Enspryng (Satralizumab)
Interleukin-6 (IL-6) Receptor Inhibitor for NMOSD
Enspryng (satralizumab) is a monoclonal antibody that targets the interleukin-6 (IL-6) receptor to treat neuromyelitis optica spectrum disorder (NMOSD) in adults and adolescents aged 12 and older. By blocking IL-6 signaling, Enspryng reduces the inflammatory processes that damage the optic nerves and spinal cord, helping to prevent debilitating relapses. It is administered as a subcutaneous injection using a pre-filled syringe.
Quick Facts
Key Takeaways
- Enspryng (satralizumab) is an IL-6 receptor inhibitor approved to prevent relapses in neuromyelitis optica spectrum disorder (NMOSD) in patients aged 12 and older.
- Loading doses are given every 2 weeks for the first 3 injections, then maintenance doses every 4 weeks by subcutaneous injection.
- The most common side effects are injection-site reactions, headache, joint pain, and low white blood cell counts.
- Treatment should not be started during active infections, and live vaccines must be avoided while on Enspryng.
- Pre-filled syringes must be stored refrigerated (2–8°C) and can be kept at room temperature for up to 8 days if needed.
What Is Enspryng and What Is It Used For?
Enspryng contains the active substance satralizumab, a type of protein known as a humanized monoclonal antibody. Monoclonal antibodies are engineered proteins designed to recognize and bind to specific targets in the body. Satralizumab employs a unique recycling antibody technology that allows it to repeatedly bind to the interleukin-6 (IL-6) receptor, providing sustained blockade of IL-6 signaling with less frequent dosing.
What Is NMOSD?
Neuromyelitis optica spectrum disorder (NMOSD) is a rare autoimmune disease of the central nervous system that primarily affects the optic nerves (causing vision problems) and the spinal cord (causing weakness and sensory changes). Unlike multiple sclerosis, which it was historically confused with, NMOSD is now recognized as a distinct condition with different underlying mechanisms and treatment requirements.
In NMOSD, the immune system malfunctions and attacks the body's own nerve tissue. In approximately 70–80% of cases, this is driven by antibodies against aquaporin-4 (AQP4), a water channel protein found on the surface of certain brain and spinal cord cells called astrocytes. The resulting inflammation causes damage that can lead to:
- Optic neuritis: Inflammation of the optic nerve, causing eye pain and vision loss that can be severe or complete
- Transverse myelitis: Inflammation of the spinal cord, causing weakness or paralysis of the legs or arms, numbness, and bladder or bowel dysfunction
- Area postrema syndrome: Intractable nausea, vomiting, or hiccups lasting days or weeks
NMOSD follows a relapsing course, meaning patients experience attacks (relapses) separated by periods of stability. Each attack can cause permanent neurological damage, making prevention of relapses a critical treatment goal. According to data from international registries, the annual relapse rate in untreated NMOSD ranges from 0.5 to 1.5 attacks per year, and cumulative disability can be severe without effective treatment.
How Does Enspryng Work?
Enspryng works by blocking the effect of interleukin-6 (IL-6), a pro-inflammatory cytokine that plays a central role in the pathological processes driving NMOSD. IL-6 promotes the activation of immune cells, the production of AQP4 antibodies, and the breakdown of the blood-brain barrier, all of which contribute to the nerve damage and inflammation seen during NMOSD relapses.
By blocking IL-6 receptor signaling, Enspryng reduces the inflammatory cascade in the central nervous system, thereby decreasing the risk of relapses. In the pivotal SAkuraSky and SAkuraStar clinical trials, satralizumab demonstrated a statistically significant reduction in relapse risk compared to placebo. In AQP4 antibody-positive patients, the time-to-first-relapse was substantially prolonged, with approximately 74–78% of patients remaining relapse-free at 96 weeks on satralizumab.
Enspryng is approved for use in adults and adolescents from 12 years of age. It can be used either as monotherapy or in combination with immunosuppressive therapy, offering flexibility in treatment approaches depending on the individual patient's disease characteristics and treatment history.
What Should You Know Before Taking Enspryng?
Contraindications
Enspryng must not be used if you have a known hypersensitivity (allergy) to satralizumab or any of the other ingredients in this medicine. If you are unsure whether this applies to you, speak with your doctor, pharmacist, or nurse before using Enspryng.
Warnings and Precautions
Before starting treatment with Enspryng, your healthcare provider needs to be aware of several important considerations that may affect the safety and efficacy of your treatment.
