Gamifant (emapalumab)
An approved treatment for Systemic Juvenile Idiopathic Arthritis.
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, achieving MAS remission in 82% of patients.
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.
Mechanism: Fully human monoclonal antibody that binds and neutralizes interferon-gamma (IFNγ), halting the hyperactivated macrophage response that drives macrophage activation syndrome
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 6 mg/kg, followed by 3 mg/kg every 3 days for 5 doses, then 3 mg/kg twice a week. Doses can be raised up to 10 mg/kg based on clinical response and lab results. (The 1 mg/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
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.
- 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.
- From a charity · The Assistance FundJuvenile Arthritis fundWaitlist
Pays for: Copays, coinsurance, deductibles and other health-related expenses.
The foundation says: “WAITLIST — Accepting Waitlist Patients. TAF is currently accepting requests to join the enrollment waitlist for this program. Waitlists a…”
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, achieving MAS remission in 82% of patients.
▸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 6 mg/kg, followed by 3 mg/kg every 3 days for 5 doses, then 3 mg/kg twice a week. Doses can be raised up to 10 mg/kg based on clinical response and lab results. (The 1 mg/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 (2025) 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.
▸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 trials, 82% of patients achieved MAS remission.
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