Structural Elucidation, Modification and Anticancer Properties of a Lead Compound Nicotinamide N-Methyltransferase Inhibitor
- Publication Type:
- Thesis
- Issue Date:
- 2021
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Nicotinamide N-methyltransferase (NNMT) is an enzyme that together with the methyl donor S-adenosyl methionine (SAM) catalyses the methylation of nicotinamide and related compounds. NNMT has been involved in a range of diseases including cancers and metabolic disorders. The development of NNMT inhibitors (NNMTIs) may lead to new therapeutic drugs for these disorders. Research into the development of NNMTIs has occurred over the past decade, however the inhibitors that have come out of these programs lack potency and specificity. Therefore the development of NNMTIs with therapeutic potential remains an unmet need.
Recently a library of mono-N-alkylated tetrahydroisoquinoline (THIQ) compounds were synthesised in a different research, and one analogue (compound 23, see page 24) was shown to inhibit NNMT from a screening service offered by Eli Lilly. The original aim of this project was to optimise the NNMT inhibitory activity of 23 by synthesising and testing of a range of analogues.
A key step in the synthesis of 23 and its analogues was mono-alkylation of the amine group in THIQ with propargyl bromide. The reaction had been reported to give exclusively the mono-alkylated product when performed with 2 equivalences of propargyl bromide, however when the reaction was conducted the 1H NMR of the product indicated that dialkylation had occured. Therefore this project began with an investigation to confirm that compound 23 was indeed a di-alkylated product. Two series of THIQ analogues- one mono-alkylated series and one di-alkylated series were synthesised. In total, eight compounds were synthesised. The information obtained from these reaction outcomes, was used to further understand each reaction mechanism.
The NNMT inhibitory activity of the THIQ analogues was next assessed using an NNMT inhibition assay reported in the literature. The assay involved the NNMT mediated formation of a fluorescent quinolinium product whose formation could be followed and quantified using a plate reader. After several attempts at assay optimisation, it was discovered that the assay was not sufficiently sensitive to follow the reaction kinetics. Decreased sensitivity was attributed to quenching of the quinolinium fluorescence by the assay buffer system. Unfortunately, time constraints prevented assay optimisation.
The anticancer activity of THIQ libraries was assessed against the MDA-MB-231 breast cancer cell line. These assays showed that four of eight compounds reduced cell viability at concentrations below 50 μM. Further testing is now required to establish if the observed anticancer activity is mediated by inhibition of NNMT or by actions at other cellular targets.
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