The summary of Exelixis' Phase 3 STELLAR-303 trial results for metastatic colorectal cancer requires an important update due to mixed investor reactions despite some positive data points.

The trial showed that the combination of zanzalintinib and atezolizumab improved median overall survival (OS) to 10.9 months compared to 9.4 months with regorafenib, representing a 20% reduction in the risk of death. This OS benefit was consistent across key subgroups including geographic region, RAS mutation status, liver metastases presence, and prior anti-VEGF therapy. Landmark OS at 12 and 24 months was also higher with the combination.?

However, the progression-free survival (PFS) benefit was more modest and did not reach statistical superiority at interim analysis due to hierarchical testing constraints. The PFS trend was consistent but investors likely expected stronger or clearer efficacy signals in this endpoint, fueling the 12% stock price drop observed right after the data release.

In summary, while the trial met one of its dual primary endpoints and demonstrated a meaningful survival advantage, the mixed nature of the PFS results has caused disappointment in the market, dampening enthusiasm. The company plans to submit a new drug application for zanzalintinib by year-end, supporting medium-term growth prospects but possibly with tempered near-term expectations priced in by investors.?

The rest of the pipeline remains robust with additional Phase 2/3 drugs progressing, and the CABINET trial reaffirmed CABOMETYX's benefit in neuroendocrine tumors, supporting longer-term growth beyond the colorectal cancer indication.?

Therefore, while the initial summary noted positive impacts from the phase 3 data, it should highlight the nuanced investor response and the modest PFS results that tempered the stock price, reflecting cautious optimism about growth baked into these latest trial disclosures.