Urea Cycle DisordersPhase 1/2NCT07667387
Study of LNP.UCD.ABE in Patients With Urea Cycle Disorders
A Phase 1/2 study testing LNP.UCD.ABE in people with Urea Cycle Disorders and Carbamoyl-Phosphate Synthase I Deficiency, run by Rebecca Ahrens-Nicklas at 1 site in United States.
Trial summary
This is a single-site Phase 1/2 open-label umbrella clinical trial designed to evaluate the safety, tolerability, and efficacy of a single intravenous dose of LNP.UCD.ABE in 5 pediatric subjects with severe infantile-onset UCDs. Read more about this study
- Who is it for?
- Ages 24 hours to 5 years
- Conditions the study is for
- Urea Cycle Disorders, Carbamoyl-Phosphate Synthase I Deficiency
- What is being tested?
- LNP.UCD.ABE
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 7 participants
- Where
- 1 siteUnited States
- Study dates
- 7 Aug 2026to Sep 2028
- Phase
- Phase 1/2
- Are there results?
- Not yet: the study is under way
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 24 hours to 5 years
- All sexes
- No healthy volunteers
- Child
Who may be able to join
- Diagnosis of a severe urea cycle disorder, in the judgement of the investigators.
- Molecular testing demonstrating homozygosity or compound heterozygosity for a disease-causing mutation in CPS1 that is targeted by a variant-specific version of the LNP.UCD.ABE drug product.
- Current or historical biochemical testing consistent with a urea cycle disorder
- At least one of the subject's alleles must be amenable to base editing by LNP.UCD.ABE, as assessed in vitro
- A history of an ammonia level of ≥400 μmol/L prior to age 12 months, unless a diagnosis was made prenatally and care was initiated immediately after birth
- If the patient is taking a nitrogen scavenger medication, their ammonia level may currently be in the normal range
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- If the patient is diagnosed prenatally, then personal history, family history, or analysis of mutations should indicate a high likelihood of a severe UCD.
- Subjects more than 8 weeks from the initial diagnosis of a UCD must have demonstrated:
- a persistent need for dietary protein restriction and chronic administration of a nitrogen scavenger medication, AND / OR
- a recurrent hyperammonemic event AND / OR
- a history of a hyperammonemia-induced seizure
- Weight >3.5 kg at the time of screening
- Legal guardian(s) capable of giving signed informed consent, which includes compliance with the requirements and restrictions listed in the informed consent form (ICF) and in this protocol.
Who cannot join
- Abnormal liver function, electrolyte, coagulation, or blood count laboratory values thought not attributable to the underlying urea cycle disorder;
- Demonstrated need for urgent liver transplantation due to liver failure, in the opinion of the investigators;
- Participation in a prior gene therapy trial or participation in a trial of an investigational product in the last 12 months;
- History of liver transplantation;
- Any other diseases or conditions that the investigators would consider to pose unacceptable risk to the subject;
- Inability or unwillingness to comply with the visit schedule and study assessments;
- Any genetic variation in the causative urea cycle disorder gene that, in the opinion of the investigators, may decrease the potential efficacy of the drug product;
- History of severe hypersensitivity or anaphylaxis to polyethylene glycol (PEG)-containing products, such as PEG-containing vaccines or laxatives
Trial locations and contacts
1 site in 1 country. Contact the study team or a site near you to ask about taking part.
United States1 site, 1 recruiting
- Recruiting
Children's Hospital of Philadelphia
Philadelphia, Pennsylvania, 19104
Sarah McCague, 267-426-1464, cigt@chop.edu
About this study
Official title: Master Protocol for a Phase I/II Open-label Safety and Efficacy Study of LNP.UCD.ABE, a Lipid Nanoparticle-delivered Base Editing Therapy, in Patients With Urea Cycle Disorders Due to Variants Amenable to Corrective Editing by LNP.UCD.ABE
This is a single-site Phase 1/2 open-label umbrella clinical trial designed to evaluate the safety, tolerability, and efficacy of a single intravenous dose of LNP.UCD.ABE in 5 pediatric subjects with severe infantile-onset UCDs. This is a master clinical protocol in which subjects with a variant in a urea cycle disorder (UCD) gene (CPS1, OTC, ASS1, ASL, ARG, NAGS, or SLC25A15) that is demonstrated to be amenable to corrective editing by an adenine base editor (ABE) would be eligible for enrollment.
