Seattle Genetics to Resume Leukemia Drug Trials After FDA Lifts Hold

Xconomy Seattle — 

An experimental leukemia drug from Seattle Genetics can resume clinical testing, work that had ground to a halt three months ago following the deaths of four patients.

The FDA in December placed clinical holds or partial holds on three early stage trials SeaGen (NASDAQ: SGEN) has been running to study the leukemia drug vadastuximab. The holds suspended the three trials until SeaGen could evaluate the risk of liver damage to patients taking the drug. Bothell, WA-based SeaGen said Monday that testing could resume after an analysis by the company, the FDA, and an independent committee of clinical experts “resolved” the clinical holds with changes to the clinical trial to “further enhance patient safety.” SeaGen’s shares dipped 1 percent to $68.18 Monday morning.

Leukemias are cancers that occur in the blood or bone marrow. The SeaGen drug is being tested as a potential treatment for acute myeloid leukemia (AML), a form of the cancer in which stem cells from bone marrow do not become healthy white blood cells. The SeaGen drug is what’s called an antibody drug conjugate, or ADC. These drugs link powerful cancer-killing chemicals to antibodies, an approach meant to offer a more targeted hit to cancer cells and spare healthy tissue. SeaGen has already won FDA approval of one ADC, Brentuximab vedotin (Adcetris), for Hodgkin’s lymphoma.

When the FDA halted the SeaGen trials in December, the company cited liver damage that appeared to be linked to four patients deaths in the trials. The company decided to search for instances of veno-occlusive disease, when blockages occur in small veins that transport blood to through the liver. In a research note sent this morning, Leerink Partners analyst Michael Schmidt said SeaGen CEO Clay Siegall told the firm that the rate of veno-occlusive disease in the trials is in line with the rate of the disease historically seen in similar patients. The company has since established an independent data monitoring committee to avoid a misdiagnosis of the liver condition, which occurred in a few instances in the SeaGen trials, Schmidt wrote.

SeaGen now plans to resume two Phase 1 trials in adults with AML and also start a randomized Phase 2 study evaluating the drug in combination with chemotherapy, the standard of care. The company said it will not resume the Phase 1/2 trial of its drug in AML patients before and after receiving stem cell transplants “given the challenges of developing therapies in this specific setting.”

Jonathan Drachman, SeaGen’s chief medical officer, in a statement that SeaGen will continue a Phase 3 clinical trial evaluating the drug in older AML patients, as well as a Phase 1/2 trial in myelodysplastic syndrome, a disorder in which bone marrow doesn’t make enough healthy red blood cells.

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