OR25-01 Durable CYP21A2 Gene Therapy in Non-Human Primates for Treatment of Congenital Adrenal Hyperplasia

Severe Congenital Adrenal Hyperplasia (CAH) is most commonly caused by genetic defects in the CYP21A2 gene, which leads to a deficiency of 21-hydroxylase enzyme and disruption in the biosynthesis of Adrenal corticosteriods. Despite treatment with corticosteroids, patients remain at significant risk for adrenal crisis, experiencing a 3-fold higher mortality rate than age matched controls. They also suffer from significant infertility, bone, metabolic, and cardiovascular disease, and hyperandrogenism in women leading to genital abnormalities, hirsutism, and other complications. We are developing an AAV5- based gene therapy (BBP-631) that will provide a functional copy of the CYP21A2 gene to the adrenal glands of CAH patients. To determine the durability of this therapy we treated cynomolgus monkeys with increasing doses of BBP-631 via intravenous injection. At 4-, 12- and 24-weeks post treatment, expression of hCYP21A2 mRNA and vector genome copies (VGC) in the adrenals and other peripheral tissues was measured. VGC was present in the liver and adrenals at 4 weeks, with durable detection through 24 weeks and total vg levels were dose dependent. hCYP21A2 RNA expression in adrenal and liver tissues was also dose dependent and continued to increase from 4 weeks through 12 weeks. There were no adverse safety signals in any of the treated animals. This data combined with efficacy data of BBP-631 in a Cyp21-/- mouse model supports our continued clinical development of BBP-631 as a treatment for congenital adrenal hyperplasia.