Enspryng

Enspryng is used to treat:

• neuromyelitis optica spectrum disorder (NMOSD) in adults who are aquaporin-4 (AQP4) antibody positive, and
• thyroid eye disease (TED) in adults, regardless of how active or how long-standing the eye disease is.

It is given as an injection under the skin (subcutaneously) every 4 weeks after an initial loading period.

Enspryng (satralizumab-mwge) first gained FDA approval for NMOSD on August 14, 2020. The FDA approved it for thyroid eye disease on October 16, 2026. There is no generic or biosimilar.

Enspryng is a solution provided in a single-dose prefilled syringe or a single-dose prefilled autoinjector. It is given as an injection under the skin (subcutaneously).

• See the Instructions for Use inside the carton for complete instructions on the right way to prepare and inject Enspryng. There is a separate Instructions for Use for the prefilled syringe and for the autoinjector.
• Enspryng is intended for self-injection under the guidance of a healthcare provider. If your healthcare provider decides that you or your caregiver can give your injections, you or your caregiver should receive training on the right way to prepare and inject Enspryng.
• Before injecting, take Enspryng out of the refrigerator and let it sit at room temperature outside of the carton for 30 minutes. Do not warm it any other way.
• Use Enspryng within 5 minutes of removing the cap or the needle may clog. Do not remove the cap until you are ready to inject. If using the autoinjector, do not touch the green needle shield or put the cap back on after it has been removed, as this may unintentionally activate the device.
• Always inject all of the medicine in the prefilled syringe or autoinjector.
• The injections during the loading period are given 1 time every 2 weeks for the first 3 doses (at Weeks 0, 2, and 4).
• After this, Enspryng is injected every 4 weeks (maintenance period), starting at Week 8.
• Rotate injection sites. Do not inject into skin that is damaged, bruised, red, hard, or tender.
• Keep using Enspryng for as long as your healthcare provider tells you to.

What happens if I miss a dose?

If you miss a dose of Enspryng, talk to your healthcare provider about restarting dosing. The schedule for making up a missed dose depends on how long it has been since your last dose.

You should not use Enspryng if you have:

• a known allergy (hypersensitivity) to satralizumab or to any of the inactive ingredients in Enspryng
• an active hepatitis B infection
• active tuberculosis, or latent (inactive) tuberculosis that has not been treated.

Enspryng (satralizumab) is thought to work by blocking receptors for a protein called IL-6 (interleukin-6). By attaching to these receptors, Enspryng stops inflammatory signals from getting through and reduces harmful inflammation.

In NMOSD, this helps prevent relapses and protects the optic nerves and spinal cord from being damaged by your own immune system. In thyroid eye disease, reducing IL-6 driven inflammation can help lessen eye bulging (proptosis) and other signs and symptoms.

Enspryng belongs to the drug class called interleukin inhibitors. Specifically, it is an IL-6 receptor inhibitor.

Before you use Enspryng, tell your healthcare provider about all of your medical conditions, including if you:

• Have or think you have an infection
• Have liver problems
• Have ever had hepatitis B or are a carrier of the hepatitis B virus
• Have had or have been in contact with someone with tuberculosis
• Have had a recent vaccination or are scheduled to receive any vaccination
• Are pregnant, think that you might be pregnant, or plan to become pregnant
• Are breastfeeding or plan to breastfeed.

Before your first dose, your healthcare provider will screen you for hepatitis B virus and tuberculosis, and will check your liver enzymes (transaminases) and bilirubin.

Pregnancy

It is not known if Enspryng will harm your unborn baby.

Pregnancy Registry: There is a registry for pregnant women who take Enspryng for NMOSD. The purpose of this registry is to check the health of the pregnant mother and her baby. If you are pregnant or become pregnant while taking Enspryng for NMOSD, talk to your healthcare provider about how you can join this pregnancy registry, or you may contact the registry at 1-833-277-9338 to enroll.

Breastfeeding

It is not known if Enspryng passes into your breast milk. Talk to your healthcare provider about the best way to feed your baby if you take Enspryng.

Common side effects

The most common side effects of Enspryng in people treated for NMOSD are:

• Sore throat, runny nose (nasopharyngitis)
• Rash
• Fatigue
• Extremity pain
• Headache
• Upper respiratory tract infection
• Nausea
• Inflammation of the stomach lining (gastritis)
• Joint pain.

The most common side effects in people treated for thyroid eye disease are upper respiratory tract infection and increased liver enzymes (increased alanine aminotransferase, or ALT).

Serious side effects and warnings

Enspryng may cause the following serious side effects.

Infections

Enspryng can increase your risk of serious infections, some of which can be life-threatening. Talk to your healthcare provider if you are being treated for an infection, or call them right away if you think you have signs of an infection, with or without a fever, such as:

• Chills, feeling tired, muscle aches, a cough that will not go away, or a sore throat
• Skin redness, swelling, tenderness, pain, or sores on your body
• Diarrhea, belly pain, or feeling sick
• Burning when you urinate or urinating more often than usual.

