Abstract A218: Simultaneous inhibition of both the PI3K-AKT and MAPK-ERK pathways using a single small molecule based approach for the treatment of advanced cancer.
Authors: Dhawan Neil , Smith Blake , Sangodkar Jaya , Gidwani Vickram , Kastrinsky David , Ohlmeyer Michael , Narla Goutham 
Published: June 2012

Background: Activation of the PI3K-AKT and MAPK-ERK signaling pathways drives a significant percentage of human cancer and serve as the target for multiple drug development efforts and clinical trials. Due to defined molecular crosstalk, dual inhibition of both pathways is necessary for optimal therapeutic efficacy, and therefore, combinations of PI3K-AKT and MAPK-ERK specific drug therapies are being evaluated. In this study, we have identified compounds that are capable of simultaneously inhibiting both the PI3K-AKT and MAPK-ERK pathway to induce apoptosis both in vitro and in mouse models of the disease. Moreover, we have performed additional derivatization of these small molecules to limit their toxicity and significantly improve their therapeutic window in cell culture and in vivo.

Methods: Our new series of molecules are derived from the phenothiazine, exemplified by trifluoperazine(TFP), and dibenzazepine structural backbones, exemplified by clomipramine(CIP). While the antiproliferative properties of neuroleptic tricyclics have been identified, previous clinical trials failed due to dose limiting CNS toxicities related to their potent antidopaminergic properties. We rendered the pendant amine non-basic to attempt to abolish the antidopaminergic effects of this class of drugs. We screened 100 of these novel compounds in the PTEN-null, EGFR-activated H1650 cell line. Subsequently, we determined the effect of two candidate molecules on the PI3K-AKT and MAPK-ERK pathways and their ability to induce apoptosis in vitro and in vivo.

Results: Through multiple rounds of SAR (structure activity relationship) analysis, we sequentially derivatized the parent compounds and identified two potent small molecule candidates that efficiently decouple the dose limiting CNS toxicity from the anti-proliferative and anti-tumorigenic properties of this class of FDA approved drugs. Treatment of a panel of lung adenocarcinoma cancer cell lines with these compounds, DBK-368 and DBK-382, led to a decrease in cell viability through the induction of spontaneous apoptosis. These compounds specifically induce caspase-dependent apoptosis as indicated by ZVAD-mediated inhibition of Annexin V staining. Upon mechanistic analysis, DBK-368 and DBK-382 display the ability to directly inhibit AKT and ERK downstream of PI3K and MEK, efficiently and potently decoupling the crosstalk between these two signaling pathways. Furthermore, in a transgenic inducible EGFR-activated mouse model of lung adenocarcinoma, we demonstrated that the novel derivative compounds inhibit AKT and ERK signaling and induce apoptosis in vivo. Lastly, in vivo toxicology studies demonstrated that while TFP exhibited dose limiting CNS toxicities at 15 mg/kg, DBK-368 and DBK-382 displayed no significant effects up to 60 mg/kg.

Conclusions: We have identified a series of novel small molecules through a reverse engineering effort of the tricyclic class of FDA approved drugs. Specifically, DBK-368 and DBK-382 appear to be promising monotherapy for advanced cancer as they exhibit dual functionality in the inhibiting both the PI3K-AKT and MAPK-ERK pathways simultaneously, both in vitro and in vivo.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr A218.