One of Merck & Co.’s already marketed drugs has generated positive results in a large clinical trial testing it in patients with a hard-to-treat form of kidney cancer.
Merck on Friday said a pre-planned, interim analysis found its drug Welireg to be significantly better than another kidney cancer therapy, everolimus, on the trial’s main goal of preventing disease progression. The study enrolled around 740 adults with advanced renal cell carcinoma that had progressed after treatment with two specific kinds of target cancer therapy.
The trial had a second main goal: to show Welireg could also keep patients alive longer. On that “overall survival” measure, Merck said there was a “trend toward improvement,” but the results didn’t reach statistical significance. Welireg did, however, succeed on another key test, as the percentage of patients who responded in some way to the drug was deemed statistically significant.
Merck didn’t release any numerical data from the study, but plans to share the results with regulators and present them at an upcoming medical meeting. The company also said overall survival will be assessed further in a subsequent analysis.
As for safety, Welireg’s side effects were “consistent” with what’s been observed in previous studies, according to Merck. The drug’s label currently carries a black box warning for embryo-fetal toxicity. It has additional warnings and precaution’s about monitoring patients for deficiencies in both oxygen and red blood cells. The most common adverse effects seen with Welireg include headache, nausea, fatigue, dizziness, anemia and decreased hemoglobin.
Merck’s trial enrolled patients whose renal cell carcinoma progressed after treatment with drugs that target “PD-1/L1” and “VEGF-TKI,” two proteins involved in the development of certain cancers.
According to Marjorie Green, head of late-stage oncology development at Merck Research Laboratories, these patients need new treatment options that can keep them alive and their disease in check, especially since advanced renal cell carcinoma currently has low survival rates. Some estimates hold that roughly 82,000 new cases of kidney cancer will be diagnosed in the U.S. this year, and around 15,000 people will die from the disease.
“This is the first Phase 3 trial to show positive results in advanced RCC following these therapies and the first new mechanism to demonstrate potential in advanced RCC in recent years,” Green said in a statement.
Welireg works by interfering with the production of a protein known, in short, as HIF-2α. This protein helps regulate how the body responds to changes in oxygen availability; yet, research also indicates that it can play a role in the growth of certain cancers.
Merck got ahold of Welireg through the $1 billion acquisition of Peloton Therapeutics in 2019. Two years after the deal was announced, the Food and Drug Administration approved Welireg for the treatment of adults with von Hippel-Lindau disease, a rare genetic disorder that causes non-cancerous tumors to form throughout the body. Last year, Merck recorded $123 million in Welireg sales.
The FDA’s approval hinged on a small study that showed half of participants who had renal cell carcinoma associated with VHL disease responded to treatment with Welireg. The study also enrolled a few dozen patients with certain kinds of tumors found either in the nervous system or the pancreas, and found the overall response rate in those groups to be 63% and 83%, respectively.
Merck is currently running more than a dozen other studies evaluating Welireg, either alone or paired with other cancer medicines like Keytruda or Lenvima, as a treatment for solid tumors affecting various parts of the body.
Merck, though, isn’t the only drug developer to see potential with this kind of therapy. Arcus Biosciences, a California-based biotechnology company, is now recruiting for an early-stage clinical trial to test its own HIF-2α inhibitor, called AB521, in patients with advanced solid tumors or clear cell renal cell carcinoma.
That study is expected to produce results in early 2026, per a posting on a federal database of clinical trials.