Fig. 1

ALRN-6924 anti-proliferative efficacy in vitro. a–c Cell line panel screening. Two cancer cell line panels (Eurofins OncoPanel and focused Horizons Discovery OncoSignature panel) of total 302 cell lines were employed to assess ALRN-6924 activity (a). Horizons Discovery OncoSignature panel of 89 cell lines was used to compare three MDM2/MDM4 inhibitors, ALRN-6924, RG7112, and RG7388 (b). The effect of ALRN-6924 on breast cancer was assessed in 23 breast cancer cell lines (c). For these screening assay (a–c), cells seeded into 384-well plates overnight were treated the inhibitors at serially diluted concentrations for 72 h. EC₅₀ (equally IC₅₀, half-maximal inhibitory concentration) was determined using relative cell proliferation rate assessed by changes in nuclear dye uptake or ATP levels. d Effect of ALRN-6924 on breast cancer cell lines with different ER status. Cells, seeded in 96-well plates, were treated with ALRN-6924 at serially diluted concentrations for 72 h. Cell proliferation was determined using SRB assay. IC₅₀ was calculated using CalcuSyn. Data represent mean ± SD obtained from three replicates. e–h Colony formation assay. ER+ breast cancer cell lines MCF-7 (e, f) and ZR-75-1 (g, h), seeded in 6-well plates, were cultured in the presence of vehicle or ALRN-6924 at different concentrations for 2–3 weeks followed by crystal violet staining. Colony images show representative wells (e, g). Total colony area (pixel^2) was measured by using NIH ImageJ software (f, h). Data represent mean ± SD from triplicates