After a median follow-up of 15.8 months, patients within the mCRPC cohort who received the combination achieved an objective response rate of 33%.
Data from the COSMIC-021 trial presented during the 2020 ASCO Virtual Scientific Program shows that the combination of Cabometyx (cabozantinib) and Tecentriq (atezolizumab) was effective in patients with metastatic castration-resistant prostate cancer (mCRPC).
“The combination of cabozantinib and atezolizumab demonstrated a tolerable safety profile and clinically meaningful activity in men with mCRPC,” said lead study author Dr. Neeraj Agarwal, director the Genitourinary Oncology Program at Huntsman Cancer Institute.
Agarwal shared data for the first 44 patients enrolled in the mCRPC cohort within the multicenter, open-label phase 1b COSMIC-021 trial, which aims to evaluate the objective responses and safety associated with the combination of Cabometyx and Tecentriq in patients with locally advanced or metastatic solid tumors. Patients who had hormone-sensitive disease, and had received prior docetaxel treatment, were permitted to enter the study.
The patients (77% white; 4.5% black) received Cabometyx orally at 40 milligrams (mg) once daily and intravenous Tecentriq at 1200 mg every three weeks. Objective response rate (ORR), which is the proportion of patients who had a complete or partial response to treatment, served as the study’s primary outcome.
Most of the patients (82%) had high-risk mCRPC, which was defined as having visceral and/or extra-pelvic lymph node metastases. All patients within this portion of the study had received previous novel hormonal therapy, including Zytiga (abiraterone acetate), Xtandi (enzalutamide), Erleada (apalutamide), or Nubeqa (darolutamide). Additionally, 27% of patients received docetaxel before entering the study to treat metastatic castration-sensitive disease. The median time between most recent systemic therapy and enrollment was 1.3 months. Overall, 70% of patients had prior radiotherapy and 80% of patients had prior surgery for prostate cancer.
After a median follow-up of 15.8 months, patients within the mCRPC cohort who received the combination achieved an ORR of 33%. Among the 44 patients, there were three complete responses and 11 partial responses. Eight patients had progressive disease and 21 had stable disease. Agarwal noted that the disease control rate was 80%.
Median time for disease to respond to therapy was 1.6 months, and the median duration of response was 8.3 months. A subgroup of 36 patients who had high-risk clinical features achieved an ORR of 33%.
More than half (59%) of patients experienced grade 3 and grade 4, which are considered more serious, side effects. The most common treatment-related grade 3 and grade 4 side effects included fatigue, diarrhea and hyponatremia, which is when sodium levels in the blood are too low.
Nineteen patients had their Cabometyx doses reduced as a result of their side effects. Additionally, four patients experienced side effects unrelated to disease progression but led to discontinuation of both study drugs.
“[The mCRPC cohort] is being further expanded, and cohorts evaluating the contribution of cabozantinib and atezolizumab have been initiated,” Agarwal concluded during his presentation. “Further evaluation of cabozantinib and atezolizumab in mCRPC in a phase 3 trial is planned.”
A version of this story originally appeared on OncLive® as “Cabozantinib Plus Atezolizumab Shows Promise in mCRPC”.