ALBERT

Description: Relapsed B-cell lymphomas are incurable with conventional chemotherapy and radiation therapy, although a fraction of patients can be cured with high-dose chemoradiotherapy and autologous stem-cell transplantation (ASCT). We conducted a phase I/II trial to estimate the maximum tolerated dose (MTD) of iodine 131 (131I)–tositumomab (anti-CD20 antibody) that could be combined with etoposide and cyclophosphamide followed by ASCT in patients with relapsed B-cell lymphomas. Fifty-two patients received a trace-labeled infusion of 1.7 mg/kg 131I-tositumomab (185-370 MBq) followed by serial quantitative gamma-camera imaging and estimation of absorbed doses of radiation to tumor sites and normal organs. Ten days later, patients received a therapeutic infusion of 1.7 mg/kg tositumomab labeled with an amount of131I calculated to deliver the target dose of radiation (20-27 Gy) to critical normal organs (liver, kidneys, and lungs). Patients were maintained in radiation isolation until their total-body radioactivity was less than 0.07 mSv/h at 1 m. They were then given etoposide and cyclophosphamide followed by ASCT. The MTD of131I-tositumomab that could be safely combined with 60 mg/kg etoposide and 100 mg/kg cyclophosphamide delivered 25 Gy to critical normal organs. The estimated overall survival (OS) and progression-free survival (PFS) of all treated patients at 2 years was 83% and 68%, respectively. These findings compare favorably with those in a nonrandomized control group of patients who underwent transplantation, external-beam total-body irradiation, and etoposide and cyclophosphamide therapy during the same period (OS of 53% and PFS of 36% at 2 years), even after adjustment for confounding variables in a multivariable analysis.

Description: Relapsed B-cell lymphomas are incurable with conventional chemotherapy and radiation therapy, although a fraction of patients can be cured with high-dose chemoradiotherapy and autologous stem-cell transplantation (ASCT). We conducted a phase I/II trial to estimate the maximum tolerated dose (MTD) of iodine 131 (131I)–tositumomab (anti-CD20 antibody) that could be combined with etoposide and cyclophosphamide followed by ASCT in patients with relapsed B-cell lymphomas. Fifty-two patients received a trace-labeled infusion of 1.7 mg/kg 131I-tositumomab (185-370 MBq) followed by serial quantitative gamma-camera imaging and estimation of absorbed doses of radiation to tumor sites and normal organs. Ten days later, patients received a therapeutic infusion of 1.7 mg/kg tositumomab labeled with an amount of131I calculated to deliver the target dose of radiation (20-27 Gy) to critical normal organs (liver, kidneys, and lungs). Patients were maintained in radiation isolation until their total-body radioactivity was less than 0.07 mSv/h at 1 m. They were then given etoposide and cyclophosphamide followed by ASCT. The MTD of131I-tositumomab that could be safely combined with 60 mg/kg etoposide and 100 mg/kg cyclophosphamide delivered 25 Gy to critical normal organs. The estimated overall survival (OS) and progression-free survival (PFS) of all treated patients at 2 years was 83% and 68%, respectively. These findings compare favorably with those in a nonrandomized control group of patients who underwent transplantation, external-beam total-body irradiation, and etoposide and cyclophosphamide therapy during the same period (OS of 53% and PFS of 36% at 2 years), even after adjustment for confounding variables in a multivariable analysis.

Description: Abstract 4307 The von Willebrand factor-cleaving protease, also known as ADAMTS13, is synthesized, in part, by endothelial cells (EC). We previously reported that proliferating EC secreted ∼3-fold more ADAMTS13 (antigen and activity) than confluent EC, and that this synthesis was transcriptionally regulated (SJ Kling et al, Pathophysiol Haemost Thromb 2008; 36: 233.) Thrombospondin domains, a defining feature of the ADAMTS protease family, in other ADAMTS family members mediate inhibition of angiogenesis. In particular, ADAMTS1 inhibits angiogenesis by sequestering vascular endothelial growth factor (VEGF) (A Luque et al, J Biol Chem, 2003; 278: 23656). Since ADAMTS13 also has thrombospondin domains, we hypothesized that ADAMTS13 might also mediate anti-angiogenic activity. Human umbilical vein EC angiogenesis was quantified by Angioquant analysis of fluorescence microscopy tube images in a Matrigel assay. Treatment of EC with inhibitors of angiogenesis (anti-VEGF, vasostatin) did not alter EC production of ADAMTS13. However, exogenous recombinant ADAMTS13 inhibited angiogenesis in a dose-dependent manner (Figure 1), in media containing VEGF. In VEGF-free media, ADAMTS13 had no effect on EC tube formation. Preincubation of ADAMTS13 with an antibody to the ADAMTS13 thrombospondin domains 5–7 partially reversed the inhibition of tube formation, implicating these domains in the anti-angiogenic interaction (Figure 2). We also found that VEGF co-immunoprecipitates with ADAMTS13, providing strong evidence that these two proteins interact. When EC lysates were crosslinked with DTSSP prior to immunoprecipitation, anti-ADAMTS13 immunoprecipitated as much VEGF as did anti-ADAMTS1, while an antibody to ADAM17, a similar protein that lacks thrombospondin domains, failed to co-immunoprecipitate VEGF (Figure 3). These data indicate that as with other ADAMTS family members, ADAMTS13 inhibits tubule formation - a parameter of angiogenesis – through its interaction with VEGF, an effect likely mediated by its thrombospondin domains. Inhibition of angiogenesis adds to the expanding roles of ADAMTS13 in down-regulation of thrombosis and inflammation. Fig. 1. Fig. 1. Fig. 2. Fig. 2. Fig. 3. An antibody to ADAMTS13 immunoprecipitates VEGF in similar amounts as anti-ADAMTS1 when proteins from HUVEC lysates are crosslinked prior to co-immunoprecipitation. Nonspecific IgG fails to immunoprecipitate VEGF, as does anti-ADAM17. (A1 = ADAMTS1; A13 = ADAMTS13) Fig. 3. An antibody to ADAMTS13 immunoprecipitates VEGF in similar amounts as anti-ADAMTS1 when proteins from HUVEC lysates are crosslinked prior to co-immunoprecipitation. Nonspecific IgG fails to immunoprecipitate VEGF, as does anti-ADAM17. (A1 = ADAMTS1; A13 = ADAMTS13) Disclosures: Fryer: American Diagnostica Inc: Employment. Greenfield:American Diagnostica Inc: Employment.