally, oligomeric R3 was identified as a particularly pathological form, prompting the establishment of a screening platform. Through screening, tolcapone was found to possess therapeutic efficacy against pathological tau aggregates in PS19 transgenic mice. This screening platform provides a valuable avenue for identifying compounds that selectively interact with peptides implicated in the progression of tauopathies.