Company-reported prevalence

Azetukalner

Overview

Field	Value
Drug	Azetukalner (XEN1101)
Indication	Focal onset seizures
Disease	Focal onset seizures (FOS), which the company also names focal seizures and focal epilepsy; the company also gives figures for all epilepsy in adults
Company	Xenon Pharmaceuticals (worldwide rights; acquired all rights to azetukalner from 1st Order Pharmaceuticals in April 2017). No partner holds rights to azetukalner; the Neurocrine Biosciences license agreement of December 2019 covers Nav1.6 and Nav1.2/1.6 sodium channel inhibitors
Documents searched	Xenon Pharmaceuticals website: home, pipeline, therapeutic areas, clinical trials, patients, health care providers, science, about, and media pages, accessed October 14, 2026; Epilepsy by the Numbers infographic, April 2026; What Does It Mean to Live With Epilepsy? infographic, 2026; corporate presentation, September 2026; Form 10-K for 2025, filed February 26, 2026; Form 10-K for 2024, filed February 27, 2025; Form 10-Q for the quarter ended June 30, 2026, filed August 2026; Form 424B5 prospectus supplement, March 2026; 2025 annual report, April 2026; press releases of September 17, 2026, August 26, 2026, August 6, 2026, April 19, 2026, March 9, 2026, January 12, 2026, December 5, 2025, December 3, 2025, April 4, 2025, January 13, 2025, December 6, 2024, November 25, 2024, September 9, 2024, May 28, 2024, April 16, 2024, January 8, 2024, December 2, 2023, November 27, 2023, November 9, 2023, October 9, 2023, September 4, 2023, and April 24, 2023
Data as of	October 14, 2026
Prepared by	AI research agent (Claude); not yet reviewed by a person

Company statements of prevalence

United States

Number affected (adults with epilepsy): Xenon Pharmaceuticals corporate presentation, September 2026

“Estimated Diagnosed Adult Epilepsy Patient Population in the U.S.” (opens the source at this quote in a new tab)
“3M U.S. Adults with Epilepsy” (opens the source at this quote in a new tab)

Cited source: 2.1 Milligan 2021; 2.2 Kobau 2023; 2.3 Gupta 2017; 2.4 Keränen 1988; 2.5 ScienceDirect 2026; 2.6 Barnard 2025

Xenon Pharmaceuticals (2026) corporate presentation, September 2026, quoted passage highlighted — Captured from page 8 of 43 (opens in a new tab)

Number affected (adults with focal onset seizures): Xenon Pharmaceuticals corporate presentation, September 2026

“Estimated Diagnosed Adult Epilepsy Patient Population in the U.S.” (opens the source at this quote in a new tab)
“Focal Onset Seizures FOS represent the largest segment of the epilepsy population” (opens the source at this quote in a new tab)
“1.8M” (opens the source at this quote in a new tab)

Cited source: 2.1 Milligan 2021; 2.2 Kobau 2023; 2.3 Gupta 2017; 2.4 Keränen 1988; 2.5 ScienceDirect 2026; 2.6 Barnard 2025

Prevalence (share of patients without seizure freedom on first-line treatment or with drug-resistant epilepsy): Xenon Pharmaceuticals corporate presentation, September 2026

“Significant Epilepsy Burden in U.S.” (opens the source at this quote in a new tab)
“Despite availability of 30+ ASMs, up to 50% of patients do not achieve seizure freedom with 1st line ASMs, and about 1/3 have drug-resistant epilepsy” (opens the source at this quote in a new tab)

Cited source: 2.7 Johannessen Landmark 2023; 2.8 Chen 2018; 2.9 Kwan 2010; 2.6 Barnard 2025; 2.10 Löscher 2021

Number affected (adults with epilepsy): Xenon Pharmaceuticals epilepsy infographic, April 2026

“million adults” (opens the source at this quote in a new tab)
“in the U.S. live with epilepsy” (opens the source at this quote in a new tab)

Cited source: 2.11 Centers for Disease Control and Prevention 2024

Xenon Pharmaceuticals (2026) Epilepsy by the Numbers infographic, April 2026, quoted passage highlighted — Captured from page 1 of 1 (opens in a new tab)

Number affected (adults with epilepsy): Xenon Pharmaceuticals website, October 2026

“It is the fourth most common neurological condition and affects nearly 3 million adults in the U.S.” (opens the source at this quote in a new tab)

Cited source: None stated in the document.

