Pfizer and CytomX Therapeutics have entered into a global strategic collaboration worth up to $635 million to develop and commercialize several new targeted anticancer drugs using the biotech’s probody drug conjugate technology.

CytomX says its probody technology offers a new and different approach to developing safer and more effective antibody-drug conjugates, and addressing targets in cancer and inflammation that are currently considered undruggable.

The South San Francisco-based biotech’s drug conjugates are engineered to combine cytotoxic agents with masked probodies that remain inert in healthy tissue but are activated in the tumor microenvironment. The masked probody drug conjugates are activated by the dysregulated protease activity, a feature of many disease states, and therefore can target very disease-specific tissues.

Under the terms of their agreement, Pfizer has exclusive rights to pursue development and commercialization of select probody drug conjugates in oncology. Specific targets have not been disclosed. The companies will work together on preclinical research and Pfizer will be responsible for development and potential commercialization of any selected compounds. CytomX will be eligible to receive approximately $25 million in upfront, research reimbursement and preclinical milestone payments as well as up to $610 million in regulatory and sales milestone, plus tiered royalties.

For Pfizer, CytomX is the latest in a string of early-stage collaborations the Big Pharma has struck over the past year as it continues to externalize early stage research. “This partnership is a great example of how Pfizer is seeking to innovate new capabilities in cutting-edge science and technology platforms with the aim of delivering safer, more effective cancer medicines to patients,” says Robert Abraham, senior vice president and chief scientific officer, Pfizer’s Oncology Research Unit. “Pfizer’s investment in CytomX’s emerging probody platform is an important component of our overall strategic focus to advancing the next generation of ADCs and reflects the disruptive potential of this approach.”

The deal with Pfizer is CytomX’s first pharma collaboration. The company was formed in 2010 from a precursor company that was originally spun out of University of California, Santa Barbara in 2006. It has several pipeline candidates in preclinical development and is backed by Third Rock Ventures, Canaan Partners, and the Roche Venture Fund, which have invested $41 million in the company to date.