Abstract 5461: Novel antitumor amino-pancratistatin derivatives inhibitors of protein and DNA synthesis

The Amaryllidaceous alkaloids pancratistatin and narciclasine are known to exert marginal antitumor properties but associated with toxicities. Despite extensive investigations, pancratistatin or analogues did not succeed to provide sufficient therapeutic benefit although a new pro-drug strategy was applied recently to narciclasine. We decided to undertake a chemistry program aimed at modifying the skeleton of this attractive pharmacophore in order to improve its therapeutic application. At first sight, literature survey suggests that any change in the structure would lead to a loss of activity but a careful examination of published data indicated that position −1 of the molecule may be of potential interest although poorly investigated. We report here the synthesis of a series of 39 novel derivatives of 1-aminopancratistatin by chemical modification of the naturally available narciclasine extracted from Narcissus bulbs. These new compounds present improved pharmaceutical properties such as higher aqueous solubility (from 300 µg/ml for narciclasine up to 2000 µg/ml) without loss of stability tested on human and murine microsomal assays (70-90% stability after 1h incubation). A sub-set of these novel derivatives demonstrated a drastic increase of the cytotoxic activity reaching nM range tested on a panel of 8 different cell lines. The higher antiproliferative activity translates towards the induction of stronger pro-apoptotic signals evidenced with Annexin V, caspase 3/7 and JC-1 assay. Besides the previously described inhibition of protein synthesis, our studies originally demonstrated that part of the mechanism of action involves inhibition of DNA synthesis as well. The contribution of these two pharmacological properties elaborates a SAR (structure - activity relationship) and segregates our new pancrastistatin derivatives into different categories depending on their ability to inhibit protein synthesis, DNA synthesis or both. Based on their differential in vitro activity profile, the compounds were selected for evaluation of their in vivo antitumor properties on murine and xenografted models. As a major result F 98604 (dimethylaminomethyl benzamide derivative of pancratistatin) exhibited significant and reproducible activity on the murine B16 sc and human A375 melanoma models in terms of tumor growth inhibition as well as increased therapeutic index. The present SAR suggests that modification of the natural pancratistatin or narciclasine pharmacophore at the position −1 open new perspectives as potential anticancer agents with novel pharmacological profiles. Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 5461.