Fig. 4

Fenebrutinib inhibits downstream pathways linked to FcγR activation and LPC exposure in IMHBOs. A Immunoreactivity of BTK and Iba1 in IMHBOs showing overlap between BTK expression in iMicroglia in IMHBOs. Scale bar is 100 µm. B TNF-α release from IMHBOs incubated with fenebrutinib (1 μM) and stimulated with Agg IgG (1 mg/mL; 24 h) or LPC (0.1 mM; 72 h). Fenebrutinib treatment reduced Agg IgG- and LPC-induced TNF-α release. C Heatmap showing top differentially expressed genes from annotated gene sets in IMHBOs treated with fenebrutinib (1 μM) and stimulated with Agg IgG (1 mg/mL; 24 h) or LPC (0.1 mM; 72 h). D NfL levels in supernatants of IMHBOs incubated with fenebrutinib (0.01–1 μM) and stimulated with Agg IgG (1 mg/mL; 24 h) or LPC (0.1 mM; 72 h). Fenebrutinib treatment significantly reduced LPC-induced NfL release. Data are shown as mean ± SD; individual dots represent replicate wells from single organoids. Significance is indicated by ****P < 0.0001, ***P < 0.001, **P < 0.01 and *P < 0.05, determined by one‐way ANOVA and Tukey’s post hoc test. Agg IgG heat-aggregated immunoglobulin G, ANOVA analysis of variance, BTK Bruton’s tyrosine kinase, FcγR Fc gamma receptor, FEN fenebrutinib, Iba1 ionized calcium-binding adaptor molecule 1, IMHBO immunocompetent human brain organoid, iMicroglia induced pluripotent stem cell-derived microglia, LPC lysolecithin, NfL neurofilament light chain, SD standard deviation, TNF tumor necrosis factor