8-K: Rapport Therapeutics' Lead Epilepsy Drug RAP-219 Fully Enrolled in Phase 2a Trial, Topline Results Expected September 2025

Rapport Therapeutics announced its lead drug candidate, RAP-219, has fully enrolled its Phase 2a trial for refractory focal epilepsy, with topline results anticipated in September 2025, alongside positive Phase 1 safety data and a strong financial position.

Summary

• Rapport Therapeutics' Phase 2a trial of RAP-219 for refractory focal epilepsy is fully enrolled and on track to report topline results in September 2025.
• Final aggregate data from three completed Phase 1 multiple dose trials (n=64) for RAP-219 showed differentiated tolerability, with all treatment-emergent adverse events (TEAEs) being Grade 1 or 2, no serious adverse events (SAEs), and no clinically significant laboratory, vital signs, or electrocardiogram abnormalities.
• The most common TEAEs observed in Phase 1 were headache (n=12), dry mouth (n=5), brain fog (n=5), and fatigue (n=5), with only three discontinuations.
• Human PET study results confirmed TARP8, RAP-219's target, is highly expressed in the neocortex and mesial temporal lobe (where focal seizures originate) and minimally in hindbrain regions, supporting a favorable benefit/risk profile.
• RAP-219 achieved target receptor occupancy (50-70%) at doses as low as 0.25 mg in human PET studies, lower than predicted from animal models and the Phase 2a trial dose.
• The company reported $285.4 million in cash, cash equivalents, and short-term investments as of March 31, 2025, providing a cash runway expected to fund operations through the end of 2026.
• Rapport plans to initiate a Phase 2a trial for RAP-219 in bipolar mania in Q3 2025, with topline results expected in 1H 2027, and is finalizing plans for a Phase 2a trial in diabetic peripheral neuropathic pain.

Sentiment

Score: 8

Explanation: The document conveys a strong positive sentiment, highlighting successful enrollment of a key clinical trial, favorable safety data from Phase 1, and a robust financial position with a clear cash runway. The strategic pipeline expansion and precision approach further contribute to a confident outlook.

Positives

• RAP-219's Phase 2a trial for refractory focal epilepsy is fully enrolled and on schedule for topline results in September 2025, indicating efficient clinical progress.
• Phase 1 data for RAP-219 demonstrated a favorable safety and tolerability profile, with all TEAEs being mild (Grade 1 or 2) and no serious adverse events reported across 100 healthy volunteers.
• The human PET study confirmed RAP-219's precision targeting, showing high expression of TARP8 in seizure-originating brain regions and low expression in areas associated with common adverse events.
• RAP-219 achieved clinically efficacious receptor occupancy at lower doses than anticipated, suggesting potential for dose flexibility to optimize tolerability and benefit.
• The company maintains a strong financial position with $285.4 million in cash as of March 31, 2025, providing a cash runway through the end of 2026.
• RAP-219 exhibits excellent pharmaceutical properties, including once-a-day dosing, minimal drug-drug interactions, and no observed CYP interactions, which could enhance patient compliance and market potential.
• The Phase 2a trial design for focal epilepsy, utilizing the RNS System and objective biomarkers (Long Episodes), is innovative and guided by KOLs, potentially improving the reliability of results.

Risks

• Risks related to the company's research and development activities.
• Uncertainties regarding the company's ability to execute its strategy, including obtaining requisite regulatory approvals on the expected timeline, or at all.
• Uncertainties relating to preclinical and clinical development activities.
• Dependence on third parties to conduct clinical trials, manufacture product candidates, and develop/commercialize approved candidates.
• Risks related to the company's ability to attract, integrate, and retain key personnel.
• Risks associated with the company's financial condition and the need for substantial additional funds to complete development activities and commercialize product candidates, if approved.
• Risks related to regulatory developments and approval processes by the U.S. Food and Drug Administration and comparable foreign regulatory authorities.
• Risks related to establishing and maintaining intellectual property protections.
• Risks related to the competitive landscape for the company's product candidates.

