GAMIFANT

RECENT MAJOR CHANGES Indications and Usage ( 1 ) 6/2025 Dosage and Administration ( 2.2 , 2.3 ) 6/2025 Warnings and Precautions ( 5.1 , 5.3 ) 03/2026

1 INDICATIONS AND USAGE GAMIFANT is indicated for the treatment of: adult and pediatric patients with primary hemophagocytic lymphohistiocytosis (HLH) with refractory, recurrent or progressive disease or intolerance with conventional HLH therapy. adult and pediatric patients with HLH/macrophage activation syndrome (MAS) in known or suspected Still’s disease, including systemic Juvenile Idiopathic Arthritis (sJIA), with an inadequate response or intolerance to glucocorticoids, or with recurrent MAS. GAMIFANT is an interferon gamma (IFNγ) neutralizing antibody indicated for the treatment of: adult and pediatric patients with primary hemophagocytic lymphohistiocytosis (HLH) with refractory, recurrent or progressive disease or intolerance with conventional HLH therapy. ( 1 ) adult and pediatric patients with HLH/macrophage activation syndrome (MAS) in known or suspected Still’s disease, including systemic Juvenile Idiopathic Arthritis (sJIA), with an inadequate response or intolerance to glucocorticoids, or with recurrent MAS. ( 1 )

2 DOSAGE AND ADMINISTRATION For intravenous infusion only: Primary HLH recommended starting dosage: 1 mg/kg as an intravenous infusion over 1 hour twice per week. ( 2.1 ) HLH/MAS in Still’s disease recommended dosage schedule: 6 mg/kg, followed by 3 mg/kg every 3 days for 5 doses, then 3 mg/kg twice per week. Given as an intravenous infusion over 1 hour. ( 2.2 ) For both indications, the dose may be titrated up to a maximum of 10 mg/kg. ( 2.5 , 2.6 ) 2.1 Recommended Dosage for Primary Hemophagocytic Lymphohistiocytosis The recommended starting dose of GAMIFANT is 1 mg/kg given as a central or peripheral intravenous infusion over 1 hour twice per week (every three to four days). Doses subsequent to the initial dose may be increased based on clinical and laboratory criteria [see Dosage and Administration ( 2.5 )] . Administer GAMIFANT until hematopoietic stem cell transplantation (HSCT) is performed or unacceptable toxicity. Discontinue GAMIFANT when a patient no longer requires therapy for the treatment of HLH. 2.2 Recommended Dosage for Hemophagocytic Lymphohistiocytosis/Macrophage Activation Syndrome GAMIFANT is administered as a central or peripheral intravenous infusion over 1 hour according to the dosage schedule in Table 1. Doses may be increased based on clinical and laboratory criteria [see Dosage and Administration ( 2.6 )] . Discontinue GAMIFANT when a patient no longer requires therapy for the treatment of HLH/MAS. Table 1. GAMIFANT Dosage in Patients with HLH/MAS Treatment Day GAMIFANT Dosage Day 1 6 mg/kg Days 4 to 16 3 mg/kg every 3 days for 5 doses From Day 19 onward 3 mg/kg twice per week (i.e., every 3 to 4 days) 2.3 Monitoring to Assess Safety Before Initiating GAMIFANT Treatment Conduct testing for latent tuberculosis infections using the purified protein derivative (PPD) or IFNγ release assay and evaluate patients for tuberculosis risk factors prior to initiating GAMIFANT. Administer tuberculosis prophylaxis to patients at risk for tuberculosis, or known to have a positive PPD test result, or positive IFNγ release assay. During GAMIFANT Treatment Monitor for herpes zoster infection, adenovirus, EBV and CMV as clinically indicated. 2.4 Prophylaxis and Concomitant Medication Information Prophylaxis Consider prophylaxis for herpes zoster, Pneumocystis jirovecii , and for fungal infections prior to GAMIFANT administration. Concomitant Medications For primary HLH patients who are not receiving baseline dexamethasone treatment, begin dexamethasone at a daily dose of at least 5 mg/m 2 to 10 mg/m 2 the day before GAMIFANT treatment begins. For patients who were receiving baseline dexamethasone, they may continue their regular dose provided the dose is at least 5 mg/m2. Dexamethasone can be tapered according to the judgment of the treating physician [see Clinical Studies ( 14 )] . 2.5 Dose Modification Based on Response for Primary Hemophagocytic Lymphohistiocytosis The GAMIFANT dose may be titrated up if disease response is unsatisfactory (see Table 2) [see Clinical Pharmacology ( 12.3 )] . After the patient's clinical condition is stabilized, decrease the dose to the previous level to maintain clinical response. Table 2: Dose Titration Criteria Treatment Day GAMIFANT Dose Criteria for Dose Increase Day 1 Starting Dose of 1 mg/kg N/A From Day 4 onwards Increase to 3 mg/kg Unsatisfactory improvement in clinical condition, as assessed by a healthcare provider AND at least one of the following: Fever - persistence or recurrence Platelet count If baseline 50,000/mm 3 If baseline > 50,000/mm 3 and less than 30% improvement If baseline > 100,000/mm 3 and decrease to 500/mm 3 If baseline > 500/mm 3 to 1,000/mm 3 and decrease to 3,000 ng/mL Splenomegaly - any worsening Coagulopathy (both D-Dimer and Fibrinogen must apply) D-Dimer If abnormal at baseline and no improvement Fibrinogen (mg/dL) If baseline levels ≤100 mg/dL and no improvement If baseline levels > 100 mg/dL and any decrease to < 100 mg/dL From Day 7 onwards Incr …

