The purpose of the study is to test how well patients with advanced solid tumors respond to treatment with elimusertib (BAY1895344) in combination with pembrolizumab. In addition researchers want to find for patients the optimal dose of elimusertib in combination with pembrolizumab, how the drug is tolerated and the way the body absorbs, distributes and discharges the drug. The study medication, elimusertib, works by blocking a substance (ATR Kinase) which is produced by the body and is important for the growth of tumor cells. Pembrolizumab is an immunologic checkpoint blocker that promotes an immune response against the tumor.

Inclusion Criteria:

• Participant must be ≥18 years of age inclusive, at the time of signing the informed consent.
• Presence of the putative biomarkers of DDR deficiency in tumor and/or other tissues (dose escalation only).
• Participants must have histologically confirmed solid tumors .
• Eastern Cooperative Oncology Group performance status (ECOG-PS) of 0 to 1.
• Adequate bone marrow function as assessed by laboratory tests to be conducted within 7 days before the first dose of study intervention.
• Participants must have adequate kidney function, as assessed by the estimated glomerular filtration rate (eGFR) > 40 mL/min per 1.73 m*2 within 7 days before the first dose of study intervention.
• Participants must have adequate liver function as assessed by laboratory tests to be conducted within 7 days before the first dose of study intervention.
• Participants must have adequate coagulation, as assessed by laboratory tests as applicable, (to be conducted within 7 days before the first dose of study intervention) or be on stable anti-coagulation treatment.
• Adequate cardiac function per institutional normal measured by echocardiography (recommended) or multigated acquisition (MUGA) scan/cardiac MRI per institutional guidelines.
• Participants must have measurable disease (at least one measurable lesion) as per RECIST 1.1, or evaluable disease according to the Prostate Cancer Clinical Trials Working Group 3 (PCWG3) classification as applicable. Lesions situated in a previously irradiated area are considered measurable if progression has been demonstrated in such lesions

Exclusion Criteria:

• Ongoing infections of Common terminology criteria for adverse events (CTCAE) grade ≥2 not responding to therapy or active clinically serious infections.

• Participants with

  • Known human immunodeficiency virus (HIV)
  • Active Hepatitis B infection (positive for Hepatitis B surface antigen (HBsAg)/ Hepatitis B virus (HBV) DNA).
  • Active Hepatitis C infection (positive anti-HCV Antibody and quantitative HCV RNA results greater than the lower limits of detection of the assay).

• Active autoimmune disease (active defined as having autoimmune disease related symptoms and detectable autoantibodies) 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

• Diagnosis of immunodeficiency or participant is receiving chronic systemic steroid therapy (in dosing exceeding 10 mg daily of prednisone equivalent) or any other form of immunosuppressive therapy within 7 days prior to the first dose of study intervention. The use of physiologic doses of corticosteroids may be approved after consultation with the sponsor.

• Pleural effusion or ascites that causes respiratory compromise (CTCAE Grade ≥ 2 dyspnea).

• History of cardiac disease: congestive heart failure New York Heart Association (NYHA) class >II, unstable angina (angina symptoms at rest), new-onset angina (within the past 6 months before study entry), myocardial infarction within the past 6 months before study entry, or cardiac arrhythmias requiring anti-arrhythmic therapy (beta blockers, calcium channel blockers, and digoxin are permitted)

• Uncontrolled arterial hypertension despite optimal medical management (per investigator's opinion)

• Moderate or severe hepatic impairment, i.e., Child-Pugh class B or C.

• History of organ allograft transplantation

• Evidence or history of bleeding disorder, i.e., any hemorrhage / bleeding event of CTCAE Grade > 2 within 4 weeks before the first dose of study intervention

Availability of this study's data will later be determined according to Bayer's commitment to the EFPIA/PhRMA "Principles for responsible clinical trial data sharing". This pertains to scope, timepoint and process of data access. As such, Bayer commits to sharing upon request from qualified researchers patient-level clinical trial data, study-level clinical trial data, and protocols from clinical trials in patients for medicines and indications approved in the US and EU as necessary for conducting legitimate research. This applies to data on new medicines and indications that have been approved by the EU and US regulatory agencies on or after January 01, 2014.

Interested researchers can use www.vivli.org to request access to anonymized patient-level data and supporting documents from clinical studies to conduct research. Information on the Bayer criteria for listing studies and other relevant information is provided in the member section of the portal.