The following criteria is provided for health care professionals.

Key Inclusion Criteria:

• Patients must have relapsed or refractory MM or NHL with no available therapies that would confer clinical benefit for their primary disease.
• For MM patients, measurable relapsed or refractory MM as defined by the IMWG Criteria (Kumar, 2016) following treatment with at least 3 lines of therapy with no other available treatment that would confer benefit.
• For NHL patients, measurable or detectable disease according to International Myeloma Working Group (IMWG) and the Lugano Classification. Extranodal NHL disease that is measurable by fluorodeoxyglucose-positron emission tomography (FDG-PET) imaging only is allowed.
• Estimated glomerular filtration rate (eGFR) ≥ 40 mL/min/1.73 m2.
• Eastern Cooperative Oncology Group (ECOG) performance status score ≤ 2
• Patient has the following laboratory test results during Screening:
  • Absolute neutrophil count (ANC) or absolute granulocyte count (AGC) ≥ 1000/µL
  • Platelets ≥ 30,000/µL
  • Hemoglobin ≥ 8g/dL
  • Absolute lymphocytes ≥ 500/µL
  • Leukocytes ≥ 3000/µL
• Patients are eligible who also meet all the following criteria in these cohorts of Part 2:
  • NKTR-255 Monotherapy NHL Group Only:
    
    • Patients with NHL who received a commercially approved CD19 CAR-T product and had PD. The first dose of NKTR-255 will be administered within 30 days of the PD.
  • NKTR-255 with Daratumumab MM Group Only:
    
    • Patients with MM must have had previous exposure to proteasome inhibitor, immunomodulatory agent (IMiD), and anti-CD38 therapy.
    • Patients who previously received daratumumab or other anti-CD38 therapies must have at least 3 months washout.
  • NKTR-255 with Rituximab Group iNHL Group Only:
    
    • Patients with relapsed or refractory iNHL who previously progressed during or following 1 or more prior systemic rituximab-containing (or another treatment with an anti-CD20 antibody-containing) regimens for lymphoma.

Key Exclusion Criteria:

• Patients who have an active, known, or suspected autoimmune disease.
• Any treatment-related neurotoxicity or cytokine release syndrome (CRS) prior to enrollment into the study should return to baseline before NKTR-255 treatment.
• Active central nervous system (CNS) involvement with NHL.
• Patients who have been previously treated with prior interleukin-2 or interleukin-15.
• Patients who received daratumumab or other anti-CD38 therapies previously must have 3 months washout.
• NOTE: Other protocol defined Inclusion/Exclusion criteria may apply