Tuvusertib (M1774) in Participants With Metastatic or Locally Advanced Unresectable Solid Tumors (DDRiver Solid Tumors 301)

Inclusion Criteria

• •Participants with locally advanced or metastatic disease that is refractory to standard therapy or for which no standard therapy is judged appropriate by the Investigator which may convey clinical benefit
• •Eastern Cooperative Oncology Group (ECOG) Performance Status less than or equal to (\<=) 1
• •Participants with clinically controlled brain metastases, which is defined as individuals with central nervous system metastases that have been treated for, are asymptomatic, and have discontinued steroids (for the treatment of brain metastases) for greater than (\>) 28 days may be enrolled
• •Participants with meningeal carcinomatosis are excluded
• •In Part A3, measurable disease according to Response Evaluation Criteria in Solid Tumors (RECIST) Version 1.1
• •Part A3: Participants with presence of loss of function mutations in the genes for ARID1A, ATRX and /or DAXX and ATM
• •Contraceptive use by males or females will be consistent with local regulations on contraception methods for those participating in clinical studies
• •Adequate hematological, hepatic, and renal function as defined in the protocol
• •Female participants are not pregnant or breastfeeding
• •Part B1:
• •Subpart B1a: Participants with Baseline Body weight \< 77 kg or platelets \<150,000 cubic per millimeter (mm\^3) Subpart B1b: Participants with Baseline Body weight \>= 77 kg and platelets \>=150,000 mm\^3 will be included
• •Treatment with live or live attenuated vaccine within 30 days of dosing (non-replicating vector vaccines are permitted)
• •Part B1 only: participants diagnosed with hereditary diseases characterized by genetic defects of DNA repair mechanisms, including ataxia telangiectasia, Nijmegen breakage syndrome, Werner syndrome, Bloom Syndrome, Fanconi anemia, xeroderma pigmentosum, Cockayne syndrome, and trichothiodystrophy
• •Any other clinical condition, uncontrolled concurrent illness, or other situation which in the Investigator's opinion would not make the participant a good candidate for the clinical study including or may potentially impact the absorption of M1774, such as (but not limiting to) significant small bowel resection or gastric surgery and exocrine pancreatic insufficiency requiring pancreatic enzyme replacement therapy
• •Prohibited concomitant medication, as per Protocol
• •Another investigational drug within 28 days or 5 half-lives, whichever is shorter, prior to start of administration of study intervention
• •Prior use of Ataxia telangiectasia mutated and Rad3-related (ATR) inhibitor and/or Checkpoint kinase 1 (CHK1) inhibitor
• •Participants who cannot comply with restrictions for medications or food
• •Part B1 only: Participants with a known history of acute myeloid leukemia (AML) or myelodysplastic syndromes (MDS), and prostate cancer