3 DOSAGE FORMS AND STRENGTHS GAMIFANT is a clear to slightly opalescent, colorless to slightly yellow preservative-free solution available as: Injection: • 10 mg/2 mL (5 mg/mL) in a single-dose vial • 50 mg/10 mL (5 mg/mL) in a single-dose vial • 100 mg/20 mL (5 mg/mL) in a single-dose vial • 50 mg/2 mL (25 mg/mL) in a single-dose vial • 100 mg/4 mL (25 mg/mL) in a single-dose vial • 250 mg/10 mL (25 mg/mL) in a single-dose vial • 500 mg/20 mL (25 mg/mL) in a single-dose vial Injection: • 10 mg/2 mL (5 mg/mL) solution in a single-dose vial ( 3 ) • 50 mg/10 mL (5 mg/mL) solution in a single-dose vial ( 3 ) • 100 mg/20 mL (5 mg/mL) solution in a single-dose vial ( 3 ) • 50 mg/2 mL (25 mg/mL) solution in a single-dose vial ( 3 ) • 100 mg/4 mL (25 mg/mL) solution in a single-dose vial ( 3 ) • 250 mg/10 mL (25 mg/mL) solution in a single-dose vial ( 3 ) • 500 mg/20 mL (25 mg/mL) solution in a single-dose vial ( 3 )

