By Colin Kellaher


U.S.-listed shares Addex Therapeutics plunged nearly 60% in premarket trading Monday after the clinical-stage biopharmaceutical company reported the failure of a mid-stage study of a proposed epilepsy drug it is developing with Johnson & Johnson.

Addex said the Phase 2 study evaluating adjunctive ADX71149 administration in patients with focal onset seizures with suboptimal response to levetiracetam or brivaracetam missed its primary endpoint of time for patients to reach baseline seizure count.

Geneva-based Addex said it is still analyzing the study data, adding that it will provide more details when the analysis is complete and will work with J&J to determine the next steps for the ADX71149 program.

J&J's Janssen unit had been conducting the Phase 2 study since June 2021 under a worldwide research collaboration and license agreement and is responsible for financing the development and commercialization, if any, of ADX71149.

Addex is eligible for up to about $117 million in success-based development and regulatory milestone payments under the agreement, along with royalties on product sales.

Addex's U.S.-listed shares, which closed Friday at $16.10, were recently down 58% to $6.81 in premarket trading.


Write to Colin Kellaher at colin.kellaher@wsj.com


(END) Dow Jones Newswires

04-29-24 0737ET