Kidney cancer is one of the most common cancers affecting adults, and the most common form is called clear cell renal cell carcinoma, often shortened to ccRCC.
Although treatments for this disease have improved greatly over the past decade, many patients with advanced kidney cancer eventually face a difficult problem: their cancer stops responding to treatment. Once resistance develops, treatment options become more limited, making it harder to control the disease.
Researchers around the world are searching for new ways to help patients whose cancer has progressed despite receiving standard therapies. Now, an early clinical trial led by Mayo Clinic researchers has produced encouraging results that may offer new hope for people with advanced kidney cancer.
The study focused on a new experimental drug called darlifarnib. Researchers tested it in combination with cabozantinib, a targeted therapy that is already widely used to treat advanced clear cell renal cell carcinoma.
Cabozantinib works by blocking signals that cancer cells use to grow and spread. While the drug can be very effective, its benefits are often temporary because tumors can adapt and find alternative pathways to continue growing.
To address this challenge, scientists investigated whether adding darlifarnib could help overcome treatment resistance.
Darlifarnib is a next-generation targeted therapy designed to block additional growth signals used by cancer cells. Researchers hoped that attacking multiple pathways at the same time might slow or stop tumor growth more effectively than cabozantinib alone.
The findings came from a phase 1a/b clinical trial, which represents one of the earliest stages of testing a new treatment in humans. Early-phase trials are primarily designed to evaluate safety and determine appropriate dosing, but they can also provide important clues about whether a treatment might be effective.
The study included 18 patients with advanced clear cell renal cell carcinoma. All of them had previously been treated with cabozantinib, and many had received several other cancer treatments as well.
In fact, about half of the participants had already undergone at least three previous therapies before joining the trial. This means the study involved patients whose disease had become particularly difficult to treat.
Despite these challenges, the results were encouraging. Among 16 patients who could be fully evaluated, seven experienced tumor shrinkage.
This translated to an overall response rate of 44%. Even more impressive, disease control was achieved in 15 of the 16 patients, or 94% of participants. Disease control means that the cancer either shrank or stopped growing for a period of time.
According to Dr. Yousef Zakharia, a medical oncologist at Mayo Clinic in Arizona and the principal investigator of the study, these findings are especially important because many patients with advanced kidney cancer urgently need better treatment options. He presented the results at the 2026 International Kidney Cancer Symposium: Europe, held in Paris.
Researchers believe the combination may work by preventing cancer cells from switching to alternative growth pathways after becoming resistant to cabozantinib. Cancer cells are often remarkably adaptable.
When one pathway is blocked, they can activate others to survive. By targeting multiple pathways simultaneously, the new combination may make it harder for tumors to escape treatment.
Although the results are promising, the researchers emphasize that this is still an early-stage study involving a relatively small number of patients.
Larger clinical trials are needed to confirm whether the benefits observed in this trial can be reproduced in a broader patient population. Such studies will also help researchers better understand the long-term safety and effectiveness of the treatment.
The international, multicenter trial is continuing and will enroll more participants to further evaluate the drug combination. If future studies confirm these early findings, the treatment could potentially become a valuable new option for patients whose kidney cancer has stopped responding to standard therapies.
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Source: Mayo Clinic.
