Investigating the role of uptake and metabolism in the mechanism of action of the drug N-acetyl-leucine

N-acetyl-leucine (NAL) is an acetylated form of the amino acid leucine. Originally used as a treatment for acute vertigo, there is now intense interest in repurposing this drug for other neurological disorders with unmet medical needs. Potential applications include the lysosomal storage disorder Niemann-Pick disease Type C (NPC), for which a successful phase III clinical trial was completed in 2023 (NCT05163288). NAL is a chiral molecule, existing as L and D enantiomers. The L form is of primary interest for clinical development, although the D form can elicit certain therapeutic effects (Kaya et al, 2021).

Despite its therapeutic promise, the mechanism of action of NAL remains incompletely understood. This project aims to contribute to our mechanistic understanding of NAL, thereby providing a rational framework to expand its use in rare and common neurological disorders and potentially informing the development of new drugs.

The working hypothesis is that NAL is a prodrug of leucine, acting via leucine or its metabolites. A broad outcome of NAL treatment may be to normalise cellular energy production, which has been shown to be dysregulated in NPC (Kennedy et al, 2013). Experimental data also indicate that cellular uptake of NAL utilises a monocarboxylate transporter (MCT) rather than the L-type amino acid transporter (LAT1) used by leucine (Churchill et al, 2021). This may have important mechanistic implications: for example, MCT kinetics could enhance the relative flux through ordinarily minor pathways of leucine metabolism.

We will test several independent but interrelated hypotheses regarding the mechanism of NAL. Central aims of the project are as follows:

1. To test the role of uptake by a transporter in the mechanism of action of NAL
2. To determine the metabolic fate of NAL
3. To test the role of metabolism in the mechanism of action of NAL
Experimental techniques will include molecular and cell biology methods, the use of pharmacological inhibitors, flow cytometry, imaging/microscopy, liquid chromatography and mass spectrometry. Areas of skill development will include quantitative skills such as statistical analysis, development of scientific communication skills, and training for in vivo work if required.