Most people with colorectal cancer respond well to the first treatments they receive, such as chemotherapy and targeted drugs. But when the cancer spreads and stops responding, treatment options become limited—especially for microsatellite-stable (MSS) colorectal cancer, which is the most common type.
Zanzalintinib is a new medication designed to help patients in this exact situation. Early research suggests it may control the cancer longer and with fewer side effects than some older medicines. For many families, it represents a new source of hope.
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What Is Zanzalintinib?
Zanzalintinib is a pill taken by mouth. It is a type of targeted therapy, which means it blocks specific signals that cancer cells use to grow and spread.
Cancer needs blood vessels to survive, and zanzalintinib blocks important pathways that tumors use to create new blood supply. It also shuts down signals that help cancer cells move, invade other organs, and resist treatment. Because it acts on several pathways at once, it may be more effective than older drugs in its class.
How Does Zanzalintinib Work?
Zanzalintinib targets proteins called VEGFR2, MET, AXL, and others. These proteins help cancer cells grow, spread, and protect themselves from treatment. When zanzalintinib blocks these signals, cancer cells weaken and may stop growing.
This approach makes zanzalintinib different from chemotherapy: instead of killing fast-growing cells broadly, it aims at the specific processes cancer cells depend on.
What Did the STELLAR-303 Study Find?
The STELLAR-303 clinical trial compared zanzalintinib with regorafenib, a drug commonly used when standard treatments stop working. Patients on the study had metastatic colorectal cancer that no longer responded to chemotherapy or other targeted medicines.
The study showed that:
- Patients lived longer on zanzalintinib than on regorafenib.
- Cancer stayed under control for a longer period.
- Fewer patients needed to stop treatment because of side effects.
These findings are especially meaningful because treatment options after second- or third-line therapy are usually limited.
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What Side Effects Should Patients Expect?
All cancer treatments can cause side effects, and zanzalintinib is no exception. The most common side effects reported in studies included:
- tiredness
- diarrhea
- high blood pressure
- decreased appetite
- hand-foot skin reactions (soreness or redness on palms and soles)
Most side effects were manageable and less severe than those seen with older medicines like regorafenib. Doctors may give instructions on how to manage symptoms at home, reduce the dose, or take short breaks from treatment when necessary.
Who Could Benefit from Zanzalintinib?
Zanzalintinib is being studied for people with microsatellite-stable metastatic colorectal cancer who have already received standard treatments. This group has few effective options, which is why the results of the STELLAR-303 trial are so important.
It may also be useful in other cancers where the same growth pathways are active, but research is ongoing.
Is Zanzalintinib Available Yet?
Zanzalintinib is still being studied and is not yet fully approved for colorectal cancer. However, its strong trial results suggest it may become available in the near future. Many cancer centers are also participating in additional trials, giving some patients access to the medication sooner.
Patients can ask their oncologist whether clinical trials involving zanzalintinib are available in their region.
What Does the Future Look Like?
Researchers are now studying zanzalintinib in combination with immunotherapy. Some laboratory studies suggest that by blocking MET and AXL, the medicine might help the immune system recognize cancer more easily. If this proves true, zanzalintinib could become part of combination treatments that work even better than the drug alone.
Because its side effects appear manageable and its early results are encouraging, many experts believe zanzalintinib may become a key part of metastatic colorectal cancer care in the years ahead.
Conclusion
Zanzalintinib is a promising new treatment for people with metastatic colorectal cancer, especially those with microsatellite-stable disease who have already received several lines of therapy. It works by blocking multiple pathways that cancer cells use to grow and spread. Early clinical trial results show longer survival, better cancer control, and fewer severe side effects than older drugs in its class.
Although still under investigation, zanzalintinib represents progress in an area of cancer care where new options are urgently needed. Patients and families should talk to their oncologist about whether clinical trials involving zanzalintinib may be appropriate.
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Written by Armen Gevorgyan, MD