307. A new nanoformulation of a brain-penetrating VIPR2 antagonist peptide for the treatment of schizophrenia

Abstract

Abstract Background Both preclinical and clinical studies have demonstrated a strong link between high expression/overactivation of vasoactive intestinal peptide receptor 2 (VIPR2) and schizophrenia. We recently reported on a brain-penetrant formulation of the VIPR2 antagonist peptide KS-133, which was found to restore cognitive function in a mouse model of schizophrenia with early postnatal VIPR2 hyperactivation (Sakamoto et al., JACS Au 2024). In this formulation, KS-133 was encapsulated in the hydrophobic core of nanoparticles (NPs) coated with DPPE-KS-487, a conjugate of the cyclic peptide KS-487 and dipalmitoylphosphoethanolamine (DPPE) produced by a click reaction that binds low-density lipoprotein-related protein 1, thereby enabling blood-brain barrier (BBB) penetration upon systemic injection. However, the click reaction generated multiple positional isomers and manufacturing required repetitive cycles of ultrasonication at high and low temperatures, posing challenges for industrial scalability. The pharmacological and safety profiles of KS-133 also remain unclear. Aims & Objectives This study aimed to develop a new formulation of KS-133-containing NPs coated with distearoylphosphoethanolamine (DSPE) using a non-click method, and to evaluate the therapeutic potential and safety profile of KS-133/DSPE-KS-487 NPs in mice. Method Adult male ICR or C57BL/6J mice were used. All animal procedures were approved by the Animal Care and Use Committees of The University of Osaka, Hiroshima University, and KAC Bioscience. For the pharmacokinetic study, blood, brain, and pancreas were collected at 1, 2, 4, and 6 h after subcutaneous administration. For the behavioral studies, depressive-like behaviors and cognitive impairments were analyzed using the forced swim test and novel object recognition test, respectively. For the safety testing, whole blood samples were collected for hematological and biochemical analyses. Results Using a non-click method, we coated KS-133-containing NPs with DSPE-KS-487, thereby avoiding positional isomers, and established a streamlined manufacturing process that allows the ultrasonication step to proceed unidirectionally from high to low temperatures. This new formulation remained physically and chemically stable for at least 12 months under refrigeration, with no aggregation or changes observed in particle size, zeta potential, KS-133 content, or KS-487 presentation level. KS-133/DSPE-KS-487 NPs exhibited brain penetration and therapeutic efficacy in chronic ketamine-induced models of locomotor sensitization, depressive-like behaviors, and cognitive impairment in mice. We confirmed that KS-133 acts selectively on VIPR2 among the 48 receptors targeted by current antipsychotic medications and/or related to the pathophysiology of schizophrenia. Furthermore, no systemic side effects or signs of hematological, brain, heart, liver, or lung toxicity were detected following daily injections in mice for two weeks at five times the effective dose. Discussion & Conclusions We demonstrated that KS-133/DSPE-KS-487 NPs have equivalent pharmacokinetic properties and therapeutic efficacy to those of KS-133/DPPE-KS-487 NPs fabricated using a more complex, multistep procedure. This new formulation also exhibited excellent stability, an acceptable therapeutic window, and minimal side effects even at doses at least five times higher than the therapeutic dose. As the global healthcare burden of schizophrenia continues to rise, this KS-133/DSPE-KS-487 NP formulation could provide an effective treatment for negative symptoms and cognitive dysfunction that are currently difficult to treat.