Xenon Pharmaceuticals (2026) therapeutic areas web page, quoted passage highlighted — Captured from the passage on the page (opens in a new tab)

Number affected (adults with epilepsy): Xenon Pharmaceuticals press release, September 2026

“It is the fourth most common neurological condition and affects approximately three million adults in the U.S.” (opens the source at this quote in a new tab)

Cited source: None stated in the document.

Xenon Pharmaceuticals (2026) press release, September 17, 2026, quoted passage highlighted — Captured from the passage on the page (opens in a new tab)

Number affected (people with focal onset seizures): Xenon Pharmaceuticals Form 10-K for 2025, February 2026

“Approximately 60% of people with epilepsy in the U.S. have FOS, which results in a total patient population of approximately 1.8 million.” (opens the source at this quote in a new tab)

Cited source: None stated in the document.

Xenon Pharmaceuticals (2026) Form 10-K for 2025, quoted passage highlighted — Captured from the passage on the page (opens in a new tab)

Europe

No evidence found.

Global

No evidence found.

Other countries and regions

No evidence found.

Geography not stated

Prevalence (share of people with epilepsy who have focal onset seizures): Xenon Pharmaceuticals epilepsy infographic, April 2026

“Focal onset seizures (FOS) are the most common seizure type, affecting about 60% of people with epilepsy.” (opens the source at this quote in a new tab)

Cited source: 2.12 Ighodaro 2023; 2.13 Beghi 2020

Prevalence (share of people with epilepsy who have drug-resistant epilepsy): Xenon Pharmaceuticals epilepsy infographic, April 2026

“About 1/3 have drug-resistant epilepsy.” (opens the source at this quote in a new tab)

Cited source: 2.7 Johannessen Landmark 2023; 2.9 Kwan 2010

Prevalence (share of newly diagnosed focal onset seizures without seizure freedom at one year): Xenon Pharmaceuticals epilepsy infographic, April 2026

“Approximately half with newly diagnosed FOS are not able to achieve seizure freedom at one year with first-line therapy.” (opens the source at this quote in a new tab)

Cited source: 2.14 Barnard 2024; 2.8 Chen 2018

Prevalence (share of people with epilepsy who could benefit from additional treatment options): Xenon Pharmaceuticals epilepsy infographic, April 2026

“Up to 50% of epilepsy patients could potentially benefit from additional treatment options to improve seizure control.” (opens the source at this quote in a new tab)

Cited source: 2.7 Johannessen Landmark 2023; 2.14 Barnard 2024; 2.8 Chen 2018; 2.9 Kwan 2010

Prevalence (share of patients inadequately managed with initial lines of therapy): Xenon Pharmaceuticals Form 10-K for 2025, February 2026

“Despite the availability of multiple treatment options, up to 50% of patients are considered inadequately managed with initial lines of therapy warranting additional treatment options.” (opens the source at this quote in a new tab)

Cited source: None stated in the document.

Prevalence (share of people with focal epilepsy who have uncontrolled seizures): Xenon Pharmaceuticals press release, September 2026

“However, despite more than 30 available epilepsy treatments, up to half of people with focal epilepsy still live with uncontrolled seizures.” (opens the source at this quote in a new tab)

Cited source: None stated in the document.

Prevalence (share of people with focal epilepsy who have uncontrolled seizures): Xenon Pharmaceuticals website, October 2026

“However, despite treatment, about half of people with focal epilepsy still live with uncontrolled seizures.” (opens the source at this quote in a new tab)

Cited source: None stated in the document.

Sources the company cites

Milligan 2021

Reference as the company lists it

“Milligan TA. Am J Med. 2021” (opens the source at this quote in a new tab)

Passage carrying the nearest figure

“Epilepsy is the fourth most common neurological disorder and affects 1 in 26 people in the United States and 65 million people worldwide.” (opens the source at this quote in a new tab)

Milligan 2021, quoted passage highlighted — Captured from the passage on the page (opens in a new tab)

Kobau 2023

Reference as the company lists it

“Kobau R et al. Epilepsy Behav. 2023” (opens the source at this quote in a new tab)

Passage carrying the nearest figure

“In 2021, 1.1% of U.S. adults, (approximately 2,865,000 adults) reported active epilepsy” (opens the source at this quote in a new tab)

Kobau 2023, quoted passage highlighted — Captured from the passage on the page (opens in a new tab)

