A Study of PEGylated Recombinant Human Hyaluronidase (PEGPH20) With Pembrolizumab in Participants With Selected Hyaluronan High Solid Tumors

Inclusion Criteria

• Dose Expansion: Histologically confirmed and documented, previously untreated or treated stage IIIB or IV NSCLC having failed no more than 1 previous platinum containing chemotherapy regimen for locally-advanced or metastatic disease or relapsed/refractory locally advanced or metastatic gastric adenocarcinoma having failed no more than 2 previous chemotherapy regimens for locally advanced or metastatic disease. Participants with NSCLC who are known to be epidermal growth factor receptor (EGFR)-mutation positive must have received an EGFR inhibitor and participants known to be anaplastic lymphoma kinase (ALK)-mutation positive must have received an ALK inhibitor. Prior to enrollment, confirmation of the following must be obtained: • For participants in the dose expansion portion of the study, it is mandatory that available archived tumor tissue in formalin-fixed. paraffin-embedded (FFPE) block or minimum 10-15 unstained consecutive core biopsy slides from 1 archival block that meet specific tissue requirements are available.
• For dose expansion: one or more tumors measurable on computed tomography (CT) scan/magnetic resonance imaging (MRI) scan per RECIST v 1.1., for dose escalation, participants need only have evaluable disease - Previously irradiated tumors may be eligible if they have clearly progressed in size.
• Eastern Cooperative Oncology Group (ECOG) Performance Status of 0 or 1.
• Life expectancy greater than or equal to (≥) 3 months. Participants must also satisfy the following inclusion criterion to be enrolled in the dose expansion portion:
• Participants (NSCLC and gastric adenocarcinoma) must be determined to have HA-high levels from their tumor biopsies.
• NSCLC and gastric adenocarcinoma participants must have tissue available for HA-selection and programmed cell death-1 (PD-L1) testing.

Exclusion Criteria

• Previous treatment with pembrolizumab, nivolumab, or other antibody (anti-)-PD-1 or PD-1 ligand-antibody (anti-PD-L1) agents.
• New York Heart Association Class III or IV (Appendix D) cardiac disease or myocardial infarction within the past 12 months before screening, or preexisting atrial fibrillation.
• Prior history of cerebrovascular accident or transient ischemic attack.
• NSCLC participants with known brain metastases (certain exceptions allowed)
• Gastric adenocarcinoma participants with brain metastases
• History of active bleeding within the last 3 months requiring transfusion
• Anti-angiogenic therapy within the last month
• Participants with known interstitial fibrosis or interstitial lung disease.
• Previous history of pulmonary embolism or pulmonary embolism found on screening exam.
• History of:
• Pneumonitis that requires oral or IV steroids;
• Or known cases of hepatobiliary diseases (e.g., primary biliary cholangitis, primary sclerosing cholangitis, history of immune-mediated cholangitis);
• Participants with cholangitis attributed to infectious etiology (e.g., ascending cholangitis, bacterial cholangitis) are eligible if the infection has been fully resolved prior to the screening visit.
• Or known cases of drug-induced hepatobiliary toxicities.
• Active autoimmune disease requiring systemic treatment within the past 3 months or documented history of clinically severe autoimmune disease, or syndrome that requires systemic steroids or immunosuppressive agents.
• History of another primary cancer within the last 3 years that required treatment, with the exception of non-melanoma skin cancer, early-stage prostate cancer, or curatively treated cervical carcinoma in situ.