Regeneron's four-year-old collaboration with CytomX Therapeutics (Nasdaq: CTMX) has been significantly expanded, with the companies announcing a broadened agreement that could push total milestone exposure to approximately USD 4 billion. The San Francisco-based CtyomX and Regeneron are working on conditional activation as a solution to the toxicity limitations of T-cell engaging bispecifics in solid tumors. CytomX will now receive a USD 37 million target selection payment for two additional programs, while Regeneron secures options on up to six further targets. Regeneron retains full responsibility for preclinical, clinical, and commercial development costs.
Under the expanded structure, total potential payments of USD 4 billion span target nomination fees, preclinical and clinical milestones, regulatory approvals, and commercial sales thresholds. CytomX is also eligible for tiered global net sales royalties. The original collaboration was initiated in 2022, and included a USD 30 million upfront payment and up to USD 2 billion in milestone commitments from Regeneron to CytomX.
Deal context
The programs combine CytomX's Probody platform with Regeneron's Veloci-Bi bispecific antibody technology. CytomX's approach involves engineering a masking peptide onto the antibody that remains inactive in systemic circulation; proteases overexpressed in the tumor microenvironment cleave the mask, locally activating the bispecific. Applied to T-cell engagers, which simultaneously bind a tumor antigen and CD3 on T cells, this mechanism is intended to confine T-cell activation to the tumor site, reducing the cytokine release and on-target, off-tumor toxicity that has constrained conventional bispecific TCEs in solid tumors. All programs under the collaboration remain at the discovery and preclinical stage; no clinical candidates have been publicly identified.
CytomX has reported positive Phase I data for its lead proprietary asset, varsetatug masetecan, an EpCAM-directed Probody ADC in colorectal cancer, providing clinical evidence that the masking concept can widen the therapeutic window for targets previously considered undruggable due to normal tissue expression. That clinical validation supports the rationale for applying the same platform logic to bispecifics.