Gamifant (emapalumab)
An approved treatment for Systemic Juvenile Idiopathic Arthritis.
Drug facts
The same compound appears under different names depending on the context. Here is how to identify Emapalumab wherever you encounter it, plus the key facts at a glance.
- Generic name
- Emapalumab
- Brand name
- Gamifant
- Development code
- NI-0501
- Drug class
- Anti-interferon-gamma antibody
- Manufacturer
- Sobi (Swedish Orphan Biovitrum)
- How it's taken
- Given as an intravenous infusion over 1 hour.
The first and only FDA-approved treatment for macrophage activation syndrome (MAS) in Still's disease, including sJIA-associated MAS.
- Emapalumab blocks interferon-gamma, the cytokine that drives the life-threatening immune hyperactivation in MAS.
- In the 2 studies behind the approval, 21 of 39 patients (54%) reached complete response, the main measure, by week 8, and 82% had their MAS signs resolve clinically.
We'll email you when Gamifant's FDA label changes, when the FDA acts on it, and when new trials for Systemic Juvenile Idiopathic Arthritis open. Unsubscribe anytime.
- Trial Alerts, when a new trial opens or a trial changes
- Disease Updates, FDA decisions and condition news, usually 1 or 2 emails a month
We never share your email. Unsubscribe anytime. Privacy policy · Check any health site
Where Emapalumab fits
The only FDA-approved treatment for macrophage activation syndrome in Still's disease (sJIA and adult-onset Still's disease).
- Represents a paradigm shift from non-specific immunosuppression (high-dose steroids, etoposide) to targeted therapy addressing the specific cytokine (IFNγ) that drives MAS pathology.
- Reserved for MAS episodes rather than routine sJIA management, which is typically treated with canakinumab (Ilaris), tocilizumab (Actemra), or anakinra (Kineret).
How Emapalumab works
Macrophage activation syndrome is a life-threatening complication of systemic JIA in which the immune system spirals out of control. Macrophages and T cells become hyperactivated and begin attacking the body's own organs, potentially causing multi-organ failure. The master signal driving this hyperactivation is interferon-gamma (IFNγ).
Emapalumab is an antibody that grabs every IFNγ molecule it encounters in the bloodstream, neutralizing them before they can activate macrophages. With IFNγ blocked, macrophages stop their destructive overactivation, cytokine levels normalize, and the inflammatory cascade halts.
In clinical trials, 82% of patients achieved clinical MAS remission at 8 weeks. This is a remarkable result given that MAS carries mortality rates of 8-25% even with conventional treatment. Emapalumab provides the first therapy that directly addresses the underlying mechanism of MAS rather than relying on broad immunosuppression.
Side effects and safety
Because emapalumab suppresses IFNγ (which plays an important role in fighting infections), serious and even fatal infections are the main risk, especially tuberculosis and other mycobacterial infections, shingles (herpes zoster), and histoplasmosis. Patients are tested for latent tuberculosis before starting and are watched for CMV and other viral infections during treatment.
Doctors may also give medicines to prevent shingles, Pneumocystis pneumonia, and fungal infections. Live vaccines should not be given during treatment or for at least 4 weeks after the last dose. In the Still's disease MAS studies, the most common side effects were viral infections (44%), including CMV infection or reactivation (36%), and rash (21%).
Anemia, low white cell counts, blood clots, headache, high blood sugar, and infusion reactions were also seen. Serious side effects occurred in 31% of these patients.
This is not a complete list of side effects. Talk to your doctor or pharmacist about what to expect and when to seek medical attention.
Taking Emapalumab
Given as an intravenous infusion over 1 hour. For MAS in Still's disease, the first dose is 6mg/kg, followed by 3mg/kg every 3 days for 5 doses, then 3mg/kg twice a week. Doses can be raised up to 10mg/kg based on clinical response and lab results. (The 1mg/kg starting dose is for primary HLH.) Treatment continues until MAS remission is achieved, then tapered.
Availability and cost
Only available as the brand-name product.
Help paying for Gamifant
The maker of Gamifant publishes no copay card, but its support program can check your insurance and explain any help that exists. Drugmaker copay cards can't be used with Medicare, Medicaid or TRICARE, but charity funds often can. The charity fund for Systemic Juvenile Idiopathic Arthritis was not taking new applications on November 13, 2026. Pick your insurance below to see which offers fit you.
