XenoPort, Inc. (Nasdaq: XNPT) announced today favorable preliminary results from a Phase 1 clinical trial in healthy adults designed to assess the pharmacokinetics (PK), safety and tolerability of single doses of four different oral formulations of XP23829, a novel fumaric acid ester compound that is a prodrug of monomethyl fumarate (MMF). XP23829 is being developed for the potential treatment of relapsing-remitting multiple sclerosis (RRMS) and/or psoriasis. The trial demonstrated that administration of XP23829 resulted in the expected levels of MMF in the blood. As anticipated, the four formulations produced different PK profiles of MMF, including one formulation that could potentially be dosed two or three times a day and at least one formulation that may be suitable for once-a-day dosing. XP23829 was generally well-tolerated in the trial.
Ronald W. Barrett, Ph.D., chief executive officer of XenoPort, said, "Given the broad potential therapeutic utility of XP23829, we are delighted that the results of this first Phase 1 trial achieved our goals by confirming the expected human metabolism of XP23829 and identifying formulations that we believe could be capable of achieving MMF exposures that are similar to MMF exposures observed in other fumaric acid ester therapies that have demonstrated effectiveness in psoriasis and RRMS. We are particularly pleased that the results suggest that the PK profile of at least one of our formulations supports further evaluation as a once-a-day treatment. We anticipate initiating further studies early next year, including a Phase 1, dose-escalation, multiple-dose study in healthy subjects, with the ultimate goal of developing a potential best-in-class fumaric acid ester-based medicine."
In the Phase 1 trial, 60 subjects were assigned to five cohorts of 12, and each cohort received one of four different formulations of XP23829 or placebo. Subjects received a single dose of XP23829 or placebo in both a fasted and fed state in a randomized order with a two-week period between dosing. All formulations of XP23829 were administered at a dose that was equivalent to 107 mg of MMF. Formulation 1 was a delayed-release formulation that was designed to suppress the release of XP23829 while in the stomach and then immediately release the drug upon entering the small intestine. Formulations 2, 3 and 4 were designed to delay and then slowly release XP23829.
All formulations of XP23829 produced MMF in the blood, while levels of intact XP23829 and the potential desmethyl-metabolite of XP23829 were below the limits of quantitation. The clearance of the promoiety, a pharmacologically inactive molecule that is also created in the enzymatic conversion of XP23829 to MMF, was rapid, with a half-life of about three hours.
As anticipated, when dosed in a fasted state, Formulation 1 produced a sharp peak in MMF blood levels and a PK profile that supports further evaluation for two- or three-times-a-day dosing. The maximum MMF concentrations after dosing Formulation 1 were lower and more variable when dosed with food.
Formulation 2 produced a total MMF exposure that was similar to that of Formulation 1, but with a lower maximum MMF concentration and a longer duration of exposure. The presence of food had minimal effect on the total exposure and PK profile of MMF. Given the duration of MMF exposure, the PK profile for Formulation 2 supports further evaluation as a once-a-day treatment. While Formulations 3 and 4 also produced sustained exposures of MMF, the total MMF exposures in blood were generally lower than Formulations 1 and 2.
XP23829 was generally well tolerated during the trial. All 12 subjects in each cohort completed both dosing periods. All adverse events were rated as mild. The only adverse events reported in more than one subject and more frequently for XP23829 than for placebo were flushing and "feeling hot." Of the 12 subjects in each cohort, the number of subjects reporting these adverse events was as follows: