FDA Grants Fast Track Status to PHST001 for Ovarian Cancer Treatment

The U.S. Food and Drug Administration (FDA) has granted fast track designation to PHST001 for the single-agent treatment of patients with advanced platinum-resistant ovarian cancer or in combination with chemotherapy in platinum-sensitive ovarian cancer, according to a news release from Pheast Therapeutics.

PHST001 is an experimental antibody therapy that may help the immune system detect and attack solid tumors by targeting the CD24 protein.

“Receiving fast track designation from the FDA reinforces the [possibility] 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,” Dr. Raphaël Rousseau, chief medical officer of Pheast Therapeutics, said in the 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.”

The FDA’s fast track program helps speed the development and review of new therapies for serious conditions with unmet needs. Companies granted fast track status can have more frequent FDA interactions during clinical trials and may qualify for faster approval or priority review if they meet certain criteria.

The multicenter, open-label phase 1 study of PHST001 is enrolling up to 80 patients with advanced relapsed or refractory solid tumors. It aims to evaluate the safety and tolerability of PHST001 and determine the recommended phase 2 dose, with secondary goals to assess pharmacokinetics and early anti-tumor activity.

In Texas, two centers are actively recruiting: MD Anderson Cancer Center in Houston and South Texas Accelerated Research Therapeutics (START) in San Antonio. Additional locations in California, Connecticut, Illinois, Massachusetts, Michigan, North Carolina and Tennessee are to be included in the future of the study.

What is CD24 and PHST001?

CD24 is a protein found on the surface of many cancer cells that helps tumors avoid being destroyed by the immune system. It does this by binding to Siglec-10, a receptor on immune cells called macrophages, which normally would clear away harmful cells. This interaction prevents macrophages from attacking the cancer.

CD24 was found to be an important “checkpoint” in the immune system by Dr. Amira Barkal, founder of Pheast Therapeutics, and her colleagues in Dr. Irving Weissman’s lab at Stanford University.

PHST001 is an investigational antibody designed to block the CD24 checkpoint. By inhibiting CD24, PHST001 helps restore macrophages’ ability to engulf and destroy cancer cells, sparking a stronger immune response. CD24 is found at high levels in several cancers, including ovarian cancer and triple-negative breast cancer, where its presence is linked to worse outcomes. PHST001 is engineered to be a leading treatment in its class, aiming to overcome immune suppression within tumors.

What is Platinum Sensitive Ovarian Cancer

Cancer that responds to treatment with platinum-based drugs, such as cisplatin and carboplatin, is called “platinum sensitive,” according to the National Cancer Institute. Some cancers that return after treatment may also be platinum sensitive — for example, ovarian cancer that comes back 6 or more months after platinum therapy. Platinum-resistant ovarian cancer, however, shows a resistance to platinum-based therapies and may return within 6 months. Knowing if cancer is platinum sensitive helps guide further treatment.

Ovarian cancer develops in the tissues of the ovaries, female reproductive glands that produce eggs. Most ovarian cancers are ovarian epithelial cancers, which start in the surface cells of the ovary, or malignant germ cell tumors, which begin in egg cells. Fallopian tube cancer and primary peritoneal cancer are similar to ovarian epithelial cancer and are treated the same way.

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