Why Did Aeglea BioTherapeutics Shares Nosedived To 52-Week Low On Monday Premarket?

Aeglea BioTherapeutics Inc AGLE has announced data from the Phase 3 study of pegzilarginase in Arginase 1 Deficiency (ARG1-D) patients aged two years and older. ARG1-D is a rare disease characterized by high levels of the amino acid arginine. The disease manifestations include spasticity, developmental delay, intellectual disability, and seizures.

• The study met the primary endpoint with a statistically significant reduction in plasma arginine from baseline after 24 weeks.
• At six months, 21 patients dosed with pegzilarginase posted an 80% reduction in mean plasma arginine over placebo. 
• Meanwhile, 90.5% of patients receiving pegzilarginase reached normal plasma arginine levels compared with no patients in the control arm.
• So what resulted in shares plunging to a 52-week low?
• On two key secondary endpoints, including improvements in a two-minute walk test and a catch-all mobility test known as GMFM-E, peglizarginase failed to best placebo.
• For the two-minute walk test, patients dosed with peglizarginase posted a mean increase in distance walked from a baseline of 7.4 meters compared with an increase of 1.9 meters in control patients, far below the bar for statistical significance.
• On the GMFM-E test, patients dosed with pegzilarginase showed a 4.2-unit increase over baseline compared with a 0.4-unit decline for placebo patients.
• Aeglea said it didn’t flag any new safety concerns in the study and no patients dropping out due to dosing.
• The Company plans to submit a marketing application to the FDA in 1H of 2022.
• Price Action: AGLE shares are down 30.7% at $4.16 during the premarket session on the last check Monday.