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S F Rosebrough

Publications and source records attributed to S F Rosebrough.

18 recordsLinked to original sources
PubMed2000

Isothiocyanate-trigalactose: application for antibody-targeted delivery of diagnostic and therapeutic agents.

Radiolabeled monoclonal antibodies (MAb) and MAb-streptavidin conjugates exhibit slow blood clearance which impedes radioimmunoimaging and radioimmunotherapy. To control blood clearance and lower background levels, lesion-specific targeting proteins can be modified with galactose derivatives for liver uptake via the hepatocyte galactose receptor. In this study, an isothiocyanate-trigalactose derivative (ITC-Tgal) designed for direct coupling to protein amino groups, was synthesized and characterized. In vitro experimentation demonstrated efficient conjugation of ITC-Tgal to streptavidin (SA) and MAb Fab fragment with a corresponding decrease in protein net charge. In vivo studies were conducted with radiolabeled ITC-Tgal modified and native SA and MAb Fab fragment. ITC-Tgal modified SA and Fab fragment exhibited increased blood clearance with the liver uptake and the rate of blood clearance controlled by the extent of ITC-Tgal modification.

Animals↗
PubMed1996

Galactose-modified streptavidin-GC4 antifibrin monoclonal antibody conjugates: application for two-step thrombus/embolus imaging.

Diagnostic and therapeutic procedures utilizing the high affinity streptavidin (SA)/biotin system are being investigated for in vivo use. We are developing a rapid two-step imaging technique for the diagnosis of deep venous thrombosis and pulmonary embolism. The optimal SA-bound targeting moiety would circulate adequately for sufficient lesion accumulation, but nonbound reagent would clear in a reasonably short time before the injection of radiolabeled biotin. The objective of this study was to cross-link SA and galactose-modified SA to GC4 antifibrin monoclonal antibody and to study the pharmacokinetics and biodistribution of the radiolabeled GC4-SA conjugates after injection into rabbits. A cross-linking method was developed for the synthesis of the GC4-SA conjugates via the addition reaction of sulfhydryl containing SA derivatives with maleimide-GC4. In vivo, radiolabeled trigalactose modified SA-GC4 exhibited a much faster blood clearance compared to mono-galactose modified GC4-SA or GC4-SA containing no galactose.

Animals↗
PubMed1996

Biochemical modification of streptavidin and avidin: in vitro and in vivo analysis.

UNLABELLED: The high affinity streptavidin (or avidin)/biotin system is being investigated for imaging and radiotherapy procedures. Streptavidin (SA) and avidin exhibit markedly different pharmacokinetics, with avidin clearing from the blood much faster than SA. To optimize blood clearance kinetics, SA and avidin were biochemically modified and analyzed in vitro and in vivo. METHODS: Galactose moieties were covalently attached to promote binding by hepatocyte galactose receptors and hasten SA clearance. To prolong avidin clearance, avidin was deglycosylated and/or neutralized by acetylation of its lysine amino acids. In vitro, the modified proteins were analyzed by isoelectric focusing, SDS polyacrylamide electrophoresis and a biotin binding saturation assay. The modified and native proteins were radiolabeled with 131I and injected into rabbits for pharmacokinetic, redistribution and imaging analysis. RESULTS: For SA, the resulting increase in blood clearance and liver accumulation was correlated to the amount of galactose bound to SA. For avidin, each type of modification increased its circulation time, with the slowest clearance resulting from a combination of deglycosylation and neutralization. CONCLUSION: Biochemical modification of SA and avidin resulted in altered pharmacokinetics compared to the native proteins. Modified SA or avidin, when cross-linked with a lesion-specific targeting agent, may be applicable for rapid two-step in vivo imaging techniques.

Animals↗
PubMed1996

Two-step immunological approaches for imaging and therapy.

Radiolabeled monoclonal antibodies and their F(ab')2 and Fab fragments have been successful for imaging and therapy. However, their prolonged circulation and nonspecific accumulation in metabolic organs have resulted in high background radioactive levels and delayed imaging times. Current approaches are two- and three-step procedures consisting of first, the injection of a targeting moiety, which has specific binding affinity for both a lesion and a small molecular weight radiolabeled agent, and, second, a subsequently injected radioactive diagnostic or therapeutic agent. The rapid blood clearance of the free radiolabeled agent greatly reduces background levels and radiation dose and increases target-to-background ratios. This review will focus on two different approaches: 1) bispecific monoclonal antibodies and 2) monoclonal antibodies in conjunction with the streptavidin (avidin)/biotin system.

Animals↗
PubMed1995

Quantification and lowering of serum biotin.

An enzyme-linked assay was developed to quantify serum biotin concentrations in experimental animals and humans. With this assay the effect on serum biotin concentration after intravenous injection of streptavidin or the addition of avidin to food was studied in rabbits and dogs. Intravenous injection of streptavidin reduced serum biotin values quickly but temporarily, in a dose-dependent manner in both species. Addition of avidin to the diet lowered biotin values approximately four- to fivefold in the rabbits, with resultant biotin concentrations similar to those of humans.

