OncoMed Pharmaceuticals Inc. raised $13.9 million in its first financing round to fund drug discovery efforts against cancer stem cells, which are believed to cause the growth and metastasis of tumors.

It was the first major round of financing for OncoMed since it was founded in 2004 by Michael Clarke and Max Wicha of the University of Michigan, who discovered a class of tumor cells that appeared capable of long-term self-renewal.

"Dr. Clarke found that you could take epithelial tumors, like breast, colon or lung cancer, and separate the cancer cells into tiny populations based on their surface markers," said James Woody, CEO of OncoMed. After injecting the separated cells into immunosuppressed animals, scientists found that "one group would create really dramatic tumors in animals, while all the other groups would grow for a little bit and then stop."

That led to the discovery of a small percentage - maybe about 5 percent - of tumor cells that were capable of continually renewing and replicating, Woody said, adding that they became known as cancer stem cells, or tumorgenic cells.

"We've finally gotten to what we think is the really bad actor here," he told BioWorld Today. "This is the one that causes the tumor to keep growing, and the one that metastasizes and ultimately leads to the death of the patient."

Recent studies also have suggested that existing therapies might be targeting only nontumorgenic cells, which make up the bulk of tumors, but are not eliminating the cancer stem cells.

"This answers a lot of questions about why tumors recur even when patients are undergoing chemotherapy," Woody said. "It explains how the disease can be dormant for a while, and, all of a sudden, just take off."

OncoMed, headquartered in Mountain View, Calif., plans to use proceeds to identify cancer stem cells and develop monoclonal antibodies and small molecules to target them. Over the next four months, the company will concentrate on determining its long-term strategy for therapeutic development, such as whether OncoMed will focus on creating a treatment adjunctive to existing chemotherapy or will plan to combine its own products for a single therapy.

The company will be working with its scientific and clinical advisory board to get "an idea of what the first clinical trials might look like," Woody said.

Funds from the Series A also will go toward building up the firm's scientific staff. The money should take OncoMed into next year's second quarter, at which time an antibody should be selected to begin moving to the clinic. The company then might consider conducting a Series B round.

OncoMed, which has about 20 employees, also has a diagnostic division aimed at identifying patients with cancer stem cell types that are particularly aggressive. The diagnostic tools would allow doctors to determine which patients need treatment targeted against cancer stem cells.

In addition, the company has established a library of antibodies that are capable of binding to the cell-surface proteins expressed on cancer stem cells. Because OncoMed is a small company, it might consider partnering some of the antibodies that it is not able to take into the clinic on its own, Woody said.

The Series A round was led by venture capital firms, including San Francisco-based Latterell Venture Partners, Summit, N.J.-based The Vertical Group and US Venture Partners and Morgenthaler Ventures, both of Menlo Park, Calif.

In addition to the financing, OncoMed recently appointed members to its newly formed board. Woody, who was named founding chairman, will be joined by: Laurence Lasky, general partner at Latterell Venture Partners; Jonathan Root, general partner at USVP; James Broderick, general partner of Morgenthaler Ventures; and Jack Lasersohn, of The Vertical Group.