Diagnostic Performance of Contrast Enhanced Pulmonary Computed Tomography Angiography for the Detection of Angioinvasive Pulmonary Aspergillosis in Immunocompromised Patients.

Invasive pulmonary aspergillosis (IPA) is one of the major complications in immunocompromised patients. The mainstay of diagnostic imaging is non-enhanced chest-computed-tomography (CT), for which various non-specific signs for IPA have been described. However, contrast-enhanced CT pulmonary angiography (CTPA) has shown promising results, as the vessel occlusion sign (VOS) seems to be more sensitive and specific for IPA in hematologic patients. The aim of this study was to evaluate the diagnostic accuracy of CTPA in a larger cohort including non-hematologic immunocompromised patients. CTPA studies of 78 consecutive immunocompromised patients with proven/probable IPA were analyzed. 45 immunocompromised patients without IPA served as a control group. Diagnostic performance of CTPA-detected VOS and of radiological signs that do not require contrast-media were analyzed. Of 12 evaluable radiological signs, five were found to be significantly associated with IPA. The VOS showed the highest diagnostic performance with a sensitivity of 0.94, specificity of 0.71 and a diagnostic odds-ratio of 36.8. Regression analysis revealed the two strongest independent radiological predictors for IPA to be the VOS and the halo sign. The VOS is highly suggestive for IPA in immunocompromised patients in general. Thus, contrast-enhanced CTPA superior over non-contrast_enhanced chest-CT in patients with suspected IPA.

Phase I/II trial of topotecan given as continuous infusion in combination with oxaliplatin in 5-FU-pretreated patients with colorectal cancer.

BACKGROUND: Oxaliplatin and topotecan are novel options for a variety of neoplasms. Topotecan has shown fewer side effects and higher efficacy when given as a continuous i.v. infusion compared to single doses, but this regimen has not yet been combined with oxaliplatin. PATIENTS AND METHODS: This phase I/II trial was designed to establish the dose-limiting toxicity of a combination of oxaliplatin (85-130 mg/m2 on day 1) and a continuous infusion of topotecan (initial 0.9 mg/m2 over 72-120 h). Eligible patients with metastatic colorectal cancer had progressive disease during, or within 12 weeks after, palliative fluoropyrimidine-based chemotherapy or in whom intolerable 5-FU toxicity had developed. RESULTS: The study included 21 patients. Subjectively the treatment was well tolerated but haematological toxicity was observed with the initial treatment schedule of oxaliplatin 85 mg/m2 on day 1 and topotecan 0.9 mg/m2 on days 1-5. Reducing topotecan to 0.9 mg/m2 on days 1-3 resulted also in acceptable haematological toxicity. In patients completing three or more therapy cycles, median progression-free survival was 5 months, and 50% had stable disease or showed a partial response. CONCLUSION: The recommended dose of this combination for further testing is oxaliplatin 85 mg/m2 on day 1 and topotecan 0.9 mg/m2 per day as a continuous infusion on days 1-3.

Targeted enzyme prodrug therapies.

The cure of cancer is still a formidable challenge in medical science. Long-known modalities including surgery, chemotherapy and radiotherapy are successful in a number of cases; however, invasive, metastasized and inaccessible tumors still pose an unresolved and ongoing problem. Targeted therapies designed to locate, detect and specifically kill tumor cells have been developed in the past three decades as an alternative to treat troublesome cancers. Most of these therapies are either based on antibody-dependent cellular cytotoxicity, targeted delivery of cytotoxic drugs or tumor site-specific activation of prodrugs. The latter is a two-step procedure. In the first step, a selected enzyme is accumulated in the tumor by guiding the enzyme or its gene to the neoplastic cells. In the second step, a harmless prodrug is applied and specifically converted by this enzyme into a cytotoxic drug only at the tumor site. A number of targeting systems, enzymes and prodrugs were investigated and improved since the concept was first envisioned in 1974. This review presents a concise overview on the history and latest developments in targeted therapies for cancer treatment. We cover the relevant technologies such as antibody-directed enzyme prodrug therapy (ADEPT), gene-directed enzyme prodrug therapy (GDEPT) as well as related therapies such as clostridial- (CDEPT) and polymer-directed enzyme prodrug therapy (PDEPT) with emphasis on prodrug-converting enzymes, prodrugs and drugs.

Current constructs and targets in clinical development for antibody-based cancer therapy.

