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QR-421a

Oligonucleotide (Antisense oligonucleotide) · Gene silencing · developed by ProQR Therapeutics

Phase 1/2 Most advanced trial (none active)

PRQR Developer

1 Registered trials

What is QR-421a?

QR-421a is an RNA antisense oligonucleotide administered by intravitreal injection. It is being studied in retinitis pigmentosa, Usher syndrome type 2, and other hereditary retinal diseases.

Summary written with AI from the sources listed at the end of this page.

At a glance

Drug type: Oligonucleotide (Antisense oligonucleotide)
Mechanism: Gene silencing
Therapy area: Ophthalmology
Developer: ProQR Therapeutics (PRQR)
FDA status: Investigational, not approved in the US. Most advanced trial: Phase 1/2

🧪 Clinical trials

Trial	Phase	Condition	Status	Sponsor
NCT03780257	Phase 1/2	Retinitis Pigmentosa	Completed	PRQR

Trials of the companies BioRadar tracks, from ClinicalTrials.gov, most advanced phase first.

Conditions studied

Deaf BlindEye DiseasesEye Diseases, HereditaryEye Disorders CongenitalRetinal DiseaseRetinitis PigmentosaUsher Syndrome Type 2Vision Disorders

More from ProQR Therapeutics

QR-010 Phase 1/2 QR-1123 Phase 1/2 QR-504a Phase 1 Sepofarsen Phase 2/3

Sources

ClinicalTrials.gov NCT03780257

Updated Oct 3, 2026. Something wrong or missing? Report it on the PRQR page.

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Data: FDA (Drugs@FDA, Purple Book, DailyMed), NIH (NCI Thesaurus, GSRS, RxNorm), ClinicalTrials.gov • Informational purposes only, not medical or investment advice. • All drugs A–Z