Pheast Therapeutics Reports Initial Phase 1a Data Showing Early Clinical Activity and Target Engagement for PHST001 at AACR 2026

Initial clinical data highlight a differentiated safety and pharmacologic profile for PHST001, including target engagement, innate immune activation, and early signals of clinical activity

Preclinical studies further support activity in metastatic models and combination potential across multiple classes of anti-cancer therapies

REDWOOD CITY, Calif., April 17, 2026 (GLOBE NEWSWIRE) -- Pheast Therapeutics, a clinical-stage biotechnology company advancing macrophage-directed immunotherapies for cancer, today announced the presentation of initial Phase 1a clinical data and new preclinical findings for PHST001, an IgG4 anti-CD24 macrophage checkpoint inhibitor, at the American Association for Cancer Research® (AACR) Annual Meeting 2026.

“The data presented at AACR suggest that PHST001 may address a longstanding challenge in translating the therapeutic potential of macrophage biology into a cancer treatment with the right balance of activity and tolerability,” said Roy Maute, Ph.D., CEO and Co-founder of Pheast Therapeutics. “The preclinical data further support rationally designed therapeutic combinations informed by CD24 biology, reinforcing the breadth of PHST001’s development potential.”

In the ongoing Phase 1a first-in-human study, PHST001 was generally well-tolerated across dose-escalation cohorts. Most treatment-related adverse events were Grade 1 or 2, with a subset of patients experiencing transient neutrophil decreases that were manageable and not associated with clinical complications. The dataset demonstrated linear pharmacokinetics, increasing CD24 receptor occupancy at higher dose levels, and pharmacodynamic changes consistent with innate immune activation. Early signs of clinical activity were observed, including disease stabilization and tumor shrinkage.

In preclinical studies including patient-derived tumor xenograft models, PHST001 enhanced macrophage-mediated tumor control and prolonged survival in combination with chemotherapies and antibody-drug conjugates. PHST001 also inhibited metastatic spread and reduced metastatic burden across multiple in vivo models.

“Taken together, these clinical and preclinical findings begin to build the profile we are looking for in a macrophage checkpoint inhibitor: favorable tolerability, evidence of biological activity, and meaningful combination potential,” said Raphaël Rousseau, M.D., Ph.D., Chief Medical Officer of Pheast Therapeutics. “These data support continued development of PHST001 as a monotherapy and in combination with cytotoxic agents, where it may enhance macrophage-mediated clearance of treatment-damaged tumor cells.”

Pheast plans to present updated clinical data from the ongoing PHST001-101 study at a future medical meeting.

The AACR posters can be viewed at https://www.pheast.com/pipeline.

About CD24

CD24 is a cell surface protein that plays a key role in tumor immune evasion by engaging Siglec-10, an inhibitory receptor on macrophages. This interaction suppresses macrophage-mediated clearance of cancer cells, allowing tumors to evade destruction by the innate immune system. CD24 was identified as a novel macrophage checkpoint through foundational work by Dr. Amira Barkal, principal founder of Pheast. Along with other co-founders, Drs. Irving Weissman, Ravi Majeti, and Roy Maute, Pheast’s research forms the basis for therapeutic strategies targeting CD24 to activate innate immune responses against cancer.

About PHST001

PHST001 is an anti-CD24 macrophage checkpoint inhibitor designed to overcome immune suppression in the tumor microenvironment. CD24 is highly expressed in many human cancers and high expression of CD24 is associated with poor prognosis across multiple tumor types. PHST001 is designed to promote macrophage-mediated phagocytosis of cancer cells and initiate a broader immune response. PHST001-101 is an open-label, multicenter Phase 1 study in patients with advanced solid tumors (ClinicalTrials.gov Identifier: NCT06840886). Primary objectives include safety, tolerability, and dose optimization, with secondary objectives evaluating pharmacokinetics and preliminary anti-tumor activity. PHST001 received FDA Fast Track Designation for the treatment of ovarian cancer in June 2025. The phase 1b portion of the study combining PHST001 with chemotherapies is actively recruiting patients.

About Pheast Therapeutics

Pheast is a clinical-stage immuno-oncology company focused on activating the innate immune system to treat cancer. Founded as a spinout from Stanford University and led by scientific experts in innate immunity and cancer immunotherapy, Pheast is developing novel therapies for aggressive and difficult-to-treat cancers. The company is backed by leading life sciences investors, including Catalio Capital Management and ARCH Venture Partners. For more information, visit Pheast.com and connect on LinkedIn.

Investor Contact:
Christina Tartaglia
christina.tartaglia@precisionaq.com

Media Contact:
Colleen Ketchum
colleen.ketchum@precisionaq.com