SAT-175 Trial in Progress Interim Report: A Phase II Clinical Trial Using Single Agent Cabozantinib in Advanced Adrenocortical Carcinoma

BACKGROUND: Adrenocortical carcinoma (ACC) in an aggressive malignancy with suboptimal response to frontline chemotherapy and without established second line treatment. cMET activation is associated with ACC resistance to chemotherapy. Cabozantinib is a multi-kinase inhibitor that targets the VEGFR, c-MET, AXL, and RET receptors. We report interim data about using cabozantinib in ACC through a prospective phase II clinical trial. Methods: This is an investigator-initiated, open label clinical trial to evaluate the efficacy and safety of cabozantinib in patients with unresectable/metastatic ACC (ClinicalTrials.gov Identifier: NCT03370718). The primary objective is 4-month progression-free survival rate (PFS4). Participants are ≥ 18 years old with histologically confirmed ACC. Subjects who used mitotane within 6 months of consent must have mitotane serum level of < 2 mg/L. Cabozantinib starting dose is 60 mg daily with possible dose reductions. Subjects stopped treatment at time of disease progression, death, or occurrence of severe adverse events. Objective tumor responses were assessed per RECIST v.1.1 criteria. Adverse effects were graded per CTCAE v.4.03 Results: At time of data cut off (Oct 28, 2019), we screened 16 patients for enrollment. Ten patients (3 females) received cabozantinib out of whom 5 had history of mitotane use. Nine patients were eligible for response evaluation, defined as having at least one follow up imaging. One patient was taken off study after one week due to hypertensive crisis. Median age at time of diagnosis was 45 years (range 32 - 72). Five patients had hormonally active ACC. Median number of prior lines of systemic therapy was 2 (range 0 -5). Median duration of cabozantinib therapy was 6.6 months (range 0.7 -11.3). Eight patients (80%) were without evidence of progression at 4 months (achieved study endpoint). At time of data cut off, 1 patient had partial response (53% reduction over 8.8 months and ongoing), 3 patients had stable disease, and 5 patients had progressive disease. Nine patients were alive with disease and one patient died (not drug related). Grade 3/4 clinical adverse events included thromboembolic events (3 patients), severe hypertension (1 patient), intracranial hemorrhage secondary to hypertensive crisis (1 patient), weight loss (1 patient), and abdominal pain (1 patient). Grade 3/4 laboratory adverse events included increased AST (2 patient), increased ALT (1 patient), increased GGT, increased amylase (1 patient), increased lipase (1 patient) and hyponatremia (1 patient). Conclusions: In this interim analysis of phase II study, majority of subjects reached the study primary endpoint (PFS4). These data are in favor of continuing study accrual to assess magnitude of response to therapy and safety profile in ACC. Aggressive blood pressure management and close monitoring of liver enzymes are crucial to ensure the safety of study subjects.