Lung cancer is one of the leading causes of death worldwide with non-small cell lung cancer (NSCLC) accounting for more than 80% of all cases1, many cases of which are associated with oncogenic aberrations of fibroblast growth factor (FGF) signalling pathways making fibroblast growth factor receptors (FGFRs) attractive molecular targets for drug development2. The FGFR1-4 are receptor tyrosine kinases for which many small molecule inhibitors have been tested in clinical trial – a renewed focus has been on a subset of such molecules, irreversible inhibitors that covalently modify the protein.
A series of irreversible FGFR inhibitors have been tested in cell biology assays at the Auckland Cancer Society Research Centre and were found to be potent inhibitors of FGFR13. We have focused on understanding the structural basis of this inhibition, in particular, how the reactive centre of the inhibitor is presented to the target (Cys488), and also to discover a means to reliability measure the reactivity of the inhibitors against recombinant protein in vitro.
We have shown by mass spectrometry the relative reactivity of three series of compounds towards FGFR1 and compared these results to the profiles of published inhibitors FIIN-1 and TAS-120. We hypothesize that inherently lower reactivity correlates with substitution at the acrylamide group in our novel compounds compared to the unsubstituted acrylamide literature compounds, and that this is probably an advantage in a drug candidate as it may limit the potential for toxicity from indiscriminate reactivity. The mass spectrometry assay will also allow us to show in isolated protein experiments, the selectivity of the inhibitors for different members of the FGFR family. We will present preliminary results suggesting that structural flexibility within inhibitors as well as in the protein P-loop, are critical molecular mechanisms in determining both reactivity and selectivity in FGFR targeting.