An Improved Brain-Penetrating Nanoformulation of the VIPR2 Antagonist Peptide KS-133 for Treating Cognitive Impairment in Schizophrenia

In 2024, we reported a brain-penetrant formulation of the vasoactive intestinal peptide receptor 2 (VIPR2) antagonist peptide KS-133 that mitigated cognitive dysfunction in the VIPR2 hyperactivation mouse model of schizophrenia. In this formulation, KS-133 was encapsulated in the hydrophobic core of nanoparticles (NPs) coated with 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine–KS-487 (DPPE–KS-487), a conjugate of the cyclic peptide KS-487 and DPPE produced by a click reaction that binds low-density lipoprotein-related protein 1, enabling blood–brain barrier penetration upon subcutaneous 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. In the current study, we coated KS-133-containing NPs with 1,2-distearoyl-sn-glycero-3-phosphoethanolamine–KS-487 (DSPE–KS-487), a novel conjugate of KS-487 with DSPE produced through a non-click method, thus eliminating positional isomers, and also established a simplified manufacturing process allowing a unidirectional transition from ultrasonication at high to low temperatures. This formulation remained physically and chemically stable for at least 12 months under refrigeration, with no changes in particle size, zeta potential, KS-133 content, or KS-487 presentation level. The formulation also exhibited brain penetration and therapeutic efficacy against VIPR2 agonist-induced novel object recognition impairment in mice comparable to those of DPPE–KS-487 NPs. Furthermore, no systemic side effects of hematologic, brain, heart, liver, and lung toxicity were detected following daily injections to mice for two weeks at five times the effective dose. This new KS-133 formulation incorporating DSPE–KS-487 as a brain-penetrant shuttle is a promising drug candidate for the treatment of cognitive dysfunction in schizophrenia.