Antibody guided targeting of non-small cell lung cancer using 111In-labeled HMFG1 F(ab')2 fragments.

Immunoscintigraphy using F(ab')2 fragments of tumor-associated monoclonal antibody HMFG1 was performed in 14 patients with primary and metastatic non-small cell carcinoma of lung cancer. The antibody was conjugated with diethylenetriamine pentaacetic acid and labeled with 111In. Quality control studies showed efficient incorporation of 111In onto antibody (5 mCi/mg), no significant loss of immunoreactivity, and in vitro and in vivo stability. The optimal time for imaging was between 48 and 72 h. Following i.v. administration, serum activity fell rapidly (t1/2a = 2.5 +/- 1.3 (SD) h; t1/2b = 42 +/- 4.5 h). The majority of the radioactivity was associated with the plasma and not with the blood cells. All patients had a significant concentration of 111In in the liver (approximately 20% of the injected dose, 48 h postadministration). No toxicity was encountered. No human antimurine-IgG antibody was detected in any of the patients within 4 months of follow-up, even in patients receiving two administrations of F(ab')2 fragments. Localization of all primary lesions and the majority (80%) of metastatic lesions was achieved. Seven of 14 patients were also studied using a 111In-labeled nonspecific antibody (Fab')2 fragment (4C4). In three patients the specificity index was higher than the other four (P less than 0.05). We conclude that although successful targeting of 111In-labeled (Fab')2 fragments of HMFG1 can be achieved in patients with non-small cell carcinoma of lung, observable tumor localization can also be achieved using a nonspecific antibody. Based on these findings, we recommend that in order to demonstrate specific radioimmunolocalization, patients with lung and possibly other tumor types should be studied using both specific and nonspecific antibodies.

Antibody guided diagnosis and therapy of brain gliomas using radiolabeled monoclonal antibodies against epidermal growth factor receptor and placental alkaline phosphatase.

Twenty-seven patients with brain glioma were scanned using 123I-labeled monoclonal antibodies against epidermal growth factor receptor (EGFR1) or placental alkaline phosphatase (H17E2). Successful localization was achieved in 18 out of 27 patients. Eleven out of 27 patients were also studied using a nonspecific control antibody (11.4.1) of the same immunoglobulin subclass and observable tumor localization was also achieved in five patients. The specificity of targeting was assessed by comparing images obtained with specific and nonspecific antibodies and by examining tumor and normal tissue biopsies after dual antibody administration. Ten patients with recurrent grade III or IV glioma who showed good localization of radiolabeled antibody were treated with 40-140 mCi of 131I-labeled antibody delivered to the tumor area intravenously (n = 5) or by infusion into the internal carotid artery (n = 5). Six patients showed clinical improvement lasting from 6 mo to 3 yr. One patient continues in remission (3 yr after therapy), but the other five who responded initially relapsed 6-9 mo after therapy and died. No major toxicity was attributable to antibody-guided irradiation. Targeted irradiation by monoclonal antibody may be clinically useful and should be explored further in the treatment of brain gliomas resistant to conventional forms of treatment.

Phosphate compounds in bone scanning.

Bone scanning with radioactive isotopes has been used to study a wide variety of disorders. Recently certain phosphate compounds, labelled with technetium, have been used as bone scanning agents. The comparative merits of three technetium-labelled phosphate compounds currently available for bone scanning--pyrophosphate, tripolyphosphate and ethylhydroxydiphosphonate (EHDP) have been compared in rabbits. Each substance was injected into ten rabbits and blood was withdrawn at regular intervals. The animals were killed at four hours and the blood and tissue samples were assayed for radioactivity. The results show that EHDP has a more rapid blood clearance than the other two agents, with a resultant improvement in the bone to soft-tissue ratio. Of the three substances investigated technetium-labelled EHDP was the best and might allow the technique of scanning to be used on a wide scale for the general study of bone and its pathology.

Covalent attachment of metal chelates to proteins:the stability in vivo and in vitro of the conjugate of albumin with a chelate of 111indium.

Human serum albumin has been conjugated to 1-(p-bnezenediazonium)-(ethylenedinitrilo)tetraacetic acid, a powerful chelating agent, and radioactive 111indium ions have been added specifically to the chelating groups. The product, with a specific radioactivity of about 1 mCi/mg of protein, was employed as a radiotracer in scintillation scanning studies with human volunteers. Results show that 48 hr after injection, practically all of the label remains attached to albumin. This is confirmed by electrophoresis of serum proteins; 7 days after injection, 85% of the radioactivity in the serum is still in the albumin fraction. These observations agree with in vitro studies of the labeled albumin in human serum, where loss of the metal ion from the chelating group to the protein transferrin amounts to less than 3% after 1 week and less than 5% after 2 weeks. Measurements of the distribution of label in mice up to 23 days after injection suggest that metabolism of the labeled protein does not lead to binding of indium ions by transferrin. The binding of indium and other metal ions by transferrin has previously posed a major impediment to the use of metal chelates for in vivo diagnostic procedures. Demonstration of the kinetic inertness of the chelate in these experiments suggests the use of related chelates as physical probes of biological systems.