Objective: To evaluate the acute toxicity, potential efficacy, and effects on the soluble interleukin 2 receptor (sIL-2R) of recombinant human interferon gamma (rIFN-gamma) in patients with systemic sclerosis (SSc).
Methods: A multicentered, pilot clinical trial of rIFN-gamma was performed on 20 patients (15 women, 5 men, mean age 45 years) with active cutaneous SSc (mean disease duration 36 months) to evaluate it potential as a novel therapy for this untreatable disorder. After one week of rIFN-gamma 0.01 mg/m2/day, subjects self-administered rIFN-gamma 0.1 mg/m2/day intramuscularly for a total of 18 weeks. The major outcome variable was a modified skin score (0 = normal skin, 3 = hidebound skin) measured and summed from 15 anatomic areas of the body. sIL-2R levels were measured by ELISA at entry and exit from the study.
Results: The clinical results were modest at best. Nine of 20 patients achieved at least a 20% reduction in skin score, with one patient showing almost total remission of all skin abnormalities. The mean skin score at entry for all subjects was 22.8 +/- 8.9 and over the course of the trial improved marginally compared to baseline (mean change -4.72 +/- 6.62; p = 0.008). However, 8 subjects did not change appreciably while in the trial. Antibodies to Scl-70 were observed in only 5 patients (all with diffuse scleroderma) and were not associated with either response to or complications from therapy. The adverse reactions were frequent and occasionally severe. Ten subjects were withdrawn because of exacerbation of Raynaud's symptoms (n = 5), constitutional symptoms (n = 2), development of renal crises (n = 2), and mild pancytopenia (n = 1). Minor laboratory abnormalities were common and included elevation of cholesterol, triglycerides, hepatic transaminases, and reduction in white blood cell count. Compared to controls, mean sIL-2R was markedly elevated at entry (1309 +/- 495 U/ml; p = 0.0001) and did not change appreciably at exit. Spearman correlation analysis showed a trend but no statistically significant association of skin score with sIL-2R (R = 0.408; p = 0.074). However, sIL-2R was significantly correlated with erythrocyte sedimentation rate (R = 0.542; p = 0.0165). A subset analysis revealed that skin score (p = 0.0001) and sIL-2R (p = 0.00170) were significantly higher at baseline for patients with diffuse scleroderma compared to patients with limited disease.
Conclusion: rIFN-gamma may be beneficial for some patients with SSc, but the benefit appears marginal for most individuals and the side effects frequent. Although sIL-2R was elevated in many of the patients with SSc, it did not appear to be correlated with activity of cutaneous disease or response to therapy.