The FDA recently approved a Society of Nuclear Medicine (SNM)-sponsored, centralized, multicenter, investigational new drug (IND) application for 18F-labeled 3’-deoxy-3’-fluorothymidine (FLT). The FDA has agreed to allow multiple sources of FLT to be evaluated, reviewed, and accepted for use under a single IND. It has also agreed to base the IND review process for acceptance of the various investigational FLT products on the end product specifications.
According to SNM President Robert W. Atcher, PhD, MBA, “Until now, FLT has been evaluated for investigational use under an IND at a limited number of imaging centers that have FDA-approved INDs in place. With the SNM’s centralized IND now approved, multicenter investigational imaging is achievable in large (100+ center), therapeutic clinical trials through a single cross reference letter.”
FLT is an investigational PET imaging biomarker that has apparent promise for the demonstration of tumor proliferation. Therapeutics developers who want to use FLT as a surrogate marker of effectiveness in the development of novel cancer therapies have been seeking access to a centralized, multicenter IND for FLT to speed and simplify the drug-development process. The SNM’s application was made possible, in part, through a letter of cross-reference to a master FLT IND held by the Cancer Imaging Program at the National Cancer Institute (NCI).
“We’re aware that we don’t have the resources needed to conduct large phase 3 trials,” says James L. Tatum, MD, associate director of the Cancer Imaging Program. “Therefore, we strongly encourage imaging societies, academic institutions, cooperative groups, and commercial sectors to work together to effectively lower this last barrier.”
During the past four years, the NCI has allowed more than 20 entities to cross-reference this master IND. SNM combined the NCI information with data obtained from the University of Pennsylvania, the Mayo Clinic, the University of Iowa, the University of Utah, and the University of Washington. Most of these institutions hold a single, site-approved IND for FLT; however, each facility follows a different manufacturing process. The individual INDs describe end product FLT that is unique to each facility. Prior to the new, centralized IND submission, the FDA has not been asked to review these various production processes together or to base acceptance of the chemistry, manufacturing, and controls on the end product formulation. Centralized, multicenter INDs are a key enabler for the recently formed SNM Clinical Trials Network, whose mission is to increase the use of imaging biomarkers in multicenter clinical trials.
“Since we received approval of SNM’s centralized IND, several pharmaceutical developers have expressed interest in using FLT in near-term, clinical trial multicenter work,” says Atcher. Active clinical trials utilizing FLT are expected to begin this year.
— Source:Society of Nuclear Medicine

