With New PET Probe, Researchers Image Fibrosis of the Lungs

The MGH Martinos Center’s Pauline Désogère and colleagues have described a new positron emission tomography (PET) probe that can help to advance noninvasive diagnosis of pulmonary fibrosis. Reported in a Science Translational Medicine paper published online today, the probe enables detection and staging of the disease by imaging Type I collagen, a major component of fibrosis.

In current practice, high-resolution computed tomography is commonly used for diagnosis of the disease, but the technique often cannot distinguish between fibrosis and other pathological processes in the lung. It can precisely diagnose only 50 percent of patients, and in many cases is not able to predict prognosis or show response to therapies. This leaves surgical biopsy as the only available method for definitive diagnosis, and biopsy can be particularly hazardous to the patients in question.

Désogère sought to change this.

An Instructor in the Center working in the laboratory of Peter Caravan, Désogère developed the new probe by modifying a collagen-specific peptide to bind with the radioisotope Gallium-68, commonly written as 68Ga. Interest in 68Ga probes has increased dramatically over the past year, especially as the short half-life of the radioisotope allows relatively easy production and leads to low radiation exposure in subjects. With an eye toward clinical translation with PET, Désogère, Caravan and colleagues tested the collagen-targeted probe – 68Ga-CBP8 – in a mouse model of pulmonary fibrosis and found high specificity for the disease. In another model, they showed that the probe could also be used to monitor response to treatment. Finally, experiments using ex vivo samples of fibrotic human lung tissue suggested that the probe could differentiate between stable disease and progressive fibrosis – information that can be important to treatment planning.

The introduction of the probe is timely. The US Food and Drug Administration recently approved two drugs that slow the progression of idiopathic pulmonary fibrosis – a form of the disease that affects mostly older adults – and of associated loss of function in the lungs. Investigators are also exploring the potential of the drugs for other forms of the disease. With these new possibilities for treatment, early detection of the disease, accurate prognosis and the ability to monitor treatment response become ever more important. The 68Ga-CBP8 probe could enable these, reliably and noninvasively, and thus could benefit a wide range of pulmonary fibrosis patients.

Gary Boas