Exelixis reports STELLAR-303 final analysis, FDA review underway
Exelixis Inc. reported final overall survival results from the Phase 3 STELLAR-303 trial, indicating a numerical but non-statistically significant survival benefit for the zanzalintinib and atezolizumab combination in patients without active liver metastases. The FDA accepted a New Drug Application for the therapy in February 2026 with a target action date of December 3, 2026, while analysts highlighted the company's defensive investment profile.
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Exelixis Inc. on Monday reported final overall survival data from the Phase 3 STELLAR-303 trial, showing a numerical survival benefit that failed to achieve statistical significance in a subgroup of metastatic colorectal cancer patients without active liver metastases. The trial evaluated zanzalintinib in combination with atezolizumab versus regorafenib in previously treated non-microsatellite instability-high metastatic colorectal cancer. The FDA is currently reviewing a New Drug Application for the combination therapy, with a target action date of December 3, 2026.
The final analysis of the dual primary endpoint of overall survival in the subset of patients without active liver metastases showed a non-statistically significant trend favoring the combination. The stratified hazard ratio was 0.83 with a P-value of 0.1185. Median overall survival was 15.9 months with the zanzalintinib combination compared to 12.7 months with regorafenib.
Safety Profile and Previous Results
The safety profile of zanzalintinib in combination with atezolizumab in this subgroup was consistent with the intention-to-treat population, with no new safety signals identified. Exelixis previously announced that STELLAR-303 met its other dual primary endpoint, demonstrating a statistically significant improvement in overall survival in the intention-to-treat population, which included all randomized patients regardless of liver metastases status.
Regulatory Status and Analyst View
In February 2026, the FDA accepted the New Drug Application seeking approval of zanzalintinib in combination with atezolizumab for previously treated metastatic colorectal cancer patients who had received specific chemotherapies and, when appropriate, anti-EGFR therapy. William Blair analyst Andy Hsieh noted that given the trial's statistical design, it could be deemed successful if one of two dual primary endpoints met statistical significance. Hsieh added that Exelixis provides investors with a highly defensive investment profile due to substantial cash flow generation into early 2031.
| Metric | Zanzalintinib + Atezolizumab | Regorafenib |
|---|---|---|
| Median OS (months) | 15.9 | 12.7 |
| Stratified Hazard Ratio | 0.83 | — |
| P-value | 0.1185 | — |
How might the lack of statistical significance in the non-active liver metastases subgroup influence the FDA's risk-benefit assessment by the December 2026 target date?
Will Exelixis need to conduct additional post-marketing studies to further validate the survival benefit in specific patient subpopulations?
What impact will these mixed trial results have on the commercial uptake and prescribing patterns of zanzalintinib if approved?
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