Quantitative characterization of in vitro bystander effect of antibody-drug conjugates.
Antibody-drug conjugates (ADCs) are designed to target antigen expressing (Ag+) cells in a tumor. Once processed by the Ag+ cells, ADCs can release cytotoxic drug molecules that can diffuse out of Ag+ cells into the neighboring antigen-negative (Ag-) cells to induce their cytotoxicity. This additional efficacy of ADCs on Ag- cells in the presence of Ag+ cells is known as the 'bystander effect'. Although the importance of this phenomena is widely acknowledged for effective killing of a heterogeneous tumor, the rate and extent of the bystander killing in a heterogeneous system is not quantitatively understood yet. Thus, the objectives of this manuscript were to: (1) synthesize and characterize a tool ADC Trastuzumab-vc-MMAE that is capable of exhibiting bystander effect, (2) quantify the time course of the bystander effect for the tool ADC using in vitro co-culture systems created using mixture of various HER2-expressing cell lines, and (3) develop a pharmacodynamic (PD) model that is capable of characterizing the bystander effect of ADCs. Co-culture studies conducted using GFP labelled MCF7 cells as Ag- cells and N87, BT474, and SKBR3 as Ag+ cells revealed that the bystander effect of ADC increases with increasing fraction of Ag+ cells in a co-culture system, and with increased expression level of target on Ag+ cells. A notable lag time after ADC incubation was also observed prior to significant bystander killing of Ag- cells. Based on our results we hypothesize that there may be other determinants apart from the antigen expression level that can also influence the ability of Ag+ cells to demonstrate the bystander effect in a co-culture system. The co-culture analysis also suggested that the bystander effect of the ADC can dissipate over the period of time as the population of Ag+ cells declines. A novel PD model was developed to mathematically characterize the bystander effect of ADCs by combining two different cell distribution models to represent the population of Ag+ and Ag- cells in a co-culture system. This PD model can be integrated with the systems PK model for ADCs in the future to generate a quantitative framework that is capable of supporting the discovery and development of novel ADCs with optimal bystander killing capabilities.
Department of Pharmaceutical Sciences, School of Pharmacy and Pharmaceutical Sciences, The State University of New York at Buffalo, 455 Kapoor Hall, Buffalo, NY, 14214-8033, USA.
Aman P
AP
Singh
Department of Pharmaceutical Sciences, School of Pharmacy and Pharmaceutical Sciences, The State University of New York at Buffalo, 455 Kapoor Hall, Buffalo, NY, 14214-8033, USA.
Sharad
S
Sharma
Department of Pharmaceutical Sciences, School of Pharmacy and Pharmaceutical Sciences, The State University of New York at Buffalo, 455 Kapoor Hall, Buffalo, NY, 14214-8033, USA. dshah4@buffalo.edu.
Dhaval K
DK
Shah
D000911:Antibodies, Monoclonal / Q000737:chemistry / Q000494:pharmacology*; D000951:Antigens, Neoplasm / Q000235:genetics / Q000378:metabolism*; D000970:Antineoplastic Agents / Q000737:chemistry / Q000494:pharmacology*; D024201:Bystander Effect / Q000187:drug effects*; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D018920:Coculture Techniques; D049452:Green Fluorescent Proteins / Q000235:genetics; D006801:Humans; D018796:Immunoconjugates / Q000737:chemistry / Q000494:pharmacology*; D061986:MCF-7 Cells; D008954:Models, Biological; D009842:Oligopeptides / Q000138:chemical synthesis / Q000494:pharmacology*; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000235:genetics; D013997:Time Factors; D000068878:Trastuzumab / Q000494:pharmacology*
D000911:Antibodies, Monoclonal; D000951:Antigens, Neoplasm; D000970:Antineoplastic Agents; D049452:Green Fluorescent Proteins; D018796:Immunoconjugates; D009842:Oligopeptides; D018719:Erb-b2 Receptor Tyrosine Kinases; D000068878:Trastuzumab; C000624252:trastuzumab-vc-MMAE; C508053:ERBB2 protein, human
Antibody–drug conjugates; Bystander effect; Co-culture system; Pharmacodynamic modeling; Tumor heterogeneity
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