CytomX - 2013 Fierce 15

Escalating the antibody arms race

Based: South San Francisco
Founded: 2008
CEO: Sean McCarthy
Clinical focus: Cancer, inflammation, plus

The scoop: Antibodies are old hat in today's biotech. So the focus now is on new and better (and faster). CytomX sprung from the labs of the University of California, Santa Barbara (UCSB). And they've dubbed their next-level antibodies Probodies--whipped-up therapeutics that can be more potent than what's available today. The company recently won some substantial support from Pfizer ($PFE) to push their work ahead.

What makes CytomX fierce: CytomX's innovation was to extend the classic antibody--a Y-shaped protein that can be designed to hunt down specific targets--"so the new end terminus is a peptide that blocks the antibody's ability to bind to an antigen until it's clipped off by a disease-associated enzyme," says CEO Sean McCarthy. "That's the magic here. Along with the disease-specific linker or substrate that allows the local activation, the unmasking of the Probody. That's the concept that came out of UCSB."

Their lead program is focused on the Notch pathway activated by one of the Notch ligands, Jagged, which have been implicated in a number of tumors. There's preclinical data coming out in October, but the CEO emphasizes that all of their work underscores the fact that their therapeutic is both potent and well-tolerated--the twin goals of current-day oncology R&D. Another target is EGFR, a big market in the cancer field.

"Our approach is a disruptive approach to how we think of antibody targets," says McCarthy, a scientist who came up the biotech management ladder on the business development side of the industry. "The low-hanging fruit has been taken and the field is looking for new target ideas."

Pfizer illustrated that avid interest in new targets perfectly when it signed on for a $635 million pact--including $25 million in upfront cash, R&D support and near-term milestones--in June. The deal puts CytomX's platform to work designing Probody conjugates--its antibody linked to a cytotoxic agent--for some targets of the pharma giant's choosing.   

"As you can imagine, the announcement of the Pfizer pact has raised our profile in the community," says McCarthy. That deal laid the foundation for more partnership talks, leaving the biotech with a good shot at one more pact, at least, in the next year.

The partnership money builds on a steady flow of venture cash. Third Rock and Roche Ventures came in with a $30 million B round in 2010, back when Nancy Stagliano (now CEO at iPierian) helmed the company. That round was expanded with another $11 million from Canaan Partners.

McCarthy and his team of 30 full-timers have been having a good year, and they like to take a breather at the end of "beer Fridays" to relax. On the Friday afternoon McCarthy talked with FierceBiotech, though, the company was preparing for a wine tasting.

It's good to keep mixing things up a bit when you're feeling disruptive.

Investors: Third Rock, Roche Ventures, Canaan

For more:
Pfizer turns to upstart CytomX for $635M deal on armed antibody tech
Third Rock leads $30M round for antibody upstart

-- John Carroll (email)

CytomX - 2013 Fierce 15