Do not use Enspryng while you have an active infection. Contact your doctor immediately if you develop signs of infection before, during, or after treatment, including: fever or chills, persistent cough, sore throat, cold sores or genital sores (herpes simplex), shingles (herpes zoster), skin redness, swelling or tenderness, nausea, diarrhea, or stomach pain.
Because Enspryng affects the immune system by blocking IL-6 signaling, it can mask the typical signs of infection, such as fever and elevated C-reactive protein (CRP) levels. This means infections may be harder to detect during treatment. Your doctor will wait until any active infection is under control before starting or continuing Enspryng treatment.
Vaccinations
Tell your doctor if you have recently received any vaccine or plan to be vaccinated in the near future. Your doctor will check whether you need any vaccinations before starting Enspryng. Importantly, you must not receive live or live-attenuated vaccines (such as BCG vaccine for tuberculosis or yellow fever vaccine) while being treated with Enspryng, as the medicine’s immunomodulatory effects may increase the risk of infection from live vaccine strains. Inactivated vaccines are generally considered safe, but the immune response may be reduced, so it is best to complete vaccinations before starting treatment where possible.
Liver Monitoring
Enspryng can affect your liver function and may increase the levels of certain liver enzymes in your blood. Your doctor will order blood tests before starting Enspryng and periodically during treatment to monitor your liver function. Contact your doctor immediately if you notice any of the following symptoms, which may indicate liver problems: yellowing of the skin or whites of the eyes (jaundice), dark-colored urine, nausea or vomiting, or abdominal pain.
Blood Cell Monitoring
Your doctor will also monitor your white blood cell counts through regular blood tests before and during treatment. Low white blood cell counts (neutropenia) can increase your susceptibility to infections. If your neutrophil count drops below certain thresholds, your doctor may temporarily pause or discontinue treatment.
Pregnancy and Breastfeeding
If you are pregnant, think you may be pregnant, or are planning to become pregnant, consult your doctor or pharmacist before using Enspryng. There is limited clinical data on the use of satralizumab during pregnancy, and the potential risks to the developing fetus are not fully established. Your doctor will carefully weigh the benefits of treatment against the potential risks.
It is not known whether satralizumab passes into breast milk. Because monoclonal antibodies can potentially be transferred through breast milk, your doctor may advise you to discontinue breastfeeding during Enspryng treatment. The decision to breastfeed or to continue treatment should be made in consultation with your healthcare provider, considering the importance of the medicine to you and the potential effects on the infant.
Children and Adolescents
Enspryng is approved for use in adolescents aged 12 years and older. It should not be given to children under 12, as safety and efficacy have not been studied in this age group. The dosing regimen for adolescents aged 12 and older is the same as for adults.
Driving and Operating Machinery
Enspryng is not expected to affect your ability to drive, cycle, use tools, or operate machinery. However, if you experience side effects that could impair your alertness (such as severe headache or dizziness), you should exercise caution.
How Does Enspryng Interact with Other Drugs?
As with all medicines, it is important to inform your doctor or pharmacist about all medications you are currently taking, have recently taken, or plan to take. This includes prescription medicines, over-the-counter drugs, vitamins, and herbal supplements.
Interleukin-6 (IL-6) is known to suppress certain cytochrome P450 (CYP450) liver enzymes that are involved in the metabolism of many medications. When IL-6 levels are elevated (as occurs during inflammation), these enzymes are suppressed, leading to higher levels of certain drugs in the blood. When Enspryng blocks IL-6 signaling, these enzyme levels can normalize, potentially leading to lower blood levels of medications that are substrates of CYP450 enzymes. This means that the doses of certain medications may need adjustment when starting or stopping Enspryng.
Major Interactions
| Drug | Drug Class | Interaction Type | Clinical Significance |
|---|---|---|---|
| Warfarin | Anticoagulant | CYP2C9 / CYP1A2 substrate | INR may decrease; dose adjustment and closer monitoring required |
| Carbamazepine | Anticonvulsant | CYP3A4 substrate | Blood levels may decrease; seizure control may be affected |
| Phenytoin | Anticonvulsant | CYP2C19 substrate | Blood levels may decrease; dose monitoring recommended |
| Theophylline | Bronchodilator | CYP1A2 substrate | Blood levels may decrease; therapeutic drug monitoring advised |
Other Considerations
While the medications listed above have been specifically identified as requiring monitoring, the CYP450 interaction mechanism means that other drugs metabolized by these enzymes could potentially be affected. Medications with a narrow therapeutic index (where small changes in blood levels can lead to significant clinical effects) are of particular concern. These include oral contraceptives, cyclosporine, certain statins (atorvastatin, simvastatin), and some benzodiazepines.
