Most antibody-drug conjugates work by finding a protein expressed on cancer cells, binding it, and dropping a cytotoxic payload that kills the cell.
The whole field has spent the last decade refining this playbook. Better antibodies, better linkers, better payloads. Higher therapeutic indices in tumors that overexpress the target.
What if the target wasn’t the cancer cell at all?
StarkAge Therapeutics is bringing preclinical data to AACR 2026 for STX-1, a first-in-class senolytic ADC. The target is DPP4 (also known as CD26), a surface marker that is enriched on senescent cells inside the tumor microenvironment. The payload selectively kills the cells that bind it. The cells it kills are old, damaged, and supposedly helping the tumor survive.
That’s a different mental model.
STX-1 mechanism: targeting senescent cells in the TME
Senescent cell
DPP4 / CD26 enriched
STX-1 ADC
Anti-DPP4 + cytotoxic payload
Cell death
TME reset
Senescent cells secrete inflammatory factors that support tumor growth and immune evasion
The biology behind this approach has been bubbling for a few years. Senescent cells (cells that have stopped dividing but haven’t died) accumulate in tumors as a side effect of chemotherapy, radiation, and aging. They secrete a noxious cocktail of inflammatory factors and growth signals known as the senescence-associated secretory phenotype (SASP). The SASP suppresses anti-tumor immunity, recruits immunosuppressive cells, and provides growth signals to surviving tumor cells.
Clearing them should, in theory, reset the tumor microenvironment in a useful direction.
The first-generation senolytics (compounds like dasatinib + quercetin, navitoclax, and various BH3 mimetics) showed the concept worked in vitro and in some animal models. They also tended to be either not selective enough (hitting healthy stem cells) or too selective (working only in narrow contexts). The clinical translation has been slow.
StarkAge’s approach is to get the selectivity from a different direction: use an antibody to target a senescence-enriched marker, then deliver a payload that only kills cells the antibody binds. Same playbook as oncology ADCs, applied to a completely different cell biology.
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The lead indication is metastatic colorectal cancer, where senescent cell accumulation has been linked to chemoresistance and poor outcomes. The preclinical data, presented in collaboration with Gustave Roussy Institute, reportedly show target binding, internalization, and target-dependent cytotoxicity, plus enhanced efficacy in senescence-enriched tumor models.
That’s the right preclinical package. Whether it translates to clinical benefit is the open question. DPP4 is also expressed on some normal immune cells, including T cells and certain epithelial populations, so the off-tumor profile will need to be tight.
There’s no IND filing or clinical timeline disclosed yet.
The competitive picture for ADCs in general keeps evolving. GlycoNex is targeting glycan structures rather than proteins. CrossBridge Bio, recently acquired by Lilly, is pushing dual-payload designs. Each represents a different bet on what makes the next generation of ADCs differentiated. StarkAge’s bet is on the target biology rather than the chemistry.
If the senolytic-ADC concept works, it doesn’t replace existing oncology ADCs. It complements them. You could imagine a regimen where a HER2 ADC kills the bulk of the tumor, then a senolytic ADC mops up the senescent cells the chemo drove into existence. Combination therapy where the agents target different cell populations within the same tumor.
That’s the long-term vision anyway. For now, this is preclinical AACR data. The path from poster to IND is its own multi-year project. But the modality is genuinely new.
Worth tracking.
