Shares of Northfield Laboratories Inc. lost more than half their value after the company said that more deaths occurred among patients given its synthetic blood product than among those not receiving the treatment in a study.
There were 46 deaths among 349 patients receiving the product, called PolyHeme, compared with 35 among 363 people getting a standard treatment, Northfield said Tuesday. The company said "protocol violations" and discrepancies related to two patient deaths prevented a complete analysis of the results.
Northfield's shares fell $5.84, or 51%, to $5.58 in after-hours trading. Earlier, its shares dropped $2.90, or 20%, to $11.42 on the company's announcement that it would hold a conference call to discuss the research findings.
The setback is the second this month for makers of artificial blood.