Shares of biopharmaceutical firm

NeoRx

(NERX)

plummeted after the company suspended enrollment and treatment under its phase III clinical trial in patients with multiple myeloma and other skeletal targeted radiotherapy studies.

The company's shares were recently off $8.19, or 46.9%, to $9.25 in

Nasdaq

trading.

The Seattle company said it was suspending its trials because four patients from an earlier trial developed a serious delayed side effect, with symptoms that include abnormal clotting of blood in small blood vessels.

The company is awaiting a resolution with the

Food and Drug Administration

.