Evalstotug (development code BA3071) is an investigational, conditionally active biologic (CAB) monoclonal antibody being developed for cancer immunotherapy. It is designed as a novel anti-CTLA-4 therapy with an integrated safety switch. Unlike traditional CTLA-4 inhibitors (e.g., ipilimumab), which are constitutively active and can cause significant systemic immune-related adverse events (irAEs), evalstotug is engineered to be active only within the acidic tumor microenvironment (TME). At the near-neutral pH of healthy tissues, it remains in a mostly inactive state with minimal target binding. However, in the acidic conditions often found in tumors, the antibody undergoes a conformational change, exposing its active binding site and allowing it to potently block the CTLA-4 pathway locally. This design aims to concentrate the immune-stimulating effects at the tumor site while sparing healthy tissues, thereby improving the therapeutic index.