Clasp Therapeutics, Inc.

CAMBRIDGE, MA and ROCKVILLE, MD, USA I April 28, 2025 I Clasp Therapeutics, a biotechnology company bringing unparalleled precision to immuno-oncology with next-generation T-cell engagers (TCEs), today announced new data supporting the development of its lead program, CLSP-1025. Nonclinical data underpinning the GUARDIAN-101 Phase 1 study of CLSP-1025 were presented at the 2025 American Association for Cancer Research (AACR) Annual Meeting in Chicago, IL on April 27, 2025. Clasp’s approach centers on developing precision TCEs with absolute tumor specificity by targeting oncogenic driver mutations presented by human leukocyte antigen (HLA) on cancer cells. CLSP-1025 exemplifies this strategy, selectively engaging the p53 R175H mutant peptide, presented by HLA-A*02:01, to direct a potent T cell response. Given that p53 is frequently mutated in cancer—with R175H as its most common variant—and HLA-A*02:01 is highly prevalent in the US, Europe, and Asia, CLSP-1025 has broad clinical potential. The promising nonclinical data presented at AACR support the clinical development of CLSP-1025 as a potentially transformative therapy designed to deliver durable anti-tumor responses while minimizing impact on healthy tissue. As the first clinical-stage TCE to target an oncogenic driver mutation, CLSP-1025 is currently being evaluated in the GUARDIAN-101 Phase 1 clinical trial. This study is assessing the safety, pharmacokinetics, pharmacodynamics, and preliminary antitumor activity of CLSP-1025 in HLA-A*02:01–positive patients with advanced solid tumors harboring the p53 R175H mutation. “At Clasp, we’re pioneering a new era of precision immuno-oncology – one that goes straight to the source by targeting the mutations that drive cancer formation and progression,” said Vipin Suri, Ph.D., Chief Scientific Officer of Clasp Therapeutics. “The nonclinical data we presented reinforce the promise of our approach and the potential of CLSP-1025 in the GUARDIAN-101 Phase 1 trial. These data mark a meaningful step forward in our mission to deliver targeted, more effective therapies for patients with limited options.” Data Highlights: About GUARDIAN-101 and CLSP-1025 Clasp’s Phase 1 GUARDIAN-101 dose escalation study evaluates 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, generating a precise immune response to selectively and potently eliminate cancer cells. CLSP-1025 is designed to target the p53 R175H peptide in the context of HLA-A*02:01. Enrolled patients must be HLA-A*02:01 positive and have an advanced solid tumor that harbors the p53 R175H mutation. This Phase 1 study will identify the dose of CLSP-1025 for use in future studies. Visit clinicaltrials.gov (NCT06778863) for more details. About Clasp Therapeutics, Inc. Clasp is pioneering precision in immuno-oncology through next-generation T-cell engagers (TCEs) that target tumor-specific oncogenic driver mutations common across hard-to-treat cancers. Clasp’s platform identifies mutation-associated neoantigens and develops TCEs that can selectively bind HLA (human leukocyte antigen)-presented peptides derived from these oncogenic drivers. With their unique properties, Clasp’s TCEs are adaptable for application across a variety of cancers with high unmet need. Please visit www.clasptx.com to learn more. SOURCE: Clasp Therapeutics

