Objective: OPC-28326 is a selective alpha-adrenergic antagonist with preferential binding to the alpha(2C)-adrenergic receptor (alpha(2C)-AR) subtype. This study observed the effect of OPC-28326 on skin temperature and digital blood flow following an acute cold challenge in patients with Raynaud's phenomenon secondary to scleroderma.
Methods: The study was designed as a single-center, double-blind, placebo-controlled, randomized, 3-period crossover study of OPC-28326 (oral doses of 10 mg or 40 mg) or placebo. The primary outcome measures were the time to recover 50% and 70% of the fall (induced by cold challenge) in baseline digital skin temperature.
Results: Twelve of 13 enrolled patients completed the study. The mean time to achieve 50% and 70% recovery of the change in prechallenge digital skin temperature was shorter after the OPC-28326 40-mg dose than after placebo (50% recovery at 5.8 minutes versus 10.0 minutes [P = 0.02]; 70% recovery at 13.8 minutes versus 19.5 minutes [P = 0.01]). These recovery times tended to be shorter in the 10 mg OPC-28326 group as well, but the difference versus placebo was not significant (50% recovery at 9.0 minutes versus 10.0 minutes [P = 0.65]; 70% recovery at 15.3 minutes versus 19.5 minutes [P = 0.07]). Total digital blood flow tended to be lower prior to the cold challenge and after administration of 40 mg OPC-28326, as compared with that after placebo, but the difference was not significant. Symptoms that were potentially drug-related were reported more frequently with 40 mg OPC-28326 than with 10 mg OPC-28326 or with placebo, but none were serious or sustained.
Conclusion: OPC-28326 at doses of 10 mg and 40 mg was well tolerated during this study. The shorter time to skin temperature recovery after 40 mg OPC-28326 suggests that selective alpha(2C)-AR blockade improves digital skin perfusion during recovery from cooling in patients with Raynaud's phenomenon secondary to scleroderma.