Dose-related immunologic effects of levamisole in patients with cancer

Purpose: This phase I study was conducted to determine the maximum-tolerated dose (MTD) and the immunologic properties of levamisole in cancer patients when administered alone and in combination with interferon gamma (IFN-γ). Patients and Methods: Twenty patients with advanced cancer and 36 patients with completely resected melanoma (n = 33) or renal cell cancer (n = 3) received levamisole orally every other day for six doses at 1.0, 2.5, 5.0, or 10.0 mg/kg. Ten days later, patients restarted levamisole and began IFN-γ 0.1 mg/m² by subcutaneous injection every other day. Blood samples were collected for measurement of neopterin and soluble interleukin-2 receptor (sIL-2R), and for flow-cytometric analysis. Results: The MTD of levamisole was 5 mg/kg, and this was not changed by the addition of IFN-γ. Dose-related increases in serum levels of neopterin and sIL-2R were noted. Multiple doses of ≥ 5 mg/kg of levomisole were required to elicit immune changes, which were more prominent in patients with minimal tumor burdens. Increased expression of CD64 and class I and class II major histocompatibility antigens on monocytes was also observed. The combination of IFN-γ and levamisole did not result in greater immunologic effects than those observed in previous trials of IFN-γ alone. Conclusion: Levamisole induces dose-related immunologic changes in patients with large or minimal tumor burdens. These changes may be involved in the beneficial effects noted in recent adjuvant trials of levamisole. Ongoing clinical trials should correlate immune changes with response, and trials exploring different schedules of administration using higher, more immunologically active, doses of levamisole should be performed.