Key Takeaways

• The FDA has granted priority review to Genentech's supplemental BLA for Enspryng for the treatment of thyroid eye disease, with a regulatory decision expected by October 15, 2026
• If approved, Enspryng would offer a subcutaneous, at-home treatment option for TED with a safety profile consistent with its established use in neuromyelitis optica spectrum disorder

Genentech has received FDA priority review for a supplemental Biologics License Application (sBLA) seeking approval of Enspryng (satralizumab) for the treatment of thyroid eye disease (TED), positioning the therapy as a potential new treatment option for patients with the autoimmune condition.

The FDA accepted the application based on results from the global phase 3 SatraGO-1 and SatraGO-2 clinical trials. Under the priority review designation, the agency is expected to issue a decision by October 15, 2026.

If approved, Enspryng would introduce a subcutaneous, at-home treatment option for TED that targets the disease through inhibition of the interleukin-6 (IL-6) receptor, offering a mechanism distinct from currently available therapies.

“The FDA’s decision to grant priority review to Enspryng is an important step toward expanding treatment options for people living with thyroid eye disease,” said Levi Garraway, MD, PhD, chief medical officer and head of Global Product Development. “By targeting the underlying disease biology with a novel mechanism of action, this subcutaneous therapy has the potential to introduce a new treatment approach that combines clinical efficacy and a favorable safety profile with the convenience of at-home administration.”

The supplemental application is supported by findings from the pivotal SatraGO clinical development program, which consisted of two identically designed, randomized, placebo-controlled phase 3 studies evaluating adults with active, moderate-to-severe TED and chronic inactive disease. Across both trials, 258 patients from 19 countries were randomized 1:1 to receive either satralizumab or placebo. The primary endpoint measured the proportion of patients with active TED achieving at least a 2-mm reduction in proptosis in the study eye at Week 24.

In SatraGO-2, 53% of patients treated with Enspryng achieved the primary endpoint compared with 23% of patients receiving placebo, a statistically significant difference. In SatraGO-1, 49% of patients receiving Enspryng achieved a proptosis response compared with 31% in the placebo group. Although the difference favored treatment, it did not reach statistical significance.

According to Genentech, the totality of evidence from the two studies demonstrated consistent, clinically meaningful improvements across multiple measures of disease activity.

Beyond proptosis, Enspryng demonstrated benefits across secondary efficacy endpoints. Among patients with active TED, between 78% and 90% experienced reductions in Clinical Activity Score (CAS), while improvements in diplopia were observed in 44% to 61% of patients across the two studies.

The company reported that no new safety signals emerged during the phase 3 program. The observed safety profile was consistent with the established experience for Enspryng, which is currently approved for neuromyelitis optica spectrum disorder.