Abstract 3775: Mutated cancer cell-specific cell death activity of alkylating Pyrrole-Imidazole polyamide conjugates targeting a variety of oncogenic driver gene mutations
Authors: Nagase Hiroki , Hiraoka Kiriko , Inoue Takahiro , Yoda Hiroyuki , Sakthisri Krishnamurthy , Lin Jason , Watanabe Takayoshi , Koshikawa Nobuko , Takatori Atsushi 
Published: July 2016

Cancer may be recognized as non-self by antibiotics such as minor groove binders, which show self / non-self recognition partially due to preferential DNA sequence recognition and distinguish from other non-self bacteria. We learned minor groove binders produced from Streptomyces and synthesized Pyrrole-Imidazole polyamide indol-seco CBI conjugate to alkylate specific sites in the cancer genome.

Although a tremendous amount of studies has been made to directly target oncogenic drivers, such as RAS and MYC, yet no drug is clinically available because of difficulties to develop RAS- or Myc-targeted anti-cancer therapeutics due to the smooth 3D surface topology. One of major limitations of targeting the RAS pathway may be intrinsic or acquired resistance as seen in the other molecular target therapy. New approaches that directly target driver genes may provide a more direct route to helps address unmet medical needs for refractory cancer conquest.

We therefore synthesized several Pyrrole-Imidazole polyamide conjugates, each of which specifically alkylated KRAS codon 12 mutant DNA (G12D or G12V), amplified MYCN or mutated DNA of PI3K E542K mutation. All three conjugates reduced expression of the mutated oncogenic-protein by RNA transcription inhibition and induced cancer cell death at low dose (1 to 50 nM). Low dose tail vein injections of conjugates-targeting KRS or MYCN also demonstrated significant anti-tumor effects on xenograft models of human tumors harboring oncogenic mutated driver with minimum host toxicity, but not in xenografts harboring wild type or non-recognized mutations. We also performed a series of biological searches for toxicities by applying Modified SHIRPA (behavioral and functional analysis of mouse phenotype) to test any pathological phenotypes and examinations of blood and urine in ICR mice. Modified SHIRPA screening, blood chemistry, blood cell analysis and urea tests exhibited no toxicologically significant changes. Additionally, we examine pharmacokinetics of PI polyamide conjugates In vivo using LC-mass and fluorescent imaging of tumor-bearing mice. Intriguingly, 48 hours after the administration the highest fluorescence intensity was observed in the tumor-cell nuclear and almost no fluorescent intensity in all other organs, tissues and cells. These data suggest that sequence-dependent alkylating approach using antibiotic mimics of alkylating PI-polyamide conjugates, may open a new strategy not only targeting point mutation of driver oncogene but also targeting key driver gene in the cancer amplicon. This approach should be used for future ‘ Precision cancer medicine’.

Citation Format: Hiroki Nagase, Kiriko Hiraoka, Takahiro Inoue, Hiroyuki Yoda, Krishnamurthy Sakthisri, Jason Lin, Takayoshi Watanabe, Nobuko Koshikawa, Atsushi Takatori. Mutated cancer cell-specific cell death activity of alkylating Pyrrole-Imidazole polyamide conjugates targeting a variety of oncogenic driver gene mutations. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3775.