Pharmacokinetics of Roflumilast Cream in Chronic Plaque Psoriasis: Data from Phase I to Phase III Studies

Background Most patients with chronic plaque psoriasis receive topical treatment; however, available options lack a balance of efficacy with long-term safety and tolerability. Roflumilast cream 0.3% is a highly potent phosphodiesterase 4 (PDE4) inhibitor approved by the US FDA for treatment of psoriasis. Objective The aim of this study was to define the pharmacokinetic (PK) profile of roflumilast delivered topically from a phase I maximal usage study and data from phase II and phase III studies. Methods PK data for roflumilast and the active metabolite, roflumilast N-oxide, were determined from a phase I PK and safety maximal usage study of roflumilast cream 0.3% applied once daily for 14 days in patients with plaque psoriasis affecting body surface area (BSA) >= 20% (N = 26). Serial plasma samples were obtained on Days 1 and 15 to determine maximum plasma concentration (C-max) and area under the concentration-time curve (AUC). Plasma concentrations were also assessed at Weeks 3, 4, and 5 for terminal half-life (t(1/2)). Concentrations of roflumilast and roflumilast N-oxide in skin were assessed at Day 28 for 14 patients with psoriasis in a phase I/IIa study of once-daily roflumilast cream 0.5% and 0.15% for 28 days. Systemic exposure (C-trough and AUC) of roflumilast and roflumilast N-oxide in two phase III trials (DERMIS-1, n = 245; DERMIS-2, n = 250) of roflumilast cream 0.3% for 8 weeks was assessed at Weeks 4 and 8. Results Bioavailability of roflumilast cream 0.3% after topical administration was 1.5%. Unlike after oral dosing, the plasma concentration-time curve was flat, with a peak-to-trough ratio of 1.2. Roflumilast N-oxide concentrations were eightfold higher than roflumilast concentrations. The t(1/2) in adult patients was 4.0 days for roflumilast and 4.6 days for roflumilast N-oxide following the last dose administered. Steady state was reached by Day 15. Concentrations of roflumilast in skin were, on average, 126- and 61.8-fold higher than corresponding mean plasma C-trough following administration of roflumilast cream 0.15% and 0.5% daily for 28 days. Roflumilast N-oxide was quantifiable in only one skin sample (N = 27). Following 8 weeks of treatment in DERMIS-1, mean plasma C-trough of roflumilast was 1.78 ng/mL, and 9.86 ng/mL for roflumilast N-oxide. In DERMIS-2, mean plasma C-trough was 1.72 ng/mL and 10.2 ng/mL, respectively. In the maximal usage study (mean BSA: 27.5%), eight patients (30.8%) experienced adverse events (AEs) and all were mild or moderate, with no reports of diarrhea, headache, insomnia, or application-site pain; no patients discontinued treatment due to an AE. Conclusion Topical administration of roflumilast cream 0.3% results in concentrations in skin 126- and 61.8-fold higher relative to plasma, which are much higher than expected to be achievable with oral dosing. PDE4 inhibition in the skin is likely due to roflumilast as compared with its active metabolite, as there is no significant conversion to roflumilast N-oxide in the skin. Consistent with reservoir formation and retention of drug in the stratum corneum, roflumilast is slowly released from the skin (t(1/2) 4 days) and peak-to-trough ratio is 1.2. ClinicalTrials.gov Identifiers NCT04279119, NCT03392168, NCT04211363, NCT04211389.