Tusamitamab is an investigational monoclonal antibody designed to target CEACAM5 (carcinoembryonic antigen-related cell adhesion molecule 5), a protein often overexpressed in certain solid tumors, particularly non-small cell lung cancer (NSCLC) and gastrointestinal cancers such as colorectal and gastric cancers.

Its primary application is in targeted cancer therapy, where it binds specifically to CEACAM5 on the surface of tumor cells. This binding enables selective delivery of cytotoxic agents when tusamitamab is used as part of an antibody-drug conjugate (ADC). In clinical development, it has been conjugated to a cytotoxic payload (e.g., maytansinoid DM4) to form a drug known as tusamitamab ravtansine (also called SAR408701). This ADC is internalized upon binding, releasing the cytotoxic agent inside the cancer cell, leading to cell death while minimizing damage to healthy tissues.

Tusamitamab-based therapies are being evaluated in clinical trials for patients with advanced or metastatic CEACAM5-positive cancers, especially those who have limited treatment options. The selectivity of tusamitamab for CEACAM5-expressing tumors makes it a promising tool for precision oncology, with potential applications in both treatment and patient stratification based on CEACAM5 expression levels.