ChemoCentryx Reports Promising Clinical Activity for Traficet-EN(R) From Phase 2 Trial for the Treatment of Crohn's Disease.

Phase 2 Results Used in Design of Ongoing 400+ Patient PROTECT-1 Clinical Trial

BERLIN -- ChemoCentryx, Inc., a clinical-stage, biopharmaceutical company developing orally-administered therapeutics that target the chemokine and chemoattractant systems, today announced positive data from the company's Phase 2 clinical trial of Traficet-EN[R] (CCX282-B) for the treatment of Crohn's disease at the 14th United European Gastroenterology Week (UEGW 2006) meeting in Berlin, Germany. Traficet-EN[R] is a first-in-class, orally active, anti-inflammatory agent that targets the chemokine receptor known as CCR9.

The four-week Phase 2 clinical trial enrolled 74 patients with moderate-to-severe Crohn's disease to primarily assess Traficet-EN's safety and tolerability. Patients were randomized on a 2:1 basis to receive 250 mg of Traficet-EN once daily for 28 days or placebo. Traficet-EN was very well tolerated: incidence of adverse events was approximately similar to those observed in the placebo group. Clear signs of clinical activity, measured by a drop in blood levels of C-reactive protein (CRP) were observed in the patients receiving Traficet-EN compared to placebo. Researchers observed a mean CRP decrease of 4.4 3.7 mg/L after 28 days on Traficet-EN, while CRP levels increased by 6.7 4.2 mg/L in the placebo group, relative to baseline, across the entire study. In addition, the Crohn's Disease Activity Index (CDAI) also decreased in patients on study drug. In a defined subgroup of patients who were in active flare at the time of study entry (as determined by baseline CDAI and CRP that were greater than 250 and 7.5 mg/L, respectively), 56 percent of patients receiving Traficet-EN experienced a 70-point reduction in CDAI compared to 29 percent of those who received placebo. Further, a 100-point drop in CDAI scores occurred in 40 percent of patients dosed with Traficet-EN, compared to 21 percent on placebo. In addition, the rate of reduction in CDAI was significantly more rapid in the CCX282-B group.

"In addition to being very pleased with the safety profile observed to date, we are very encouraged by the percentage of patients who received clinical benefit from Traficet-EN as observed by a significant drop in their CDAI scores and CRP levels," said Pirow Bekker, M.D., Ph.D., ChemoCentryx's Vice President, Medical and Clinical Affairs. "Based on the positive data obtained in this trial of Traficet-EN, we have designed and initiated a large multi-national trial of more than 400 Crohn's patients with moderate-to-severe disease, which is now ongoing. This new trial, called PROTECT-1 is designed to demonstrate whether Traficet-EN induces a response or remission in subjects with moderate-to-severe Crohn's disease as measured by improvements in CDAI scores. In addition, an extension to the study will also assess whether Traficet-EN may be useful for the maintenance of disease response or remission."

The Prospective Randomized Oral Therapy Evaluation in Crohn's disease Trial (PROTECT-1) will enroll approximately 420 patients. Patients will receive Traficet-EN or placebo either at the same dose used in the Phase 2 trial or at twice the dose over a 12-week period. The primary objective of the trial will be to determine the effect on Crohn's disease severity as measured by changes in the CDAI score. Secondary efficacy objectives include evaluation of the effect of Traficet-EN on microscopic features of the small and large bowel surface tissue, endoscopic appearance of the bowel surface tissue, health-related quality of life based on a questionnaire, and serum concentrations of CRP.

The Phase 2 data were presented today at the UEGW meeting in an oral presentation entitled "CCX282-B, an Orally Active Inhibitor of Chemokine Receptor CCR9, in a Randomized, Double-blind, Placebo-controlled Phase 2 Study in Moderate to Severe Crohn's Disease" (Abstract #OP-G-93) delivered by Satish Keshav, M.D., Ph.D., who is the Director of the Gastroenterology Centre and IBD Clinic in The Department of Medicine, Royal Free & University College Medical School London, and a clinical investigator on the ChemoCentryx study.

"Crohn's disease is a serious and debilitating condition affecting hundreds of thousands of patients worldwide. In spite of a number of medications - including 5-ASAs, immunosuppressants, steroids and TNF alpha inhibitors - used in the treatment of Crohn's disease, there is still a great unmet need for safe, effective and well-tolerated oral medications to induce and maintain remission," said Dr. Keshav. "Traficet-EN appears to be one of the first of new chemical classes to be developed in some time for Crohn's that shows preliminary efficacy in early trials. In particular, Traficet-EN's oral dosing, its excellent safety profile and strong signs of clinical activity, represent an important innovation in the treatment of this chronic, disabling disease."

About Traficet-EN

Traficet-EN a small molecule, orally-available drug, is intended to control the inappropriate immune system response underlying inflammatory bowel disease (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 principle forms of IBD. ChemoCentryx has completed four Phase I trials and one 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 of greater than 400 patients with moderate-to-severe Crohn's disease.

About Crohn's Disease

Crohn's disease is a chronic inflammatory condition of the gastrointestinal tract. It is estimated that the disease affects over 500,000 patients in Europe and North America. Patients suffer periods of flare-ups or periods characterized by intense symptoms, interspersed with periods of remission where symptoms decrease or disappear. As Crohn's disease is a chronic condition, 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.

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 generated, internally, 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 (PROTECT-1) of greater than 400 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.