What happened
Shares of Aeglea BioTherapeutics (AGLE -2.86%), a clinical-stage biopharmaceutical company, are falling today in response to mixed clinical-trial data. Investors nervous about the future of the company's lead candidate pushed the stock 36.6% lower as of 11:53 a.m. ET on Monday.
So what
Aegla BioTherapeutics' lead candidate, pegzilarginase, is an enzyme replacement therapy for patients with an ultra-rare amino-acid metabolism disorder called arginase 1 deficiency. The trial reached its primary endpoint by dramatically reducing circulating arginine by 80% compared to baseline measurements.
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The stock is getting beaten down today because investors are disappointed with two outcome measurements that were secondary endpoints in the pivotal study. Patients treated with pegzilarginase improved their average two-minute walking distance scores by 7.4 meters after 24 weeks. Unfortunately for Aeglea, that wasn't significantly better than the placebo group, which improved by 1.9 meters.
Patient scores on the gross motor function test improved by 4.2 points compared to a 0.4 point worsening for the placebo group. While this indicates a benefit, there weren't enough patients tested to consider this improvement statistically significant, either.
Now what
Aeglea BioTherapeutics still plans to submit an application for pegzilarginase to the Food and Drug Administration (FDA) in the first half of 2022. The company already rolled all 32 patients from the phase 3 trial into a longer single-arm extension study.
In a previous single-arm study, 11 out of 14 patients showed mobility measurement improvements after 56 weeks on pegzilarginase. Considering the dearth of available treatment options for patients with this progressively debilitating disorder, similarly positive long-term outcomes in the new extension study could be enough to convince the FDA to give pegzilarginase a green light.
