After FDA snub, Daiichi's Vanflyta gains US approval and tees up AML clash with Novartis, Astellas

If at first you don’t succeed, try, try again. That’s the lesson Daiichi Sankyo likely took home Friday after scoring a long-awaited U.S. approval for quizartinib—a treatment for acute myeloid leukemia (AML) that’s now set to tangle with drugs from Novartis and Astellas Pharma.

Some four years after quizartinib scored its initial green light in Japan—and suffered a slap-down from drug regulators stateside—the AML medicine has won the FDA’s blessing. It becomes the first FLT3 inhibitor approved across three phases of the common blood cancer.

Now christened Vanflyta, Daiichi’s drug has specifically been approved in tandem with standard induction and consolidation therapies plus as a solo maintenance therapy following consolidation chemo.

The drug—the third from Daiichi’s oncology franchise to score a U.S. nod—is cleared for use in adult patients with newly diagnosed AML with the FLT3-ITD mutation, the company said in a press release. The FLT3 mutation is one of the most common mutations in people with AML, with FLT3-ITD affecting about a quarter of AML patients. 

Alongside Friday’s approval for Vanflyta, the FDA also signed off on a companion diagnostic to detect the relevant mutations in patients with newly diagnosed AML.

Daiichi notes that AML is among the most common forms of leukemia in adults, with an estimated 20,380 new cases expected to be diagnosed in the U.S. this year. What’s more, up to 37% of newly diagnosed patients with AML have an FLT3 gene mutation, some 80% of which are FLT3-ITD mutations. The mutation is understood to drive cancer growth and fuel an increased risk of relapse and is associated with shorter overall survival.

The five-year survival rate for patients with FLT3-ITD AML has been reported at approximately 20%, according to Daiichi.

With the approval in hand, Daiichi says it aims to make Vanflyta available in the U.S. in the coming weeks. Daiichi picked up the therapy way back in 2014 when it snapped up San Diego’s Ambit Biosciences for $410 million. Prior to that acquisition, Ambit had been working with Astellas under a $40 million pact centered on quizartinib and other FLT3 inhibitors.  

The FDA’s approval hinged on results from Daiichi’s QuANTUM-First trial, which showed Vanflyta plus chemotherapy in three phases of treatment—induction, consolidation and maintenance—plus as a maintenance monotherapy, slashed the risk of death by 22% versus standard chemotherapy alone.

Vanflyta carries a boxed warning for QT prolongation, or an extended interval between the heart contracting and relaxing, plus other heart risks. Given the risks the medicine carries, Vanflyta will only be available under certain circumstances through the Vanflyta Risk Evaluation and Mitigation Strategy.

While quizartinib has been approved in Japan since 2019, the drug has had a considerably tougher go of things in the U.S. In fact, the FDA first slapped down the med just three days after it scored its initial Japanese green light four years back.

Things started to look up for Vanflyta in the U.S. after the drug posted positive phase 3 survival data last June. With that trial win in its back pocket, Daiichi prepared regulatory filings around the world.

Matters took a slight turn in late April, when the FDA delayed its decision on quizartinib by three months to July. The regulator wasn’t concerned about the drug’s data; rather, it needed more time to review proposed updates to Daiichi’s safety monitoring program.

But the approval doesn’t necessarily mean Vanflyta will have an easy go in a competitive market. Novartis’ Rydapt and Astella’s Xospata have already beaten Daiichi’s drug to the American market, with both treatments also targeting FLT3 gene mutations.

Daiichi will likely have to depend on its medicine’s green light across three phases of treatment to help separate Vanflyta from the rest of the AML pack.

For all of 2022, Astella’s Xospata brought home (PDF) 46.6 billion Japanese yen (about $330 million). Novartis, for its part, doesn’t include Rydapt sales on its list of reported product revenues, which are capped on the low end by Afinitor/Votubia at around $500 million.