--- title: "Xenon pauses depression trial enrollment" url: "https://aibio.space/news/xenon-pauses-depression-trial-enrollment-after-psychosis-reports/" publisher: "aibio.space (Biotech Investor Relations News)" date: "2026-09-18" section: "Distress" tickers: "NASDAQ:XENE" source: "https://fiercebiotech.com/biotech/xenon-pauses-phase-3-depression-trials-after-psychosis-events" summary: "The company stopped enrolling in its phase 3 MDD and bipolar studies of azetukalner. Fierce Biotech reported the shares fell 26% pre-market the next day." --- By the aibio.space Xenon desk. Sources - [Fierce Biotech](https://fiercebiotech.com/biotech/xenon-pauses-phase-3-depression-trials-after-psychosis-events) - [BioPharma Dive](https://www.biopharmadive.com/news/xenon-azetukalner-depression-trial-halt-adverse-events/830756/) - [Xenon press release (via Finviz)](https://finviz.com/news/393312/xenon-announces-azetukalner-nda-submission-to-fda-for-focal-seizures-and-provides-update-on-psychiatry-clinical-program) [XENE](https://aibio.space/companies/xenon-pharmaceuticals/) 2026-09-18 # Xenon pauses depression trial enrollment after psychosis reports, shares drop Tickers [XENE](https://aibio.space/companies/xenon-pharmaceuticals/) The company stopped enrolling in its phase 3 MDD and bipolar studies of azetukalner. Fierce Biotech reported the shares fell 26% pre-market the next day. ## Key facts - **Company**: Xenon Pharmaceuticals Inc. (NASDAQ: XENE) - **News type**: Distress - **Primary source**: [Fierce Biotech](https://fiercebiotech.com/biotech/xenon-pauses-phase-3-depression-trials-after-psychosis-events) *Stone columns of a government building. Photo: The Building Envelope, CC0, via StockSnap. The picture shows the field, not the companies named.* Xenon Pharmaceuticals said on September 17 that it had paused new enrollment in its phase 3 studies of azetukalner in major depressive disorder and bipolar depression after neuropsychiatric adverse events. [Fierce Biotech reported](https://fiercebiotech.com/biotech/xenon-pauses-phase-3-depression-trials-after-psychosis-events) that the shares fell 26% in pre-market trading the next day to $42.25, from a Thursday close of $57.35. BioPharma Dive put the intraday drop at [up to 30%](https://www.biopharmadive.com/news/xenon-azetukalner-depression-trial-halt-adverse-events/830756/). Patients already enrolled stay in the studies. The epilepsy trials are not affected, and Xenon filed its FDA application for azetukalner in focal seizures [the same day](https://finviz.com/news/393312/xenon-announces-azetukalner-nda-submission-to-fda-for-focal-seizures-and-provides-update-on-psychiatry-clinical-program). ## The details Chief medical officer Christopher Kenney told Fierce that a small percentage of patients had confusion, aphasia or ataxia, and that ["in a very small number of patients, we have seen an adverse event captured under the broad preferred term of psychosis."](https://fiercebiotech.com/biotech/xenon-pauses-phase-3-depression-trials-after-psychosis-events) Executives described the events as [mild to moderate, short in duration and reversible](https://www.biopharmadive.com/news/xenon-azetukalner-depression-trial-halt-adverse-events/830756/), according to William Blair analyst Myles Minter, who was on the call. Xenon said the events were consistent with azetukalner's known safety profile and did not appear in its phase 2 depression study. The company suggested that [exposing more patients in a larger phase 3](https://www.biopharmadive.com/news/xenon-azetukalner-depression-trial-halt-adverse-events/830756/) may have brought them out. In epilepsy, where the drug has more than 1,500 patient-years of exposure, [there was one psychosis case in each of two phase 3 trials](https://fiercebiotech.com/biotech/xenon-pauses-phase-3-depression-trials-after-psychosis-events). Xenon plans to adjust dosing over the coming months to improve tolerability and has told the FDA. It calls the pause temporary. X-NOVA2, the first depression study, has enrolled about 360 patients, roughly 80% of its target. Xenon plans to finish dosing the enrolled patients and unblind the data, with [topline data now expected in the first quarter of 