The NEOASIS study is an adaptive, pan-cancer, single-center, open-label, basket study assessing the efficacy of botensilimab and balstilimab in patients with resectable dMMR and pMMR solid tumors of various origins. Patients will be included in baskets according to tumor type and mismatch repair (MMR) status and will receive 2 cycles of immunotherapy followed by surgery. The trial will commence with two safety run-in cohorts: one for patients with dMMR tumors and one for patients with pMMR tumors that will run in parallel. These safety run-in cohort will be used to assess safety and feasibility of pre-operative botensilimab + balstilimab. Data from the safety run-in cohorts will be used to determine the dosing and scheduling to be used in the MMR-specific cohorts of the main study. Safety will be assessed according to dose limiting toxicities. In the run-in cohorts, the first five patients will receive botensilimab 25mg intravenously (IV) on Day1 plus balstilimab 450mg IV on Day1 and Day22. Patients 6-10 will receive botensilimab 50mg IV on Day1 plus balstilimab 450mg IV on Day1 and Day22 followed by surgery 8 weeks after registration. After full accrual of the run-in cohorts, MMR-specific baskets including a "other cancers" basket will start accrual with the optimal dose and schedule as determined in the safety run-in followed by surgery 8 weeks after registration. The MMR-specific baskets are designed with a Simon's 2 stage design in which first 8 patients will be included, if in the first 8 patients >2 Major pathological responses are reported (defined as =10% residual viable tumor) accrual of 10 more patients will continue for a total of 18 patients per basket.