PROTECT-1 Phase II/III Induction-Stage Results for ChemoCentryx's Traficet-EN(TM)...

PROTECT-1 Phase II/III Induction-Stage Results for ChemoCentryx's
Traficet-EN(TM) Presented in Oral Session at DDW 2009 Conference

Oral CCR9 Antagonist Demonstrates Clinical Efficacy with Favorable
Tolerability Profile

MOUNTAIN VIEW, Calif., June 1 /PRNewswire/ -- ChemoCentryx, Inc., announced
that Phase II/III clinical data from the company's PROTECT-1 (the Prospective
Randomized Oral Therapy Evaluation in Crohn's disease Trial) of
Traficet-EN(TM) (CCX282-B) in patients with moderate-to-severe Crohn's disease
demonstrated evidence of clinical efficacy in the reduction of disease
severity, as defined by a decrease from baseline in the Crohn's Disease
Activity Index (CDAI) score of at least 70 points over the course of 12 weeks;
the more stringent criterion of at least a 100 point decrease in the CDAI
score was also met by week 12. In addition, Traficet-EN treatment resulted in
colonoscopic evidence of improvement. These data, reported from the Induction
Stage of the ongoing PROTECT-1 trial, were presented at Digestive Disease Week
(DDW) 2009 in Chicago, IL, by Satish Keshav, M.D., Ph.D., Department of
Gastroenterology, John Radcliffe Hospital, Oxford University, in an oral
session today.

The study, "PROTECT-1 Study Demonstrated Efficacy of the Intestine-Specific
Chemokine Receptor Antagonist CCX282-B (Traficet-EN) in Treatment of Patients
with Moderate to Severe Crohn's Disease," showed that the 500 mg once-daily
dose (QD) of Traficet-EN in patients with small bowel and/or colonic Crohn's
disease was consistently superior to placebo across multiple efficacy
endpoints. At week 12, the CDAI greater than or equal to 70-point response
was 61 percent in the 500 mg QD group versus 47 percent for placebo (p=0.039).
Similarly, the CDAI greater than or equal to 100-point response was 55
percent in this group versus 40 percent for placebo (p=0.029). In his oral
presentation, Dr. Keshav further noted that colonoscopic evidence of
improvement based on the Crohn's Disease Endoscopic Index of Severity (CDEIS)
was observed in the 500 mg QD group compared to placebo (CDEIS decrease of
-8.4 vs. -1.1 for placebo, p=0.049). C-reactive protein (CRP) results
confirmed the effect of 500 mg QD Traficet-EN. Traficet-EN may offer a new
orally available treatment option with a favorable side effect profile to
patients with this chronic gastrointestinal disease.

"Targeting the CCR9 chemokine receptor represents a new and highly specific
approach to treating patients with Crohn's disease and potentially ulcerative
colitis," said Pirow Bekker, M.D., Ph.D., Senior Vice President, Medical and
Clinical Affairs of ChemoCentryx. "No cure exists for inflammatory bowel
diseases and many patients do not respond to or cannot tolerate current
treatment options, including the newer biologics such as anti-Tumor Necrosis
Factor (TNF) agents, which need to be injected or infused. There was no
evidence of an increased risk of infection with Traficet-EN in PROTECT-1.
This safety and efficacy profile may translate into a meaningful treatment
option for patients."

"These data highlight a year of unparalleled clinical development progress by
the ChemoCentryx team. This is true not only for our CCR9 program, but
throughout our entire pipeline," said Thomas J. Schall, Ph.D., President and
Chief Executive Officer of ChemoCentryx. "Traficet-EN results announced today
underscore our leadership position in CCR9-based therapeutics for the
treatment of inflammatory bowel diseases."

The randomized, placebo-controlled, double-blind PROTECT-1 clinical trial of
more than 430 patients is comprised of three discrete phases which allows for
evaluation of efficacy and safety of Traficet-EN in inducing a clinical
response or remission, as well as maintaining response/remission in Crohn's
disease over a combined total of 12 months. The Induction Phase of the study
is followed by a four-week, open label 'Active Period', during which all
subjects receive Traficet-EN. Patients who achieve a pre-specified reduction
in disease severity are re-randomized to active drug or placebo for an
additional 36-week 'Maintenance Period', thereby permitting an evaluation of
the drug's ability to maintain a treatment response.

