Abstract 671: Tumor delay and mechanism of action studies of a novel cyanoaziridine derivative, AMP423

Proceedings: AACR 102nd Annual Meeting 2011‐‐ Apr 2‐6, 2011; Orlando, FL We describe a novel cyanoaziridine derivative, AMP423, which possesses good cytotoxic potency against a wide variety of cancer cell types. AMP423 is a naphthyl derivative of 2-cyanoaziridine-1-carboxamide, (C14H11N3O, MW 237.2), with structural similarity to the iminopyrrolidone-based pro-oxidant anti-tumor agent imexon. In contrast to imexon, AMP423 is more lipophilic (clog P = 3.32) and possesses a mean 16-fold greater cytotoxic potency than imexon against a variety of cancer cell lines, including multiple myeloma (RPMI 8226/S, H929, U266, MM.1S), pancreatic (MiaPaCa-2, Panc-1, BxPC-3), colorectal (HCT-116), lymphoma (SU-DHL-6), leukemia (MV-4-11, OCI-AML-3), prostate (DU-145, PC-3), and breast (MDA-MD-231, MCF-7). The mean 72h IC50 for AMP423 against these cell types ranged from 2 – 36 uM, in contrast to 16 – 552 uM, for imexon. The greater cytotoxic potency may be due to the lipophilic naphthyl moiety, allowing greater cell uptake. There was also no cross-resistance in two drug resistant myeloma cell lines, RPMI 8226/IM10 (5x resistance to imexon) and RPMI 8226/Dox40 (40x resistance to doxorubicin). In vitro mechanism of action studies were performed in the RPMI 8226/S and RPMI 8226/IM10 myeloma cell lines. At equipotent concentrations, growth inhibition by both AMP423 and imexon were due to a combination of apoptosis and necrosis (AnnexinV/PI). Both drugs caused a loss of mitochondrial membrane potential (JC-1), a loss of cellular thiols (CMFDA), generation of reactive oxygen species (HE), and activation of caspase 3. In spite of these similarities, cell cycle effects were dissimilar; whereas imexon causes G2/M arrest, cells treated with AMP423 arrest in S-phase (propidium iodide). Despite a chemical similarity to other aziridine-containing molecules, AMP423 showed no evidence of alkylation (p-nitrobenzyl pyridine alkylation assay), which may be due to the presence of the cyano group resulting in a reduced reactivity towards cellular nucleophiles. In vivo, in SCID mice, treatment with AMP423 resulted in a significantly delayed mean tumor growth rate compared to vehicle treated controls against SU- DHL-6 lymphoma xenografts (p=0.0484) and a marginally significant delay against RPMI 8226/S myeloma xenografts (p=0.0775). AMP423 did not affect tumor growth against MDA-MB-231 breast or MiaPaca-2 pancreatic xenografts when used alone, however, in combination with gemcitabine, we saw significantly greater tumor growth delay in the MiaPaca-2 pancreatic xenografts (p=0.0322). Like imexon, toxicology tests showed that AMP423 is relatively non-myelosuppressive. Herein, we report that AMP423 mechanistically shows many similarities to imexon, however it possesses greater cytotoxic potency across a wide range of cancer cell types, and thus may be a good candidate for future clinical development. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 671. doi:10.1158/1538-7445.AM2011-671