REDWOOD CITY, Calif.–Pheast Therapeutics announced the publication of peer-reviewed preclinical research supporting PHST001, its experimental macrophage-directed cancer immunotherapy, in the journal Clinical Cancer Research.
The study identified CD24 as an important “don’t eat me” signal used by cancer cells to evade immune surveillance and found that PHST001 could block that signal and promote the destruction of tumor cells by macrophages.
PHST001 is a high-affinity IgG4 monoclonal antibody designed to target CD24 and disrupt its interaction with Siglec-10. According to the published findings, the treatment increased macrophage phagocytosis, the process through which immune cells engulf and destroy tumor cells.
In preclinical studies, PHST001 demonstrated anti-tumor activity across models of ovarian, breast, endometrial, pancreatic and lung cancers, as well as cholangiocarcinoma. The antibody was active as a standalone treatment and enhanced the effects of chemotherapy, radiotherapy and antibody-drug conjugates, including in treatment-resistant tumor models.
The findings also indicated interactions between macrophages activated by PHST001 and the adaptive immune system, which the company said could contribute to the treatment’s broader anti-tumor effects.
“Cancer cells survive in part by expressing cell surface ‘don’t eat me’ signals that suppress critical immune surveillance functions of the immune system’s macrophages. CD24 is one of the most important of these signals expressed on several types of human cancer cells; this publication shows that blocking it with PHST001 can mobilize macrophages against a broad range of solid tumors,” said Irving Weissman, M.D., Co-founder of Pheast Therapeutics. “This is a significant advance for the field of innate immune therapy against cancer and is critical for the next stages to determine the potential of PHST001 to become an important new cancer treatment.”
PHST001 is currently being evaluated in the Phase 1 PHST001-101 clinical trial involving patients with relapsed or refractory solid tumors. Pheast said the monotherapy dose-escalation portion of the study is nearly complete, while combination cohorts testing PHST001 with chemotherapy are underway.
“The combination benefit outlined in this publication is exactly what we are now testing in patients, where PHST001 has already shown promising early signs of activity,” said Roy Maute, Ph.D., Co-founder and Chief Executive Officer of Pheast. “These peer-reviewed data underpin our conviction in CD24 as a critical target and Pheast’s leadership in macrophage checkpoint immunotherapy.”
The company expects to present initial clinical findings from the trial at an upcoming medical meeting. PHST001 received FDA Fast Track designation for the treatment of ovarian cancer in June 2025.
