ART6043 is a potent and selective small molecule inhibitor of DNA polymerase theta (DNA Polθ), inhibits Polθ polymerase domain (residues 1820-2590) with IC50 of 1.3 nM.
ART6043 shows no inhibitory activity against related polymerases Polα, Polγ, Polη and Polν up to >120 uM.
ART6043 inhibits Polθ non competitively with respect to dNTPs and uncompetitively with respect to DNA.
ART6043 has EC50 of 0.6 nM in BRET assays, as direct evidence of target engagement and the DNA uncompetitive binding mode in cells.
ART6043 selectively inhibits Polθ-mediated MMEJ with a potency of approximately 60 nM, but does not inhibit DSBR through non-homologous end joining (NHEJ) or homologous recombination (HR).
ART6043 inhibits survival of BRCA1 null, MDA-MB-436 triple negative breast cancer (TNBC) cells harbouring a SHLD2 gene knockout in colony formation assays (CFAs) with EC50 of 60 nM.
ART6043 inhibits cell survival across a broader panel of HRD lines with loss of either BRCA1, BRCA2 or RAD51C protein expression with EC50 of 0.059-0.88 uM.
ART6043 (50 mg/kg, PO, BID) exhibits tumour growth inhibition (TGI) of MDA-MB-436 SHLD2-/- cells transplanted into rats.
ART6043 potentiates response to PARP inhibitors in HRD cells, potentiates PARP inhibitor efficacy and induces phospho-RPA and DSBs in vitro and in vivo.
ART6043 potentiates PARP inhibitor efficacy in BRCA2, BRCA1 and RAD51C null tumours in vivo.