Enspryng (satralizumab)

In NMOSD it is one of 4 approved targeted drugs, alongside the complement blockers Soliris and Ultomiris and the B-cell drug Uplizna, and the only one patients inject themselves. In thyroid eye disease it would be the first drug that does not block IGF-1R, trading a smaller effect on eye bulging for a monthly at-home injection and no hearing warning.

Interleukin-6 is an immune messenger that keeps inflammation going and helps B cells turn into the plasma cells that make harmful antibodies. Satralizumab is an antibody that sits on the IL-6 receptor so the messenger cannot deliver its signal. Its engineering is what sets it apart from the older IL-6 receptor drug tocilizumab: a recycling design lets each satralizumab molecule bind the receptor strongly and repeatedly, which Genentech says gives sustained IL-6 inhibition and supports dosing every 4 weeks. In NMOSD that calms the attacks on the optic nerves and spinal cord. In thyroid eye disease, where IL-6 levels rise with disease activity, the same block is meant to quiet the inflammation that swells the tissue behind the eye.

The label carries no boxed warning. Its warnings are the ones shared by IL-6 receptor blockers: an increased risk of infections including serious and potentially fatal ones, raised liver enzymes, lowered neutrophil counts and hypersensitivity reactions. Patients are screened for hepatitis B and tuberculosis before the first dose, liver enzymes are checked every 4 weeks for the first 3 months and then every 3 months for a year, neutrophils are checked 4 to 8 weeks after starting, and live vaccines are not given during treatment. The most common side effects in the NMOSD trials (at least 15%) were nasopharyngitis, headache, upper respiratory infection, gastritis, rash, joint pain, limb pain, fatigue and nausea. In the thyroid eye disease trials through week 24, serious adverse events occurred in 4.5% and 3.1% of patients on satralizumab against 3.2% and 4.8% on placebo, with no deaths and no serious infections; one trial saw more raised liver enzymes and low neutrophil counts on the drug. No hearing problems were reported, which separates it from the IGF-1R drugs for thyroid eye disease.

A specialty biologic sold by Genentech. The copay program covers commercially insured patients and the Genentech Patient Foundation covers eligible uninsured patients; Genentech's disclosed list price is $18,905.57 per 120 mg syringe (wholesale acquisition cost as of July 1, 2026).

Pick your insurance to see which help fits. Drugmaker copay cards can't be used with Medicare, Medicaid or TRICARE; charity funds are the usual route there.

More ways to get help paying for treatment →

Approved for adults with neuromyelitis optica spectrum disorder who test positive for anti-AQP4 antibodies. Use in thyroid eye disease and MOG antibody-associated disease is not yet approved; both are under FDA review. Patients with active hepatitis B or untreated latent tuberculosis cannot take it.

Source: Enspryng patient site, Genentech

Access program details are provided for informational purposes and may vary based on insurance coverage, geographic location, and individual circumstances. Confirm current eligibility directly with the manufacturer or your specialty pharmacy.

NMOSD approval rested on 2 Phase 3 trials, SAkuraStar (satralizumab alone) and SAkuraSky (added to existing immunosuppressants), both of which cut the risk of relapse in anti-AQP4 antibody positive patients^[1][2]. For thyroid eye disease, the identically designed Phase 3 trials SatraGO-1 (NCT05987423, 131 patients) and SatraGO-2 (NCT06106828, 127 patients) measured the share of active-disease patients whose eye bulging improved by at least 2 mm at week 24. SatraGO-2 met its primary endpoint, 52.9% versus 23.4% on placebo (p = 0.0011), with 89.6% versus 63.3% achieving a 2-point drop in clinical activity score and 60.7% versus 25.8% improving in double vision. SatraGO-1 did not, 49.0% versus 31.2% (p = 0.0715), although its inflammation measures favored the drug significantly (78.0% versus 54.9% for the activity score)^[5][6][7]. For MOG antibody-associated disease, the Phase 3 METEOROID trial cut the risk of relapse by 68%, with 87% of treated patients relapse-free at 48 weeks against 67% on placebo^[4].

Satralizumab was created by Chugai Pharmaceutical in Japan as SA237, a re-engineered successor to tocilizumab with recycling antibody technology, and is sold by Genentech and Roche. The FDA approved it as Enspryng on August 14, 2020 for anti-AQP4 antibody positive NMOSD, the first self-injected treatment for that disease; it is now approved in about 90 countries^[2][3]. The thyroid eye disease trials began in late 2023, their primary results were presented at the ASOPRS meeting in October 2025, and the FDA accepted a supplemental application with priority review on June 29, 2026, setting a decision date of October 15, 2026^[3]. A second supplemental application, for MOG antibody-associated disease, was accepted with priority review on September 9, 2026 with a decision due January 10, 2027^[4].