New PET tracer shows promise for guiding pancreatic cancer therapy

A novel PET imaging agent appears promising for selecting patients with pancreatic cancer for targeted radiopharmaceutical therapy, according to recent research. 

The finding comes from a phase I trial of zirconium-89 (Zr-89) NMK89, a radiotracer designed to identify pancreatic tumors eligible for paired therapy with cancer-killing actinium-225 (Ac-225) NMT25, noted lead investigator Delphine Chen, MD, of the University of Washington in Seattle, and colleagues. 

“These findings support NMK89 as a promising companion diagnostic to select patients for MUC5AC-targeted radiopharmaceutical therapy,” the group wrote. The study was presented June 2 at the Society of Nuclear Medicine and Molecular Imaging (SNMMI) annual meeting. 

Pancreatic cancer remains one of the hardest cancers to treat with currently available therapies, and new approaches that pair a diagnostic imaging agent with a matched therapy (theranostics) offer a promising path toward more targeted treatment, the authors explained. NMK89 works by targeting a protein called MUC5AC, which appears on the surface of most pancreatic tumors but is largely absent from healthy tissue, they noted. 

To assess the tracer’s evaluate clinical safety, tolerability, and biodistribution, the investigators recruited 10 patients with biopsy-confirmed pancreatic cancer whose tumors expressed MUC5AC. Nearly all had received at least one cycle of chemotherapy, and two patients had surgical resection of the primary tumor prior to starting chemotherapy.  

All 10 received a single injection of NMK89 and underwent PET/CT scans at 1, 24, 72, and 168 hours later, while blood and urine were collected at each imaging time-point for both safety and pharmacokinetic evaluations.

Transaxial Zr-89 NMK89 PET/CT images 1, 24, 72, and 168 hours after injection showing increasing uptake in pancreatic tail adenocarcinoma. Maximum standard uptake value (SUV) in the pancreatic mass is 14 at 168 hours post-injection (crosshairs). PET SUV scale used for windowing was 0 to 10.Delphine Chen, MD, and SNMMIAccording to the results, no serious adverse events related to NMK89 administration were observed. Activity was seen in the blood pool, liver, and kidneys on early imaging at 1 hour after injection that cleared over time. Approximately 20% to 25% of the early blood activity remained in the blood at 168 hours post-injection, while activity in all organs was lower than blood pool activity at all time-points for all subjects. 

PET imaging showed uptake in nearly all liver metastases except in one patient in whom only a few liver metastases showed a low level of uptake. In the eight patients who had not had primary tumor resection, uptake in the primary tumor was generally low compared to metastatic lesions, the researchers reported. 

“NMK89 may be effective at targeting MUC5AC-expressing pancreatic tumors with limited normal-organ uptake,” the group wrote.  

Ultimately, the study offers early evidence that patients whose tumors take up NMK89 on PET/CT imaging could then be considered candidates for treatment with paired Ac-225 NMT25, also under development, the researchers noted. 

“Formal dosimetry and pharmacokinetic analyses to confirm these preliminary results are ongoing,” the group concluded. 

Check out AuntMinnie’s full coverage of SNMMI 2026 on our recent ShowCast.