Summary of Xilio Therapeutics Conference Call Company Overview - **Company**: Xilio Therapeutics (NasdaqGS:XLO) - **Focus**: Development of novel masked biologics using proprietary protein engineering technology - **Key Products**: Velastigard (anti-CTLA-4), efarindodekin alfa (IL-12), XTX501 (PD-1/IL-2) Industry Context - **Industry**: Oncology, specifically focusing on immunotherapy for colorectal cancer - **Target Condition**: Microsatellite stable colorectal cancer (MSSCRC), which constitutes 95% of all colon cancers Key Data Updates - **SITC Conference**: Presented new clinical data for Velastigard in combination with Tislelizumab for MSSCRC - **Clinical Data**: - Velastigard demonstrated a **26% overall response rate** in late-line metastatic MSSCRC without liver metastases, compared to a **2% response rate** for Tislelizumab as monotherapy [8][9][10] - In a biomarker-defined population with high plasma tumor mutational burden (TMB), the overall response rate was **40%** [14][15] Biomarker Insights - **Plasma TMB**: - Approximately **55%** of MSSCRC patients have high plasma TMB (greater than 10 mutations per megabase) [12][15] - High plasma TMB correlates with better response rates to Velastigard and Tislelizumab combination therapy [12][14] - Plasma-based TMB assays are more sensitive and provide a comprehensive assessment compared to traditional tissue-based assays [11][19] Safety Profile - **Safety Data**: - Velastigard showed a **7% incidence of colitis**, significantly lower than traditional anti-CTLA-4 therapies [16][17] - Discontinuation rate for the combination therapy was only **5%**, indicating a favorable safety profile [17] Future Development Plans - **Partnerships**: Actively seeking partnerships to develop Velastigard in combination with PD-1, PD-L1, or newer PD-1 bispecifics [43][44] - **Regulatory Path**: Plans to assess the regulatory pathway for future development using plasma TMB as a predictive biomarker [43][44] - **Upcoming Milestones**: Additional phase two data for Velastigard expected in the first half of 2026 [47] Additional Clinical Programs - **Efarindodekin alfa**: Phase one data showed deep monotherapy responses and a well-tolerated safety profile [45] - **Masked T-cell Engagers**: Preclinical data demonstrated broad applicability and potential for reduced systemic toxicity [46] Conclusion - Xilio Therapeutics is positioned to leverage its innovative masking technology to address significant unmet medical needs in oncology, particularly in MSSCRC, with promising clinical data supporting the efficacy and safety of its lead product, Velastigard. The identification of plasma TMB as a predictive biomarker enhances the potential for targeted therapies in this patient population.

Vilastobart Clinical Data and Opportunity - Vilastobart, in combination with atezolizumab, showed a 40% Overall Response Rate (ORR) in MSS mCRC patients without liver metastases and with high plasma TMB[30, 42] - 63% of plasma TMB-evaluable patients had high plasma TMB (≥10 mutations/Mb) in the Phase 2 trial, including all TMB-evaluable responders[32, 33, 42] - A statistically significant correlation (p=0.05) was observed between plasma TMB status and response to vilastobart plus atezolizumab[33, 42] - The combination of vilastobart and atezolizumab demonstrated a differentiated safety profile, with a low discontinuation rate of 5% and only 7% of patients experiencing colitis of any grade[35, 36, 42] Market and Competitive Landscape - Approximately 95% of mCRC patients are MSS, and standard of care in 3L+ provides minimal benefit (1-6% ORR)[23] - Real-world data indicates that approximately 55% of patients with MSS CRC have high plasma TMB, which is substantially higher than historically reported with tissue-based TMB assays[28, 42] - Next-generation anti-CTLA-4 agents in development show promising clinical efficacy in MSS mCRC, with ORRs ranging from 8-29% and discontinuation rates due to AEs up to ~30%[21] Technology and Pipeline - Xilio's clinically-validated platform technology is being applied across diverse mechanisms and architectures, including antibodies, cytokines, bispecifics, and T cell engagers[13, 14] - Efarindodekin Alfa (tumor-activated IL-12) demonstrated promising clinical efficacy with a generally well-tolerated safety profile in Phase 1 in patients with advanced solid tumors[44] - Masked T cell engager programs demonstrated potent anti-tumor activity with favorable tolerability across a diverse range of targets in preclinical models[50, 51, 52] Financial Outlook and Milestones - The company anticipates a cash runway into Q1 2027, including a $175 million development milestone received under the Gilead license in Q4 2025[53] - Anticipated milestones include reporting updated Phase 2 data for vilastobart in combination with atezolizumab in metastatic MSS mCRC in 1H 2026 and IND submissions for at least two masked T cell engager programs in 2027[53]