P. Gómez Pardo

BACKGROUND: Sacituzumab govitecan demonstrated significant progression-free survival benefit over chemotherapy in the phase 3 TROPiCS-02 trial in patients with pretreated, endocrine-resistant hormone receptor-positive, human epidermal growth factor receptor 2-negative (HR+ and HER2-) metastatic breast cancer with limited treatment options. Here, we report the protocol-specified final analysis of overall survival and endpoints by trophoblast cell-surface antigen 2 (Trop-2) expression and other variables. METHODS: In this randomised, open-label, multicentre, phase 3 trial, which took place in 91 centres across North America (the USA and Canada) and Europe (Belgium, France, Germany, Italy, the Netherlands, Spain, and the UK), patients were randomly assigned (1:1) to receive sacituzumab govitecan or chemotherapy (eribulin, vinorelbine, capecitabine, or gemcitabine). Patients had confirmed HR+ and HER2- locally recurrent inoperable or metastatic breast cancer and had received at least one previous endocrine therapy, a taxane, and a CDK4/6 inhibitor in any setting and two to four previous chemotherapy regimens for metastatic disease. The primary endpoint was progression-free survival (previously reported and not included in this analysis), and secondary endpoints included overall survival, objective response rate (ORR), and patient-reported outcomes. Overall survival was assessed using stratified log-rank tests and Cox regression. Trop-2 expression was assessed in tumour tissue by immunohistochemistry. In the statistical testing hierarchy, ORR and patient-reported outcomes were tested sequentially if overall survival was significant. This study is registered with ClinicalTrials.gov, NCT03901339. FINDINGS: At the data cutoff date of July 1, 2022, 543 of 776 screened patients were randomly assigned between May 30, 2019, and April 5, 2021, with 272 patients in the sacituzumab govitecan group and 271 patients in the chemotherapy group. With a 12·5-month (IQR 6·4-18·8) median follow-up, 390 deaths occurred among 543 patients. Overall survival was significantly improved with sacituzumab govitecan versus chemotherapy (median 14·4 months [95% CI 13·0-15·7] vs 11·2 months [10·1-12·7]; hazard ratio [HR] 0·79, 95% CI 0·65-0·96; p=0·020); survival benefit was consistent across Trop-2 expression-level subgroups. ORR was significantly improved with sacituzumab govitecan compared with chemotherapy (57 [21%] patients vs 38 [14%]; odds ratio 1·63 [95% CI 1·03-2·56]; p=0·035), as was time to deterioration of global health status and quality of life (median 4·3 months vs 3·0 months; HR 0·75 [0·61-0·92]; p=0·0059) and fatigue (median 2·2 months vs 1·4 months; HR 0·73 [0·60-0·89]; p=0·0021). The safety profile of sacituzumab govitecan was consistent with previous studies (including the TROPiCS-02 primary analysis and the ASCENT trial). One fatal adverse event (septic shock caused by neutropenic colitis) was determined to be related to sacituzumab govitecan treatment. INTERPRETATION: Sacituzumab govitecan demonstrated statistically significant and clinically meaningful benefit over chemotherapy, with a 3·2-month median overall survival improvement and a manageable safety profile. These data support sacituzumab govitecan as a new treatment option for patients with pretreated, endocrine-resistant HR+ and HER2- metastatic breast cancer. FUNDING: Gilead Sciences.

