Development of benzofuran-derived sulfamates as dual aromatase-steroid sulfatase inhibitors (DASIs): design, synthesis and biological evaluation

Resistance of oestrogen receptor-positive (ER+) breast cancer, the most prevalent type of breast cancer accounting for ∼70% of all cases, to current therapies necessitates the study of alternative strategies. One promising strategy is the multi-targeting approach using dual aromatase-steroid sulfatase inhibitors (DASIs). Herein, we describe the development of DASIs using a common benzofuran pharmacophore. Triazole benzofuran sulfamates were found to have low nM aromatase (Arom) inhibitory activity but no steroid sulfatase (STS) inhibitory activity (IC₅₀ > 10 μM); by contrast, benzofuran ketone sulfamates demonstrated low nM STS inhibitory activity but no Arom inhibitory activity (IC₅₀ > 1 μM). The addition of a methyl group at the 3rd position of the benzofuran ring in the benzofuran ketone sulfamate 19 (R¹ = CH₃) had a notable effect, resulting in dual aromatase and STS inhibitory activities with the 4-chloro derivative 19b (Arom IC₅₀ = 137 nM, STS IC₅₀ = 48 nM) and 4-methoxy derivative 19e (Arom IC₅₀ = 35 nM, STS IC₅₀ = 164 nM) optimal for dual inhibition. Arom/STS inhibition results combined with molecular dynamics studies provided a clear rationale for the activity observed.