The underlying mechanisms of lorlatinib penetration across the blood‐brain barrier and the distribution characteristics of lorlatinib in the brain

OBJECTIVE: To clarify the distribution of lorlatinib in the brain and elucidate the molecular mechanisms of lorlatinib penetration across the blood‐brain barrier (BBB). METHODS: Cytological experiments were performed to investigate the growth inhibitory effect of lorlatinib on different cells (endothelial cells HUVEC, HMEC‐1, and HCMEC/D3) and to investigate the protective effect of lorlatinib on neuronal cells after SH‐SY5Y hypoxia/reoxygenation injury. Furthermore, rat brain tissue was sequenced, and the differentially expressed genes (secreted phosphoprotein 1 (SPP1), vascular endothelial growth factor (VEGF), transforming growth factor beta (TGF‐β), Claudin, ZO‐1 and P‐gp) in several different drug treatment groups were verified by Real‐Time PCR. Lorlatinib brain distribution was predicted by physiologically based pharmacokinetics (PBPK). RESULTS: Lorlatinib and crizotinib both had inhibitory effects on endothelial cells, however lorlatinib inhibited the growth of HCMEC/D3 more efficaciously than crizotinib. In the SH‐SY5Y hypoxia model, lorlatinib had a greater protective effect on nerve cell damage caused by hypoxia and reoxygenation than crizotinib. The expression of SPP1, VEGF, TGF‐β, and Claudin in brain tissue was significantly downregulated after lorlatinib administration, and the expression level of early growth transcription factor 1 (Egr‐1) was significantly increased. The PBPK model successfully described lorlatinib concentrations in blood and brain tissue in the mouse model and gave a brain tissue partition coefficient of 0.7. CONCLUSION: Lorlatinib can increase the permeability of the blood‐brain barrier whereby we suggest its underlying working mechanism is related to downregulating SPP1, inhibiting VEGF, TGF‐β, and Claudin subsequently reducing the number of tight junctions between BBB cells. Lorlatinib plays a protective role on injured nerve cells and does not change the amount of P‐gp expression in brain tissue, which may be important for its ability to be efficacious across the BBB with a low incidence of resistance.