IC50: 3.0 and 0.97 μM for full length BLM and BLM636–1298, respectively

ML216 is a potent inhibitor of the DNA unwinding activity of BLM helicase.

BLM helicase is reported to be a DNA unwinding enzyme critical in DNA repair through the homologous recombination pathway. BLM gene mutations lead to diminished BLM helicase activity and can cause Bloom’s Syndrome. Similar to other DNA repair enzymes, BLM helicase inhibition shows sensitization of tumor cells to conventional cancer therapies, such as camptothecin.

In vitro: ML216 showed submicromolar potency and selectivity over related helicases including RECQ1, RECQ5, and E. coli UvrD helicases. ML216 also inhibited cell proliferation of BLM-proficient fibroblast cells while had minimal effects on BLM deficient fibroblast cells, indicating on-target activity in a cellular context. Additionally, ML216 increased the frequency of sister chromatid exchanges, which was a diagnostic cellular phenotype consistent with the absence of a functional BLM protein [1].

In vivo: ML216 was a suitable starting point for further mouse tumor xenograft models and for the further development of potential cancer therapeutics [1].

Clinical trial: N/A

Reference:
[1] Rosenthal AS,Dexheimer TS,Nguyen G,Gileadi O,Vindigni A,Simeonov A,Jadhav A,Hickson I,Maloney DJ.  Discovery of ML216, a Small Molecule Inhibitor of Bloom (BLM) Helicase. Probe Reports from the NIH Molecular Libraries Program [Internet]. Bethesda (MD): National Center for Biotechnology Information (US); 2010-2011 Apr 15