Chemotherapy resistance is a significant barrier to effective cancer treatment. A key mechanism of resistance at the single-cell level is the overexpression of drug transporters in the ABC family, particularly P-glycoprotein (P-gp), which leads to multidrug resistance (MDR). Inhibitors of these transporters can help re-sensitize cancer cells to chemotherapeutics. This study evaluated elacridar (GG918 and GF120918), a potent third-generation P-gp inhibitor, for its ability to reverse MDR in paclitaxel (PAC)-resistant ovarian cancer cell lines. Sensitive and PAC-resistant cells were cultured in two-dimensional (2D) and three-dimensional (3D) models.