An on-demand pill for hereditary angioedema attacks clears the FDA

The Food and Drug Administration approved sebetralstat, sold as Ekterly, on 3 July for the treatment of acute attacks of hereditary angioedema in adults and children aged 12 and older [s1]. It is a plasma kallikrein inhibitor taken as a tablet [s1].

The route of administration is the point. Hereditary angioedema produces episodes of swelling — in the limbs, the abdomen, or, most dangerously, the airway — that arrive with little warning and escalate over hours. The trial that supported this approval was designed against a specific problem: the approved on-demand treatments available when it was run all had to be given parenterally, a route associated with delays in treatment or with therapy being withheld altogether [s2].

What the label says

The recommended dose is 600 mg — two 300 mg tablets — taken by mouth at the earliest recognition of an attack [s1]. A second 600 mg dose may be taken at least three hours after the first if the response is inadequate or if symptoms worsen or recur, up to a maximum of 1,200 mg in any 24-hour period [s1].

The label carries dosing modifications that matter clinically. Sebetralstat is a CYP3A4 substrate: concomitant use with strong CYP3A4 inhibitors, and with strong or moderate CYP3A4 inducers, is to be avoided; with moderate inhibitors the dose is reduced to 300 mg [s1]. In patients with moderate hepatic impairment the dose is likewise 300 mg, and use is to be avoided in severe hepatic impairment [s1]. Sebetralstat exposure fell substantially alongside enzyme inducers — with phenytoin, maximum concentration dropped 66% and total exposure 83%; with efavirenz, 63% and 79% [s1].

The evidence

Approval rests on KONFIDENT, a double-blind, randomised, placebo-controlled, three-way complete crossover trial comparing sebetralstat 600 mg and 300 mg against placebo [s1]. A total of 136 participants aged 12 and older with type 1 or type 2 hereditary angioedema were assigned to one of six treatment sequences, and 110 of them went on to treat 264 attacks [s2].

Of those 264 attacks, 142 (54%) involved peripheral symptoms only, 85 (32%) abdominal symptoms only, 27 (10%) both, and 8 (3%) mild to moderate laryngeal symptoms; two had a missing location [s1]. Severe laryngeal attacks — the ones that threaten the airway — were not treated in the trial [s1]. That exclusion is the single most important limit on what this evidence can say.

The primary endpoint was the beginning of symptom relief, defined as a rating of at least "a little better" on a seven-point patient-reported global impression of change scale at two consecutive time points within 12 hours of the first dose [s1]. Seventy-one of 93 patients (76%) given 600 mg reached that endpoint, against 41 of 84 (49%) on placebo, a statistically significant difference [s1]. Median time to the beginning of relief on 600 mg was 2.0 hours (95% CI 1.5 to 2.8); fewer than half of placebo attacks reached the endpoint at all within 12 hours, so no median could be estimated for placebo [s1]. In the 600 mg group, 38% of patients took a second dose within 12 hours [s1].

The published trial reports the same comparison in its own terms: median time to the beginning of symptom relief was 1.61 hours with 300 mg, 1.79 hours with 600 mg and 6.72 hours with placebo [s2]. Complete resolution within 24 hours occurred in 42.5% of attacks with 300 mg, 49.5% with 600 mg and 27.4% with placebo [s2].

Note that the 300 mg dose performed comparably in the trial, but the label states plainly that 300 mg is not a recommended dose for treating acute attacks — it is reserved for the interaction and hepatic-impairment scenarios described above [s1].

Safety, as far as it goes

In KONFIDENT's safety population, 93 patients received 600 mg, 86 received 300 mg and 83 received placebo [s1]. The only adverse reaction reported at an incidence of at least 2% and more common than placebo was headache, in 3 patients (3.2%) on 600 mg versus 1 (1.2%) on placebo [s1]. The trial investigators reported similar safety profiles for sebetralstat and placebo, with no serious adverse events related to the trial agents [s2].

Those are small numbers. A crossover trial in 110 patients treating 264 attacks is adequate to detect a difference in time-to-relief; it is not large enough to characterise uncommon harms, and the label's adverse-reaction table should be read as a first sketch rather than a settled profile.

What is and is not established

What the evidence supports is that an oral kallikrein inhibitor, taken at the onset of an attack, shortens the time to the beginning of symptom relief compared with placebo, in attacks that were mostly peripheral or abdominal.

What it does not establish is performance in severe laryngeal attacks, which were excluded [s1]; comparative effectiveness against the existing injected or infused on-demand treatments, which KONFIDENT did not test — its comparator was placebo [s2]; or anything about long-term prophylaxis, which is a different clinical question from on-demand treatment. Twenty-two per cent of KONFIDENT participants were already on background prophylaxis [s1], but the trial was not designed to answer how the two strategies interact.

The trial population was also narrow demographically: 84% white, 9% Asian, 1% Black or African American, with 6% reporting Hispanic or Latino ethnicity, and 92% had type 1 disease [s1].

What to watch

Two things. First, whether real-world use in laryngeal attacks — which will happen, because attacks do not announce their location in advance — generates safety or effectiveness signals that the trial could not. Second, whether an oral option changes the treatment-delay pattern the trial was built around [s2]: the argument for a pill is that people will actually take it early, and that is a behavioural claim which only post-marketing data can test.

This article is informational and does not constitute medical advice. Decisions about treatment for hereditary angioedema belong with a clinician who knows the individual case.

Sources

• [s1] EKTERLY (sebetralstat) tablets, for oral use — prescribing information, NDA 219301, US Food and Drug Administration, approved 3 July 2025. https://www.accessdata.fda.gov/drugsatfda_docs/label/2025/219301s000lbl.pdf
• [s2] Oral Sebetralstat for On-Demand Treatment of Hereditary Angioedema Attacks — New England Journal of Medicine, published online 31 May 2024. https://doi.org/10.1056/NEJMoa2314192