Another refuse-to-file for a small biotech — is the FDA using RTFs to manage its workload?

The latest RTF letter, disclosed Thursday by Aeglea BioTherapeutics, a penny-stock, clinical-stage biotech company calls for new efficacy data to be included in its BLA for pegzilarginase for the treatment of the rare, progressive and debilitating disease characterized by high levels of arginine, and known as Arginase 1 Deficiency. The company’s stock price fell by more than 40% on Thursday.