| E.1 Medical condition or disease under investigation | 
| E.1.1 | Medical condition(s) being investigated | 
| • Histologically confirmed carcinoma of the rectum • Suitable for local therapy with curative intent
 • Medical need for a standard neoadjuvant CRT
 • Suitable to withstand a course of standard neoadjuvant CRT
 |  | 
| E.1.1.1 | Medical condition in easily understood language | 
| • Rectal cancer • Medical need for a standard preoperative chemoradiotherapy
 • Suitable to withstand a course of  standard preoperative chemoradiotherapy
 |  | 
| E.1.1.2 | Therapeutic area | Diseases [C] - Cancer [C04] | 
| MedDRA Classification | 
| E.1.2 Medical condition or disease under investigation | 
| 
| E.1.2 | Version | 20.0 |  
| E.1.2 | Level | PT |  
| E.1.2 | Classification code | 10038038 |  
| E.1.2 | Term | Rectal cancer |  
| E.1.2 | System Organ Class | 10029104 - Neoplasms benign, malignant and unspecified (incl cysts and polyps) |  | 
| E.1.2 Medical condition or disease under investigation | 
| 
| E.1.2 | Version | 20.0 |  
| E.1.2 | Level | LLT |  
| E.1.2 | Classification code | 10038045 |  
| E.1.2 | Term | Rectal cancer NOS |  
| E.1.2 | System Organ Class | 10029104 - Neoplasms benign, malignant and unspecified (incl cysts and polyps) |  | 
| E.1.3 | Condition being studied is a rare disease | No | 
| E.2 Objective of the trial | 
| E.2.1 | Main objective of the trial | 
| Safety, tolerability and feasibility of standard neoadjuvant CRT with sequential ipilimumab and nivolumab following surgical resection. |  | 
| E.2.2 | Secondary objectives of the trial | 
| • Radiographic response determined by magnetic resonance imaging-assessed tumor regression grade (mrTRG) • Pathological response determined by tumor regression grade (TRG) and tumor stage (ypT and ypN stage).
 |  | 
| E.2.3 | Trial contains a sub-study | No | 
| E.3 | Principal inclusion criteria | 
| • 18 years of age and older • All sexes
 • Histologically confirmed carcinoma of the rectum
 • Suitable for local therapy with curative intent
 • Medical need for a standard neoadjuvant CRT
 • Suitable to withstand a course of standard neoadjuvant CRT
 • Written informed consent form (ICF) for participation in the study
 • Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1
 |  | 
| E.4 | Principal exclusion criteria | 
| • Metastatic disease that is considered incurable by local therapies • Previous surgery of the tumor other than biopsy
 • Pregnancy, breastfeeding or expectancy to conceive
 • Disagreement of participants with reproductive potential to use
 contraception throughout the study period and for up to 180 days
 after the last dose of study therapy
 • Prior therapy with anti-CTLA-4, anti-PD-1, anti-PD-L1, anti-PD-L2 or
 any other agent directed against co-inhibitory T cell receptors or
 has previously participated in clinical studies with immunotherapy
 • Any contraindication according to the official medical information
 of Ipilimumab or Nivolumab
 • Live vaccine within 30 days prior to the first dose of study therapy
 • Hepatitis B or C
 • Human immunodeficiency virus (HIV)
 • Immunodeficiency
 • Allogeneic tissue or solid organ transplantation
 • Autoimmune disease that has required systemic therapy in the past
 2 years with modifying agents, steroids or immunosuppressive
 drugs
 • Systemic steroids or any other form of immunosuppressive therapy
 within 7 days prior to the first dose of study treatment
 • Active non-infectious pneumonitis
 • Active infection requiring systemic therapy
 • Treatment with botanical preparations (i.e. herbal supplements or traditional Chinese medicines) intended for general health support or to treat the disease under study within 2 weeks prior to randomization/treatment
 • Participants with serious or uncontrolled medical disorders
 • Uncontrolled or significant cardiovascular disease (myocardial infarction, uncontrolled angina, any history of clinically significant arrhythmias, QTc prolongation in males > 450 ms and > 470 ms in
 females, participants with history of myocarditis)
 • Allergies and adverse drug reaction (history of allergy or hypersensitivity to study drug components, contraindications to
 any of the study drugs of the chemotherapy regimen)
 • Other exclusion criteria: Prisoners or participants who are involuntarily incarcerated, participants who are compulsorily detained for treatment of either a psychiatric or physical (i.e.
