Sunesis slumps after pulling plug on leukemia drug vosaroxin in Europe

Sunesis will now focus on BTK inhibitor and would-be Imbruvica rival SNS-062.

Sunesis Pharmaceuticals has been forced to concede defeat in its bid to bring vosaroxin to the E.U. market for acute myeloid leukemia, in a near-carbon copy of what happened with the FDA two years ago.

Sunesis admitted that the EU Committee for Medicinal Products for Human Use (CHMP) had expressed reservations about its data for the drug during meetings and the advisory panel was "likely to formally adopt a negative opinion" on vosaroxin for AML.

In 2015, the company got a similar response form the FDA. After the phase 3 VALOR trial of the drug missed its primary endpoint of improving survival when added to the generic drug cytarabine, Sunesis had tried to argue that it had seen a benefit in a subgroup of patients. The agency was unconvinced, however, advising it not to file for approval without more evidence. Sunesis had been pretty much relying on the same dataset in its discussions with the European Medicines Agency (EMA).

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Sunesis' investors voted with their feet and the company's share price went into sharp decline as the decision all-but destroyed chances of approval for vosaroxin without a second clinical trial. Vosaroxin is a derivative of the antibacterial agent quinolone, and the company had been hoping to position it as a new class of therapy for relapsed or refractory AML.

There's been a chronic lack of new treatments for AML for almost 30 years, although that changed last week with the FDA gave a green light to Novartis' Rydapt (midostaurin).

Sunesis hasn't said it will give up on the program just yet, but will not be investing in an expensive clinical trial for the time being at least. Instead, it hopes to rely on a "modest investment" in investigator-led studies to try to build data for vosaroxin while it turns its attention to other projects—led by BTK inhibitor SNS-062 which is due to start phase 1/2 trials in B-cell cancers later this quarter.

The company's CEO Daniel Swisher said the company will "carefully assess business development alternatives to support the conduct of another pivotal trial to achieve future regulatory approval of vosaroxin."

With no chance of vosaroxin approval any time soon, the South San Francisco biotech is now facing the prospect of having to bring forward an early-stage candidate quickly—into a competitive market.

Since 2013, Johnson & Johnson been selling its BTK inhibitor Imbruvica (ibrutinib)—which is predicted to become the third biggest-selling cancer drug in 2022 with sales of more than $8 billion—since 2013, and other companies including AstraZeneca, Ono/Gilead Sciences and China's BeiGene amongst companies with so-called 'second-generation' BTK inhibitors that claim to offer increased potency and fewer side effects than ibrutinib in clinical testing.

At least Sunesis' cash burn will now reduce dramatically, without costs for commercializing vosaroxin or a second clinical trial anytime soon. The firm's latest annual report indicates it ended 2016 with around $43 million in cash and cash equivalents—which it says is enough to fund "beyond Q1 2018."

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