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Astellas Ends $1.7B CytomX Collaboration — But Stock Surges 75% on Other Drug
The Japanese pharma giant walked away from a six year T cell bispecific partnership as CytomX shares rallied on positive colorectal cancer data.
The Japanese pharma giant walked away from a six year T cell bispecific partnership as CytomX shares rallied on positive colorectal cancer data.
Astellas Pharma has terminated a six-year collaboration with CytomX Therapeutics for the development of T-cell engaging bispecific antibodies, ending a partnership that could have generated more than $1.68 billion in milestone payments for the South San Francisco-based biotech.
The collaboration, launched in March 2020, allowed Astellas to apply CytomX's Probody therapeutic platform to discover, develop, and commercialize novel T-cell engaging bispecific antibodies designed to fight cancer by targeting CD3 and tumor surface cell antigens.
Astellas paid CytomX an $80 million upfront and agreed to pay up to $1.6 billion in preclinical, clinical, and commercial milestones, plus tiered royalties ranging from high-single digit to mid-teen percentages. The company selected four targets under the agreement, with programs for three remaining active.
The first sign of trouble came in Q1 2025, when Astellas chose not to continue IND-enabling activities for the first collaboration target, instead prioritizing their second nominated target. In total, Astellas paid $20 million in milestone payments before ending the relationship.
"CytomX is currently assessing options to advance select targets previously covered under the Astellas collaboration as part of its ongoing research and development strategy," the company disclosed in its 2025 Form 10-K.
The end of the collaboration coincided with positive news for CytomX: its Probody drug conjugate varseta-M achieved a 32% overall response rate in a Phase I study for advanced colorectal cancer, sending shares surging 75% to a 52-week high.
CytomX's 2025 financials showed challenges: revenue tumbled 45% to $76.2 million from $138.1 million in 2024, blamed on completed collaborations with Bristol Myers Squibb and reduced work with Astellas, Moderna, and Regeneron. The company posted a $17.4 million net loss in 2025 versus $31.9 million net income in 2024.
The company ended 2025 with $137 million in cash, expected to fund operations through Q2 2027.
CytomX maintains other partnerships with Amgen, Bristol Myers Squibb, Moderna, and Regeneron.