FDA halts phase 1b Kura Oncology trial in acute myeloid leukemia following patient death

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The cause of death in Kura Oncology's early-stage cancer trial, differentiation syndrome, is seen in some treatments for acute myeloid leukemia (AML) and was included in the black box warning of an AML drug approved by the FDA in 2018. (FDA)

The FDA sidelined an early-stage cancer trial from Kura Oncology after a patient died due to a serious adverse event related to the oral treatment's mechanism of action. 

The partial clinical hold means no additional patients in the acute myeloid leukemia trial will be enrolled until the FDA gives the green light. The regulator's information request is "not complicated," and the hold should be "relatively short," Kura's management said in a conference call Wednesday morning. 

Kura's stock was down 22% to $12.95 a share as of 9:30 a.m. ET.

The patient's death in the phase 1b trial is potentially associated with differentiation syndrome, the biotech said. The adverse event is a drug reaction caused by differentiating agents in certain treatments for AML and occurs in up to one-quarter of patients treated with such agents. The syndrome is marked by unexplained fever, acute kidney injury, hypotension, weight gain and other harmful results.

The side effect is included in a black box warning for Agios Pharmaceuticals' approved AML drug Tibsovo, which was given the go-ahead in July 2018. The syndrome also has a 1% incidence with Astellas' AML treatment Xospata.

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Kura's management described the syndrome as "part and parcel of this mechanism of action," and occurrence of the syndrome "shouldn't surprise anyone," leadership said in a conference call discussing the news.

The biotech and its site investigators already had a mitigation strategy in place for the syndrome, and there were "relatively few" other patients who experienced the syndrome, but those cases were "manageable and resolved with steroids," management said. 

The patient who died had failed four prior lines of therapy. The patient started on the 200-mg dose, management said. 

The FDA has asked for "three key pieces of information," including a review of the safety database, an articulation of the mitigation plan for the deadly syndrome and rationale for the dose selection of 200 mg and 600 mg, management said. 

"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," said Troy Wilson, Ph.D., Kura's president and CEO, in a statement.

Management reassured analysts on the call that all physicians involved in the study "are doing proper surveillance."