- BACKGROUND: Several studies have shown that interferon alpha as a single agent produces responses in multiple myeloma patients, and may produces responses in multiple myeloma of interleukin-2 (rHu-IL-2) in multiple myeloma models indicate that rHu-IL-2 may have a therapeutic effect. In this phase II clinical trial, we combined rHu-interferon alpha-2a (rHu-IFN-2a) and rHu-IL-2, to assess the feasibility, toxicity and response rate when this treatment was given as subcutaneous injections to previously treated patients with relapsed or refractory multiple myeloma. PATIENTS AND METHODS: Seventeen patients with measurable serum M protein or urine paraprotein were entered on the study. Three patients were refractory to first line treatment; fourteen had relapsed following response to prior treatment. rHu-IFN alpha-2a was given three times per week continuously. rHu-IL-2 was given three times per week for 6 weeks followed by a 2-week break from treatment. Patients were assessed for response and toxicity at 4-week intervals. RESULTS: All patients were eligible and evaluable for toxicity; two patients were invaluable for response because they did not complete 4 weeks of treatment. All response-evaluable patients had a best objective response of stable disease which lasted a median of 22 weeks and was maintained for over one year in 5 patients. Toxicity was tolerable and was typical of rHu-IL-2 and rHu-IFN alpha-2a; fever, chills or rigors and lethargy were nearly universal; local toxicity at the injection site, headache, anorexia, nausea and vomiting were also common. CONCLUSIONS: No objective responses in serum M protein or urine paraprotein levels were noted thus we do not recommend further study of this combination in myeloma.