XenoPort Announces Initiation of a Phase 1 Clinical Trial of XP23829, a Novel Fumarate Analog for the Potential Treatment of Relapsing-Remitting Multiple Sclerosis and Psoriasis

XenoPort Announces Initiation of a Phase 1 Clinical Trial of XP23829, a Novel Fumarate Analog for the Potential Treatment of Relapsing-Remitting Multiple Sclerosis and Psoriasis

<0> XenoPort, Inc.Jackie Cossmon, 408-616-7220 </0>

XenoPort, Inc. (Nasdaq: XNPT) announced today that the first subjects have been dosed in a Phase 1, randomized, double-blind, two-period crossover, food effect comparison study of XP23829 in healthy adults. The trial is designed to assess the pharmacokinetics, safety and tolerability of a single dose of XP23829 administered in both fasted and fed conditions.

Approximately 60 subjects will be assigned to one of five cohorts with each cohort receiving one of four different formulations of XP23829 or placebo. Subjects will receive a single dose of XP23829 or placebo in both a fasted and fed state in randomized order. The trial will assess the blood levels of XP23829, its active metabolite, monomethyl fumarate (MMF), and other potential metabolites. The four XP23829 formulations will include one immediate-release formulation and three extended-release formulations that are designed for possible once-a-day dosing of XP23829.

Ronald W. Barrett, Ph.D., chief executive officer of XenoPort, said, “Dosing of the first human subject with XP23829 is an important milestone as we work to develop this potential best-in-class fumarate analog. One goal of this study is to verify that XP23829 is efficiently metabolized to produce MMF in the blood. We believe that the MMF pharmacokinetic profiles produced by the different XP23829 formulations administered with and without food will be instructive for the selection of one or more formulations to take forward into future trials.”

XP23829 is currently being studied in a Phase 1 clinical trial in healthy subjects and has potential as a treatment for relapsing-remitting multiple sclerosis (RRMS) and/or psoriasis. It is a fumaric acid ester compound that is a patented prodrug of MMF. Fumaric acid ester compounds have shown immuno-modulatory and neuroprotective effects in cell-based systems and preclinical models of disease. Dimethyl fumarate (DMF), also a fumaric acid ester compound and a prodrug of MMF, has been shown to be effective in clinical trials in patients with RRMS and psoriasis. In XenoPort’s preclinical animal studies that compared molar equivalent doses of XP23829 to DMF, 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 when compared to DMF.

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 approved in the United States for the treatment of moderate-to-severe primary restless legs syndrome (RLS) in adults and for the management of postherpetic neuralgia in adults. GlaxoSmithKline holds commercialization rights and certain development rights for in the United States. Regnite (gabapentin enacarbil) Extended-Release Tablets is approved for the treatment of RLS in Japan. Astellas Pharma Inc. holds all development and commercialization rights for 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 spasticity, Parkinson’s disease and RRMS.

To learn more about XenoPort, please visit the web site at .

This press release contains “forward-looking” statements, including, without limitation, all statements related to the clinical development of XP23829 and the timing and results thereof; 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 “believe,” “possible,” “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 the uncertain results and timing of clinical trials and other studies; XenoPort’s ability to successfully conduct clinical trials in the anticipated timeframes, or at all; XenoPort’s dependence on its current and additional collaborative partners; the availability of resources to develop XenoPort’s product candidates; 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.

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Source code: XNPT2C