On an acute myeloid leukemia (AML) roll, the FDA has green-lighted Astellas’ Xospata, also known as gilteritinib. For Astellas, it marks the first step toward challenging Novartis’ Rydapt and likely just a slim head start against Daiichi Sankyo.

Xospata’s nod makes it the first monotherapy approved for AML patients with either one of two forms of FLT3 mutation—either FLT3 internal tandem duplication (ITD) or tyrosine kinase domain (TKD)—who’ve relapsed or are resistant to standard chemotherapy. It is also the first blood cancer nod for Astellas in the U.S.

Astellas is pricing the drug at the wholesale acquisition price of $22,500 for a 30-day course of treatment, "in line with other recently launched branded AML treatments," and will make the drug available in the following week, a company spokesperson told FiercePharma.

The FLT3 mutation is expressed in about 30% of AML patients, and it's associated with worse prognosis, including higher relapse rate, faster disease progression and shorter overall survival, according to Richard Pazdur, M.D., acting director of the oncology office within FDA’s Center for Drug Evaluation and Research (CDER).

"The approval of Xospata is also a proud, landmark moment for our oncology program and marks the first approval of a medicine that will be the cornerstone of our new presence in blood cancers," Astellas’ oncology development head, Steven Benner, M.D., said in a statement.

Xospata might not be alone in the FLT3-mutated relapsed/refractory setting long, though. Fellow Japanese drugmaker Daiichi Sankyo’s FLT3 inhibitor, quizartinib, just won an FDA priority review in FLT3-ITD. Affecting around 25% of AML patients, the ITD form is much more common than the TKD mutation. The agency has set a decision date for May 25, 2019.

Xospata’s approval, granted also under FDA’s priority review pathway, is based on a phase 3 study of 138 patients. In that study, Xospata achieved complete remission or complete remission with partial hematologic recovery in 21% of patients, with a median duration of 4.6 months. Among the 106 patients who required red blood or platelet transfusions at the beginning, 31% became independent of transfusions for at least 56 days.

As Xospata and potentially quizartinib square off in the second-line setting, they’re both eyeing newly diagnosed patients—a market currently dominated by Novartis’ Rydapt.

Rydapt last April became the first FDA-approved targeted therapy to treat new patients with FLT3-mutated AML. However, it must be used alongside chemo. Credit Suisse analysts at the time predicted the drug could reach $260 million in sales by 2019.

A phase 2/3 study testing Xospata as monotherapy and in combination with chemotherapy Vidaza in the first-line setting is expected to read out in 2021, whereas a phase 3 studying a quizartinib-chemo combination will report in late 2020.

The Xospata nod followed two other FDA approvals in AML the past few days. As Pfizer bagged an approval for new drug Daurismo in combination with chemo to treat some newly diagnosed patients, AbbVie and Roche’s Venclexta was conditionally cleared to be used in the exact same condition.

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