Seattle Genetics halts late-stage study of leukemia drug

Seattle Genetics Inc said it would halt a late-stage study of its drug to treat a type of leukemia in older patients following a "higher rate" of deaths in patients on the drug compared with those on a placebo.

Shares of the U.S. drug developer fell as much as 11 percent to $57.40 in early trading on Monday, but recouped some losses to be down about 3.7 percent.

The drug, vadastuximab talirine, was being evaluated in the late-stage study, Cascade, to treat a form of blood cancer called acute myeloid leukemia (AML).

Seattle Genetics declined to disclose the number of deaths, but said they were not related to liver toxicity, based on available data.

In December, the U.S. Food and Drug Administration (FDA) had imposed a clinical hold on several early stage studies testing vadastuximab talirine after six AML patients were identified with liver toxicity and four died. The hold was lifted in March.

The discontinuation of Cascade is not related to the clinical hold from December, the company said in an email.

Seattle Genetics also said it would suspend patient enrollment and treatment in all trials involving vadastuximab talirine, including an early-stage study in patients with another form of blood cancer.

The company, which is developing various cancer drugs, said it would consult the FDA regarding future plans for vadastuximab talirine.

At least three analysts cut their revenue estimates for Seattle Genetics following the discontinuation of the trial.

Oppenheimer analyst Leah Rush Cann slashed her estimated 2021 total revenue by 12.5 percent.

But some analysts turned their focus to the company's Adcetris drug ahead of a late-stage study readout expected by the end of the year.

Adcetris is already approved in the United States to treat patients with classical Hodgkin lymphoma who have not realized enough benefits from prior therapies.

The drug, which generated about $71 million in North America sales last year, is also being developed in combination with Bristol-Myers Squibb's immunotherapy, Opdivo, to treat relapsed hodgkin lymphoma (HL).

The trial, involving previously untreated HL patients, could help expand the Adcetris label.

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