Objective: To investigate if duration of benefit (“Good On” time) per dose during immediate-release (IR) carbidopa-levodopa (CD-LD) treatment predicts response to IPX203 conversion.

Background: Levodopa’s limited opportunity for absorption in the proximal small intestine, its short plasma half-life, and the progressive loss of dopaminergic neurons available to convert, store, and release levodopa-derived dopamine contribute to motor fluctuations in Parkinson’s disease (PD). IPX203, a new oral extended-release (ER) CD-LD capsule, was developed to address levodopa’s limited absorption window and short plasma half-life.

Method: We performed post-hoc analyses on Hauser diary data from the 495 subjects that completed the RISE-PD Phase 3 clinical trial. The trial had a 3-week open-label IR CD-LD dose optimization phase and a 4-week open-label dose conversion phase to IPX203, followed by a 13-week, randomized, double-blind maintenance phase with two parallel arms: IR CD-LD and IPX203. For this analysis, the patient population was rank-ordered and then divided into quartiles based on their “Good On” time per dose at the end of the IR CD-LD dose optimization. The mean end of study “Good On” time per dose values were then compared between IPX203 and IR CD-LD treated groups for each quartile.

Results: Mean “Good On” time per dose for each quartile of the IR CD-LD dose optimization phase was 1.35, 1.91, 2.36, and 2.96 hours. For patients randomized to IR CD-LD, the end of study mean “Good On” time per dose values were 1.71, 2.06, 2.34, and 2.93 hours. In patients randomized to IPX203, the end of study mean “Good On” time per dose values were 3.16, 3.44, 4.02, and 4.55 hours. The mean differences in “Good On” time per dose between IPX203 and IR CD-LD were 1.53h for quartile one, 1.38h for quartile two, 1.85h for quartile three, and 1.56h for quartile four.

Conclusion: Regardless of the duration of efficacy observed with IR CD-LD, measured as “Good On” per dose, the improvement in duration of benefit observed with IPX203 remained similar, with a range of about 1.38 to 1.85 hours for the four quartiles and an overall mean of 1.58 additional hours compared to IR treatment. These results may help care providers plan conversion regimens and anticipate clinical responses.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/what-change-to-expect-in-duration-of-benefit-per-dose-when-switching-from-ir-cd-ld-to-ipx203-er-cd-ld/