Gupta 2017

Reference as the company lists it

“Gupta S et al. Epilepsia Open. 2017” (opens the source at this quote in a new tab)

Passage carrying the nearest figure

“Focal epilepsy comprises about 55.7–61.1% of the overall epilepsy patient population.” (opens the source at this quote in a new tab)

Gupta 2017, quoted passage highlighted — Captured from the passage on the page (opens in a new tab)

Keränen 1988

Reference as the company lists it

“Keränen T et al. Epilepsia. 1988” (opens the source at this quote in a new tab)

Passage carrying the nearest figure

“Fifty-six percent of patients had partial seizures and 26.5% had generalized seizures.” (opens the source at this quote in a new tab)

Keränen 1988, quoted passage highlighted — Captured from the passage on the page (opens in a new tab)

ScienceDirect 2026

Reference as the company lists it

“ScienceDirect. 2026” (opens the source at this quote in a new tab)

Passage carrying the figure

Not quoted: The reference names a publisher platform and a year and no title, author, or address, so the cited document could not be identified.

Barnard 2025

Reference as the company lists it

“Barnard SN et al. JAMA Neurol. 2025” (opens the source at this quote in a new tab)

Passage carrying the nearest figure

“Epilepsy affects approximately 65 million people worldwide, and 60% have focal seizures.” (opens the source at this quote in a new tab)
“There were 245 treatment-sensitive participants (54.7%), 102 treatment-resistant participants (22.8%), and 101 indeterminate participants (22.5%).” (opens the source at this quote in a new tab)
“Among treatment-sensitive participants, most (217 [89.3%]) responded to monotherapy and half (121 [49.4%], or 27% of total cohort) became seizure free while receiving their first ASM.” (opens the source at this quote in a new tab)

Barnard 2025, quoted passage highlighted — Captured from the passage on the page (opens in a new tab)

Johannessen landmark 2023

Reference as the company lists it, corporate presentation, September 2026

“Landmark CJ et al. Epileptic Disord. 2023” (opens the source at this quote in a new tab)

Reference as the company lists it, Epilepsy by the Numbers infographic, April 2026

“Landmark CJ, et al. Pharmacology of antiseizure medications. Epileptic Disord. 2023.” (opens the source at this quote in a new tab)

Passage carrying the figure

Not quoted: The review, open access at the publisher, addresses the pharmacology, drug interactions, and therapeutic drug monitoring of antiseizure medications and states no proportion of patients with drug-resistant epilepsy or uncontrolled seizures.

Chen 2018

Reference as the company lists it, corporate presentation, September 2026

“Chen Z et al. JAMA. 2018” (opens the source at this quote in a new tab)

Reference as the company lists it, Epilepsy by the Numbers infographic, April 2026

“Chen Z, et al. Long-term outcomes with ASMs. JAMA Neurol. 2018.” (opens the source at this quote in a new tab)

Passage carrying the nearest figure

“More than one-third of patients experience epilepsy that remains uncontrolled.” (opens the source at this quote in a new tab)
“There were 820 patients who were seizure free 1 year or longer with the initial AED, so the predicted probability was 50.5% (95% CI, 47.9%-53.1%).” (opens the source at this quote in a new tab)

Chen 2018, quoted passage highlighted — Captured from the passage on the page (opens in a new tab)

Kwan 2010

Reference as the company lists it, corporate presentation, September 2026

“Kwan P. Epilepsia. 2010” (opens the source at this quote in a new tab)

Reference as the company lists it, Epilepsy by the Numbers infographic, April 2026

“Kwan P, et al. Definition of drug-resistant epilepsy. Epilepsia. 2010.” (opens the source at this quote in a new tab)

Passage carrying the figure

Not quoted: The consensus proposal defines drug-resistant epilepsy and states no proportion of people with epilepsy who meet the definition or who need additional treatment.

