ChemoCentryx Presents Clinical and Preclinical Data on Traficet-EN(R) in Inflammatory Bowel Disease (IBD).

Clinical Analysis Shows that Traficet-EN Reduces Inflammation Associated with IBD 

MIAMI -- ChemoCentryx, Inc. is presenting clinical and preclinical data from studies of the company's drug candidate Traficet-EN[R] (CCX282-B) a first-in-class, orally active, anti-inflammatory agent that targets the chemokine receptor known as CCR9, at the 2006 Crohn's and Colitis Foundation of America's (CCFA) National Research and Clinical Conference/Fifth Annual Advances in the Inflammatory Bowel Diseases meeting being held December 1-3, 2006 in Miami, FL. New data from a Phase 2 clinical trial of patients with moderate-to-severe Crohn's disease are being presented analyzing the effect of Traficet-EN on lowering pro-inflammatory cytokine and chemokine concentrations in the intestine. These findings complement earlier data showing improved clinical endpoints in Crohn's disease from the Phase 2 clinical trial.

Traficet-EN elicited a decrease in the levels of pro-inflammatory cytokines and chemokines, including TNF-alpha, interleukin 12, interferon gamma and the chemokine ligand RANTES. In contrast, no decreases in such parameters were seen in patients on placebo. Biopsies were taken from the colon of patients upon enrollment in the study and again upon completion of the 28-day treatment regimen. These results are consistent with previously reported data from the Phase 2 clinical trial showing that blood levels of C-reactive protein (CRP) dropped and Crohn's Disease Activity Index (CDAI) scores decreased among patients who received Traficet-EN as compared to those on placebo. The randomized, placebo-controlled four-week Phase 2 trial was designed to assess Traficet-EN's safety and tolerability among Crohn's patients. The clinical analysis of inflammatory response data will be presented by Pirow Bekker, M.D., Ph.D., ChemoCentryx's Vice President, Medical and Clinical Affairs, as part of Session VIII: Original basic and clinical research abstract presentations on Sunday, December 3, 2006 at 11:10 a.m. Eastern Standard Time in a presentation entitled "Traficet-EN (CCX282), an Orally Active Inhibitor of Chemokine Receptor CCR9 for Treatment of Crohn's Disease."

"In designing our four-week Phase 2 trial of this first-in-class compound, we sought to initially evaluate safety and tolerability when administering Traficet-EN to subjects with Crohn's disease. We are encouraged by the consistent evidence achieved in our early Phase 2 trial showing that Traficet-EN appears to reduce the inflammatory response in the digestive tract and to alleviate the symptoms of Crohn's disease among patients," said Dr. Bekker. "We are currently conducting a larger-scale clinical trial, called PROTECT-1, to study Traficet-EN's efficacy in inducing and potentially maintaining clinical responses among Crohn's patients. In addition, based on preclinical studies, we believe Traficet-EN may have applications beyond Crohn's disease to address gastrointestinal conditions where inflammation plays a key role."

Preclinical data from studies in two models of IBD showing that Traficet-EN alleviated the mucosal inflammation associated with IBD are being presented by Thomas J. Schall, Ph.D., ChemoCentryx's President and Chief Executive Officer. In a TNF-DARE mouse model of Crohn's disease, treatment with Traficet-EN resulted in significant improvement of disease, with 70 percent of the treated group scoring normal or mild disease and with no evidence of severe disease. In contrast, 60 percent of mice in the control group developed severe disease. A second set of preclinical studies in an MDR1a mouse model of ulcerative colitis showed that Traficet-EN was highly effective in alleviating symptoms. These data will be included in a presentation entitled "Pharmacological Inhibition of Gut-Homing CCR9 T-cells Alters Disease Severity in Murine Models of Inflammatory Bowel Disease" as part of Session VI B: Original basic and clinical research abstract presentations on Saturday, December 2, 2006 at 3:40 p.m. Eastern Standard Time.

About Traficet-EN

Traficet-EN a small molecule, orally-available drug, is intended to control the inappropriate immune system response underlying IBD by blocking the activity of the CCR9 chemokine receptor. In adults, CCR9 is a highly specific receptor expressed by T cells that migrate selectively to the digestive tract. The trafficking of T cells to the small and large intestine causes persistent inflammation that may result in Crohn's disease or ulcerative colitis - the two principal forms of IBD. ChemoCentryx has completed four Phase I trials and one four-week Phase 2 trial of Traficet-EN demonstrating that the product candidate is well-tolerated and appropriate for once- or twice-daily oral dosing. In preclinical studies, the compound worked both therapeutically and prophylactically in Crohn's disease. Currently, Traficet-EN is being tested in the PROTECT-1 trial, a multinational study in patients with moderate-to-severe Crohn's disease.

About Inflammatory Bowel Disease

Inflammatory bowel disease refers to two diseases - Crohn's disease and ulcerative colitis - characterized by chronic inflammation of the small and large intestine. Patients suffer periods of flare-ups or periods characterized by intense symptoms, interspersed with periods of remission where symptoms decrease or disappear as inflammatory cells attack the intestinal walls. Patients continue on a given therapeutic regimen from the time of diagnosis over the course of a lifetime, layering additional therapies as flare-ups recur or persist in an effort to reduce symptoms. When medications can no longer control symptoms, patients have few or no options beyond surgery. Crohn's disease is estimated to affect more than 500,000 patients in Europe and North America. Ulcerative colitis is estimated to affect 670,000 people in the United States, and an additional 330,000 people worldwide.

About ChemoCentryx

ChemoCentryx, Inc. is a clinical-stage biopharmaceutical company focused on discovering, developing and commercializing orally-administered therapeutics that target the chemokine and chemoattractant systems in order to treat autoimmune diseases, inflammatory disorders and cancer. The chemokine system is a complex network of chemokine molecules, or ligands, and receptors that regulates inflammation. Based on their proprietary drug discovery and drug development platform, ChemoCentryx has internally generated several clinical and preclinical stage programs, each targeting distinct chemokine and chemoattractant receptors with different small molecule compounds. ChemoCentryx's lead compound, Traficet-EN[R], a specific CCR9 antagonist, is currently in a multinational clinical trial, called PROTECT-1, in patients with moderate-to-severe Crohn's disease. In August 2006, ChemoCentryx and GlaxoSmithKline entered into a worldwide strategic alliance to discover, develop and commercialize up to six novel medicines targeting four chemokine and chemoattractant receptors for a variety of inflammatory disorders. ChemoCentryx is privately held. For more information, please refer to 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.