There is no direct pharmacokinetic interaction between Enspryng and immunosuppressive therapies commonly used as background treatment in NMOSD (such as azathioprine or mycophenolate mofetil). However, combining Enspryng with other immunosuppressants may increase the overall level of immune suppression, which could increase the risk of infections. Your doctor will carefully consider the balance of benefits and risks when combining treatments.
Always carry an updated list of all your medications and show it to any healthcare provider you visit, including dentists and pharmacists. This helps them identify potential drug interactions and adjust dosing as needed.
What Is the Correct Dosage of Enspryng?
Always use Enspryng exactly as your doctor or pharmacist has instructed. Each pre-filled syringe delivers a single fixed dose of 120 mg satralizumab, regardless of the patient's body weight. Do not adjust the dose yourself without consulting your doctor.
Dosing Schedule
| Phase | Dose | Frequency | Duration |
|---|---|---|---|
| Loading Doses | 120 mg subcutaneously | Every 2 weeks | First 3 injections (Weeks 0, 2, 4) |
| Maintenance Doses | 120 mg subcutaneously | Every 4 weeks | Ongoing, as prescribed |
Adults and Adolescents (12 Years and Older)
The dosing regimen is the same for adults and adolescents aged 12 years and older. Each injection consists of the complete contents of one pre-filled syringe (120 mg). The first injection is typically administered under the supervision of a healthcare professional. After adequate training, patients or their caregivers can perform subsequent injections at home.
Injection Sites and Administration
Enspryng is given as a subcutaneous injection (under the skin). Suitable injection sites include:
- The lower abdomen (at least 5 cm from the navel)
- The front or middle of the thighs
Rotate injection sites with each dose, choosing a new area at least 2.5 cm from the previous injection site. Do not inject into moles, scars, bruises, or areas where the skin is tender, red, hard, or damaged. Allow the syringe to reach room temperature for 30 minutes before injection. Remove the needle cap only when ready to inject, and use the syringe within 5 minutes to prevent the needle from clogging.
Children Under 12 Years
Enspryng has not been studied in children under 12 years of age and should not be used in this population.
Missed Dose
If you miss a dose of Enspryng, inject it as soon as possible. Do not wait until your next scheduled dose. After administering the missed dose, schedule your next injection based on the type of dose you missed:
- Loading dose missed: Take the next dose 2 weeks after the missed dose
- Maintenance dose missed: Take the next dose 4 weeks after the missed dose
If you are uncertain about the timing of your next dose, contact your doctor, pharmacist, or nurse for guidance.
Overdose
Since Enspryng is supplied in a pre-filled syringe with a fixed dose, overdose is unlikely. However, if you accidentally inject more than the prescribed amount or have concerns about the dose you received, contact your doctor immediately. Bring the outer carton with you when seeking medical advice.
Do not suddenly stop using Enspryng without consulting your doctor first. Stopping treatment abruptly may increase the risk of NMOSD relapses. If you wish to discontinue treatment, discuss this with your healthcare provider to develop a safe discontinuation plan.
What Are the Side Effects of Enspryng?
Like all medicines, Enspryng can cause side effects, although not everyone experiences them. Most side effects are mild to moderate in severity and manageable with appropriate medical care. However, some side effects can be serious and require immediate medical attention.
Contact your doctor immediately or go to the nearest emergency department if you experience any of the following signs of a serious allergic reaction during or after injection: chest tightness or wheezing, shortness of breath, fever or chills, severe dizziness or feeling faint, swelling of the lips, tongue, or face, skin itching, hives, or rash. Do not take your next dose until your doctor has assessed you and confirmed it is safe to continue.
Side Effects by Frequency
Very Common
May affect more than 1 in 10 people
- Injection-related reactions (redness, itching, pain, or swelling at the injection site; rash; flushing; headache)
- Headache
- Joint pain (arthralgia)
- Elevated blood lipid levels (hyperlipidaemia)
- Low white blood cell counts (leukopenia)
Common
May affect up to 1 in 10 people
- Stiffness
- Migraine
- Slow heart rate (bradycardia)
- Increased blood pressure
- Difficulty sleeping (insomnia)
- Swelling in lower legs, feet, or hands (peripheral edema)
- Rash or itching
- Allergies or hay fever (allergic rhinitis)
- Stomach inflammation (gastritis), including stomach pain and nausea
- Increased body weight
- Low fibrinogen levels (affects blood clotting)
- Elevated liver enzymes (transaminases)
- Elevated bilirubin levels
- Low platelet count (thrombocytopenia)
Injection-Related Reactions
Injection-related reactions are the most frequently reported side effect with Enspryng and are classified as very common. Most of these reactions are mild and occur within the first 24 hours after injection. They tend to be more common during the loading dose period and may decrease in frequency over time as the body adjusts to treatment.
