Phase I trial of concurrent twice-weekly recombinant human interleukin-12 plus low-dose IL-2 in patients with melanoma or renal cell carcinoma.

PURPOSE: To maintain interferon gamma (IFNgamma) induction by recombinant human interleukin-12 (rhIL-12) and enhance its activity against melanoma and renal cell cancer, a regimen of twice-weekly intravenous (IV) rhIL-12 was modified to include concurrent low-dose subcutaneous (SC) IL-2 in a phase I dose escalation study. PATIENTS AND METHODS: Patients received 6-week cycles of twice-weekly IV rhIL-12 at doses of 300 to 500 ng/kg. Midway through cycle 1, low-dose SC IL-2 was added. The IL-2 was escalated from 0.5 to 6.0 MU/m2. Grade 3 elevations of hepatic ALT, AST, or alkaline phosphatase were not considered dose-limiting unless values were more than 10 times normal. During cycle 1, patients underwent immune monitoring to assess the effect of IL-2 on lymphocyte activation and cytokine production induced by rhIL-12. RESULTS: Twenty-eight patients were enrolled onto the study. The maximum-tolerated dose (MTD) was 500 ng/kg rhIL-12 plus 3 MU/m2 IL-2. Toxicities related to the addition of IL-2 at the MTD included fever or chills, anemia, fatigue, nausea or vomiting, and orthostatic hypotension. At the MTD, IL-2 significantly augmented IFNgamma and IFNgamma-inducible protein-10 production by rhIL-12 and led to a three-fold expansion of natural killer cells. There was one major clinical response (partial response) as well as two pathologic responses; all occurred in melanoma patients. Stable disease for three to six cycles was only observed at or above the MTD in melanoma and renal cell cancer patients. CONCLUSION: The addition of concurrent low-dose IL-2 to rhIL-12 is well tolerated, restores and maintains immune activation by rhIL-12, and has clinical activity. This regimen should be further investigated in phase II studies in untreated patients with melanoma or renal cell cancer and in other rhIL-12-responsive malignancies.

IL-12 induces monocyte IL-18 binding protein expression via IFN-gamma.

IL-18 is a Th1 cytokine that synergizes with IL-12 and IL-2 in the stimulation of lymphocyte IFN-gamma production. IL-18 binding protein (IL-18BP) is a recently discovered inhibitor of IL-18 that is distinct from the IL-1 and IL-18 receptor families. In this report we show that IL-18BPa, the IL-18BP isoform with the highest affinity for IL-18, was strongly induced by IL-12 in human PBMC. Other Th1 cytokines, including IFN-gamma, IL-2, IL-15, and IL-18, were also capable of augmenting IL-18BPa expression. In contrast, IL-1alpha, IL-1beta, TNF-alpha, IFN-gamma-inducible protein-10, and Th2 cytokines such as IL-4 and IL-10 did not induce IL-18BPa. Although monocytes were found to be the primary source of IL-18BPa, the induction of IL-18BPa by IL-12 was mediated through IFN-gamma derived predominantly from NK cells. IL-18BPa production was observed in cancer patients receiving recombinant human IL-12 and correlated with the magnitude of IFN-gamma production. The IFN-gamma/IL-18BPa negative feedback loop identified in this study may be capable of broadly controlling immune activation by cytokines that synergize with IL-18 to induce IFN-gamma and probably plays a key role in the modulation of both innate and adaptive immunity.