General Information

Enspryng (satralizumab-mwge) is an interleukin-6 (IL-6) receptor antagonist.

Enspryng is specifically indicated for the treatment of neuromyelitis optica spectrum disorder (NMOSD) in adult patients who are anti-aquaporin-4 (AQP4) antibody positive.

Assessments prior to the first dose of Enspryng should include screenings for hepatitis B, tuberculosis and liver transaminases. Because vaccination with live-attenuated or live vaccines is not recommended during treatment with Enspryng, administer all immunizations according to immunization guidelines at least 4 weeks prior to initiation of Enspryng for live or live-attenuated vaccines and, whenever possible, at least 2 weeks prior to initiation of Enspryng for non-live vaccines.

Enspryng is supplied as an injection for subcutaneous administration. The recommended loading dosage of Enspryng for the first three administrations is 120 mg by subcutaneous injection at Weeks 0, 2, and 4, followed by a maintenance dosage of 120 mg every 4 weeks. Please see the drug label for recommended doses for missed or delayed treatments.

Mechanism of Action

Enspryng (satralizumab-mwge) is a recombinant humanized anti-human interleukin 6 (IL-6) receptor monoclonal antibody based on a human IgG2 framework. The precise mechanism by which satralizumab-mwge exerts therapeutic effects in NMOSD is unknown but is presumed to involve inhibition of IL-6-mediated signaling through binding to soluble and membrane-bound IL-6 receptors.

Clinical Trial Results

The FDA approval of Enspryng was based on results from two randomized controlled Phase III clinical trials, the SAkuraStar and SAkuraSky studies.

SAkuraStar was a multicenter, randomized, double-blind, placebo-controlled study to evaluate the efficacy and safety of Enspryng monotherapy. Ninety-five adult patients were randomized to either of the following two treatment groups in a 2:1 ratio: Enspryng (120 mg) or placebo. Both treatments were administered subcutaneously at week 0, 2, and 4. The subsequent treatment was continued at 4-week intervals. The double-blind treatment period ended at 1.5 years after the enrollment of the last patient.The primary endpoint is the time to first protocol-defined relapse (PDR), adjudicated by an independent review committee in the double-blind period. The time to first relapse was significantly longer in Enspryng treated patients compared to patients who received placebo (risk reduction 55%). In the anti-AQP4 antibody positive population, there was a 74% risk reduction. There was no evidence of a benefit in the anti-AQP4 antibody negative patients.

SAkuraSky was a multicenter, randomized, double-blind, placebo-controlled study to evaluate the efficacy and safety of Enspryng added to baseline immunosuppressant therapy in patients with NMOSD. Seventy-six adult patients were randomized to either of the following two treatment groups in a 1:1 ratio: Enspryng (120 mg) or placebo added to baseline therapy (azathioprine, mycophenolate mofetil and/or corticosteroids). Both treatments were administered subcutaneously at week 0, 2, and 4. The subsequent treatment was continued at 4-week intervals. The double-blind treatment period ended when patients experienced a PDR; the study ended when the total number of PDRs reached 26. The primary endpoint was the time to first PDR as adjudicated by an independent review committee in the double-blind period. The time to the first confirmed relapse was significantly longer in patients treated with Enspryng compared to patients who received placebo (risk reduction 62%). In the anti-AQP4 antibody positive population, there was a 78% risk reduction. There was no evidence of a benefit in the anti-AQP4 antibody negative patients.