Avelumab With Bempegaldesleukin With or Without Talazoparib or Enzalutamide in Advanced or Metastatic Solid Tumors

Evaluation of the combination of avelumab + bempegaldesleukin (NKTR-214 ) in locally advanced squamous cell carcinoma of the head and neck ( metastatic SCCHN) and avelumab + bempegaldesleukin (NKTR-214) + talazoparib or enzalutamide in metastatic castration resistant prostate cancer (mCRPC).

Phase 1b/ Phase 2 Design

Phase 1b will be the sequential dose-finding study.

Once the Phase 1b component is completed, Phase 2 will be initiated to further evaluate the safety and anti-tumor activity across combinations of therapy.

Combination A will enroll participants with SCCHN.

Combination B and C will enroll participants with mCRPC

Eligibility Criteria:
Inclusion Criteria:

* Participants must be ≥ 18 years old.
* Participants with SCCHN or mCRCP.
* Participants must have histological diagnosis of solid tumors and provide tumor tissue.
* Measurable disease by RECIST v1.1 with at least 1 measurable lesion.
* Eastern Cooperative Oncology Group (ECOG) Performance Status (PS) 0 or 1.
* Adequate bone marrow, renal and liver function
* Highly effective contraceptive use by men with the ability to father a child or women of childbearing potential.
* A WOCBP must have a negative highly sensitive pregnancy test (\[urine or serum\] as required by local regulations) at C1D1.
* Signed and dated informed consent.

Exclusion Criteria:

* Known prior severe hypersensitivity to investigational products or any component in their formulations, including known severe hypersensitivity reactions to monocolonal antibodies.
* Known history of: immune-mediated colitis, inflammatory bowel disease, pneumonitis, or pulmonary fibrosis.
* Active or prior autoimmune disease that might deteriorate when receiving an immunostimulatory agent.
* Prior organ transplantation including allogenic stem cell transplantation.
* Vaccination within 4 weeks prior to C1D1 and while on trial is prohibited except for administration of inactivated vaccines.
* Known symptomatic brain lesions requiring steroids.
* Known history of testing positive for human immunodeficiency virus (HIV or known acquired immunodeficiency syndrome (AIDS).
* Positive HBV surface antigen or HCV test indicating acute or chronic infection..
* Active infection requiring systemic therapy
* Clinically significant (i.e., active) cardiovascular disease including the following: documented left ventricular ejection fraction (LVEF) \<50% by ECHO/MUGA; cerebral vascular accident/stroke or transient ischemic attack; myocardial infarction; unstable angina; congestive heart failure or serious cardiac arrhythmia (uncontrolled, clinically significant) requiring medication.
* Diagnosis of any other malignancy within 2 years prior to C1D1, except for adequately treated basal cell or squamous cell skin cancer, carcinoma in situ of the breast, bladder or of the cervix and for Combination A only, low-grade (Gleason 6 or below) prostate cancer on surveillance with no plans for treatment intervention (e.g., surgery, radiation, or castration) or adequately treated prostate cancer.
* Current use of immunosuppressive medication at the time of study enrollment.
* Major surgery within 4 weeks prior to study enrollment.
* Conditions that may impair intake or absorption such as inability to swallow capsules or tablets; known malabsorption syndrome; or baseline diarrhea ≤ Grade 1.
* Participation in other studies involving investigational drug(s) within 2 weeks prior to C1D1.