Abstracts

Rationale: Huperzine A is a potent, naturally occurring acetylcholinesterase inhibitor used in Chinese medicine for the treatment of numerous neurological disorders, including Alzheimer’s disease and neuropathic pain. Utilizing a novel, proprietary synthetic route for scale-up production of highly pure Huperzine A, Biscayne Neurotherapeutics, Inc. is developing synthetic Huperzine A (also known as BIS-001) as a treatment in adults with drug-resistant epilepsy. Previous studies have shown that Huperzine A induces cholinergic side effects as a result of high maximum concentration (Cmax) in plasma.  Furthermore, the pharmacokinetics of the currently available immediate release form requires 4-6 times daily dosing to maintain sufficient plasma concentrations for seizure protection.  The high frequency of dosing and undesirable side effect profile would result in very low patient compliance, causing a persistence of seizure activity.  An extended release formulation of BIS-001 would allow for less frequent daily dosing (twice daily) and result in more constant plasma concentrations, thus, decreasing the cholinergic side effect profile prompted by the high Cmax.  The current study sought to produce prototypes of an extended release BIS-001 (BIS-001 ER), and evaluate their pharmacokinetic characteristics by in vitro dissolution and in vivo testing. Methods: In Vitro Dissolution: Several prototypes of BIS-001 ER were developed, and the BIS-001 release characteristics were assessed by commonly used in vitro dissolution methods, which quantify drug released over time, under mechanically mixed, physiological conditions.  Test samples were taken at 30, 60, 120, 180, 240, 300, 360, 420, 480, 600, and 720 min.  Total release (%) was measured using HPLC analysis.Pharmacokinetics:  The pharmacokinetics of the BIS-001 ER prototypes were characterized in dogs (n=2-3) following oral administration of 0.049 mg/kg.  Plasma samples were collected at 0.5, 1, 2, 3, 4, 6, 8, 10, 12, and 24 hrs, and BIS-001 concentrations were quantified by LC-MS/MS analysis. Results: Several BIS-001 ER prototypes were successfully produced.  In the in vitro dissolution assay, the lead formulation accomplished a desirable dissolution rate which resulted in an in vivo half-life (t1/2)of ~8hrs.  Furthermore, BIS-001ER’s release behavior in vitro was confirmed to attain the preferred release profile in an in vivo dog pharmacokinetic study. The concentration-time profile of a single 0.049 mg/kg dose (p.o.) of the lead BIS-001 ER formulation in dogs was best fit by a  first order absorption, two-compartment PK model, with a t1/2 = 8.32 hrs, time of maximal concentration (Tmax) = 4 hrs, and Cmax = 6 ng/mL  Conclusions: A new BIS-001 extended release formulation was demonstrated, in both in vitro and in vivo (dog) studies, to slow drug release, significantly reduce serum peak concentrations, and to eliminate previously observed cholinergic side effects; therefore, displaying a profile necessary for human use in seizure prevention. Funding: Supported by Biscayne Neurotherapeutics, Inc.