Panulisib

The mTOR pathway is often upregulated in cancer and thus intensively pursued as a target to design novel anticancer therapies. Approved and emerging drugs targeting the mTOR pathway have positively affected the clinical landscape. Recently, activin receptor-like kinase 1 (ALK1), belonging to the TGFβ receptor family, has been reported as an emerging target for antiangiogenic cancer therapy. Here, we describe a novel orally efficacious compound, P7170, that inhibits mTORC1/mTORC2/ALK1 activity with a potent cell growth inhibition. In cell-based assays, P7170 strongly inhibited (IC50 < 10 nmol/L) the phosphorylation of p70S6K (T389) and pAKT (S473). In many cancer cell lines, such as prostate, ovarian, colon, and renal, P7170 treatment resulted in marked cell growth inhibition. Furthermore, it induced G1–S cell-cycle arrest and autophagy. In vitro HUVEC tube formation, in vivo Matrigel plug, and rat aorta ring assays demonstrated that P7170 exhibited significant antiangiogenic activity. In addition, ALK1 knockdown studies in HUVEC confirmed that the antiangiogenic activity of P7170 was primarily due to ALK1 inhibition. Strong inhibition of ALK1 in addition to mTORC1/mTORC2 differentiates P7170 in its mechanism of action in comparison with existing inhibitors. In vivo mouse xenograft studies revealed P7170 to exhibit a significant dose-dependent tumor growth inhibition in a broad range of human tumor types when administered orally at 10 to 20 mg/kg doses. The distinctive pharmacological profile with favorable pharmacokinetic parameters and in vivo efficacy makes P7170 an attractive candidate for clinical development. It is currently being tested in phase I clinical studies. Mol Cancer Ther; 14(5); 1095–106. ©2015 AACR.

Activation of the phosphatidylinositol 3-kinase (PI3K)/AKT/mTOR pathway has been implicated in anti-estrogen resistance in breast cancer. We tested the therapeutic potential of the novel PI3K/mTOR dual inhibitor P7170 in a panel of anti-estrogen-sensitive and anti-estrogen-resistant models of ER+ breast cancer. Estrogen receptor-positive (ER+) breast cancer cells were treated ±P7170. Fresh cores from primary ER+/HER2- tumors from two patients were treated ±P7170 ex vivo. Mice bearing breast cancer xenografts were randomized to treatment with vehicle, fulvestrant, P7170, or combinations, and tumor volumes were measured. Tissues and cells were analyzed for markers of pathway activity, cell viability, and apoptosis. In cell lines, P7170 exhibited IC50 values in the range of 0.9-7 nM and induced apoptosis. P7170 potently inhibited mTOR activity (≤ 25 nM) and inhibited PI3K at higher concentrations (≥ 200 nM). P7170 completely inhibited MCF-7 tumor growth, significantly inhibited growth of fulvestrant-resistant T47D tumors, and suppressed tumor cell proliferation but did not induce apoptosis. While P7170 inhibits PI3K and mTOR in ER+/HER2- human breast cancer cells and tumors ex vivo, in vivo data indicate that the primary mechanism of P7170 anti-tumor action is inhibition of mTOR and cell proliferation. P7170 is a novel agent worthy of further investigation for the treatment of ER+ breast cancer.