Abstract 2547 Mechanistic Insights into HPK: A Targeted Protein Delivery System for HER3-Driven Cancer Therapy

Elevated expression of epidermal growth factor receptor-3 (HER3) has been observed in many human cancer types and indicates lower survival rates for patients with tumors.Activation of HER3 signaling has been shown to promote cancer metastasis and has been identified as a major cause of treatment resistance in cancer therapy, making HER3 an attractive target for therapeutic intervention.HPK (HER Penton base with K-tail) is a pentameric HER3-homing protein particle designed to mediate delivery of therapeutics to tumors with high surface densities of HER3 and has been shown to only enter tumor cells, leaving healthy cells alone.Our research employs molecular dynamics (MD) simulations to investigate the structural and biochemical properties of HPK bioparticle under physiological conditions, both in isolation and in complex with different types of cargo.We have previously helped develop the second-generation of this bioparticle called HPK2.0.In this study we have conducted MD simulations on HPK2.0 in different pH environments matching early to late endosomes to probe its unique dissociative behavior in these acidic conditions.We found that HPK2.0 breaks up into individual monomers at pH 5 but not at pH 7, highlighting its pH-dependent structural dynamics.This dissociation is needed for the release of any therapeutic cargo that may be loaded onto the bioparticle.Additionally, we have built structural models of HPK-HER3 receptor complexes to study how HPK binding influences HER3 activation and signaling.These studies will elucidate the molecular mechanisms underlying HPK's interactions with HER3 and its therapeutic cargo, with the ultimate goal of optimizing HPK2.0 structure as a precision delivery vehicle for cancer therapeutics.