Xilio Therapeutics shares rise 10.63% after-hours after Phase 2 data shows 40% ORR in MSS mCRC with high plasma TMB.

Xilio Therapeutics (XLO) surged 10.63% in after-hours trading following the announcement of late-breaking Phase 2 data for vilastobart in combination with atezolizumab. The trial demonstrated a 40% objective response rate (ORR) in heavily pre-treated patients with microsatellite stable (MSS) metastatic colorectal cancer (mCRC) without liver metastases and high plasma tumor mutational burden (TMB ≥10 mutations/Mb). The company highlighted that approximately 55% of MSS CRC patients have high plasma TMB, significantly expanding the potential target population compared to traditional tissue-based assays. The results, presented at the SITC 40th Annual Meeting, underscored the biomarker-driven approach’s promise and the therapy’s favorable safety profile, with minimal treatment-related adverse events. These findings, coupled with the upcoming investor webcast featuring expert discussions, likely fueled the post-market rally.