RSD1235

Astellas Pharma Inc · Phase 3 active Small molecule

RSD1235 is a Potassium channel opener Small molecule drug developed by Astellas Pharma Inc. It is currently in Phase 3 development for Atrial fibrillation (acute conversion and prevention of recurrence). Also known as: vernakalant, Kynapid.

RSD1235 is a potassium channel opener that suppresses atrial fibrillation by prolonging atrial refractoriness and reducing atrial conduction velocity.

RSD1235 is a potassium channel opener that suppresses atrial fibrillation by prolonging atrial refractoriness and reducing atrial conduction velocity. Used for Atrial fibrillation (acute conversion and prevention of recurrence).

Likelihood of approval

56.3% vs 58.3% industry baseline

If approved by FDA: likely 2028–2030

Steps remaining: NDA/BLA submission

Confidence: High

Why this estimate

• Baseline phase 3 → approval rate +58.3pp
  Industry-wide phase 3 drugs reach approval ~58.3% of the time (BIO/Informa 2023 industry benchmark across all therapeutic areas).
• Cardiovascular Phase 3 risk -2.0pp
  Modern cardiovascular outcome trials are large + long; many fail to beat aggressive standard-of-care.

Predicted approval windows by jurisdiction (conditional on FDA approval)

Regulator	Country	Likely year	Lag vs FDA
FDA	US	2028–2030	—
EMA	EU	2029–2031	+0.7 yr
MHRA	GB	2029–2031	+0.7 yr
Health Canada	CA	2029–2032	+0.9 yr
TGA	AU	2029–2032	+1.2 yr
PMDA	JP	2029–2032	+1.5 yr
NMPA	CN	2030–2033	+2.3 yr
MFDS	KR	2029–2032	+1.4 yr
CDSCO	IN	2029–2033	+1.8 yr
ANVISA	BR	2030–2033	+2.3 yr

Hover any row for the lag rationale. Lag estimates are reduced when the drug has FDA Breakthrough or EMA PRIME designation (sponsors file globally in parallel).

Estimate based on the BIO/Informa industry phase transition rates plus per-drug modifiers for therapeutic area, sponsor type, FDA designations, mechanism, and trial design. Per-jurisdiction lags from Tufts CSDD international approval studies. Not investment, clinical or regulatory advice. Methodology: /methodology#likelihood.

At a glance

Generic name	RSD1235
Also known as	vernakalant, Kynapid
Sponsor	Astellas Pharma Inc
Drug class	Potassium channel opener
Target	ATP-sensitive potassium channels (KATP)
Modality	Small molecule
Therapeutic area	Cardiovascular
Phase	Phase 3

Mechanism of action

RSD1235 works by opening ATP-sensitive potassium channels in atrial tissue, which hyperpolarizes cardiac myocytes and increases the refractory period. This electrophysiological effect reduces the ability of ectopic foci to trigger arrhythmias and slows conduction, thereby terminating or preventing atrial fibrillation episodes. The drug's selective action on atrial tissue aims to minimize ventricular side effects.

Approved indications

• Atrial fibrillation (acute conversion and prevention of recurrence)

Common side effects

• Hypotension
• Bradycardia
• Headache
• Dizziness

Key clinical trials

• RAFF4 Trial: Vernakalant vs. Procainamide for Acute Atrial Fibrillation in the Emergency Department (PHASE4)
• Vernakalant Versus Amiodarone for Post-operative Atrial Fibrillation in Cardiac Surgery Patients (PHASE3)
• Predictive Factors to Effectively Terminate Paroxysmal Atrial Fibrillation by Blocking Atrial Selective Ionic Currents (PHASE4)
• Study of Normal Conditions of Use, Dosing, and Safety of Intravenous (IV) Administration of Vernakalant (MK-6621-049)
• A Study of the Efficacy and Safety of Vernakalant Hydrochloride (MK-6621) in Patients With Atrial Fibrillation (MK-6621-010 AM4) (PHASE3)
• Vernakalant Versus Ibutilide In Recent-Onset Atrial Fibrillation (PHASE4)
• A Phase 3b Study of Vernakalant Injection in Patients With Recent Onset Symptomatic Atrial Fibrillation (AF)(MK-6621-045) (PHASE3)
• A Study Comparing Vernakalant Therapy to Amiodarone Therapy in Acute Management of Recent Onset Atrial Fibrillation (AF) (MK-6621-055) (PHASE4)

Primary sources

Every claim on this page is sourced from regulatory or scientific primary sources. See our editorial policy for full methodology.

Source	Used for
ClinicalTrials.gov	Trial enrolment, design, endpoints, results

Competitive intelligence

For the full competitive landscape — auto-detected comparators, recent regulatory actions across the set, upcoming PDUFA, patent timeline, sponsor landscape:

• RSD1235 CI brief — competitive landscape report
• RSD1235 updates RSS · CI watch RSS
• Astellas Pharma Inc portfolio CI

Frequently asked questions about RSD1235

What is RSD1235?

RSD1235 is a Potassium channel opener drug developed by Astellas Pharma Inc, indicated for Atrial fibrillation (acute conversion and prevention of recurrence).

How does RSD1235 work?

RSD1235 is a potassium channel opener that suppresses atrial fibrillation by prolonging atrial refractoriness and reducing atrial conduction velocity.

What is RSD1235 used for?

RSD1235 is indicated for Atrial fibrillation (acute conversion and prevention of recurrence).

Who makes RSD1235?

RSD1235 is developed by Astellas Pharma Inc (see full Astellas Pharma Inc pipeline at /company/astellas).

Is RSD1235 also known as anything else?

RSD1235 is also known as vernakalant, Kynapid.

What drug class is RSD1235 in?

RSD1235 belongs to the Potassium channel opener class. See all Potassium channel opener drugs at /class/potassium-channel-opener.

What development phase is RSD1235 in?

RSD1235 is in Phase 3.

What are the side effects of RSD1235?

Common side effects of RSD1235 include Hypotension, Bradycardia, Headache, Dizziness.

What does RSD1235 target?

RSD1235 targets ATP-sensitive potassium channels (KATP) and is a Potassium channel opener.

Related

• Drug class: All Potassium channel opener drugs
• Target: All drugs targeting ATP-sensitive potassium channels (KATP)
• Manufacturer: Astellas Pharma Inc — full pipeline
• Therapeutic area: All drugs in Cardiovascular
• Indication: Drugs for Atrial fibrillation (acute conversion and prevention of recurrence)
• Also known as: vernakalant, Kynapid