Exelixis (Exelixis (EXEL)) released final overall survival data Monday from its Phase 3 STELLAR-303 trial, and while the numbers didn't hit statistical significance, they tell an interesting story about a potential new treatment for a tough cancer.

The trial tested zanzalintinib — a next-generation oral tyrosine kinase inhibitor that's essentially the successor to Exelixis' flagship drug cabozantinib — in combination with atezolizumab. The target: patients with metastatic colorectal cancer (mCRC) who don't have active liver metastases and have already been through other treatments.

Here's what the data showed: Patients getting the zanzalintinib combo lived a median of 15.9 months, compared to 12.7 months for those on regorafenib, an existing therapy. That's a 3.2-month improvement, but the hazard ratio of 0.83 came with a p-value of 0.1185 — meaning it didn't reach the statistical significance threshold. Still, the trend is there.

William Blair analyst Andy Hsieh noted that the trial's design allows it to be considered successful if just one of two dual primary endpoints hits significance. So this isn't necessarily a failure.

But Hsieh's main point was broader: "Given its substantial and likely durable cash flow generation into early 2031, we continue to believe Exelixis provides investors with a highly defensive investment profile." In other words, even if the drug doesn't become a blockbuster overnight, the company's financial foundation is solid.

Exelixis isn't waiting around. The FDA accepted its New Drug Application for zanzalintinib plus atezolizumab back in February 2026, and the agency set a PDUFA target action date of December 3, 2026. That's the day we'll know whether the combo gets the green light for previously treated mCRC patients.

As for the stock, Exelixis shares dipped 0.89% to $51.45 on Monday — a modest move that suggests investors are taking the mixed data in stride.