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P10.13.B Repurposing neuroleptics to treat brain metastases: Clozapine as a novel therapy for melanoma brain metastases


 
 
 Around half of advanced melanoma patients develop brain metastases (BM) and survival is still measured in months. Current treatments, although increasingly effective, are not sufficient for this patient group, necessitating development of new therapeutic options. Drugs targeting BM specifically are a scarcity. However, utilizing drug repurposing, i.e. novel uses of drugs already approved for other medical conditions, may broaden available therapy options. Medications used to treat psychosis can penetrate an intact blood-brain barrier and it has been shown that patients with schizophrenia have lower incidences of certain cancer types than the rest of the population. Still, little is known on antitumor effects of neuroleptics on BM. We have preliminary data showing that the antipsychotic drug clozapine effectively inhibits growth of human melanoma brain metastasis (MBM) cell lines in vitro.
 
 
 
 We used the H1, H2, H3 and H10 MBM cell lines, as well as normal human astrocytes (NHA). Monolayer viability and IncuCyte studies were performed to determine IC50 doses. Cell migration was measured by a scratch wound assay. Apoptosis was studied by flow cytometry. Colony formation assays were performed using 2D clonogenic assays and 3D soft agar models. A protein array was used to find signaling proteins potentially affected by clozapine. The effect of clozapine on the normal brain was assessed, using a novel brain organoid model developed from fetal rat brains.
 
 
 
 A viability screening using 6 different neuroleptics showed that clozapine was most effective in inhibiting MBM cell viability, while NHA tolerated the same doses. MBM cells exhibited a dose-dependent inhibition of cell proliferation, migration, clonogenic formation and 3D growth. Flow cytometry demonstrated that apoptosis was a major mechanism of cytotoxicity. The protein array showed that CCL3, IL8 and VEGF were downstream targets of clozapine. These results are currently being confirmed by western blots. Doses significantly above MBM IC50 doses did not affect viability of brain organoids. Currently, a partnership with the Dept. of Chemistry (UiB) has been initiated to develop and test novel clozapine derivates, to find a more effective derivative with a larger therapeutic window and lesser side effects.
 
 
 
 Clozapine shows promise as a novel agent for use in cancer therapy due its favorable tolerability, small molecular size and established clinical safety.
