FDA Grants Fast Track Designation to PHST001 for Ovarian Cancer

FDA

The FDA has granted fast track designation to the investigational anti-CD24 monoclonal antibody PHST001 for the treatment of patients with advanced platinum-resistant ovarian cancer, and in combination with chemotherapy for those with platinum-sensitive ovarian cancer.1

PHST001 is intended to enhance innate immune recognition and antitumor activity in patients with solid tumors. CD24 is a cell surface protein that engages with the inhibitory receptor Siglec-10 expressed on macrophages to drive tumor immune evasion. CD24 is expressed across a variety of tumor types, including ovarian cancer and triple-negative breast cancer. Notably, high expression of CD24 is also a negative prognostic factor is several tumor types.

The agent is currently being investigated in an phase 1 trial (NCT06840886), which is assessing the safety, tolerability, and preliminary efficacy of the agent in patients with advanced relapsed/refractory solid tumors.

“Receiving fast track designation from the FDA reinforces the promise of CD24 as a next-generation immuno-oncology target and highlights the potential of PHST001 to address a critical unmet need in the treatment of ovarian cancer,” Raphaël Rousseau, MD, PhD, chief medical officer of Pheast Therapeutics, stated in a news release. “We are committed to advancing PHST001 through the clinic and accelerating its development for cancer patients in urgent need of more effective treatments.”

Phase 1 Trial Overview

The multicenter, open-label study is enrolling patients at least 18 years of age with histologically or cytologically confirmed advanced solid tumors whose disease is relapsed from or refractory to all locally available standard therapies.2 Patients are required to have adequate hepatic, renal, and bone marrow function.

The study is excluding patients with a history of a previous additional malignancy, unless that patient underwent potentially curative treatment with no evidence of the malignancy for 5 years. Patients with active known central nervous system (CNS) metastases and/or carcinomatous meningitis are not allowed to enroll; however, patients with previously treated CNS metastases are permitted if they are radiologically stable, clinically stable, and without requirement of steroid treatment for at least 14 days prior to first study treatment. Other key exclusion criteria comprise prior autologous or allogeneic hematopoietic stem cell transplant; prior solid organ transplant’ or previous treatment with another agent targeting CD24.

During the dose-escalation portion of the study, patients are receiving PHST001 at 1 of 7 dose levels. In all cohorts, the agent is being administered once every 3 weeks, on day 1 of each 21-day cycle. Investigators intend to enroll approximately 40 to 80 patients in the first portion of the study to be treated across the 7 dose levels. In the second part of the trial, additional expansion cohorts will be opened.

Safety and the incidence of dose-limiting toxicities are the trial’s primary end points. Secondary end points included preliminary antitumor activity per RECIST 1.1 criteria, pharmacokinetics, and pharmacodynamics.

The FDA’s fast track program facilitates development of novel therapies for serious conditions and address significant unmet medical needs, and it can also expedite the review process by the regulatory agency.

References

1. Pheast Therapeutics receives FDA fast track designation for PHST001 for the treatment of ovarian cancer. News release. Pheast Therapeutics. June 3, 2025. Accessed June 6, 2025. https://www.pheast.com/pheast-therapeutics-receives-fda-fast-track-designation-for-phst001-for-the-treatment-of-ovarian-cancer/
2. A study of PHST001 in advanced solid tumors. ClinicalTrials.gov. Updated April 29, 2025. Accessed June 6, 2025. https://clinicaltrials.gov/study/NCT06840886