Key Inclusion Criteria:

All Study Parts:

- Personally signed and dated informed consent form

- Male or female ≥ 18 years of age

- Diagnosis of cancer that has been histologically or cytologically confirmed

- Eastern Cooperative Oncology Group Performance Status of 0 or 1

- For male patients and female patients of childbearing potential, agreement to use an effective method of contraception per institutional standards through 4 months after the last administration of study treatment (i.e., ARRY-382, pembrolizumab)

- For females of childbearing potential only, negative serum human chorionic gonadotropin (hCG) pregnancy test result at baseline and nonlactating

- Willingness and ability to comply with scheduled visits, treatment plan, laboratory tests, and other study procedures

Part A (1 of the following):

- Ovarian cancer, triple-negative breast cancer, head and neck squamous cell cancer, bladder cancer, metastatic colorectal cancer, pancreatic ductal adenocarcinoma, or gastric cancer that is measurable or evaluable, nonmeasurable as defined by RECIST v1.1 and meets 1 of the following criteria:

- is refractory to standard of care

- no standard therapy available

- patient refuses standard therapy

- Advanced, unresectable, or metastatic melanoma with or without prior treatment and measurable or evaluable, nonmeasurable disease as defined by RECIST v1.1

- Advanced/metastatic PD-L1-positive NSCLC, with progression following treatment with a platinum-containing chemotherapy regimen or with progression following locally approved appropriate therapy for patients with EGFR or anaplastic lymphoma kinase (ALK) genomic tumor aberrations and measurable or evaluable, nonmeasurable disease as defined by RECIST v1.1

Part B:

- Advanced, unresectable, or metastatic melanoma with or without prior treatment, measurable disease as defined by RECIST v1.1, and a minimum of 3 lesions

Part C:

- Advanced/metastatic PD-L1-positive NSCLC, with progression following treatment with a platinum-containing chemotherapy regimen, or with progression following locally approved appropriate therapy for patients with EGFR or ALK genomic tumor aberrations and measurable disease as defined by RECIST v1.1

Key Exclusion Criteria:

- Prior treatment as follows:

- Part A: an immune CPI (e.g., PD-1, PD-L1, or cytotoxic T-lymphocyte antigen 4 [CTLA-4] inhibitor)

- Parts B and C: an immune CPI (e.g., PD-1, PD-L1, or CTLA-4 inhibitor) or a CSF-1R or CSF-1 (or MCSF) inhibitor

- Symptomatic brain metastasis at screening

- Active autoimmune disease, documented history of autoimmune syndrome or disease, or a chronic medical condition that requires chronic steroid therapy or immunosuppressive medication

- History of pneumonitis or interstitial lung disease

- Severe, acute, or chronic medical or psychiatric condition or laboratory abnormality that may increase the risk associated with study participation or study drug administration or that may interfere with the interpretation of study results and, in the judgment of the Investigator, would make the patient an inappropriate candidate for the study