Aeglea BioTherapeutics, Inc. (NASDAQ: AGLE), a clinical-stage biotechnology company developing a new generation of human enzyme therapeutics as innovative solutions for rare metabolic diseases, today announced that it has completed patient randomization for PEACE (Pegzilarginase Effect on Arginase 1 Deficiency Clinical Endpoints), the pivotal Phase 3 clinical trial investigating pegzilarginase for the treatment of Arginase 1 Deficiency (ARG1-D). ARG1-D is a rare, progressive disease characterized by high levels of arginine which results in severe mobility limitations due to spasticity, seizures, developmental delay, intellectual disability and early mortality. Topline data from PEACE are expected in the fourth quarter of 2021.

"Completing randomization in our pivotal Phase 3 PEACE study is an important milestone given the challenges our investigators and patient families have faced with COVID-19. Exceeding our enrollment target of 30 patients with 32 randomized during a global pandemic demonstrates the high levels of enthusiasm in the ARG1-D patient and physician community and underscores the significant need for effective treatment options for this patient population," said Anthony G. Quinn, M.B. Ch.B., Ph.D., president and chief executive officer of Aeglea. "Pegzilarginase has the potential to be the first FDA-approved therapy to address the driver of the disease, persistently high levels of arginine, and to improve the quality of life for ARG1-D patients and their families."

Pegzilarginase is a novel, recombinant human arginase 1 enzyme that has been shown to lower toxic levels of the amino acid arginine in patients with ARG1-D. PEACE is a global, randomized, double-blind trial designed to assess the effects of treatment with pegzilarginase versus placebo over 24 weeks. The trial enrolled 32 ARG1-D patients aged two years and older, who had plasma arginine levels greater than 250 µM and a baseline deficit in at least one clinical response assessment. The primary endpoint is assessment of plasma arginine reduction from baseline and the key secondary endpoints include the 2 Minute Walk Test and Gross Motor Function Measure Part E as assessments of clinically meaningful effects, in addition to safety and pharmacokinetics. Previous studies have demonstrated that plasma arginine control has the potential to improve the clinical status and to slow disease progression in patients with ARG1-D.

For more information on the PEACE study, please visit http://clinicaltrials.gov.

About Pegzilarginase in Arginase 1 Deficiency

Pegzilarginase is a novel recombinant human enzyme, which has been shown to rapidly and sustainably lower levels of the amino acid arginine in plasma. Aeglea is developing pegzilarginase for the treatment of patients with ARG1-D, a rare debilitating and progressive disease characterized by the accumulation of arginine. ARG1-D presents in early childhood and patients experience spasticity, seizures, developmental delay, intellectual disability and early mortality. Aeglea's Phase 1/2 and Phase 2 open-label extension (OLE) data for pegzilarginase in patients with ARG1-D demonstrated clinical improvements and sustained lowering of plasma arginine. The Company's ongoing single, global pivotal Phase 3 PEACE trial is designed to assess the effects of treatment with pegzilarginase versus placebo over 24 weeks with a primary endpoint of plasma arginine reduction. Pegzilarginase has received multiple regulatory designations, including Rare Pediatric Disease, Breakthrough, Fast Track and Orphan Drug Designations from the U.S. Food and Drug Administration as well as Orphan Drug Designation from the European Medicines Agency.

About Aeglea BioTherapeutics

Aeglea BioTherapeutics is a clinical-stage biotechnology company redefining the potential of human enzyme therapeutics to benefit people with rare metabolic diseases with limited treatment options. Aeglea's lead product candidate, pegzilarginase, is in a pivotal Phase 3 trial for the treatment of Arginase 1 Deficiency and has received both Rare Pediatric Disease and Breakthrough Therapy Designation. In the second quarter of 2020, the Company initiated a Phase 1/2 clinical trial of AGLE-177 for the treatment of Homocystinuria. AGLE-177 has also been granted Rare Pediatric Disease Designation. Aeglea has an active discovery platform focused on engineering small changes in human enzymes to have a big impact on the lives of patients and their families. For more information, please visit http://aeglea.com.

Aeglea Safe Harbor / Forward Looking Statements

This press release contains "forward-looking" statements within the meaning of the safe harbor provisions of the U.S. Private Securities Litigation Reform Act of 1995. Forward-looking statements can be identified by words such as: "anticipate," "intend," "plan," "goal," "seek," "believe," "project," "estimate," "expect," "strategy," "future," "likely," "may," "should," "will" and similar references to future periods. These statements are subject to numerous risks and uncertainties that could cause actual results to differ materially from what we expect. Examples of forward-looking statements include, among others, statements we make regarding our ability to obtain regulatory approval for, and commercialize, pegzilarginase, recognize milestone and royalty payments from our agreement with Immedica, cash forecasts, the timing and success of our clinical trials and related data, the timing and expectations for regulatory submissions and approvals, timing and results of meetings with regulators, the timing of announcements and updates relating to our clinical trials and related data, our ability to enroll patients into our clinical trials, the expected impact of the COVID-19 pandemic on our operations and clinical trials, success in our collaborations, the potential addressable markets of the our product candidates and the potential therapeutic benefits and economic value of our lead product candidate or other product candidates. Further information on potential risk factors that could affect our business and its financial results are detailed in our most recent Annual Report on Form 10-K for the year ended December 31, 2020 filed with the Securities and Exchange Commission (SEC), and other reports as filed with the SEC. We undertake no obligation to publicly update any forward-looking statement, whether written or oral, that may be made from time to time, whether as a result of new information, future developments or otherwise.