A large number of patient dropouts caused by immune side effects have forced Merck to end a late-stage trial of its anti-TIGIT drug vibostolimab in skin cancer.
Because of the dropouts, Merck unblinded the 1,594-person study and said it was unlikely it would hit statistical significance. The Phase 3 trial was studying the efficacy of vibostolimab plus Keytruda versus Keytruda alone, in patients with resected, high-risk stage IIB-IV melanoma.
Merck’s press release announcing the trial discontinuation didn’t say how many patients dropped out or how severe the side effects were. The company didn’t immediately respond to a request for comment on Monday.
The study, dubbed KeyVibe-010, has a primary endpoint of recurrence-free survival. The company is recommending patients receiving the combination regimen be offered the choice to switch to Keytruda monotherapy. It is also continuing with data analysis.
Other Phase 3 tests of vibostolimab plus Keytruda are ongoing in various lung cancer settings. Merck said it doesn’t expect changes to those trials based on the findings from KeyVibe-010.
“These studies in lung cancer are routinely monitored, and interim external data monitoring committee safety reviews have not resulted in any safety-related study modifications to date,” a company spokesperson told Endpoints News in a statement.
“If vibostolimab added activity despite being difficult to tolerate, it may yet have a (slim) chance to succeed in metastatic lung cancer,” TD Cowen analysts said.
This is not the first time that vibostolimab plus Keytruda has disappointed in clinical trials. In March 2023, the regimen failed the open-label part of a Phase 2 test comparing it with chemotherapy in patients with metastatic non-small cell lung cancer.
Editor’s note: This article was updated to add company and analyst comment.