Sapanisertib (INK 128) is an orally bioavailable inhibitor of raptor-mTOR (TOR complex 1 or TORC1) and rictor-mTOR (TOR complex 2 or TORC2) with potential antineoplastic activity.

PI3Kδ:230 nM, PI3Kβ:5.293 μM, PI3Kα:219 nM, mTOR:1.4 nM(Ki), PI3Kγ:221 nM

Administering INK 128 orally on a daily basis to various transplant model systems inhibits angiogenesis and tumor growth. Daily treatment of the ZR-75-1 breast cancer xenograft model with 0.3 mg/kg of INK 128 demonstrated a suppressive effect on tumor growth.

INK 128 functions as a dual inhibitor of TORC1/2, suppressing the phosphorylation of TORC1's downstream substrates S6 and 4EBP1, while selectively inhibiting the phosphorylation of AKT on Ser473, a downstream substrate of TORC2. It exhibits enzymatic inhibitory activity against mTOR, presenting over 100-fold selectivity towards PI3K kinases. Moreover, INK 128 effectively inhibits cell lines resistant to rapamycin and pan-PI3K inhibitors.

mTOR activity is assayed using LanthaScreen Kinase kit reagents. PI(3)K α, β, γ and δ activity are assayed using the PI(3)K HTRF assay kit. The concentration of INK128 necessary to achieve inhibition of enzyme activity by 50% (IC50) is calculated using concentrations ranging from 20 μM to 0.1 nM (12-point curve). IC50?values are determined using a nonlinear regression model.

PC3 cells are treated with the appropriate drug for 48 h, and proliferation is measured using CellTiter-Glo Luminescent reagent. The concentration of INK128 necessary to achieve inhibition of cell growth by 50% (IC50) is calculated using concentrations ranging from 20.0 μM to 0.1 nM (12-point curve).