Technetium (99mTc) fanolesomab (trade name NeutroSpec, manufactured by Palatin Technologies) is a mouse monoclonal antibody formerly used to aid in the diagnosis of appendicitis.

NeutroSpec was approved by the U.S. Food and Drug Administration (FDA) in June 2004 for imaging of patients with symptoms of appendicitis.

It consisted of an intact murine (mouse) IgM monoclonal antibody against human CD15, labeled with technetium-99m so as to be visible on a gamma camera image.

These events occurred within minutes of administration of NeutroSpec and included shortness of breath, low blood pressure, and cardiopulmonary arrest.

A review of all post-marketing reports showed an additional 46 patients who experienced adverse events that were similar but less severe.