WALTHAM, Mass. — November 13, 2025 — Leads & Copy — Xilio Therapeutics, Inc. (Nasdaq: XLO) has announced pipeline progress, business updates, and financial results for the third quarter ending September 30, 2025.
The clinical-stage biotechnology company, focused on discovering and developing tumor-activated immuno-oncology therapies, highlighted several key achievements. Noteworthy progress includes reported Phase 2 data at SITC for vilastobart, which demonstrated a 40% Objective Response Rate (ORR) in heavily pretreated patients with microsatellite stable (MSS) metastatic colorectal cancer (mCRC) without liver metastases and high plasma tumor mutational burden (TMB). Additionally, Phase 1 data for efarindodekin alfa was presented at SITC, showcasing promising monotherapy anti-tumor activity and a generally well-tolerated safety profile in patients with advanced solid tumors. The company also announced new preclinical data at SITC for masked T cell engager programs, supporting their potential and showing efficient masking, anti-tumor activity and a broad therapeutic index.
René Russo, Pharm.D., president and chief executive officer of Xilio, emphasized the company’s progress in advancing its pipeline of masked immunotherapies and validating its masking technology.
For the vilastobart program, Phase 2 clinical trial data presented at the Society for Immunotherapy of Cancer (SITC) 40th Annual Meeting demonstrated a 40% objective response rate (ORR) in heavily pre-treated, plasma tumor mutational burden (TMB) high patients with MSS mCRC without liver metastases. A statistically significant correlation (p=0.05) was observed between plasma TMB status and response, with approximately 55% of patients with MSS mCRC estimated to have high plasma TMB.
Additional Phase 2 data presented at SITC indicated the potential for circulating tumor DNA (ctDNA) as an early predictive biomarker for response to treatment with vilastobart in combination with atezolizumab in patients with MSS mCRC. Xilio is seeking a partner to further develop vilastobart in combination with PD-(L)1 or PD1-VEGF in MSS CRC and other tumor types.
Efarindodekin alfa is being evaluated in an ongoing Phase 1/2 clinical trial in patients with advanced solid tumors. Phase 1 monotherapy dose escalation data presented at SITC demonstrated promising monotherapy anti-tumor activity and a generally well-tolerated safety profile.
In September 2025, Xilio announced the selection of an initial recommended phase 2 dose (RP2D) and schedule for efarindodekin alfa and initiated patient dosing in the Phase 2 portion of the clinical trial, achieving a $17.5 million development milestone under its license agreement with Gilead Sciences, Inc. Xilio has completed enrollment in the Phase 1A monotherapy dose escalation and Phase 1B monotherapy dose expansion portions of the ongoing Phase 1/2 clinical trial.
XTX501, a bispecific PD-1 / masked IL-2, is advancing through investigational new drug (IND)-enabling studies, with plans to submit an IND application in mid-2026.
New preclinical data for masked T cell engager programs was presented at SITC, highlighting the potential for the company’s masking technology to expand the therapeutic window for T cell engagers. Development candidates are anticipated for the CLDN18.2 program in the fourth quarter of 2025 and for its STEAP1 program in the first half of 2026. IND applications for at least two of these programs are anticipated in 2027.
Xilio’s cash and cash equivalents were $103.8 million as of September 30, 2025, compared to $55.3 million as of December 31, 2024. Collaboration and license revenue was $19.1 million for the quarter ended September 30, 2025, compared to $2.3 million for the quarter ended September 30, 2024. Research & Development (R&D) expenses were $14.3 million for the quarter ended September 30, 2025, compared to $10.8 million for the quarter ended September 30, 2024. General & Administrative (G&A) expenses were $6.7 million for the quarter ended September 30, 2025, compared to $6.3 million for the quarter ended September 30, 2024. Net loss was $16.3 million for the quarter ended September 30, 2025, compared to $14.0 million for the quarter ended September 30, 2024.
Based on current operating plans, Xilio anticipates that its cash and cash equivalents will be sufficient to fund its operations into the first quarter of 2027.
Investor Contact: Alex Lobo, Precision AQ, alex.lobo@precisionaq.com
Media Contact: Josie Butler, 1AB, josie@1abmedia.com
Source: Xilio Therapeutics, Inc.