CAMBRIDGE, MA. & ROCKVILLE, MD.--( BUSINESS WIRE )--Clasp Therapeutics, a biotechnology company bringing unparalleled precision to immuno-oncology using next-generation TCEs, today announced new data validating the potential of its lead program, CLSP-1025. CLSP-1025 is a half-life extended TCE targeting cancer cells expressing the p53 R175H mutant peptide presented by HLA-A*02:01. Data demonstrating the therapeutic potential of CLSP-1025 will be presented at the Society for Immunotherapy of Cancer’s (SITC) 39th Annual Meeting on November 8, 2024. Clasp’s innovative approach focuses on developing TCEs with absolute tumor specificity (i.e., no anticipated off-tumor binding) by targeting shared cancer neoantigens derived from oncogenic driver mutations presented by human leukocyte antigen (HLA) on cancer cells. The company’s proprietary pHLAre™ platform mimics the natural immune synapse by bridging cancer cells and T cells through CD3 binding. This engagement activates T cells, resulting in potent targeting and destruction of cancer cells. CLSP-1025 targets the p53 R175H mutation, which is prevalent in a range of solid tumors such as colorectal, esophageal, gastric, gynecological, lung, pancreatic and prostate cancers. Together, Clasp’s data support advancing CLSP-1025 into clinical trials. CLSP-1025 is expected to be the first TCE targeting a shared cancer neoantigen to reach the clinic, with the first-in-human trial anticipated to begin in early 2025. “Clasp was built to bring absolute precision to the power of immunotherapies, thereby improving and extending the lives of people with cancer,” said Chief Executive Officer Rob Ross, M.D. “Building on this promising preclinical data, we look forward to advancing CLSP-1025 into the clinic. Today’s presentation marks a significant milestone in our mission to deliver a new class of precision TCEs that expand the reach of immunotherapy.” Data Highlights: Selectivity : CLSP-1025 demonstrates high selectivity for p53 R175H presented on HLA-A*02:01 Specifically binds the R175H mutant peptide and spares wildtype p53; No reactivity with any other human peptides presented on HLA-A*02:01; Sensitivity : CLSP-1025 activates T cells and effectively kills patient-derived organoids, demonstrating activity at endogenous target expression levels; Activity : CLSP-1025 induces the regression of established tumors in vivo . About Clasp Therapeutics, Inc. Clasp is pioneering precision in immuno-oncology through next-generation T cell engagers (TCEs) that target tumor-specific oncogenic driver mutations common across hard-to-treat cancers. Clasp’s platform identifies mutation-associated neoantigens and develops TCEs that can selectively bind HLA (human leukocyte antigen)-presented peptides derived from these oncogenic drivers. These innovative pHLAre TM molecules, precise HLA redirecting engagers, direct all T cell types to destroy the tumor. With their unique properties, Clasp’s TCEs are adaptable for application across a variety of cancers with high unmet need. Please visit www.clasptx.com to learn more.

CAMBRIDGE, MA. & ROCKVILLE, MD.--(BUSINESS WIRE)--Clasp Therapeutics, a biotechnology company bringing unparalleled precision to immuno-oncology using next-generation T cell engagers (TCEs), today announced it will present comprehensive preclinical data demonstrating the selectivity and activity of CLSP-1025, a TCE targeting a common p53 mutation, at the 2024 Annual Meeting of the Society for Immunotherapy of Cancer (SITC), being held November 8 - 10, 2024 in Houston, Texas and virtually. Presentation Details: Title: CLSP-1025, a novel bispecific T cell engager targeting a p53 R175H mutant peptide presented by HLA-A*02:01 Presentation Type: Poster Abstract Number: 1061 Date and Time: Friday, November 8, 2024, at 9 a.m. CT – 7 p.m. CT Location: Exhibit Halls AB, George R. Brown Convention Center in Houston, TX Presenters: Justina X Caushi, Alec R Andrews, James Bingham, Lenore Cullen, Anthony S Gizzi, Gillian A Kingsbury, Kaleigh Krapfl, Madison Curtis Siok, Catherine Souza, Kate Stokes and Michael F Maloney About Clasp Therapeutics, Inc. Clasp is pioneering precision in immuno-oncology through next-generation T cell engagers (TCEs) that target tumor-specific oncogenic driver mutations common across hard-to-treat cancers. Clasp’s platform identifies mutation-associated neoantigens and develops TCEs that can selectively bind HLA (human leukocyte antigen)-presented peptides derived from these oncogenic drivers. These innovative pHLAre TM molecules, precise HLA redirecting engagers, direct all T cell types to destroy the tumor. With their unique properties, Clasp’s TCEs are adaptable for application across a variety of cancers with high unmet need. Please visit to learn more. Contacts Media: Michael Galfetti Ten Bridge Communications 757-759-2576 mgalfetti@tenbridgecommunications.com