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DTX301

Phase 3

OTC Deficiency | Gene therapy | Rare Disease |Ultragenyx Pharmaceutical Inc.|Last Updated: Jun 2, 2026

Target and mechanism

Molecular targetOTC
Target classGene
ModalityGene therapy

Success Probability

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Market & Valuation

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Trial Design

RandomizedDouble-BlindCONTROLLEDDMC
Total Trials1
Total Enrollment37

FDA Designations

No designations recorded

Clinical trial landscape

DTX301 · 1 trial · 1 indication

Phase 3 1
NCT05345171Clinical Study of DTX301 AAV-Mediated Gene Transfer for Ornithine Transcarbamylase (OTC) DeficiencyOTC Deficiency
ACTIVE NOT_RECRUITING37 Analytics
PHASE3ACTIVE NOT_RECRUITING
Clinical Study of DTX301 AAV-Mediated Gene Transfer for Ornithine Transcarbamylase (OTC) Deficiency
OTC DeficiencyUnlock trial analytics

Study Endpoints

Primary Endpoints

Plasma Ammonia as Measured by 24-Hour Ammonia (AUC0-24)
Week 36
Complete Responder Rate at the Final Study Visit After DTX301 Exposure
Up to 64 Weeks Post DTX301 Infusion

Secondary Endpoints

Percentage of Complete Responders or Responders After DTX301 Exposure
Up to 64 Weeks Post DTX301 Infusion
Annualized Event Rate of Hyperammonemic Crises (HACs) Pre-DTX301 Exposure vs Post-DTX301 Exposure
Pre-enrollment, Baseline, Up to 64 Weeks Post DTX301 Infusion
Annualized Event Rate of Interim Clinical Events (ICEs) Pre-DTX301 Exposure vs Post-DTX301 Exposure
Pre-enrollment, Baseline, Up to 64 Weeks Post DTX301 Infusion
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Study Design & Arms

AllocationRANDOMIZED
MaskingQUADRUPLE
ModelCROSSOVER
PurposeTREATMENT

Treatment Arms

ArmTypeDescription
DTX301EXPERIMENTALParticipants receive single peripheral intravenous (IV) infusion of DTX301 in solution. Between Week 36 and Week 64, participants may receive single peripheral IV infusion of placebo.
Placebo, Then DTX301EXPERIMENTALParticipants receive single peripheral IV infusion of placebo. Between Week 36 and Week 64, participants receive single peripheral IV infusion of DTX301 in solution.

Interventions

NameTypeDescription
DTX301GENETICnon-replicating, self-complementary recombinant adeno-associated virus serotype 8 (AAV8) vector
PlaceboOTHERnormal saline infusion
Oral CorticosteroidsDRUGParticipants who receive DTX301 solution will receive oral corticosteroids.
Placebo for oral corticosteroidsDRUGParticipants who receive Placebo will receive placebo corticosteroids to maintain the study blind
Sodium AcetateDRUGA tracer for the Ureagenesis Rate Test (URT)
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Eligibility Criteria

Age Range12 Years to N/A
SexALL
Healthy VolunteersNo
Study Sites16

Key Inclusion Criteria: * Confirmed clinical diagnosis of late-onset OTC deficiency with historical documentation by enzymatic (ie, liver biopsy), biochemical (ie, hyperammonemia in the presence of elevated plasma glutamine, low citrulline, and elevated spot urine orotic acid), or molecular testing...

Countries:United StatesArgentinaBrazilCanadaFranceGermanyJapanNetherlandsPortugalSpain
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Frequently asked questions about DTX301

What is DTX301 used for?

DTX301 is an investigational gene therapy being developed for the treatment of ornithine transcarbamylase (OTC) deficiency, a rare inherited metabolic disorder. It is currently in Phase 3 clinical development and has not been approved by regulatory authorities.

What does DTX301 target?

DTX301 targets the OTC gene, which encodes the enzyme ornithine transcarbamylase. The therapy is designed to deliver a functional copy of this gene to address the underlying genetic cause of OTC deficiency.

Who makes DTX301?

DTX301 is being developed by Ultragenyx Pharmaceutical Inc., a biopharmaceutical company traded on NASDAQ under the ticker symbol RARE.

What phase is DTX301 in?

DTX301 is currently in Phase 3 clinical development. It is an investigational therapy and has not yet been approved by the FDA or other regulatory agencies.

What clinical trials is DTX301 in?

DTX301 is being evaluated in a Phase 3 clinical trial with the identifier NCT05345171. This randomized, double-blind, controlled study is investigating the safety and efficacy of DTX301 in patients with OTC deficiency and is currently active but not recruiting.

Is DTX301 the same as a gene therapy for OTC deficiency?

DTX301 is an AAV-mediated gene transfer therapy specifically designed for OTC deficiency. It is the only gene therapy candidate for this condition mentioned in the available clinical trial data, and it is being studied in a Phase 3 trial.