Gene Therapy to Treat Ethanol-induced Osteoporosis Associated with Aldehyde Dehydrogenase 2 Deficiency in Post-menopausal East Asian Women

Abstract. ENYX Therapeutics, LLC, is an early-stage biotechnology company focused on using in vivo gene therapy technologies to treat hereditary disorders of unmet medical need. ENYX is developing an in vivo gene therapy strategy to mitigate the high risk for osteoporosis related hip fracture in alcohol consuming post-menopausal East Asian women with aldehyde dehydrogenase 2 deficiency (ALDH2D). ALDH2D is a hereditary disorder affecting 8% of the world population, and 35-45% of people of East Asian background. ALDH2 is a key enzyme for ethanol metabolism; with ethanol ingestion, ALDH2 mutations result in systemic accumulation of toxic acetaldehyde. The most common variant is the ALDH2*2 allele (E487K). Heterozygotes have <50% ALDH2 enzymatic activity; homozygotes have <4% due to the dominant negative function of the mutant protein in the tetrameric enzyme. The combination of acetaldehyde and ethanol suppresses early osteoblast progenitor formation, leading to decreased bone formation, osteopenia and eventually osteoporosis. ENYX’s proposed therapy is a one-time intravenous administration of ENX03 (AAVrh.10hALDH2), an adeno- associated virus serotype 10 gene transfer vector expressing the normal human ALDH2 coding sequence. In collaboration with the Crystal laboratory at Weill Cornell, osteopenia has been assessed in 2 mouse models of ALDH2 deficiency. After chronic ethanol ingestion, these models have high serum acetaldehyde levels and develop a striking osteopenia phenotype quantified by microcomputed tomography (µCT) and histology with significantly lower bone volume/total volume, cortex thickness, trabecular number and thickness, and increased trabecular space. When pretreated with intravenous administration of ENX03, there was remarkable prevention of these bone abnormalities. In alcohol- consuming mice with preexisting osteopenia, ENX03 increased cortical bone thickness, i.e., ENX03 both prevents and reverses the osteopenia associated with ALDH2 deficiency and chronic ethanol ingestion. The goal of this Phase II STTR, is to translate ENX03 therapy of ALDH2 deficiency toward the clinic by: aim 1 - having a pre-IND meeting with the FDA; aim 2 - manufacturing clinical grade ENX03; aim 3 - carrying out a safety/toxicology study; and aim 4 - submit and gain approval from the FDA of an Investigational New Drug application to initiate a clinical trial focused on ENX03 preventing hip fracture in alcohol consuming post-menopausal East Asian women with ALDH2 deficiency and osteoporosis, a phenotype with a high risk for hip fracture.