Read the detailed description
Humans ingest protein to support growth and the synthesis of a number of key macromolecules. Nitrogen waste generated from protein catabolism is converted to ammonia, which under normal physiologic conditions is converted to urea via the urea cycle. Urea is then excreted in urine to maintain whole-body nitrogen homeostasis. Loss of function of any of the six enzymes of the urea cycle-encoded by CPS1 (carbamoyl phosphate synthetase 1), OTC (ornithine transcarbamylase), ASS1 (argininosuccinate synthetase), ASL (argininosuccinate lyase), ARG (arginase), and NAGS (N-acetylglutamate synthetase)-results in a urea cycle disorder (UCD). In addition loss of the ornithine transporter, ORNT1 (encoded by SLC25A15), can also lead to disease.
Severe UCD patients typically present as neonates and have a profound decrease in function in any one of the six enzymes of the urea cycle or a lack of function of the ornithine transporter that carries urea cycle intermediates. This results in toxic accumulation of ammonia in the blood and accumulation of specific urea cycle amino acids that aid in diagnoses and therapeutic monitoring. Patients are at risk of developing extremely elevated blood ammonia levels (hyperammonemia) that can lead acutely to coma and death and chronically to profound neurologic dysfunction.
LNP.UCD.ABE is an investigational in vivo gene editing product proposed for the treatment of hyperammonemia in patients under 5 years of age with deficiencies in enzymes or a related transporter of the urea cycle who are homozygous or compound heterozygous for a pathogenic variant in any UCD gene, including CPS1, OTC, ASS1, ASL, ARG, NAGS, and SLC25A15, that can be efficiently corrected by an adenine base editor (ABE).
Each subject will have a personalized variant-specific LNP.UCD.ABE developed and evaluated during the Screening period, which may last up to 8 months. Subjects will eligible for a lead in period to establish a stable diet. After the subject's drug is developed and lead in has been completed, the subject will be administered LNP.UCD.ABE via a single intravenous infusion. After LNP.UCD.ABE administration, participants will be followed for safety and efficacy for 52 weeks.
- Being tested
- LNP.UCD.ABE
- Medical subject headings
- Urea Cycle Disorders, Inborn
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
LNP.UCD.ABEBiological
Each subject will have a personalized variant-specific LNP.UCD.ABE developed and evaluated in real time. Each member of the LNP.UCD.ABE drug product (DP) family is a lipid nanoparticle (LNP)-based editing therapeutic comprising lipid excipients, a messenger RNA (mRNA) drug substance (DS) encoding an adenine base editor (ABE), and a single guide RNA (gRNA) DS.
| Study group | Role | What they receive |
|---|---|---|
| Experimental | Experimental | Not described Receives: Biological: LNP.UCD.ABE |
What is being measured
The primary outcome is the main question the study is designed to answer.
Safety and tolerability of a single intravenous dose of LNP.UCD.ABE
Incidence of treatment-emergent adverse events as assessed by CTCAE version 6.0 criteria at 52 weeks after LNP.UCD.ABE administration.
Measured: 52 weeks
Secondary outcomes (1)
Clinical efficacy of a single intravenous dose of LNP.UCD.ABE
The proportion of the population that can tolerate: 1. an increase in protein intake to 100% of the recommended dietary allowance (RDA) for age and/or at least a 50% reduction in the nitrogen scavenger medication dose, without an associated hyperammonemic event [defined as an ammonia level ≥ 2.5× upper limit of normal (ULN) on a non-hemolyzed specimen and the presence of symptoms of hyperammonemia], by 16 weeks after administration of LNP.UCD.ABE.
