The US Food and Drug Administration (FDA) has placed a partial clinical hold on Kura Oncology’s Phase Ib KOMET-001 clinical trial of its drug candidate, KO-539, in relapsed or refractory acute myeloid leukaemia (AML) patients.

KO-539 is a potent and selective inhibitor of menin.

The FDA’s partial clinical hold comes in response to the latest report submitted by the company of a Grade 5 serious adverse event of patient death probably connected to differentiation syndrome.

This syndrome is a recognised side effect linked to differentiating agents in the AML treatment.

Kura noted that the subjects currently enrolled in the trial could continue to take KO-539 but no new subjects will be enrolled until the FDA lifts the partial clinical hold.

The company is holding talks with FDA as well as trial investigators to address the clinical hold soon.

Kura Oncology president and CEO Troy Wilson said: “Differentiation syndrome is known to be an on-target effect associated with therapeutic agents that induce differentiation, and we want to ensure physicians are fully informed and prepared to address these events if they occur.

“Based on the totality of preclinical and clinical data, we continue to believe that KO-539 has the potential to address the significant unmet medical need of AML patients, including those with NPM1 mutations and KMT2A rearrangements.”

The company will temporarily delay the guidance on the conclusion on patient enrolment in the trial and selection of the recommended dose of the drug for the Phase II trial.

In addition to KO-539, Kura has several small molecule therapy candidates in its pipeline. Its tipifarnib, an orally bioavailable inhibitor of farnesyl transferase, is currently being analysed in a trial in individuals with HRAS-mutant head and neck squamous cell cancer.

Another farnesyl transferase inhibitor, KO-2806, is being developed for oncology indications.

In August this year, the FDA placed a clinical hold on Aprea Therapeutics’ trial of eprenetapopt to treat lymphoid malignancies.