Inclusion criteria

• Subject is considered an adult according to local regulation at the time of signing the informed consent form (ICF).
• Subject has measurable disease by RECIST Version 1.1.
• Subject has accessible archival tumor tissue from either the primary tumor or a metastatic site, for which source and availability have been confirmed prior to study treatment. If no archival tumor tissue is available, the subject will have a biopsy to obtain tumor tissue prior to study treatment. If the subject is unable to undergo a biopsy due to safety concerns, enrollment into the study must be discussed with the medical monitor.
• For cohort 9 only: Subject should submit archival or fresh tumor tissue sample for programmed cell death-ligand 1 (PD-L1) central testing during screening if no local PD-L1 test result is available. Central test result for PD-L1 will be required prior to subject enrollment. For cohort 9 subjects with local PD-L1 test result confirming CPS ≥ 1, archival or fresh tissue sample for exploratory analysis should be submitted within 5 days of enrollment.
• Subject has ECOG performance status of 0 or 1.
• Subject has the following baseline laboratory data. If a subject has received a recent blood transfusion, the hematology tests must be obtained ≥ 28 days after any blood transfusion.
  • absolute neutrophil count (ANC) ≥ 1.0 × 10^9/L
  • platelet count ≥ 100 × 10^9/L
  • hemoglobin ≥ 9 g/dL
  • serum total bilirubin ≤ 1.5 × upper limit of normal (ULN) or ≤ 3 × ULN for subjects with Gilbert's disease
  • creatinine clearance (CrCl) ≥ 30 mL/min as estimated per institutional standards or as measured by 24-hour urine collection (glomerular filtration rate [GFR] can also be used instead of CrCl).
  • alanine aminotransferase (ALT) and aspartate aminotransferase (AST) ≤ 3 × ULN
• Subject agrees not to participate in another interventional study while receiving study treatment in the present study.
• Additional contraceptive requirements exist for male and female subjects.
• Disease Specific Inclusion Criteria:
• Evidence of progression on or after the last regimen received.
• Locally advanced or metastatic disease that is not amenable to curative intent treatment.
• Cohort 1: HR+/HER2- breast cancer
• Subject has evidence of radiographic progression on or after the last regimen received.
• Subject has histologically- or cytologically-confirmed HR+/HER2- (estrogen receptor [ER] positive and/or progesterone receptor [PR] positive, and HER2 negative) breast cancers and are not considered a candidate for further hormonal therapy. Subject will be considered HR+ if biopsies show ≥ 1% expression of ER or PR as per current American Society of Clinical Oncology/College of American Pathologists (ASCO/CAP) guidelines.
• Subject has locally advanced or metastatic disease that is not amenable to curative intent treatment.
• Subject must have received a taxane or anthracycline in the neoadjuvant, adjuvant or incurable, locally advanced or metastatic setting.
  • Prior cytotoxic regimen received in the neoadjuvant or adjuvant setting will count as a prior cytotoxic regimen if disease recurrence occurred during or within 6 months of completing the regimen.
• Subject has progressed, relapsed, or discontinued for toxicity during or after at least 1 prior standard of care cytotoxic regimen in the incurable, unresectable locally advanced or metastatic setting, and has not received > 2 prior lines of cytotoxic therapy in the locally advanced or metastatic setting. No limit applies to endocrine therapies. Poly(ADP-ribose) polymerases (PARP) inhibitors do not count as a line of cytotoxic therapy.
• Subject has progressed, relapsed, or discontinued for toxicity during or after receiving endocrine therapy or with hormonally-directed therapy with cyclin-dependent kinase (CDK) inhibitors. Prior therapy with CDK inhibitors is not required.
• Cohort 2: triple negative breast cancer (TNBC)
• Subject has evidence of radiographic progression on or after the last regimen received.
• Subject has histologically- or cytologically-confirmed TNBC; defined as unequivocal TNBC histology (ER-negative/PR-negative/HER2-negative). This is defined by < 1% expression of ER and PR by immunohistochemistry (IHC), and that are, for HER2, either 0 to 1+ by IHC, or IHC 2+ and fluorescence in situ hybridization (FISH) negative (not amplified) as per current ASCO/CAP guidelines.
