Inhibition of Glycogen Synthase II with RNAi Prevents Liver Injury in Mouse Models of Glycogen Storage Diseases

Glycogen storage diseases (GSDs) of the liver are devastating disorders presenting with fasting hypoglycemia as well as hepatic glycogen and lipid accumulation, which could lead to long-term liver damage. Diet control is frequently utilized to manage the potentially dangerous hypoglycemia, but there is currently no effective pharmacological treatment for preventing hepatomegaly and concurrent liver metabolic abnormalities, which could lead to fibrosis, cirrhosis, and hepatocellular adenoma or carcinoma. In this study, we demonstrate that inhibition of glycogen synthesis using an RNAi approach to silence hepatic Gys2 expression effectively prevents glycogen synthesis, glycogen accumulation, hepatomegaly, fibrosis, and nodule development in a mouse model of GSD III. Mechanistically, reduction of accumulated abnormally structured glycogen prevents proliferation of hepatocytes and activation of myofibroblasts as well as infiltration of mononuclear cells. Additionally, we show that silencing Gys2 expression reduces hepatic steatosis in a mouse model of GSD type Ia, where we hypothesize that the reduction of glycogen also reduces the production of excess glucose-6-phosphate and its subsequent diversion to lipid synthesis. Our results support therapeutic silencing of GYS2 expression to prevent glycogen and lipid accumulation, which mediate initial signals that subsequently trigger cascades of long-term liver injury in GSDs.

Abstract B20: EnCore-LNP mediated tumor delivery of MYC and CTNNB1 Dicer Substrate RNAs (DsiRNAs)

MYC and CTNNB1 are well-characterized drivers of numerous tumor types. Human and preclinical genetic evidence suggest that pharmacological intervention to reduce transactivation of MYC and CTNNB1-regulated genes would yield therapeutic benefit to many cancer patients. Since the proteins encoded by these genes are challenging to target via conventional modalities, progress in new therapeutic agents has been slow despite decades of research. RNA interference technology has enabled the inhibition of previously-undruggable genetic targets at the mRNA level, and has advanced to clinical development for several indications. DCR-MYC is a Phase I-stage lipid nanoparticle (LNP)-formulated Dicer substrate siRNA (DsiRNA), representing a potent class of RNAi triggers being developed by Dicerna Pharmaceuticals. Here we describe new preclinical data that increase our understanding of the parameters that impact tumor delivery and activity of DsiRNA. We demonstrate that the cationic lipid and PEG-lipid components of Dicerna's unique EnCore LNP platform can be modulated to improve delivery of DsiRNA to both orthotopic and spontaneous liver tumors, as well as xenograft tumors of diverse non-hepatic tissue origin. Characterization of LNP formulations with respect to plasma PK, tissue exposure and target mRNA knockdown was employed towards understanding the pharmacology of LNP-mediated tumor delivery.

Citation Format: Marc Abrams, Shanthi Ganesh, Bo Ying, Girish Chopda, Utsav Saxena, Anee Shah, Martin Koser, Rokhand Arvan, Dongyu Chen, Serena Shui, Rohan Diwanji, Wei Zhou, Benjamin Holmes, Boyoung Kim, Hailin Yang, Mihir Patel, Wendy Cyr, Wendy Cyr, Natalie Pursell, Nicole Avitahl-Curtis, Hank Dudek, Cheng Lai, Weimin Wang, Bob D. Brown. EnCore-LNP mediated tumor delivery of MYC and CTNNB1 Dicer Substrate RNAs (DsiRNAs). [abstract]. In: Proceedings of the AACR Special Conference on Myc: From Biology to Therapy; Jan 7-10, 2015; La Jolla, CA. Philadelphia (PA): AACR; Mol Cancer Res 2015;13(10 Suppl):Abstract nr B20.

Abstract 748: Novel selective orally bioavailable small molecule PAK4 allosteric modulators display antitumor activity and induce apoptosis in vitro and in vivo

P21-Activated Kinase 4 (PAK4) is a member of the PAK family of proteins that regulate cell survival, cell division and apoptosis. The six members of the PAK family are divided into two groups; Group I (PAK1, 2, 3) and Group II (PAK4, 5, 6), based upon their sequence homology and regulatory mechanisms. PAK4 is a member of the group II family of PAKs and is amplified or mutated in many cancer types. PAK4 is also a key downstream effector of the K-Ras pathway.

Methods: Flow cytometry, CellTiter AQueous One assay (MTS) and colony formation assays were used to determine compound effects on cell cycle distribution, proliferation and viability. Immunoblots were used to measure effects of compounds on protein steady state levels and phosphorylation. The breast cancer cell line, MDA-MB-468, and the mantle cell lymphoma line, Z-138, were used in xenograft models in mice to test the in vivo efficacy of these compounds.

Results: We have identified selective, orally bioavailable small molecule PAK4 allosteric modulators, which demonstrated anti-tumor activity in a variety of cancer cell lines (IC50 values = 0.005 - 1 μM). Treatment of cancer cells with these small molecules resulted in the reduction of PAK4 steady state levels and reduced phosphorylation of key growth signaling proteins such as Akt, ERK1/2, p90RSK, β-catenin, cofilin, p21, and cyclin D1. These allosteric modulators induced apoptosis through the activation of caspases 3 and 8 and subsequent cleavage of PARP. After 48 hours of compound treatment, it was found that the cancer cells were arrested at the G1 and G2 phases of the cell cycle. In addition, we have observed anti-tumor activity against Z-138 and MDA-MB-468 xenografts in mice at a daily oral dose of 10 mg/kg in the absence of any clinical signs of toxicity up to 200 mg/kg daily dose.

Conclusions: PAK4 represents a novel anti-cancer target as a major downstream effector of Ras oncogene. We have identified selective, orally-bioavailable small molecule PAK4 allosteric modulators with anti-tumor activity both in vitro and in vivo. These compounds inactivate PAK4 by directly inducing PAK4 destabilization. This represents a novel mechanism of the protein kinase inactivation involving degradation of PAK4 rather than direct inhibition of the kinase activity. Moreover, these allosteric modulators induce tumor cell growth arrest and apoptosis. Based on the in vitro and in vivo activity, these PAK4 allosteric modulators show promising results for the treatment of a wide variety of cancers.

Citation Format: William Senapedis, Erkan Baloglu, Natalie Pursell, Marsha Crochiere, Dilara McCauley, Joel Ellis, Trinayan Kashyap, Boris Klebanov, Robert Carlson, Ori Kalid, Michael Kauffman, Sharon Shacham, Yosef Landesman. Novel selective orally bioavailable small molecule PAK4 allosteric modulators display antitumor activity and induce apoptosis in vitro and in vivo. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 748. doi:10.1158/1538-7445.AM2014-748