Study of AMG 994 Monotherapy and AMG 994 and AMG 404 Combination Therapy in Participants With Advanced Solid Tumors

Inclusion Criteria: * Participant has provided informed consent/assent prior to initiation of any study specific activities/procedures. * Age ≥ 18 years at the time of signing informed consent. * Life expectancy of \> 3 months, in the opinion of the investigator. * Participant must have histologically or cytologically proven metastatic or locally advanced solid tumors of known MSLN expression who have relapsed after and/or are refractory to established and available therapies with known clinical benefit, for which: * No standard systemic therapy exists; or * Standard systemic therapy has failed or is not available. * Dose Expansion (Part 2): Participant must have one of the following malignancies: mesothelioma, pancreatic adenocarcinoma, MSLN positive NSCLC squamous cell carcinoma or adenocarcinoma, high grade serous ovarian carcinoma. * At least 1 measurable or evaluable lesion as defined by modified RECIST 1.1 guidelines. * Participants must be willing to undergo a biopsy prior to enrollment and during treatment with AMG 994. * Participants with treated brain metastases are eligible provided they meet the following criteria: * Definitive therapy was completed at least 2 weeks prior to enrollment. * No evidence of radiographic central nervous system (CNS) progression or CNS disease following definitive therapy and by the time of study screening. Patients manifesting progression in lesions previously treated with stereotactic radiosurgery may still be eligible if p…