Intraperitoneal alpha-radioimmunotherapy in mice using different specific activities.
OBJECTIVE
The aim of this study was to investigate the therapeutic efficacy of the alpha-radioimmunotherapy of ovarian cancer in mice, using different specific activities. This study was performed by using the monoclonal antibody, MX35 F(ab')(2), labeled with the alpha-particle-emitter, 211At.


METHODS
Animals were intraperitoneally inoculated with approximately 1 x 10(7) cells of the cell line, NIH:OVCAR-3. Four (4) weeks later, five groups of animals were given 400 kBq of 211At-MX35 F(ab')(2) with specific activities equal to 130, 65, 32, 16, or 4 kBq/microg, respectively (n = 18 in each group). As controls, animals were given unlabeled MX35 F(ab')(2) (n = 12). Eight (8) weeks after treatment, the animals were sacrificed and the presence of macro- and microscopic tumors and ascites was determined.


RESULTS
The tumor-free fractions (TFFs) of the animals, defined as the fraction of animals with no macro- and microtumors and no ascites, were 0.67, 0.73, 0.50, 0.50, and 0.17 when treated as above. Only the TFF of 0.17, for the specific activity of 4 kBq/microg, was significantly less, compared to that of the specific activity of 130 kBq/microg. The TFF for the specific activity of 4 kBq/microg showed a significant lowering, compared to the specific activity of 130 kBq/microg (p < 0.05). Treatment with unlabeled MX35 F(ab')(2) resulted in a TFF of zero.


CONCLUSIONS
A specific activity-dependent therapeutic outcome could not be shown in the interval of 130- to 16 kBq/mug. For lower specific activities (i.e., 4 kBq/microg), the therapeutic efficacy was significantly lowered.
Elgqvist
Jörgen
J
Institute of Clinical Sciences, The Sahlgrenska Academy at the University of Gothenburg, Gothenburg, Sweden. jorgen.elgqvist@gu.se
Andersson
Håkan
H
Haglund
Elin
E
Jensen
Holger
H
Kahu
Helena
H
Lindegren
Sture
S
Warnhammar
Elisabet
E
Hultborn
Ragnar
R
D000512:Alpha Particles; D000818:Animals; D000911:Antibodies, Monoclonal / Q000008:administration & dosage / Q000737:chemistry; D045744:Cell Line, Tumor; D004195:Disease Models, Animal; D005260:Female; D007263:Infusions, Parenteral; D051379:Mice; D010051:Ovarian Neoplasms / Q000276:immunology / Q000532:radiotherapy*; D016499:Radioimmunotherapy / Q000379:methods*
D000911:Antibodies, Monoclonal