Atsp-9172, A Novel Stapled Peptide Inhibitor Of Hif-Dependent Transcriptional Activity With In Vivo Antitumor Efficacy In A Preclinical Model Of Prostate Cancer.

Proceedings: AACR 104th Annual Meeting 2013; Apr 6-10, 2013; Washington, DC Hypoxia-inducible transcription factors (HIF) are key regulators of cellular adaptation to hypoxia in solid tumors, and HIF-1α controls the expression of genes involved in anaerobic metabolism, angiogenesis, cell growth and survival. Hydrocarbon cross-linked alpha helical peptides (Stapled Peptides) are a breakthrough approach to create new class of drugs that modulate intracellular protein-protein interactions. Here, we have mimicked the structure and function of the CITED2 protein, an endogenous negative regulator of the interaction between HIF-1α and p300 proteins, by designing a Stapled Peptide derived from CITED2 to generate the first example of a potent and selective Stapled Peptide inhibitor of HIF-1α-dependent transcription. ATSP-9172 bound to the CH1 domain of p300 and disrupted the HIF-1α C-TAD/CH1 interaction in biochemical assays and inhibited HIF-dependent reporter gene activity in ME-180 cells. Examination of endogenous transcript levels in ME-180 cells revealed that ATSP-9172 down-regulated the transcription of HIF-1α target genes, such as adolase C, angiopoietin-like 4, and carbonic anhydrase 9 in a dose-dependent manner, but did not affect the expression of non-HIF target genes, verifying a specific and on-target mechanism of action. ATSP-9172 exhibited a dramatic improvement in solubility and plasma stability profile relative to the linear peptide, and demonstrated favorable pharmacokinetic properties in mice by providing high systemic exposure, low plasma clearance and long elimination half-life. Finally, intravenous administration of ATSP-9172 on an every other day schedule significantly inhibited tumor growth in a PC-3 human prostate tumor xenograft model (p < 0.05); this inhibition was found to be dose-dependent. Our results demonstrate that a Stapled Peptide mimicking the HIF inhibitory function of the native CITED2 protein provides a novel and specific strategy to suppress HIF-1α-dependent gene expression for cancer therapy. Citation Format: Kaiming Sun, Steven J. DeMarco, Vincent Guerlavais, Aditi Mukherjee, Sean Irwin, Eric Shi, Hongliang Cai, Krzysztof Darlak, Solimar Santiago, Jessica Pero, Karen A. Olson, Huw M. Nash, Yong Chang. ATSP-9172, a novel Stapled Peptide inhibitor of HIF-dependent transcriptional activity with in vivo antitumor efficacy in a preclinical model of prostate cancer. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr LB-304. doi:10.1158/1538-7445.AM2013-LB-304