Xilio Therapeutics reported third-quarter 2026 results alongside progress in its oncology pipeline. The main development is that its experimental drug XTX501 has entered clinical testing; two other programs remain in preclinical development, with the company targeting regulatory submissions in late 2027.
The announcement also says Xilio reported quarterly financial results, but the material provided does not include the figures.
Key details
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XTX501 has begun Phase 1 testing. The first patient has been dosed in a Phase 1/2 trial, whose initial stage is testing the drug in people with metastatic non-small cell lung cancer and certain other advanced solid tumors. Xilio plans to report initial Phase 1 data in metastatic lung cancer in the fourth quarter of 2027.
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The drug combines two immune approaches in one molecule. XTX501 is designed to block the PD-1/PD-L1 pathway while using a masked, high-potency form of IL-2 to stimulate T cells. Xilio’s approach is intended to activate the IL-2 treatment primarily in tumors, addressing toxicity and other limitations associated with non-masked IL-2 therapies. These are design goals, not demonstrated clinical results.
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Two masked T-cell engager programs are progressing toward planned 2027 submissions.
- XTX602 targets CLDN18.2, a marker found in several gastrointestinal cancers, and includes a built-in CD2 co-stimulatory component intended to strengthen T-cell activity. Xilio is conducting studies needed to support an investigational new drug application and plans to submit one in the fourth quarter of 2027.
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XTX701 targets both PSMA and STEAP1, markers found across many metastatic castration-resistant prostate cancers. Targeting both is intended to address variation in which marker tumors express. Its design also includes CD2 co-stimulation. Xilio is conducting preparatory studies and plans to submit an application in the fourth quarter of 2027.
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The T-cell engager designs use masking to limit activity outside tumors. Xilio says its approach masks the T cells’ CD3-binding domain, and in XTX602 also masks the tumor-targeting domain. The drugs are designed to become active selectively in the tumor environment. The company is advancing two wholly owned masked T-cell engager programs and another in collaboration with AbbVie; the announcement does not identify the AbbVie program in the material provided.
Plain-English implications
XTX501 has moved from development into human testing, but the release provides no clinical results yet; the first planned data are more than a year away. XTX602 and XTX701 are earlier-stage programs, with their next stated milestones being planned regulatory submissions in late 2027.