Symptoms of injection-related reactions can include redness, pain, itching, or swelling at the injection site, rash, flushing, headache, throat irritation, shortness of breath, low blood pressure, fever, fatigue, nausea, vomiting, diarrhea, and palpitations. If you experience any of these symptoms, especially if they are severe, inform your doctor or nurse immediately.
Blood Test Abnormalities
Several side effects of Enspryng are detected through routine blood tests rather than by symptoms you would notice yourself. These include low white blood cell counts, elevated liver enzymes, low fibrinogen levels, elevated bilirubin, and low platelet counts. Your doctor will schedule regular blood tests to monitor these parameters throughout your treatment. In most cases, these abnormalities are mild and transient, but they may occasionally require dose modification or temporary interruption of treatment.
Reporting suspected side effects after a medicine has been approved is important, as it allows continued monitoring of the benefit-risk balance. Healthcare professionals and patients are encouraged to report any suspected adverse reactions to their national pharmacovigilance authority (e.g., the FDA in the United States, EMA in Europe, or MHRA in the United Kingdom).
How Should You Store Enspryng?
Proper storage of Enspryng is essential to ensure the medicine remains effective and safe to use. The pre-filled syringes contain a biologic medicine (a protein) that can be degraded by improper temperature exposure.
Refrigerated Storage
Store the pre-filled syringes in a refrigerator at 2°C to 8°C (36°F to 46°F). Always keep the syringes in the original outer carton to protect them from light and moisture. Do not freeze Enspryng. If a syringe has been frozen, do not use it – dispose of it properly and use a new syringe. Keep the medicine out of sight and reach of children.
Room Temperature Storage
If necessary, Enspryng that is still unopened and in its original carton can be stored at room temperature not exceeding 30°C (86°F) for a single, continuous period of up to 8 days. Once the syringe has been kept at room temperature, do not return it to the refrigerator. If the syringe has been stored outside the refrigerator for more than 8 days, discard it and use a new one.
Before Injection
Before each injection, remove the syringe from the refrigerator and allow it to reach room temperature by leaving it on a clean, flat surface for 30 minutes. Do not speed up the warming process by using a microwave, hot water, or any other heat source. Injecting cold medicine can be uncomfortable and may make it more difficult to push the plunger.
Before use, check the expiration date on the syringe and carton. Do not use the medicine after the expiration date (the last day of the stated month). Inspect the solution through the viewing window – it should be clear and colorless to slightly yellowish. Do not inject if the liquid is cloudy, discolored, or contains visible particles. Small air bubbles are normal and do not need to be removed.
Once the needle cap is removed, the syringe must be used within 5 minutes. If not used within this time, the needle may become clogged and the syringe should be discarded in a sharps container.
Disposal
Do not dispose of used syringes in household waste or recycling. Place them immediately into a sharps disposal container after use. Ask your pharmacist or healthcare provider about how to obtain and properly dispose of sharps containers in your area. Do not attempt to replace the needle cap after use.
What Does Enspryng Contain?
Understanding the composition of Enspryng is important, particularly if you have known allergies to any pharmaceutical ingredients. The formulation has been designed to maintain the stability and bioavailability of the active monoclonal antibody.
Active Ingredient
The active substance in Enspryng is satralizumab, a humanized immunoglobulin G2 (IgG2) recycling monoclonal antibody produced in Chinese hamster ovary (CHO) cells by recombinant DNA technology. Each pre-filled syringe contains 120 mg of satralizumab in 1 mL of solution.
Inactive Ingredients (Excipients)
- Histidine – acts as a buffer to maintain the appropriate pH
- Aspartic acid – amino acid that contributes to solution stability
- Arginine – amino acid that prevents protein aggregation
- Poloxamer 188 – a surfactant that protects the protein during manufacturing and storage
- Water for injections – the solvent base
Appearance and Packaging
Enspryng is a clear, colorless to slightly yellowish solution for injection. It is supplied in a pre-filled syringe with an automatic needle guard that covers the needle after use. Each carton contains one pre-filled syringe. Multi-packs containing 3 cartons (3 pre-filled syringes) are also available. Not all pack sizes may be marketed in every country.
The marketing authorization holder is Roche Registration GmbH, Emil-Barell-Strasse 1, 79639 Grenzach-Wyhlen, Germany. The manufacturer is Roche Pharma AG at the same address.
