To summarize the FDA approval of satralizumab-mwge for thyroid eye disease, the supporting phase 3 trial results, and relevant dosing and safety information.
Approach:
Approval: The FDA approved satralizumab-mwge (Enspryng) for adults with thyroid eye disease (TED). It is the first and only approved at-home subcutaneous treatment for TED; patients or trained caregivers can administer maintenance injections every 4 weeks.
Evidence: Approval was supported by two identically designed, phase 3, double-masked, placebo-controlled trials, SatraGO-1 and SatraGO-2, which enrolled 258 adults across 19 countries. The primary endpoint was the proportion of patients with active TED who achieved a reduction in proptosis of at least 2 mm from baseline at week 24.
Key Findings:
SatraGO-2 met its primary endpoint: proptosis response occurred in 52.9% of satralizumab-treated patients and 23.4% of placebo recipients.
In SatraGO-2, diplopia improved in 60.7% of satralizumab-treated patients and 25.8% of placebo recipients.
SatraGO-1 did not meet its prespecified primary endpoint; proptosis response occurred in 49.0% of satralizumab-treated patients and 31.2% of placebo recipients.
The trials reported no new safety signals. No serious infections occurred in the satralizumab groups during the 24-week assessment.
Interpretation:
The approval expands satralizumab-mwge’s indication beyond aquaporin-4 antibody–positive neuromyelitis optica spectrum disorder, for which it was approved in 2020. The trials did not directly compare the treatment with other approved TED therapies.
Limitations:
SatraGO-1 did not meet its prespecified primary endpoint.
The studies did not directly compare satralizumab-mwge with other approved treatments.
The reported safety assessment covered 24 weeks.
Conclusion:
The FDA approval makes satralizumab-mwge the first and only approved at-home subcutaneous treatment for adults with TED. Evidence came from two phase 3 trials: SatraGO-2 met its primary endpoint, while SatraGO-1 did not. The trials did not directly compare satralizumab-mwge with other approved TED treatments.
