Xenon Pharmaceuticals (XENE) provided investors with two very different updates on the same drug, and Wall Street paid attention to the troubling one.
Shares of the Vancouver-based biotech company plummeted as much as 30% on Sept. 18 after Xenon temporarily halted recruitment of additional patients in late-stage depression trials of azetukalner, its flagship investigational medication.
The drugmaker indicated that adverse neuropsychiatric events occurred in its continuing psychiatry program, Reuters reported.
The occurrences included disorientation, speech issues, difficulty with coordination, and a tiny number of instances of psychosis, Reuters said. They occurred at a low incidence and were defined as short-lived and reversible.
But the same business report also included a possibly far bigger development in the long run.
Xenon said it has submitted a New Drug Application to the Food and Drug Administration for azetukalner in focal seizures, moving the drug closer to a potential commercial launch in epilepsy.
That leaves investors with two very different questions to weigh: how much the psychiatry setback damages azetukalner’s broader opportunity and whether the epilepsy program remains intact.
Xenon’s depression trials hit unexpected safety problem
Xenon said azetukalner’s side effects were consistent with its known pharmacology and safety profile but had not emerged in its previous Phase 2 depression research. Xenon is currently assessing potential dose changes that may enhance tolerability.
- Drug: Azetukalner
- Indications affected: Major depressive disorder and bipolar depression
- Action: Temporary pause in new enrollment
- Existing patients: Remain active
- X-NOVA2 enrollment: About 360 patients
- Expected data: Q1 2027
That difference is noteworthy. This is not a complete termination of the psychiatric program. Instead, Xenon is halting new enrollment but will continue to care for and track existing patients.
Its X-NOVA2 trial in major depressive illness has already recruited about 360 patients, or about 80% of the initial goal of 450 patients. “Population should still be sufficiently powered to detect a clinically meaningful effect on the primary endpoint of the trial,” Xenon stated.
Topline data is now expected in the first quarter of 2027.
The FDA is still reviewing Xenon’s biggest opportunity
The sell-off is exacerbated by the distinct issue of Xenon’s epilepsy program.
Xenon has filed for FDA clearance of azetukalner for focal seizures, a kind of epilepsy where seizures originate in one part of the brain. Xenon’s Phase 2b X-TOLE trial and Phase 3 X-TOLE2 research underpin the application.
The 25-milligram dosage of X-TOLE2 resulted in a median decrease of 53.2% in monthly focal-onset seizure frequency, compared to 10.4% for placebo. The 15-milligram arm showed a 34.5% decline.
Azetukalner was usually well tolerated in those epilepsy tests, and its safety profile was comparable with prior research, Xenon also noted. The company says its epilepsy program now contains more than 1,500 patient-years of safety and exposure data.
Chief Medical Officer Chris Kenney said Xenon remains confident in azetukalner’s epilepsy profile based on its efficacy and safety data.
That helps explain why some analysts see the market’s response as possibly isolating the psychiatry prospect from the basic epilepsy argument.
Wall Street debates how much of Xenon’s value disappeared
Before the trial suspension, the value of Xenon had surged to almost $5 billion, with investors betting on azetukalner’s potential in several neurological and psychiatric illnesses.
The Sept. 18 sell-off effectively removed a large amount of that value in a single session.
TD Cowen analyst Joseph Thome, quoted by BioPharma Dive, said azetukalner’s fall was “overdone,” while RBC Capital Markets analyst Brian Abrahams predicted azetukalner could still bring in $1.7 billion in annual epilepsy sales.
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Wall Street lacks universal consensus.
Deutsche Bank lowered Xenon to Hold from Buy and reduced its price target to $46 from $90 after the safety update. But Stifel kept its Buy rating and $86 price target following the interruption.
The divide represents the key dilemma for XENE investors.
There is no longer any question that azetukalner works. What remains to be seen is how much of the medicine’s value should come from epilepsy and how much investors should still allocate to depression.
Xenon still has financial room to work through the setback
Another key issue is Xenon’s balance sheet.
Xenon had cash, cash equivalents, and marketable securities of about $1.3 billion as of the end of the first quarter, which management claimed could support operations beyond 2029.
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That allows the firm to work through the psychiatric safety problems while continuing with epilepsy research and preparing for a potential commercial launch.
Xenon is also conducting additional azetukalner trials, including X-TOLE3 for focal seizures and X-ACKT for primary generalized tonic-clonic seizures.
The corporation is not in imminent need of cash due to the setback in its depression program. Still, the next few months will probably reveal whether investors see azetukalner as a potential multi-indication blockbuster prospect or just an epilepsy medicine.
Xenon’s stock crash may have changed what investors are paying for
The 30% fall is a big reset of expectations.
Prior to the stoppage, investors had been willing to put a meaningful value on azetukalner’s prospects in epilepsy, major depressive disorder, and bipolar depression.
Now the psychiatric opportunity is far less clear. Yet Xenon’s epilepsy program has not stalled, and its FDA filing will move forward.
That is a unique situation for XENE shares. The firm recently experienced a major clinical blow, yet its most advanced medicine also achieved one of the most crucial regulatory milestones in its history.
The next trigger for investors may be less about whether azetukalner finally works and more about whether the FDA believes the epilepsy findings are robust enough to secure clearance.
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