- Insurance and case manager help
Benefits investigation, prior authorization and appeal support, specialty pharmacy coordination, and help finding financial assistance.
The official page does not say who qualifies. Ask the program. · source - Copay help
Gamifant Copay Assistance Program exists; eligibility checked through Gamifant Cares. Terms not stated on the page.
The official page does not say who qualifies. Ask the program. · source - Free medicine program
Gamifant Patient Assistance Program exists; eligibility checked through Gamifant Cares. Criteria not stated on the page.
The official page does not say who qualifies. Ask the program. · source
Good to know: Official pages name the copay and patient assistance programs but do not say who qualifies or dollar amounts. Call Gamifant Cares for details.
Charity funds for Systemic Juvenile Idiopathic Arthritis
- From a charity · The Assistance FundJuvenile Arthritis fundWaitlist
Pays for: Copays, coinsurance, deductibles and other health-related expenses.
Every program and charity fund for Systemic Juvenile Idiopathic Arthritis →
Emapalumab treatment timeline for Systemic Juvenile Idiopathic Arthritis (MAS)
Tap how long you have been on Emapalumab to drop your pin on the road. Your answers stay on this device.
Stage 1 of 5 · Start to 1 mo
Acute MAS treatment
Your child is receiving emapalumab (Gamifant) for macrophage activation syndrome, a life-threatening complication of systemic JIA where the immune system becomes dangerously overactivated. MAS causes the body to attack its own organs, leading to high fevers, organ damage, blood clotting problems, and potentially multi-organ failure. Emapalumab was the first FDA-approved treatment for MAS in Still's disease, for use when steroids have not worked well enough, are not tolerated, or MAS returns. It works by blocking interferon-gamma, the key signal driving the runaway macrophage activation. Your child is likely in the hospital during this phase, receiving the infusion along with supportive care. How long your child stays in the hospital depends on how sick they are and how fast MAS responds. The first dose is 6mg/kg, then 3mg/kg every 3 days for 5 doses, then 3mg/kg twice a week. The team may raise the dose based on response. Before the first dose, the team tests for tuberculosis. They may also give medicines to help prevent shingles, a type of pneumonia and fungal infections.
Coming up
Your child's medical team is monitoring lab values intensively, often daily or even more frequently during the acute phase. The key markers they are tracking include: ferritin (should start dropping as MAS responds), blood counts (platelets and white cells should begin recovering), liver enzymes (should start improving), fibrinogen (should normalize), and overall clinical status. In the 2 studies behind the approval, 82% of patients reached clinical MAS remission by week 8, judged on a doctor's 0-10 score. A complete response, meaning remission plus 7 lab targets for blood counts, liver tests, fibrinogen and ferritin, was seen in 54% at week 8. Once MAS is controlled and your child is clinically stable, the transition from crisis management to recovery begins. Your child should not get live vaccines during treatment or for at least 4 weeks after the last dose. Because MAS is triggered by the underlying sJIA, a plan for long-term sJIA management (to prevent future MAS episodes) is developed simultaneously.
Get in touch with your rheumatology team if you notice
- Ferritin not declining or continuing to rise despite emapalumab treatment (may need dose escalation or additional therapy)
- New organ failure: kidney function worsening, liver failure, respiratory failure, or DIC (disseminated intravascular coagulation)
- CMV reactivation or other serious infection: alert your medical team immediately. CMV symptoms include persistent low-grade fever, fatigue, diarrhea, or visual changes. Your team checks for CMV and other viruses as needed. (Emapalumab blocks interferon-gamma, which helps fight viral infections, so the label advises watching for these viruses.)
- Severe infusion reaction
- Neurological symptoms: confusion, seizures, or altered consciousness (CNS involvement in MAS is a serious sign)
- Is my child's MAS responding to emapalumab? What are the ferritin and blood count trends?
- How long will my child need to stay in the hospital?
- Is there a risk that the MAS could come back even while on emapalumab?
- Since emapalumab blocks interferon-gamma (an infection-fighting protein), how are you monitoring for infections?
