Longboard Pharmaceuticals Announces Positive Interim Analysis Results from the Open-Label Extension (OLE) of the Phase 1b/2a PACIFIC Study Evaluating Bexicaserin in Participants with Developmental and Epileptic Encephalopathies (DEEs)

Longboard Pharmaceuticals, Inc. (Nasdaq: LBPH), a clinical-stage biopharmaceutical company focused on developing novel, transformative medicines for neurological diseases, today announced positive interim results from its ongoing 52-week open-label extension of the PACIFIC Study evaluating bexicaserin (LP352) in participants ages 12-65 years old with Developmental and Epileptic Encephalopathies (DEEs).

“We are thrilled that bexicaserin is continuing to demonstrate a sustained, durable response in seizure reduction and a favorable safety and tolerability profile across a broad range of DEE patients. These data provide further support to bexicaserin’s potential to offer a highly differentiated and best-in-class profile,” stated Dr. Randall Kaye, Longboard’s Chief Medical Officer.

“Given the tremendous unmet need in patients living with DEEs, we are committed to rapidly advancing the development of bexicaserin. We expect to provide a full analysis of participants with 12-month data early next year as they complete the OLE Study and transition to our Expanded Access Program,” Dr. Kaye continued. “With Breakthrough Therapy designation granted, we remain on track to initiate our global Phase 3 program for bexicaserin later this year.”

PACIFIC OLE Study Interim Analysis:

The PACIFIC OLE Study is a 52-week Phase 2, open-label, long-term safety study of bexicaserin in participants with a range of DEEs including Dravet syndrome (n=3), Lennox-Gastaut syndrome (n=20) and DEE Other (n=18), who completed the PACIFIC Study (n=41). The study objectives are to investigate the safety and tolerability of multiple doses of bexicaserin in participants with DEEs, and to analyze the effect of bexicaserin on the frequency of observed countable motor seizures and other seizure types. The interim analysis was conducted when participants reached the approximate 9-month point in the OLE Study.

Summary of Efficacy Results:

The median change in countable motor seizure frequency for participants in the OLE Study over an approximate 9-month treatment period was a decrease of 57.7% (n=40) from their baseline entering the PACIFIC Study.

The median change in countable motor seizure frequency from baseline for:

• participants randomized to the bexicaserin-treated group in the PACIFIC Study was a decrease of 58.2% (n=31)
• participants randomized to the placebo group in the PACIFIC Study that transitioned to bexicaserin in the OLE was a decrease of 57.3% (n=9)

Summary of Safety and Tolerability Results: