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Chemical structure of N-acetyl-leucine. (a) Stereochemistry of the enantiomers. (b) Amide resonance structures showing similarity to an imine. Extending from the tetrahedral chiral carbon is a solid wedge to indicate a bond projecting above the plane of the paper and a hashed wedge to indicate a bond projecting below the plane of the paper. https://doi.org/10.1371/journal.pone.0229585.g001
Source publication
The enantiomers of many chiral drugs not only exhibit different pharmacological effects in regard to targets that dictate therapeutic and toxic effects, but are also handled differently in the body due to pharmacokinetic effects. We investigated the pharmacokinetics of the enantiomers of N-acetyl-leucine after administration of the racemate (N-acet...
Contexts in source publication
Context 1
... N-acetyl-leucine is an analogue of the alpha amino acid leucine, and because it retains leucine's stereocentre it exists as a pair of enantiomers (Fig 1). Enantiomers are isomers, compounds with the same molecular formula but which differ in the arrangement of their atoms in space, having one chiral stereocentre with four different substituents that yields two nonsuperimposable mirror image molecules (Fig 1). ...
Context 2
... N-acetyl-leucine is an analogue of the alpha amino acid leucine, and because it retains leucine's stereocentre it exists as a pair of enantiomers (Fig 1). Enantiomers are isomers, compounds with the same molecular formula but which differ in the arrangement of their atoms in space, having one chiral stereocentre with four different substituents that yields two nonsuperimposable mirror image molecules (Fig 1). Often the pharmacological activity of a drug resides with a single enantiomer because living systems are chiral and formed from chiral constituents [14]. ...
Context 3
... determine whether the enantiomers of N-acetyl-leucine have different pharmacokinetics, we orally dosed mice with either a racemate or the L-enantiomer (Fig 2 and S1 Fig). Following an oral dose of N-acetyl-DL-leucine (100 mg/kg and 10 mg/mL), in the plasma, the concentration of the D-enantiomer was greater than the L-enantiomer at all time points (Fig 3A). ...
Context 4
... an oral dose of the purified L-enantiomer at 100 mg/kg and 10 mg/mL, the concentration of the L-enantiomer was greater at all time points (Fig 3C). Quantitatively, for the D-and L-enantiomers, respectively, had a C max of 436 ng/mL versus 16900 ng/mL (Fig 5A and Table 1) and an AUC of 573 h � ng/mL and 11400 h � ng/mL ( Fig 5D and Table 1). As with administration of the racemate (Fig 3A and 3B), after dosing with purified L-enantiomer, the elimination rate was similar for both enantiomers, indicated by the linear and parallel curves on a semilog graph (Fig 3D) and was well-fit with a noncompartmental model giving a k e of 1.7 h -1 for the D-enantiomer and 2.4 −1 for L-enantiomer ( Fig 5C and (Fig 5G) with a last concentration of 16 ng/mL and 168 ng/mL (Fig 5F). ...
Context 5
... way to compare administration of the racemate to the purified L-enantiomer on the pharmacokinetics of the enantiomers was to calculate the ratio of enantiomers in regard to C max and AUC. As we verified the administered compound to be a true racemate (50% each enantiomer; S1 Fig), deviations from a ratio of 1 reveal significantly different pharmacokinetics between the D-and L-enantiomers. When administered as the racemate, the ratio of D/L enantiomer was about 25 for both C max (Fig 5H; 26 versus 1, p = 0.014) and AUC (Fig 5I, 25 vs 1, p = 0.015). ...
Context 6
... we verified the administered compound to be a true racemate (50% each enantiomer; S1 Fig), deviations from a ratio of 1 reveal significantly different pharmacokinetics between the D-and L-enantiomers. When administered as the racemate, the ratio of D/L enantiomer was about 25 for both C max (Fig 5H; 26 versus 1, p = 0.014) and AUC (Fig 5I, 25 vs 1, p = 0.015). As the purified L-enantiomer administered contained 97.4% L-enantiomer and 2.6% D-enantiomer (S1 Fig), if the enantiomers had identical pharmacokinetics, the ratio of L/ D would be predicted to be 36 (that is, 97.4/2.6). ...
Context 7
... the purified L-enantiomer administered contained 97.4% L-enantiomer and 2.6% D-enantiomer (S1 Fig), if the enantiomers had identical pharmacokinetics, the ratio of L/ D would be predicted to be 36 (that is, 97.4/2.6). When administered as the purified L-enantiomer, the ratio of L/D was 32 for C max (Fig 5H; 31.7 versus 36, p = 0.17) and 20 for AUC (Fig 5I; 19.8 versus 36, p = 0.006). ...
Context 8
... identity of the carrier for N-acetyl-leucine on the intestinal brush-border membrane is unknown; however, given that N-acetyl-leucine is a modified amino acid, the most likely candidates are amino acid transporters, as 52 families exist that show distinct substrate selectivity [31][32][33]. These possibilities can be narrowed down further based on the effect of N-acetylation, which forms an amide bond (Fig 1). An amide bond would both make N-acetyl-leucine appear more like a dipeptide and, through resonance, given the C-N bond partial double bond character with a bond order 1.5 [34], making it an analogue of an imine (Fig 1B). ...
Context 9
... possibilities can be narrowed down further based on the effect of N-acetylation, which forms an amide bond (Fig 1). An amide bond would both make N-acetyl-leucine appear more like a dipeptide and, through resonance, given the C-N bond partial double bond character with a bond order 1.5 [34], making it an analogue of an imine (Fig 1B). These predict that N-acetyl-leucine would be a substrate for the low affinity/high capacity a H + -coupled di/tripeptide transporter termed PepT1, which is highly expressed and responsible for 80% of all amino acids are taken up from the small intestine lumen, or an imino acid transporter which has 100-fold greater affinity for N-modified amino acids and shows only 2-fold stereoselectivity [35]. ...
Citations
... Despite clinically observed benefits of ADLL in AT individuals, it is well documented that the L-enantiomer, N-acetyl-L-leucine (NALL), is the pharmacologically active form of the drug ADLL [19] and that supplementation of up to 4 g/day of NALL is safe and well tolerated [20]. However, there are no published randomized controlled trials on the effect of NALL in patients with AT. ...
... The exact role of N-acetyl-L-leucine in vertigo is unknown [73,74]. Its primary mode of action is thought to be its influence on vestibular nucleus networks, with restoration of membrane potential of hyperpolarized/depolarized vestibular neurons. ...
There have been few investigations on the epidemiology, etiology, and medical management of acute unilateral vestibulopathy (AUV). Short-term pharmaceutical resolutions include vestibular symptomatic suppressants, anti-emetics, and some cause-based therapies. Anticholinergics, phenothiazines, antihistamines, antidopaminergics, benzodiazepines, and calcium channel antagonists are examples of vestibular suppressants. Some of these medications may show their effects through multiple mechanisms. In contrast, N-acetyl-L-leucine, Ginkgo biloba, and betahistine improve central vestibular compensation. Currently, AUV pathophysiology is poorly understood. Diverse hypotheses have previously been identified which have brought about some causal treatments presently used. According to some publications, acute administration of anti-inflammatory medications may have a deleterious impact on both post-lesional functional recovery and endogenous adaptive plasticity processes. Thus, some authors do not recommend the use of corticosteroids in AUV. Antivirals are even more contentious in the context of AUV treatment. Although vascular theories have been presented, no verified investigations employing anti-clotting or vasodilator medications have been conducted. There are no standardized treatment protocols for AUV to date, and the pharmacological treatment of AUV is still questionable. This review addresses the most current developments and controversies in AUV medical treatment.
... It is important to note that the dosage used in these in vivo studies (0.1 g per kg per day) approximates the dose used in previous observational clinical studies with the racemate, the phase IIb studies with IB1001, and the current IB1001-301 clinical trial. Finally, pharmacokinetic studies demonstrate that the D-enantiomer is not metabolized and could accumulate relative to the L-enantiomer during chronic administration of the racemate, having the potential for long-term negative effects [14]. Therefore, in this clinical trial, the effects of N-acetyl-L-leucine will be evaluated. ...
Background
Niemann-Pick disease type C (NPC) is a rare autosomal recessive neurodegenerative lysosomal disease characterized by multiple symptoms such as progressive cerebellar ataxia and cognitive decline. The modified amino acid N-acetyl-leucine has been associated with positive symptomatic and neuroprotective, disease-modifying effects in various studies, including animal models of NPC, observational clinical case studies, and a multinational, rater-blinded phase IIb clinical trial. Here, we describe the development of a study protocol (Sponsor Code “IB1001-301”) for the chronic treatment of symptoms in adult and pediatric patients with NPC.
Methods
This multinational double-blind randomized placebo-controlled crossover phase III study will enroll patients with a genetically confirmed diagnosis of NPC patients aged 4 years and older across 16 trial sites. Patients are assessed during a baseline period and then randomized (1:1) to one of two treatment sequences: IB1001 followed by placebo or vice versa. Each sequence consists of a 12-week treatment period. The primary efficacy endpoint is based on the Scale for the Assessment and Rating of Ataxia, and secondary outcomes include cerebellar functional rating scales, clinical global impression, and quality of life assessments.
Discussion
Pre-clinical as well as observational and phase IIb clinical trials have previously demonstrated that IB1001 rapidly improved symptoms, functioning, and quality of life for pediatric and adult NPC patients and is safe and well tolerated. In this placebo-controlled cross-over trial, the risk/benefit profile of IB1001 for NPC will be evaluated. It will also give information about the applicability of IB1001 as a therapeutic paradigm for other rare and common neurological disorders.
Trial registrations
The trial (IB1001-301) has been registered at www.clinicaltrials.gov (NCT05163288) and www.clinicaltrialsregister.eu (EudraCT: 2021–005356-10). Registered on 20 December 2021.
... ADLL (or racemate, mixture of D-and Lenantiomers) has been available in France since 1957 (Tanganil, Pierre Fabre Laboratories) as a treatment for acute vertigo and is available as a solution for injection and as a tablet. ALL was shown to be the active ingredient of the racemate responsible for the neuroprotective, diseasemodifying effects, demonstrating superior clinical effects when used independently [46]. ALL is not currently authorized anywhere in the world for the treatment of any condition. ...
Introduction:
Niemann-Pick disease type C (NPC) is a rare, autosomal recessive, lysosomal storage disorder. To combat the progressive neurodegeneration in NPC, disease-modifying treatment needs to be introduced early in the course of the disease. The only approved, disease-modifying treatment is a substrate-reduction treatment, miglustat. Given miglustat's limited efficacy, new compounds are under development, including gene therapy; however, many are still far from clinical use. Moreover, the phenotypic heterogeneity and variable course of the disease can impede the development and approval of new agents.
Areas covered:
Here, we offer an expert review of these therapeutic candidates, with a broad scope not only on the main pharmacotherapies, but also on experimental approaches, gene therapies, and symptomatic strategies. The National Institute of Health (NIH) database PubMed has been searched for the combination of the words 'Niemann-Pick type C'+ 'treatment' or 'therapy' or 'trial.' The website clinicaltrials.gov has also been consulted.
Expert opinion:
We conclude a combination of treatment strategies should be sought, with a holistic approach, to improve the quality of life of affected individuals and their families.
... It may directly affect the neurons in the vestibular nuclei [11]. Previous studies have reported that the L-enantiomer is the pharmacologically active enantiomer of NADLL [12,13]. NALL has not yet been approved for any indication in any jurisdiction. ...
Multiple Sulfatase Deficiency (MSD) is a rare autosomal recessive disease with specific clinical findings such as psychomotor retardation and neurological deterioration. No therapy is available for this genetic disorder. Previous studies have shown that N-acetyl-L-leucine (NALL) can improve the neurological inflammation in the cerebellum.
In the current study, the effects of NALL on ataxia symptoms and quality of life were explored in a patient with MSD.
This study was a crossover case study. The subject, a girl aged 12 years old, received NALL at a dose of 3 g/day (1 g in the morning, 1 g in the afternoon, and 1 g in the evening). A fasting blood sample was taken from the subject to evaluate side effects before the intervention and 4 weeks after taking supplement/placebo in every study stage. The ataxia moving symptoms were evaluated using the Scale for the Assessment and Rating of Ataxia (SARA) score in every study stage. Dietary intake was measured using 24-h dietary recall before and after the intervention. The diet compositions were assessed by Nutritionist IV software. Serum IL-6 level was measured using an ELISA kit.
There was no significant change in complete blood count (CBC) and serum biochemical factors in the patient with MSD after receiving NALL (3 g/day) over 4 weeks. The SARA score was reduced by 25%. The gait whose maximum score accounts for approximately one-fifth of the maximum total SARA score (8/40) was decreased. The heel-to-shin slide, the only SARA item performed without visual control, was also improved after therapy. Furthermore, there was a downward trend in the 8MWT (8.71 to 7.93 s). Regarding quality of life assessments, the parent and child reported improved quality of life index, physical health, and emotional function after taking NALL. Moreover, total energy intake was increased with NALL treatment through the study period.
Supplementation with NALL at a dose of 3 g/day over 4 weeks was well tolerated and improved ataxia symptoms, quality of life measure, and serum IL-6 levels in the patient with MSD. Further proof-of-concept trials are warranted to confirm the present findings.
... These studies specifically identified the L-enantiomer as the active isomer of the racemate, responsible for the neuroprotective effect, and suggested superior clinical effects when administered independently 3,8,9 . Further, pharmacokinetic studies in mice indicate that during chronic dosing of the racemate, the D-enantiomer may accumulate, with the potential for unwanted effects 10 . Recently, it was reported that NALL is taken up and distributed to all tissues including the central nervous system by the monocarboxylate transporter (MCT1) and hydrolyzed to L-leucine 11 thereby functioning as a prodrug for the delivery of L-leucine, a powerful intracellular metabolic signal of pathways such as mTORC1 12 . ...
Background and Objective
GM2 gangliosidoses (Tay-Sachs and Sandhoff diseases) are rare, autosomal-recessive, neurodegenerative diseases with no available symptomatic or disease modifying treatments. This clinical trial investigated N-acetyl-L-leucine (NALL), an orally administered, modified amino acid in pediatric (≥ 6 years) and adult patients with GM2 gangliosidoses.
Methods
In this Phase IIb, multi-national, open-label, rater-blinded study (IB1001-202), male and female patients aged ≥6 years with a genetically confirmed diagnosis of GM2 gangliosidoses received orally-administered NALL for a 6-week treatment period (4 g/day in patients ≥13 years, weight-tiered doses for patients 6-12 years), followed by a 6-week post-treatment washout period. For the primary Clinical Impression of Change in Severity analysis, patient performance on a pre-determined primary anchor test (the 8-Meter Walk Test or the 9-Hole Peg Test) at baseline, after 6 weeks on NALL, and again after a 6-week washout period, was videoed and evaluated centrally by blinded raters. Secondary outcomes included assessments of ataxia, clinical global impression, and quality of life.
Results
30 patients between the age of 6 and 55 were enrolled. 29 had an on-treatment assessment and were included in the primary modified intention-to-treat analysis. The study met its CI-CS primary endpoint (mean difference 0.71, SD=2.09, 90% CI 0.00, 1.50, p=0.039), as well as secondary measures of ataxia and global impression. NALL was safe and well-tolerated, with no serious adverse reactions.
Conclusions
Treatment with NALL was associated with statistically significant and clinically-relevant changes in functioning and quality of life in patients with GM2 gangliosidosis. NALL was safe and well-tolerated, contributing to an overall favourable risk: benefit profile. NALL is a promising, easily administered (oral) therapeutic option for these rare, debilitating diseases with immense unmet medical needs.
Classification of Evidence
This study provides Class IV evidence that NALL improves outcomes for patients with GM2 gangliosidoses.
Trial Registration Information
The trial is registered with ClinicalTrials.gov ( NCT03759665 ; registered 30-Nov-2018), EudraCT (2018-004406-25), and DRKS (DRKS00017539). The first patient was enrolled 07-June-2019.
... It is important to note that the dosage used in these in vivo studies (0.1 g per kg per day) approximates the dose used in previous observational clinical studies with the racemate, the Phase IIb studies with IB1001, and the current IB1001-301 clinical trial. Finally, pharmacokinetic studies demonstrate that the D-enantiomer is not metabolized and could accumulate relative to the L-enantiomer during chronic administration of the racemate, having the potential for long-term negative effects 14 . Therefore, in this clinical trial, the effects of N-acetyl-L-leucine will be evaluated. ...
Background
Niemann-Pick disease type C (NPC) is a rare autosomal recessive neurodegenerative lysosomal disease characterized by multiple symptoms such as progressive cerebellar ataxia and cognitive decline. The modified amino acid N-acetyl-leucine has been associated with positive symptomatic and neuroprotective, disease-modifying effects in various studies, including animal models of NPC, observational clinical case studies, and a multinational, rater-blinded Phase IIb clinical trial. Here, we describe the development of a study protocol (Sponsor Code “IB1001-301”) for the chronic treatment of symptoms in adult and pediatric patients with NPC.
Methods
This multinational double-blind randomized placebo-controlled crossover Phase III study will enroll patients with a genetically confirmed diagnosis of NPC patients aged 4 years and older across 16 trial sites. Patients are assessed during a baseline period and then randomized (1:1) to one of two treatment sequences: IB1001 followed by placebo or vice versa. Each sequence consists of a 12-week treatment period. The primary efficacy endpoint is based on the Scale for the Assessment and Rating of Ataxia, and secondary outcomes include cerebellar functional rating scales, clinical global impression, and quality of life assessments.
Discussion
Pre-clinical as well as observational and Phase IIb clinical trials have previously demonstrated that IB1001 rapidly improved symptoms, functioning, and quality of life for pediatric and adult NPC patients and is safe and well tolerated. In this placebo-controlled cross-over trial, the risk/benefit profile of IB1001 for NPC will be evaluated. It will also give information about the applicability of IB1001 as a therapeutic paradigm for other rare and common neurological disorders.
Trial registrations
The trial (IB1001-301) has been registered at www.clinicaltrials.gov (NCT05163288) and www.clinicaltrialsregister.eu (EudraCT: 2021-005356-10).
... One mechanism of action of NALL that has been implicated for this neuroprotective, disease-modifying effect is the activation of cerebral glucose metabolism in the cerebellum, correlated with enhanced cerebellar activity [5]. Pharmacokinetic studies also suggest the d-enantiomer could accumulate relative to the l-enantiomer during chronic administration of the racemate, with the potential for long-term negative effects [6]. Therefore, the individual l-enantiomer is being developed. ...
Objective
To investigate the safety and efficacy of N -acetyl- l -leucine (NALL) on symptoms, functioning, and quality of life in pediatric (≥ 6 years) and adult Niemann–Pick disease type C (NPC) patients.
Methods
In this multi-national, open-label, rater-blinded Phase II study, patients were assessed during a baseline period, a 6-week treatment period (orally administered NALL 4 g/day in patients ≥ 13 years, weight-tiered doses for patients 6–12 years), and a 6-week post-treatment washout period. The primary Clinical Impression of Change in Severity (CI-CS) endpoint (based on a 7-point Likert scale) was assessed by blinded, centralized raters who compared randomized video pairs of each patient performing a pre-defined primary anchor test (8-Meter Walk Test or 9-Hole Peg Test) during each study periods. Secondary outcomes included cerebellar functional rating scales, clinical global impression, and quality of life assessments.
Results
33 subjects aged 7–64 years with a confirmed diagnosis of NPC were enrolled. 32 patients were included in the primary modified intention-to-treat analysis. NALL met the CI-CS primary endpoint (mean difference 0.86, SD = 2.52, 90% CI 0.25, 1.75, p = 0.029), as well as secondary endpoints. No treatment-related serious adverse events occurred.
Conclusions
NALL demonstrated a statistically significant and clinical meaningfully improvement in symptoms, functioning, and quality of life in 6 weeks, the clinical effect of which was lost after the 6-week washout period. NALL was safe and well-tolerated, informing a favorable benefit-risk profile for the treatment of NPC.
Clinicaltrials.gov identifier
NCT03759639.
... Previous studies have shown significant differences in the pharmacokinetics of L-and D-enantiomers [23]. Given that the L-enantiomer is the pharmacologically active enantiomer in N-acetyl-DL-leucine, it should be better to run future studies with this formula [24]. ...
Ataxia-telangiectasia (AT) is a rare autosomal recessive disorder with no available curative treatment. Although the positive effects of N-acetyl-DL-leucine on cerebellar ataxia have been reported previously, there is little evidence of N-acetyl-DL-leucine’s effects in patients with AT. This study assessed the effect of 16 weeks N-acetyl-DL-leucine supplementation on ataxia symptoms in a 9-year-old female with AT. The subject consumed 4 g/day N-acetyl-DL-leucine (2 g in the morning and 2 g in the evening) for 16 weeks. Safety was assessed via clinical blood chemistry prior to the intervention and after 6 and 16 weeks. Additionally, The Scale for the Assessment and Rating of Ataxia (SARA) score was used to assess the drug’s effects on ataxia symptoms at baseline, 6, 12, and 16 weeks. Quality of life has also been evaluated by a specialist using the PedsQL questionnaire.Despite some initial (first week only) nausea and constipation, supplementation with N-acetyl-DL-leucine was well tolerated and safe according to blood chemistry measures. The SARA score progressively improved, and by week 16 had improved by 11.0 points (48.88%). Parent and self-reported quality of life assessments indicated physical, emotional, social, and school functions all improved by 16 weeks. Supplementation with N-acetyl-DL-leucine at a dose of 4 g/day for 16 weeks was well tolerated and significantly improved ataxia symptoms and quality of life measures in a young child with AT.
... NCT03759639,NCT03759665 and NCT03759678). CNS exposure of the administered compounds is equivalent within the limitations of the methods used, but L is metabolized rapidly whereas D is inert (Churchill et al., 2020). However, it remains to be determined if this proposed MOA is relevant to the effects of ADLL and individual enantiomers in NPC. ...
Acetyl-dl-leucine is a derivative of the branched chain amino acid leucine. In observational clinical studies, acetyl-dl-leucine improved symptoms of ataxia, in particular in patients with the lysosomal storage disorder, Niemann-Pick disease type C1. Here, we investigated acetyl-dl-leucine and its enantiomers acetyl-l-leucine and acetyl-d-leucine in symptomatic Npc1-/- mice and observed improvement in ataxia with both individual enantiomers and acetyl-dl-leucine. When acetyl-dl-leucine and acetyl-l-leucine were administered pre-symptomatically to Npc1-/- mice, both treatments delayed disease progression and extended life span, whereas acetyl-d-leucine did not. These data are consistent with acetyl-l-leucine being the neuroprotective enantiomer. Altered glucose and antioxidant metabolism were implicated as one of the potential mechanisms of action of the l-enantiomer in Npc1-/- mice. When the standard of care drug miglustat and acetyl-dl-leucine were used in combination significant synergy resulted. In agreement with these pre-clinical data, when Niemann-Pick disease type C1 patients were evaluated after 12 months of acetyl-dl-leucine treatment, rates of disease progression were slowed, with stabilization or improvement in multiple neurological domains. A beneficial effect of acetyl-dl-leucine on gait was also observed in this study in a mouse model of GM2 gangliosidosis (Sandhoff disease) and in Tay-Sachs and Sandhoff disease patients in individual-cases of off-label-use. Taken together, we have identified an unanticipated neuroprotective effect of acetyl-l-leucine and underlying mechanisms of action in lysosomal storage diseases, supporting its further evaluation in clinical trials in lysosomal disorders.