• Subject has locally advanced or metastatic disease that is not amenable to curative intent treatment.
• Subject must have received a taxane or anthracycline in the neoadjuvant, adjuvant or incurable, locally advanced or metastatic setting.
  • Prior cytotoxic regimen received in the neoadjuvant or adjuvant setting will count as a prior cytotoxic regimen if disease recurrence occurred during or within 6 months of completing the regimen.
• Subject has progressed, relapsed, or discontinued for toxicity during or after at least 1 prior standard of care cytotoxic regimen in the incurable, unresectable locally advanced or metastatic setting, and has not received > 2 prior lines of cytotoxic therapy in the locally advanced or metastatic setting. Poly(ADP-ribose) polymerases (PARP) inhibitors do not count as a line of cytotoxic therapy.
• Subject has received prior therapy with an anti-programmed cell death protein-1 (PD-1) or an anti-programmed cell death-ligand 1 (PD-L1) based on subject's tumor PD-1 or PD-L1 expression and local treatment guidelines and has progressed or discontinued treatment due to toxicity, or therapy is contraindicated for subject.
• Cohort 3: squamous non-small cell lung cancer (NSCLC)
• Subject has evidence of radiographic progression on or after the last regimen received.
• Subject has histologically or cytologically-confirmed squamous NSCLC.
  • Subjects with mixed histology NSCLC are eligible provided there is not any component of neuroendocrine histology.
  • Subjects with known epidermal growth factor receptor (EGFR), anaplastic lymphoma kinase (ALK), reactive oxygen species (ROS), BRAF, or other actionable mutations are eligible if treated with mutation targeted therapy and have progressed, relapsed, or discontinued treatment due to toxicity.
• Subject has locally advanced or metastatic disease that is not amenable to curative intent treatment.
• Subject has progressed, relapsed, or discontinued treatment due to toxicity after 1 platinum-based standard of care regimen for locally advanced or metastatic disease, and has not received > 2 prior lines of cytotoxic anticancer therapy in the locally advanced or metastatic setting.
  • Subjects with locally advanced disease who previously received curative intent treatment with platinum-based standard of care regimen in the adjuvant or neoadjuvant setting or as part of concomitant chemoradiation therapy are eligible if they have progressed or relapsed within 6 months of completion.
  • Maintenance therapy does not constitute a new chemotherapy regimen provided there was no progression after the initial platinum-based regimen.
  • Changing chemotherapy agents during platinum-based treatment for the management of toxicities does not constitute a new chemotherapy regimen provided no progression had occurred while on the initial therapy.
• Subject has received prior therapy with an anti-PD-1 or anti-PD-L1 based on subject's tumor PD-1 or PD-L1 expression and local treatment guidelines and has progressed, relapsed, or discontinued treatment due to toxicity, or therapy is contraindicated for subject.
• Cohort 4: non-squamous non-small cell lung cancer
• Subject has evidence of radiographic progression on or after the last regimen received.
• Subject has histologically- or cytologically-confirmed non-squamous NSCLC.
  • Subjects with mixed histology NSCLC are eligible provided there is not any component of neuroendocrine histology.
  • Subjects with known EGFR, ALK, ROS, BRAF, or other actionable mutations are eligible if treated with mutation targeted therapy and have progressed, relapsed, or discontinued treatment due to toxicity.
• Subject has locally advanced or metastatic disease that is not amenable to curative intent treatment.
• Subject has progressed, relapsed, or discontinued treatment due to toxicity after 1 platinum-based standard of care regimen for locally advanced or metastatic disease, and has not received > 2 prior lines of cytotoxic anticancer therapy in the locally advanced or metastatic setting.
  • Subjects with locally advanced disease who previously received curative intent treatment with platinum-based standard of care regimen in the adjuvant or neoadjuvant setting or as part of concomitant chemoradiation therapy are eligible if they have progressed or relapsed within 6 months of completion.
  • Maintenance therapy does not constitute a new chemotherapy regimen provided there was no progression after the initial platinum-based regimen.
