By Alex Keown


Over the past few years CytomX Therapeutics, Inc. has forged a number of developmental deals with big pharma, but this week Pfizer Inc. notified the Bay Area-based company of its intent to terminate its five-year-old oncology collaboration.

The news of Pfizer’s decision was buried at the end of CytomX’s 2017 year-end financial report. The two companies initially teamed up in 2013 to develop four Probody drug conjugate (PDC) targets for the treatment of cancer. The initial target the two companies worked on was Epidermal Growth Factor Receptor (EGFR) mutations, a highly validated oncology target expressed in multiple types of cancer. That program was terminated some time ago, with certain rights reverting to CytomX, the company said.

Now Pfizer has completely pulled out of the deal, ending hopes of a potential $635 million or more that CytomX could have garnered if the projects had met certain milestones, including commercialization. In its announcement, CytomX said Pfizer terminated the second and third targets that were part of the agreement during the first quarter of this year. Pfizer had previously declined to option the fourth target in the collaboration agreement, CytomX said. None of the four programs the two companies worked on had advanced to the clinical stage. CytomX did not disclose what the two other targets the companies worked on were.

CytomX’s probody therapeutics are designed to take advantage of unique conditions in the tumor microenvironment to enhance the tumor-targeting features of an antibody and reduce drug activity in healthy tissues, according to company information. Once activated, the probody therapeutics bind selectively to cells within tumor tissue with reduced binding to healthy tissue, potentially improving or creating a therapeutic window, according to company data.

While Pfizer has ended an arrangement with CytomX, the biotech has forged a number of other partnerships. Last year the company entered into a developmental agreement with Amgen and expanded a 2014 collaboration agreement with Bristol-Myers Squibb to use CytomX’s Probody platform for targets in oncology and non-oncology programs. CytomX had previously entered into a deal worth up to $500 million with AbbVie to co-develop commercialize Probody Drug Conjugates against CD71, also known as transferrin receptor 1 (TfR1).

Sean McCarthy, president and chief executive officer of CytomX Therapeutics, called 2017 a year of “tremendous execution,” with the initiation of Phase I/II studies for two wholly-owned and one partnered program. Looking at 2018 McCarthy said the company is anticipating data readouts from its PD-L1-targeting Probody therapeutic, CX-072, and its CD166-targeting Probody drug conjugate, CX-2009. Data from those clinical programs are expected in mid- and late 2018, respectively, the company said.

CX-072 is being explored in a Phase I/II trial as a monotherapy treatment and in combination with BMS’ Yervoy (ipilimumab) or Genentech’s Zelboraf (vemurafenib) in patients with cancer. CX-2009, a PDC that targets CD166, is being studied as a monotherapy in a Phase I/II trial in a subset of CD166-positive cancer types.

“We also expect to initiate clinical studies for two additional programs this year, resulting in five clinical-stage Probody therapeutic programs by year end. Our deepening pipeline of innovative therapeutics has the potential to make a meaningful difference in the lives of people with cancer,” McCarthy said in a statement. 



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