FDA Approves Companion Diagnostic for Quizartinib in FLT3-ITD+ AML

The FDA has approved the LeukoStrat CDx FLT3 Mutation Assay for use as a companion diagnostic to select patients with FLT3-ITD–positive acute myeloid leukemia who may be eligible to receive treatment with quizartinib (Vanflyta).¹

The LeukoStrat CDx FLT3 Mutation Assay is a PCR-based in vitro diagnostic test designed to detect ITD and TKD FLT3 D835 and I836 mutations via genomic DNA from peripheral blood or bone marrow aspirates of patients diagnosed with AML.

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, for the treatment of adult patients with newly diagnosed AML that is FLT3-ITD positive, as detected by an FDA-approved test.²

The approval was supported by data from the phase 3 QuANTUM-First trial (NCT02668653), which showed that treatment with the quizartinib regimen led to 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 median follow-up of 39.2 months (interquartile range, 31.9-45.8), patients in the quizartinib arm experienced a median OS of 31.9 months (95% CI, 2.0-not estimable [NE]) vs 15.1 months (95% CI, 13.2-26.2) for those in the placebo arm.

“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.”

QuANTUM-First was a randomized, double-blind, placebo-controlled trial that enrolled 539 patients with newly diagnosed, FLT3-ITD–positive AML, defined as a FLT3-ITD allelic frequency of at least 3%.⁴ The LeukoStrat CDx FLT3 Mutation Assay retrospectively verified FLT3-ITD status after another clinical trial assay was used prospectively for enrollment.²

Investigators randomly assigned patients in a 1:1 fashion to receive quizartinib or placebo in combination with induction and consolidation therapy, then as maintenance monotherapy. Randomization did not occur again at the initiation of post-consolidation therapy. In patients who underwent hematopoietic stem cell transplantation following consolidation, maintenance therapy was given after recovery from transplant.

Additional data showed that patients treated with quizartinib achieved a complete response (CR) rate of 55% (95% CI, 48.7%-60.9%) vs 55% (95% CI, 49.2%-61.4%) for those given placebo. The median duration of CR was 38.6 months (95% CI, 21.9-NE) in the experimental arm vs 12.4 months (95% CI, 8.8-22.7) in the control arm.²

The most common grade 3 or higher treatment-emergent adverse effects (TEAEs) reported in at least 10% of patients enrolled in QuANTUM-First included febrile neutropenia (43.4% and 41.0% in the quizartinib and placebo arms, respectively), neutropenia (18.1% and 8.6%), hypokalemia (18.9% and 16.4%), and pneumonia (11.7% and 12.7%).⁵

Rates of TEAEs associated with fatal outcomes were 11.3% for quizartinib vs 9.7% for chemotherapy alone, and these deaths were mainly due to infections.

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. Quizartinib with standard of care chemotherapy and as continuation therapy in patients with newly diagnosed FLT3-ITD (+) acute myeloid leukemia (AML) (QuANTUM-First). ClinicalTrials.gov. Updated December 29, 2022. Accessed July 24, 2023. https://clinicaltrials.gov/ct2/show/NCT02668653
5. Erba H, Montesinos P, Vrhovac R, et al. Quizartinib prolongs survival vs placebo plus intensive induction and consolidation therapy followed by single-agent continuation in patients aged 18-75 years with newly diagnosed FLT3-ITD+ AML. Presented at: 2022 EHA Congress; June 9-12, 2022; Vienna, Austria. Abstract S100.