Physicians who treat multiple sclerosis have been looking forward to getting access to Biogen Idec Inc.'s BG-12 based on its efficacy, safety and oral dosing. Now XenoPort Inc. is seeking to build a better version with XP23829, an asymmetrical diester prodrug of monomethyl fumarate.

The compound cleared its first clinical hurdle early this month when XenoPort reported Phase I safety and pharmacokinetic data that suggest potential for once-daily dosing and fewer side effects than BG-12.