PURPOSE Hormone receptor–positive (HR+) human epidermal growth factor receptor 2–negative (HER2–) endocrine-resistant metastatic breast cancer is treated with sequential single-agent chemotherapy with poor outcomes. Sacituzumab govitecan (SG) is a first-in-class antibody-drug conjugate with an SN-38 payload targeting trophoblast cell-surface antigen 2, an epithelial antigen expressed in breast cancer. METHODS In this global, randomized, phase III study, SG was compared with physician's choice chemotherapy (eribulin, vinorelbine, capecitabine, or gemcitabine) in endocrine-resistant, chemotherapy-treated HR+/HER2– locally recurrent inoperable or metastatic breast cancer. The primary end point was progression-free survival (PFS) by blinded independent central review. RESULTS Patients were randomly assigned to receive SG (n = 272) or chemotherapy (n = 271). The median age was 56 years, 95% had visceral metastases, and 99% had a prior cyclin-dependent kinase 4/6 inhibitor, with three median lines of chemotherapy for advanced disease. Primary end point was met with a 34% reduction in risk of progression or death (hazard ratio, 0.66 [95% CI, 0.53 to 0.83; P = .0003]). The median PFS was 5.5 months (95% CI, 4.2 to 7.0) with SG and 4.0 months (95% CI, 3.1 to 4.4) with chemotherapy; the PFS at 6 and 12 months was 46% (95% CI, 39 to 53) v 30% (95% CI, 24 to 37) and 21% (95% CI, 15 to 28) v 7% (95% CI, 3 to 14), respectively. Median overall survival (first planned interim analysis) was not yet mature (hazard ratio, 0.84; P = .14). Key grade ≥ 3 treatment-related adverse events (SG v chemotherapy) were neutropenia (51% v 38%) and diarrhea (9% v 1%). CONCLUSION SG demonstrated statistically significant PFS benefit over chemotherapy, with a manageable safety profile in patients with heavily pretreated, endocrine-resistant HR+/HER2– advanced breast cancer and limited treatment options.

LBA1001 Background: HR+/HER2– disease is the most common subtype of metastatic breast cancer (MBC). Treatment includes sequential endocrine therapy combined with targeted agents followed by single-agent chemotherapy, with increasingly shorter durations of benefit. SG is an anti–Trop-2 antibody-drug conjugate approved for metastatic triple-negative breast cancer with ≥2 prior therapies (≥1 for MBC). The HR+/HER2– MBC cohort of the phase 1/2 IMMU-132-01 study (n = 54) had an objective response rate (ORR) of 31.5%, median progression-free survival (PFS) of 5.5 mo, median overall survival (OS) of 12 mo, and a manageable safety profile with SG. TROPiCS-02 is a phase 3 randomized study (NCT03901339) to confirm SG outcomes in HR+/HER2– advanced breast cancer. Methods: Adults with locally determined, HR+/HER2– unresectable locally advanced or MBC, ECOG performance status of 0 or 1, and 2-4 prior chemotherapy regimens for MBC were eligible; 1 prior therapy for MBC was allowed if disease progressed ≤12 mo after (neo)adjuvant therapy. Pts must have received ≥1 prior taxane, CDK4/6 inhibitor, and endocrine therapy in any setting. Pts were randomized 1:1 to receive SG (10 mg/kg IV on d1 and 8, every 21d) or TPC (capecitabine, eribulin, vinorelbine, or gemcitabine) until disease progression/unacceptable toxicity. Primary endpoint was PFS per RECIST v1.1 by blinded independent central review (final analysis) with key secondary endpoint of OS (1 st planned interim analysis). Results: At data cutoff on Jan 3, 2022, 272 vs 271 pts were randomized to receive SG vs TPC, respectively. Pt characteristics in the SG vs TPC arms were similar (3 median prior chemotherapy regimens for MBC [range, 0-8]; 95% had visceral metastases, 86% had prior endocrine therapy for MBC for ≥6 mo, 60% and 38% received prior CDK4/6 inhibitors for ≤12 and > 12 mo, respectively). SG (vs TPC) improved median PFS (5.5 vs 4.0 mo; HR, 0.66; 95% CI, 0.53-0.83; P= 0.0003); PFS rates at 6 and 12 mo were 46% vs 30% and 21% vs 7%, respectively. SG vs TPC showed a numeric but nonsignificant difference in OS (13.9 vs 12.3 mo; HR, 0.84; P= 0.143); ORR (21% vs 14%) and clinical benefit rate (34% vs 22%) were higher with SG vs TPC and median duration of response was 7.4 vs 5.6 mo, respectively. Overall, 74% vs 60% of patients (SG vs TPC) had grade ≥3 treatment-emergent adverse events (AEs); neutropenia (51% vs 39%) and diarrhea (10% vs 1%) were most common. AEs leading to discontinuation of SG vs TPC were low (6% vs 4%). There was 1 treatment-related death in the SG arm; none in the TPC arm. Conclusions: SG had a statistically significant, clinically meaningful PFS benefit over single-agent chemotherapy and a manageable safety profile in pts with heavily pre-treated HR+/HER2– endocrine-resistant, unresectable locally advanced or MBC, who have limited treatment options. Clinical trial information: NCT03901339.