Carol I. Diamanti

Conjugation of antibodies with bifunctional chelating agents: isothiocyanate and bromoacetamide reagents, methods of analysis, and subsequent addition of metal ions.

Preparation of the chelating agent (S)-4-[2,3-bis[bis(carboxymethyl)am ino]propyl]phenyl isothiocyanate is reported. Procedures for conjugation of this and (S)-N-4-[2,3-bis[bis-(carboxymethyl)amino] propyl]phenyl bromoacetamide to monoclonal antibodies and other proteins are described. The conjugates may be purified quickly by centrifugation through Sephadex G-50. The number of protein-bound chelating groups may be measured by titration with standard 57Co2+, using thin-layer chromatography to monitor binding. The labeled products retain their immunoreactivity, as illustrated by experiments in vivo with chelate-conjugated antibody to mouse I-AK antigen.

Use of specific antibody for rapid clearance of circulating blood background from radiolabeled tumor imaging proteins

AbstractA major problem that arises when radiolabeled serum proteins are used for tumor imaging is the presence of a large amount of circulating background activity that persists for several days. This delays imaging for at least 2 days following injection and necessitates computer subtraction of simulated background (second radiopharmaceutical injection) which introduces artifacts that are difficult to control. We propose here the injection of specific antibody immediately before imaging as an alternate way of reducing blood background through clearance of the immune complex by the liver. 111In-alkyl human transferrin and IgG were injected IV in BALB/c tumor mice, and followed in 18 h by anti-human transferrin and anti-human IgG antibody IV. Two hours later, the tumor and organ distribution of activity was compared with control mice not receiving antibody. 111In-transferrin blood activity was reduced to 1/48 of control with no decrease in tumor concentration: as a result, the tumor to blood ratio increased from 1.4:1 to 78:1. 111In-IgG blood activity was reduced to 1/17 of control, again with no decrease in tumor. The tumor to blood ratios increased from 0.7:1 to 17:1. The liver picked up most of the blood activity with none of the complex going to spleen, bone marrow, or kidney. Dog experiments showed clearance of blood was 90% complete in less than 15 min following antibody injection. Simultaneous scintillation images showed complete clearance of activity from the heart and great vessels in the chest and neck, and over the abdomen, with a concomitant increase in liver activity but no increase in spleen, kidney, or bone marrow activity. These studies show the feasibility of using specific antibody to lower the blood background just minutes prior to tumor imaging procedures using radiolabeled proteins.

Rapid synthesis and quality control of 68Ga-labeled chelates for clinical use

Abstract Rapid synthesis of radiopharmaceuticals labeled with 68 Ga obtained from a 68Ge68Ga generator is described. Approximately 70% of the available 68 Ga activity was obtained in 4 mL 1 N HCl and evaporated to dryness in 5 min in a Rotovap system. Activity was reconstituted in 0.01 N HCl and 0.5 M NaAc, MPO added and pH adjusted to 6.7–7.0 with NaOH. Previously prepared human platelets were labeled with 68 Ga and reinjected within 1 h of eluting the generator.

68Ga MPO Platelets in Human Pet Thrombus Imaging

The excellent immediate results of various interventional techniques for recanalization of peripheral and coronary arterial lesions has highlighted the persistant problem of restenosis, occurring in as many as 30% of patients in 1 year and 66% in 2 years1. Platelet deposition and its sequellae are among the most important possible causes of restenosis, and intensive research on the prevention of restenosis has involved many new anti-platelet drugs2. A method of measuring platelet deposition in vivo, would better define the effectiveness of the various anti-platelet protocols, help select patients and permit monitoring of anti-platelet drug activity3.