What the label lists and what reports show
Emapalumab side effects
Emapalumab's FDA label: “In patients with primary HLH, the most common adverse reactions (≥ 20%) were: infections, hypertension, infusion-related reactions, and pyrexia.” FAERS holds 208 reports naming it through July 30, 2026; the reaction reported most often, leaving out the conditions it is used for, product-use terms and outcomes, is haemophagocytic lymphohistiocytosis (58 reports).
- No generic listed
Check it at the source: the emapalumab FDA label on DailyMed (effective March 26, 2026); the FDA FAERS public dashboard.
What does the patient leaflet say about side effects?
From the patient leaflet: What are the possible side effects of GAMIFANT?GAMIFANT can cause serious side effects, including: See "What is the most important information I should know about GAMIFANT?" Infusion reactions. Infusion reactions, including severe reactions, can happen during or within 24 hours after the start of your GAMIFANT infusion. Your healthcare provider may temporarily stop your infusion and treat your symptoms before continuing your infusion at a slower rate if you get severe infusion reactions. […]
Source: FDA drug label, Swedish Orphan Biovitrum AB (publ), effective March 26, 2026 (SPL set a865e0ef-8685-4f69-8838-648c4f3bab47), via openFDA; the full label on DailyMed
What does the label list?
From the label: adverse reactionsIn patients with primary HLH, the most common adverse reactions (≥ 20%) were: infections, hypertension, infusion-related reactions, and pyrexia.
A table the label prints in its adverse reactions section without a title; its column headings name the groups compared
| 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 |
Rows and numbers as the label prints them, under its own column headings (the first rows of a longer table where it runs on). A reaction in a trial table is not necessarily caused by the medicine, and trials differ from everyday use.
From the label: adverse reactions, continuedThe 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 )]. …
Source: FDA drug label, Swedish Orphan Biovitrum AB (publ), effective March 26, 2026 (SPL set a865e0ef-8685-4f69-8838-648c4f3bab47), via openFDA; the full label on DailyMed
What do FAERS reports show?
208 reports list emapalumab among the medicines taken, each a report of something that happened, not proof the medicine caused it; 87 are coded as a death and 55 as a hospital stay. Counts follow how widely a medicine is used and watched, and they are not a measure of how risky it is. Of the 21 reactions below, 7 are named by the same term (in US spelling) in the label's adverse reactions, warnings or patient leaflet; a reaction the label does not name may still be there under another word, and a report does not show that the medicine caused it.
The 25 most reported reactions
Source: FDA Adverse Event Reporting System (FAERS) via openFDA, reports through July 30, 2026; reactions as MedDRA preferred terms
What next?
- Emapalumab: the full record
- label, generics, price, shortages, recalls
- Report a side effect to the FDA
- MedWatch
- Side effects hub
- the most reported medicines and reactions