Profiling crystal engineered ligands for targeting treatment resistant androgen receptors.

Introduction: Prostate cancer (PCa) is one of the principal contributors to health burden in the aging male population. PCa develops through dysregulation of androgen receptor (AR) signaling pathways. Despite improvements in diagnostic techniques and interventions, no pharmacological measures with long term efficacy have been established once PCa advances to castration resistant prostate cancer (CRPC). To circumvent this issue, tetra-aryl cyclobutanes (CBs) have been proposed as structurally distinct compounds with a mechanism of action differing from traditional androgen receptor pathway inhibitor (ARPI). Methods: Here, we apply principles of crystal engineering and solid state synthesis to expand the class of CBs through strategic derivatization. The synthesis of the CB occurs quantitatively, producing no side products. We demonstrate how head-to-tail stacking interactions of halo-pyrimidine rings can be exploited to stack and align unsymmetrical alkenes to undergo [2 + 2] photodimerization to generate the CB in the solid state. We examine the structure-function relationships of CBs in vitro by profiling AR mediated transcriptional activity, receptor translocation, and cell viability. Moreover, we explored putative binding interactions of ClCB and BrCB ligands across distinct AR mutants (wild-type, T877A, and F877L/T878A) using molecular docking. Results/Discussion: In total, our data suggest that CBs have unexploited therapeutic potential in CRPC and that green chemistry and crystal engineering principles offer a unique route to generate these drug candidates.