Catalytic activity of an in vivo tumor targeted anti-CEA scFv::carboxypeptidase G2 fusion protein.

Antibody-directed enzyme prodrug therapy (ADEPT) targets an enzyme selectively to a tumor where it converts a relatively non-toxic prodrug to a potent cytotoxic drug. Previous clinical work using antibody-enzyme chemical conjugates has been limited by the moderate efficiency of tumor targeting of these molecules. To address this a recombinant fusion protein composed of MFE-23, an anti-carcinoembryonic antigen (CEA) single chain Fv (scFv) antibody, fused to the amino-terminus of the enzyme carboxypeptidase G2 (CPG2) has been constructed to achieve ADEPT in CEA-producing tumors. MFE-23::CPG2 fusion protein was overexpressed in Escherichia coli and purified using CEA affinity chromatography. Efficacy of MFE-23::CPG2 delivery to tumors in vivo was assessed by measuring catalytic activity after intravenous injection of purified MFE-23::CPG2 into nude mice bearing CEA-positive LS174T human colon adenocarcinoma xenografts. Recombinant MFE-23::CPG2 cleared rapidly from circulation and catalytic activity in extracted tissues showed tumor to plasma ratios of 1.5:1 (6 hr), 10:1 (24 hr), 19:1 (48 hr) and 12:1 (72 hr). (125)I-MFE-23::CPG2 was retained in kidney, liver and spleen but MFE-23::CPG2 catalytic activity was not, resulting in excellent tumor to normal tissue enzyme ratios 48 hr after injection. These were 371:1 (tumor to liver), 450:1 (tumor to lung), 562:1 (tumor to kidney), 1,477:1 (tumor to colon) and 1,618:1 (tumor to spleen). Favorable tumor : normal tissue ratios occurred at early time points when there was still 21% (24 hr) and 9.5% (48 hr) of the injected activity present per gram of tumor tissue. The high tumor concentrations and selective tumor retention of active enzyme delivered by MFE-23::CPG2 establish that this recombinant fusion protein has potential to give improved clinical efficiency for ADEPT.

Exemplifying guidelines for preparation of recombinant DNA products in phase I trials in cancer: preparation of a genetically engineered anti-CEA single chain Fv antibody.

Products of recombinant DNA technology have potential for the diagnosis or treatment of cancer. There is a need to investigate whether they function by the intended mechanism in small phase I clinical trials before their suitability for more extensive studies can be assessed. Quality and safety of these products should be assured prior to their use in humans in a way which is appropriate to the preliminary nature of the trials but not inhibitory to progress. The Cancer Research Campaign control recommendations for products derived from recombinant DNA technology (Begent RHJ and associates. Eur J Cancer 1993, 29A, 13, 1907-1910) provide guidelines for the production of new biotechnology products in academic research units within a relatively short time, while ensuring appropriate quality and safety. The practical application of the guidelines requires that solutions are found for the quality and safety issues during the production of recombinant products. We describe an approach to the relevant quality and safety issues during and after the production and purification of a genetically engineered anti-carcinoembryonic antigen (CEA) single chain Fv (scFv) antibody for a phase I trial of radioimmunoguided surgery with the intention of providing a model for other products.

Suicide among psychiatric in-patients in the Wellington region.

To identify risk factors for in-patient suicide, a case-control study of in-patient suicide was conducted in the Wellington Area Health Board region between 1984 and 1989 on 27 cases and 86 controls. The risk of in-patient suicide was increased among individuals who had been compulsorily admitted, suffered from schizophrenia, had a past history of deliberate self harm, had been in hospital for more than a month, or were unmarried. Notably, there was no relationship with physical health, a history of substance abuse, number of psychiatric admissions and time since the last known episode of deliberate self harm. These characteristics can assist clinical assessment of individual suicidal risk. Further evaluation of the relation of compulsory admission to suicide is required.

New Zealand suicides 1984-8.

AIMS: to determine regional differences in suicide with special attention to inpatients and prisoners. METHODS: all cases of suicide 1984-8 were identified from coroners' register and age, sex, method of suicide, date of death, place of inquest, occupation and prisoner or inpatient status were recorded. RESULTS: between 1984 and 1988 there were 2019 suicides. Subjects were usually male and hanging was the commonest method of achieving death. Northland-Auckland had the highest regional suicide rate and the highest prison suicide rate; and Wellington-Wairarapa had the lowest regional suicide rate, the lowest prison suicide rate but the highest inpatient suicide rate of the five regions studied. CONCLUSIONS: the high regional and prison rates of suicide in Northland-Auckland were probably because the largest city in New Zealand lies within its boundaries. The high inpatient suicide rate in Wellington-Wairarapa could not be explained by the regional rate, nor by controlling for the number of admissions. This pointed to regional differences in the delivery of psychiatric care.

Characterisation of antibodies to urinary gonadotrophin peptide.

There is now general recognition that human chorionic gonadotropin (hCG), its beta subunit and its fragments are valuable diagnostic markers of trophoblastic and some non-trophoblastic malignancies. Urinary gonadotropin peptide (UGP) contains at least one epitope which cross-reacts with the beta-subunit of hCG. In order to assess the potential of UGP as a tumour marker in its own right, it was paramount that any measurements made could be regarded as specific for UGP and not cross-reactive with either hCG or human luteinising hormone (hLH). Four antibodies were tested, two polyclonal (AK12 and DR-Pool) and two monoclonal (2C2 and 6D3). Initial screening using radioiodinated (125I) UGP, hCG, hCG beta-subunit and hLH showed that the polyclonal antibodies bound to all four gonadotrophins, whilst the monoclonal antibodies bound only to the radioiodinated UGP. The antibodies were tested in both radioimmunoassay (RIA) and immunoradiometric assay (IRMA-sandwich assay) systems. The parameters measured were sensitivity and specificity for UGP. The polyclonal antibodies used in the RIA system produced a sensitive assay (0.2 ng/ml UGP) which was relatively specific; cross-reactions for the AK12 antibody (at 50% inhibition) were 5% for hCG, 11% for its beta-subunit, 0.4% for the alpha-subunit and 2.6% for hLH. The monoclonal antibodies performed optimally in the IRMA system. Immobilised 2C2 and radiolabelled (125I) AK12 produced a system that had a sensitivity of 0.4 ng/ml UGP and cross-reactivity (50% maximum binding) of 2% for the hCG beta-subunit and less than 1% for hCG, hLH and the hCG alpha-subunit.