Löscher 2021

Reference as the company lists it

“Löscher W and Klein P. CNS Drugs. 2021” (opens the source at this quote in a new tab)

Passage carrying the figure

“The goal of epilepsy therapy is the complete elimination of seizures; however, this is not achievable in about one-third of patients.” (opens the source at this quote in a new tab)
“However, despite the availability of numerous ASMs with different mechanisms of action (MOAs), both SRS and SE may be resistant to treatment in about 30% of all patients with epilepsy” (opens the source at this quote in a new tab)

Löscher 2021, quoted passage highlighted — Captured from the passage on the page (opens in a new tab)

Centers for disease control and prevention 2024

Reference as the company lists it

“CDC. Epilepsy facts & statistics. 2024.” (opens the source at this quote in a new tab)

Passage carrying the nearest figure

“Almost 3 million U.S. adults have epilepsy.” (opens the source at this quote in a new tab)
“During 2021 and 2022, about 2.9 million U.S. adults 18 and older reported having active epilepsy.” (opens the source at this quote in a new tab)

Centers for Disease Control and Prevention (2024) epilepsy facts and stats page, quoted passage highlighted — Captured from the passage on the page (opens in a new tab)

Ighodaro 2023

Reference as the company lists it

“Ighodaro ET, et al. Focal onset seizure. StatPearls. 2023.” (opens the source at this quote in a new tab)

Passage carrying the nearest figure

“An estimated 52.5 million people worldwide are affected by epilepsy.” (opens the source at this quote in a new tab)
“Focal onset seizures are more prevalent than generalized onset seizures.” (opens the source at this quote in a new tab)

Ighodaro 2023, quoted passage highlighted — Captured from the passage on the page (opens in a new tab)

Beghi 2020

Reference as the company lists it

“Beghi E. Epidemiology of epilepsy. Neuroepidemiology. 2020.” (opens the source at this quote in a new tab)

Passage carrying the figure

Not quoted: Closed access; the abstract states that focal seizures are more common than generalized seizures in children and in adults and gives no percentage.

Barnard 2024

Reference as the company lists it

“Barnard S, et al. Treatment outcomes in newly diagnosed focal epilepsy. AES. 2024.” (opens the source at this quote in a new tab)

Passage carrying the nearest figure

“267 (59.6%) participants achieved at least 1 period of seizure freedom and 121 participants did so on their first ASM (45.3% of ever seizure free; 27.0% of all participants).” (opens the source at this quote in a new tab)
“Our preliminary findings suggest that over half of people newly diagnosed with focal epilepsy will be sensitive to treatment. Only one third can expect to sustain seizure freedom 1 year post stable treatment initiation.” (opens the source at this quote in a new tab)

Barnard 2024, quoted passage highlighted — Captured from the passage on the page (opens in a new tab)

Overview

1Company statements of prevalence

Number affected (adults with epilepsy): Xenon Pharmaceuticals corporate presentation, September 2026

Number affected (adults with focal onset seizures): Xenon Pharmaceuticals corporate presentation, September 2026

Prevalence (share of patients without seizure freedom on first-line treatment or with drug-resistant epilepsy): Xenon Pharmaceuticals corporate presentation, September 2026

Number affected (adults with epilepsy): Xenon Pharmaceuticals epilepsy infographic, April 2026

Number affected (adults with epilepsy): Xenon Pharmaceuticals website, October 2026

Number affected (adults with epilepsy): Xenon Pharmaceuticals press release, September 2026

Number affected (people with focal onset seizures): Xenon Pharmaceuticals Form 10-K for 2025, February 2026

Prevalence (share of people with epilepsy who have focal onset seizures): Xenon Pharmaceuticals epilepsy infographic, April 2026

Prevalence (share of people with epilepsy who have drug-resistant epilepsy): Xenon Pharmaceuticals epilepsy infographic, April 2026

Prevalence (share of newly diagnosed focal onset seizures without seizure freedom at one year): Xenon Pharmaceuticals epilepsy infographic, April 2026

Prevalence (share of people with epilepsy who could benefit from additional treatment options): Xenon Pharmaceuticals epilepsy infographic, April 2026

Prevalence (share of patients inadequately managed with initial lines of therapy): Xenon Pharmaceuticals Form 10-K for 2025, February 2026

Prevalence (share of people with focal epilepsy who have uncontrolled seizures): Xenon Pharmaceuticals press release, September 2026

Prevalence (share of people with focal epilepsy who have uncontrolled seizures): Xenon Pharmaceuticals website, October 2026

2Sources the company cites

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Reference as the company lists it, corporate presentation, September 2026

Reference as the company lists it, Epilepsy by the Numbers infographic, April 2026

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Reference as the company lists it, corporate presentation, September 2026

Reference as the company lists it, Epilepsy by the Numbers infographic, April 2026

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Reference as the company lists it, corporate presentation, September 2026

Reference as the company lists it, Epilepsy by the Numbers infographic, April 2026

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3References

Company statements of prevalence

Sources the company cites

References