- What caused this MAS episode: was it a sJIA flare, an infection trigger, or something else?
- What is the plan for preventing future MAS episodes once this one is treated?
Every stage of Emapalumab treatment at a glance
Acute MAS treatment Start to 1 mo
Your child is receiving emapalumab (Gamifant) for macrophage activation syndrome, a life-threatening complication of systemic JIA where the immune system becomes dangerously overactivated. MAS causes the body to attack its own organs, leading to high fevers, organ damage, blood clotting problems, and potentially multi-organ failure. Emapalumab was the first FDA-approved treatment for MAS in Still's disease, for use when steroids have not worked well enough, are not tolerated, or MAS returns. It works by blocking interferon-gamma, the key signal driving the runaway macrophage activation. Your child is likely in the hospital during this phase, receiving the infusion along with supportive care. How long your child stays in the hospital depends on how sick they are and how fast MAS responds. The first dose is 6mg/kg, then 3mg/kg every 3 days for 5 doses, then 3mg/kg twice a week. The team may raise the dose based on response. Before the first dose, the team tests for tuberculosis. They may also give medicines to help prevent shingles, a type of pneumonia and fungal infections.
Your child's medical team is monitoring lab values intensively, often daily or even more frequently during the acute phase. The key markers they are tracking include: ferritin (should start dropping as MAS responds), blood counts (platelets and white cells should begin recovering), liver enzymes (should start improving), fibrinogen (should normalize), and overall clinical status. In the 2 studies behind the approval, 82% of patients reached clinical MAS remission by week 8, judged on a doctor's 0-10 score. A complete response, meaning remission plus 7 lab targets for blood counts, liver tests, fibrinogen and ferritin, was seen in 54% at week 8. Once MAS is controlled and your child is clinically stable, the transition from crisis management to recovery begins. Your child should not get live vaccines during treatment or for at least 4 weeks after the last dose. Because MAS is triggered by the underlying sJIA, a plan for long-term sJIA management (to prevent future MAS episodes) is developed simultaneously.
MAS recovery and stabilization 1 mo to 3 mo
Your child's MAS has responded to emapalumab and the acute crisis has passed. The focus now is on two things: continuing emapalumab until the team decides it is no longer needed, and establishing or reestablishing effective sJIA treatment to prevent future episodes. Your child is likely recovering from the physical toll of MAS, which can include prolonged fatigue, weakness, and slow recovery of blood counts and liver function. Lab values are being monitored frequently (usually weekly or biweekly) to confirm continued improvement and watch for relapse. Your child may still be receiving emapalumab infusions, and the team will stop them once your child no longer needs this treatment for MAS.
Once emapalumab is discontinued, your child will need to be on a robust sJIA maintenance therapy to prevent future MAS episodes. The rheumatologist will likely recommend an IL-1 or IL-6 blocker for ongoing sJIA care. Canakinumab (Ilaris) and tocilizumab (Actemra) are FDA approved for sJIA. Anakinra (Kineret) is widely used for sJIA but is not FDA approved for it in the US. The choice depends on what your child was on before the MAS episode and whether that therapy was adequate. Some children develop MAS as their initial sJIA presentation, while others have a MAS episode despite being on biologic therapy. In the latter case, your rheumatologist may change the biologic approach. Lab monitoring remains frequent during this transition period.
Post-MAS management 3 mo to 6 mo
Your child is 3-6 months out from the acute MAS episode. Emapalumab has likely been discontinued, and your child is now on maintenance sJIA therapy (an IL-1 or IL-6 inhibitor). The scars of MAS, both physical and emotional, are still present. Physically, your child may still be regaining strength and stamina. Emotionally, both you and your child may be dealing with the trauma of a life-threatening hospitalization. Lab monitoring continues regularly but less frequently than during the acute phase, typically every 2-4 weeks. Your child's rheumatologist is watching closely for any early signs of MAS recurrence.
If your child's sJIA is well-controlled on the current maintenance biologic and there are no signs of MAS recurrence, the plan is to continue this regimen and gradually normalize your child's life. Return to school, activities, and social engagement are important recovery milestones. The rheumatologist will continue monitoring labs and adjusting treatment as needed. MAS recurrence risk is real but decreases over time as sJIA is well-controlled. The experience of MAS may change how aggressively your rheumatologist manages the underlying sJIA going forward.
