The mammalian target of rapamycin (mTOR) is a serine-threonine kinase that is central to two protein complexes, mTORC1 and mTORC2. These complexes are differentially regulated (e.g., only mTORC1 is sensitive to rapamycin ) and regulate different pathways. OSI-027 is an inhibitor of the catalytic site of mTOR and, as a result, inhibits both mTORC1 and mTORC2 (IC50s = 22 and 65 nM, respectively). It is selective for mTOR over phosphatidylinositol 3-kinase isoforms and DNA protein kinase. OSI-027 prohibits proliferation, induces autophagy, and potentiates apoptosis in BCR-ABL transformed cells and other cancer cells at 10 μM. OSI-027 is effective in vivo, blocking the phosphorylation of targets of mTORC1 and mTORC2 and suppressing tumor growth in several different human xenograft models.
OSI-027 is a kinase inhibitor with anti-tumor activity, used in treatment of breast cancer.
ChEBI: 4-[4-amino-5-(7-methoxy-2-indolylidene)-1H-imidazo[5,1-f][1,2,4]triazin-7-yl]-1-cyclohexanecarboxylic acid is a member of indoles.
Effects on GEO colorectal xenograft growth treated with Rapamycin or OSI-027 for 12 days are consistent with our in vitro experiments. Treatment with Rapamycin (20 mg/kg) inhibits phospho-S6 and phospho-4E-BP1, while Akt phosphorylation is increased by 29%. In contrast, OSI-027 (65 mg/kg) inhibits both mTORC1 and mTORC2 effectors. After 2 hours, decreased 4E-BP1, Akt, and S6 phosphorylation is observed and inhibition of S6 and Akt is sustained for 24 hours. The plasma drug concentration of OSI-027 inversely correlated with these effects on mTORC1 and mTORC2 signaling. The median plasma drug concentration with OSI-027 is 21.3 μM at 2 hours and 14.9 μM at 8 hours. The in vivo efficacy of OSI-027 plus Sunitinib is tested in H292 human lung and Ovcar-5 human ovarian xenograft tumors. H292 tumors, treated with OSI-027 (50 mg/kg) for 21 days have 61% median tumor growth inhibition for the duration of treatment (TGI). Sunitinib (40 mg/kg) for 21 days had 47% median TGI. Combining OSI-027 with Sunitinib, however, has a median TGI of 100% with 59% maximal tumor regression, a statistically significant improvement over either agent alone. Ovcar-5 xenograft tumors treated with OSI-027 or Sunitinib have a 55% and 68% median TGI, respectively. OSI-027 administered with Sunitinib has a significantly better median TGI of 100% with 38% maximal tumor regression[1].
In the Rapamycin (RAPA) group, three rats exhibit symptoms typical of LTx-aGVHD and die 27 to 35 days after liver transplantation (LT); the remaining five rats do not develop LTx-aGVHD symptoms and survive for more than 100 days. In contrast, seven rats in the OSI-027 group survive for more than 100 days without symptoms of LTx-aGVHD, and only one rat exhibits LTx-aGVHD symptoms and dies on day 33 after LT[3].
mTOR: 4 nM (IC50); mTORC1: 22 nM (IC50); mTORC2: 65 nM (IC50); PI3K-γ: 0.42 μM (IC50); PI3K-α: 1.3 μM (IC50); DNA-PK: 1 μM (IC50); Autophagy
[1] bhagwat s v, gokhale p c, crew a p, et al. preclinical characterization of osi-027, a potent and selective inhibitor of mtorc1 and mtorc2: distinct from rapamycin. molecular cancer therapeutics, 2011, 10(8): 1394-1406.
