Topical maxacalcitol for the treatment of psoriasis vulgaris: a placebo-controlled, double-blind, dose-finding study with active comparator

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Abstract
1α, 25-Dihydroxy-22-oxacalcitriol (maxacalcitol) is a vitamin D3 analogue which displays approximately 10 times greater efficacy at suppressing keratinocyte proliferation in vitro than calcipotriol and tacalcitol. To determine clinical efficacy, a phase II double-blind, randomized, left vs. right, concentration–response study was performed with once-daily topical maxacalcitol in patients with mild to moderate chronic plaque psoriasis. Primary efficacy parameters were psoriasis severity index (PSI) based on sum of scores for erythema, scaling and induration and investigators' overall assessment of patients' response to therapy at 8 weeks of treatment. One hundred and forty-four patients participated. All concentrations of maxacalcitol ointment (6, 12.5, 25 and 50 μg/g) were significantly more effective at reducing PSI than placebo (P < 0.01), with greatest effect noted for maxacalcitol 25 μg/g. Calcipotriol ointment 50 μg/g once daily as active comparator had a similar effect. Marked improvement or clearance of psoriasis was greatest for maxacalcitol 25 μg/g (55% of subjects) which compared favourably with calcipotriol (46%). Improvement continued throughout the study period, with no plateau at week 8. Investigators' and patients' side preference (secondary efficacy parameters) rated maxacalcitol more effective than placebo and 25 μg/g maxacalcitol better than calcipotriol (P < 0.05 for investigators' assessment). Twelve patients withdrew from the study due to adverse events, of which four were judged to be due to study medication. This study indicates that once-daily maxacalcitol ointment is effective in the management of plaque psoriasis, with greatest effect noted at 25 μg/g. As no response plateau was noted at 8 weeks, these data suggest that further benefit might be obtained if maxacalcitol ointment were applied for longer. Finally, investigators' overall assessment and side preference suggest that maxacalcitol 25 μg/g may be more effective than once-daily calcipotriol.