---
schema_version: "secwatch.filing_event.v1"
accession: "0001193125-25-271189"
form_type: "8-K"
ticker: "XLO"
cik: "0001840233"
company_name: "Xilio Therapeutics, Inc."
filed_at: "2025-11-07T23:59:59+00:00"
generated_at: "2026-05-16T23:08:07.167461+00:00"
event_type: "other_material"
sentiment: "positive"
materiality_score: 0.85
calibrated_materiality_score: 0.85
confidence: "high"
source: SEC EDGAR
---

# Xilio reports 40% ORR in MSS mCRC with high plasma TMB; advances masked T cell engager programs

## Summary
- Vilastobart + atezolizumab: 40% ORR in heavily pre-treated MSS mCRC without liver mets and high plasma TMB (≥10 mut/Mb); p=0.05 correlation.
- Estimated 55% of MSS CRC patients have high plasma TMB via Guardant360 assay, vs <10% by tissue TMB.
- Preclinical masked T cell engagers show reduced systemic toxicity and enhanced durability with costimulation; PSMA candidate nominated Q3 2025.
- Phase 1 efarindodekin alfa: well-tolerated at >100-fold MTD of rhIL-12, 2 PRs in advanced solid tumors, immune infiltration.
- Vilastobart ctDNA data: deep reductions associated with response; 2 patients achieved endoscopic CR with undetectable ctDNA.

## SEC filing metadata
- accession: 0001193125-25-271189
- form_type: 8-K
- ticker: XLO
- cik: 0001840233
- company_name: Xilio Therapeutics, Inc.
- filed_at: 2025-11-07T23:59:59+00:00
- event_type: other_material
- sentiment: positive
- materiality_score: 0.85
- calibrated_materiality_score: 0.85
- confidence: high
- sec_items: 7.01, 9.01
- EDGAR index: https://www.sec.gov/Archives/edgar/data/1840233/000119312525271189/0001193125-25-271189-index.htm
- EDGAR primary document: https://www.sec.gov/Archives/edgar/data/1840233/000119312525271189/xlo-20251107.htm

## Machine-readable alternates
- HTML: https://secwatch.observer/filing/0001193125-25-271189
- JSON: https://secwatch.observer/filing/0001193125-25-271189.json
- Plain text: https://secwatch.observer/filing/0001193125-25-271189.txt

This AI-assisted summary is a reading aid. Review the linked SEC EDGAR filing before relying on any specific claim.