Background
Serum interleukin (IL)-6 levels correlate with disease outcomes in renal cell carcinoma (RCC) patients. Siltuximab, a chimeric, murine-human mAb against IL-6, was evaluated in a three-part phase I/II study in patients with progressive metastatic RCC.
Conclusion
Siltuximab stabilised disease in >50% of progressive metastatic RCC patients. One PR was observed. Given the favourable safety profile of siltuximab and poor correlation of tumour shrinkage with clinical benefit demonstrated for other non-cytotoxic therapies, further evaluation of dose-escalation strategies and/or combination therapy may be considered for patients with RCC.
Methods
In part 1, 11 patients received 1, 3, 6, or 12mgkg-¹ at weeks 1, 4 and q2w × 2 thereafter; in part 2, 37 patients randomly received 3 or 6 mgkg-¹ q3w × 4; in part 3, 20 low-risk patients received 6mgkg-¹ q2w × 6. Modified WHO response criteria were assessed at weeks 7, 11, the 6-week follow-up, and when clinically indicated.
Results
Siltuximab was well tolerated overall, with no maximum tolerated dose or immune response observed. In all, 5 out of 11, 17 out of 37, and 9 out of 20 patients in parts 1, 2, and 3, respectively, received extended treatment beyond 4-6 initial infusions. In part 2, stable disease (SD) (≥11weeks) or better was achieved by 11 out of 17 (65%) 3 mgkg-¹ treated patients (one partial response (PR) ~8 months, 10 SD) and 10 out of 20 (50%) 6mgkg-¹ treated patients (10 SD). In part 3, documented complete or PR was not observed, but 13 out of 20 (65%) patients achieved SD.