Long-term MAS prevention 6 mo to 18 mo
Your child is now several months out from the MAS episode and hopefully stabilized on effective sJIA maintenance therapy. The acute crisis is behind you, but the experience has fundamentally shaped your child's treatment plan. Your rheumatologist is likely managing the sJIA more aggressively than they might in a child who had never experienced MAS. Lab monitoring continues at regular intervals, with particular attention to ferritin trends, blood counts, and liver enzymes as early warning markers.
Ongoing vigilance for MAS is part of long-term sJIA management after a MAS episode. Your rheumatologist may recommend periodic ferritin checks even when your child feels well, as rising ferritin can be an early signal. If the sJIA remains well-controlled and there are no MAS recurrences, the treatment approach may gradually become less intensive. However, any decisions about tapering biologics will be made very cautiously given the MAS history.
Long-term survivorship 18 mo on
Your child is more than a year and a half past the MAS episode and in the long-term survivorship phase. Emapalumab served its purpose during the acute crisis, and your child's ongoing management is now handled by the maintenance sJIA biologic. The MAS experience remains an important part of your child's medical history and influences treatment decisions, but daily life should be increasingly normal.
Long-term care continues with periodic rheumatology visits, lab monitoring, and age-appropriate health screening. As your child grows, transition planning to adult rheumatology care becomes relevant. The history of MAS should always be communicated to any new providers, as it affects future treatment decisions, anesthesia considerations, and infection management. Research into MAS continues to advance, and newer preventive strategies may become available.
This timeline shows typical patterns from the prescribing information, guidelines and published studies. Your own treatment may differ, and your rheumatology team is the source of truth for your plan. Last checked against the FDA label on .
Clinical trial results
The pivotal evidence came from the Phase 3 EMERALD trial and Phase 2 NI-0501-06 trial in patients with HLH/MAS associated with Still's disease. In pooled analysis (39 patients), 53.8% achieved complete response at week 8 (resolution of all MAS clinical signs and normalization of laboratory parameters). Clinical MAS remission (the broader measure) was achieved in 82% of patients. These results were transformative for a condition with limited prior treatment options.
Development history
Emapalumab (NI-0501) was developed by Novimmune, a Swiss biotech focused on IFNγ biology. Sobi acquired the program in 2019. The FDA first approved emapalumab in November 2018 for primary hemophagocytic lymphohistiocytosis (HLH). Based on the EMERALD trial data, FDA expanded the approval in June 2025 to include MAS in Still's disease (including sJIA-associated MAS), making it the first and only approved treatment specifically for this life-threatening complication.
Explore Systemic Juvenile Idiopathic Arthritis trials
Other Systemic Juvenile Idiopathic Arthritis treatments
Common questions about Emapalumab
▸What is Emapalumab (Gamifant)?
The first and only FDA-approved treatment for macrophage activation syndrome (MAS) in Still's disease, including sJIA-associated MAS. Emapalumab blocks interferon-gamma, the cytokine that drives the life-threatening immune hyperactivation in MAS. In the 2 studies behind the approval, 21 of 39 patients (54%) reached complete response, the main measure, by week 8, and 82% had their MAS signs resolve clinically.
▸How does Emapalumab work?
Macrophage activation syndrome is a life-threatening complication of systemic JIA in which the immune system spirals out of control. Macrophages and T cells become hyperactivated and begin attacking the body's own organs, potentially causing multi-organ failure. The master signal driving this hyperactivation is interferon-gamma (IFNγ).
Emapalumab is an antibody that grabs every IFNγ molecule it encounters in the bloodstream, neutralizing them before they can activate macrophages. With IFNγ blocked, macrophages stop their destructive overactivation, cytokine levels normalize, and the inflammatory cascade halts.
In clinical trials, 82% of patients achieved clinical MAS remission at 8 weeks. This is a remarkable result given that MAS carries mortality rates of 8-25% even with conventional treatment. Emapalumab provides the first therapy that directly addresses the underlying mechanism of MAS rather than relying on broad immunosuppression.