Future Outlook

Rapport Therapeutics expects topline results from its Phase 2a trial of RAP-219 in refractory focal epilepsy in September 2025. The company plans to initiate a Phase 2a trial for RAP-219 in bipolar mania in Q3 2025, with results anticipated in the first half of 2027, and will provide an update on its diabetic peripheral neuropathic pain program in the second half of 2025. The current cash position is projected to fund operations through the end of 2026.

Management Comments

• "Our Phase 2a trial of RAP-219 in refractory focal epilepsy is now fully enrolled, and we remain on track to report topline results in September 2025. This will mark a major milestone for our lead program and an opportunity to demonstrate the strength of our precision neuroscience approach."
• "We're excited to share additional details about the trial ahead of the readout and honored to be joined by Dr. French, principal investigator of our RAP-219 epilepsy trial, who will provide valuable expert insight on the trial design and unmet need in focal epilepsy."
• "Today's event allows us to further underscore the potential of RAP-219 as a differentiated therapeutic with broad clinical and commercial potential."

Industry Context

Rapport Therapeutics is advancing precision medicines in neuromedicine, a field where conventional drug discovery often faces challenges due to widespread receptor distribution and associated adverse events. Their RAP technology platform aims to overcome these limitations by targeting receptor associated proteins (RAPs) for increased selectivity and neuroanatomical specificity. This approach positions RAP-219 as a potential first-in-class therapy in large market opportunities like focal epilepsy, bipolar disorder, and neuropathic pain, addressing significant unmet needs where current treatments often have limited efficacy or tolerability issues.

Comparison to Industry Standards

• RAP-219's target, TARP8, is selectively expressed in brain regions associated with focal onset seizures (neocortex and mesial temporal lobe) and has relatively low expression in hindbrain structures, which is a differentiated profile compared to pan-AMPAR antagonists like perampanel (FYCOMPA) that are widely distributed.
• Preclinical studies suggest RAP-219 has the potential to significantly improve the therapeutic index compared to other antiseizure medications (ASMs) such as Levetiracetam, Tiagabine, Ezogabine, Carbamazepine, Valproate, Lacosamide, Clobazam, Gabapentin, Lamotrigine, Topiramate, and Phenytoin, based on the corneal kindling mouse model and rotarod performance.
• The Phase 2a trial's target responder rate of 40% for a 30% reduction in Long Episodes (LEs) and a 50% reduction in clinical seizures (CSs) aligns with clinically meaningful effects, as responder rates in registrational trials for approved ASMs typically range from 25-55% for a 50% CS reduction.
• The use of the RNS System for objective iEEG data (Long Episodes) as a primary endpoint is an innovative approach, with experts like Jacqueline French, M.D., noting that changes in long episode rates correlate strongly with changes in clinical seizure rates, potentially offering a more reliable measure than patient-reported diaries.

Stakeholder Impact

• **Shareholders/Investors**: Positive news regarding clinical trial progress and financial stability may increase investor confidence and potentially lead to positive share price movement.
• **Patients (Focal Epilepsy, Bipolar Mania, Neuropathic Pain)**: The progress of RAP-219 offers potential for a new, differentiated treatment option with a favorable tolerability profile for neurological and psychiatric disorders with significant unmet needs.
• **Employees**: Continued progress in clinical development and a strong financial position provide job security and potential for growth within the company.
• **Regulatory Authorities**: The company's adherence to clinical trial timelines and transparent reporting of safety data are positive indicators for regulatory oversight.

Next Steps

• Report topline results from the RAP-219 Phase 2a trial in refractory focal epilepsy in September 2025.
• Initiate the RAP-219 Phase 2a trial in bipolar mania in Q3 2025.
• Provide an update on the diabetic peripheral neuropathic pain program in 2H 2025.
• Report topline results from the RAP-219 Phase 2a trial in bipolar mania in 1H 2027.

Key Dates

Recommendation

Keywords

Rapport Therapeutics, RAP-219, Focal Epilepsy, Bipolar Mania, Diabetic Peripheral Neuropathic Pain, TARP8, AMPAR modulator, Clinical Trial, Phase 2a, Biotechnology, Neurological Disorders, Psychiatric Disorders, Drug Development, SEC Filing, 8-K, Investor Day