Despite hitting the primary endpoint in its phase III study of pegzilarginase in treating arginase 1 deficiency, Aeglea Biotherapeutics Inc. had a tough go of it Dec. 6 as the price of its stock (NASDAQ:AGLE) plunged 36.5% to close at $3.81 per share. The study hit its primary endpoint with a statistically significant reduction in plasma arginine from baseline after 24 weeks of treatment with pegzilarginase (p<0.0001). The study results were positive enough to prompt Aeglea to say it planned to submit a BLA to the FDA in the first half of 2022.