FDA puts partial hold on trial of vascular agent for AML, MDS


The Food and Drug Administration has placed a partial clinical hold on a phase 1b/2 study of OXi4503, a vascular disrupting agent.

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In this trial (NCT02576301), researchers are evaluating OXi4503 alone and in combination with cytarabine in patients with relapsed/refractory acute myeloid leukemia (AML) and myelodysplastic syndromes (MDS).

The partial clinical hold applies to the 12.2 mg/m2 dose of OXi4503. The FDA is allowing the continued treatment and enrollment of patients using a dose of 9.76 mg/m2. Additional data on patients receiving OXi4503 at 9.76 mg/m2 must be evaluated before dosing at 12.2 mg/m2 can be resumed.

The partial clinical hold is a result of two potential dose-limiting toxicities (DLTs) observed at the 12.2-mg/m2 dose level: hypotension, which occurred shortly after initial treatment with OXi4503, and acute hypoxic respiratory failure, which occurred approximately 2 weeks after receiving OXi4503 and cytarabine.

Both events were deemed “possibly related” to OXi4503, and both patients recovered following treatment.

“Although it is disappointing that we are not currently continuing with the higher dose of OXi4503, we look forward to gathering more safety and efficacy data at the previous dose level, where we observed 2 complete remissions in the 4 patients that we treated,” William D. Schwieterman, MD, chief executive officer of Mateon Therapeutics Inc., the company developing OXi4503, said in a statement.

In preclinical research, OXi4503 demonstrated activity against AML, both when given alone and in combination with bevacizumab. These results were published in Blood in 2010.

In a phase 1 trial (NCT01085656), researchers evaluated OXi4503 in patients with relapsed or refractory AML or MDS. OXi4503 demonstrated preliminary evidence of disease response in heavily pretreated, refractory AML and advanced MDS.

The maximum tolerated dose of OXi4503 was not identified, but adverse events attributable to the drug included hypertension, bone pain, fever, anemia, thrombocytopenia, and coagulopathies.

Results from this study were presented at the 2013 annual meeting of the American Society of Hematology.

In 2015, Mateon Therapeutics initiated the phase 1b/2 study of OXi4503 (NCT02576301) that is now on partial clinical hold.

The phase 1 portion of this study was designed to assess the safety, pharmacokinetics, pharmacodynamics, and preliminary efficacy of single-agent OXi4503 in patients with relapsed/refractory AML and MDS. It is also aimed at determining the safety, pharmacokinetics, and pharmacodynamics of OXi4503 plus intermediate-dose cytarabine.

The goal of the phase 2 portion is to assess the preliminary efficacy of OXi4503 and cytarabine in patients with AML and MDS.

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