SLAMF6 Identified as Self-Activating T Cell Brake Behind Immunotherapy Resistance, New Monoclonal Antibodies Show Promise
核心洞察
Researchers at Université de Montréal and IRCM discovered that SLAMF6 (搜索) acts as an internal, self-activating immune checkpoint on T cells that operates independently of tumor signals, explaining why many cancers resist PD-1/PD-L1 inhibitors.
Unlike PD-1 or CTLA-4, SLAMF6 (搜索) binds to itself on the T cell surface, suppressing progenitor exhausted T cells and accelerating immune exhaustion without requiring any signal from the tumor microenvironment.
Custom monoclonal antibodies developed by the team blocked SLAMF6 (搜索) self-binding, increasing T cell activation, boosting durable immune cell populations, and producing strong anti-tumor responses in mouse models.
A team led by Dr. André Veillette at the Université de Montréal and the Montreal Clinical Research Institute (IRCM) (搜索) has identified SLAMF6 (搜索) — Signaling Lymphocytic Activation Molecule 6 — as a previously unrecognized internal brake on T cell immunity that may explain why a substantial proportion of cancer patients fail to respond to or eventually develop resistance to current immunotherapies. The landmark study, published June 9, 2026 in Nature, also describes newly developed monoclonal antibodies capable of neutralizing this brake, laying the foundation for what could become a new class of cancer immunotherapies.
A Fundamentally Different Immune Checkpoint
Most immune checkpoint inhibitors in clinical use today — including PD-1 inhibitors like pembrolizumab (Keytruda) and nivolumab (Opdivo), as well as CTLA-4 blockers — work by disrupting inhibitory signals that tumor cells or the tumor microenvironment send to T cells. SLAMF6 (搜索) operates through an entirely distinct mechanism: it activates itself through direct homotypic interactions on the T cell surface, binding to copies of itself on the same cell or neighboring T cells, without requiring any signal from the tumor.
This self-activating property means SLAMF6 (搜索) suppresses T cell activity regardless of whether the tumor expresses the corresponding ligand — precisely the scenario in many tumors that fail to respond to PD-1 or CTLA-4 inhibitors. When activated, SLAMF6 reduces the ability of T cells to attack cancer cells, decreases the production of strong and long-lasting T cells, and accelerates immune exhaustion, a state in which T cells progressively lose their effectiveness against cancer.
Critically, SLAMF6 (搜索) is preferentially expressed on progenitor or stem-like exhausted T cells — the specific population that retains the capacity for functional restoration after immune checkpoint blockade. By suppressing this population through a tumor-independent mechanism, SLAMF6 limits the immune response before T cells even fully engage with the tumor.
New Antibodies Demonstrate Strong Anti-Tumor Activity
To overcome SLAMF6 (搜索)'s inhibitory effects, Veillette and his colleagues developed custom monoclonal antibodies designed to prevent the molecule from binding to itself and triggering its suppressive signals. Laboratory testing yielded several promising results: increased activation of human T cells, larger numbers of durable immune cells, fewer exhausted T cells, and strong anti-tumor responses in mouse models. According to the researchers, these newly developed antibodies perform significantly better than any existing approach aimed at targeting SLAMF6.
The antibodies also showed promising synergy when combined with PD-1 inhibitors in preclinical models, suggesting potential for both monotherapy and combination strategies.
Clinical Implications and Next Steps
The discovery carries significant implications for patients who no longer benefit from PD-1 or PD-L1 treatments. Because SLAMF6 (搜索) acts autonomously within T cells rather than relying on tumor-specific expression, the therapeutic approach may be applicable across a far wider range of cancer types than current checkpoint inhibitors — potentially including the approximately 40 to 50 percent of solid tumors that respond poorly to PD-1 and CTLA-4 blockade.
"The discovery made by Dr. Veillette's team opens the door to a new chapter in immunotherapy," said Dr. Jean-François Côté, IRCM president and scientific director. "By identifying an internal brake that had until now gone unrecognized and by developing antibodies capable of neutralizing it, our researchers are offering an innovative solution to the limitations of current treatments."
The SLAMF6 (搜索) antibodies are currently in preclinical development. The next step will be early-stage clinical trials to evaluate safety and effectiveness in people with solid tumors and blood cancers. Human clinical trials would typically begin three to five years after promising mouse results, subject to Phase I safety studies.
The study, titled "SLAMF6 (搜索) as a drug-targetable suppressor of T cell immunity against cancer," was funded by the Canadian Institutes of Health Research, the Terry Fox Research Institute, BioCanRx, Québec's Ministry of Economy, Innovation and Energy, and the Canadian Foundation for Innovation.