Abstract B27: First-in-class cytoskeletal targeting drug, Anisina, enhances effectiveness of microtubule inhibitors in a preclinical model of neuroblastoma

Abstract

Abstract Neuroblastoma is the most common extracranial solid tumor in childhood accounting for ~7% of all cancer cases in children. Children with high-risk neuroblastoma still have a poor overall outcome when treated with existing chemotherapeutics, making it imperative that new chemotherapeutic strategies are developed to treat this disease. The actin cytoskeleton is an ideal chemotherapeutic target due to its role in numerous biological processes essential for tumor cell growth and survival. While the therapeutic potential of actin-targeting compounds has been extensively investigated, no lead compound has been developed through to the clinic due to the associated cardiac and respiratory toxicity. We have developed a novel class of anti-tropomyosin (ATM) drugs that target cancer- associated actin filaments containing the tropomyosin Tpm3.1. The lead ATM, Anisina, was identified utilizing Novogen's proprietary VAL-ID - Versatile Approach to Library-based Iterative Design – medicinal chemistry program. This strategy is based around the design, synthesis and evaluation of targeted small-molecule libraries and has proven to be a rapid and robust method of identifying lead compounds. In vitro studies have demonstrated that Anisina binds to and impairs the function of Tpm3.1 in a dose dependent manner in both protein and cell based assays. Inhibition of Tpm3.1 function in a tumor cell model results in the destabilization of Tpm3.1 containing actin filaments and induction of tumor cell death via the activation of the intrinsic apoptotic pathway. Anisina has broad efficacy against both adult and pediatric cancers in vitro. When tested against a panel of neuroblastoma cell lines, Anisina was effective independent of NMYC status and had an average IC50 of 4-7uM. In preparation for the clinic, in vitro synergy studies were undertaken to evaluate the impact of Anisina in combination with standard of care chemotherapeutics. Anisina showed a high degree of synergy (combinatorial index <0.5) with anti-microtubule agents, both vinca alkaloids (microtubule destabilizing) and taxanes (microtubule stabilizing) in some adult and pediatric cancer cell models. In particular a ~20 fold increase in sensitivity to drug induced cell death was observed in tumor cells treated with the Anisina/Vincristine (VCR) combination. The same combinatorial effect was not observed with untransformed cells. More importantly, the synergy observed with Anisina/VCR in vitro has now been replicated in a CHLA20 human neuroblastoma xenograft model. Animals (n=4-5) were randomly divided into four treatment groups i) Control (Captisol), ii) Anisina (150mg/kg daily IP) iii) VCR alone (0.5mg/kg weekly, IV) and iv) Anisina (150mg/kg) + VCR (0.5mg/kg). Animals treated with Anisina/VCR showed a significant and profound regression of tumor growth compared to control and either drug treatment alone. Further to this, of the 5 animals in the combinatorial Anisina/VCR treatment group 3 (60%) reached a “complete response” with one animal showing a “maintained complete response” for more than 100 days post treatment. The outcomes of this study have significant therapeutic implications as microtubule inhibitors such as VCR are current standard of care for a wide range of solid tumors, including neuroblastoma. Anisina is currently being developed as an adjunct therapy for the treatment of both adult and pediatric cancers. Citation Format: Justine Stehn, Mark Currier, Duo Chen, Eleanor Eiffe, Andrew Heaton, Jeff Hook, Peter Gunning, Timothy Cripe. First-in-class cytoskeletal targeting drug, Anisina, enhances effectiveness of microtubule inhibitors in a preclinical model of neuroblastoma. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Pediatric Cancer Research: From Mechanisms and Models to Treatment and Survivorship; 2015 Nov 9-12; Fort Lauderdale, FL. Philadelphia (PA): AACR; Cancer Res 2016;76(5 Suppl):Abstract nr B27.