ChemoCentryx Begins Phase I Clinical Trial of Traficet-EN^™, a Novel Drug Candidate for the Treatment of Inflammatory Bowel Disease

ChemoCentryx Establishes World-Class Clinical Advisory Board for IBD

January 13, 2004; San Carlos, Calif. — ChemoCentryx, Inc. today announced that it has initiated a Phase I clinical trial to evaluate its novel drug candidate for the treatment of inflammatory bowel disease (IBD). The compound, known as Traficet-EN^™, is a novel, orally active anti-inflammatory agent that targets a chemokine receptor protein implicated in both Crohn's disease and ulcerative colitis, the two principal forms of IBD. Initial pharmacokinetic, safety and toxicity clinical data as demonstrated at multiple dosing levels will be presented on January 14th at the 22nd Annual JPMorgan Healthcare Conference in San Francisco.

Two Phase I clinical trials are being conducted in 72 healthy adult volunteers in the United Kingdom. The trials are designed to assess the safety and pharmacokinetic properties of the Traficet-EN^™ product, first in a single dose regimen, and subsequently with multiple doses. Both studies are scheduled to be completed in the second quarter of 2004.

"The initiation of Phase I clinical trials with Traficet-EN^™ is an important milestone for ChemoCentryx. This internal program represents the second new drug candidate stemming from ChemoCentryx research and development to enter clinical trials," said Thomas J. Schall, Ph.D., President and CEO of ChemoCentryx. "ChemoCentryx has achieved rapid success in translating our expertise in the chemokine system into viable drug candidates. The company continues to execute on its plan of advancing a compound into the clinic every 12 to 18 months, with a total of three compounds in clinical development by early 2005. Separately, we are extremely pleased to have such internationally recognized experts in the field of IBD serve on our Clinical Advisory Board."

ChemoCentryx also announced that the company has established a five-member Clinical Advisory Board composed of some of the world's leading experts in the field of IBD. Members of the ChemoCentryx Clinical Advisory Board include: Stephen Hanauer, M.D., Professor of Medicine and Clinical Pharmacology and Chief, Section of Gastroenterology and Nutrition, University of Chicago Pritzker School of Medicine; Michael Kamm, M.D., Professor of Gastroenterology and Director of Physiology Unit, St Mark's Hospital, Harrow, England; William Sandborn, M.D., Gastroenterology & Hepatology, Head, Inflammatory Bowel Disease, Mayo Clinic, Rochester, Minnesota; Stephan Targan, M.D., Division Director of Gastroenterology, Inflammatory Bowel Disease Center and Immunobiology Institute, Cedars-Sinai Medical Center, Los Angeles; and Sander van Deventer, M.D., Ph.D., Professor of Gastroenterology, Academic Medical Center, University of Amsterdam, The Netherlands. The Clinical Advisory Board will provide guidance for ChemoCentryx's clinical development programs in IBD, including Traficet-EN^™ compound.

About Traficet-EN^™
Traficet-EN^™, a first-in-class small molecule drug, is designed to control the inappropriate immune response underlying IBD. By selectively binding to a chemokine receptor involved in the trafficking of lymphocytes to the bowel, Traficet-EN^™ compound has been shown to inhibit the migration of such cells to the intestinal mucosa in models of Crohn's disease and ulcerative colitis, thereby alleviating inflammation in the large and small intestine. Traficet-EN^™ has demonstrated efficacy in both therapeutic and prophylactic models of inflammatory bowel disease. Unlike existing therapeutics for IBD, many of which are taken by injection, ChemoCentryx has designed Traficet-EN^™ to be taken orally once a day.

"Chemokine receptor antagonists show potential to occupy a prominent role in our arsenal of tools to combat serious and chronic inflammation," said Dr. Stephen Hanauer. "I am enthusiastic about the potential clinical benefits of this promising new compound, which could greatly improve the long-term outcomes for IBD patients."

"There exists a significant unmet need for a targeted treatment for the millions of patients suffering from IBD," commented Dr. Stephan Targan. "The availability of an oral therapy to treat inflammatory bowel disease would represent a major advance for patients, especially those who currently rely on injectable therapies. I look forward to contributing to the advancement of ChemoCentryx's promising new medicine through clinical development."

About Inflammatory Bowel Disease
IBD is a chronic, life-long condition that features relapsing inflammation of the gastrointestinal tract. IBD, including both Crohn's disease and ulcerative colitis, affects 1.7 million patients in the world's seven major pharmaceutical markets. Currently, no cure exists for IBD, and, in the most severe cases, accumulated damage to the intestine can result in the need for surgery. Despite the recent introduction of TNF inhibitors, many patients do not respond to current treatment options or develop serious long-term side effects. As a small molecule taken orally once a day, ChemoCentryx's Traficet-EN^™ compound is expected to provide advantages in terms of dosing and cost over existing therapeutics.

About ChemoCentryx
ChemoCentryx, Inc. discovers, develops and commercializes novel small molecule medicines for autoimmune diseases, inflammatory disorders, cancer and infectious disease. Recently, ChemoCentryx's first lead compound, an oral treatment for psoriasis, entered into Phase II clinical study initiated by the company's partner, Tularik. ChemoCentryx has advanced Traficet-EN^™, the company's orally active drug for inflammatory bowel disease, into Phase I clinical trials. Other programs include an orally active development candidate for rheumatoid arthritis and multiple sclerosis and emerging drug candidates for cancer and cardiopulmonary inflammation. Leveraging its leadership in chemokine-based drug discovery, ChemoCentryx focuses on new classes of orally active small molecules to selectively inhibit activity of the chemokine system, the "master regulator" of immune response. Based in San Carlos, California, ChemoCentryx is privately held. For more information on the company, visit www.chemocentryx.com.

Any statements in this press release about ChemoCentryx's expectations, beliefs, plans, objectives, assumptions or future events or performance are not historical facts and are forward-looking statements. These statements are often, but not always, made through the use of words or phrases such as "believe," "will," "expect," "anticipate," "estimate," "intend," "plan," and "would." Forward-looking statements are not guarantees of performance. They involve known and unknown risks, uncertainties and assumptions that may cause actual results, levels of activity, performance or achievements to differ materially from any results, levels of activity, performance or achievements expressed or implied by any forward-looking statement. Some of the risks, uncertainties and assumptions that could cause actual results to differ materially from estimates or projections contained in the forward-looking statements include but are not limited to (i) the timing, success and cost of preclinical research and clinical studies, (ii) the timing, acceptability and review periods for regulatory filings, (iii) the availability of corporate partners, (iv) uncertainties relating to patent protection and intellectual property rights of third parties, (v) the impact of competitive products and technological changes, (vi) the availability of capital and the cost of capital, (vii) other vagaries in the biotechnology industry and (viii) other risks. ChemoCentryx undertakes no obligation to update or revise any forward-looking statements.