Navtemadlin boosts engineered T-cell killing of melanoma in vitro

What did the laboratory experiment show?

In a nearly seven-day laboratory comparison of engineered human T cells, those prepared with investigational p53 activator navtemadlin killed melanoma cells significantly better after about 40 hours. Their advantage continued throughout the experiment. They also showed stronger cancer-fighting activity without additional interleukin-2, a protein commonly used to support T-cell growth and survival.

The UCLA Health Jonsson Comprehensive Cancer Center team collected human T cells and compared cells prepared with navtemadlin against untreated cells. The researchers genetically engineered the cells to recognize a protein found on certain melanoma cells, then used specialized imaging to track the attack for nearly seven days.

Navtemadlin blocks MDM2, a protein that normally keeps p53 levels under control. Blocking MDM2 increased p53 activity. The comparison assessed the cells’ development, energy production and ability to fight cancer.

p53 is best known as the “guardian of the genome” because it prevents damaged cells from becoming cancerous. Scientists have studied that protective role extensively, while its role in regulating human T cells has remained less clear.

In plain terms, temporary p53 activation improved laboratory tumor killing, but no patient benefit has been established.

Why do engineered T cells falter?

Engineering a patient’s immune cells to recognize cancer does not guarantee that the cells will keep fighting it. Repeated exposure to cancer gradually weakens T cells’ ability to multiply and attack tumors, a decline known as exhaustion.

The laboratory process used to prepare those cells can also mature them too quickly. That reduces their chances of surviving and remaining effective over time, which limits the potential durability of engineered T-cell treatments.

Two approaches face this problem: chimeric antigen receptor (CAR) T-cell therapy and T-cell receptor (TCR) therapy. Both collect a patient’s immune cells, genetically modify them in a laboratory to recognize cancer, then return the cells to the patient to attack tumors.

These treatments have transformed care for certain blood cancers. Researchers increasingly study them for solid tumors, including melanoma, but persistence and sustained tumor killing remain central obstacles.

In plain terms, recognition alone cannot carry engineered T cells through repeated tumor exposure.

Which cellular changes suggest a longer response?

Treated cells had greater energy reserves. They were also more likely to produce interferon-gamma and granzyme B, two cancer-fighting proteins that help immune cells coordinate an attack and destroy cancer cells.

They were more likely to become central memory T cells. That subset has a greater capacity to survive and multiply when it encounters its target again, a feature linked in this study to a potentially longer-lasting response.

The treated cells also carried fewer molecular signs of exhaustion. Together, the shifts suggested that navtemadlin-treated cells might remain effective longer than untreated cells, although the experiments measured laboratory behavior rather than treatment outcomes in patients.

Joseph Crompton, MD, PhD, assistant professor of surgery at the David Geffen School of Medicine at UCLA and senior author, said: “This is one of the first studies to link p53, one of the most extensively studied proteins in biology, to T-cell exhaustion in humans.”

He added: “While p53 has long been known for its role in preventing cancer, our findings suggest it may also play an important role in helping immune cells maintain their ability to fight it. This opens up a new avenue for developing more effective cancer immunotherapies.”

In plain terms, the laboratory signal points to better endurance, not proven benefit in people.

Could this work with current cell manufacturing?

Adding navtemadlin during cell preparation could fit into existing manufacturing processes. That could improve engineered T-cell therapies without an entirely new treatment or additional genetic modifications.

Concentration determines whether that benefit comes with cell loss. At lower concentrations, navtemadlin encouraged healthy memory T-cell development without substantially reducing the overall number of viable cells. Higher concentrations caused more cells to die.

The concentration effect shows why any use of this approach would require careful control of p53 activation. The preparation step must preserve enough viable cells to retain the improvement seen in the laboratory.

In plain terms, the drug can strengthen the cells, but excess exposure can kill them.

What remains before a patient benefit?

The study, “p53 activation via pharmacologic MDM2 inhibition constrains exhaustion and enhances antitumor function of human CD8+ T cells,” appeared in Frontiers in Immunology on September 18, 2026. Alexandra Boix de Jesus led the author list, and Crompton was senior author. Its DOI is 10.3389/fimmu.2026.1910235.

The author list also included Hy B. Dao, Anthony Imani, Gabriel A. Rodriguez, Michael S. Shehata, Rachana R. Chandran, Stuart A. Fine, Sin Y. Lim, Michelle To, Serena Y. Lofftus, Nicolas Pedroncelli, Fritz C. Eilber, Brigitte N. Gomperts, Tyler R. McCaw and Cristina Puig-Saus.

Partial funding came from the American College of Surgeons; the UCLA Broad Center of Regenerative Medicine and Stem Cell Research; the UCLA Health Jonsson Comprehensive Cancer Center; the Tower Cancer Research Foundation; the Sarcoma Foundation of America; and the National Cancer Institute of the National Institutes of Health under the Early-Stage Surgeon Scientist Program.

Navtemadlin remains investigational. The next question is whether controlled p53 activation can improve engineered T-cell persistence and tumor killing in patients while preserving viable cells. Until then, the study supplies a manufacturing hypothesis, not a new melanoma treatment standard.

In plain terms, the strategy must now show longer-lasting tumor control in patients before it can become a melanoma treatment.