An experimental cancer treatment using genetically engineered immune cells has produced encouraging results in patients with advanced melanoma who had exhausted important treatment options. In a new clinical study, tumors shrank in 10 of 15 patients who received the selected treatment dose, including two whose cancer disappeared on imaging tests.
The findings, published November 3, 2026, in Nature Medicine, describe a personalized treatment designed to strengthen the body's own cancer-fighting immune cells. The approach could offer another option for people whose melanoma has continued growing despite earlier immunotherapy.
The experimental treatment, called amsokigene autoleucel or amsoki-cel, uses immune cells collected from a patient's own tumor. Scientists genetically modify these cells to help them survive and attack cancer while reducing the need for a powerful immune-stimulating drug commonly used with similar treatments.
How the New Treatment Works
The therapy belongs to a category known as tumor-infiltrating lymphocyte treatment, or TIL therapy. Lymphocytes are immune cells that can recognize and destroy abnormal cells, including some cancer cells.
Doctors begin by collecting tissue from a patient's tumor. Laboratory specialists then isolate immune cells that have entered the tumor and grow large numbers of them before returning the cells to the patient.
The new treatment adds another step. Researchers genetically engineer the collected cells to produce a protein called interleukin-15, or IL-15, which helps support immune-cell survival and activity.
Unlike conventional approaches, the engineered cells do not continuously produce the active protein at the same level. Instead, IL-15 expression is controlled by a medication called acetazolamide, allowing doctors to influence the activity of the modified cells after infusion.
Acetazolamide is an established medication used for several medical conditions, including glaucoma and altitude sickness. Its new role in this treatment is to activate a specially engineered control mechanism within the immune cells.
Researchers hope this system will help cancer-fighting cells remain active long enough to attack tumors without causing excessive inflammation throughout the body.
Two-Thirds of Patients Responded at the Selected Dose
The research combined information from two early-stage clinical trials involving 37 patients with advanced melanoma. All had experienced disease progression following treatment with immune checkpoint inhibitors, drugs that help the immune system recognize and attack cancer.
The first trial included 17 patients, while the second, called Agni-01, included 20. The researchers examined safety across both studies and assessed tumor responses in patients receiving different treatment doses.
Among 15 patients treated at the dose selected for further testing, 10 experienced an objective response, meaning their tumors shrank enough to meet established clinical criteria. This represented a response rate of 66.7 percent.
Two patients experienced complete responses, meaning no detectable cancer remained on their imaging assessments. A complete response does not necessarily mean a patient is permanently cured, because microscopic cancer cells may remain.
The median progression-free survival in this group was 8.1 months. This measurement describes the time patients lived without their cancer worsening, rather than their overall survival.
The results are notable because these patients had cancers that resisted earlier immune checkpoint treatment. Such patients often have fewer effective treatment options once their disease progresses.
However, the study was small and did not include a randomized comparison group. Larger trials are necessary to establish whether the treatment provides better or longer-lasting results than existing therapies.
Reducing the Need for a Difficult Cancer Treatment
One of the most important features of amsoki-cel is its ability to eliminate the need for high-dose interleukin-2, or IL-2, after the engineered cells are infused.
Traditional TIL therapy often requires IL-2 to stimulate the transferred immune cells. Although effective in supporting immune activity, high doses can cause serious complications involving blood pressure, fluid balance and organ function.
The new approach uses engineered IL-15 controlled by acetazolamide instead. This could make treatment easier to tolerate while still encouraging the immune cells to multiply and remain active.
Patients must still receive chemotherapy before their immune-cell infusion. This preparation temporarily reduces existing immune cells, creating conditions that allow the transferred cells to expand.
The investigators also tested a less intensive chemotherapy preparation regimen. Reducing the amount of preparatory treatment could eventually lessen some of the physical burden associated with cellular immunotherapy.
Safety Findings Show Both Progress and Remaining Risks
Across the 37 treated patients, researchers reported no treatment-related deaths, intensive care admissions or dose-limiting toxicities in the pooled analysis. However, significant blood-related side effects were common.
Nearly 65 percent of patients experienced severe neutropenia, a condition involving dangerously low levels of certain infection-fighting white blood cells. Severe reductions in other blood cells were also reported.
An important safety concern emerged during the first trial. The initial patient experienced rapid expansion of the engineered immune cells and swelling around a previously irradiated brain metastasis.
Researchers responded by changing the treatment protocol and substantially reducing the initial doses of the engineered cells and controlling medication. Later adjustments allowed investigators to evaluate different doses under revised safety precautions.
The study therefore provides early evidence of tolerability, not proof that the treatment is free from serious risks. Patients receiving cellular immunotherapy still require careful medical monitoring.
A New Direction in Personalized Cancer Therapy
Melanoma is a form of skin cancer that develops in pigment-producing cells called melanocytes. Although many cases can be successfully treated when detected early, advanced melanoma can spread to lymph nodes and organs throughout the body.
Immune checkpoint inhibitors have transformed treatment for many patients with advanced disease. These medications block signals that cancers use to prevent immune cells from attacking them.
Nevertheless, some cancers never respond to checkpoint inhibitors, while others initially improve before becoming resistant. Finding treatments for these patients remains a major priority in melanoma research.
The broader field of TIL therapy has already reached an important milestone. In February 2024, the U.S. Food and Drug Administration granted accelerated approval to lifileucel, marketed as Amtagvi, for certain patients with advanced melanoma.
That treatment also uses immune cells collected from a patient's tumor but requires high-dose IL-2 support after infusion. Amsoki-cel is being developed as a genetically engineered alternative that could potentially avoid that requirement.
Researchers also observed biological evidence that the experimental treatment was acting as intended. Following infusion, several populations of cancer-fighting immune cells expanded, including natural killer cells, which help the body recognize abnormal cells.
In some patients, blood tests showed declining amounts of circulating tumor DNA soon after treatment. These findings suggest that the infused cells were affecting cancer activity, although the biological analyses were exploratory.
What Happens Next?
The research was conducted with support from Obsidian Therapeutics, the biotechnology company developing amsoki-cel. The company funded the trials and participated in their design and analysis.
A larger registration-enabling group within the Agni-01 trial is now enrolling patients with advanced melanoma that has progressed after checkpoint inhibitor treatment. Investigators will assess tumor responses using independent imaging review to provide stronger evidence of clinical effectiveness.
The company has also begun investigating the engineered-cell approach in non-small cell lung cancer. That research is at an earlier stage and cannot yet establish whether the treatment works against other types of solid tumors.
The newly published melanoma findings are encouraging because they demonstrate measurable tumor shrinkage in a difficult-to-treat population. Yet the small number of patients, limited follow-up and absence of a randomized comparison mean the results must be interpreted cautiously.
The next major test will be whether researchers can reproduce the responses in a larger group while maintaining an acceptable safety profile. Those findings will help determine whether engineered immune cells controlled by an existing medication can become another established treatment for advanced melanoma.