Animals↗
PubMed1995

Synthesis, pharmacokinetics, and biodistribution of 67GA deferoxamineacetyl-cysteinylbiotin.

The exceptionally high affinity of streptavidin for biotin may be exploited for two-step in vivo approaches for delivering radiolabelled biotin derivatives to lesion-bound streptavidin-conjugated monoclonal antibodies. A radiolabeled biotin derivative was prepared, and its characterization, stability, pharmacokinetics, and biodistribution studies are presented. This derivative contains deferoxamine, a chelating moiety with high affinity for trivalent metals suitable for imaging and therapy. Deferoxamineacetyl-cysteinylbiotin (DACB) was synthesized in three steps: nucleophilic reaction of deferoxamine with N-hydroxysuccinimide iodoacetate, aminolysis of N-hydroxysuccinimide biotin by L-cysteine, followed by coupling of cysteinylbiotin with N-iodoacetyldeferoxamine. DACB was characterized by matrix-assisted laser desorption/ionization MS. Radiolabeling of DACB with 67Ga led to a labeling efficiency of > 95%. Pharmacokinetics of 67Ga DACB exhibited rapid blood clearance, with < 10% circulating at 30 min and < 1% at 6 hr. Plasma samples collected at various time intervals showed > 95% binding with streptavidin, indicating in vivo stability of 67Ga DACB. Urinalysis showed > 80% of the administered dose excreted at 6 hr. Biodistribution data at 6 hr showed < 1% radioactivity remaining per organ.

Animals↗
PubMed1993

Pharmacokinetics and biodistribution of radiolabeled avidin, streptavidin and biotin.

The extraordinary high affinity of avidin and streptavidin for biotin may be exploited in a two-step approach for delivering radiolabeled biotin derivatives suitable for imaging and therapy to target-bound streptavidin or avidin conjugated monoclonal antibodies (MAbs). The in vivo pharmacokinetics and biodistribution of radiolabeled avidin, streptavidin (SA) and DTPA-biocytinamide (DTPA-biotin) were studied in the rabbit and dog. SA circulated in the blood similar to other 60 kDa proteins, avidin cleared immediately and DTPA-biotin exhibited plasma clearance by glomerular filtration.

Animals↗
PubMed1993

Plasma stability and pharmacokinetics of radiolabeled deferoxamine-biotin derivatives.

The extraordinary high affinity of biotin for streptavidin may be exploited in a two-step in vivo approach for delivering radiolabeled biotin derivatives suitable for imaging and therapy to lesion-bound streptavidin-conjugated monoclonal antibodies. Compared to the use of directly radiolabeled monoclonal antibodies, the two-step approach is desirable because of the fast renal clearance of radiobiotin, which reduces in vivo background levels and radiation dose. Deferoxamine binds with high-affinity trivalent metals useful for imaging and radiotherapy. Three deferoxaminebiotin derivatives were synthesized, radiolabeled and their stabilities tested in vitro in dog plasma and in vivo in the dog by an avidin binding assay and high-performance liquid chromatography. Defero-desaminolysyl-biotin (DLB) was unstable, with immediate degradation evident. A plasma enzyme, biotinidase, converts biocytin to biotin. DLB closely resembles biocytin, and analysis of the urine and plasma suggested rapid degradation of DLB to biotin and desaminolsyl-deferoxamine. Defero-biotin, a direct conjugate of deferoxamine and biotin, was similarly tested and found to be more stable. Defero-acetyl-cysteinyl-biotin contains a carboxyl group adjacent to the amide bond cleavage site of biotinidase. In vitro at 24 hr in plasma, defero-acetyl-cysteinyl-biotin was 87% stable, compared to 45% and 15% for defero-biotin and DLB, respectively. The pharmacokinetics of the three derivatives were similar, with 80% of the injected doses found in the urine at 6 hr; however, only defero-acetyl-cysteinyl-biotin was present as the intact moiety.

Animals↗
PubMed1990

Thrombus imaging: a comparison of radiolabeled GC4 and T2G1s fibrin-specific monoclonal antibodies.

Radioimmunoimaging of experimentally-induced canine thrombi has previously been achieved with iodine-131- and indium-111-labeled (131I and 111In) anti-fibrin T2G1s monoclonal antibody (MAb). We now compare T2G1s to another anti-fibrin MAb, designated GC4, for imaging fresh and aged canine thrombi. GC4 is specific for a neoepitope exposed on fibrin later in the thrombolytic process after plasmin digestion. Femoral venous thrombi were induced in six groups of dogs, each containing three dogs. In two groups, the MAbs were compared when the thrombi were 3-hr or 3-days old at the time of injection, and the dogs were killed at 48 hr. In thrombi 3-hr-old, the GC4/T2G1s concentration ratio averaged 0.53 compared to 1.9 in 3-day-old thrombi. Two groups of dogs with thrombi 1- or 3-days-old were heparinized before MAb injection and were killed at 24 hr. The heparinized dogs with thrombi 1- or 3-days-old had GC4/T2G1s mean ratios of 2.3 and 2.9, respectively. In the unheparinized groups, the corresponding ratios were 1.1 and 1.9. GC4 may be more useful for clinical thrombus imaging than T2G1s because spontaneous venous thrombi are usually several days old at the time of presentation and patients are often heparinized immediately.

