To assess the long-term safety and efficacy of IPX203.

IPX203 is an investigational oral extended-release (ER) carbidopa-levodopa (CD-LD) that contains immediate-release (IR) granules, ER beads, and mucoadhesive polymers to prolong therapeutic LD plasma concentrations. In a Phase 3 study, IPX203 was shown to be superior to IR CD-LD for “Good On” time.

This was a 9-month, multicenter, open-label safety extension study. Parkinson’s patients with motor fluctuations who had successfully completed the Phase 3 double-blind study comparing the safety and efficacy of IPX203 with IR CD-LD were invited to enroll in this study.

Between April 3, 2019, and March 21, 2022, 419 patients were enrolled and received treatment; 352 (84%) patients completed the study; 67 (16%) discontinued. The primary reasons for discontinuation were patient withdrawal (22 [32.8%]), adverse events (AEs) (20 [29.9%]), and lack of efficacy (14 [20.9%)]. IPX203 was generally safe and well tolerated. Overall, 221 (52.7%) patients experienced treatment-emergent AEs (TEAEs). The most frequent TEAEs (≥2% patients) were dyskinesia (21 [5.0%]), fall (21 [5.0%]), urinary tract infection (21 [5.0%]), back pain (15 [3.6%]), constipation (11 [2.6%]), and COVID-19 (10 [2.4%]). The majority of TEAEs were mild or moderate in severity and occurred within the first 90 days of treatment. All efficacy measures were stable throughout the study period of 9 months. Most patients reached a stable dosing regimen by 3 months of treatment; the average daily dosing frequency of IPX203 was generally stable over the 9-month period. The average (mean [SD]) daily dosing frequency of IPX203 was 3.1 (0.45) times/day, the mean±SD daily dose of IPX203 was 1539.61±630.837 (range: 420.0, 4458.9) mg and the median (range) treatment duration was 271.0 (16, 369) days.

In this 9-month open-label extension study, IPX203 exhibited a favorable safety and tolerability profile, and efficacy was maintained from baseline to the end of the study.