4 CONTRAINDICATIONS None. None. ( 4 )

6 ADVERSE REACTIONS The following adverse reactions are described elsewhere in the labeling: Infections [see Warnings and Precautions ( 5.1 )] Increased Risk of Infection with Use of Live Vaccines [see Warnings and Precautions ( 5.2 )] Infusion-Related Reactions [see Warnings and Precautions ( 5.3 )] In patients with primary HLH, the most common adverse reactions (≥ 20%) were: infections, hypertension, infusion-related reactions, and pyrexia. ( 6.1 ) In patients with HLH/MAS in Still’s disease, the most common adverse reactions (≥20%) were: viral infections, including cytomegalovirus infection or reactivation, and rash. ( 6.1 ) To report SUSPECTED ADVERSE REACTIONS, contact 1-866-773-5274 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch. 6.1 Clinical Trial Experience Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice. Primary HLH The safety data described in this section reflect exposure to GAMIFANT in which 34 patients with untreated primary HLH and previously treated patients with primary HLH ( NCT01818492 ) received GAMIFANT at a starting dose of 1 mg/kg every 3 days with dose increases up to 10 mg/kg [see Dosage and Administration ( 2.1 ) and Clinical Studies ( 14 )] . The median duration of treatment with GAMIFANT was 59 days (range: 4 to 245 days) and the median cumulative dose was 25 mg/kg (range: 4 to 254 mg/kg). The median age of study population was 1 year (range: 0.1 to 13 years), 53% were female, and 65% were Caucasian. Serious adverse reactions were reported in 53% of patients. The most common serious adverse reactions (≥3%) included infections, gastrointestinal hemorrhage, and multiple organ dysfunction. Fatal adverse reactions occurred in two (6%) of patients and included septic shock and gastrointestinal hemorrhage. Disseminated histoplasmosis led to drug discontinuation in one patient. The most commonly reported adverse reactions (≥20%) were infections, hypertension, infusion-related reactions, and pyrexia. Adverse reactions reported in ≥10% of patients during treatment with GAMIFANT are presented in Table 4. Table 4 : Adverse Reactions Reported in 10% of Patients with Primary HLH Adverse Reactions GAMIFANT (%) (N = 34) Infections a 56 Hypertension b 41 Infusion-related reactions c 27 Pyrexia 24 Hypokalemia 15 Constipation 15 Rash 12 Abdominal pain 12 Cytomegalovirus infection 12 Diarrhea 12 Lymphocytosis 12 Cough 12 Irritability 12 Tachycardia 12 Tachypnea 12 a Includes viral, bacterial, fungal, and infections in which no pathogen was identified b Includes secondary hypertension c Includes events of drug eruption, pyrexia, rash, erythema, and hyperhidrosis Additional selected adverse reactions (all grades) that were reported in less than 10% of patients treated with GAMIFANT included: vomiting, acute kidney injury, asthenia, bradycardia, dyspnea, gastro-intestinal hemorrhage, epistaxis, and peripheral edema. HLH/MAS The safety of GAMIFANT was evaluated in two open-label clinical studies in patients with HLH/MAS in Stills disease, including sJIA [see Clinical Studies ( 14.2 )] . The pooled safety data from these two studies included 39 patients who received an initial dose of 6 mg/kg followed by 3 mg/kg every 3 days until Day 16, and then twice weekly thereafter. The median duration of treatment with GAMIFANT was 29 days (range: 7 to 220 days) and the median cumulative dose was 33 mg/kg (range: 12 to 175 mg/kg). Serious adverse reactions were reported in 12 patients (31%), with the most common serious adverse reaction being pneumonia (5%). Fatal adverse reactions occurred in two patients (5%) and included multiple organ dysfunction and circulatory shock. Pneumonia led to drug discontinuation in one patient (3%). The most common adverse reactions (≥20%) were viral infections, including cytomegalovirus i …

7 DRUG INTERACTIONS 7.1 Effect of GAMIFANT on Cytochrome P450 Substrates The formation of CYP450 enzymes may be suppressed by increased levels of cytokines (such as IFNγ) during chronic inflammation. By neutralizing IFNγ, use of GAMIFANT may normalize CYP450 activities which may reduce the efficacy of drugs that are CYP450 substrates due to increased metabolism. Upon initiation or discontinuation of concomitant GAMIFANT, monitor for reduced efficacy and adjust dosage of CYP450 substrate drugs as appropriate.

8 USE IN SPECIFIC POPULATIONS 8.1 Pregnancy Risk Summary There are no available data on GAMIFANT use in pregnant women to inform a drug-associated risk of adverse developmental outcomes. In an animal reproduction study, a murine surrogate anti-mouse IFNγ antibody administered to pregnant mice throughout gestation crossed the placental barrier, and no fetal harm was observed (see Data ) . The estimated background risk of major birth defects and miscarriage for the indicated population is unknown. All pregnancies have a background risk of birth defect, loss, or other adverse outcomes. In the U.S. general population, the estimated background risk of major birth defects and miscarriage in clinically recognized pregnancies is 2 to 4% and 15 to 20%, respectively. Data Animal Data In a mouse embryo-fetal development study, a murine surrogate anti-mouse IFNγ antibody was administered every 3-4 days throughout organogenesis and late gestation at doses of 0, 30, 75 or 150 mg/kg/occasion. The surrogate antibody was detected in the plasma of all treated pregnant mice and their corresponding fetuses. No maternal toxicity occurred and there was no evidence of teratogenicity or effects on embryo-fetal survival or growth. 8.2 Lactation Risk Summary There is no information regarding the presence of emapalumab-lzsg in human milk, the effects on the breastfed child, or the effects on milk production. Published data suggest that only limited amounts of therapeutic antibodies are found in breast milk and they do not enter the neonatal and infant circulations in substantial amounts. The developmental and health benefits of breastfeeding should be considered along with the mother's clinical need for GAMIFANT and any potential adverse effects on the breastfed child from GAMIFANT or from the underlying maternal condition. 8.4 Pediatric Use Safety and effectiveness of GAMIFANT have been established in pediatric patients with primary HLH that is reactivated or refractory to conventional therapies and with HLH/MAS in Still’s Disease (including sJIA) with an inadequate response to glucocorticoids [see Clinical Studies ( 14 )]. Use of GAMIFANT is supported by 3 single-arm trials which included 57 pediatric patients: 27 with primary HLH and 30 with HLH/MAS in Still’s disease. These studies included pediatric patients in the following age groups: 5 patients newborn to 6 months, 13 patients 6 months to 2 years, 27 patients from 2 years to <12 years, and 12 patients from 12 years to <17 years. 8.5 Geriatric Use Clinical studies of GAMIFANT did not include sufficient numbers of subjects aged 65 and over to determine whether they respond differently from younger subjects. Other reported clinical experience has not identified differences in responses between the elderly and younger patients.

