SeaGen Ends One Leukemia Drug Trial, Stops Enrolling Three Others

Xconomy Seattle — 

Seattle Genetics is ending a Phase 3 clinical trial of its leukemia drug after a review showed more deaths in patients treated with the drug compared to the control group, the company announced this morning.

Bothell, WA-based Seattle Genetics (NASDAQ: SGEN) says the decision to end the trial follows a discussion with the independent data monitoring committee and a review of unblinded clinical trial data. That review found showed higher death rates, including fatal infections, in the group of patients treated with its drug vadastuximab talirine, SeaGen says. In addition to ending that trial, SeaGen will also stop enrolling patients in three other trials of the drug.

The news delivered a blow to SeaGen’s stock price, which dropped more than 12 percent to $56.77 early Monday.

SeaGen was studying vadastuximab talirine as a potential treatment for acute myeloid leukemia (AML), a form of the blood cancer in which stem cells from bone marrow fail to mature into healthy white blood cells and instead build up in the body. The trial was testing the SeaGen drug in combination with chemotherapy compared to chemotherapy alone in adult patients newly diagnosed with AML.

The SeaGen drug is one of the company’s antibody drug conjugates (ADC), a type of cancer therapy that links powerful anti-cancer compounds to targeting antibodies to deliver a precise strike to cancer cells. SeaGen has already received FDA approval for one such drug, brentuximab vedotin (Adcetris) for Hodgkin’s lymphoma. Though ADCs’ targeted approach is meant to spare healthy cells, other efforts to develop ADCs have been stymied by the effects that the therapy’s powerful anti-cancer toxins have on healthy tissue.

So far, the data in the AML trial do not show safety issues involving liver toxicity, SeaGen says. Liver damage was among the concerns raised by the FDA regarding the deaths of four patients in earlier-stage clinical trials testing the drug as a single therapy in patients who received stem cell transplants before or after the treatment. Those deaths led the FDA to place complete or partial holds on three vadastuximab talirine trials last December. In March, the regulator cleared SeaGen to resume those trials after making changes to improve patient safety.

Besides AML, SeaGen was also studying its drug in patients who have myelodysplastic syndrome, a disorder in which bone marrow does not make enough healthy blood cells. Monday’s announcement also stops enrollment in that Phase 1/2 trial.

SeaGen says it plans to review the data from the AML trial and discuss with the FDA the future plans for its drug.

Image of human cells with acute myeloid leukemia by the National Cancer Institute.