Study of NKTR 255 in Combination With Cetuximab in Solid Tumors

Key Inclusion Criteria: * Histologically confirmed diagnosis of a locally advanced or metastatic HNSCC or CRC. * Life expectancy \> 12 weeks as determined by the Investigator. * Eastern Cooperative Oncology Group (ECOG) performance status 0 or 1. * Measurable disease per RECIST 1.1. HNSCC: * Progression on any first or second line platinum-based chemotherapy and/or anti-PD-1 or programmed death-ligand 1 antibody. CRC: * Patients must have received or were intolerant to at least 2 prior cancer therapy regimens administered for metastatic disease. Key Exclusion Criteria: * Use of an investigational agent or an investigational device within 28 days before administration of first dose of study drug(s) * Prior surgery or radiotherapy within 14 days of initiating study drug(s) * Evidence of clinically significant interstitial lung disease or active, noninfectious pneumonitis; active infection requiring systemic therapy within 7 days prior to dosing * Patients who have been previously treated with IL-2 or IL-15 * Known Grade 3 or 4 hypersensitivity reaction to cetuximab, history of allergy to red meat or tick bites, or history of positive test results for immunoglobulin E antibodies against cetuximab * Patients who have an active, known, or suspected autoimmune disease NOTE: Other protocol defined inclusion/exclusion criteria may apply