Combining DCSZ11 With Radiation and Chemotherapy as Neoadjuvant Treatment for pMMR Locally Advanced Rectal Cancer

Inclusion Criteria: * Age ≥18 years. * Eastern Cooperative Oncology Group (ECOG) performance status 0 - 1. * Rectal cancer (with tumor tissue present at or below the peritoneal reflection) as determined by MRI pelvis or endoscopic ultrasound. * Have histologically proven mismatch repair proficient (pMMR) or microsatellite stable (MSS) rectal adenocarcinoma. * Must not have received any prior systemic treatment or radiation. * Patients have the following clinical staging: * cT4 any node status * Any T stage cN2 node status * Any T or N status, evidence of suspicious lateral lymph nodes \> 10 mm in size in short axis * Evidence of extramural vascular invasion on MRI pelvis * Absence of distant metastases on CT or MRI imaging * Patients must have adequate organ and marrow function defined by study-specified laboratory tests and procedures. * Left ventricular ejection fraction (LVEF) assessment with documented LVEF ≥ 50% by either TTE or Multigated Acquisition (MUGA) (TTE preferred) within 6 months from first study drug administration. * For both Women and Men, must use acceptable form of birth control while on study. * Ability to understand and willingness to sign a written informed consent document. Exclusion Criteria: * Have received an investigational agent or used an investigational device within 28 days of the first dose of study drug. * Have expected to require any other form of systemic or localized antineoplastic therapy while on study. * Have had surgery wit…