Objective: To analyze dosing regimen data from a Phase 3 study in order to identify an optimal dose conversion from IR CD-LD to IPX203 for use in clinical practice.

Background: IPX203 is an extended-release, oral CD-LD formulation designed to rapidly achieve therapeutic LD plasma concentrations and to maintain LD concentrations for a longer duration with less peak-to-trough variations than currently approved oral CD-LD products.

Method: RISE-PD was a randomized, double-blind, active-controlled, Phase 3 study of the safety and efficacy of IPX203 vs IR CD-LD in PD patients with motor fluctuations. All patients underwent 3 weeks of IR CD-LD dose adjustment, a 4-week open-label conversion to IPX203, followed by randomization to a 13-week double-blind treatment with IR CD-LD or IPX203. The initial dose of IPX203 during the open-label dose conversion was based on the most frequent individual dose of the patient’s stable dosing of IR CD-LD at the end of the dose adjustment period. The conversion ratio of IR CD-LD to IPX203 was 2.8, and IPX203 was administered approximately every 8 hours for most patients.

Results: Five hundred eighty-nine patients were enrolled into the IPX203 conversion period. The mean daily dosing frequency was 2.9 times/day at the start and 3.0 times/day at the end of the IPX203 conversion period. Fifty-four of 589 patients who entered the dose conversion period started on BID dosing, 31 (57%) remained on twice a day IPX203 through the end of the dose conversion period, 21 (39%) increased to TID dosing, and 2 (4%) increased to QID dosing. Of the 425 patients who started on TID dosing, 52 (12%) increased to QID dose frequency. The most frequent individual dose of IPX203 was 464.0 mg at the start and 491.1 mg at the end of the IPX203 conversion period. The average number of titration steps to stable dosing of IPX203 was 1.6. The ratio of stable IPX203 total daily dose to stable IR CD-LD total daily dose was 1.79. The ratio of most frequent stable individual IPX203 dose to IR CD-LD dose was 2.92.

Conclusion: At the end of dose conversion, average individual IPX203 doses were close to doses at the start of dose conversion despite the dosing frequency restrictions in the study. Dose conversion based on most frequent individual LD dose may facilitate the conversion process in clinical practice; dosing frequency may be adjusted to address patient’s motor fluctuations as needed.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/ipx203-dose-conversion-from-immediate-release-carbidopa-levodopa-in-parkinsons-disease-patients-with-motor-fluctuations/