Joseph An2LTBCellHuMAbMouse

Ipilimumab

Flow Diagram of Ipilimumab Production

Ipilimumab is an antibody approved to be used as a novel immunotherapeutic against unresectable or metastatic melanoma. Ipilimumab is more commonly known to the public as Yervoy and is manufactured by Bristol-Myers Squibb.[endnoteRef:1] The cost of an Ipilimumab treatment course is around $120,000, averaging $30,000 per injection.[endnoteRef:2] [1: Bristol-Myers Squibb. 2015. Highlights of Prescribing Information [Internet]. Princeton (NJ): Bristol-Myers Squibb: c2013 [revised 2015 Aug]. Available from: http://packageinserts. bms.com/pi/pi_yervoy.pdf] [2: Fellner C. 2012. Ipilimumab (Yervoy) Prolongs Survival in Advanced Melanoma. Pharmacy and Therapeutics 37(9): 503-511, 530.]

Anti-CTLA-4 antibodies are made by injecting heat-inactivated Staphyloccocus aureus (or another cell line) constitutively expressing CTLA-4 immunoglobulin into HuMAb mice. These mice have had their immunoglobulin genes replaced with human genes. Secondary lymphoid tissues (2LTs) were harvested to isolate lymphocytes, of which B cells are of focus. Lymphocytes were fused with melanoma cells to form hybridoma/transfectoma cells. Fusion cells that successfully secrete anti-CTLA-4 immunoglobulin were selected through a stringent process of positive and negative selection. These selected hybridoma cells were able to efficiently produce monoclonal anti-CTLA-4 antibodies.[endnoteRef:3],[endnoteRef:4] [3: Krummel MF, Allison JP. 1995. CD28 and CTLA-4 Have Opposing Effects on the Response of T Cells to Stimulation. Journal of Experimental Medicine 182:459-465. ] [4: Hoos A, Ibrahim R, Korman A, et al. 2010. Development of Ipilimumab: Contribution to a New Paradigm for Cancer Immunotherapy. Seminars in Oncology 37(5):533-546.] Fully Human IgG1K Antibody

Normally, CTLA-4 binds to the B7 receptors (CD86/80) expressed on antigen-presenting cells (APCs). This high-affinity binding prevents CD28 expressed on T cells from binding to the B7 receptors. CD28 signaling is required for co-stimulation of the T lymphocyte in conjunction with TCR-complex stimulation. In particular, upregulation of IL-2 expression and secretion would occur, promoting cell proliferation.[endnoteRef:5],[endnoteRef:6] Hence, CTLA-4 works to dampen excess proliferation of activated T cells that may otherwise result in dangerous hyperactivity of the humoral response. Ipilimumabs effect is mediated by its selective binding to CTLA-4 on activated T cells and preventing its minding to its substrates, thereby releasing the brakes on a negative regulatory mechanism on T cells. In relevance to melanoma, the cancer that ipilimumab is approved to treat, CTLA-4 blocking allows for the amplification of anti-tumor activity of effector T cells.i Ipilimumab (commercially as Yervoy) was shown to result in a median overall survival rate of 10 months compared to the control group, which had a rate of 6 months.[endnoteRef:7] [5: Shapiro VS,. Truitt KE, Imboden JB, Weiss A. 1997. CD28 Mediates Transcriptional Upregulation of the Interleukin-2 (IL-2) Promoter through a Composite Element Containing the CD28RE and NF-IL-2B AP-1 Sites. Molecular and Cellular Biology 17(7): 4051-4058.] [6: Toyooka K, Maruo S, Iwahori T. 1996. CD28 co-stimulatory signals induce IL-2 receptor expression on antigen-stimulated virgin T cells by an IL-2-independent mechanism. International Immunology 8(2): 159-169. ] [7: Bristol-Myers Squibb. 2015. Clinical Trial Results [Internet]. Princeton (NJ): Bristol-Myers Sqsuibb: c2015. Available from: http://yervoy.com/clinical-trial-results ]

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