Clasp Therapeutics has announced the dosing of the first patient in a Phase 1 clinical trial for its innovative T-cell engager (TCE), CLSP-1025. The trial, known as GUARDIAN-101, represents a significant milestone in the company's efforts to bring unprecedented precision to immuno-oncology treatments. CLSP-1025 is designed to specifically target cancer cells that express the p53R175H mutation, which is prevalent in various solid tumors, including those affecting the colon, pancreas, lungs, stomach, esophagus, reproductive organs, and prostate. Traditional TCEs often target proteins found on both tumor and normal cells, leading to potential toxicity and side effects. In contrast, Clasp's TCEs focus on tumor-specific peptides derived from cancer-causing mutations, ensuring absolute specificity and reducing the risk of damaging healthy tissues. The p53R175H mutation, a truncal mutation that arises early in tumor development and is present in all tumor cells, makes it an optimal target for immune system engagement. Furthermore, Clasp’s pHLAre (precise HLA redirecting engagers) molecules are engineered to mimic the natural interaction between a T cell receptor and a cancer cell, enhancing the effectiveness of the immune response against the tumor. “Dosing the first patient in the GUARDIAN-101 trial is a transformative moment for Clasp Therapeutics,” said Dr. Lauren Harshman, M.D., Senior Vice President of Clinical Development at Clasp. “This advancement brings us closer to realizing the full potential of our pHLAre platform, which aims to address the limitations of existing T-cell engagers and provide a breakthrough treatment option for patients.” At the 2025 American Association for Cancer Research (AACR) Annual Meeting, Clasp presented nonclinical data that support the clinical development of CLSP-1025. The data highlight the candidate's selectivity, activity, pharmacokinetics, and safety profile, reinforcing its promise as a targeted therapy. About GUARDIAN-101 and CLSP-1025 The GUARDIAN-101 Phase 1 dose escalation study is designed to evaluate the safety and initial anti-tumor activity of CLSP-1025. CLSP-1025 is a bispecific antibody-like molecule that directs a patient's T cells to the tumor, facilitating a precise and powerful immune response to eliminate cancer cells. The molecule targets the p53R175H peptide in the context of HLA-A02:01. To participate in the trial, patients must be HLA-A02:01 positive and have an advanced solid tumor with the p53R175H mutation. The primary goal of this Phase 1 study is to determine the optimal dose of CLSP-1025 for subsequent trials. For more information about the study, visit clinicaltrials.gov (NCT06778863). About Clasp Therapeutics, Inc. Clasp Therapeutics is at the forefront of precision immuno-oncology, developing next-generation T-cell engagers that target tumor-specific oncogenic driver mutations. These mutations are common in difficult-to-treat cancers, and Clasp’s platform identifies neoantigens associated with such mutations to develop TCEs that can selectively bind to HLA-presented peptides derived from cancer drivers. This approach allows Clasp’s TCEs to be versatile and applicable to a wide range of cancers with high unmet medical needs. To learn more about Clasp Therapeutics, visit their website at www.clasptx.com. pHLAre is a registered trademark of Clasp Therapeutics, Inc. All rights reserved. For additional news and updates from Clasp Therapeutics, stay tuned to their communications channels.