Exelixis (EXEL) Reports Results from Phase 2 Trial of Cabozantinib in Combination with Pembrolizumab

Exelixis, Inc. (Nasdaq: EXEL) today announced results from a phase 2, investigator-sponsored trial of cabozantinib (CABOMETYX®) in combination with pembrolizumab in patients with recurrent or metastatic head and neck squamous cell carcinoma (HNSCC). The data will be presented at the 2022 American Society of Clinical Oncology (ASCO) Annual Meeting during Oral Abstract Session: Head and Neck Cancer on Friday, June 3 beginning at 2:45 p.m. CT.

The trial met its primary endpoint of objective response rate per Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1 at 54%. The overall clinical benefit rate was 91%. At a median follow-up of 10.6 months, the one-year progression-free survival rate was 54.0% (95% confidence interval [CI]: 31.5-72.0%), and median progression-free survival was 14.6 months. The one-year overall survival (OS) rate was 68.4% (95% CI: 45.1-83.5%; median OS: 22.3 months). For the 17 patients with a PD-L1 combined positive score (CPS) under 20, the one-year OS rate was 54.9% (95% CI: 24.5-77.5%; median OS: 14.6 months). For the 17 patients with a CPS score of 20 or more, the one-year OS rate was 83.6% (95% CI: 48.0-95.7%; median OS: 32.9 months).

“Metastatic head and neck cancer is a challenging disease to treat, particularly following disease progression after definitive therapy, meaning patients need additional options beyond radiation and chemotherapy,” said Nabil F. Saba, M.D., Professor and Vice Chair, Hematology and Medical Oncology, The Lynne and Howard Halpern Chair in Head and Neck Cancer Research, Co-Director of Head and Neck Cancer Multidisciplinary Program, Winship Cancer Institute, Emory University, and primary investigator of the investigator-sponsored trial. “These results showing promising clinical activity of cabozantinib in combination with pembrolizumab are encouraging to these patients who face poor outcomes.”

In this phase 2 trial, eligible patients had recurrent or metastatic HNSCC that was deemed inoperable, with measurable disease per RECIST version 1.1, a life expectancy of at least 3 months and an Eastern Cooperative Group Performance Status of 0 or 1. Of the 36 evaluable patients, 61% had cancer in the oropharynx, 16% in the nasopharynx, 11% in the larynx, 6% in the hypopharynx and 6% in the oral cavity. Eighty-nine percent of patients had received prior radiation therapy and all had received prior chemotherapy.

The most frequent adverse events (AEs) were fatigue (44.4%), diarrhea (33.3%), hypothyroidism (33.3%), constipation (30.6%), dry mouth (27.8%), anorexia (25.0%), headache (25.0%), hypertension (25.0%), hyponatremia (25.0%) and oral mucositis (25.0%). Grade 3/4 treatment-related AEs were aspartate aminotransferase (AST) increase (8.3%), hyponatremia (8.3%), gamma-glutamyl transferase increase (5.6%), lipase increase (5.6%), oral mucositis (5.6%), alanine transaminase/AST increase (2.8%), bilirubin increase (2.8%) and hypertension (2.8%). Dose reductions occurred in 47.2% of patients, and AEs leading to discontinuation occurred in 25.0% of patients.

“Treatment options for patients with metastatic head and neck squamous cell carcinoma are limited, leaving a critical unmet need for this community,” said Vicki L. Goodman, M.D., Executive Vice President, Product Development & Medical Affairs, and Chief Medical Officer, Exelixis. “These data support the further development of a combination regimen of cabozantinib and an immune checkpoint inhibitor in patients with metastatic head and neck carcinoma and we are pleased to share these data at ASCO. Through our research, including our investigator-sponsored trials program, we continue to advance toward our goal of bringing new treatment options to people with difficult-to-treat cancers.”

About HNSCC

HNSCC comprises head and neck cancers that begin in the squamous cells that line the mucosal surfaces of the head and neck.1 Accounting for about 90% of all head and neck cancers, HNSCC is classified by its location: it can occur in the oral cavity, oropharynx, nasal cavity and paranasal sinuses, nasopharynx, larynx or hypopharynx.1,2 Oral cavity and larynx cancers are generally associated with tobacco consumption, alcohol abuse or both, whereas pharynx cancers are increasingly attributed to infection with human papillomavirus (HPV), primarily HPV-16.3 About 50,000 new cases of HNSCC are diagnosed in the U.S. every year.1 HNSCC is more common among men and people over the age of 50.4 Depending on the site of the cancer and level of metastases, the five-year survival rate for metastatic HNSCC ranges from 4-35%.5

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