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The FDA has granted orphan drug designation to onvansertib, an oral PLK1 inhibitor, for chronic myelomonocytic leukemia (CMML) — a rare and hard-to-treat blood cancer. The designation is backed by early phase 1 data showing clinical benefit in roughly 40% of relapsed/refractory patients. It adds momentum to Cardiff Oncology's growing pipeline across both blood cancers and solid tumors.
The FDA has granted orphan drug designation to onvansertib for chronic myelomonocytic leukemia (CMML), a rare myeloid malignancy with limited treatment options. The oral drug works by selectively inhibiting PLK1, a mitotic kinase that is overexpressed in proliferative CMML — particularly in tumors harboring RAS-pathway mutations.
The designation is supported by early data from a Mayo Clinic–sponsored phase 1 trial evaluating onvansertib monotherapy in relapsed/refractory CMML. Among nine patients enrolled, the drug was generally well tolerated and showed meaningful early activity, with one patient achieving enough response to proceed to a stem cell transplant.
By the Numbers:
Why it matters: CMML is a rare and aggressive blood cancer with very few approved therapies, making new treatment approaches urgently needed. Orphan drug designation comes with regulatory perks — including tax credits and market exclusivity — that can accelerate development. Onvansertib's PLK1-targeting mechanism also has potential implications beyond CMML, with trials ongoing in colorectal, pancreatic, lung, and breast cancers.
