Short-Term Outcome of N-Carbamylglutamate in the Treatment of Acute Hyperammonemia

This is a double-blind, placebo-controlled, randomized clinical drug trial to evaluate the efficacy of NCG in the treatment of two organic acidemias (severe PA and MMA), and two urea-cycle disorders (late-onset CPSD and OTCD).

Primarily, the investigators want to determine whether NCG treatment of acute hyperammonemia in severe, neonatal-onset PA, MMA, CPSD, and OTCD is efficacious and whether it is safe. The investigators will approach this task in two ways.

1. Assess Whether NCG Treatment is Effective

The objective of this study is to assess whether NCG is efficacious in treating hyperammonemia and improving outcome:

The investigators will realize this goal by randomizing each hyperammonemic episode from every subject to NCG (NCG)+standard treatment (NCG-STD) versus placebo+standard treatment (PLBO-STD) and subsequently gauging response with the primary outcome of plasma ammonia levels, in addition to the plasma glutamine, the Functional Status Scale, and the length of hospitalization.
2. Safety

The primary safety outcome of the study will be the assessed via the rate of Serious Adverse Events (SAEs), defined in this study as death or substantial prolongation of hospitalization, as patients are hospitalized as part of the entry to the study.

Safety tests consisting of complete blood count (CBC), liver and kidney function tests, and coagulation profile (PTT/INR) will be performed before treatment, between days 3-5 of treatment, and just prior to discontinuation of NCG. An electrocardiogram will be performed before treatment and on the third day of treatment or before discharge if earlier.

• Carbaglu (Drug), also known as Carglumic Acid: Carbaglu Chemical Composition: N-carbamoyl-L-glutamic acid (NCG) The daily dose will be 150 mg/kg/ day or 3.3 g/m2/day for patients >15 kg and will be administered for 7 days or until discharge, whichever is sooner. The doses are to be divided into 2 equal doses and administered orally or enterally by nasogastric or gastrostomy tube. Standard of care will prevail when choosing the mode of drug administration. The tablets must be dispersed in a minimum of 2.5-10 ml of water and ingested immediately or administered by fast-push through a syringe via a nasogastric or gastrostomy tube. The suspension has a slightly acidic taste.
• Placebo (Drug): Placebo that looks/tastes the same as NCG and is administered on the same schedule as the NCG intervention

Primary outcomes

• Time to the Primary Outcome (Earlier of Ammonia <50 µmol/L or Hospital Discharge) [Average of all measurements of hyperammonemia, for up to 7 days]: The composite primary intention to treat (ITT) outcome of the earlier of time to reach an ammonia level of ≤50 µmol/L or hospital discharge. Data presented as a hazard ratio based on the time to reach an ammonia level of ≤50 µmol/L. The outcome measure was a survival analysis based on time to reach the earlier of an ammonia level of ≤50 µmol/L or time to discharge, which was considered to be a point where the patient was no longer at risk of neurological injury from ammonia. The outcome of survival analysis was a hazard ratio reflecting the ratio of probabilities in each group (drug vs placebo) of reaching the earlier of an ammonia level of ≤50 µmol/L or discharge. We measured multiple post-treatment ammonia levels at uncontrolled times during an episode, so it is difficult to compute a meaningful average that would not be biased by the frequency and timing of ammonia testing during episodes.

Sex: All, ages: 1 Week to 99 Years

Inclusion Criteria

o Aged older than 1 week with an established diagnosis of CPSD or OTCD (as follows):

* Diagnosed with late-onset CPSD confirmed by detection of pathogenic mutation(s), and/or decreased (<20% of control) CPS enzyme activity in liver OR
* Diagnosed with late-onset OTCD by detection of pathogenic OTC mutation, OR decreased (<20% of control) OTC enzyme activity in liver OR elevated urinary orotate (greater than 20 µM/mM) following allopurinol loading with the absence of argininosuccinic acid

AND: Subject or subject's first-degree relative had plasma ammonia level ≥100 μmol/L >1 week of age

OR

o An established diagnosis of PA or MMA (as follows):

\- Diagnosed with PA by semi-quantitative urine organic acid analysis, defined as the presence of elevated Methylcitric acid and normal methylmalonic acid levels and no evidence of biotin related disorders in the organic acid analysis

OR

\- Diagnosed with MMA by semi-quantitative urine organic acid analysis, defined as an elevation of methylmalonic acid and no evidence of vitamin B12 dependent disorder on plasma amino acid analysis (B12 dependency is defined by documented B12 responsiveness)

AND: Subject or subject's first-degree relative had plasma ammonia level at any time ≥100 μmol/L

* Able to receive medications orally, by nasogastric (NG)-tube or by gastric (G)-tube
* No concomitant illness which would preclude safe participation as judged by the investigator
* If post-menarcheal must have a negative pregnancy test prior to administration of study drug at each episode
* Signed informed consent by the subject or the subject's legally acceptable representative

Exclusion Criteria

* Administration of NCG within 7 days of participation in the study
* Use of any other investigational drug, biologic, or therapy
* Planned participation in any other clinical trial
* Diagnosis of any medical condition causing hyperammonemia which is not PA/MMA, CPSD or OTCD. Other urea cycle disorders will be excluded from this study
* Any clinical or laboratory abnormality or medical condition that, at the discretion of the investigator, may put the subject at additional risk by participating in this study
* Has had a liver transplant
* Is not expected to be compliant with this study in terms of returning to the site for subsequent episodes of hyperammonemia crises
* Is pregnant

Participant flow

Outcome results

• Time to the Primary Outcome (Earlier of Ammonia <50 µmol/L or Hospital Discharge) (Primary), Number, Hazard Ratio: PA/MMA Episodes 1.37 (0.88 to 2.13); CPS1D/OTCD Episodes 0.79 (0.22 to 2.81)

Adverse events

Time frame: During each hospitalization, once per day, up to 7 days.

Serious adverse events by term

Other adverse events by term

• Results publication: Amari S, Shahrook S, Namba F, Ota E, Mori R. Branched-chain amino acid supplementation for improving growth and development in term and preterm neonates. Cochrane Database Syst Rev. 2020 Oct 2;10(10):CD012273. doi: 10.1002/14651858.CD012273.pub2. PMID 33006765

• Study Protocol and Statistical Analysis Plan (PDF, 2020-05-01)

• Mendel Tuchman, MD, Principal investigator, Children's National Research Institute