In vitro activity: Serabelisib (also known as INK-1117, MLN-1117, and/or TAK-117) is a potent, selective, and oral bioavailable inhibitor of PI3Kα (phosphoinositide 3-kinase) isoform with IC50 of 21 nmol/L against PI3Kα. It exhibited> 100-fold selectivity relative to other class I PI3K family members (PI3Kβ/γ/δ) and mTOR, and a high degree of selectivity against many other kinase. Class IA PI3K is essential for clonal expansion, differentiation, and effector function of B and T lymphocytes. The p110δ catalytic isoform of PI3K is highly expressed in lymphocytes and plays a prominent role in B and T cell responses. Another class IA PI3K catalytic isoform, p110α, is a promising drug target in cancer but little is known about its function in lymphocytes. MLN1117 inhibits Akt phosphorylation and growth in PIK3CA mutant breast cancer cells with IC50s around 2 μM, yet has no effect on cells lacking PTEN. BCR-stimulated B cells treated with 1 μM MLN1117 displays a significant reduction (up to 50%) in the magnitude of the phosphorylated Akt (p-Akt) signal measured by intracellular flow cytometry. The effect of MLN1117 is dose-dependent

Kinase Assay: TAK-117 administration in PIK3CA-mutant tumor cell lines results in potent PI3K pathway inhibition, blockade of cellular proliferation, and apoptosis. INK1117 potently inhibits PI3K and demonstrates a greater than 100-fold selectivity relative to other class I PI3K family members and mTOR as well as a high degree of selectivity against a large panel of protein kinases. INK1117 blocks proliferation of tumor cell lines bearing PIK3CA mutations, and inhibits cellular phosphorylation and activity of AKT. However, INK1117 shows much less activity in PTEN-deficient tumor cells, which typically display constitutive PI3K pathway activation independent of PI3Kα.

Cell Assay: A total of 5000 SK-OV-3 and U87MG cell lines /well in low serum media (0.2% FBS) are seeded in triplicate wells of a 96-well flat bottom culture plate for 18 h to adhere. Media is aspirated and inhibitors in 0.2% FBS media are added to each well at the indicated concentrations. After 48 h, cell viability is determined using the MTS assay (Cell Titer 96 Aqueous One solution cell proliferation assay kit) with absorbance (490 nm) measured in a microplate spectrophotometer