Immuno-PET quantitation of de2-7 epidermal growth factor receptor expression in glioma using 124I-IMP-R4-labeled antibody ch806.

UNLABELLED: Overexpression, activation, and mutations of the epidermal growth factor receptor (EGFR) are commonly found in solid tumors. The aim of this study was to develop a PET-based method for detecting the constitutively active mutant de2-7 EGFR, which is associated with disease progression and resistance to chemotherapy and radiotherapy in glioma. METHODS: The chimeric antibody ch806, which selectively binds an epitope of the EGFR that is exposed only on overexpressed, mutant, or ligand-activated forms of the receptor, was conjugated to the radiohalogen (124)I via the residualizing ligand IMP-R4, and in vitro properties were characterized. In vivo biodistribution and small-animal PET studies were performed in BALB/c nude mice bearing U87MG.de2-7 glioma xenografts. Imaging results were correlated with measured tumor uptake of the radioconjugate. RESULTS: (124)I-IMP-R4-ch806 had an immunoreactivity of 78.3% and was stable for 7 d when incubated in serum in vitro. The biodistribution analysis of (124)I-IMP-R4-ch806 demonstrated a maximal uptake of 30.95 +/- 6.01 percentage injected dose per gram (%ID/g) in U87MG.de2-7 xenografts at 48 h after injection, with prolonged tumor retention (6.07 +/- 0.80 %ID/g at 216 h after injection). The tumor-to-blood ratio increased from 0.44 at 4 h after injection to a maximum of 4.70 at 168 h after injection. PET of (124)I-IMP-R4-ch806 biodistribution was able to clearly detect the U87MG.de2-7 tumors at 24 h after injection and for at least 168 h after injection. Correlation between tumor PET image quantitation of (124)I-IMP-R4-ch806 and %ID/g determined from resected tissues (r = 0.9350) was excellent. CONCLUSION: These results show that immuno-PET with (124)I-IMP-R4-ch806 is feasible and allows noninvasive quantitation of de2-7 EGFR expression in vivo.

Enhanced efficacy of radioimmunotherapy with 90Y-CHX-A''-DTPA-hu3S193 by inhibition of epidermal growth factor receptor (EGFR) signaling with EGFR tyrosine kinase inhibitor AG1478.

PURPOSE: Monoclonal antibodies and tyrosine kinase inhibitors specific for the epidermal growth factor receptor (EGFR) have been shown to enhance the effect of external beam radiation on EGFR-positive tumors. The effect of EGFR signaling abrogation by EGFR tyrosine kinase inhibitor on the efficacy of radioimmunotherapy has not been reported previously. This study investigated the effect of EGFR tyrosine kinase inhibition on the efficacy of radioimmunotherapy in a human cancer xenograft model. EXPERIMENTAL DESIGN: The humanized anti-Lewis Y antibody hu3S193 and the EGFR tyrosine kinase inhibitor AG1478 were studied. BALB/c nude mice were engrafted with A431 squamous carcinoma cells. Initial biodistribution properties of the 90Y-CHX-A''-DTPA-hu3S193 were evaluated in this model. In therapy experiments, cohorts of four to five xenografted mice were treated with saline as placebo, 0.4 mg AG1478 i.p. (six doses over 2 weeks), single i.v. injections of unlabeled hu3S193, or 90Y-CHX-A''-DTPA-hu3S193 (12.5, 25, 50, or 100 microCi). The combination of 0.4 mg AG1478 i.p. and 25 microCi 90Y-CHX-A''-DTPA-hu3S193 i.v. was subsequently evaluated in the A431 model. RESULTS: 90Y-CHX-A''-DTPA-hu3S193 retained excellent immunoreactivity after radiolabeling. The biodistribution study showed excellent uptake in tumor (90.33 +/- 38.84%ID/g) peaking at 24 to 72 hours after injection and with prolonged retention. 90Y-CHX-A''-DTPA-hu3S193 significantly inhibited A431 xenograft growth at 25, 50, and 100 microCi doses. The combination of 0.4 mg AG1478 with a single dose of 25 microCi 90Y-CHX-A''-DTPA-hu3S193 resulted in a significant enhancement of efficacy compared with either agent alone (P = 0.013). CONCLUSIONS: The efficacy of radioimmunotherapy with 90Y-CHX-A''-DTPA-hu3S193 is significantly enhanced by EGFR tyrosine kinase inhibitor AG1478. Further investigations of dosing regimens using EGFR tyrosine kinase inhibitors and radioimmunotherapy in the treatment of EGFR expressing tumors are warranted.

