Study of NKTR 255 in Combination With Cetuximab in Solid Tumors

Patients with relapsed or refractory (R/R) head and neck squamous cell carcinoma (HNSCC) or colorectal carcinoma (CRC) will receive a loading dose of cetuximab alone, followed 7 days later by the first combination treatment of cetuximab and NKTR-255 on Cycle 1 Day 1 (C1D1). Thereafter, intravenous (IV) NKTR-255 will be given in 21-day cycles in combination with weekly IV cetuximab. After determination of the recommended Phase 2 dose (RP2D) of NKTR-255 in combination with cetuximab, this dose of NKTR-255 will be further studied in patients with HNSCC (Cohort A) and CRC (Cohort B) in Phase 2 of the study.

This study is a Phase 1b/2, open-label, multicenter dose escalation and dose expansion study in patients with R/R HNSCC or CRC. NKTR-255 is a cytokine that is designed to regulate T and natural killer cell activation, proliferation and promote their anti-tumor effects. After an initial cetuximab loading dose during the study run-in period (Day -7), patients will receive IV NKTR-255 every 21 days in combination with cetuximab weekly. In the dose escalation phase, beginning with Dose Level 1, successive cohorts will receive ascending doses of NKTR-255 until the MTD and/or RP2D is determined. Patients who achieve optimal response (partial response or complete response), will be given the option to continue treatment with NKTR-255 as single agent for maintenance. Enrollment into Phase 2 will commence once the RP2D is established in Phase 1b. The RP2D of NKTR-255 will be evaluated in expansion Cohorts A and B. Cohort A will combine NKTR-255 and cetuximab in patients with R/R HNSCC and Cohort B will combine NKTR-255 and cetuximab in patients with R/R CRC.