Design and Methods: In an open-label phase 2 trial, 10 patients with psoriasis subcutaneously received recombinant human IL-10 over a 7-week period in a dosage of 8 mu g/kg daily (n=5) or 20 mu g/kg 3 times per week (n=5). Patients were followed up for an additional 5 weeks.

Results: The treatment was well tolerated. Antipsoriatic effects were found in all but 1 patient. A significant decrease of the psoriasis area and severity index by 55.3% +/- 11.5% (mean +/- SEM) was observed (P<.02). The antipsoriatic efficiency was confirmed by histological examination. Heterogeneity in the effectiveness was found among the patients, but seems to be independent of the dosage regimen. However, a tendency to a better response was found in the patients who received 20-mu g/kg IL-10 3 times per week. Decreasing response in the delayed-type hyper-sensitivity reaction against recall antigens indicated immunosuppressive effects. Moderate effects on hematopoietic cells were observed.

Conclusions: Our data suggest that IL-10 therapy for psoriasis is safe and possibly clinically effective. Consequently, its value in psoriasis and similar immune diseases should be further determined. Dose-finding, placebo-controlled, double-blind trials are necessary now.