Measured: 16 weeks
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted25 Jun 2026
- Study start7 Aug 2026
- Primary completionSep 2028 (estimated)
- Study completionSep 2028 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Urea Cycle DisordersStudies of the same condition, open and under way.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase 1/2
- Primary purpose
- Treatment
- Allocation
- Not applicable
- Intervention model
- Single group
- Masking
- None (open label)
- Enrolment
- 7 participants (estimated)
Sponsor and investigators
- Lead sponsor
- Rebecca Ahrens-Nicklas
- Sponsor type
- University, hospital or other
- Collaborators
- National Institute of Neurological Disorders and Stroke (NINDS), Advanced Research Projects Agency for Health (ARPA-H)
- Responsible party
- Sponsor-investigator, Rebecca Ahrens-Nicklas, Children's Hospital of Philadelphia
- Investigators
- Rebecca Ahrens-Nicklas, M.D., Ph.D., Principal investigator, Children's Hospital of Philadelphia
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT07667387
- Sponsor's protocol ID
- UCD-101
- Status last verified
- Aug 2026
- First submitted
- 18 Jun 2026
- Last updated
- 26 Aug 2026
- Results posted
- No
- Data monitoring committee
- Yes
- FDA-regulated drug
- Yes
- FDA-regulated device
- No
- Individual data sharing
- No
Study at a glance
From the registry record, last updated by the sponsor on 26 Aug 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Master Protocol for a Phase I/II Open-label Safety and Efficacy Study of LNP.UCD.ABE, a Lipid Nanoparticle-delivered Base Editing Therapy, in Patients With Urea Cycle Disorders Due to Variants Amenable to Corrective Editing by LNP.UCD.ABE
- ClinicalTrials.gov ID
- NCT07667387
- Acronym / sponsor ID
- UCD-101
- Phase
- Phase 1/2
- Study type
- Interventional
- Recruitment status
- Recruiting
- Enrolment
- 7 participants (estimated)
- Lead sponsor
- Rebecca Ahrens-NicklasUniversity, hospital or other
- Collaborators
- National Institute of Neurological Disorders and Stroke (NINDS), Advanced Research Projects Agency for Health (ARPA-H)
- Study start
- 7 Aug 2026 (actual)
- Primary completion
- Sep 2028 (estimated)
- Study completion
- Sep 2028 (estimated)
- First posted
- 25 Jun 2026 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
This is a single-site Phase 1/2 open-label umbrella clinical trial designed to evaluate the safety, tolerability, and efficacy of a single intravenous dose of LNP.UCD.ABE in 5 pediatric subjects with severe infantile-onset UCDs. This is a master clinical protocol in which subjects with a variant in a urea cycle disorder (UCD) gene (CPS1, OTC, ASS1, ASL, ARG, NAGS, or SLC25A15) that is demonstrated to be amenable to corrective editing by an adenine base editor (ABE) would be eligible for enrollment.
Detailed description
Humans ingest protein to support growth and the synthesis of a number of key macromolecules. Nitrogen waste generated from protein catabolism is converted to ammonia, which under normal physiologic conditions is converted to urea via the urea cycle. Urea is then excreted in urine to maintain whole-body nitrogen homeostasis. Loss of function of any of the six enzymes of the urea cycle-encoded by CPS1 (carbamoyl phosphate synthetase 1), OTC (ornithine transcarbamylase), ASS1 (argininosuccinate synthetase), ASL (argininosuccinate lyase), ARG (arginase), and NAGS (N-acetylglutamate synthetase)-results in a urea cycle disorder (UCD). In addition loss of the ornithine transporter, ORNT1 (encoded by SLC25A15), can also lead to disease.
Severe UCD patients typically present as neonates and have a profound decrease in function in any one of the six enzymes of the urea cycle or a lack of function of the ornithine transporter that carries urea cycle intermediates. This results in toxic accumulation of ammonia in the blood and accumulation of specific urea cycle amino acids that aid in diagnoses and therapeutic monitoring. Patients are at risk of developing extremely elevated blood ammonia levels (hyperammonemia) that can lead acutely to coma and death and chronically to profound neurologic dysfunction.
