Abstract PD1-08: Oral paclitaxel and encequidar (oPac+E) versus IV paclitaxel (IVPac) in the treatment of metastatic breast cancer (mBC) patients (study KX-ORAX-001): Progression free survival (PFS) and overall survival (OS) updates

Background: IVPac is widely used to treat patients with breast cancer. oPac+E is oral paclitaxel in combination with Encequidar, an oral, minimally absorbed, specific p-glycoprotein inhibitor that enables the absorption of oral paclitaxel. Results of the phase III trial, KX-ORAX-001, were presented at SABCS, 2019, Abstract # GS6-01. At the time of the database lock for the final analysis of the primary endpoint of confirmed tumor response rate, analyses of PFS and OS were performed. The confirmed tumor response rate was significantly higher in the oPac+E group vs IVPac (35.8% vs 23.4%, p=0.011 ITT, population). The median overall survival was 27.7 months vs 16.7 months, respectively favoring oPac. An update of the duration of response, PFS and OS data comprising an additional 14 months follow-up will be presented. At the time of the update it is projected that approximately 60% of subjects will have had a survival event. Methods: Study KX-ORAX-001 was a phase III, randomized, international study in women with mBC for whom treatment with IVPac was recommended. Eligible patients were randomized 2:1 to receive oPac+E or IVPac. Patients continued treatment until discontinuation due to progressive disease or toxicity. oPac 205 mg/m2 was given once daily for 3 days weekly. E 12.9 mg was given 1 hour before each dose of oPac. IVPac 175 mg/m2 was infused over 3 hours every 3 weeks. The primary endpoint was efficacy defined as tumor response confirmed by BICR at two consecutive evaluations. Key secondary endpoints included PFS, OS. Safety was monitored throughout the study. Results: A total of 402 mBC patients were randomized (oPac+E 265: IVPac 137) and represent the ITT population of which 399 subjects were dosed. Updated data for duration of response, PFS and OS for the ITT and prespecified mITT populations will be presented. (NCT 02594371) Citation Format: G Umanzor, H S Rugo, F J Barrios, R H Vasallo, M A Chivalan, S Bejarano, J R Ramirez, L Fein, R D Kowalyszyn, D L Cutler, D Kramer, J Goldfinch, H Wang, T Moore, R MF Kwan. Oral paclitaxel and encequidar (oPac+E) versus IV paclitaxel (IVPac) in the treatment of metastatic breast cancer (mBC) patients (study KX-ORAX-001): Progression free survival (PFS) and overall survival (OS) updates [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PD1-08.