Rituximab is an anti-CD20 chimeric mAb effective for the treatment of B-NHL. It can lyse lymphoma cells in vitro through both C- and Ab-dependent cellular cytotoxicity. The mechanism of action of rituximab in vivo is however still unclear. We have set up a new in vivo model in nonimmunodeficient mice by stable transduction of the human CD20 cDNA in the murine lymphoma line EL4. Animals injected i.v. with the EL4-CD20⁺ lymphoma cells died within 30 days with evident liver, spleen, and bone marrow involvement, confirmed by immunohistochemistry and PCR analysis. A single injection of rituximab or the murine anti-CD20 Ab 1F5, given i.p. 1 day after the tumor, cured 100% of the animals. Indeed, at week 4 after tumor cell inoculation, CD20⁺ cells were undetectable in all organs analyzed in rituximab-treated animals, as determined by immunohistochemistry and PCR. Rituximab had no direct effect on tumor growth in vitro. Depletion of either NK cells or neutrophils or both in tumor-injected animals did not affect the therapeutic activity of the drug. Similarly, rituximab was able to eradicate tumor cells in athymic nude mice, suggesting that its activity is T cell independent. In contrast, the protective activity of rituximab or the 1F5 Ab was completely abolished in syngeneic knockout animals lacking C1q, the first component of the classical pathway of C (C1qa^−/−). These data demonstrate that C activation is fundamental for rituximab therapeutic activity in vivo.

Summary: Gemtuzumab ozogamicin (GO) is a humanized anti‐CD33 antibody conjugated with the cytotoxic drug calicheamicin and approved for the treatment of relapsed acute myeloid leukaemia. As approximately 18% of acute lymphoblastic leukaemias (ALL) are also CD33 positive, we have investigated the cytotoxic activity of GO on CD33⁺ ALL cells in vitro and in vivo. 10 ng/ml GO induced 30–95% inhibition of thymidine uptake and 30–70% cell death in four freshly isolated and one in vivo passaged CD33⁺ ALL‐cell cultures. Furthermore, an in vivo model of a CD33⁺ ALL carrying the Philadelphia chromosome [t(9;22)] was established. 5 × 10⁶ ALL‐2 cells inoculated in the tail vein of severe combined immunodeficient mice engrafted into haematopoietic organs, reaching a mean of 70%, 61% and 69% human CD45⁺ cells in bone marrow, spleen and liver, respectively, at 35 d. To test the therapeutic activity of GO, 50 or 100 μg immunotoxin was inoculated i.p. on days 7, 11 and 15 following tumour‐cell inoculation. GO treatment dramatically inhibited expansion of ALL‐2 cells in all tested organs and increased survival of tumour‐injected animals by 28–41 d, relative to controls. These data demonstrated that GO is active both in vitro and in vivo against CD33⁺ ALL cells.

Article Glycated albumin: correlation to HbA1c and preliminary reference interval evaluation was published on February 1, 2017 in the journal Clinical Chemistry and Laboratory Medicine (CCLM) (volume 55, issue 2).