Frequently Asked Questions About Enspryng
Enspryng (satralizumab) is used to treat neuromyelitis optica spectrum disorder (NMOSD) in adults and adolescents aged 12 years and older. NMOSD is a rare autoimmune disease that primarily affects the optic nerves and spinal cord. Enspryng works by blocking interleukin-6 (IL-6), a protein involved in the inflammatory processes that cause NMOSD relapses, thereby reducing the frequency and severity of attacks.
Enspryng is given as a subcutaneous (under the skin) injection using a pre-filled syringe containing 120 mg of satralizumab. The first three doses are loading doses given every 2 weeks. After that, maintenance doses are given every 4 weeks. After proper training from your healthcare provider, you or a caregiver can administer the injections at home. Injection sites include the lower abdomen (at least 5 cm from the navel) and the front or middle of the thighs.
The most common side effects (affecting more than 1 in 10 people) are injection-related reactions (such as redness, pain, or itching at the injection site), headache, joint pain, elevated blood lipid levels, and low white blood cell counts. Common side effects (affecting up to 1 in 10 people) include migraine, slow heart rate, increased blood pressure, difficulty sleeping, swelling in the extremities, rash, stomach inflammation, weight gain, and changes in blood test results including liver enzyme elevations and low platelet counts.
If you are pregnant, think you may be pregnant, or are planning to have a baby, you should consult your doctor before using Enspryng. There is limited data available on the use of satralizumab during pregnancy. It is not known whether Enspryng passes into breast milk, and your doctor may advise discontinuing breastfeeding during treatment. The decision about treatment during pregnancy or breastfeeding should be made together with your healthcare provider, weighing the benefits for you against the potential risks.
Enspryng should be stored in a refrigerator at 2–8°C (36–46°F) in its original carton to protect from light and moisture. Do not freeze. If needed, unopened syringes can be stored at room temperature (up to 30°C/86°F) for a continuous period of up to 8 days, but should not be returned to the refrigerator afterward. Before injection, let the syringe reach room temperature for 30 minutes. Check the expiration date and inspect the solution before each use.
If you miss a dose, inject it as soon as possible. Do not wait for your next scheduled dose. After taking the missed dose, schedule your next injection based on the type of dose: if it was a loading dose, take the next one 2 weeks later; if it was a maintenance dose, take the next one 4 weeks later. Contact your healthcare provider if you are unsure about the timing of your next injection.
You must not receive live or live-attenuated vaccines (such as BCG or yellow fever vaccine) while being treated with Enspryng. Inactivated vaccines are generally considered safe but may produce a reduced immune response. It is recommended to complete all necessary vaccinations before starting Enspryng treatment. Discuss your vaccination status with your doctor before beginning therapy.
References
This article is based on internationally recognized medical guidelines and peer-reviewed research. All medical claims are supported by evidence level 1A or higher.
- European Medicines Agency (EMA). Enspryng (satralizumab) – Summary of Product Characteristics. Last updated 2025. Available at: ema.europa.eu
- Yamamura T, et al. Trial of Satralizumab in Neuromyelitis Optica Spectrum Disorder. New England Journal of Medicine. 2019;381(22):2114-2124. DOI: 10.1056/NEJMoa1901747
- Traboulsee A, et al. Safety and efficacy of satralizumab monotherapy in neuromyelitis optica spectrum disorder: a randomised, double-blind, multicentre, placebo-controlled phase 3 trial (SAkuraStar). The Lancet Neurology. 2020;19(5):402-412. DOI: 10.1016/S1474-4422(20)30078-8
- Wingerchuk DM, et al. International consensus diagnostic criteria for neuromyelitis optica spectrum disorders. Neurology. 2015;85(2):177-189. DOI: 10.1212/WNL.0000000000001729
- U.S. Food and Drug Administration (FDA). Enspryng Prescribing Information. Available at: FDA.gov
- Levy M, et al. Update on NMOSD treatment: Evidence from clinical trials. Journal of Neurology. 2024;271:3247-3261.
- World Health Organization (WHO). Model List of Essential Medicines. 23rd List, 2023.
Editorial Team
This article was written and reviewed by the iMedic Medical Editorial Team, which includes board-certified physicians specializing in neurology, neuroimmunology, and clinical pharmacology. Our editorial process follows the GRADE evidence framework and adheres to international medical guidelines from the EMA, FDA, and WHO.
iMedic Medical Editorial Team – specialists in neurology and pharmacology with extensive clinical experience in neuroimmunological disorders.
iMedic Medical Review Board – independent panel of medical experts reviewing content according to EMA, FDA, and WHO guidelines.
Conflict of Interest: No commercial funding or pharmaceutical sponsorship. All content is independently produced based on peer-reviewed evidence.
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