Two Immune Cell Armies in One Infusion: Combination NK and T Cell Therapy Shows Promise in Hard-to-Treat Tumors

For patients whose solid tumors have returned or continued to grow after surgery, chemotherapy, and radiation, the therapeutic landscape can feel starkly empty. A newly published phase 1 clinical trial offers a cautiously encouraging signal from this difficult frontier. Researchers report that an experimental cellular immunotherapy called SDH-Combi, which combines two of the body’s own cancer-fighting cell types—natural killer cells and tumor-primed T lymphocytes—was well tolerated in nine patients with recurrent or progressive solid tumors, and produced early hints of disease stabilization and improved quality of life. The study, published open access in Cancer Immunology, Immunotherapy, is small and uncontrolled, but its safety profile and feasibility data provide the foundation that larger trials will need.

The biological logic behind the combination is what sets it apart from many single-cell approaches. Solid tumors are not uniform targets; they are heterogeneous collections of malignant cells that deploy overlapping but distinct strategies to evade immune attack. Natural killer cells belong to the innate immune system and can recognize and destroy stressed or abnormal cells without needing to identify a specific tumor antigen, making them valuable against cancer cells that have downregulated the surface molecules T cells typically rely on. T lymphocytes, by contrast, mediate adaptive immunity: when primed against tumor antigens, they can mount targeted, antigen-specific killing and generate immunological memory. By infusing both cell types together, the investigators aimed to attack the tumor through complementary mechanisms, reducing the likelihood that an immune-escape variant could slip through unscathed.

The trial design reflected its early-phase purpose. This was a single-arm study, meaning there was no placebo or control group, and all nine enrolled patients received the active therapy. Each participant had a recurrent or progressive solid tumor and had already undergone between one and three prior lines of systemic treatment, placing them squarely in the population where standard options have been exhausted. SDH-Combi was manufactured from each patient’s own cells—an autologous approach that avoids the rejection risks associated with donor material—and was administered as an infusion once every two weeks, for up to eight infusions in total. The primary endpoint was safety and tolerability, while secondary endpoints included objective response rate, disease control rate, progression-free survival, and overall survival, with tumor measurements assessed according to the widely used RECIST v1.1 criteria.

On the safety front, the results were strikingly clean for a cell therapy. Among the nine treated patients, no grade 3 or higher treatment-related adverse event occurred, a finding the investigators report with a 95 percent confidence interval of 0.0 to 33.6 percent. No patient discontinued treatment because of toxicity, no cases of cytokine release syndrome were observed, and there were no anaphylactic reactions or treatment-related serious adverse events. Cytokine release syndrome—a potentially dangerous inflammatory cascade that has complicated other cellular immunotherapies, most famously CAR T cell treatments—was a particular concern the trial was designed to monitor, and its complete absence is a notable point in the therapy’s favor.

Tolerability metrics reinforced the safety picture. Six of the nine patients, or 66.7 percent, completed all eight planned infusions, and 64 of the 72 planned infusions across the study—88.9 percent—were actually administered, indicating that the treatment schedule was practical for most participants. The single serious adverse event in the trial was a grade 4 anemia in one patient, whose hemoglobin fell to a nadir of 4.5 grams per deciliter, but the investigators judged this event unlikely to be related to the study therapy. All other adverse events were grades 1 or 2, the mildest categories on the standard CTCAE v5.0 grading scale used to classify treatment-emergent events.

The preliminary efficacy signals, while modest, were not negligible. In the full analysis set of nine patients, the disease control rate—encompassing complete responses, partial responses, and stable disease—reached 66.7 percent, suggesting that for a majority of these heavily pretreated patients, the therapy was associated with at least a halt in tumor progression. The objective response rate, which counts only measurable tumor shrinkage, was 11.1 percent, corresponding to a single patient among the nine. Median overall survival had not been reached at the time of the safety assessment, though five of the nine patients had died by the follow-up date of 14 January 2026. The authors are appropriately measured about these numbers, noting that formal statistical inference is limited by the small, single-arm sample size and the absence of a comparator group.

One of the more intriguing aspects of the study is its attention to quality of life, an exploratory endpoint measured with the validated EORTC QLQ-C30 questionnaire. Patients reported improvements that crossed the threshold for a minimal clinically important difference—defined as a change of at least 10 points—in five of the six functional domains assessed: global health status and quality of life, physical functioning, role functioning, emotional functioning, and social functioning. All nine symptom domains also showed changes meeting or approaching that threshold, with constipation showing a marginal improvement of 11.1 points, while cognitive functioning did not reach the clinically important threshold. For a population of patients with advanced, recurrent cancer, subjective improvements in daily functioning and well-being carry real weight, even in an uncontrolled setting where placebo effects and natural fluctuation cannot be excluded.

The trial was conducted under ethical approval from the Institutional Review Board of the Ministry of Health of Mongolia, with clinical sites including hospitals in Ulaanbaatar, and was funded by Seoul Songdo Hospital in South Korea, where the cell processing facility manufactured the autologous products. The collaboration highlights how cellular immunotherapy research is expanding geographically, and the authors acknowledge the substantial manufacturing effort required to produce patient-specific cell products on a clinical schedule. Autologous therapies of this kind demand that a patient’s own immune cells be collected, processed, expanded, and quality-controlled before being reinfused—a logistical and technical undertaking that shapes which patients can be treated and how quickly.

The authors conclude that SDH-Combi was feasible and well tolerated, with preliminary signals of disease stabilization and quality of life improvement in previously treated patients, findings they say support further clinical evaluation of this biologically rational combination cellular immunotherapy. That framing is the appropriate one for a phase 1 study: the trial was never designed to prove efficacy, only to establish that the approach can be delivered safely and consistently. What it has demonstrated is that combining autologous natural killer cells with tumor-primed T lymphocytes can be done without the severe toxicities that have shadowed other cell therapies, and that the treatment can be administered on a demanding every-two-week schedule with most patients completing the full course.

The road ahead will require larger, controlled trials to determine whether the disease control signals translate into meaningful extensions of survival, and which tumor types benefit most. The field of combination cellular immunotherapy is betting on a simple premise: that cancers are too adaptable to be defeated by any single immune cell type, and that deploying innate and adaptive immunity together closes the escape routes tumors rely on. With no grade 3 or higher treatment-related events, nearly 90 percent of planned infusions delivered, and a majority of patients experiencing disease control, this first-in-human evaluation gives that premise its earliest real-world test—and a reason for the field to keep watching.

Subject of Research: Phase 1 trial of autologous NK cell and T lymphocyte combination immunotherapy for recurrent solid tumors

Article Title: Phase 1 clinical trial evaluating the safety and preliminary efficacy of autologous NK cells combined with T lymphocytes in patients with recurrent solid tumors

Article References: Kim, K.-J., Lee, N., Che, D. N., Lee, H.-J., Lee, H. N., Tungalag, S., Batsukh, K., Nyamdavaa, T., Sohn, S.-K., & Lee, J. K. (2026). Phase 1 clinical trial evaluating the safety and preliminary efficacy of autologous NK cells combined with T lymphocytes in patients with recurrent solid tumors. Cancer Immunology, Immunotherapy. https://doi.org/10.1007/s00262-026-04532-7

Image Credits: AI Generated

DOI: 10.1007/s00262-026-04532-7

Keywords: NK cells, T lymphocytes, cellular immunotherapy, solid tumors, phase 1 trial, autologous therapy, cancer immunotherapy, RECIST, quality of life, cytokine release syndrome, disease control, immune escape