Your healthcare provider will check if you have an infection and treat it if needed before you start or continue to take Enspryng.

• Your healthcare provider should test you for hepatitis B and tuberculosis (TB) before you start taking Enspryng.
• All required vaccinations should be completed before starting this medicine. People using Enspryng should not be given 'live' or 'live-attenuated' vaccines. 'Live' or 'live-attenuated' vaccines should be given at least 4 weeks before you start Enspryng. Your healthcare provider may recommend that you get a 'non-live' (inactivated) vaccine, such as some of the seasonal flu vaccines. If you plan to get a 'non-live' (inactivated) vaccine, it should be given, whenever possible, at least 2 weeks before you start Enspryng.

Increased liver enzymes

Enspryng can increase your liver enzymes. Your healthcare provider should order blood tests to check your liver enzymes before and while you are taking Enspryng.

• Your healthcare provider will tell you how often you will need to have these blood tests.
• Make sure you get all of your follow-up blood tests as ordered by your healthcare provider.
• Your healthcare provider will tell you if you need to wait to start Enspryng if your liver enzymes are increased.

Low neutrophil count

Enspryng can cause a decrease in the neutrophil counts in your body. Neutrophils are white blood cells that help the body fight off bacterial infections. Your healthcare provider should order blood tests to check your neutrophil count while you are taking Enspryng.

Serious allergic reactions

Serious allergic reactions that may be life-threatening have happened with other medicines like Enspryng. Tell your healthcare provider before taking your next dose if you had hives, rash, or flushing after your injection. Seek medical attention right away if you have any symptoms of a serious allergic reaction, such as:

• Shortness of breath or trouble breathing
• Dizziness or feeling faint
• Swelling of your lips, face, or tongue
• Moderate or severe stomach (abdominal) pain or vomiting
• Chest pain.

Notes:

It is not known if Enspryng is safe and effective in children.

These are not all the possible side effects of Enspryng. Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088. You may also report side effects to Genentech at 1-888-835-2555.

Adult dose of Enspryng for NMOSD

• Loading phase (Weeks 0, 2, and 4): 120 mg subcutaneously
• Maintenance phase (Week 8 and every 4 weeks thereafter): 120 mg subcutaneously

Adult dose of Enspryng for thyroid eye disease

The dose for thyroid eye disease is based on body weight:

Dosing is based on actual body weight. The safety and effectiveness of Enspryng have not been established in people with thyroid eye disease who weigh less than 40 kg.

Rotate injection sites. Do not inject into damaged or irritated skin.

• Strength: 120 mg/mL prefilled syringe
• Strength: 120 mg/mL prefilled autoinjector
• Strength: 180 mg/1.5 mL prefilled autoinjector

NMOSD

Two major clinical trials tested Enspryng's effectiveness in NMOSD:

• SAkuraSky (NCT02028884): When patients added Enspryng to their existing immune-suppressing medications, they had 62% fewer relapses compared to those taking a placebo.
• SAkuraStar (NCT02073279): Adults with AQP4-positive NMOSD who took Enspryng alone (without other treatments) had 55% fewer relapses.

Thyroid eye disease

Enspryng was studied in two identical Phase 3 trials in adults with thyroid eye disease, SatraGO-1 (NCT05987423) and SatraGO-2 (NCT06106828), which together enrolled 258 patients with active or inactive disease. The main measure was the proptosis responder rate at Week 24 (at least a 2 mm reduction in eye bulging in the study eye, without worsening in the other eye).

• In SatraGO-2, 52.9% of patients on Enspryng were proptosis responders compared with 23.4% on placebo. More patients also had an improvement in double vision (60.7% versus 25.8%).
• SatraGO-1 did not meet its main goal at Week 24 (49.0% on Enspryng versus 31.2% on placebo, a difference that was not statistically significant).

The safety profile seen in the thyroid eye disease trials was consistent with what is already known for Enspryng in NMOSD.

Tell your healthcare provider about all the medicines you are taking, including prescription and over-the-counter medicines, vitamins, and herbal supplements.

No formal drug-drug interaction studies have been performed with Enspryng.

Store Enspryng in the refrigerator between 36 and 46 degrees Fahrenheit (2 and 8 degrees Celsius) in the original carton.

• Protect from light.
• Do not freeze, and do not use the syringe or autoinjector if it has been frozen.
• Do not shake.

Enspryng, if unopened, can be removed from and returned to the refrigerator if needed. The total combined time out of the refrigerator should not be more than 8 days at a temperature that does not go above 86 degrees Fahrenheit (30 degrees Celsius).

Active ingredient: satralizumab-mwge.

Inactive ingredients: L-arginine, L-aspartic acid, L-histidine, poloxamer 188, and Water for Injection.

Available as a 120 mg/mL solution (prefilled syringe or autoinjector, each delivering 120 mg) and as a 180 mg/1.5 mL solution (autoinjector delivering 180 mg). The prefilled syringe and autoinjector are not made with natural rubber latex.