2027](https://finviz.com/news/393312/xenon-announces-azetukalner-nda-submission-to-fda-for-focal-seizures-and-provides-update-on-psychiatry-clinical-program). In August the company had guided to the [first half of 2027](https://investor.xenon-pharma.com/node/14566/pdf). X-NOVA2 had an initial enrollment target of 450 patients, [per Xenon's release](https://finviz.com/news/393312/xenon-announces-azetukalner-nda-submission-to-fda-for-focal-seizures-and-provides-update-on-psychiatry-clinical-program). ## Context Another Kv7 drug had trouble a week earlier. Fierce reported that Biohaven paused focal epilepsy trials of BHV-7000, a Kv7.2/7.3 activator, and has released limited information. Xenon CEO Ian Mortimer said nothing public [suggests a link](https://fiercebiotech.com/biotech/xenon-pauses-phase-3-depression-trials-after-psychosis-events) to azetukalner's adverse events. William Blair analysts told clients that Zoloft and Wellbutrin have similar psychosis rates, that the two pauses are unrelated and do not point to a class-wide Kv7 problem, and that epilepsy prospects are unaffected, per Fierce. They cut their probability of success in MDD from 60% to 50%, having already seen the indication as risky because of [mixed phase 2 data](https://fiercebiotech.com/biotech/xenon-pauses-phase-3-depression-trials-after-psychosis-events). Before the drop, Xenon's market value had risen above $5 billion, and some analysts saw it as an acquisition candidate, per BioPharma Dive. It also ended June with [$1,245.1 million in cash](https://investor.xenon-pharma.com/node/14566/pdf). ## What it means for investors The drop shows how much of Xenon's value was riding on psychiatry. Epilepsy is the approved-path asset: the filing is in, the phase 3 data were strong, and analysts quoted by BioPharma Dive argued the FDA is unlikely to weigh depression findings heavily in the epilepsy review, since common epilepsy drugs carry [more serious side-effect risks](https://www.biopharmadive.com/news/xenon-azetukalner-depression-trial-halt-adverse-events/830756/). That is an analyst view, not an FDA statement. Depression is the open question. The BIO/Informa/QLS base rates show only [57.8% of phase 3 programs reach a filing](https://go.bio.org/rs/490-EHZ-999/images/ClinicalDevelopmentSuccessRates2011_2020.pdf) across all areas, and Xenon's own MDD evidence going in was mixed. A dosing change could help tolerability but may also weaken efficacy, and the company has not said what doses it will test. There is also a label risk. Even if the events stay out of the epilepsy decision, the FDA could ask for them to be described in the safety section of any label. Xenon has [told the agency about the pause](https://fiercebiotech.com/biotech/xenon-pauses-phase-3-depression-trials-after-psychosis-events). ## What to watch Topline X-NOVA2 data are due in the first quarter of 2027. Investors will look for the revised dosing plan, any FDA comment on the pause, and the agency's decision to accept the epilepsy filing. Phase 1 pain studies of XEN1701 and XEN1120 are due to finish in the [second half of 2026](https://investor.xenon-pharma.com/node/14566/pdf). [Report an error](https://aibio.space/reputation/#correction) ## Companies in this story XENE Xenon Pharmaceuticals Inc. NASDAQ ยท Canada Open the desk ## More from the Xenon desk Financings ### [Xenon prices $650 million stock offering at $57 after epilepsy data](https://aibio.space/news/xenon-prices-650-million-stock-offering-57-after-epilepsy-data/) Mar 10, 2026 Debt Financing ### [Pelthos amends Horizon venture loan, funds Loans E to H and adds Loans I and J](https://aibio.space/news/pelthos-amends-horizon-venture-loan-funds-loans-e-h-adds-loans/) Oct 30, 2026 Debt Financing ### [Repligen announces $1.0 billion private convertible notes transaction](https://aibio.space/news/repligen-announces-1-0-billion-private-convertible-notes-transaction/) Oct 30, 2026 --- Source page: https://aibio.space/news/xenon-pauses-depression-trial-enrollment-after-psychosis-reports/. Facts in aibio.space stories are checked against company filings and releases; opinion is labelled. Cite as: aibio.space, "Xenon pauses depression trial enrollment", 2026-09-18, https://aibio.space/news/xenon-pauses-depression-trial-enrollment-after-psychosis-reports/