8-K: Rapport RAP-219 Phase 2a Success in Focal Seizures

Rapport Therapeutics announced positive topline results from its Phase 2a clinical trial of RAP-219 for drug-resistant focal onset seizures, demonstrating statistically significant efficacy and good tolerability.

Summary

• RAP-219 Phase 2a trial for drug-resistant focal onset seizures met primary and key secondary endpoints with high statistical significance.
• 85.2% of patients achieved a 30% reduction in long episodes (LEs) from baseline (p<0.0001) over the 8-week treatment period.
• 72.0% of patients achieved a 50% reduction in clinical seizures from baseline (p<0.0001).
• 24% of patients achieved seizure freedom for the 8-week treatment period (p<0.0001).
• Median reduction in LE frequency from baseline was 71.0% (p=0.0001), and median reduction in clinical seizure frequency was 77.8% (p=0.01).
• RAP-219 was generally well-tolerated, with the majority of treatment-emergent adverse events (TEAEs) being mild or moderate, and a low discontinuation rate of 10% (3 patients).
• No serious adverse events were reported during the treatment period.
• Common TEAEs (≥10% incidence) included dizziness (26.7%), headache (16.7%), fatigue (13.3%), fall (10.0%), nausea (10.0%), and somnolence (10.0%).
• Plans include an end-of-Phase 2 meeting with the U.S. FDA in Q4 2025 and initiation of two Phase 3 pivotal trials in Q3 2026.
• Development of a long-acting injectable (LAI) formulation of RAP-219 continues, with initial pharmacokinetic results expected in 2027.
• RAP-219 is also being evaluated in a Phase 2 trial for bipolar mania (topline results H1 2027) and diabetic peripheral neuropathic pain (update expected later in 2025).

Sentiment

Score: 9

Explanation: The trial results are overwhelmingly positive, demonstrating strong efficacy and a favorable safety profile for a drug targeting a significant unmet medical need. The clear path to Phase 3 and additional pipeline potential contribute to a very strong positive sentiment.

Positives

• Achieved statistically significant results for primary long episode (LE) endpoints (p<0.0001).
• 85.2% of patients achieved 30% reduction in LEs from baseline.
• Achieved statistically significant results for key secondary endpoints of clinical seizures (p<0.0001).
• 72.0% of patients achieved 50% reduction in clinical seizures from baseline.
• 24% of patients achieved seizure freedom for the 8-week treatment period.
• Median reduction in LE frequency from baseline was 71.0%.
• Median reduction in clinical seizure frequency from baseline was 77.8%.
• RAP-219 was generally well-tolerated with a low discontinuation rate (10%).
• No serious adverse events were reported during the treatment period.
• All TEAEs reported were mild (78.5%) or moderate (21.5%) in severity.
• Data supports advancement into Phase 3 registrational trials.
• RAP-219 is a potential first-in-class, investigational TARPg8-specific AMPAR negative allosteric modulator, offering a novel mechanism of action.
• Development of a long-acting injectable (LAI) formulation has the potential to improve patient adherence and expand clinical utility.
• RAP-219 demonstrates 'pipeline-in-a-product' potential, with ongoing evaluation for bipolar mania and diabetic peripheral neuropathic pain.

Negatives

• Three patients (10%) discontinued treatment due to treatment-emergent adverse events (TEAEs).
• The most common TEAEs reported (≥10% incidence) were dizziness (26.7%), headache (16.7%), fatigue (13.3%), fall (10.0%), nausea (10.0%), and somnolence (10.0%).

Risks

• Risks relating to research and development activities.
• Ability to execute strategy, including obtaining requisite regulatory approvals on the expected timeline, if at all.
• Uncertainties relating to preclinical and clinical development activities.
• Dependence on third parties to conduct clinical trials, manufacture product candidates, and develop/commercialize them, if approved.
• Ability to attract, integrate, and retain key personnel.
• Financial condition and need for substantial additional funds to complete development activities and commercialize a product candidate, if approved.
• Risks related to regulatory developments and approval processes of 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 product candidates.

Future Outlook

Rapport Therapeutics plans to advance RAP-219 into two Phase 3 pivotal trials for focal onset seizures in Q3 2026, following an end-of-Phase 2 FDA meeting in Q4 2025. The company expects further data releases for the Phase 2a trial in 2026, preliminary results from a long-term safety trial in H2 2026, and initial pharmacokinetic results for a long-acting injectable formulation in 2027. RAP-219's Phase 2 trial for bipolar mania is on track for H1 2027 topline results, with an update on a diabetic peripheral neuropathic pain trial expected later in 2025.

