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.

        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.

        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

          -  Contraindication to or unable to receive cetuximab