LeukoStrat CDx FLT3 Mutation Assay Is Approved to Help Identify Patients With AML Who Are Eligible for Quizartinib

The FDA has approved the LeukoStrat CDx FLT3 Mutation Assay to help identify patients who are eligible to receive treatment with quizartinib (Vanflyta). Quizartinib was recently approved for patients with newly diagnosed FLT3-ITD positive acute myeloid leukemia (AML).¹

That assay is a polymerase chain reaction-based in vitro diagnostic that identifies alterations occurring in the FLT3 gene. The diagnostic assesses genomic DNA samples removed from mononuclear cells. In patients with AML, these cells are obtained from peripheral blood or bone marrow aspirates. Specifically, the assay is engineered to identify internal tandem duplication (ITD) and tyrosine kinase domain (TKD) mutations D835 and I836.

The LeukoStrat CDx FLT3 Mutation Assay is also approved to help identify patients who are eligible to receive midostaurin (Rydapt) and gilteritinib (Xospata).

“FDA approval of the LeukoStrat CDx FLT3 Mutation Assay as a companion diagnostic to [quizartinib] is a significant milestone for patients with newly diagnosed FLT3-ITD–positive AML,” Jeffrey Miller, chief strategy officer, chief executive officer, and founder of Invivoscribe, stated in a news release.¹ “Timely and accurate testing for FLT3-ITD mutations in newly diagnosed patients is critical to identify those who may be eligible for treatment with [quizartinib], and we are happy to collaborate with Daiichi Sankyo to help bring this important new therapy to patients.”

On July 20, 2023, the FDA approved quizartinib, in combination with standard cytarabine and anthracycline induction, and cytarabine consolidation, and as maintenance monotherapy following consolidation chemotherapy, to treat patients with newly diagnoses AML that is FLT3-ITD positive, as detected by an FDA-approved test.²

Findings from the phase 3 QuANTUM-First trial (NCT02668653) support the regulatory decision. Published data demonstrated that the combination elicited a statistically significant and clinically meaningful improvement in overall survival (OS) vs chemotherapy plus placebo (HR, 0.78; 95% CI, 0.62-0.98; 2-sided P = .0324).³ At a 31.9-month median follow-up, the median OS in the experimental arm was 31.9 months (95% CI, 2.0-not estimable [NE]) vs 15.1 months (95% CI, 13.2-26.2) in the control arm.

Quizartinib is a tablet which is available in 2 different forms and strengths: 17.7 mg and 26.5 mg. Patients should take quizartinib once daily, with or without food. They should take the medicine at approximately the same time every day.⁴

Of note, the quizartinib comes with boxed warnings for cardiac complications. As such, the label advises provider to periodically perform electrocardiograms and to monitor for hypokalemia or hypomagnesemia, and correct deficiencies. If a patient had severe hypokalemia, severe hypomagnesemia, or long QT syndrome, they should not receive this treatment. They also should not receive quizartinib if their QTcF surpasses 450 ms.⁴

Because of the risk of QT prolongation, torsados de pointes, and cardiac arrest, quizartinib only is available through the Vanflyta Risk Evaluation and Mitigation Strategy (REMS). Patients will receive a patient wallet card outlining the signs and symptoms of potential treatment-related cardiac complications. It is important that patients are taught to always keep this on them and to show it to all their health care providers.⁴

References

1. Invivoscribe announces FDA approval of the LeukoStrat® CDx FLT3 mutation assay to select patients with FLT3-ITD positive AML for treatment with Vanflyta. News release. Invivoscribe. July 21, 2023. Accessed July 24, 2023. https://invivoscribe.com/invivoscribe-announces-fda-approval-of-the-leukostrat-cdx-flt3-mutation-assay-to-select-patients-with-flt3-itd-positive-aml-for-treatment-with-vanflyta/
2. FDA approves quizartinib for newly diagnosed acute myeloid leukemia. News release. FDA. July 20, 2023. Accessed July 24, 2023. https://www.fda.gov/drugs/drug-approvals-and-databases/fda-approves-quizartinib-newly-diagnosed-acute-myeloid-leukemia
3. Erba HP, Montesinos P, Kim HJ, et al. Quizartinib plus chemotherapy in newly diagnosed patients with FLT3-internal-tandem-duplication-positive acute myeloid leukaemia (QuANTUM-First): a randomised, double-blind, placebo-controlled, phase 3 trial. Lancet. 2023;401(10388):1571-1583. doi:10.1016/S0140-6736(23)00464-6
4. Vanflyta. Prescribing information. Daiichi Sankyo Company, Ltd; 2023. Accessed July 25, 2023. https://www.accessdata.fda.gov/drugsatfda_docs/label/2023/216993s000lbl.pdf