Four times longer half-life with Sc-44 DOTA oncologic PET agent

A longer lasting alternative to gadolinium-68 for PET cancer imaging prior to radionuclide therapy has been found in a cyclotron-produced scandium-44 agent, according to a study published online Nov. 6 in the Journal of Nuclear Medicine.

Ga-68 is a common PET agent for scouting of malignancies prior to cancer treatment with lutetium-177, but it has a brief half-life of 68 minutes and requires an in-house generator, which can be costly. Cristina Muller, PhD, from the department of nuclear medicine at the Center for Radiopharmaceutical Sciences ETH-PSI-USZ, Paul Scherrer Institute, Villigen-PSI, in Switzerland, and colleagues conducted preliminary testing of a Sc-44 DOTA-folate conjugate, which offers a half-life of just under four hours.

“This study presents a high-yield production and efficient separation method of Sc-44 at a quality suitable for radiolabeling of DOTA-functionalized biomolecules,” wrote Muller et al. “An in vivo proof-of-concept study using a DOTA-folate conjugate demonstrated the excellent features of Sc-44 for PET imaging. Thus, Sc-44 is a valid alternative to Ga-68 for imaging and dosimetry before Lu-177 radionuclide tumor therapy.”

Results of the study showed that this formula of Sc-44 DOTA led to a maximum yield of 350 MBq (megabecquerel) at a purity greater than 99 percent.

Both in vitro and in vivo studies revealed the Sc-44 PET agent to be a stable and high-performing alternative to Ga-68. Pharmacokinetics of the agent compared to Lu-177 were nearly matching.