Pharmacokinetics, immunogenicity and bioactivity of the therapeutic antibody catumaxomab intraperitoneally administered to cancer patients.

AIMS: Catumaxomab is the first EMEA approved trifunctional anti-EpCAMxanti-CD3 antibody for the treatment of cancer patients with malignant ascites. A phase II pharmacokinetic study was conducted to determine local and systemic antibody concentrations and anti-drug antibody (ADA) development. METHODS: Thirteen cancer patients with symptomatic malignant ascites were treated with four ascending doses of 10, 20, 50, and 150 microg catumaxomab intraperitoneally (i.p.) infused on days 0, 3, 6 or 7 and 10. The pharmacokinetics of catumaxomab were studied by implementation of supportive data from a non clinical mouse tumour model. Additionally, ADA development was monitored. RESULTS: Ten out of 13 patients were evaluable for pharmacokinetic analysis. Catumaxomab became increasingly concentrated in ascites during the course of treatment, attaining effective concentrations in the ng ml(-1) range. Catumaxomab remained immunologically active even after several days in the circulation. The observed systemic catumaxomab exposure was low (<1%), with a maximal median plasma concentration (C(max)) of 403 pg ml(-1). The mean elimination half-life in the plasma was 2.13 days. All patients developed ADA, but not before the last infusion. High observed inter-individual variability and low systemic exposure may be explained by the inverse correlation between tumour burden, effector cell numbers and systemic antibody bioavailability as demonstrated in a defined mouse tumour model. CONCLUSIONS: Based on the high and effective local concentrations, low systemic exposure and acceptable safety profile, we confirmed that the i.p. application scheme of catumaxomab for the treatment of malignant ascites is appropriate.

Methylation analysis of several tumour suppressor genes shows a low frequency of methylation of CDKN2A and RARB in uveal melanomas.

We have investigated the frequency of methylation of several tumour suppressor genes in uveal melanoma. As the loss of one copy of chromosome 3 (monosomy 3), which is found in about half of these tumours, is tightly associated with metastatic disease, a special emphasis was laid on genes located on this chromosome, including the fragile histidine triad (FHIT), von Hippel-Lindau (VHL), beta-catenin (CTNNB1), activated leukocyte cell adhesion molecule (ALCAM) and retinoic acid receptor-beta2 (RARB) genes. In addition, the methylation patterns of the CpG-rich regions 5' of the E-cadherin (CDH1), p16/cyclin-dependent kinase inhibitor 2 A (CDKN2A) and retinoblastoma (RB1) genes were analysed by bisulphite genomic sequencing or methylation-specific PCR (MSP). Furthermore, the SNRPN and D15S63 loci, which are located in the imprinted region of chromosome 15, were included in the study. Aberrant methylation was detected in nine of 40 tumours analysed: The imprinted SNRPN and D15S63 loci were hypermethylated in three tumours, all of which retained both copies of chromosome 3. Methylated RARB alleles were detected in three tumours, whereas in three other tumours CDKN2A was found to be methylated. As we did not find RARB and CDKN2A preferentially methylated in tumours with monosomy 3, which is a significant predictor of metastatic disease, we suggest that these genes may play a causative role in the formation of uveal melanoma but not in the development of metastases.