A Phase II Trial of Neoadjuvant PD-1 Vaccine PD1-Vaxx in Operable MSI High Colorectal Cancer

This is a phase II, Bayesian Optimal Design, single arm, one cohort, open label, multi-centre study of neoadjuvant PD-1 vaccine PD1-Vaxx and surgical resection in adult patients with operable MSI-high colorectal cancer. All patients will be administered PD1-Vaxx intramuscularly into the deltoid region of the upper arm on days 1,15 and 29. Patients will undergo resection surgery within 21 days, but up to 42 days of completing trial treatment. The resection sample will be examined locally for pathological response within 28 days of surgical resection. Patient will then remain in active follow up for up to 2 years. Once the last patient has completed their last visit a check will be made on all patients to confirm their recurrence and survival status. The aim of the trial is to determine the major pathological response rates after administering neoadjuvant PD-1 vaccine PD1-Vaxx in operable MSI-high CRC patients.