SNMMI 2026
SNMMI 2026: Molecular imaging may find lung inflammation missed on CT
Clinical takeaway: A molecular imaging tracer may eventually help distinguish inflammatory from fibrotic interstitial lung disease, guiding the choice between immunosuppressants and antifibrotics.
Treating interstitial lung disease (ILD) hinges on a distinction current imaging cannot make. Inflammation may respond to immunosuppression, while established fibrosis calls for antifibrotics, yet high-resolution CT maps structural scarring without reliably showing active inflammation.
Confirming inflammation has no reliable noninvasive test, so clinicians often infer it from CT pattern, disease subtype, and clinical course. A noninvasive way to see it would help match patients to the right therapy.
Lungs affected by ILD took up a molecular tracer that healthy lungs largely didn't, an early signal that imaging might fill that gap. The agent, 99mTc-maraciclatide, binds a marker of the new blood vessel growth that accompanies inflammation known as αvβ3 integrin. Healthy controls showed minimal lung uptake, while both disease groups showed distinct uptake.
The clearest result was in fibrotic hypersensitivity pneumonitis, a subtype where inflammation is expected. Mean lung uptake there was significantly higher than in controls (1.2 vs. 0.75, p=0.02). Idiopathic pulmonary fibrosis, a predominantly fibrotic process with little active inflammation, sat in between and didn't reach significance (0.95, p=0.18), a pattern the authors called biologically plausible.
A target-to-background ratio meant to sharpen the contrast was numerically higher in both disease groups but not statistically significant, so the tracer separated disease from health more clearly than it separated inflammation from fibrosis.
This small phase 2 study enrolled 15 participants, five each with idiopathic pulmonary fibrosis, fibrotic hypersensitivity pneumonitis, and age- and sex-matched healthy controls. Each received 740 MBq of 99mTc-maraciclatide intravenously, followed by SPECT/CT two hours later, with images read by nuclear medicine physicians and thoracic radiologists. The data are from a conference abstract and haven't been peer-reviewed.
If validated, the use case is selection: identifying patients whose disease is still inflammatory and potentially treatable with immunosuppression, versus those with fixed fibrosis better served by antifibrotics. The authors also see a possible role in screening and monitoring patients with rheumatoid arthritis at risk for ILD.
A phase 3 trial would be the next test. With FDA Fast Track designation in hand, the authors estimate the agent could reach patients within two years of starting that trial.
"While current imaging techniques can provide a structural view of fibrosis in the lungs, there is no reliable, non-invasive way to identify inflammation," said Druin Burch, a consultant physician at John Radcliffe Hospital in Oxford, UK.
Source: Burch D. SNMMI 2026 Annual Meeting. Abstract 261910. Imaging lung inflammation in interstitial lung disease with 99mTc-maraciclatide: a therapy selection tool