Ovarian cancer (OC) remains largely incurable due to the emergence of multidrug resistance (MDR) following platinum–taxane therapy through rewiring of DNA repair, metabolism, and drug efflux pathways. Strategies capable of collapsing this stress-adaptation network remain limited [1]. We developed BBIT20, a first-in-class small-molecule disruptor of the BRCA1–BARD1 interaction, essential to homologous recombination (HR) repair and genome stability.
BBIT20 was evaluated in BRCA-proficient and -mutated OC cell lines, MDR cells, patient-derived organoids (PDOs), and xenograft and patient-derived xenograft (PDX) mouse models. Activity was assessed alone and in combination with paclitaxel, carboplatin, and PARPi. Mechanistic studies included DNA repair profiling, apoptosis, and immune-evasion markers.
BBIT20 displayed BRCA status-independent cytotoxicity (IC50 4–6 µM), favorable selectivity over non-tumoral cells, and retained activity in MDR models without cross-resistance. In wtBRCA1 PDOs, BBIT20 reduced BRCA1 and RAD51 levels, inducing DNA damage and apoptosis consistent with HR collapse. BBIT20 also modulated the E2F1-c-MYC-HDAC3 axis, triggered mitochondrial stress, and reduced ABCB1 drug-efflux expression.
Combination therapy showed strong synergy with paclitaxel, carboplatin, and PARPi (CI 0.08–<1), reducing effective doses by up to 20-fold in both sensitive and resistant OC models. In vivo, BBIT20 (2 mg/kg) reduced ascites formation and tumor burden in PDX models and achieved greater tumor growth inhibition than olaparib in xenografts. Combination therapy further supressed proliferation, HR and NHEJ repair, EMT, and angiogenesis markers while remaining well tolerated.
BBIT20 induces DNA repair–metabolic stress collapse and resensitizes MDR tumors to platinum, taxanes, and PARP inhibitors, supporting its development for refractory OC.
[1] Uboveja A et al. (2024)
Acknowledgments: This work was supported by FCT/MCTES through Project 2024.13556.PEX (https://doi.org/10.54499/2024.13556.PEX). A.C. Matos is supported by fellowship UI/BD/154513/2023. An international patent covering BBIT20 has been filed by S. Mulhovo, M.J. Ferreira, and L. Saraiva. L. Saraiva and M.J. Ferreira are co-founders of BBIT-Therapeutics, Lda.
