A phase I randomized trial to assess the effect on skin infiltrate thickness and tolerability of topical phosphodiesterase inhibitors in the treatment of psoriasis vulgaris using a modified psoriasis plaque test.

Background: Oral phosphodiesterase (PDE)4 inhibitors have shown efficacy in chronic obstructive pulmonary disease and psoriasis.

Objectives: To assess the effectiveness, local safety and tolerability, and systemic pharmacokinetics of two topical PDE4 inhibitors, roflumilast and TAK-084, in plaque psoriasis.

Methods: An intraindividual comparison of six topical products was made in 15 patients aged 18-65 years with stable chronic plaque psoriasis in an investigator-blinded, within-subject randomized study. The products evaluated were calcipotriol 0·005% cream; betamethasone valerate 0·1% (both in their marketed formulations); investigational cream formulations of roflumilast 0·5% and TAK-084 0·5% and 5%; and a vehicle cream formulation as a control. Each treatment was applied daily to different test sites located on psoriasis plaques for 3 weeks.

Results: The primary end point of (mean) change from baseline in skin infiltrate thickness after 3 weeks of treatment showed statistically significant improvements for all treatments: betamethasone valerate cream (-286·9 μm), the selective PDE4 inhibitors roflumilast 0·5% (-237·1 μm) and TAK-084 (0·5% cream, -153·6 μm; 5% cream, -216·7 μm) and calcipotriol 0·005% (-187·7 μm) when compared with vehicle cream control (all P < 0·001). Both the TAK-084 5% and roflumilast 0·5% formulations performed well overall compared with the potent corticosteroid, betamethasone, and were ranked better than the vitamin D analogue calcipotriol. All adverse events were mild or moderate and none was serious.

Conclusions: Topical treatment with cream formulations of the PDE4 inhibitors roflumilast and TAK-084 reduced inflammation, measured as a change in skin infiltrate thickness, and reduced psoriasis severity. Corticosteroid treatments have known systemic and cutaneous side-effects; PDE4 inhibitors could offer an alternative to these and deserve further study.