The news comes on the heels of promising Phase I/Ib data, which point to the potential of casdatifan as a more effective alternative to Merck’s Welireg in renal cell carcinoma.
Gilead will not move forward with Arcus Biosciences’ casdatifan, an investigational HIF-2a blocker that is being tested for kidney cancer.
As per the California biotech’s Tuesday press announcement, Gilead’s window to exercise its exclusive option to obtain rights to casdatifan has “expired.” Arcus will retain full control over the asset and its development path forward. Arcus also announced that it will run a $150 million common stock offering—which Gilead will participate in—to help bankroll future studies of casdatifan.
Arcus CEO Terry Rosen in a statement said that the biotech is “thrilled” to keep ownership of casdatifan, which he says “represents a transformational change for Arcus” and allows it to “address a significant unmet need for patients with an estimated $5 billion market opportunity.”
Investors, however, are not as enthused: Arcus’ shares dipped 16% to $10.96 on Tuesday, a new 52-week low for the company, per SeekingAlpha.
Analysts at Mizuho Securities, on the other hand, appeared optimistic about Arcus, writing in a Tuesday note that the stock offering “could allow [Arcus] to advance the casdatifan program independently” and provide freedom to assess the candidate as a monotherapy or as part of combination regimens.
Tuesday’s news comes just days after Arcus presented promising Phase I/Ib data for casdatifan at the 2025 American Society of Clinical Oncology Genitourinary Cancers Symposium. Results, disclosed over the weekend, showed that a 100-mg dose, given once a day, resulted in a 33% confirmed overall response rate (ORR) and a 52% stable disease rate in patients with metastatic clear cell renal cell carcinoma (RCC).
Patients treated with this casdatifan dosage did not reach median progression-free survival (PFS) at the time of the readout, though a different dose level—50 mg twice-daily—had a median PFS of 9.7 months. Arcus is taking the 100-mg dose forward.
According to Mizuho, these data suggest that casdatifan is “superior” to Merck’s Welireg (belzutifan), which is also a HIF-2a inhibitor that is FDA-approved for advanced RCC. In particular, the analysts zeroed in on casdatifan’s 9.7-month PFS in the 50-mg, once-daily dose arm, which they say compares favorably to Welireg’s 5.6-month PFS, as indicated in its label.
Additionally, casdatifan’s 33% ORR is higher than Welireg’s 22%, as per Mizuho. Cross-study comparisons are inconclusive, however, in the absence of direct head-to-head trials.
Arcus plans to ramp up investment to “position casdatifan as the HIF-2a inhibitor of choice,” Rosen said in a statement. The biotech will unveil more data for the therapy throughout 2025 and is preparing to launch another study, dubbed PEAK-1, which will test casdatifan with Cabometyx, Exelixis’s VEGF2 inhibitor, in metastatic clear cell RCC patients who had previously undergone immune-oncology treatments.
