Why ATYR Shares Are Down Today: Phase 3 Trial Falls Short

aTyr Pharma, Inc. (NASDAQ: ATYR) shares plummeted approximately 83% on September 15, 2025, following the announcement that its Phase 3 EFZO-FIT study of efzofitimod in pulmonary sarcoidosis failed to meet its primary endpoint. The biotechnology company’s stock fell from a previous close of $6.03 to around $1.02 in early trading, representing one of the most significant single-day declines in the company’s trading history. The disappointing results have raised questions about the future development path for efzofitimod, the company’s lead therapeutic candidate for treating interstitial lung diseases.

Phase 3 Study Falls Short of Expectations, Investor Confidence Hit

The EFZO-FIT study, which enrolled 268 patients with pulmonary sarcoidosis, failed to demonstrate a statistically significant reduction in oral corticosteroid use compared to placebo. Patients treated with 5.0 mg/kg efzofitimod showed an average reduction in daily steroid dose to 2.79 mg versus 3.52 mg for placebo patients, with a p-value of 0.3313 that fell well short of statistical significance. This primary endpoint failure triggered the massive sell-off, as investors had been anticipating positive results from what represents the largest interventional study ever completed in sarcoidosis.

Despite missing the main goal, aTyr highlighted several encouraging secondary findings that may provide a pathway forward. The study showed that 52.6% of patients in the 5.0 mg/kg efzofitimod group achieved complete steroid withdrawal at week 48 compared to 40.2% on placebo. Additionally, patients treated with efzofitimod demonstrated improved quality of life scores on the King’s Sarcoidosis Questionnaire-Lung assessment, with a statistically significant improvement (p=0.0479) compared to placebo.

The drug was well-tolerated across both dosing groups, maintaining the consistent safety profile observed in previous trials. aTyr’s management emphasized that the totality of data suggests efzofitimod may still provide meaningful clinical benefits, and the company plans to engage with the FDA to determine potential regulatory pathways despite the primary endpoint miss.

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Shares Sink to 52-Week Low as Market Cap Shrinks

As of 10:11 AM EDT on September 15, 2025, ATYR shares were trading at $1.0201, down $5.0099 or 83.08% from the previous close. The dramatic decline erased approximately $500 million in market capitalization, reducing the company’s valuation to roughly $101 million. Trading volume surged to over 66 million shares, more than 13 times the average daily volume of 4.9 million shares, indicating intense selling pressure from institutional and retail investors alike.

The stock’s performance has been challenging throughout 2025, with year-to-date returns now showing a decline of 71.41% compared to the S&P 500’s positive return of 12.37%. Over the past year, ATYR has fallen 45.53% while the broader market gained 17.48%. The company’s 52-week trading range now spans from $1.00 to $7.29, with the current price representing the lower bound of that range.

Analyst price targets for ATYR range from $9.50 to $35.00, with an average target of $20.15, suggesting significant upside potential if the company can successfully navigate regulatory discussions with the FDA. However, these targets will likely face downward revisions following the trial results, as analysts reassess the commercial prospects for efzofitimod in pulmonary sarcoidosis and factor in the increased regulatory uncertainty surrounding the program.

Disclaimer: The author does not hold or have a position in any securities discussed in the article. All stock prices were quoted at the time of writing.