Synthesis of Thieno[2,3-d]pyrimidine-Based EGFR-TK Inhibitors with Improved Solubility and Metabolic Stability

Abstract

The objective of this master s thesis was to synthesize EGFR tyrosine kinase inhibitors with enhanced aqueous solubility, metabolic stability and potency compared with commercially available inhibitors. Improving these properties, may lead to a higher in vivo exposure, thus lowering the chance of side-effects for cancer patients in a therapeutic setting.

The aqueous solubility of the inhibitors has been enhanced by the introduction of solubilizing amine tails that are protonated at physiological pH. In addition to enhanced solubility, the tails also increased the potency of the inhibitors by interacting with additional amino acids in the enzyme, which is supported by computational molecular docking.

Access to the target compounds was achieved in four steps. Arylboronic esters with methyl ester functional groups were prepared by esterification followed by a palladium catalysed borylation. These were then coupled to the thienopyrimidine scaffold in a Suzuki coupling. Finally, introduction of the solubilizing tails was achieved by aminolysis of the methyl esters.

The work has resulted in 11 new inhibitor molecules and three new intermediates. Four of the target compounds are roughly equipotent to the commercial inhibitor Erlotinib (IC50 < 1 nM). Three candidates with solubilizing tails were further tested for solubility and metabolic stability, and outperformed Erlotinib in both categories. The thorough biological and chemical testing of the target molecules has confirmed the hypotheses of increased solubility, potency and metabolic stability. However, when tested for cell membrane permeability, high efflux ratios were measured. This could indicate the inhibitors may be substrates of transporter enzymes.