Angiography↗
PubMed1989

Immunoreactivity of 111In and 131I fibrin-specific monoclonal antibody used for thrombus imaging.

Immunoreactivity of radiolabeled F(ab')2 fragment of anti-fibrin T2G1s monoclonal antibody was determined by affinity chromatography using fibrin-coated Sepharose. This preparation is useful for thrombus detection in vivo by gamma camera imaging, provided a high percentage of immunoreactivity is retained after labeling. For 111In labeling, DTPA/F(ab')2 molar ratios were varied from 1000 to 6600/1, with little effect on immunoreactivity. Immunoreactivity of the F(ab')2 fragment, labeled with imaging doses of 131I and 111In, remained high and ranged from 81% to 89%. Equilibrium binding analysis determined the affinity constants of 111In- or 125I-labeled T2G1s and its F(ab')2 and Fab fragments, to be equivalent (Kd approximately 3 X 10(-8) M). This suggests that only one binding domain of T2G1s binds to fibrin even though there are two antigenic sites/mol of fibrin.

Antibodies, Monoclonal↗
PubMed1988

Thrombus imaging with indium-111 and iodine-131-labeled fibrin-specific monoclonal antibody and its F(ab')2 and Fab fragments.

We have previously reported successful imaging of fresh (2-4 hr old) and aged (1-5 days old) canine thrombi with 131I-labeled intact monoclonal antibody (MAb) specific for fibrin. We now report thrombus imaging with 131I-labeled F(ab')2 and Fab and 111In-labeled intact MAb, F(ab')2, and Fab. Indium-111-labeled F(ab')2 proved to be the best imaging agent due to less nonspecific binding in the liver than whole IgG. Image quality was improved by the higher administered dose permissible with 111In and its better physical characteristics for imaging, compared to 131I. Immunofluorescence of fresh human histologic sections showed intact MAb and F(ab')2 binding to thrombi, pulmonary emboli, and atherosclerotic plaques, strengthening the feasibility of clinical thrombus imaging.

Animals↗
PubMed1987

Aged venous thrombi: radioimmunoimaging with fibrin-specific monoclonal antibody.

Radioimmunoimaging of fresh canine venous thrombi with a murine monoclonal antibody specific for human and dog fibrin has been reported. Successful imaging of canine deep venous thrombi 1, 3, and 5 days old at the time of antibody injection is reported. Images were positive in all dogs, and the uptake of fibrin-specific antibody was equivalent to that of fresh thrombi.

Animals↗
PubMed1986

Purification of fibrin-specific monoclonal antibody from ascites fluid by preparative isoelectric focusing.

With the increased use of site-directed monoclonal antibodies (MAbs) for the detection and localization of antigens (Ags) in vivo, an efficient, noninjurious MAb purification procedure is essential [1-9]. In this study MAb was purified by both immunoaffinity chromatography (IAFC) and preparative isoelectric focusing (PIEF). For anti-fibrin MAb purified by each method, the purification efficiency, blood clearance, and in vivo localization in thrombi were compared. Blood clearance rates and in vivo localization were determined by a double isotope assay: affinity-purified MAb was labeled with I-125, and PIEF-purified MAb was labeled with I-131. Both were injected intravenously into a dog with an experimentally induced femoral vein thrombus. MAb purified by PIEF had a slightly longer biological T 1/2 resulting in comparably higher thrombus localization. Due to its efficiency, PIEF warrants consideration when purified MAb is desired.

Animals↗
PubMed1985

Radioimmunoimaging of venous thrombi using iodine-131 monoclonal antibody.

Murine monoclonal antibody (Mab) specific for the NH2-terminal region of human fibrin, but not cross-reactive with fibrinogen, was used in radioimmuno-imaging of fresh, induced venous thrombi in three dogs. Iodine-131-labeled Mab was injected intravenously, with iodine 125-labeled polyclonal murine gamma-G globulin (IgG) simultaneously injected as a control. Images were strongly positive at 24 and 48 hours in all three animals, with thrombus-to-blood and thrombus-to-muscle ratios of 8.4 and 228.0, respectively, for I-131-labeled Mab; these ratios for control IgG were 1.2 and 13.0. Radioimmunodetection of thrombi in vivo is feasible in dogs and may have clinical application since Mab is specific to human fibrin.

Animals↗