Vilastobart, a tumor-activated, Fc-enhanced anti-CTLA-4
Vilastobart is an investigational tumor-activated,
Fc-enhanced anti-CTLA-4 designed to block CTLA-4
and deplete regulatory T cells when activated (unmasked) in the tumor microenvironment (TME).
About CTLA-4
Checkpoint inhibition is one of the foundational mechanisms of immunotherapy (I-O) and occurs when a drug blocks a checkpoint receptor and an inhibitory ligand from binding and enables T cells to kill cancer cells. CTLA-4 is a common checkpoint protein that plays a critical role in limiting the ability of T cells to recognize cancer cells. CTLA-4 is also a key marker protein present on immune suppressive regulatory T cells (TREGs) that limits the immune system’s ability to fight cancer.
About the Phase 1/2 Clinical Trial for Vilastobart (anti-CTLA-4) (Monotherapy and Combination)
Vilastobart is currently being evaluated in combination with atezolizumab (Tecentriq®) in a Phase 1/2 multicenter, open-label clinical trial. The efficacy and safety of the combination is being evaluated in Phase 2 in patients with microsatellite stable (MSS) metastatic colorectal cancer (mCRC) with and without liver metastases.
Vilastobart (formerly XTX101)
Presentations & Publications
11/07/2025
Vilastobart Poster Presentation at the 2025 Society for Immunotherapy of Cancer (SITC) Annual Meeting
Plasma Tumor Mutational Burden (pTMB) Enriched for Response to Vilastobart in Combination with Atezolizumab in Patients with Microsatellite Stable (MSS) Metastatic Colorectal Cancer (mCRC)
11/07/2025
Vilastobart Poster Presentation at the 2025 Society for Immunotherapy of Cancer (SITC) Annual Meeting
ctDNA as a Potential Surrogate Biomarker for Response to Combination Vilastobart and Atezolizumab in Heavily Pretreated Microsatellite Stable (MSS) Metastatic Colorectal Cancer (mCRC) (NCT04896697)
05/31/2025
Vilastobart Poster Presentation at the 2025 American Society of Clinical Oncology (ASCO) Annual Meeting
Vilastobart (XTX101), a Tumor-Activated, Fc-Enhanced Anti–CTLA-4 Monoclonal Antibody, in Combination with Atezolizumab in Patients with MSS Colorectal Cancer
01/25/2025
Vilastobart Poster Presentation at the 2025 American Society of Clinical Oncology Gastrointestinal (ASCO GI) Cancer Symposium
Phase 1/2 Study of Vilastobart (XTX101), a Tumor-Activated, Fc-enhanced Anti-CTLA-4 Monoclonal Antibody, in Combination with Atezolizumab in Patients with Advanced Solid Tumors and in MSS CRC
More XILIO News
11/07/2024
Vilastobart Poster Presentation at the 2024 Society for Immunotherapy of Cancer (SITC) Annual Meeting
Phase 1/2 Study of Vilastobart (formerly XTX101), a Tumor-Activated, Fc-enhanced Anti-CTLA-4 Monoclonal Antibody, in Combination with Atezolizumab in Patients with Advanced Solid Tumors
12/12/2023
XTX101 Publication in Journal for ImmunoTherapy of Cancer
XTX101, a tumor-activated, Fc-enhanced anti-CTLA-4 monoclonal antibody, demonstrates tumor-growth inhibition and tumor-selective pharmacodynamics in mouse models of cancer
12/07/2023
XTX101 Poster Presentation at the 2023 European Society for Medical Oncology (ESMO) Immuno-Oncology Congress
Phase 1/2 Study of XTX101, a masked, tumor-activated Fc-enhanced anti-CTLA-4, in patients with advanced solid tumors
11/12/2021
XTX101 (CTLA-4) Poster Presentation at the Society for Immunotherapy in Cancer’s 36th Annual Meeting (SITC)
A First-in-Human, Multicenter, Phase 1/2, Open-Label Study of XTX101 in Patients with Advanced Solid Tumors
05/12/2021
XTX101 (CTLA-4) Poster Presentation at The New York Academy of Sciences’ Frontiers in Cancer Immunotherapy 2021 Virtual Symposium
Tumor-Activated Anti-CTLA-4 Monoclonal Antibody, XTX101, Demonstrates Monotherapy and Anti-PD-1 Combination Benefit in Preclinical Models
11/13/2020
XTX101 (CTLA-4) Poster Presentation at 35th Annual Meeting of The Society for Immunotherapy of Cancer
Tumor-activated Fc-engineered Anti-CTLA-4 Monoclonal Antibody, XTX101, Demonstrates Tumor-selective PD and Efficacy in Preclinical Models