Material Event (Form 8-K)

Item 8.01 Other Events.

On September 24, 2026, aTyr Pharma, Inc. (the Company) announced that it has reached alignment with the U.S. Food and Drug Administration (FDA) on the protocol for a Phase 3 study of its lead therapeutic candidate, efzofitimod, in patients with chronic, symptomatic pulmonary sarcoidosis with restrictive lung disease (Planned Phase 3 Study). The Company expects to focus on regulatory submissions in the U.S. and Europe as it initiates study-related activities in the fourth quarter of 2026.

The Planned Phase 3 Study will be a global, randomized, double-blind, placebo-controlled study to evaluate the efficacy and safety of efzofitimod in patients with moderate to severe pulmonary sarcoidosis. The 54-week Planned Phase 3 Study will consist of two parallel cohorts randomized equally to either 5.0 mg/kg efzofitimod or placebo dosed intravenously once every 3 weeks for a total of 17 doses. The Planned Phase 3 Study is intended to enroll up to approximately 372 patients with symptomatic pulmonary sarcoidosis with restrictive lung disease who are receiving a stable dose of ≤ 5.0 mg daily oral corticosteroid and/or a background immunosuppressant. All background treatment will remain stable throughout the duration of the Planned Phase 3 Study. The primary endpoint of the Planned Phase 3 Study will be change from baseline in forced vital capacity (FVC) at week 48 and the key secondary endpoint will be change from baseline in the King's Sarcoidosis Questionnaire (KSQ)-Lung score at week 48.

The Planned Phase 3 Study design is supported by data from a subgroup analysis of the Phase 3 EFZO-FIT™ study that showed that patients with pulmonary sarcoidosis with restrictive lung disease (defined as FVC percent predicted ≤ 80% with a normal FEV1/FVC ratio) who were treated with 5.0 mg/kg efzofitimod experienced a clinically meaningful benefit in FVC and improvements in multiple patient-reported outcomes, including the KSQ-Lung score, compared to placebo. These findings were presented at the World Association of Sarcoidosis and Other Granulomatous Disorders 2026 Congress.

Future development of efzofitimod in the Planned Phase 3 Study in pulmonary sarcoidosis will require the Company to obtain additional capital through equity or debt offerings, grant funding, collaborations, strategic partnerships and/or licensing arrangements.