Abstract 10487: In vivo Efficacy of HS135, a Novel Activin and GDF Trap for the Treatment of Pulmonary Hypertension (PH) and Metabolic Syndrome (MetS)

Abstract

Introduction: PH is a disorder characterized by remodeling of the pulmonary vasculature which causes increased pulmonary vascular resistance and ultimately right ventricular (RV) failure leading to death. MetS is a recognized risk factor for PH, particularly in patients suffering from PH associated with left-sided heart failure (WHO Group 2 PH) for which there are no approved therapies. Activins and growth differentiation factors (GDFs) are implicated in both PH pathology as well as body composition and metabolism by genetic disease association, preclinical, translational, and clinical evidence. HS135 is a rationally designed first-in-class activin-receptor (ActR)-based fusion protein that addresses both vascular remodeling and MetS in PH without affecting hematological parameters; hematological effects limit the dosing of other ActR-based agents. Methods: HS135’s ability to counteract vascular remodeling and heart failure in PH was assessed using a rat monocrotaline (MCT) model: a single dose of 60 mg/kg MCT was administered on Day 0 followed by 4 weeks of twice weekly treatment with either HS135 (1, 4, or 16 mg/kg) or vehicle. PH efficacy was assessed at end of study by echocardiography and histological readouts. HS135’s ability to improve body composition and metabolism was assessed in wild type mice by administering HS135 (1, 3, 10, 20, or 50 mg/kg) or vehicle twice weekly for 3 weeks. The effect of HS135 on hematological parameters was assessed by whole blood cell count in non-human primates (NHPs) 2 weeks following a single administration of HS135 at 3 or 30 mg/kg. Results: HS135 at 3 or 30 mg/kg did not lead to changes in hematological parameters in NHPs. Compared to vehicle, HS135 was effective at counteracting the MCT-induced PH phenotype in rats as evidenced by significant reductions in Fulton index and improved echocardiography parameters. In wild type mice, HS135 led to significant improvements in body composition. Conclusions: Contrary to other ActR-based therapies, HS135 did not lead to increases in hematocrit which would limit its dosing. HS135 was efficacious at treating PH while simultaneously improving body composition in preclinical models. Clinical trials with HS135 are expected to commence within 2023.