Experimental drug for rare leukemia wins FDA orphan drug status

The U.S. Food and Drug Administration (FDA) has granted orphan drug designation to the investigational therapy onvansertib as a potential treatment for chronic myelomonocytic leukemia (CMML) a rare form of blood cancer.

The FDA gives this designation to experimental medications intended to treat rare disorders, defined as conditions affecting fewer than 200,000 people in the U.S. This designation aims to provide additional incentives to pharmaceutical companies investing in the development of treatments for rare diseases. The status gives onvansertib’s developer, Cardiff Oncology, access to several perks, notably a guaranteed seven years of market exclusivity if the therapy ultimately wins FDA approval for CMML.

“We believe this designation highlights the broader clinical opportunity for onvansertib as a monotherapy [used on its own] as we continue advancing therapies for patients across cancers where new therapeutic approaches are urgently needed,” Mani Mohindru, PhD, president and CEO of Cardiff Oncology, said in a company press release.

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Limited treatment options

Onvansertib is an oral medication that blocks the activity of PLK1, a protein that helps regulate cell growth. In many types of cancer, uncontrolled PLK1 activation helps to drive the abnormal growth of cancer cells; by blocking this protein, onvansertib may help to limit cancer growth. Cardiff is developing the therapy as a potential treatment for several different types of cancer.

CMML is characterized by features that combine myelodysplastic syndromes (when the bone marrow doesn’t produce enough new blood cells) and myeloproliferative neoplasms (which involve the uncontrolled growth of blood cells). CMML usually affects older adults, and the cancer tends to be aggressive and associated with poor outcomes.

“CMML remains a difficult-to-treat hematologic malignancy with limited treatment options for patients,” Mohindru said, adding that the FDA’s decision to grant the treatment orphan drug status “further validates the therapeutic potential of PLK1 inhibition in cancers with significant unmet need and adds to the growing body of evidence supporting this mechanism across both solid tumors and hematologic malignancies.”

Mayo Clinic is sponsoring a Phase 1 study (NCT05549661) testing onvansertib in people with hard-to-treat CMML and related blood cancers. All participants in the trial will receive the experimental treatment, with the main aim of evaluating safety outcomes over up to four years of follow-up. The study aims to enroll about two dozen adults with CMML that has not been adequately managed following at least four prior lines of standard blood cancer treatment. Enrollment is ongoing at Mayo Clinic in Rochester, Minnesota.