Crystal Structures, Dissolution and Pharmacokinetic Study on a Novel Phosphodiesterase-4 Inhibitor Chlorbipram Cocrystals

Abstract Cocrystallization of chlorbipram (ChBP), a novel phosphodiesterase-4 (PDE) inhibitor with water insoluble property developed in our lab, was performed to improve the physicochemical properties and bioavailability in the present study. Three new cocrystals with fumaric aicd (FA), gentisic acid (GA) and salicylic acid (SA) as coformers were synthesized and fully characterized by using the combination of multi-techniques. The cocrystals are phase stable even under high humidity conditions. In vitro study indicates that the solubility of ChBP-GA and ChBP-SA cocrystals increase to 3724.4 ± 58.7, 2897.4 ± 81.9 μg/mL in comparison with ChBP (2561.3 ± 150.4 μg/mL), the intrinsic dissolution rates (IDRs) of ChBP-GA and ChBP-SA cocrystals (721.3 ± 8.0, 614.4 ± 13.2 μg/min/cm2) are both higher than ChBP (537.9 ± 12.0 μg/min/cm2). The blood concentration peak values of ChBP-GA and ChBP-SA cocrystals (165.8 ± 50.9, 105.3 ± 35.6 ng/mL) are both higher than ChBP (51.3 ± 15.1 ng/mL) in in vivo evaluation. It presents the same order in in vitro/vivo study: ChBP-GA > ChBP-SA > ChBP > ChBP-FA. ChBP-FA cocrystal presents a longer elimination half life (t1/2 = 10.0 ± 2.6 h), which makes it a potential candidate for prolonged controlled release formulation. ChBP-GA and ChBP-SA cocrystals both present enhanced solubility and bioavailability in comparison with ChBP, making them a better candidate for the solid dosage formulation development.