Canada's Xenon touts out-of-the-blue win for its daily epilepsy pill, sending investors into a frenzy
Looking to shake up the market for seizure and epilepsy patients, Xenon Pharmaceuticals reported new topline data Monday that earned a ringing endorsement from investors.
The British Columbia-based biotech revealed its XEN1101 program passed a Phase IIb test at all three doses, producing highly statistically significant results at the mid-and high-dose levels. There’s no concrete plan yet to commercialize the drug, as Xenon still needs to meet with the FDA, but the biotech noted it expanded the study’s open-label extension to three years to obtain more follow-up data.
In response to the news, Xenon shares $XENE were trading higher by as much as 85% pre-market Tuesday. After the opening bell, Xenon stock was up by about 75% in early trading.
Researchers set out to measure the dose response trend of XEN1101 in reducing monthly focal seizures. Xenon enrolled 323 patients and randomized them into four separate groups: 112 in the high-dose 25 mg group, 51 in the mid-dose 20 mg group, 46 in the 10 mg low-dose cohort and 114 on placebo.
Each of the dose groups achieved statistical significance in reducing the median seizure frequency from baseline after 28 days. The low dose saw a 33.2% reduction, the middle dose registered a 46.4% reduction and the high dose notched a 52.8% reduction, compared to 18.2% in the placebo arm.
The p-value for the low-dose group was p=0.035, while the mid-and high-dose cohorts each reached p<0.001. XEN1101 also hit a key secondary measure looking at the proportion of patients that saw at least a 50% reduction in monthly seizures — the low dose here hit a p-value of p=0.037 while the other two groups again hit p<0.001.
Xenon highlighted that many adult focal seizure patients take many different anti-seizure medications, and about 50% of Phase IIb participants were taking at least three such drugs. The biotech is aiming to go after this heavily treated section of the market, again noting roughly half of these patients continue to experience seizures after early interventions fail.
Safety and tolerability also appeared good, Xenon said, with similar rates of serious side effects reported across all dosing levels and placebo. The biotech did note that two patients taking XEN1101 experienced urinary retention and had to be moved to lower doses, but the low overall incidence rate fell in line with forecasts. There were also no signs of pigmentation, Xenon reported.
In a call with investors Monday morning, Xenon’s chief commercial officer Chris Von Seggern said the nature of the anti-seizure medication market could allow XEN1101 to be used with a variety of other drugs, with patients typically trying generic variations before moving on to prescriptions. The program was also developed as a once-a-day pill, with Von Seggern pitching easy accessibility as appealing to patients and hopefully leading to quick uptake.
Stifel’s Paul Matteis saw Monday’s data as a big win for the biotech, noting the efficacy data “exceed our expectation.” Matteis noted the similar seizure reduction rates to the anti-seizure med Xcopri, developed by a South Korean healthcare conglomerate and approved by the FDA in November 2019.
But Matteis projects peak sales of XEN1101 should reach something closer to Vimpat, or lacosamide, which netted $1.5 billion for UCB Pharma last year.
XEN1101 is classified as an anti-epileptic drug with a mechanism of action targeting the Kv7 potassium channel. It’s a pathway the biotech touts has long been validated by the FDA, as it approved ezogabine from Valeant and GlaxoSmithKline back in 2011.