Xilio Therapeutics(US:XLO) Globenewswireยท2025-11-07 14:05Core Insights - Xilio Therapeutics announced a 40% objective response rate (ORR) in heavily pre-treated patients with microsatellite stable (MSS) metastatic colorectal cancer (mCRC) without liver metastases and with high plasma tumor mutational burden (TMB) [1][2][9] - Approximately 55% of patients with MSS CRC are estimated to have high plasma TMB, indicating a significant patient population with unmet medical needs [1][2][5] - The company will host a conference call on November 10, 2025, to discuss these findings with leading cancer experts [1][12] Clinical Data - The Phase 2 trial evaluated vilastobart, a tumor-activated anti-CTLA-4, in combination with atezolizumab (Tecentriq) [1][15] - A statistically significant correlation was found between plasma TMB status and response, with a p-value of 0.05 [9][13] - Among evaluable patients, 62.5% were classified as TMB-high, and all responders were TMB-high, demonstrating deep and durable responses with reductions in target lesions of up to 71% [13] Safety Profile - The combination of vilastobart and atezolizumab showed a differentiated and generally well-tolerated safety profile, with treatment-related adverse events primarily being Grade 1 or 2 [10] - Only 5% of patients discontinued treatment due to adverse events, and 7% experienced colitis of any grade [10] Biomarker Potential - Plasma-based TMB assays are more sensitive than traditional tissue-based assays and can provide a comprehensive assessment of mutational load, accounting for tumor heterogeneity [4][6] - The use of plasma TMB as a predictive biomarker could help identify MSS mCRC patients who may benefit from vilastobart treatment [2][3] Development Plans - Xilio is actively seeking a partner to further develop vilastobart in combination with PD-(L)1 or PD1-VEGF for MSS CRC and other tumor types [11]