Long-term outcomes associated with istradefylline versus catechol-O-methyltransferase inhibitors in patients with Parkinson's disease: a nationwide real-world cohort study.

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BackgroundIstradefylline, a selective adenosine A2A receptor antagonist, is approved as an adjunct to levodopa in Parkinson's disease, but its long-term effects on clinically meaningful outcomes are unclear.ObjectiveWe aimed to compare the association of istradefylline versus catechol-O-methyltransferase (COMT) inhibitors with mortality, treatment escalation, and disease progression in levodopa-treated Parkinson's disease.MethodsWe conducted a nationwide cohort study emulating a target trial using the DeSC claims database in Japan. Patients aged ≥50 years with levodopa-treated Parkinson's disease between 2014 and 2023 were included. Strategies were initiation of istradefylline versus COMT inhibitors. Primary outcomes were all-cause mortality, levodopa-equivalent daily dose (LEDD) escalation to ≥1100 mg, and dementia or psychosis. Secondary outcomes were fractures, cardiovascular events, pneumonia, and depression. Intention-to-treat and per-protocol effects were estimated using Cox models with propensity score-based overlap weighting.ResultsWe identified 3190 istradefylline and 7986 COMT inhibitor initiators. In intention-to-treat analysis, istradefylline was associated with lower risks of mortality (hazard ratio [HR] 0.91; 95 % CI 0.84-0.99) and LEDD escalation (HR 0.83; 95 % CI 0.73-0.94). Associations were stronger in per-protocol analysis (mortality: HR 0.84, 95 % CI 0.72-0.97; LEDD escalation: HR 0.71, 95 % CI 0.59-0.84). Istradefylline was linked to higher fracture risk (intention-to-treat HR 1.13, 95 % CI 1.02-1.25; per protocol HR 1.23, 95 % CI 1.07-1.41). No differences were observed for dementia, psychosis, or other outcomes.ConclusionsIstradefylline was associated with reduced mortality and treatment escalation but increased fracture risk compared with COMT inhibitors, supporting further evaluation of adenosine A2A antagonists.

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