DDIS-33. SELECTIVE AND COMPLETE INHIBITION OF mTORC1 BY BI-STERIC mTOR INHIBITORS DRIVES THERAPEUTIC RESPONSE IN GLIOBLASTOMA

Autor: Tomoko Ozawa, William A. Weiss, Qi-Wen Fan, Edward G. Lorenzana, James Aggen, Kevan M. Shokat, Xujun Luo, Ozlem Aksoy, Mallika Singh, Douglas R. Wassarman, Nicholas Butowski, Robin Lea, Z. H. An, Jaqueline A.M. Smith, David R. Raleigh
Rok vydání: 2019
Předmět:
Zdroj: Neuro Oncol
ISSN: 1523-5866
1522-8517
DOI: 10.1093/neuonc/noz175.284
Popis: Activation of phosphatidylinositol 3-kinase (PI3K)/PTEN pathway and oncogenic signaling via the mechanistic target of rapamycin (mTOR) occur in a majority of high-grade glial brain tumors. Allosteric mTOR inhibitors, such as rapamycin and other rapalogs, incompletely block mTORC1 by reducing phosphorylation of some substrates, including S6K1, but not 4EBP1. In contrast, ATP-competitive inhibitors, such as sapanisertib, fully inhibit mTORC1. However these inhibitors are also active against mTORC2 and lipid kinases, likely enhancing toxicity. A new class of selective mTORC1 inhibitor that interacts with both the ATP- and FKBP12/FRB-binding sites has been developed, which we term ‘bi-steric’. The prototype bi-steric inhibitor, RapaLink-1, blocks phosphorylation of many mTORC1 substrates, including 4EBP1. Importantly, RapaLink-1 showed improved efficacy in glioblastoma models in vivo as compared to rapamycin or sapanisertib (Fan et al., Cancer Cell 2017). Revolution Medicines has developed novel next-generation bi-steric mTORC1-selective inhibitors that exhibit potent and selective (>10-fold) inhibition of mTORC1 over mTORC2 in vitro in cell line models. Two of these compounds, RM-001 and RM-006, showed sustained blockade of mTORC1 signaling, including dephosphorylation of 4EBP1, following weekly ip dosing in an orthotopic U87MG-Luc model of glioblastoma. Repeated weekly administration of these agents resulted in significantly greater anti-tumor efficacy, as assessed via tumor burden (bioluminescence imaging) and overall survival in comparison to daily sapanisertib and the rapalog everolimus, and weekly dosing of the first generation bi-steric RapaLink-1, all at maximally tolerated doses. In summary, our data demonstrate that bi-steric mTORC1 selective inhibitors elict marked anti-tumor efficacy at doses that are well tolerated in a preclinical model of glioblastoma. Our study emphasizes the importance of mTOR as a central target in glioblastoma, and showcases the therapeutic potential of novel and selective clinical bi-steric mTORC1 inhibitors under development as investigational new drugs.
Databáze: OpenAIRE
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