Almost ever since their invention, monoclonal antibodies have held the promise of cancer-specific drug targeting--Paul Ehrlich's "magic bullet"--but only during the past decade have a modest number of anti-cancer antibodies received approval for clinical use. These, however, have proven largely successful, with very different kinds of conventional or recombinant, murine, humanized, recombinant fully human and fusion constructs, and mechanisms of action as diverse as complement or antibody dependent cytotoxicity, anti-angiogenesis, and growth factor inhibition. In these latter two mechanisms of action, antibodies compete with novel small-molecule drugs. This review tries to elucidate current trends in those antibody-based therapeutics that are currently in clinical development. With more than 400 such molecules registered for clinical trials, it is far from a chance to be complete. Still, from those antibodies selected for a closer view, two large trends can be distilled: The movement towards increasingly molecularly defined recombinant constructs, and away from classical antibody effector functions in immune activation towards additional mechanisms of action--either by stimulation or (more often) inhibition of a molecular target function, or by additional functional moieties attached to the antibody scaffold. While these trends probably mark the future of antibody development for cancer therapy and clinical applications in general, a considerable number of more conventional--hybridoma generated or recombinantly chimerized or humanized--Fc receptor-activating antibodies, originally generated a decade or longer ago, continue to make their way through clinical trials, some with remarkable success.

CD4-imitating human antibodies in HIV infection and anti-idiotypic vaccination.

Anti-idiotypic vaccination against HIV infection aims at inducing an anti-gp120 immune response through anti-CD4 Abs mimicking epitopes of the gp120 molecule. The mAb IOT4a induces anti-gp120 Abs in rabbits. This study investigates the presence of human serum Abs cross-reacting with anti-CD4 mAbs and gp120 during HIV infection and after parenteral vaccination with IOT4a. Ten HIV-infected volunteers without immunodeficiency were inoculated s.c. with 0.6, 1.2, or 2.4 mg IOT4a. Six booster injections followed until day 35. Sera from study patients, 80 HIV-positive, and 43 seronegative controls were examined by a panel of assays, including an ELISA using competition against biotinylated recombinant CD4, flow cytometry assaying inhibition of anti-CD4 mAbs and biotinylated gp120 binding to CD4-positive lymphocytes, and an IOT4a immunoblot. After vaccination, an increase in competitive binding activity, which was quantitative in ELISA and flow cytometry, was observed. In the ELISA, competition against biotin-CD4 was quantitatively quenched by preincubating sera with r-gp120 or anti-CD4 mAbs such as IOT4a and Leu3a. Naive sera or sera from blood donors had no such effect in the assays employed, while 5/80 HIV sera showed binding qualities similar to vaccinees. These results suggest that 1) CD4 internal-image Abs emerge in a small proportion of HIV-positive individuals, and 2) parenteral vaccination with mAb IOT4a can induce a gp120 cross-reacting immune response that inhibits gp120 binding to CD4.

A33scFv-cytosine deaminase: a recombinant protein construct for antibody-directed enzyme-prodrug therapy.

A recombinant fusion protein of colon carcinoma binding A33 single chain antibody with cytosine deaminase displayed specific antigen binding and enzyme activity in surface plasmon resonance and is catalytic activity assay. In vitro, it selectively increased the toxicity of 5-FC to A33 antigen-positive cells by 300-fold, demonstrating the potency of this ADEPT strategy.

Pharmacokinetics and microdistribution of polyethylene glycol-modified humanized A33 antibody targeting colon cancer xenografts.

Therapeutic proteins have been conjugated with polyethylene glycol (PEGylation) to reduce immunogenicity and enhance circulating dose. Here we have investigated the effect of PEGylation on immunogenicity, pharmacokinetics, and histologic microdistribution of tumor-targeting antibodies with humanized A33 antibody (huA33) as a model system. Conjugation of huA33 with methoxy-PEG of M(r) 5,000 (32%-34% of primary amines modified) or M(r) 20,000 (16%-18% modification) preserved >50% of native huA33 binding to SW1222 colon cancer cells. In mice, both PEGylated forms cleared from serum moderately slower than native huA33. After repeated immunization with PEG-huA33, antiantibody titers in immunocompetent mice were <5% of those in huA33-treated controls. Both PEG-huA33 forms reached approx. 75% of the maximum tumor dose of huA33 in SW1222-xenografted mice, but their tumor:blood ratios were considerably reduced. To demonstrate immunologic specificity of PEG-huA33 targeting in SW1222 tumor-bearing mice, antigenic sites were presaturated by injecting excess native huA33. This reduced subsequent uptake of PEG-huA33 by up to 80%, whereas presaturation with hu3S193 control antibody had no significant effect. To assess the microdistribution of antibody uptake in the same xenograft model, tumor tissue resected at different time points after antibody administration was examined for human IgG by immunohistochemistry. Both PEG preparations achieved the same peak staining intensity and homogeneity as native huA33 with a delay of several hours. Given the measured reduction in immunoreactivity in vitro, these results demonstrate that the tumor targeting potential of huA33 in vivo is preserved at PEGylation levels sufficient to suppress immunogenicity.