ABSTRACT
INTRODUCTION: Serine proteases are involved in many normal metabolic processes but also contribute to diseases of several organ systems, including viral and gastrointestinal diseases and oncology. Upamostat is an orally bioavailable prodrug of WX-UK1, which is most active against trypsins and closely related enzymes. AREAS COVERED: Research over the past two decades suggests several diseases in the three areas noted above which upamostat may be active. Upamostat has been studied clinically against several cancers and for outpatient treatment of COVID-19. Preclinical and clinical pharmacokinetic and metabolism studies demonstrate good bioavailability, sustained tissue levels, and high concentrations of the active moiety, WX-UK1, in stool, potentially important for treatment of gastrointestinal diseases. Clinical studies suggest activity against SARS-CoV-2; results against pancreatic cancer are also encouraging, though studies in both indications are not definitive. The drug was very well tolerated for periods of 2 weeks to several months. EXPERT OPINION: Upamostat is an orally bioavailable serine protease inhibitor with an excellent safety profile and favorable pharmacokinetic properties. It has demonstrated preliminary evidence of efficacy against COVID-19, and nonclinical data suggest potential applicability against other viral illnesses, gastrointestinal diseases, and cancer.
Subject(s)
COVID-19 , Gastrointestinal Diseases , Humans , Serine Proteinase Inhibitors/pharmacology , Antiviral Agents/adverse effects , Protease InhibitorsABSTRACT
Methotrexate (MTX) in the form of a gamma-cysteinylglycine derivative was disulfide linked to a monoclonal antibody reactive with the human transferrin receptor to give an antibody-MTX conjugate (anti-TfR-MTX). Antibody directed delivery of MTX to cell surface receptors was readily detected by flow cytometry using an anti-MTX antibody plus a secondary fluorescent antibody probe. Despite the presence of ample drug on the cell membrane, the conjugate alone was not cytotoxic over the course of several days. Expression of specific toxic activity, however, was obtained in conjunction with the carboxylic ionophore monensin, in whose presence anti-TfR-MTX displayed an IC50 of 8 X 10(-8) M. These results suggest that the ionophore causes antibody-drug conjugate to bypass the normal transferrin receptor cyclic pathway, allowing sufficient drug to reach, bind to, and inactivate intracellular dihydrofolate reductase.
Subject(s)
Disulfides , Immunotoxins/pharmacology , Methotrexate/pharmacology , Monensin/pharmacology , Receptors, Transferrin/immunology , Antibodies, Monoclonal , Cell Membrane/metabolism , Cell Survival/drug effects , Drug Interactions , Flow Cytometry , Fluorescent Antibody Technique , Folic Acid Antagonists , Humans , Immunotoxins/metabolism , Methotrexate/administration & dosage , Methotrexate/metabolism , Receptors, Transferrin/metabolism , Tumor Cells, CulturedABSTRACT
Ricin A chain, a potent ribosomal poison, was disulfide linked either to the iron transport protein, transferrin, or to anti-transferrin receptor antibodies to produce highly specific derivative toxins, Tf-A and TfR-A, respectively. The ability of these agents to gain access to and damage ribosomes within the cell was accelerated in the presence of carboxylic ionophores. Their effectiveness for killing clonogenic target cells was correspondingly enhanced by 5 logs after a brief treatment with Tf-A plus ionophore. Intracellular trafficking of Tf-A and TfR-A was monitored by a variety of methods to better understand their mechanism of action. Data obtained with 125I-labeled A chain and 59Fe3+-labeled toxin probes indicated that the natural iron delivery pathway was initially followed. This was characterized by specific attachment to surface receptors, internalization, entry into low-density acidic vesicles, uncoupling of iron, an absence of lysosomal degradation, and sustained cycling. Ultrastructural studies using a colloidal gold-labeled anti-A chain probe confirmed the presence of these toxins within the structural elements associated with endocytosis. Toxic Tf-A molecules, however, diverged from this pathway (t1/2 = 88 min) to eventually kill cells as witnessed by a gradual loss in the ability to rescue cells using excess transferrin. Potentiating agents, such as carboxylic ionophores or B chain, seem to act by speeding the divergence of Tf-A and TfR-A from the normal endocytotoxic cycle.
