Repurposing of ivacaftor shows potential to treat ROR1 expressing high-grade serous ovarian cancer.

Background: Drug repurposing has emerged as an effective strategy to accelerate drug discovery. Using the pipeline established from a large collaborative drug repurposing project focused on high-grade serous ovarian cancer (HGSOC), we identified ivacaftor, an FDA-approved cystic fibrosis medication, as a drug candidate predicted to interact with the receptor tyrosine kinase-like orphan receptor 1 (ROR1) which we have previously demonstrated as a therapeutic target in ovarian cancer. Objectives: This study aimed to provide preclinical evidence supporting the potential repurposing of ivacaftor for HGSOC treatment. Design: Ivacaftor was tested in 2D and 3D preclinical models as well as patient-derived organoid models in vitro. Methods: Dose-response analysis was undertaken in ROR1 expressing HGSOC cell lines OVCAR4, KURAMOCHI, COV362 and COV318 in both 2D adherent and 3D bioprinted formats. Real-time live/dead and apoptosis cell staining were performed over a 72 h period using the IncuCyte live cell imaging platform. Flow cytometry was used to assess apoptosis, DNA damage and cell proliferation following treatment with either 15 µM ivacaftor or 30 µM carboplatin at 24, 48 and 72 h. Additionally, ROR1-expressing HGSOC patient-derived organoids (OC029, OC043 and OC058) underwent ivacaftor dose-response analysis. Cell apoptosis following 15 µM ivacaftor treatment was measured in real-time using an Annexin V assay in two additional organoid models (OC062 and OC075). Finally, the mechanisms associated with response to ivacaftor were explored in HGSOC cell lines through Western blotting. Results: The IC50 for ivacaftor ranged from 6.5 to 13.2 µM in 2D cultures and 11.6 to 18.2 µM in 3D cultures. Treatment with 10 and 15 µM ivacaftor resulted in significantly increased cell death and reduced live cell counts compared to the vehicle control over 72 h. Organoids displayed IC50 values between 11.2 and 14.1 µM. Ivacaftor treatment induced apoptosis in organoids, with no significant impact on DNA damage or cell cycle in HGSOC cells. ROR1 signalling associated oncogenic pathways including the BMI-1 and the PI3K/AKT pathways were modulated following ivacaftor treatment. Conclusion: In summary, ivacaftor demonstrated significant anti-tumour potential in preclinical HGSOC models, supporting its further investigation as a repurposed therapy for ovarian cancer.