XenoPort Submits Investigational New Drug Application for XP23829 as a Potential Treatment of RRMS

  XenoPort Submits Investigational New Drug Application for XP23829 as a
  Potential Treatment of RRMS

Business Wire

SANTA CLARA, Calif. -- May 24, 2012

XenoPort, Inc. (Nasdaq:XNPT) announced today that it has submitted an
Investigational New Drug (IND) application to the U.S. Food and Drug
Administration (FDA) to begin clinical studies of XP23829 as a potential
treatment for relapsing-remitting multiple sclerosis (RRMS). Following
clearance of the IND by the FDA, the first Phase 1 clinical trial to be
conducted in healthy subjects will commence. This study is intended to examine
the safety, tolerability and pharmacokinetics of XP23829, including
confirmation of its conversion to monomethyl fumarate (MMF), and the
performance of four novel formulations of XP23829 designed to have different
drug release mechanisms and/or time profiles.

Ronald W. Barrett, Ph.D., chief executive officer of XenoPort, stated, “We are
pleased to take this step in advancing the development of XP23829. In addition
to our filing the IND to initiate human clinical trials for the potential
treatment of RRMS, we also recently demonstrated that XP23829 and related
compounds were effective in an animal model of psoriasis. We are hopeful that
our first Phase 1 clinical trial will provide evidence of safety and
tolerability and also provide pharmacokinetic data that might support
once-a-day dosing of XP23829. Our long-term goal is to create a best-in-class
fumaric acid ester-based medicine for the potential treatment of RRMS and/or
psoriasis.”

About XP23829

XP23829 is a prodrug of MMF (also known as methyl hydrogen fumarate). In cell-
and animal-based models, MMF has been shown to exhibit immuno-modulatory
properties and inhibit damage from oxidative stress. In XenoPort’s preclinical
animal studies that compared molar equivalent doses of XP23829 to dimethyl
fumarate (DMF), another prodrug of MMF, XP23829 demonstrated a greater degree
of efficacy in animal models of both multiple sclerosis and psoriasis.
Toxicology studies conducted in two species showed that XP23829 caused less
stomach irritation compared to DMF.

XenoPort was awarded U.S. Patent 8,148,414 for “Prodrugs of Methyl Hydrogen
Fumarate, Pharmaceutical Compositions Thereof, and Methods of Use.” The patent
is directed to the XP23829 compound and analogs and formulations thereof. The
term of the patent runs until 2029, subject to potential patent term
extensions under the Hatch-Waxman Act.

About XenoPort

XenoPort is a biopharmaceutical company focused on developing and
commercializing a portfolio of internally discovered product candidates for
the potential treatment of neurological disorders. Horizant^® (gabapentin
enacarbil) Extended-Release Tablets is XenoPort's first FDA-approved product.
GlaxoSmithKline holds commercialization rights and certain development rights
for Horizant in the United States. Regnite^® (gabapentin enacarbil)
Extended-Release Tablets is approved for the treatment of moderate-to-severe
primary restless legs syndrome in Japan. Astellas Pharma Inc. holds all
development and commercialization rights for Regnite in Japan and five other
Asian countries. XenoPort holds all other world-wide rights and has
co-promotion and certain development rights to gabapentin enacarbil in the
United States. XenoPort’s pipeline of product candidates includes potential
treatments for patients with postherpetic neuralgia, spasticity and
Parkinson’s disease.

To learn more about XenoPort, please visit the company Website at
www.XenoPort.com.

Forward-Looking Statements

This press release contains “forward-looking” statements, including, without
limitation, all statements related to patent coverage and term for XP23829;
XenoPort’s future clinical trials and the timing thereof; the regulatory
process and outcome of regulatory actions by the FDA related to the IND for
XP23829 and the timing thereof; the potential for starting clinical
development of XP23829 and the timing thereof; XenoPort’s future XP23829
development plans; the potential suitability of XP23829 as a treatment for
RRMS and/or psoriasis; and the therapeutic and commercial potential of
XenoPort’s clinical product candidates. Any statements contained in this press
release that are not statements of historical fact may be deemed to be
forward-looking statements. Words such as “goal,” “hopeful,” “intended,”
“might,” “potential,” “will” and similar expressions are intended to identify
forward-looking statements. These forward-looking statements are based upon
XenoPort's current expectations. Forward-looking statements involve risks and
uncertainties. XenoPort's actual results and the timing of events could differ
materially from those anticipated in such forward-looking statements as a
result of these risks and uncertainties, which include, without limitation,
risks related to XenoPort’s ability to successfully conduct clinical trials in
the anticipated timeframes, or at all; the uncertainty of the FDA IND
clearance process and other regulatory requirements; XenoPort’s dependence on
its current and additional collaborative partners; and the uncertain
therapeutic and commercial value of XenoPort’s product candidates. These and
other risk factors are discussed under the heading "Risk Factors " in
XenoPort's Quarterly Report on Form 10-Q for the quarter ended March 31, 2012,
filed with the Securities and Exchange Commission on May 8, 2012. XenoPort
expressly disclaims any obligation or undertaking to release publicly any
updates or revisions to any forward-looking statements contained herein to
reflect any change in the company's expectations with regard thereto or any
change in events, conditions or circumstances on which any such statements are
based.

XENOPORT is a registered trademark of XenoPort, Inc.

Horizant is a registered trademark of GSK.

Regnite is a registered trademark of Astellas.

XNPT2C

Contact:

XenoPort, Inc.
Jackie Cossmon, 408-616-7220
ir@XenoPort.com