Management Comments

• Jacqueline French, M.D., principal investigator, stated that the trial represents the first time a novel antiseizure medication was evaluated in focal seizure patients using the RNS system with an objective biomarker, and the magnitude of reduction gives confidence in RAP-219's potential as a highly effective ASM for drug-resistant focal seizure patients.
• Abe Ceesay, CEO, commented that the efficacy and tolerability profile demonstrate RAP-219's potential as an important treatment, and with its emerging best-in-class profile, it could address a significant unmet need and support broad adoption among epileptologists and neurologists.
• Dr. Jeffrey Sevigny, CMO, expressed excitement over the strength of the data in both electrographic biomarker and clinical seizure reductions, providing confidence to progress RAP-219 into its next stage of clinical development and into Phase 3 trials given the persistent unmet need in focal epilepsy.

Industry Context

Up to 40% of patients with focal epilepsy remain drug-resistant despite available therapies, indicating a significant unmet need for new effective anti-seizure medications with novel mechanisms of action. RAP-219, as a potential first-in-class TARPg8-specific AMPAR negative allosteric modulator, aims to address this by selectively targeting specific brain regions (hippocampus and neocortex) where seizures originate, while minimizing expression in the hindbrain to potentially reduce adverse events. This precision approach could offer a differentiated profile compared to traditional neuroscience medications.

Comparison to Industry Standards

• The trial represents the first time a novel antiseizure medication was evaluated in focal seizure patients using the RNS system with an objective biomarker of seizure activity, setting a new benchmark for clinical trial design in this area.
• RAP-219's efficacy, including 77.8% median clinical seizure reduction and 24% seizure freedom, positions it favorably against existing anti-seizure medications (ASMs) where 30-40% of patients remain drug-resistant.
• The tolerability profile, with no serious adverse events and a low discontinuation rate, suggests an improvement over many current ASMs that are associated with burdensome side-effects like sedation, ataxia, and cognitive problems.
• The company believes RAP-219 has an 'emerging best-in-class profile' due to its targeted mechanism, once-daily dosing, low risk of drug-drug interactions, and long half-life, addressing limitations of current ASMs such as complicated administration and risk of breakthrough seizures.

Stakeholder Impact

• Shareholders: Positive impact due to strong clinical trial results, potential for future drug approval, and expanded pipeline, which could increase stock value.
• Patients with Drug-Resistant Focal Onset Seizures: Significant positive impact as RAP-219 shows potential to be a highly effective new treatment option, offering meaningful benefits and the promise of seizure freedom where current therapies fail.
• Healthcare Providers (Epileptologists, Neurologists): Potential for a new, differentiated anti-seizure medication with a novel mechanism of action and favorable tolerability profile, addressing an unmet need.
• Employees: Positive outlook due to successful clinical development and advancement of the lead product candidate, indicating job security and potential for growth.
• Regulatory Authorities (FDA): Will be engaged in the end-of-Phase 2 meeting and subsequent Phase 3 trial reviews.

Next Steps

• Hold an end-of-Phase 2 meeting with the U.S. Food and Drug Administration in Q4 2025.
• Initiate an open-label long term safety trial for RAP-219 by the end of 2025.
• Present additional efficacy analyses and 8-week follow-up results from the Phase 2a trial in 2026.
• Expect preliminary results of the open-label long term safety trial in H2 2026.
• Initiate two Phase 3 pivotal trials for RAP-219 in Q3 2026.
• Report initial pharmacokinetic results for the long-acting injectable (LAI) formulation of RAP-219 in 2027.
• Expect topline results for the Phase 2 trial of RAP-219 in bipolar mania in H1 2027.
• Expect an update on the plan and timeline for initiation of a Phase 2 trial in diabetic peripheral neuropathic pain later in 2025.

Key Dates

Recommendation

The positive topline Phase 2a results for RAP-219 in drug-resistant focal onset seizures are highly significant, demonstrating strong efficacy (high responder rates, substantial seizure reduction, and a notable percentage achieving seizure freedom) coupled with a favorable tolerability profile (no SAEs, low discontinuation). This positions RAP-219 as a potential best-in-class treatment for a patient population with significant unmet needs. The clear development pathway to Phase 3, the 'pipeline-in-a-product' potential across multiple indications, and the development of a long-acting injectable formulation further enhance the long-term value proposition. While future capital raises are anticipated, the current cash runway through 2026 provides stability for near-term milestones. These results significantly de-risk the asset and suggest substantial commercial potential, making it a compelling investment opportunity.

Keywords

Rapport Therapeutics, RAP-219, Focal Onset Seizures, Epilepsy, Phase 2a, Clinical Trial, Drug-Resistant Seizures, Biotechnology, Neuroscience, AMPAR, TARPg8, Bipolar Mania, Diabetic Peripheral Neuropathic Pain, FDA, Long-Acting Injectable