Study of TSR-042, an Anti-programmed Cell Death-1 Receptor (PD-1) Monoclonal Antibody, in Participants With Advanced Solid TumorsGARNET

Participant is at least 18 years of age.

• Participant has proven recurrent or advanced solid tumor and has disease progression after treatment with available anticancer therapies, or is intolerant to treatment that meets the following requirements for the part of the study they will participate in: A. Part 1: Any histologically or cytologically proven recurrent or advanced solid tumor B. Part 2A: : Any histologically or cytologically proven recurrent or advanced solid tumor C. Part 2B: Histologically of cytologically proven recurrent or advanced solid tumor with measurable lesion(s) per RECIST version 1.1 and meets one of the following disease types: The criteria below should be met for participant participating in: 1) Cohort A1 (dMMR/MSI-H endometrial cancer) and 2) Cohort A2 (MMR-proficient/MSS endometrial cancer)

Participants must have been previously treated with platinum-based regimn, taxane agent(s), and bevacizumab (bevacizumab could be used as a single agent or in combination with another agent, in frontline therapy, as maintenance, or for treatment of recurrent disease).

• Part 2B: Participants must have archival tumor tissue available that is formalin-fixed and paraffin-embedded (FFPE).

For Cohort G, participant must provide formalin fixed paraffin embedded (FFPE) tumor tissue block(s) with sufficient tumor content (as confirmed by the Sponsor's designated central laboratory) during screening to enable, for example, measures of homologous recombination pathway defects and PD-L1 status. The use of slides created from paraffin-embedded tissue as opposed to FFPE blocks must be approved by the Sponsor.

• Female participants must have a negative serum pregnancy test within 72 hours prior to the date of the first dose of study medication: unless they are of non-child bearing potential.Non child bearing potential is defined as:

Post-hysterectomy, post-bilateral oophorectomy, or post-tubal ligation. Documented hysterectomy or oophorectomy must be confirmed with medical records of the actual procedure or confirmed by an ultrasound, magnetic resonance imaging (MRI) or computed tomography (CT) scan. Tubal ligation must be confirmed with medical records of the actual procedure.

• Female participants of childbearing potential must agree to use 1 highly effective form of contraception with their partner starting with the screening visit through 150 days after the last dose of study therapy.
• Participant has an Eastern Cooperative Oncology Group (ECOG) performance status of <= 2 for Part 1 and <= 1 for Part 2.
• Participant has an adequate organ function.
• Participants with known human immunodeficiency virus (HIV) infection are allowed with following requirements:

Must be on an uninterrupted combination antiretroviral therapy regimen for at least 3 months prior to Screening, with combination antiretroviral therapy regimen consistent with locally recommended guidelines

• Participants with history of Centers for Disease Control and Prevention (CDC) Stage 3 disease (CDC, 2014; also known as acquired immunodeficiency syndrome [AIDS]- defining disease) are allowed if AIDS-defining disease has been treated and cured or is stable for ≥3 months prior to study entry. Cutaneous Kaposi’s Sarcoma not requiring systemic therapy is allowed.
• No history of HIV-associated non-Hodgkin lymphoma ≤5 years prior to study and no history of HIV-associated invasive cervical cancer
• No treatment with an HIV-1 immunotherapeutic vaccine within 90 days of Screening.

Participant has received prior therapy with an anti- programmed death receptor 1 (anti-PD-1), anti-PD-1- ligand-1 (anti-PD-L1), or anti-PD-1 ligand-2 (anti-PD- L2) agent.

• Participant has a known uncontrolled CNS metastasis and/or carcinomatous meningitis.
• Participant has a known additional malignancy that progressed or required active treatment within the last 2 years. Exceptions include basal cell carcinoma of the skin, squamous cell cancer (SqCC) of the skin that has undergone potentially curative therapy, or in situ cervical cancer, or other neoplastic condition which has undergone curative therapy and is considered cured by the investigator.
• Participant is considered a poor medical risk due to a serious, uncontrolled medical disorder, nonmalignant systemic disease or active infection requiring systemic therapy. Specific examples include, but are not limited to, active, non-infectious pneumonitis; uncontrolled ventricular arrhythmia; recent (within 90 days) myocardial infarction; uncontrolled major seizure disorder; unstable spinal cord compression; superior vena cava syndrome; or any psychiatric or substance abuse disorders that would interfere with cooperation with the requirements of the study (including obtaining informed consent).
• Participant is pregnant or breastfeeding or expecting to conceive children within the projected duration of the study, starting with the Screening Visit through 150 days after the last dose of study treatment.
• Participant has a diagnosis of immunodeficiency or is receiving systemic steroid therapy or any other form of immunosuppressive therapy within 7 days prior to the first dose of study treatment.
• Participant has a documented presence of hepatitis B surface antigen [HBsAg] at screening or within 3 months prior to the first dose of study intervention. Participants with a negative HbsAg and positive hepatitis B virus core antibody (HBcAb) result are eligible only if HBV DNA is negative.
• Participant has an active autoimmune disease that has required systemic treatment in the past 2 years (i.e., with use of disease- modifying agents, corticosteroids, or immunosuppressive drugs). Replacement therapy (e.g., thyroxine, insulin, or physiologic corticosteroid replacement therapy for adrenal or pituitary insufficiency, etc.) is not considered a form of systemic treatment. Use of inhaled steroids, local injection of steroids, and steroid eye drops are allowed.
• Participant has as history of interstitial lung disease.
• Participant has not recovered (i.e., to <= Grade 1 or to Baseline) from radiation- and chemotherapy-induced AEs or received transfusion of blood products (including platelets or red blood cells) or administration of colony-stimulating factors (including granulocyte-colony stimulating factor [G-CSF], granulocyte macrophage colony-stimulating factor [GM-CSF] or recombinant erythropoietin) within 3 weeks prior to the first dose of study drug.
• Participant has participated in a study of an investigational agent and received study therapy or used an investigational device within 4 weeks prior to the first dose of study drug.
• Participant has received prior anticancer therapy (chemotherapy, targeted therapies, radiotherapy, or immunotherapy) within 21 days prior to study Day 1
• Participant has not recovered adequately (<= Grade 1) from AEs and/or complications from any major surgery prior to starting therapy.
• Participant has received a live vaccine within 14 days of planned start of study therapy.
• Participant has a known hypersensitivity to dostarlimab components or excipients.
• For Cohort G, participants will not be eligible if they meet the following criteria: