Cysteamine bitartrate: Phase II/III data
Top-line data from a double-blind, French Phase II/III trial in 96 stage I/II patients showed that RP103 missed the primary endpoint of reducing progression of TMS score from baseline at 18 months vs. placebo (4.51 vs. 6.68 points, p=0.19). A higher TMS score indicates more severe disease progression. RP103 did significantly improve the endpoint in a subgroup of patients not taking concurrent Xenazine tetrabenazine (n=66) vs. placebo (2.84 vs. 6.78 points, p=0.03). Patients were permitted to continue receiving their prescribed medication regime, including Xenazine, for chorea associated with HD.
On a conference call to discuss the data, Raptor said that Xenazine could have a "masking effect" on RP103 by affecting patient behavior during evaluations. Of the 89 patients who completed the trial, there were 12 (26%) Xenazine-treated patients in the RP103 arm vs. 11 (25.5%) in the placebo arm. Xenazine from H. Lundbeck A/S (CSE:LUN, Copenhagen, Denmark) is the only FDA-approved drug for chorea associated with HD. ...