Abstract
Buntanetap is an orally bioavailable small molecule that has been shown to improve cognitive function in patients with Alzheimer's and Parkinson's diseases and holds promise for use in other neurodegenerative conditions. Until now, a crystalline anhydrate (Form A) has been used in preclinical and clinical studies. However, a novel dihydrate crystal (Form B) was recently discovered, offering improved solid-state stability without compromising its absorption, systemic exposure, and metabolism. We sought to evaluate the pharmacokinetic (PK) profile of Form B and compare it to the well-characterized PK profile of Form A in a series of studies conducted in mice, dogs, and humans. Our data revealed that although the two forms are distinct and do not interconvert, they exhibit comparable PK profiles both within and across species. Consistent with previous reports, Form A and Form B alike reached fast peak plasma concentrations (<2 h), demonstrated efficient partitioning into brain tissue, and were fully cleared by 12 h post-dose. Furthermore, metabolic profiling showed that both forms produced identical PK profiles for the primary metabolites, N1- and N8-norbuntanetap, confirming that Form B retains the established metabolic characteristics of Form A. These findings support the continued development of Form B for future clinical use, as it combines enhanced solid-state stability with a preserved PK profile essential for buntanetap's therapeutic efficacy.