Targeted therapy combinations with ipatasertib in multi-cell type 3D tumor spheroid models
We evaluated the growth-inhibitory effects of the pan-AKT inhibitor ipatasertib in combination with other targeted therapies. Thirty-nine patient-derived cancer cell lines from the NCI Patient-Derived Models Repository, along with nine NCI-60 tumor cell lines, were cultured as mct-spheroids. These mct-spheroids consisted of a mix of tumor cells (60%), endothelial cells (25%), and mesenchymal stem cells (15%) and were allowed to establish for three days before treatment. Compounds were tested at concentrations up to their reported clinical Cmax or a maximum of 10 μM. After seven days of exposure, cell viability was assessed using the CellTiter-Glo 3D assay. Ipatasertib selectively inhibited tumor cells harboring activating mutations in the PI3K/AKT/mTOR pathway. Dual targeting of the PI3K/AKT/mTOR and RAS/MEK/ERK pathways showed strong efficacy. Combining ipatasertib with the MEK inhibitor selumetinib or the ERK inhibitor ravoxertinib produced additive or synergistic cytotoxic effects in about half of the cell lines tested. In cell lines carrying the BRAF V600E mutation or the KRAS G12C mutation, ipatasertib combined with the mutation-specific inhibitors vemurafenib and sotorasib, respectively, demonstrated significant activity. Additionally, vertical inhibition of the PI3K/AKT/mTOR pathway using the mTORC1/2 kinase inhibitor sapanisertib resulted in additive or synergistic effects across multiple cell lines. Early studies revealed a correlation between the responses to ipatasertib and selumetinib in two patient-derived tumor lines grown as mct-spheroids and their corresponding patient-derived xenografts. All experimental data are publicly available through the PubChem BioAssay database.