Abstract 3657: Preclinical evaluation of water-soluble pyrrolo[3,2-d]pyrimidines as single agents with tubulin and multiple receptor tyrosine kinase inhibition and as antitumor agents

Abstract

Abstract Multiple classes of microtubule targeting agents have been identified and these include the Vinca alkaloids and colchicine (microtubule-destabilizers) and taxanes (microtubule-stabilizers). Although tubulin targeting agents are some of the most successful drugs used in the treatment of a wide range of malignancies, multidrug resistance due to overexpression of P-glycoprotein (Pgp) and/or βIII-tubulin can severely limit their clinical efficacy. Antitubulin agents like paclitaxel and other taxanes, due to poor water solubility, are formulated with polyethoxylated castor oil which can cause hypersensitivity reactions and require prolonged administration time. Recently, we reported water-soluble pyrrolo[3,2-d]pyrimidine analogs acting as antitubulin agents that circumvent these drawbacks. These analogs also exhibit potency comparable to erlotinib in cancer cell lines overexpressing epidermal growth factor receptor (EGFR) and to that of sunitinib in cancer cell lines overexpressing vascular endothelial growth factor receptor-2 (VEGFR2) and platelet derived growth factor receptor-β (PDGFRβ), in addition to inhibiting tubulin. Promising evidence for the clinical success of combination chemotherapy using multiple RTK inhibitors with antitubulin agents suggests that these dual acting compounds would serve as a single entity with both these activities. To explore the activity of these dual RTK/tubulin inhibitors, compound AG165 was evaluated in in vitro and in vivo xenograft models. In vitro AG165 inhibited the growth of MDA-MB-435 cells with an IC50 of 8.8 nM, comparable to paclitaxel. The compound is also active in paclitaxel resistant cancer cells overexpressing βIII-tubulin or Pgp, thus overcoming two important mechanisms associated with clinical resistance to paclitaxel. Compound AG165 (subcutaneous doses of 75 mg/kg x 7, cumulative dose 525 mg) showed significant (p<0.001) inhibition of tumor growth 15 days after treatment initiation. AG165 caused recoverable weight loss without any evidence of adverse effects. In this study, we have identified a water-soluble, dual acting RTK/ tubulin inhibitory agent that address some critical limitations of existing therapies and demonstrates in vivo antitumor effects with an acceptable toxicity profile. Citation Format: Khushbu Shah, Aleem Gangjee, Roheeth Pavana, Dybdal-Hargreaves F. Nicholas, Susuan Mooberry. Preclinical evaluation of water-soluble pyrrolo[3,2-d]pyrimidines as single agents with tubulin and multiple receptor tyrosine kinase inhibition and as antitumor agents. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3657. doi:10.1158/1538-7445.AM2015-3657