In vitro activity: Tenalisib displays selectivity over PI3K α (>300-fold) and β (>100-fold) isoforms. Tenalisib exhibits modest proliferation inhibition (33-46% inhibition @ 10 μM) in both HEL-RS and HEL-RR cells. Addition of 10 μM tenalisib to ruxolitinib is synergistic resulting in a near-complete inhibition of proliferation (>90% for HEL-RS and>70% for HEL-RR). Addition of 5 μM tenalisib, 4 h prior to the addition of ruxolitinib results in a significant reduction in EC50of ruxolitinib (5.8 μM) in HEL-RR cells. Incubation of 10 μM tenalisib with ruxolitinib for 72 h increases the percent of apoptotic cells (55% in HEL-RS and 37% in HEL-RR) compared to either agent alone (16-27% in HEL-RS and 17-21% in HEL-RR).

Kinase Assay: RP6530 is a specific dual PI3K δ/γ inhibitor exhibiting several-fold selectivity against the other PI3K isoforms and 245-kinases. RP6530 causes a dose-dependent inhibition (>50% @ 2-7 μM) in growth of immortalized (Raji, TOLEDO, KG-1, JEKO, REC-1) B-cell lymphoma cells. Effect is more pronounced in the DLBCL cell lines, OCI-LY-1 and OCI-LY-10 (>50% inhibition @ 0.1-0.7 μM), and the reduction in viability is accompanied by corresponding inhibition of pAKT with EC50 of 6 & 70 nM respectively. Treatment of patient-derived primary cells with 4 μM RP6530 causes an increase in cell death. Cells in early apotosis (Annexin V+/PI-) are not different between the DMSO blank and RP6530 samples. RP6530 shows potent inhibitory effect on cancer stem cells in ovarian cancer cell lines. Treatment with 1 μM RP6530 results in G2/M arrest in MM-1S and MM-1R lines with very few cells in the SubG0 phase. It also results in a 70–90% inhibition of pAKT in MM-1S and MM-1R cell lines. Potent modulation of inflammatory response by RP6530 contributes to control tumor microenvironment.

Cell Assay: Potential of the combination (1 μM RP6530 + BORT between 0.1 nM and 1 μM) is studied in MM cell lines, namely, MM-1S and MM-1R. Proliferation is determined by a MTT assay after incubating with compound for 72 h at 37oC. Apoptotic potential of the combination is estimated by AnnexinV/PI staining.