Despite ASCO Mishap, Data Still Intriguing for Sacituzumab Govitecan in TNBC

Cynthia Sullivan

Sacituzumab govitecan (IMMU-132) had an objective response rate (ORR) of 33% in pretreated patients with triple-negative breast cancer (TNBC), according to updated findings from a phase II study reported by Immunomedics, the manufacturer of the antibody-drug conjugate.

The results were originally scheduled to be presented at the 2016 ASCO Annual Meeting; however, the study was excluded from the conference when ASCO became aware that its meeting embargo had been violated when the chairman of Immunomedics reported the results at a conference in April. The ASCO exclusion did not question the quality of the research findings, according to a statement from Immunomedics.

“Both we and our many investigators involved are disappointed that our excellent therapeutic results, achieving an interim median survival of about 14 months, may not be presented at this meeting. These results are very encouraging for TNBC patients with metastatic disease who failed multiple prior therapies,” Cynthia L. Sullivan, president and CEO of Immunomedics, said in a statement.

In the phase II study, 60 patients with metastatic TNBC received either 8 or 10 mg/kg of sacituzumab govitecan intravenously on days 1 and 8 of 21-day repeated cycles. The median number of doses was 8 (range, 1-37). Patients had progressed on at least 2 prior treatments, including a taxane. Seventy percent of patients had an ECOG performance status of 1, with the remaining 30% having an ECOG performance of 0. The median age was 54 years (range, 31-80 years).

The median number of prior therapies was 5 (range, 2-12). Prior treatments received included cyclophosphamide (93%), doxorubicin (83%), carboplatin (57%), gemcitabine (50%), capecitabine (43%), eribulin (38%), cisplatin (25%), vinorelbine (17%), and bevacizumab (13%).

As of May 2016, the ORR was 33%, with a confirmed ORR of 28% and a median duration of response of nearly 11 months. The median progression-free survival was 5.6 months and the median overall survival was 14.3 months.

Safety data for these these patients with a cutoff date of November 10, 2015 were previously reported in December at the 2015 San Antonio Breast Cancer Symposium.¹ The most common all-grade adverse events (AEs) in the 10 mg/kg arm were diarrhea (27%), nausea (27%), neutropenia (23%), vomiting (22%), alopecia (18%), anemia (17%), fatigue (17%), constipation (13%), rash (13%), and abdominal pain (10%).

The most frequently reported grade ≥3 AEs in the 10 mg/kg cohort were neutropenia (15%), leukopenia (8%), diarrhea (5%), fatigue (3%), dyspnea (3%), febrile neutropenia (2%), and anemia (2%).

Based on data from the phase II study, sacituzumab govitecan received an FDA breakthrough therapy designation in February 2016 for the treatment of patients with TNBC following at least 2 treatments for metastatic disease. Immunomedics plans to submit an application to the FDA for accelerated approval of sacituzumab govitecan in this setting based on the ongoing phase II trial. The company also plans to launch a confirmatory phase III trial by the end of the 2016, and will publish the phase II study data in a peer-reviewed journal.

1. Bardia A, Diamond R, Mayer A, et al. Safety and efficacy of anti-Trop-2 antibody drug conjugate, sacituzumab govitecan (IMMU-132), in heavily pretreated patients with TNBC. Presented at: the 2015 San Antonio Breast Cancer Symposium; San Antonio, TX; December 8-12, 2015. PD3-06.