New whole-body PET probe ferrets out hidden blood clots

A preclinical trial of a novel radiopharmaceutical has shown a single intravenous injection of the probe, when used with whole-body PET, is capable of flagging blood clots wherever in the body they travel and hide.

The new probe, 64Cu-FBP8, was developed at Massachusetts General Hospital (MGH). The researchers behind the work detail their development in the October edition of Arteriosclerosis, Thrombosis and Vascular Biology.

The probe appears able to distinguish older clots from those recently formed, which can be useful in predicting whether a particular clot is responsible for a stroke or pulmonary embolism.

The probe may also aid in uncovering a clot’s composition, providing physicians with a sense of how well the clot will respond to drugs aimed at dissolving it.  

Led by Peter Caravan, PhD, co-director of the Institute for Innovation in Imaging at MGH, the research team induced clot formation in the carotid arteries and femoral veins of a group of rats.

After injecting the probe, they conducted whole-body imaging studies one, three or seven days after clot formation. Team members reading the images were not informed of the exact sites of clot induction, yet they correctly identified the sites 97 percent of the time.

A news release from MGH notes that Caravan and colleagues have developed several PET imaging agents that target the protein fibrin, which is generated as part of the process of clot formation. MGH says 64Cu-FBP8 is the most promising.

A clot causing a stroke can form in the arteries of the neck, from the aorta in the chest, from within the heart or from veins deep within the legs, Caravan points out.

“[K]nowing if any clot remains at those locations is important because it indicates a higher risk of a second stroke,” he adds. “The patient may be treated differently if that parent clot is still present than if no clot remains.”

The lead author of the study report, Francesco Blasi, PharmD, PhD, was a research fellow at the Martinos Center for Biomedical Imaging at MGH and is now at the University of Torino in Italy.

Caravan and his colleagues at MGH say they will soon start testing 64Cu-FBP8 in human volunteers to learn how the probe disseminates through the body and to see how long it lingers after injection.  

A company co-founded by Caravan has received patent rights for the fibrin-binding peptide used in 64Cu-FBP8.