JPRN-jRCT2041260070 Radiprodil Seizures Clinical Landscape Report 2026: Design, Endpoints, Sponsor and Readout Outlook

Turn a newly registered trial into a decision-ready landscape. This focused report examines JPRN-jRCT2041260070—A Multinational, Multicenter Study With an Open-Label Phase 1b and a Randomized, Double-Blind, Placebo-Controlled Phase 3 Followed by an Open-Label Extension to Assess the Efficacy, Safety, Tolerability, and Pharmacokinetics of Radiprodil in Participants With GRIN-Related Neurodevelopmental Disorder—using PatSnap Clinical Trials MCP for protocol design and endpoint evidence, Drug & Asset MCP for mechanism and development context, and Company & Deal Intelligence MCP for sponsor background. Explore PatSnap MCP Servers to reproduce the workflow inside an AI research process.

MCP evidence snapshot: 20 July 2026; publication date: 20 July 2026. Trial records can change after the snapshot and should be rechecked before operational decisions.

Why JPRN-jRCT2041260070 is a hot trial to watch

Seizures is increasingly segmented by mechanism, biomarker, treatment setting, geography and endpoint architecture. JPRN-jRCT2041260070 is notable because it evaluates Radiprodil in a Phase 3 design while パートA（適格発作コホート）：維持期間中（1週目から12週目まで）に日々の発作記録用eDiaryに記録された、計数可能な運動発作の頻度（28日毎） パートA（適格発作が認められない補助コホート）：AE、SAE、ADR（頻度、種類、重症度、期間） パートB（非盲検継続投与試験）：AE、SAE、ADR（頻度、種類、重症度、期間） serves as the main decision variable. The critical question is whether the protocol can convert its rationale into a clinically interpretable and operationally credible readout.

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Trial landscape snapshot

Design and endpoint interpretation

The phase label is only the starting point. Allocation is Randomized, masking is Double, and the intervention model is Parallel Assignment. Planned enrollment of 10 participants across Singapore, Taiwan Province, Italy, Netherlands, Germany, Poland, United Kingdom, South Korea, Slovenia, France, Canada, United States, Australia, Japan, Spain, Belgium shapes statistical precision, execution risk and external validity. Interpretation should account for baseline risk, prior therapy, assessment schedule, missing-data handling and clinical relevance—not only statistical significance.

• Primary: パートA（適格発作コホート）：維持期間中（1週目から12週目まで）に日々の発作記録用eDiaryに記録された、計数可能な運動発作の頻度（28日毎） パートA（適格発作が認められない補助コホート）：AE、SAE、ADR（頻度、種類、重症度、期間） パートB（非盲検継続投与試験）：AE、SAE、ADR（頻度、種類、重症度、期間）
• Primary: PART A - PHASE 3 RANDOMIZED QUALIFYING SEIZURES COHORT:Countable motor seizure (CMS; defined here) frequency (per 28 days) during the Maintenance Period (Weeks 1 through 12), as captured in the daily seizure eDiary PART A - PHASE 3 RANDOMIZED WITHOUT QUALIFYING SEIZURES AUXILIARY COHORT:AEs, SAEs, and ADRs (frequency, type, severity, and duration) PART B OLE - PHASE 3 RANDOMIZED COHORTS: AEs, SAEs, and ADRs (frequency, type, severity, and duration)
• Secondary: PART A - PHASE 3 RANDOMIZED QUALIFYING SEIZURES COHORT: - Proportion of participants with >=50% reduction in CMS frequency (per 28 days) from baseline (the last 4 weeks prior to randomization) to the entire Maintenance Period (Weeks 1 through 12), as captured in the daily seizure eDiary - Change in the number of CMS-free days (per 28 days) from baseline (the last 4 weeks prior to randomization) to the entire Maintenance Period (Weeks 1 through 12), as captured in the daily seizure eDiary - Cumulative distribution of percent reduction in seizure frequency from Baseline to the entire Maintenance Period (Weeks 1 through 12) - GRIN-NDD-specific CGI-C (GRIN-CGI-C) evaluated at the end of the Maintenance Period (Week 12) relative to baseline for relevant domains, including expressive communication, receptive communication, fine motor, gross motor, and dysregulated behavior - Change from baseline to the end of the Maintenance Period (Week 12) in the ABC-2C irritability subscale score - Change from baseline to the end of the Maintenance Period (Week 12) in the Vineland Adaptive Behavior Scale, Third Edition (VABS-3) Daily Living personal subdomain score PART A - PHASE 3 RANDOMIZED WITHOUT QUALIFYING SEIZURES AUXILIARY COHORT: - GRIN-CGI-C evaluated at the end of the Maintenance Period (Week 24) relative to baseline for relevant domains, including expressive communication, receptive communication, fine motor, gross motor, and dysregulated behavior - Change from baseline to the end of the Maintenance Period (Week 24) in the ABC-2C irritability subscale score - Change from baseline to the end of the Maintenance Period (Week 24) in the VABS-3 Daily Living personal subdomain score PART B OLE - PHASE 3 RANDOMIZED COHORTS: - Percent change in the CMS frequency per 28 days from baseline to each 12-week interval in the open-label extension (OLE) through the end of the OLE, as captured in the daily seizure eDiary - Change in the number of CMS-free days per 28 days from baseline to each 12-week interval in the OLE through the end of the OLE, as captured in the daily seizure eDiary - Change from baseline to each open-label treatment visit through the end of open-label treatment in the ABC-2C irritability subscale score, the VABS-3 Daily Living personal subdomain score, and the GRIN-CGI-C scale for relevant domains (including expressive communication, receptive communication, fine motor, gross motor, and dysregulated behavior)
• Secondary: パートA（適格発作コホート）： ・日々の発作記録用eDiaryに記録された、ベースライン（無作為割り付け前の直近4週間）から全維持期間（1週目から12週目）までのCMS頻度（28日毎）が、50%以上減少した被験者の割合 ・日々の発作記録用eDiaryに記録されたベースライン（無作為割り付け前の直近4週間）から全維持期間（1週目から12週目）までのCMS無発生日数（28日毎）の変化量 ・ベースラインから全維持期間（1週目から12週目）までの発作頻度減少率の累積分布 ・表出的コミュニケーション、受容的コミュニケーション、微細運動、粗大運動、調節異常行動を含む関連領域について維持期間終了時（12週目）に評価されたGRIN-NDD特異的CGI-C (GRIN-CGI-C) の、ベースラインからの変化量 ・ABC-2C易刺激性サブスケールスコアのベースラインから維持期間終了時（12週目）までの変化量 ・Vineland適応行動尺度第3版 (VABS-3) 日常生活スキルパーソナルサブドメインスコアの、ベースラインから維持期間終了時（12週目）までの変化量 パートA（適格発作が認められない補助コホート）： ・表出的コミュニケーション、受容的コミュニケーション、微細運動、粗大運動、調節異常行動を含む関連領域について維持期間終了時（24週目）に評価されたGRIN-CGI-Cの、ベースラインからの変化量 ・ABC-2C易刺激性サブスケールスコアのベースラインから維持期間終了時（24週目）までの変化 ・VABS-3日常生活スキルパーソナルサブドメインスコアのベースラインから維持期間終了時（24週目）までの変化量 パートB（非盲検継続投与試験）： ・日々の発作記録用eDiaryに記録された、ベースラインから非盲検継続投与(OLE) 期間終了までの12週間毎の各間隔までの、28日毎のCMS頻度の変化率 ・日々の発作記録用eDiaryに記録された、ベースラインからOLE終了までの12週間毎の各間隔までの、28日毎のCMS無発生日数の変化量 ・ABC-2C易刺激性サブスケールスコア、VABS-3日常生活スキルパーソナルサブドメインスコア、及びGRIN-CGI-C尺度に関連する領域（表出的コミュニケーション、受容的コミュニケーション、微細運動、粗大運動、調節異常行動を含む）における、ベースラインから非盲検治療終了までの各非盲検治療来院時における変化量

