Shares of Exelixis, Inc. EXEL were down 1.08% after the company announced disappointing results from the final analysis of the dual primary endpoint of overall survival (OS) in the subset of patients without active liver metastases (non-liver metastases, NLM) in the late-stage STELLAR-303 study.
The phase III STELLAR-303 study is a global, multicenter, randomized, open-label study evaluating zanzalintinib plus Roche’s RHHBY Tecentriq (atezolizumab) versus regorafenib in previously treated non-microsatellite instability (MSI)-high metastatic colorectal cancer (mCRC).
However, the study showed a non-statistically significant trend in OS favoring the combination in the NLM subpopulation. Median OS was 15.9 months for patients treated with the combination therapy compared with 12.7 months for those receiving regorafenib.
The stock was trading down in after-market trading as well.
Year to date, Exelixis’ shares have risen 17.2% against the industry’s decline of 1.7%.
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EXEL’s STELLAR-303 Study Details
Zanzalintinib is a novel oral kinase inhibitor that inhibits the activity of the TAM kinases (TYRO3, AXL, MeR), MET and VEGF receptors.
Patients were randomized 1:1 to receive either zanzalintinib in combination with atezolizumab (n=451) or regorafenib (n=450) in the STELLAR-303 study.
The study has two co-primary endpoints: overall survival (OS) in the intent-to-treat (ITT) population and OS in the NLM subgroup of patients.
The ITT population includes all randomized patients, irrespective of liver metastasis status. The NLM subgroup comprises patients who were determined by investigators to have no active liver metastases at baseline.
Secondary endpoints include progression-free survival, objective response rate and duration of response in the ITT population and in the NLM subgroup of patients.
The final analysis showed that the safety profile of zanzalintinib in combination with Tecentriq in the NLM subgroup was consistent with that previously reported in the ITT population. No new safety signals were identified.
In June 2025, EXEL announced that STELLAR-303 met its other dual primary endpoint, demonstrating a statistically significant improvement in OS in the ITT population, which included all randomized patients regardless of the presence of active liver metastases.
EXEL’s new drug application seeking approval of zanzalintinib in combination with Tecentriq for the treatment of patients with mCRC is under review in the United States. The targeted population includes patients who were previously treated with fluoropyrimidine-, oxaliplatin- and irinotecan-based chemotherapy, and, if RAS wild-type, an anti-epidermal growth factor receptor therapy.
The agency has set a target action date of Dec. 3, 2026. However, the disappointing results from the final analysis of OS in the NLM subset of patients create uncertainty regarding the drug’s approval.
Roche’s Tecentriq is a cancer immunotherapy that is approved around the world, either alone or in combination with targeted therapies and/or chemotherapies, for various types of cancer.
More on EXEL’s Efforts to Advance Zanzalintinib
EXEL is looking to develop new drugs and reduce dependence on its lead drug, Cabometyx. To that end, zanzalintinib represents the company’s most significant near-term catalyst.
Last month, EXEL announced a clinical development collaboration with pharma giant Merck & Co. MRK to evaluate, in combination with subcutaneous Keytruda Qlex, in the planned phase III STELLAR-316 study for resected stage II/III colorectal cancer (CRC).
Under the agreement, Exelixis will sponsor the STELLAR-316 study, while Merck will provide Keytruda Qlex for use in the study.
MRK’s blockbuster drug Keytruda (pembrolizumab) is approved for several types of cancer.
Exelixis expects to initiate the STELLAR-316 study in mid-2026.
The late-stage STELLAR-316 will evaluate zanzalintinib with and without Keytruda Qlex in patients with resected stage II/III CRC who, following definitive therapy, have tested positive for molecular residual disease (MRD+) and have no radiographic evidence of disease.
Earlier this year, Exelixis partnered with Natera NTRA, a global leader in cell-free DNA and precision medicine, for this study.
Natera will supply its Signatera assay to identify eligible MRD-positive patients for enrollment, further integrating precision medicine into the program.
We note that Exelixis had collaborated with MRK in October 2024 to advance zanzalintinib.
In April 2026, MRK initiated LITESPARK-034, a phase III study evaluating zanzalintinib plus Welireg (belzutifan) versus Welireg and placebo in previously treated advanced renal cell carcinoma (RCC) patients who progressed after PD-1/L1 and VEGFR-TKI therapies.
This marks the second Merck-sponsored phase III study under the collaboration, following LITESPARK-033 (launched in December 2025), which is assessing the combination against cabozantinib in first-line advanced RCC post-adjuvant immunotherapy.
Exelixis also announced two additional studies of zanzalintinib — STELLAR-202, a planned phase II trial evaluating the drug in combination with Keytruda as maintenance therapy in squamous non-small cell lung cancer, and a new expansion cohort in the ongoing phase Ib/II STELLAR-002 study assessing zanzalintinib plus docetaxel in metastatic castration-resistant prostate cancer patients with measurable disease.
EXEL’s Zacks Rank
Exelixis currently has a Zacks Rank #3 (Hold). You can see the complete list of today’s Zacks #1 Rank (Strong Buy) stocks here.
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