- Evidence
- AStrong human evidence
- FDA status
- FDA approvedas of 2026-10-26
- Route
- Injection
- Studies cited
- 1 human0 animal or cell
An injection that treats attacks of swelling in people with hereditary angioedema. Two controlled trials show it works, but about 4% had a severe allergic reaction.
Sold for
Ecallantide is an on-demand treatment for hereditary angioedema attacks that blocks the enzyme driving the swelling.
Studies say
Two placebo-controlled trials support the approved use, so the grade is A, with the caveat that about 4% of treated patients in trials had anaphylaxis.
Why grade A. Approval was based on two randomized, double-blind, placebo-controlled trials, EDEMA3 (n=72, cited here) and EDEMA4 (n=96), both showing faster symptom relief than placebo during acute attacks. The trials were small by the standards of common diseases, but hereditary angioedema is rare and two consistent placebo-controlled trials meet the bar for A. 12
FDA. Approved. Ecallantide is sold as Kalbitor, approved by the FDA in December 2009 for acute attacks of hereditary angioedema, originally in patients 16 and older and extended in 2014 to patients 12 and older. It carries a boxed warning for anaphylaxis and must be given by a healthcare professional. 2
Written from 2 cited sources. Fact-checked 2026-10-27: 14 claims checked, 2 corrected. Last refreshed 2026-10-27. Not physician reviewed.
What this means for you
- What people take it for
- Attacks of swelling in hereditary angioedema
- Can a US doctor prescribe it?
- Yes, FDA approved for sudden attacks of hereditary angioedema.
- Properly tested in people?
- Yes, in two controlled trials of 72 and 96 people.
Evidence checklist
- Randomised controlled trial EDEMA3 and EDEMA4 placebo-controlledyes
- Human study over 100 people Largest trial had 96 patientsno
- More than one research group Trials from one program, sponsor-runno information
- Clinical outcomes, not surrogate markers Attack symptom relief measuredyes
- Human safety data beyond case reports Anaphylaxis rate from 255 treated patientsyes
Drawn from the cited studies below. A dash means the sources give no information.
What it is
Ecallantide is a 60-amino-acid recombinant protein that inhibits plasma kallikrein. It was engineered by phage display, a laboratory method for evolving protein binders, from a human protein scaffold, not from an animal source. It is produced in yeast and sold as Kalbitor, originally by Dyax and now by Takeda. 12
Hereditary angioedema is a genetic deficiency of C1 inhibitor that leads to unpredictable attacks of deep swelling in the skin, gut and airway. Ecallantide is one of several on-demand treatments for those attacks; others include C1 inhibitor concentrates and icatibant. 1
How it works
In hereditary angioedema, uncontrolled plasma kallikrein cleaves high-molecular-weight kininogen to release bradykinin, a peptide that makes blood vessels leak fluid into tissue. Ecallantide binds kallikrein tightly and reversibly, cutting off bradykinin production at its source. It acts within minutes of a subcutaneous injection, which is why it is used for attacks not for prevention. 1
What human research shows
EDEMA3 randomized 72 patients having a moderate-to-severe attack to a single subcutaneous dose of ecallantide or placebo. At four hours, the median treatment outcome score (a patient-rated measure of improvement) was 50 on ecallantide versus 0 on placebo, and the median symptom severity score fell by 1.0 point versus 0.5. Both differences were statistically significant; the label reports the same trial as means of 63 versus 36 and 1.1 versus 0.6. 12
EDEMA4, the second phase 3 trial, enrolled 96 patients and found the same pattern: a greater fall in symptom severity at four hours (0.8 versus 0.4) and a higher treatment outcome score (53 versus 8). The FDA approved the drug on the two trials together, covering 143 unique patients since some took part in both. 2
| Study | Model | Finding |
|---|---|---|
| EDEMA3 | Humans, n=72, randomized double-blind placebo-controlled, acute attacks | Median treatment outcome score at four hours was 50 on ecallantide versus 0 on placebo (label means 63 versus 36). 1 |
| EDEMA4 (label) | Humans, n=96, randomized double-blind placebo-controlled, acute attacks | Symptom severity fell more at four hours (0.8 versus 0.4) and treatment outcome score was 53 versus 8. 2 |
Safety
Anaphylaxis is the defining risk. Across clinical trials, about 4% of treated patients (10 of 255) had an anaphylactic reaction, typically within an hour of the injection. This is why the label carries a boxed warning and requires administration by a healthcare professional able to treat anaphylaxis, and why ecallantide, unlike icatibant, cannot be self-injected at home. Patients may also develop antibodies to the drug with repeated use. 2
Common adverse events in trials were headache, nausea, diarrhea, fever, injection-site reactions and upper respiratory infection. 12
Questions for your clinician
- Why is ecallantide given by a health professional rather than self-injected?
- How does it compare with other on-demand angioedema treatments?
- What is my plan if I react within the first hour?
Questions people ask
Is ecallantide FDA-approved?
Yes. Kalbitor was approved in 2009 for acute hereditary angioedema attacks in patients 16 and older, and the age limit was lowered to 12 in 2014. 2
Why can't ecallantide be self-injected?
About 4% of patients in trials had anaphylaxis, usually within an hour. The FDA boxed warning requires it to be given by a healthcare professional prepared to treat that reaction. 2
How does ecallantide differ from icatibant?
Both treat acute attacks, but at different points in the same pathway: ecallantide stops bradykinin from being made by inhibiting kallikrein, while icatibant blocks the bradykinin B2 receptor. Icatibant is approved for self-administration; ecallantide is not because of the anaphylaxis risk. 12
Does ecallantide prevent attacks?
No. It is approved only for treating attacks once they begin. Preventive options for hereditary angioedema use other drugs, including the antibody lanadelumab, which also targets kallikrein. 2