Benchmark readouts in the surrounding field

• A Randomized, Double-Blind, Placebo-Controlled, Parallel-Group Study of RDX-002 on Postprandial Triglycerides in Patients Discontinuing the Glucagon-like Peptide-1 (GLP-1) Agonists, Semaglutide, or Tirzepatide for the Treatment of Obesity (Phase 2): Incremental Postprandial Triglycerides (TG)(Mean) = 43.81 percent change (Standard Deviation, 92.373); Incremental Postprandial Triglycerides (TG)(Mean) = -51.91 percent change (Standard Deviation, 72.293)
• A Phase II Study to Evaluate the Delay in Ovulation Following Oral Levonorgestrel Plus Meloxicam Compared to Placebo in Obese But Normal Menstruating Women (Phase 2): Interval From First Dose to Evidence of Ovulation.(Mean) = 2.67 Number of days (Standard Deviation, 1.53); Interval From First Dose to Evidence of Ovulation.(Mean) = 4.0 Number of days (Standard Deviation, 0)
• A Phase 2, Parallel-Group, Double-Blind Study to Investigate Weight Management With LY3841136 Compared With Placebo in Adult Participants With Obesity or Overweight (Phase 2): Percent Change From Baseline in Body Weight at Week 48(Least Squares Mean) = -0.4 percent change (Standard Error, 0.91); Percent Change From Baseline in Body Weight at Week 48(Least Squares Mean) = -9.4 percent change (Standard Error, 1.60)

These indexed results are contextual benchmarks, not direct head-to-head evidence. Population, treatment line, endpoint definitions, follow-up and analysis sets may differ. Their value is to clarify the type and magnitude of evidence already visible in the competitive landscape.

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Asset and sponsor context

Drug & Asset context: Radiprodil (Phase 3; GluN2B)

Company & Deal Intelligence context: GRIN Therapeutics, Inc. — United States — http://grintherapeutics.com

The sponsor profile matters because scientific rationale alone does not determine development value. Manufacturing readiness, portfolio fit, geographic reach, partnering capacity and the ability to fund confirmatory development can decide whether a positive signal becomes a competitive asset.

White space around this program

• Sharper patient selection: prospective biomarker or phenotype definitions that identify who is most likely to benefit.
• Clinically interpretable endpoints: outcomes connecting activity with function, symptoms, survival or treatment burden.
• Sequencing evidence: comparative data after the most relevant contemporary standard of care.
• Broader external validity: evidence across additional geographies, demographic groups and real-world settings.
• Operational differentiation: a development path that closes the readout gap without sacrificing safety or durability.

What to monitor next

Monitor recruitment, enrollment changes, protocol amendments, endpoint hierarchy, primary-completion timing, first result indexing, asset ownership and sponsor partnerships. A change in endpoint, population or ownership can alter probability of success before a headline data release.

Bottom line

JPRN-jRCT2041260070 is a focused lens on Seizures development. Its value will be determined by whether Radiprodil can convert the current design into evidence that is clinically meaningful, operationally credible and differentiated from indexed benchmark readouts.

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