  • Changing chemotherapy agents during platinum-based treatment for the management of toxicities does not constitute a new chemotherapy regimen provided no progression has occurred while on the initial therapy.
• Subject has received prior therapy with an anti-PD-1 or anti-PD-L1 based on subject's tumor PD-1 or PD-L1 expression and local treatment guidelines and has progressed, relapsed, or discontinued treatment due to toxicity, or therapy is contraindicated for subject.
• Cohort 5: second-line or later head and neck cancer
• Subject has evidence of radiographic progression on or after the last regimen received.
• Subject has histologically- or cytologically-confirmed head and neck cancer.
  • Primary tumor site must arise from the oral cavity, oropharynx, hypopharynx, and larynx; tumors arising from the nasopharynx are excluded. Salivary gland tumors and/or parotid gland tumors are not eligible for Cohort 5.
• Subject has locally advanced or metastatic disease that is not amenable to curative intent treatment.
• Subject has progressed, relapsed, or discontinued treatment due to toxicity after 1 platinum-based standard of care regimen for locally advanced or metastatic disease, and has not received > 2 prior lines of cytotoxic anticancer therapy in the locally advanced or metastatic setting.
  • Subjects with locally advanced disease who previously received curative intent treatment with platinum-based standard of care regimen in the adjuvant or neoadjuvant setting or as part of concomitant chemoradiation therapy are eligible if they have progressed or relapsed within 6 months after completion.
• Subject has received prior therapy with an anti-PD-1 or anti-PD-L1 based on subject's tumor PD-1 or PD-L1 expression and local treatment guidelines and has progressed, relapsed, or discontinued treatment due to toxicity, or therapy is contraindicated for subject.
• Cohorts 6, 7 and 8: gastric or gastroesophageal junction (GEJ) or esophageal adenocarcinoma
• Subject has evidence of radiographic progression on or after the last regimen received.
• Subject has histologically- or cytologically-confirmed gastric, GEJ, or esophageal cancer.
• Subject has locally advanced or metastatic disease that is not amenable to curative intent treatment.
• Subject has progressed, relapsed, or discontinued due to toxicity after 1 platinum-based standard of care regimen for locally advanced or metastatic disease, and has not received > 2 prior lines of cytotoxic anticancer therapy in the locally advanced or metastatic setting.
  • Neoadjuvant or adjuvant cytotoxic regimens will count as a prior regimen if relapsed or progressed ≤ 6 months after completion.
• Subject must have received a HER2 directed therapy if known to have HER2 positive cancer.
• Subject has received prior therapy with an anti-PD-1 or anti-PD-L1 based on subject's tumor PD-1 or PD-L1 expression and local treatment guidelines and has progressed, relapsed, or discontinued treatment due to toxicity, or therapy is contraindicated for subject.
• Cohort 9: 1L HNSCC

• Subject has histologically- or cytologically-confirmed head and neck squamous cell carcinoma.

  a. Primary tumor site must arise from the oral cavity, oropharynx, hypopharynx, and larynx; tumors arising from the nasopharynx are excluded. Salivary gland tumors and/or parotid gland tumors are not eligible for Cohort 9.

• Subject has recurrent or metastatic disease that is incurable by local therapies.
• Subject's tumor sample has PD-L1 combined positive score (CPS) of ≥ 1 as determined by local or central IHC testing.
• Subject has had no prior systemic therapy administered with the exception of systemic therapy completed > 6 months prior if given as part of multimodal treatment for locally advanced disease. Subjects who have received a PD-1 or PD-L1 inhibitor in the curative setting are eligible if it has been at least 12 months since last dose of the anti PD-L1 agent.
• Subject has ANC ≥ 1.5 × 10^9/L.
• International normalized ratio (INR) OR prothrombin time (PT) and activated partial thromboplastin (aPTT) both ≤ 1.5 × ULN unless subject is receiving anticoagulant therapy as long as PT or aPTT is within the therapeutic range of intended use of anticoagulants. PTT may be used if local lab is unable to perform aPTT.
• For subjects with oropharynx tumors, subject has results from testing of HPV status by p16 testing.