Abstract 2224: Re-engineering of the duocarmycin structural architecture enables tumour-selective CYP2W1-mediated drug activation in human colon cancer xenografts.

There is now growing evidence that CYP1A1, 1B1, 2J2, 2S1 and 2W1 are over-expressed in many human tumour types. The ultrapotent duocarmycins are ideal candidates for bioprecursor drug development and we have demonstrated that these can be re-engineered into derivatives selectively activated by CYP1A1 in vitro and in vivo. 1 , 2 In the present study, we have focussed on CYP2W1 as a potential therapeutic target. CYP2W1 is detected in 30% of colon cancers, while its protein expression in non-transformed adult tissues is absent or insignificant. 3 We have presented results indicating that the immunohistochemically assessed level of CYP2W1 enzyme could fulfil the criteria for being a prognostic biomarker for stages II and III colorectal cancer. 4 Here we present data on furanoindole-based duocarmycins that have the potential to be used as a chemical probe (e.g. ICT2726) to show CYP2W1 functional activity. We also report on indoline-based analogues that elicit potent antiproliferative activity after CYP2W1-mediated activation in cancer cells. Specifically, we have transfected human HEK293, Colo320 and SW480 cells to express CYP2W1 and shown that these suffer rapid loss of viability following treatment with two halogenated duocarmycin bioprecursor compounds (ICT2705 and ICT2706) while no activity in mock-transfected cells was seen. Significantly, ICT2706 was shown to totally prevent tumour growth when administered to SCID mice bearing SW480-2W1 xenografts (dosed daily with 100 mg/kg for 8 days) but not the mock-transfected variant. Subsequent to this treatment, the tumours were extracted for further analysis. Using H2A.X phosphorylation as a marker for DNA damage, our data revealed a time-dependent increase in expression supporting CYP2W1-mediated activation of ICT2706 in vivo. Our findings reveal the opportunities in targeting CYP2W1 as a novel therapeutic approach in colon cancer chemotherapy. Citation Format: Klaus Pors, Sandra Travica, Paul M. Loadman, Steven D. Shnyder, Mark Sutherland, Helen M. Sheldrake, Mark Searcey, Inger Johansson, Souren Mkrtchian, Magnus IngelmanSundberg, Laurence H. Patterson. Re-engineering of the duocarmycin structural architecture enables tumour-selective CYP2W1-mediated drug activation in human colon cancer xenografts. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2224. doi:10.1158/1538-7445.AM2013-2224