Anti-Human CD33 (Gemtuzumab)

Humanized antibody derived from mouse clone P67.6

This biosimilar antibody is aseptically packaged and formulated in 0.01 M phosphate buffered saline (150 mM NaCl) PBS pH 7.2 - 7.4 with no carrier protein, potassium, calcium or preservatives added. Due to inherent biochemical properties of antibodies, certain products may be prone to precipitation over time. Precipitation may be removed by aseptic centrifugation and/or filtration.

Liquid

Recombinant biosimilar antibodies are manufactured in an animal free facility using only in vitro protein free cell culture techniques and are purified by a multi-step process including the use of protein A or G to assure extremely low levels of endotoxins, leachable protein A or aggregates.

To protect mouse colonies from infection by pathogens and to assure that experimental preclinical data is not affected by such pathogens, all of Leinco’s recombinant biosimilar antibodies are tested and guaranteed to be negative for all pathogens in the IDEXX IMPACT I Mouse Profile.

Functional grade biosimilar antibodies may be stored sterile as received at 2-8°C for up to one month. For longer term storage, aseptically aliquot in working volumes without diluting and store at -80°C. Avoid Repeated Freeze Thaw Cycles.

Research Use Only

2-8°C Wet Ice

This non-therapeutic biosimilar antibody uses the same variable region sequence as the therapeutic antibody Gemtuzumab but is not covalently linked to Calich-DMH. Gemtuzumab antibody activity is directed against CD33.

CD33 is a sialic-acid-binding immunoglobulin-like lectin (Siglec) that acts as an endocytic receptor¹. CD33 is considered an attractive target for conjugated antibody chemotherapeutic development in patients with acute myeloid leukemia (AML) because ~90% of patients express CD33 surface antigen on myeloid blast cells, but not normal stem cells², and additionally CD33 is rapidly internalized when bound³.

N-acetyl-γ-calicheamicin is a potent, natural cytotoxic agent produced by Micromonospora echinospora that induces double-strand DNA breaks and apoptosis in rapidly proliferating cells, independent of cell cycle progression, and is therefore also of interest as a chemotherapeutic agent^{3, 4}. The semisynthetic derivative N-acetyl-γ-calicheamicin dimethyl hydrazide (Calich- DMH; calicheamicin) is used as an enediyne antitumor antibiotic in CD33-based chemotherapy³.

Gemtuzumab is an antibody-drug conjugate composed of Calich-DMH attached via acetyl butyrate linker to hP67.6, an anti-CD33 antibody humanized from its murine progenitor by CDR grafting³. The conjugate contains a lysine attachment to the antibody as well as a hydrazone linkage which allows for hydrolytic release. When Gemtuzumab binds CD33-expressing tumor cells, the Gemtuzumab-CD33 complex is rapidly internalized and the acidic intracellular environment (presumably in the endosomes/lysosomes of target cells) triggers the release of Calich-DMH. Calich-DMH then binds to the minor groove of DNA, undergoes a structural change in its enediyne moiety that generates diradicals, and induces double-strand DNA breakage, cell cycle arrest and apoptosis^{3, 4, 5}. Gemtuzumab temporarily arrests NB4 cells, but not clinical samples, at the G2/M phase and increases the percentage of hypodiploid cells in cell lines as well as clinical samples^{5, 6, 7}. Gemtuzumab has a drug loading capacity of 2-3 mol of Calich-DMH per mole of antibody³. However, the effects of Gemtuzumab are negatively influenced by P-glycoprotein⁶.

Gemtuzumab has been approved for treatment of some patients with relapsed acute myeloma who are aged 60 and over².

CD33 is expressed on normal multipotent myeloid precursor cells, unipotent colony-forming cells, maturing granulocytes and monocytes, macrophages, dendritic cells, and can be displayed on subsets of B cells, activated T cells and natural killer cells. CD33 is also expressed on the surface of leukemic cell blasts in more than 90% of patients with acute myeloid leukemia, but is not present on normal stem cells.

sialic acid residues

1 Clark MC, Stein A. Best Pract Res Clin Haematol. 33(4):101224. 2020.
2 McGavin JK, Spencer CM. Drugs. 61(9):1317-1322; discussion 1323-4. 2001.
3 Hamann PR, Hinman LM, Hollander I, et al. Bioconjug Chem. 13(1):47-58. 2002.
4 Thota S, Advani A. Eur J Haematol. 98(5):425-434. 2017.
5 Naito K, Takeshita A, Shigeno K, et al. Leukemia. 14(8):1436-1443. 2000.
6 Matsui H, Takeshita A, Naito K, et al. Leukemia. 16(5):813-819. 2002.
7 Takeshita A, Shinjo K, Naito K, et al. Leukemia. 19(8):1306-1311. 2005.
8 Larson RA, Sievers EL, Stadtmauer EA, et al. Cancer. 104(7):1442-1452. 2005.