▸What are the side effects of Emapalumab?
Because emapalumab suppresses IFNγ (which plays an important role in fighting infections), serious and even fatal infections are the main risk, especially tuberculosis and other mycobacterial infections, shingles (herpes zoster), and histoplasmosis. Patients are tested for latent tuberculosis before starting and are watched for CMV and other viral infections during treatment. Doctors may also give medicines to prevent shingles, Pneumocystis pneumonia, and fungal infections. Live vaccines should not be given during treatment or for at least 4 weeks after the last dose. In the Still's disease MAS studies, the most common side effects were viral infections (44%), including CMV infection or reactivation (36%), and rash (21%). Anemia, low white cell counts, blood clots, headache, high blood sugar, and infusion reactions were also seen. Serious side effects occurred in 31% of these patients.
▸How is Emapalumab taken?
Given as an intravenous infusion over 1 hour. For MAS in Still's disease, the first dose is 6mg/kg, followed by 3mg/kg every 3 days for 5 doses, then 3mg/kg twice a week. Doses can be raised up to 10mg/kg based on clinical response and lab results. (The 1mg/kg starting dose is for primary HLH.) Treatment continues until MAS remission is achieved, then tapered.
▸Is Emapalumab FDA approved?
Yes, Emapalumab (Gamifant) is FDA approved (2018) for the treatment of Systemic Juvenile Idiopathic Arthritis.
▸What is Gamifant approved for?
Gamifant (emapalumab) was approved in June 2025 as the first FDA-approved treatment for adults and children with macrophage activation syndrome (MAS, also called HLH/MAS) in known or suspected Still's disease, including sJIA. It is approved when MAS has not responded well enough to glucocorticoids (steroids), when steroids are not tolerated, or when MAS keeps coming back. It is not a treatment for sJIA itself. Gamifant has also been approved since 2018 for primary HLH that is refractory, recurrent, or progressive, or when standard HLH therapy is not tolerated. [1][2]
▸How does emapalumab treat macrophage activation syndrome?
Emapalumab blocks interferon-gamma, the master signal that drives macrophage hyperactivation in MAS. By neutralizing this signal, it halts the life-threatening immune cascade that causes multi-organ failure. In the pooled analysis of the Phase 3 EMERALD and Phase 2 NI-0501-06 trials (39 patients), 82% achieved clinical MAS remission and 53.8% achieved complete response at week 8. [3]
▸How is Gamifant given for MAS?
Gamifant (emapalumab) is given as an intravenous infusion over 1 hour. For MAS in Still's disease, the first dose is 6mg/kg, followed by 3mg/kg every 3 days for 5 doses, then 3mg/kg twice a week, and doses can be raised up to 10mg/kg based on clinical response and lab results. Treatment continues until MAS remission is achieved and is then tapered. [2]
▸What are the side effects of emapalumab?
Because emapalumab (Gamifant) blocks interferon-gamma, which helps the body fight infections, serious and even fatal infections are the main risk, especially tuberculosis and other mycobacterial infections, shingles, and histoplasmosis. In the Still's disease MAS studies, the most common side effects were viral infections (44%), including CMV infection or reactivation (36%), and rash (21%), and serious side effects occurred in 31% of patients. Patients are tested for latent tuberculosis before starting, may receive medicines to prevent shingles, Pneumocystis pneumonia, and fungal infections, and should not get live vaccines during treatment or for at least 4 weeks after the last dose. [2]
Sources and references
Every factual claim on this page is drawn from the public sources listed below. Click any reference to open the original document.
- Sobi · June 2025. FDA Approves Gamifant (emapalumab-lzsg) as First-Ever Treatment for MAS in Still's Disease. https://www.sobi.com/en/press-releases/fda-approves-gamifantr-emapalumab-lzsg-first-ever-treatment-adults-and-children-macrophage-activation-syndrome-stills-disease-2342991
- U.S. Food and Drug Administration. GAMIFANT (emapalumab-lzsg) Label. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=a865e0ef-8685-4f69-8838-648c4f3bab47
- ClinicalTrials.gov. Efficacy and Safety of Emapalumab in MAS. https://clinicaltrials.gov/study/NCT05001737