Abstract P1-14-04: A Phase 0 Clinical trial of Sacituzumab Govitecan in Patients with Breast Cancer Brain Metastases and Recurrent Glioblastoma

Abstract

Abstract Purpose: Sacituzumab govitecan has shown efficacy and acceptable tolerability in a multicenter phase I/II clinical trial (NCT01631552) in patients with advanced epithelial cancers. Our study was initiated to determine the bioavailability of Sacituzumab govitecan (SG) in breast brain metastasis and glioblastoma. The goals were to evaluate the extent by which SG can penetrate the blood brain barrier and access tumor tissues by testing free SN-38, SN-38G and total SN-38 concentrations in tumor tissue, serum, and CSF. Patients and methods: Patients diagnosed with brain metastatic breast cancer and recurrent glioblastoma were enrolled in a single-center clinical phase 0 study 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 and its metabolites. 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. Total Sn-38 levels were quantified in tumor tissue and corresponding serum from the patients. Trop-2 and carbonic anhydrase IX (CAIX) expression was investigated by IHC. SG activity was tested in a breast cancer intracranial mouse model. Results: An average of 2365 ng/ml in serum and 132 ng/g in tissue of total SN-38 was quantified in our patient samples. Trop-2 expression was observed in 90% of patient tumors. 40% of the samples showed high expression of CAIX. SG significantly inhibited tumor growth in vivo and increased overall survival. 20% of patients in the breast cancer arm of the trial demonstrated a complete response by RANO criteria and the remaining 80% of patients demonstrated a partial response. Ultimately, 80% of the patients in the breast cancer metastasis arm survived. Conclusion: Sacituzumab govitecan is an effective drug that crosses the blood brain barrier to inhibit the growth of metastatic breast cancer to the brain after tumor resection surgery. Citation Format: Pegah Ghamasaee, Henriette Balinda, Andrew Brenner, John Floyd. A Phase 0 Clinical trial of Sacituzumab Govitecan in Patients with Breast Cancer Brain Metastases and Recurrent Glioblastoma [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P1-14-04.