Phase I trial of 131I-huA33 in patients with advanced colorectal carcinoma.

PURPOSE: Humanized monoclonal antibody A33 (huA33) targets the A33 antigen which is expressed on 95% of colorectal cancers. A previous study has shown excellent tumor-targeting of iodine-131 labeled huA33 (131I-huA33). Therefore, we did a phase I dose escalation trial of 131I-huA33 radioimmunotherapy. EXPERIMENTAL DESIGNS: Fifteen patients with pretreated metastatic colorectal carcinoma each received two i.v. doses of 131I-huA33. The first was an outpatient trace-labeled "scout" dose for biodistribution assessment, followed by a second "therapy" dose. Three patients were treated at 20, 30, and 40 mCi/m2 dose levels, and six patients at 50 mCi/m2 to define the maximum tolerated dose. RESULTS: Hematologic toxicity was 131I dose-dependent, with one episode of grade 4 neutropenia and two episodes of grade 3 thrombocytopenia observed at 50 mCi/m2. The maximum tolerated dose was determined to be 40 mCi/m2. There were no acute infusion-related adverse events, and gastrointestinal toxicity was not observed despite uptake of 131I-huA33 in bowel. Seven patients developed pruritus or rash, which was not related to 131I dose. There was excellent tumor-targeting of 131I-huA33 shown in all patients. The serum T1/2beta of 131I-huA33 was (mean +/- SD) 135.2 +/- 46.9 hours. The mean absorbed tumor dose was 6.49 +/- 2.47 Gy/GBq. Four patients developed human anti-human antibodies. At restaging, 4 patients had stable disease, whereas 11 patients had progressive disease. CONCLUSION: Radioimmunotherapy using 131I-huA33 shows promise in targeting colorectal tumors, and is deliverable at a maximum tolerated dose of 40 mCi/m2. Further studies of 131I-huA33 in combination with chemotherapy are planned.

Immunological effects of chimeric anti-GD3 monoclonal antibody KM871 in patients with metastatic melanoma.

We conducted an open label dose-escalation phase I trial of chimeric anti-GD3 mAb KM871 in patients with metastatic melanoma. Patients were entered into one of five dose levels (1, 5, 10, 20, and 40 mg/m2) and received three infusions of KM871 at 2-wk intervals. A metastatic melanoma site was biopsied at day 7-10. Pharmacokinetics, immune function, and mechanism of action of KM871 were analysed. A total of 17 patients were entered into the trial; 15 were evaluable. KM871 had a serum half-life (T1/2-beta) based on ELISA of 10.39 +/- 1.12 d (mean +/- SD). Trough levels >1.0 microg/mL KM871 at 2 wk postinfusion were seen with the 10 mg/m2 and higher dose levels. There were no significant changes in white blood cell subsets or serum complement levels during KM871 treatment. KM871 was stable in vivo and maintained binding affinity and complement-dependent cytotoxicity (CDC) function up to 2 wk postinfusion. No significant trends in CDC or antibody-dependent cellular-cytotoxicity (ADCC) activity in patients were observed during treatment. Analysis of tumour biopsies demonstrated a significant increase in CD4+ T cell infiltrates compared to control patient tumours (P = 0.010), and in patients with either stable disease (2 patients) or a clinical partial response (1 patient) at restaging, a significant increase in CD3 and CD4 infiltrates in tumour over nonresponding patients was observed. The favourable immune properties of KM871, combined with this preliminary clinical data, indicate that KM871 has potential for the treatment of metastatic melanoma.