CYH33 methanesulfonate is a highly selective and orally active inhibitor of PI3Kα, with IC50 values of 5.9 nM, 598 nM, 78.7 nM, and 225 nM against the α, β, δ, and γ isoforms, respectively. This compound effectively inhibits the phosphorylation of Akt and ERK, leading to a significant G1 phase arrest in breast cancer cells and non-small cell lung cancer (NSCLC) cells. Additionally, CYH33 methanesulfonate demonstrates potent activity against solid tumors.

PI3Kδ:78.7 nM (IC50), PI3Kβ:598 nM (IC50), PI3Kα:5.9 nM (IC50), PI3Kγ:225 nM (IC50)

CYH33 methanesulfonate demonstrates inhibitory effects on cell proliferation, showing IC50 values below 1μM in 56% (18/32) of breast cancer cell lines tested. In a concentration-dependent manner, CYH33 (0.012-1 μM; 24 hours) significantly arrests T47D and MCF7 cells in the G1 phase and concurrently diminishes the phosphorylation of ERK and Akt in these cells (4-1000 nM; 1 hour), indicating targeted action on key cell cycle and survival pathways. However, it does not induce apoptosis in MCF7 and MDA-MB-231 cells (0.11-1 μM; 24 hours). Cell cycle analysis further confirmed that CYH33 arrests sensitive T47D and MCF7 cells in the G1 phase in a concentration-dependent manner, reducing the S phase cell population, with minimal effects on the resistant MDA-MB-231 cell cycle distribution. Western blot analysis supports these findings, showing inhibited phosphorylation of ERK and Akt in sensitive cell lines without significant impact on phosphorylated ERK (pERK) in MDA-MB-231 cells up to 1μM.

Administered orally at doses ranging from 2-20 mg/kg once daily for 21 days, CYH33 methanesulfonate effectively inhibits tumor growth in SCID mice implanted with human breast cancer T47D xenografts. At the highest dosage (20 mg/kg), it significantly reduces phosphorylated Akt levels in tumor tissues, indicating the suppression of the PI3K signaling pathway. Additionally, CYH33 methanesulfonate, at a dosage of 10 mg/kg given daily for 18 to 20 days, delays the recovery of blood glucose levels and increases the area under the curve (AUC) for blood glucose in T47D xenograft and R26-Pik3ca H1047R; MMTV-Cre mice models. The study shows a minimal inhibitory effect on tumor growth at lower doses (2 and 5 mg/kg), while doses of 10 or 20 mg/kg significantly reduce tumor growth, with T/C values of 58.36% and 49.42%, respectively.