Rapid conjugation of antibodies to toxins to select candidates for the development of anticancer Antibody-Drug Conjugates (ADCs)

Abstract

Antibody-Drug conjugates (ADcs) developed as a targeted treatment approach to deliver toxins directly to cancer cells are one of the fastest growing classes of oncology therapeutics, with eight ADCs and two immunotoxins approved for clinical use. However, selection of an optimum target and payload combination, to achieve maximal therapeutic efficacy without excessive toxicity, presents a significant challenge. We have developed a platform to facilitate rapid and cost-effective screening of antibody and toxin combinations for activity and safety, based on streptavidin-biotin conjugation. For antibody selection, we evaluated internalization by target cells using streptavidin-linked antibodies conjugated to biotinylated saporin, a toxin unable to cross cell membranes. For payload selection, we biotinylated toxins and conjugated them to antibodies linked to streptavidin to evaluate antitumour activity and pre-clinical safety. As proof of principle, we compared trastuzumab conjugated to emtansine via streptavidin-biotin (Trastuzumab-SB-DM1) to the clinically approved trastuzumab emtansine (T-DM1). We showed comparable potency in reduction of breast cancer cell survival in vitro and in growth restriction of orthotopic breast cancer xenografts in vivo. Our findings indicate efficient generation of functionally active ADcs. this approach can facilitate the study of antibody and payload combinations for selection of promising candidates for future ADc development. Antibody-Drug Conjugates (ADCs) combine the high specificity of antibodies for their target antigens with the cytotoxic effects of payloads to more specifically guide toxic agents towards cancer cells 1. The field of ADCs has been undergoing significant expansion since the first agent gemtuzumab ozogamicin (Mylotarg), targeting CD20-expressing B cell lymphomas, was approved by the Food and Drug Administration (FDA) in 2000 2. However, despite the potential for this therapeutic modality and the launch of many clinical studies, attrition rates are high due to several challenges such as low efficacy and "on-target" toxicity on normal cells. Until now, only eight ADCs along with two immunotoxins have been approved by the regulatory agencies 1. In order to improve

Success of prophylactic antiviral therapy for SARS-CoV-2: Predicted critical efficacies and impact of different drug-specific mechanisms of action

“…This would describe the effect of SARS-CoV-2 specific antibodies that bind to infected cells and induce antibody-dependent cellular cytoxicity or antibody-dependent cellular phagocytosis. It would also model immunomodulatory drugs that stimulate cell-mediated immune responses, or immunotoxins such as antibody toxin conjugates that can directly kill cells [ 51 ].…”

Predicted success of prophylactic antiviral therapy to block or delay SARS-CoV-2 infection depends on the drug’s mechanism of action

“…This would describe the effect of SARS-CoV-2 specific anti-bodies that bind to infected cells and induce antibody-dependent cellular cytoxicity or antibody-dependent cellular phagocytosis. It would also model immunomodulatory drugs that stimulate cell-mediated immune responses, or immunotoxins such as antibody toxin conjugates that can directly kill cells (Hoffmann et al, 2020).…”

A quantitative model used to compare within-host SARS-CoV-2, MERS-CoV, and SARS-CoV dynamics provides insights into the pathogenesis and treatment of SARS-CoV-2

“…This could be done by stimulating adaptive immunity, including responses mediated by cytotoxic T lymphocytes and natural killer cells, by immunotherapy or vaccination, but the PLOS BIOLOGY effect would not be immediate. To be consistent with the other modes of drug action discussed above, in which we assume the drug takes effect immediately after administration, we envision a drug such as a viral-specific monoclonal antibody conjugated to a toxin, as used in cancer therapy [33], or a non-neutralizing viral-specific monoclonal antibody that could induce infected cell death by complement-mediated lysis or antibody-dependent cellular cytotoxicity. A neutralizing antibody with these effector functions could be considered the equivalent of combination therapy, which is discussed below.…”