LNP.UCD.ABE is an investigational in vivo gene editing product proposed for the treatment of hyperammonemia in patients under 5 years of age with deficiencies in enzymes or a related transporter of the urea cycle who are homozygous or compound heterozygous for a pathogenic variant in any UCD gene, including CPS1, OTC, ASS1, ASL, ARG, NAGS, and SLC25A15, that can be efficiently corrected by an adenine base editor (ABE).
Each subject will have a personalized variant-specific LNP.UCD.ABE developed and evaluated during the Screening period, which may last up to 8 months. Subjects will eligible for a lead in period to establish a stable diet. After the subject's drug is developed and lead in has been completed, the subject will be administered LNP.UCD.ABE via a single intravenous infusion. After LNP.UCD.ABE administration, participants will be followed for safety and efficacy for 52 weeks.
Study design
- Primary purpose
- Treatment
- Allocation
- Not applicable
- Intervention model
- Single group
- Masking
- None (open label)
- Number of arms
- 1
| Arm | Type | Receives |
|---|---|---|
| Experimental | Experimental | Biological: LNP.UCD.ABE |
Who may qualify
- Ages
- 24 hours to 5 years
- Sex
- All
- Healthy volunteers
- Not accepted
- Age groups
- Child
Key inclusion criteria (13 listed)
- Diagnosis of a severe urea cycle disorder, in the judgement of the investigators.
- Molecular testing demonstrating homozygosity or compound heterozygosity for a disease-causing mutation in CPS1 that is targeted by a variant-specific version of the LNP.UCD.ABE drug product.
- Current or historical biochemical testing consistent with a urea cycle disorder
- At least one of the subject's alleles must be amenable to base editing by LNP.UCD.ABE, as assessed in vitro
- A history of an ammonia level of ≥400 μmol/L prior to age 12 months, unless a diagnosis was made prenatally and care was initiated immediately after birth
Key exclusion criteria (8 listed)
- Abnormal liver function, electrolyte, coagulation, or blood count laboratory values thought not attributable to the underlying urea cycle disorder;
- Demonstrated need for urgent liver transplantation due to liver failure, in the opinion of the investigators;
- Participation in a prior gene therapy trial or participation in a trial of an investigational product in the last 12 months;
- History of liver transplantation;
- Any other diseases or conditions that the investigators would consider to pose unacceptable risk to the subject;
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| LNP.UCD.ABEEach subject will have a personalized variant-specific LNP.UCD.ABE developed and evaluated in real time. Each member of the LNP.UCD.ABE drug product (DP) family is a lipid nanoparticle (LNP)-based editing therapeutic comprising lipid excipients, a messenger RNA (mRNA) drug substance (DS) encoding an adenine base editor (ABE), and a single guide RNA (gRNA) DS. | Biological | Experimental |
Primary outcome
Safety and tolerability of a single intravenous dose of LNP.UCD.ABE
Time frame: 52 weeks
Incidence of treatment-emergent adverse events as assessed by CTCAE version 6.0 criteria at 52 weeks after LNP.UCD.ABE administration.
1 secondary outcome
Clinical efficacy of a single intravenous dose of LNP.UCD.ABE
Time frame: 16 weeks
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 26 Aug 2026.
- Individual participant dataSharing planned: No
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part.
Rebecca Ahrens-Nicklas, M.D., Ph.D. principal investigator
Children's Hospital of Philadelphia
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A Phase 1/2 study testing LNP.UCD.ABE in people with Urea Cycle Disorders and Carbamoyl-Phosphate Synthase I Deficiency, run by Rebecca Ahrens-Nicklas at 1 site in United States.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 13 inclusion and 8 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: looking for participants now, as of the sponsor's last update on 26 Aug 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in United States. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
What does this combined phase mean?
Phase 1 studies test a treatment in a small group of people for the first time or in a new way, mainly to check safety and find the right dose.
Phase 2 studies give the treatment to a larger group to see whether it has the intended effect and to keep checking safety.
Not every study follows the same path, and some studies (observational studies, device studies) have no phase.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
Contact Sarah McCague (267-426-1464, cigt@chop.edu), or a site near the patient. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Safety and tolerability of a single intravenous dose of LNP.UCD.ABE (time frame: 52 weeks). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 26 Aug 2026.