Arcus Biosciences disclosed updated data from its ARC-20 study showing that casdatifan combined with cabozantinib produced a median progression-free survival of 14.5 months in patients with second-line clear cell renal cell carcinoma (ccRCC). The figures were reported in an 8-K filing with the U.S. Securities and Exchange Commission using a September 4, 2026 data cutoff.
The result comes from 43 patients with a median follow-up of 21.3 months. The filing also presented data from first-line and late-line cohorts, though each cohort carries its own follow-up length and patient population, making cross-cohort comparisons indirect. No comparison against an active control arm was reported.
Key finding
In 43 second-line ccRCC patients with 21.3 months of median follow-up, casdatifan plus cabozantinib yielded a median PFS of 14.5 months and a confirmed response rate of 44%, though the study included no randomized control arm against which to benchmark these figures.
Study Design
| Trial | ARC-20 |
|---|---|
| Population | Patients with clear cell renal cell carcinoma across second-line, first-line (TKI-free), and late-line settings; reported in separate cohorts |
| Treatment | Casdatifan plus cabozantinib (second-line cohort); casdatifan plus zimberelimab (first-line cohort); casdatifan plus zimberelimab plus ipilimumab (triple combination cohort); casdatifan monotherapy (late-line pooled cohorts) |
| Key secondary endpoints | Confirmed objective response rate, primary progression rate, overall survival (18-month OS reported for second-line cohort; median OS reported for late-line cohort) |
The primary endpoint was not explicitly specified in the 8-K filing as reported in the source material. Data were filed with the SEC by Arcus Biosciences CEO Terry Rosen using a September 4, 2026 cutoff date. Each cohort enrolled a separate group of patients and carries a distinct median follow-up duration, so results across cohorts are not directly comparable.
Results and Safety
In the second-line cabozantinib cohort (43 patients, 21.3 months median follow-up), median PFS was 14.5 months, the confirmed objective response rate was 44%, primary progression (defined as progression at or before the first scan) occurred in 5% of patients, and 18-month overall survival was 77%. The filing stated that efficacy was similar regardless of prior TKI exposure.
In the first-line TKI-free cohort, casdatifan plus zimberelimab (30 patients, 11.5 months median follow-up) produced PFS rates of 86% at six months and 69% at 12 months, with a confirmed response rate of 50% and primary progression in 6.7% of patients. The triple combination of casdatifan, zimberelimab, and ipilimumab had only three months of median follow-up among 31 dosed patients; among the 24 who had reached a first scan, primary progression occurred in one patient (4%). The filing characterized this dataset as early. In four pooled late-line cohorts totaling 121 patients (28 months median follow-up), casdatifan monotherapy yielded a median OS of 35 months, median PFS of 13 months, and a confirmed response rate of 36%, with results described as consistent across one, two, or three prior TKI-containing regimens.
No unexpected safety signals were identified in any cohort. Serious immune-related adverse events in the triple combination arm were described as generally consistent with the known profile of ipilimumab plus nivolumab in frequency, severity, and timing. Detailed safety tabulations were not included in the filing as reported in the source material.
Clinical Context
The second-line setting is a recognized area of unmet need in ccRCC, particularly for patients who have already received a TKI-based regimen. According to the filing, approximately 60% of second-line patients in current practice are TKI-pretreated and derive diminished benefit from subsequent TKI therapy. Casdatifan is a hypoxia-inducible factor 2-alpha (HIF-2α) inhibitor, a mechanistic class that has drawn interest for its activity in this population. The filing noted that efficacy in the cabozantinib cohort appeared similar whether or not patients had prior TKI exposure.
Important limitations remain. The ARC-20 cohorts are single-arm, and no randomized comparisons against standard-of-care regimens were reported. Follow-up is still maturing in the first-line and triple combination cohorts, and the triple combination dataset in particular is too early to draw meaningful efficacy conclusions. Further prospective data will be needed to establish where casdatifan-based combinations fit within the evolving ccRCC treatment landscape.
Sources
- Arcus Biosciences, Inc. “Form 8-K: Updated ARC-20 Study Data.” SEC Filing. September 2026. View source
- Bullished. “Arcus Kidney Cancer Drug Casdatifan Hits 14.5-Month Median PFS with Cabozantinib in Second-Line ccRCC.” News article. 2026. View source
