Study of Peposertib in Combination With Capecitabine and RT in Rectal Cancer

Inclusion Criteria

• Participants who have an Eastern Cooperative Oncology Group Performance Status less than or equals to (<=) 1
• Participants who have histologically confirmed and localized resectable rectal cancer (Stage 3)
• Participants who received induction chemotherapy are allowed to be enrolled to this study except this induction is resulting in clinical complete response (cCR) or tumor progression
• Participants who have lower edge of the tumor located in rectum
• Adequate hematological, hepatic and renal function as defined in the protocol
• Male participants if they agree to the following during the study intervention period and for at least 12 weeks after the last dose of study intervention
• Female participants are eligible if not pregnant or breastfeeding
• Other protocol defined inclusion criteria could apply

Exclusion Criteria

• Participants with history of any other significant medical disease or psychiatric conditions that might in the assessment of the Investigator preclude safe participation in the study
• Participants with history of difficulty swallowing, malabsorption, or other chronic gastrointestinal disease or conditions that may hamper compliance and/or absorption of the study intervention
• Unstable cardiovascular function within 6 months prior to enrollment
• Hypertension uncontrolled by medication (ie, systolic blood pressure >= 150 millimeter of mercury (mmHg) and diastolic blood pressure >= 90 mmHg)
• Participants with history of other malignant disease within the past 5 years, other than successfully treated basal carcinoma of the skin or carcinoma in situ of the cervix
• Participants with known human immunodeficiency virus positivity, known active hepatitis (for example, hepatitis B virus or hepatitis C virus), current alcohol abuse, or cirrhosis
• Participants with ongoing active infection or treatment with a live attenuated vaccine within 4 weeks of dosing
• Participants with concomitant use of H2-blocker or proton pump inhibitors (PPIs) (or unable to stop at least 5 days prior to the first treatment). Note that calcium carbonate is acceptable
• Participation in any interventional clinical study within 28 days prior to Screening or during participation in this study
• Other protocol defined exclusion criteria could apply.