With updated Phase I/Ib data in hand, Arcus will launch a Phase III trial as it aims to compete with Merck, whose drug secured approval for a type of kidney cancer in 2023.
Arcus Biosciences reported updated data on its kidney cancer candidate casdatifan Sunday, providing more evidence that the HIF-2a blocker can challenge Merck’s rival treatment.
The biotech shared updated data from a Phase I/Ib trial at the 2025 American Society of Clinical Oncology (ASCO) Annual Meeting. When abstracts for the conference were released last month, Arcus reported a 41% response rate. By the cut-off for this weekend’s oral presentation, the response rate had increased to 46%. The figure reflects one complete response and 10 partial responses in 24 patients with metastatic kidney cancer.
Arcus generated its Phase I/Ib data in patients who had received and progressed on prior immunotherapy. Patients received casdatifan in combination with Exelixis’ Cabometyx. Patients saw no “meaningful overlapping toxicity” for the two drugs, according to Arcus, and no Grade 4 or 5 adverse events were linked to casdatifan.
Truist Securities analysts said in a note to investors that they “are encouraged by the improved response rate,” which is in line with the 40% to 50% range they were targeting ahead of the release of the ASCO abstract.
The analysts considered the response rate seen in recipients of Merck’s Welireg when setting the target range for casdatifan. Like Arcus’ drug candidate, Welireg is designed to block the action of a protein that is involved in the formation of the new blood vessels that tumors need to grow. Merck won FDA approval for Welireg in advanced renal cell carcinoma, a form of kidney cancer, in 2023.
The biotech is planning a Phase III trial of the combination in kidney cancer patients who have previously received an anti-PD-1/L1 immunotherapy. Arcus has picked progression-free survival (PFS) as its primary endpoint and overall survival as a key secondary endpoint.
Merck reported a response rate of 32% and median PFS of 13.8 months in the comparable cohort of its Welireg-Cabometyx combination study. Arcus is yet to share survival data from its Phase I/Ib trial. The biotech had followed patients for a median of 5.3 months as of the cut-off for the oral presentation.
Gilead passed on an option to license casdatifan earlier this year. Arcus responded by holding a stock offering, which Gilead took part in, to fund development of the cancer candidate. The biotech ended March with $1 billion in various assets to its name, a sum it said will fund operations beyond the initial readout from the planned Phase III trial of casdatifan.
Correction (June 2): This article has been updated from its original version to correct a statement that Arcus was carrying $1.2 billion in debt. It is an accumulated deficit of $1.2 billion, not debt.
