for people ages 18 years and up (full criteria)
study started
estimated completion



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.

Official Title

A Phase 1b/2, Open-label, Multicenter, Dose Escalation and Dose Expansion Study of NKTR 255 in Combination With Cetuximab as a Salvage Regimen for Solid Tumors


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.


Head and Neck Squamous Cell Carcinoma (HNSCC) Colorectal Cancer (CRC) HNSCC CRC R/R NKTR-255 Cetuximab Squamous Cell Carcinoma of Head and Neck


You can join if…

Open to people ages 18 years and up

  • 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.

CRC: Patients with microsatellite instability-high (MSI-H) or mismatched repair disease (dMMR) tumors must have been exposed to checkpoint inhibitors such as anti-PD-(L)1 or anticytotoxic T-lymphocyte-associated protein (CTLA)-4 antibody.

You CAN'T join if...

  • 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
  • Contraindication to or unable to receive cetuximab


  • University of California, San Diego accepting new patients
    San Diego California 92103 United States
  • University of California, San Francisco accepting new patients
    San Francisco California 94158 United States


accepting new patients
Start Date
Completion Date
Nektar Therapeutics
Phase 1/2
Study Type
Last Updated