Abstract A233: Pharmacodynamic Transcriptional markers of carboxyamidotriazole orotate (CTO) exposure in anagen hair.
Authors: Karmali Rashida A. , Miele Gino 
Published: August 2014

Background: Carboxyamidotriazole Orotate (CTO) is the orotic acid salt of carboxyamodotriazole (CAI)which is an inhibitor of calcium -dependent intracellular and extracellular signal transduction pathways, also possessing antiproliferative, antiangiogenic and anti-invasive properties. The activity of CTO alone and combination with temozolomide or 5-fluorouracil was demonstrated in human glioblastoma, melanoma and colon tumor xenografts. In Phase I (NCT01107522), nine patients pretreated with 2 to 8 targeted and non-targeted drugs and having refractory tumors responded to CTO at doses ranging 75mg/m2/day through 427mg/m2/day, and achieved stable disease for different periods (3 to 14 months). Four pretreated tumors were found to have different genomic mutations (PI3KCA, EGFR multiple, BRAFV600 and NRAS) consistent with CTO's suggested mechanism of action to inhibit multiple tyrosine kinases in addition to modulating calcium signaling pathways and calcium-dependent signal transduction pathways, as yet uncharacterized.

Method: Using Epistem's ex vivo plucked anagen hair assay platform global gene expression evaluation by microarray analysis was performed to assess transcriptional response to varying doses of CTO (2, 5 and10 μM). Plucked anagen scalp hairs from five healthy donors were exposed to varying doses of CTO over a 24 hr period. Total RNA was isolated form the hair bulbs post culture and used to assess global transcriptional alterations.

Results:Significant biologically relevant alteration of the anagen hair bulb transcriptome, ranging from -100 fold to +25 fold differential expression of some mRNAs was observed at CTO levels shown to be clinically relevant. Importantly, transcriptional signatures associated with inhibition of EGFR, MEK, HDAC and HSP90 were strongly suppressed at all doses of CTO. In addition, genes associated with non-voltage dependent calcium signaling were strongly suppressed, together with those associated with RAS and Growth Factor Signature. Modest suppression of transcription signatures of WNT signaling was evident at longer CTO exposure. In contrast, activation of tumor suppressor signatures associated with P53 was observed.

Conclusion: These data provide multiple pharmacodynamics markers associated with the suggested mechanism of action of CTO e.g., inhibition of genes of non-voltage dependent calcium signaling and multiple onco-pathways, and also activation of signatures associated with tumor suppressors. These results in the anagen hair assay may provide the molecular MOA of CTO's observed clinical benefit in a broad spectrum of malignant tumors with different genomic types and a tool to design customized combination therapies of CTO with other agents.

Citation Information: Mol Cancer Ther 2013;12(11 Suppl):A233.

Citation Format: Rashida A. Karmali, Gino Miele. Pharmacodynamic Transcriptional markers of carboxyamidotriazole orotate (CTO) exposure in anagen hair. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr A233.