Traficet-EN is an orally-active inhibitor of the chemokine receptor known as
'CCR9', which is selectively expressed by inflammatory T cells to migrate to
the digestive tract in a process that ultimately results in the persistent
inflammation underlying the disease. Targeting the CCR9 chemokine receptor
represents a novel approach for the treatment of Crohn's disease and other
inflammatory disorders of the gastrointestinal system.

About Traficet-EN(TM) (CCX282-B)
Traficet-EN is a small molecule, orally-available drug that is administered in
capsule form and which is believed to control the inappropriate immune system
response underlying inflammatory bowel disease (IBD) by blocking 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. In preclinical studies, the compound worked both
therapeutically and prophylactically in models of Crohn's disease and
ulcerative colitis. In addition to the ongoing PROTECT-1 clinical trial in
Crohn's disease, Traficet-EN is being evaluated for patients with celiac
disease, a sensitivity to gluten and gluten derivatives in which digestive
tract T cells are thought to play an important role. ChemoCentryx has
completed five Phase I clinical trials and one four-week Phase II Crohn's
disease trial of Traficet-EN, demonstrating that the product candidate is
well-tolerated and appropriate for once-daily oral dosing. Traficet-EN may
offer advantages over existing therapeutic approaches for Crohn's disease by
potentially offering reduced side effects and convenient oral dosing to
patients. Traficet-EN is being developed under a strategic alliance with
GlaxoSmithKline's Center of Excellence for External Drug Discovery (CEEDD).

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 characterized
by intense symptoms, interspersed with periods of relative 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 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 network of secreted chemokine molecules, or ligands, and cell surface
receptors that regulates inflammation. Based on its proprietary drug discovery
and drug development platform, ChemoCentryx has internally generated multiple
clinical and preclinical-stage programs, each targeting distinct chemokine and
chemoattractant receptors with different small molecule compounds.
ChemoCentryx's lead compound, Traficet-EN, a specific CCR9 antagonist, is in a
Phase II/III multi-national clinical trial, called PROTECT-1, in patients with
moderate-to-severe Crohn's disease. CCX025, also a CCR9 antagonist, is in a
Phase I clinical trial. Additional clinical programs include the development
of CCX140, which targets the CCR2 receptor, currently in a Phase I clinical
trial and intended for subsequent development to treat diseases such as Type 2
diabetes, multiple sclerosis and vascular restenosis, and CCX354, a CCR1
antagonist in a Phase I clinical trial, being developed for inflammatory
diseases such as rheumatoid arthritis. ChemoCentryx also has several programs
in preclinical development. 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 may,
believe, will, expect, anticipate, estimate, intend, predict, seek, potential,
continue, plan, should, could and would or the negative of these terms or
other comparable terminology. 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
initiation, timing, progress and results of ChemoCentryx's preclinical studies
and clinical trials, (ii) ChemoCentryx's ability to advance product candidates
into clinical trials, (iii) GSK's exercise of its license options, (iv) the
commercialization of ChemoCentryx's product candidates, (v) the implementation
of ChemoCentryx's business model, strategic plans for its business, product
candidates and technology, (vi) ChemoCentryx's ability to maintain and
establish collaborations or obtain additional government grant funding, (vii)
ChemoCentryx's estimates of its expenses, future revenues, capital
requirements and its needs for additional financing, (viii) the timing or
likelihood of regulatory filings and approvals, (ix) the availability of
corporate partners, (x) the scope of protection ChemoCentryx is able to
establish and maintain for intellectual property rights covering its product
candidates and technology, (xi) the impact of competitive products and
technological changes, (xii) the availability of capital and the cost of
capital, (xiii) ChemoCentryx's financial performance, (xiv) developments
relating to ChemoCentryx's competitors and other vagaries in the biotechnology
industry and (xv) other risks.

You are cautioned not to place undue reliance on these forward-looking
statements, which speak only as of the date hereof. All forward-looking
statements are qualified in their entirety by this cautionary statement and
ChemoCentryx undertakes no obligation to revise or update this press release
to reflect events or circumstances after the date hereof. This caution is made
under the safe harbor provisions of Section 21E of the Private Securities
Litigation Reform Act of 1995.

SOURCE ChemoCentryx, Inc.

Susan M. Kanaya, Senior Vice President, Finance and Chief Financial Officer,
or Markus J. Cappel, Ph.D., Chief Business Officer, both of ChemoCentryx,
+1-650-210-2900, investor@chemocentryx.com; or media, Karen L. Bergman,
+1-650-575-1509 (mobile), or Susan Pietropaolo, +1-201-923-2049 (mobile), both
of BCC Partners for ChemoCentryx