Exelixis Ends Phase III Trial Early Due to ‘Dramatic’ Benefits in Neuroendocrine Tumors

Pictured: Exelixis headquarters/Company courtesy

Pictured: Exelixis headquarters/Company courtesy

Exelixis on Thursday announced it was unblinding and stopping the pivotal Phase III CABINET trial ahead of schedule, following “dramatic improvement in efficacy” in patients treated with its tyrosine kinase inhibitor Cabometyx (cabozantinib).

The decision to stop the trial early is in line with the recommendation of the Independent Data and Safety Monitoring Board of the Alliance for Clinical Trials in Oncology, which found that Cabometyx treatment led to a significantly longer time without disease progression or death in patients with advanced pancreatic and extra-pancreatic neuroendocrine tumors (NET).

There is currently no standard of care for patients with these tumors who progress after initial treatment, according to Will Berg, Exelixis’ senior vice president for medical affairs. With its strong performance in CABINET, Cabometyx’s could potentially provide these patients with a new treatment option. The company will discuss the study’s findings with the FDA, Berg said.

CABINET is a randomized, double-blinded and placebo-controlled study that enrolled 290 patients, of whom 93 had pancreatic NET and 197 had extra-pancreatic NET. The study’s primary endpoint was progression-free survival (PFS), while key secondary efficacy endpoints included overall survival and radiographic response rate.

In terms of safety, CABINET did not detect any new signals of concern and Cabometyx’s adverse event profile was consistent with what had been established in prior studies.

Cabometyx is a tyrosine kinase inhibitor that works by blocking the MET, AXL and VEGF proteins, all key drivers of tumorigenesis, according to Exelixis’ website. In turn, Cabometyx interferes with crucial cancer functions—such as metastasis and the formation of new blood vessels in the tumor’s environment—while also making cancer cells more sensitive to the immune response.

On Monday, this mechanism of action notched Cabometyx a late-stage victory in metastatic castration-resistant prostate cancer when used in combination with Roche’s PD-1/PD-L1 blocker Tecentriq (atezolizumab). In the Phase III CONTACT-02 study, the combination regimen led to a significant improvement in PFS, though only a trend toward better overall survival was reported.

Roche and Exelixis are trialing the Tecentriq-Cabometyx combo in several cancer indications and have sustained two Phase III defeats so far: in non-small cell lung cancer in December 2022 and in renal cell carcinoma in March 2023.

Cabometyx won its first FDA approval in April 2016 for advanced renal cell carcinoma and it has since picked up indications in hepatocellular carcinoma and thyroid cancer.

Tristan Manalac is an independent science writer based in Metro Manila, Philippines. He can be reached at tristan@tristanmanalac.com or tristan.manalac@biospace.com.

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