For nearly two decades, cancer immunotherapy has been built around two molecular targets: PD-1 and CTLA-4. Both are “checkpoints” — brakes that keep T cells, the immune system’s killer cells, from attacking the body’s own tissue. Drugs that block those brakes (checkpoint inhibitors such as pembrolizumab and ipilimumab) freed the immune system to attack tumors and reshaped oncology. But a large share of patients still don’t respond, or respond and then relapse, and researchers have long suspected there are other brakes still unaccounted for.
A team at the Montreal Clinical Research Institute (IRCM) and Université de Montréal, led by Dr. André Veillette, reports in Nature that they’ve found one: a receptor called SLAMF6, and it works in a way neither PD-1 nor CTLA-4 does.
What makes an immune checkpoint, and why this one is different
PD-1 and CTLA-4 are both engaged from the outside: a tumor cell (or another cell in its vicinity) displays a matching ligand, that ligand binds the receptor on the T cell’s surface, and the resulting signal tells the T cell to stand down. Block the ligand-receptor interaction, and the brake releases — that’s the entire mechanism behind existing checkpoint-inhibitor drugs.
SLAMF6 doesn’t need a tumor cell to switch it on. According to the IRCM’s account of the study, SLAMF6 molecules on the T cell’s own surface interact with each other — a “cis,” or same-cell, homotypic interaction — and that self-interaction alone is enough to trigger an inhibitory signal. The T cell suppresses itself, independent of anything the tumor is doing. That’s the basis for describing SLAMF6 as an independent checkpoint, structurally and mechanistically distinct from the tumor-facing brakes existing drugs target.
In the study, blocking that self-interaction with newly developed monoclonal antibodies had the opposite effect: T cells activated more strongly, fewer of them slid into the “exhausted,” non-functional state that chronic tumor exposure typically produces, and tumor growth was inhibited in mouse models.
Why an independent checkpoint matters
The practical case for SLAMF6 is straightforward: because it operates through a mechanism current checkpoint inhibitors don’t touch, it’s a plausible target for the patients those drugs fail — either as an alternative for people who don’t respond to PD-1/PD-L1 blockade, or in combination with it, on the reasoning that stacking brakes that work through different pathways should outperform blocking just one. Combination checkpoint blockade (anti-PD-1 plus anti-CTLA-4) is already standard practice in several cancers precisely because two different brakes release more immune activity than either alone; a third, mechanistically unrelated brake is a genuinely new lever, not a variation on the first two.
What stage this research is actually at
This is preclinical, mechanistic research, not a clinical result. The published data are from cellular and mouse-model experiments; no human trial of a SLAMF6-targeting antibody has been reported. The IRCM states the team’s next step is advancing these antibodies toward early-phase clinical trials — the normal, multi-year path any newly validated cancer-immunotherapy target has to clear (safety and dose-finding studies, then efficacy trials) before it could become an approved treatment. Readers should treat this as a genuine advance in understanding how T cells regulate themselves, not as a therapy that is imminently available.
Funding and institutional context
The work was carried out at the IRCM’s Laboratory of Molecular Oncology and is credited to Dr. Veillette, who directs that unit and is a full professor in the Department of Medicine at Université de Montréal; co-authors are also affiliated with McGill University. Notably for CASRAI’s research-administration audience, the IRCM attributes funding to a stack of predominantly Canadian public and philanthropic sources: the Canadian Institutes of Health Research (CIHR), the Terry Fox Research Institute, BioCanRx, Québec’s Ministry of Economy, Innovation and Energy, and the Canadian Foundation for Innovation. It’s a useful example of how a single major discovery-stage finding typically rests on several stacked, non-overlapping funder relationships rather than one grant — a funding pattern research offices managing multi-source biomedical awards will recognize.
The source
The study, “SLAMF6 as a drug-targetable suppressor of T cell immunity against cancer”, was published in Nature (vol. 652, 2026) by Bin Li, Ming-Chao Zhong, Cristian Camilo Galindo, Jiayu Dou, Jin Qian, Zhenghai Tang, Dominique Davidson and André Veillette. See also the IRCM press release for the institutional summary this article draws on.