 infectious disease) illness
 • White blood cells < 2000/μL (SI: < 2.00 × 109/L)
 • Neutrophils < 1500/μL (SI: < 1.50 × 109/L)
 • Platelets < 100 × 103/μL (SI: < 100 × 109/L) (transfusions not
 permitted within 72 h prior to qualifying laboratory value)
 • Hemoglobin < 9.0 g/dl (SI: < 90 g/L) (transfusions not permitted
 within 72 h prior to qualifying laboratory value)
 • Serum creatinine > 1.5 × upper limit of normal (ULN) or calculated
 creatinine clearance < 50 ml/min (using the Cockcroft-Gault
 formula)
 • AST/ALT: > 3.0 × ULN
 • Total bilirubin > 1.5 × ULN (except participants with Gilbert Syndrome who must have a total bilirubin level of < 3.0 × ULN)
 • Troponin T (TnT) or I (TnI) > 2 × institutional ULN. TnT or TnI levels
 between > 1 to 2 × ULN will be permitted to participate in the study if a repeat assessment remains  2 × ULN and participant undergoes a cardiac evaluation. When repeat levels within 24 h are not available, a repeat test should be conducted as soon as possible.
 |  | 
| E.5 End points | 
| E.5.1 | Primary end point(s) |  | 
| E.5.1.1 | Timepoint(s) of evaluation of this end point |  | 
| E.5.2 | Secondary end point(s) | 
| See secondary objectives. |  | 
| E.5.2.1 | Timepoint(s) of evaluation of this end point |  | 
| E.6 and E.7 Scope of the trial | 
| E.6 | Scope of the trial | 
| E.6.1 | Diagnosis | No | 
| E.6.2 | Prophylaxis | No | 
| E.6.3 | Therapy | No | 
| E.6.4 | Safety | Yes | 
| E.6.5 | Efficacy | No | 
| E.6.6 | Pharmacokinetic | No | 
| E.6.7 | Pharmacodynamic | No | 
| E.6.8 | Bioequivalence | No | 
| E.6.9 | Dose response | No | 
| E.6.10 | Pharmacogenetic | No | 
| E.6.11 | Pharmacogenomic | No | 
| E.6.12 | Pharmacoeconomic | No | 
| E.6.13 | Others | No | 
| E.7 | Trial type and phase | 
| E.7.1 | Human pharmacology (Phase I) | No | 
| E.7.1.1 | First administration to humans | No | 
| E.7.1.2 | Bioequivalence study | No | 
| E.7.1.3 | Other | No | 
| E.7.1.3.1 | Other trial type description |  | 
| E.7.2 | Therapeutic exploratory (Phase II) | Yes | 
| E.7.3 | Therapeutic confirmatory (Phase III) | No | 
| E.7.4 | Therapeutic use (Phase IV) | No | 
| E.8 Design of the trial | 
| E.8.1 | Controlled | No | 
| E.8.1.1 | Randomised | Yes | 
| E.8.1.2 | Open | Yes | 
| E.8.1.3 | Single blind | No | 
| E.8.1.4 | Double blind | No | 
| E.8.1.5 | Parallel group | No | 
| E.8.1.6 | Cross over | No | 
| E.8.1.7 | Other | No | 
| E.8.2 | Comparator of controlled trial | 
| E.8.2.1 | Other medicinal product(s) | No | 
| E.8.2.2 | Placebo | No | 
| E.8.2.3 | Other | No | 
| E.8.3 | The trial involves single site in the Member State concerned | No | 
| E.8.4 | The trial involves multiple sites in the Member State concerned | Yes | 
| E.8.4.1 | Number of sites anticipated in Member State concerned | 4 | 
| E.8.5 | The trial involves multiple Member States | No | 
| E.8.6 Trial involving sites outside the EEA | 
| E.8.6.1 | Trial being conducted both within and outside the EEA | No | 
| E.8.6.2 | Trial being conducted completely outside of the EEA | No | 
| E.8.7 | Trial has a data monitoring committee | Yes | 
| E.8.8 | Definition of the end of the trial and justification where it is not the last
                        visit of the last subject undergoing the trial |  | 
| E.8.9 Initial estimate of the duration of the trial | 
| E.8.9.1 | In the Member State concerned years | 2 | 
| E.8.9.1 | In the Member State concerned months |  | 
| E.8.9.1 | In the Member State concerned days |  |