Gallium-67/gallium-68-[DFO]-octreotide--a potential radiopharmaceutical for PET imaging of somatostatin receptor-positive tumors: synthesis and radiolabeling in vitro and preliminary in vivo studies.
When labeled with gamma-emitting radionuclides, somatostatin analogs have the potential to localize somatostatin receptor-positive tumors using gamma camera scintigraphy. We present a somatostatin analog, [DFO]-octreotide (SDZ 216-927), that comprises desferrioxamine B coupled to octreotide via a succinyl linker. This conjugate can be labeled with either 67Ga for gamma scintigraphy or 68Ga for PET imaging. The 67Ga-labeled conjugate is stable in vitro to autoradiolysis over a 24-hr period.


METHODS
Rats bearing a somatostatin receptor-positive pancreatic islet cell tumor were injected with 20 MBq of 67Ga[DFO]-octreotide (33 GBq 67Ga/mumole).


RESULTS
After 1 hr, the accumulation of 67Ga[DFO]-octreotide was 0.38 +/- 0.08 %ID/g and the tumor-to-nontumor ratios for blood, muscle, liver and intestine were 2.5, 7.4, 1.9 and 1.6, respectively. PET studies with 68Ga[DFO]-octreotide recorded a very rapid accumulation at the tumor and a subsequent residence half-life of about 6 hr.


CONCLUSIONS
Gallium-68-[DFO]-octreotide can be used in PET studies to diagnose receptor-positive tumors such as gastroenteropancreatic, small-cell lung and breast tumors.
Smith-Jones
P M
PM
Institute of Nuclear Medicine, University Hospital, Basel, Switzerland.
Stolz
B
B
Bruns
C
C
Albert
R
R
Reist
H W
HW
Fridrich
R
R
Mäcke
H R
HR
D000818:Animals; D018273:Carcinoma, Islet Cell / Q000000981:diagnostic imaging*; D003676:Deferoxamine / Q000031:analogs & derivatives* / Q000138:chemical synthesis; D006801:Humans; D066298:In Vitro Techniques; D007553:Isotope Labeling; D015282:Octreotide / Q000031:analogs & derivatives* / Q000138:chemical synthesis; D010190:Pancreatic Neoplasms / Q000000981:diagnostic imaging*; D051381:Rats; D017481:Receptors, Somatostatin; D014018:Tissue Distribution; D014055:Tomography, Emission-Computed
D017481:Receptors, Somatostatin; C082116:desferrioxamine B-succinyl-phenylalanine(1)-octreotide; D003676:Deferoxamine; D015282:Octreotide