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)

• Bexicaserin achieved an overall median seizure reduction of 57.7% in countable motor seizures over an approximate 9-month treatment period
• Favorable safety and tolerability results continue to be observed
• Data to be presented at the 15^th European Epilepsy Congress in Rome, Italy
• Full 12-month OLE dataset expected early next year

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:

Continued favorable safety and tolerability results were observed in this study. 100% of PACIFIC Study completers elected to enroll in the OLE with 92.7% (38 out of 41) remaining in the ongoing open-label study. Through the approximate nine-month period, one participant discontinued due to the adverse event (AE) of lethargy and two participants discontinued by withdrawal of consent or other (relocation). The most common treatment emergent AEs in the overall group (n=41) occurring in >5% of participants were upper respiratory tract infections, COVID-19, pneumonia, sinusitis, decreased appetite, pyrexia, and weight decrease.

ABOUT THE PACIFIC STUDY AND THE OLE STUDY

The PACIFIC Study is a Phase 1b/2a double-blind, placebo-controlled clinical trial to assess the safety, tolerability, efficacy and pharmacokinetics of bexicaserin (LP352) in 52 participants between the ages of 12 and 65 years old with DEEs at 34 sites across the United States and Australia. Following a 5-week screening period and baseline evaluations, study participants initiated a dose titration over a 15-day period and subsequently continued on the highest tolerated dose throughout the maintenance period of 60 days. Following the maintenance period, participants were then titrated down, and eligible participants were given the opportunity to enroll in the 52-week open-label extension study.

ABOUT LONGBOARD PHARMACEUTICALS

Longboard Pharmaceuticals, Inc. is a clinical-stage biopharmaceutical company focused on developing novel, transformative medicines for neurological diseases. Longboard is working to advance a portfolio of centrally acting product candidates designed to be highly selective for specific G protein-coupled receptors (GPCRs). Longboard’s small molecule product candidates are based on more than 20 years of GPCR research. Longboard plans to advance bexicaserin (LP352), an oral, centrally acting 5-hydroxytryptamine 2C (5-HT2C) receptor superagonist, with no observed impact on 5-HT2B and 5-HT2A receptor subtypes, into a global Phase 3 program. The FDA has granted Breakthrough Therapy designation for bexicaserin for the treatment of seizures associated with Developmental and Epileptic Encephalopathies (DEEs) for patients two years of age and older. Earlier this year, Longboard reported positive topline data from a Phase 1b/2a clinical trial (the PACIFIC Study) evaluating bexicaserin in participants with DEEs. Longboard is also evaluating LP659, an oral, centrally acting, sphingosine-1-phosphate (S1P) receptor subtypes 1 and 5 modulator, which is in development for the potential treatment of rare neuroinflammatory conditions. Longboard recently completed a Phase 1 single-ascending dose (SAD) clinical trial for LP659 in healthy volunteers.

Bexicaserin and LP659 are investigational compounds that are not approved for marketing by the U.S. Food and Drug Administration (FDA) or any other regulatory authority.

FORWARD-LOOKING STATEMENTS

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