Abstract OT2-07-02: Trastuzumab deruxtecan (DS-8201a) vs investigator's choice of treatment in subjects with HER2-positive, unresectable and/or metastatic breast cancer who previously received T-DM1: A randomized, phase 3 study
Authors: André F , Shahidi J , Lee C , Wang K , Krop IE 
Published: May 2019

Background: There is no uniform standard of care for HER2-positive breast cancer (BC) after disease progression on ado-trastuzumab emtansine (T-DM1). DS-8201a is a novel HER2-targeted antibody-drug conjugate (ADC) with a humanized HER2 antibody attached to a topoisomerase I inhibitor payload by a cleavable peptide-based linker, and with a drug-to-antibody ratio of 7 to 8. It is designed with the goal of improving critical attributes of an ADC. In an ongoing phase 1 trial, DS-8201a showed promising antitumor activity in HER2-positive BC previously treated with T-DM1 (confirmed objective response rate [ORR] of 54.5%; April 2018 data cutoff; Iwata et al, ASCO 2018). Based on preliminary results from the phase 1 trial, DS-8201a received FDA breakthrough therapy and fast track designations for metastatic BC that progressed after prior treatment with T-DM1. The pivotal, phase 2 DESTINY-BREAST01 trial in this population with HER2-positive BC who received prior T-DM1 is ongoing (Baselga et al, ASCO 2018).

Study Description: This multicenter, open-label, phase 3 trial will assess the efficacy and safety of DS-8201a in subjects with HER2-positive (IHC 3+ or IHC 2+/ISH+; confirmed by centralized testing) unresectable and/or metastatic BC whose disease progressed on or after T-DM1 (NCT03523585, DESTINY-BREAST02). Approximately 600 subjects will be randomized (2:1) to DS-8201a or investigator's choice of treatment (trastuzumab plus capecitabine or lapatinib plus capecitabine). Randomization is stratified by hormone receptor status, prior pertuzumab treatment, and history of visceral disease. DS-8201a (5.4 mg/kg) will be administered IV once every 3 weeks. Progression free survival (PFS) based on blinded, independent central review using RECIST v1.1 criteria is primary efficacy endpoint; overall survival (OS) is the key secondary endpoint. Other secondary efficacy endpoints are ORR, duration of response, clinical benefit rate, and PFS based on investigator assessment. Safety assessments include serious and treatment-emergent adverse events, physical examinations, vital signs, and clinical laboratory parameters. Health-related quality of life will also be measured. The primary analysis for PFS will occur when approximately 372 PFS events have been observed; providing 90% power to detect a hazard ratio of 0.70 in PFS (a 43% improvement in median PFS from 3.3 months with investigator's choice to 4.7 months with DS-8201a) with a 1-sided alpha of 0.025. An interim OS analysis is planned at the time of the PFS analysis. Final OS analysis will occur when approximately 428 OS events have been observed. Long-term follow-up will continue after the primary analysis every 3 months until death, withdrawal of consent, loss to follow-up, or study closure. Efficacy analyses will include all randomized subjects, and safety analyses will include all randomized subjects who received ≥1 dose of study treatment. The study will enroll subjects from approximately 160 sites including in North and South America, Europe, and Asia. For further information on this trial, contact Fabrice André at FABRICE.ANDRE@gustaveroussy.fr or visit clinicaltrials.gov.

Citation Format: André F, Shahidi J, Lee C, Wang K, Krop IE. Trastuzumab deruxtecan (DS-8201a) vs investigator's choice of treatment in subjects with HER2-positive, unresectable and/or metastatic breast cancer who previously received T-DM1: A randomized, phase 3 study [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr OT2-07-02.