12.1 Mechanism of Action Emapalumab-lzsg is a monoclonal antibody that binds to and neutralizes interferon gamma (IFNγ). Nonclinical data suggest that IFNγ plays a pivotal role in the pathogenesis of HLH by being hypersecreted.

11 DESCRIPTION Emapalumab-lzsg is an interferon gamma (IFNγ) neutralizing antibody. Emapalumab-lzsg is produced in Chinese Hamster Ovary cells by recombinant DNA technology. Emapalumab-lzsg is an IgG1 immunoglobulin with a molecular weight of approximately 148 kDa. GAMIFANT (emapalumab-lzsg) injection for intravenous use is a sterile, preservative-free, clear to slightly opalescent, colorless to slightly yellow solution provided in single-dose vials that require dilution prior to intravenous infusion. GAMIFANT 5 mg/mL (2 mL, 10 mL and 20 mL) Each vial contains 10 mg/2 mL, 50 mg/10 mL, or 100 mg/20 mL emapalumab-lzsg at a concentration of 5 mg/mL. Each mL also contains the following inactive ingredients: L-Histidine (1.55 mg), L-Histidine monohydrochloride, monohydrate (3.14 mg), Polysorbate 80 (0.05 mg), sodium chloride (7.30 mg), and Water for Injection, USP. GAMIFANT 25 mg/mL (2 mL, 4 mL, 10 mL and 20 mL) Each vial contains 50 mg/2 mL, 100 mg/4 mL, 250 mg/10 mL or 500 mg/20 mL emapalumab- lzsg at a concentration of 25 mg/mL. Each mL also contains the following inactive ingredients: L-Histidine (1.55 mg), L-Histidine monohydrochloride, monohydrate (3.14 mg), Polysorbate 80 (0.05 mg), sodium chloride (7.30 mg), and Water for Injection, USP.

10 OVERDOSAGE Consider contacting the Poison Help line (1-800-222-1222) or a medical toxicologist for additional overdose management recommendations.

16 HOW SUPPLIED/STORAGE AND HANDLING GAMIFANT (emapalumab-lzsg) injection is a sterile, clear to slightly opalescent, colorless to slightly yellow solution supplied in the following packaging configuration: NDC 66658-501-01 – containing one 10 mg/2 mL (5 mg/mL) single-dose vial NDC 66658-505-01 – containing one 50 mg/10 mL (5 mg/mL) single-dose vial NDC 66658-510-01 – containing one 100 mg/20 mL (5 mg/mL) single-dose vial NDC 66658-522-01 – containing one 50 mg/2 mL (25 mg/mL) single-dose vial NDC 66658-523-01 – containing one 100 mg/4 mL (25 mg/mL) single-dose vial NDC 66658-524-01 – containing one 250 mg/10 mL (25 mg/mL) single-dose vial NDC 66658-525-01 – containing one 500 mg/20 mL (25 mg/mL) single-dose vial Store GAMIFANT in a refrigerator at 2oC to 8oC (36oF to 46oF) in original carton to protect from light. Do not freeze or shake. This product contains no preservative.