desired target in the rodents’ tumors, while remaining stable and inactive while circulating through the bloodstream. So the company ended the year by showing its drug could be active in a living organism (instead of just tumors in a lab dish), and that they could be locally activated by specific disease-related enzymes in the vicinity of an EGFR-overexpressing tumor.
“We tied it up with a nice little bow for the December board meeting,” McCarthy says.
Of course, having some early success means that a lot more work needs to be done to carry the program forward. This spring, CytomX is working on various engineering tasks to come up with an optimized version of a targeted EGFR inhibitor, McCarthy says. The company has more toxicology studies to do, and has to test its drug in non-human primates. And while CytomX’s core intellectual property is in making the Probodies, it is looking for a partner with different skills to help soup up the molecules by binding them with potent toxins.
If CytomX can check those items off its to-do list soon, then it will be ready to plow ahead toward the clinic with an eye on raising the bar for safety and effectiveness in a very tough population of patients—those with EGFR-positive malignancies that also have mutant KRAS genes that fuel tumor growth too powerful for today’s drugs to handle. Presumably, if CytomX can make a drug that works for these patients, and doesn’t have the rash and gastrointestinal side effects of the others, it could have a best-in-class drug for a quite lucrative class.
It would be big news if CytomX, or anybody else, can pull off such a feat. Amgen’s former head of R&D recently told me that one of his biggest disappointments of the past decade was that Vectibix didn’t have as big an effect as he hoped, and didn’t help as many cancer patients as envisioned. But CytomX is so bullish on its approach that it is already thinking about how to avoid becoming a one-product company, by seeing if its technology can be exploited against other targets on cells that aren’t as validated by drugs like Erbitux and Vectibix. McCarthy says he’s excited by the idea of starting with EGFR, and building from there. “Once we hit our milestones, and we headed into the second half of the year, we had to look out three, four, five years and ask ourselves, what kind of company are we trying to build? We want to focus on areas where we can say, ‘without a Probody, you couldn’t do it.”
