Pfizer has terminated its five-year-old partnership with CytomX Therapeutics to use its Probody™ drug-development platform to develop and commercialize several antibody–drug conjugates (ADCs) for cancer, CytomX has acknowledged.
That partnership was originally envisioned to pay CytomX up to $635 million-plus, including milestone payments and royalties.
In announcing full-year 2017 financial results yesterday, CytomX said Pfizer notified the company on Tuesday of its intent to end the companies’ research collaboration, option, and license agreement.
The companies agreed to develop up to four Probody–drug conjugates (PDCs), which according to CytomX are ADCs engineered to combine cytotoxic agents with masked “Probodies”—fully recombinant, masked antibodies that remain inert in healthy tissue but are activated specifically in tumors and other disease microenvironments.
None of the programs in CytomX’s collaboration with Pfizer ever advanced into clinical phases. The first program was a PDC designed to target epidermal growth factor receptor (EGFR), but Pfizer ended that program earlier, returning rights to CytomX.
Pfizer also previously declined its option to select a fourth target by letting that option lapse in May 2016, leaving the companies with EGFR and two other undisclosed target programs.
“In the termination letter, Pfizer indicated that it was terminating the collaboration agreement because it had decided not to pursue the two targets it had previously selected for development, which were the last two remaining programs under the collaboration agreement,” CytomX disclosed in its Form 10-K Annual Report for 2017, filed yesterday.
As a result, CytomX added, it will no longer be eligible to receive up to $263.5 million in milestone payments consisting of:
- Up to $4.5 million upon exercise of the license options
- Up to $38 million from the achievement of development milestones for the research target programs
- Up to $101 million in milestone payments for the first commercial sale in various territories for up to three indications per research target program, and
- Up to $120 million in sales milestones payments for the research target programs.
Up-to-$635M Alliance Launched in 2013
Pfizer agreed to pay CytomX $25 million when the companies launched their partnership in June 2013. The $25 million consisted of up-front cash, as well as research reimbursement and payments tied to achieving preclinical milestones.
Pfizer also agreed to pay CytomX up to $610 million tied to achieving regulatory and sales milestones, plus tiered royalties reaching double digits on potential future sales.
Last year, CytomX said it will pursue development of a treatment targeting EGFR—an oncology target expressed on multiple human cancer types—as part of the up-to-$1.465 billion-plus collaboration it launched with Amgen in October 2017.
That partnership calls for the companies to codevelop a CytomX Probody T-cell-engaging bispecific antibody. At the time, CytomX cited preclinical studies showing that its Probody versions of EGFRxCD3 bispecific therapeutics induced tumor regressions and increased the therapeutic window for the cancer target.
Amgen was one of two biopharma giants to launch or expand collaborations with CytomX last year. The other was Bristol-Myers Squibb (BMS), which last year agreed to pay CytomX $200 million upfront to add up to eight new candidates to an up-to-$1.2 billion Probody therapeutics collaboration launched in 2014.
Under the expanded partnership, BMS also agreed to pay CytomX up to $448 million in additional development, regulatory, and sales milestones for each collaboration target, plus tiered royalties on future product sales by BMS.