CG Therapeutics isn't just another player in the growing - though oft-troubled - cancer vaccine space.

For one thing, the young Seattle-based firm aims to distinguish itself from other companies by developing an antibody-mediated therapeutic vaccine, as opposed to the T-cell-mediated approach that has spelled trouble for firms such as New York-based Antigenics Inc. and the now-defunct CancerVax Corp., though investors remain optimistic on the future of Provenge (sipuleucel T), a T-cell-mediated immunotherapy from Seattle-based Dendreon Corp., which received an FDA approvable letter requesting additional data in May.

For another, CG Therapeutics is built on extensive research and development work - primarily from Ohio State University with further vaccine delivery work added by Royer Biomedical Inc., of Frederick, Md. - targeting hCG, a hormone found on cancer cells.

It was a "combination of academic work and corporate work," said CG CEO Jon Green, that led to the company's formation in August 2005 with the aim of "bringing to market therapies that neutralize hCG in cancer."

Human chorionic gonadotropin, or hCG, has long been known for its role during pregnancy as the hormone that an embryo produces to protect itself from attack by the mother's immune system. HCG later was detected on cancer cells, where it was found to do much the same thing. In the case of tumors, hCG serves as a shield to guard against an immune response and assists in tumor growth. While hCG is not absolutely required for all cancer cells, its presence "does correlate with tumor growth and metastasis," Green told BioWorld Today.

Prior work with an earlier version of the vaccine, including a Phase II trial, showed that it can neutralize hCG and "confer an increased median survival in colorectal cancer patients," Green said. The new version, designated CG201, is "much more potent," and like the earlier form, "has no systemic side effects" since hCG is not found on healthy cells.

To date, the vaccine also has shown evidence of an anti-angiogenic mechanism of action, and it's "clear that hCG is a direct stimulator of blood vessel growth," said Thomas Hopp, vice president of research and development. That means it could target the same angiogenesis pathway hit by blockbuster cancer drug Avastin (bevacizumab, Genentech Inc.)

CG is gearing up to start advanced Phase II trials, initially investigating CG201 in colorectal cancer and non-small-cell lung cancer. Both trials will test the vaccine in combination with standard therapy vs. standard therapy alone. The firm, which has raised $3.5 million in seed funding, is in the process of raising its Series A round to fund those studies, expected to start in the middle of 2008.

Unlike some of its competitors in the cancer vaccine space, namely the T-cell-mediated vaccines, CG201 does not work by stimulating the immune system to produce T cells. The problem with that approach, Green said, is that those T-cells "might be down-regulated or turned off, possibly as a result of hCG," before they attack the cancer cell. CG201, on the other hand, works by stimulating the immune system to produce antibodies, and ideally, will yield antitumor effects comparable to the likes of Avastin, Herceptin (trastuzumab, Genentech) and Erbitux (cetuximab, ImClone Systems Inc.).

However, CG said it's possible that the two types of vaccines might end up working in combination, with the hCG-targeting vaccine knocking down the tumor's shield to expose it to the attacking T cells. Executives said they are "certainly open" to discussions with other cancer vaccine firms down the road.

CG, which operates with about a dozen employees and works with outside contract research organizations and manufacturers, likely will "remain relatively small," Green said. As to the company's business development plan, he said the firm is flexible with regards to future growth and will be on the look-out for the "best deal for shareholders."

Most recently, CG named Christopher Henney chairman of its board. Henney, who co-founded the biotech firms Immunex Corp. (now part of Amgen Inc.), ICOS Corp. (now part of Eli Lilly & Co.) and Dendreon, "brings a lot of experience," Green said, "and we're happy to have him join."

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