CTNI-10. SACITUZUMAB GOVITECAN FOR BREAST CANCER BRAIN METASTASIS

Abstract

Breast cancer brain metastasis (BCBM) is a challenge that significantly impacts patient prognosis and quality of life. Sacituzumab govitecan (SG), an antibody-drug conjugate, has demonstrated antitumor activity and is approved for triple negative and HR+/HER2 negative metastatic breast cancer. It consists of a humanized anti-Trop-2 monoclonal antibody linked to a potent topoisomerase I inhibitor, SN-38. SG activity was tested in a breast cancer intracranial mouse model. We conducted a prospective, single center, window of opportunity trial (NCT03995706) to examine the intra-tumoral concentrations of SN-38 in patients undergoing craniotomy for breast cancer brain metastases (n = 13). We enrolled patients aged ≥18 years diagnosed with brain metastatic breast cancer to receive a single intravenous dose of SG at 10 mg/kg one day before surgical resection. Tumor and corresponding serum were collected during surgery to measure their levels of SN-38. Following recovery, patients resumed SG treatment at 10 mg/kg on days 1 and 8 of 21-day cycles and were assessed for responses by MRI every third cycle using response assessment in neuro-oncology (RANO) criteria. Trop-2 and carbonic anhydrase IX (CAIX) expression was investigated by IHC. SG significantly inhibited tumor growth and increased overall survival in mice. An average of 1953.79 ng/ml in serum and 134.3 ng/g in tissue of SN-38 was quantified in patient samples. Trop-2 expression was observed in 100% of patient tumors. 41% of the samples showed high expression of CAIX. A positive correlation between the tissue:serum [SN-38], Trop-2 and gH2AX staining was observed. Median overall survival of 34.5 months (5.7 - 35.6 months) and progression free survival of 7.4 months (2 – 24.4 months) were observed. Our data suggest that SG has therapeutic potential in patients with breast cancer brain metastasis. A prospective multicenter cooperative trial of SG for BCBM, S2007, is ongoing and an update on accrual will be provided.