• 10 new cohorts added
• 8 cohorts added in January of 2018
• Trial could include up to 640 patients total

Exelixis, Inc. (Nasdaq:EXEL) announced on 6/1/2018 an amendment to the protocol for COSMIC-021, the phase 1b trial of cabozantinib (Cabometyx) in combination with atezolizumab (Tecentriq) in patients with locally advanced or metastatic solid tumors to add 10 new expansion cohorts to the trial. The primary objective in the expansion stage of this trial remains to determine the objective response rate in each cohort.

The 10 new expansion cohorts will evaluate the combination of cabozantinib and atezolizumab in patients with:

• non-small cell lung cancer (NSCLC) with an EGFR mutation who have progressed following treatment with an EGFR-targeting tyrosine kinase inhibitor for metastatic disease
• renal cell carcinoma (RCC) with non-clear cell histology who have not had prior systemic anticancer therapy for inoperable, locally advanced, recurrent or metastatic disease
• triple-negative breast cancer who have progressed following treatment with at least one prior systemic therapy for inoperable, locally advanced, recurrent or metastatic disease
• epithelial ovarian cancer who have platinum-resistant or refractory disease
• endometrial cancer who have progressed following treatment with at least one prior systemic therapy for inoperable, locally advanced, recurrent or metastatic disease
• advanced hepatocellular carcinoma (HCC) who have a Child-Pugh score of A and have not had prior systemic anticancer therapy for inoperable, locally advanced, recurrent or metastatic disease
• gastric or gastroesophageal junction adenocarcinoma who have progressed following treatment with platinum-containing or fluoropyrimidine-containing chemotherapy for inoperable locally advanced, recurrent or metastatic disease
• colorectal adenocarcinoma who have progressed following treatment with systemic chemotherapy that contained fluoropyrimidine in combination with oxaliplatin or irinotecan for metastatic disease
• head and neck cancer of squamous cell histology who have progressed following treatment with platinum-containing chemotherapy for inoperable locally advanced, recurrent or metastatic disease
• differentiated thyroid cancer who are radio-refractory or deemed ineligible for treatment with iodine-131

“We look forward to expanding this phase 1b COSMIC-021 clinical trial of cabozantinib in combination with atezolizumab in a number of additional tumor types, which include patient populations in significant need of new therapies that may improve response rates, slow disease progression and improve treatment outcomes,” said Gisela Schwab, M.D., President, Product Development and Medical Affairs and Chief Medical Officer, Exelixis. “We look forward to advancing this trial and to generating data that will inform late stage trials of cabozantinib in combination with immune checkpoint inhibitors.”

The trial had previously been expanded in January of 2018 to include an additional 8 cohorts. These included:

• RCC with clear cell histology who have not had prior systemic anticancer therapy
• urothelial carcinoma (UC) who have progressed on or after platinum-containing chemotherapy
• UC who are ineligible for cisplatin-based chemotherapy and have not received prior systemic chemotherapy for inoperable, locally advanced or metastatic disease
• UC who are eligible for cisplatin-based chemotherapy and have not received prior systemic chemotherapy for inoperable, locally advanced or metastatic disease
• advanced non-squamous NSCLC without a defined tumor genetic alteration (EGFR, ALK, ROS1, or BRAF) who have not received prior therapy with an immune checkpoint inhibitor
• NSCLC without a defined tumor genetic alteration who have progressed following treatment with an immune checkpoint inhibitor
• UC who have progressed following treatment with an immune checkpoint inhibitor
• castration-resistant prostate cancer (CRPC) who have previously received enzalutamide and/or abiraterone acetate and experienced radiographic disease progression in soft tissue

Each expansion cohort of this multicenter phase 1b, open-label study will initially enroll approximately 30 patients. Up to 80 may enroll in the cohorts of patients with UC or NSCLC who have been previously treated with an immune checkpoint inhibitor, with up to a total of 640 patients in the entire study.