SUMMARY: Breast cancer is the most common cancer among women in the US and about 1 in 8 women (12%) will develop invasive breast cancer during their lifetime. Approximately 290,560 new cases of breast cancer will be diagnosed in 2022 and about 43,780 individuals will die of the disease, largely due to metastatic recurrence. Approximately 70% of breast tumors in patients with metastatic disease are Estrogen Receptor (ER) and/or Progesterone Receptor (PR) positive and HER2-negative. These patients are often treated with single agent endocrine therapy, endocrine therapy in combination with CDK4/6 inhibitor, or single agent chemotherapy. Resistance to hormonal therapy occurs in a majority of the patients and there is therefore an unmet need for agents with novel mechanisms of action.
TRODELVY® (Sacituzumab govitecan) is an Antibody-Drug Conjugate (ADC) in which SN-38, an active metabolite of Irinotecan, a Topoisomerase I inhibitor, is coupled to the humanized Anti-Trophoblast cell-surface antigen 2 (Trop-2) monoclonal antibody (hRS7 IgG1κ), through the cleavable CL2A linker. SN-38 cannot be given directly to patients because of its toxicity and poor solubility. Trop-2, a transmembrane calcium signal transducer, stimulates cancer-cell growth, and this cell surface receptor is overexpressed in several epithelial cancers including cancers of the breast, colon and lung, and has limited expression in normal human tissues. Trop-2 is expressed in more than 85% of breast tumors including Triple Negative Breast Cancer. Upon binding to Trop-2, the anti-TROP-2 monoclonal antibody is internalized and delivers SN-38 directly into the tumor cell, making it a suitable transporter for the delivery of cytotoxic drugs. Further, the cleavable linker enables SN-38 to be released both intracellularly into the tumor cells, as well as the tumor microenvironment, thereby allowing for the delivery of therapeutic concentrations of the active drug in bystander cells to which the conjugate has not bound. Thus, TRODELVY®-bound tumor cells are killed by intracellular uptake of SN-38, whereas the adjacent tumor cells are killed by the extracellular release of SN-38.
TRODELVY® was approved by the FDA in 2021 for patients with unresectable, locally advanced or metastatic Triple Negative Breast Cancer, who have received two or more prior systemic therapies, at least one of them for metastatic disease. In the IMMU-132 Phase I/II study, the Hormone Receptor positive (HR+)/HER2-negative cohort of patients with metastatic breast cancer patients had an Objective Response Rate (ORR) of 31.5%, median Progression Free Survival (PFS) of 5.5 months and median Overall Survival (OS) of 12 months, with manageable toxicities, when treated with TRODELVY®.
TROPiCS-02 is a global, open-label, randomized, Phase III study, conducted to confirm the benefit of TRODELVY® in HR+/HER2- negative advanced breast cancer. In this study, 543 patients with HR+/HER2-negative, unresectable, locally advanced or metastatic breast cancer, were randomly assigned 1:1 to receive TRODELVY® 10 mg/kg IV on D1 and 8, every 21 days (N=272), or treatment of physician’s choice, which included single agent treatment with either Capecitabine, Eribulin, Vinorelbine, or Gemcitabine (N=271). Treatment was continued until disease progression or unacceptable toxicity. Both treatment groups were well balanced. Eligible patients had 3 median prior chemotherapy regimens for metastatic breast cancer, and one prior therapy for metastatic breast cancer was allowed if disease progressed in 12 months or less after neoadjuvant chemotherapy. Patients were required to have received endocrine therapy, a CDK4/6 inhibitor and at least one prior therapy with a Taxane in any setting. Majority of patients had visceral metastases (95%), 86% had prior endocrine therapy for metastatic breast cancer for at least 6 months, and 60% and 38% received prior CDK4/6 inhibitors for 12 months or less, and for more than 12 months, respectively. The Primary endpoint was Progression Free Survival (PFS) by blinded Independent Central Review (final analysis) and key Secondary endpoint was Overall Survival (OS) at the first planned interim analysis.
The median Progression Free Survival was 5.5 months with TRODELVY® versus 4 months with standard chemotherapy (HR=0.66; P=0.0003), representing a 34% improvement in PFS with TRODELVY®. This benefit was seen across all treatment subgroups including those who were 65 years or older, those who were heavily pretreated, as well as those with visceral metastases. The Objective Response Rate (ORR) was 21% with TRODELVY® versus 14% with standard chemotherapy. The Clinical Benefit Rate was also higher with TRODELVY® versus standard chemotherapy (34% versus 22%) and median duration of response was 7.4 months and 5.6 months respectively. Overall Survival data were immature, but there was a numerical, non-significant improvement in the median Overall Survival noted in the TRODELVY® group, compared to the standard chemotherapy group (13.9 months versus 12.3 months; HR=0.84; P=0.14), respectively. Treatment with TRODELVY® also resulted in an overall health-related Quality of Life benefit over chemotherapy, with delayed deterioration in fatigue and global health status/ Quality of Life scales, according to the researchers. Grade 3 or more adverse events were observed in 74% of patients receiving TRODELVY® and in 60% of those receiving chemotherapy, and the most common toxicities associated with TRODELVY® were diarrhea and neutropenia.
It was concluded from this landmark analysis that treatment with TRODELVY® resulted in a statistically significant and clinically meaningful improvement in Progression Free Survival, compared to standard chemotherapy, in heavily pre-treated patients with HR+/HER2-negative, endocrine-resistant, unresectable, locally advanced or metastatic breast cancer, and should therefore be considered as a new treatment option for this patient population.
Primary results from TROPiCS-02: A randomized phase 3 study of sacituzumab govitecan (SG) versus treatment of physician’s choice (TPC) in patients (Pts) with hormone receptor–positive/HER2-negative (HR+/HER2-) advanced breast cancer. Rugo HS, Bardia A, Marmé F, et al. J Clin Oncol 40, 2022 (suppl 17; abstr LBA1001)