Oral R115866 in the treatment of moderate to severe plaque-type psoriasis

BACKGROUND: R115866 (Rambazole) is a new generation all-trans retinoic acid metabolism blocking agent, highly specific against the retinoic acid 4-hydroxylase. The drug alleviates hyperproliferation and normalizes differentiation of the epidermis in animal models of psoriasis. OBJECTIVE: To explore the efficacy, safety and tolerability of systemic R115866 in patients with moderate to severe plaque-type psoriasis. PATIENTS AND METHODS: In this open label, single-arm trial, patients were treated with R115866, 1 mg/day for 8 weeks, followed by a 2-week treatment-free follow-up period. Patients were monitored for efficacy and safety. RESULTS: Nineteen patients (intent-to-treat population) were treated and 14 completed the entire study. Two patients discontinued due to lack of efficacy and three due to adverse events. At the end of the treatment, 26% of the patients showed at least 50% reduction in Psoriasis Area Severity Index (PASI) compared to baseline. Further improvement was observed at the end of the 2-week follow-up period where 47% of the patients showed a 50% or greater reduction in PASI. Kinetic data showed no evidence of accumulation of either R115866 or retinoic acid in plasma. The most common adverse events were pruritus, xerosis, cheilitis and an increase in blood triglycerides. The majority of adverse events were mild to moderate. No deaths or serious adverse events were reported. CONCLUSION: Eight-week daily treatment with 1 mg R115866 resulted in a significant reduction in PASI from baseline to end of therapy. Additional improvement was seen after the 2-week follow-up period. The drug was well tolerated. R115866 merits further evaluation to optimize its clinical efficacy and safety profile in moderate to severe plaque-type psoriasis.