Narrow Therapeutic Window of Ribavirin as an Inhibitor of Nitric Oxide Synthesis is Broadened by Macromolecular Prodrugs

Abstract

Ribavirin (RBV), a broad-spectrum antiviral agent, is a standard medication against hepatitis C virus (HCV). However, despite the decades of clinical success, the mechanism of action of this drug against HCV remains a subject of debate. Furthermore, the appeal of this therapeutic agent is considerably lessened by unfavorable pharmacokinetics. This interdisciplinary study contributes to the understanding of intracellular effects exerted by RBV and presents a successful design of macromolecular prodrugs of RBV to achieve a safer treatment. Specifically, we demonstrate that RBV exhibits a pronounced anti-inflammatory activity in cultured macrophages as is evidenced by a 2-fold decrease in the levels of produced nitric oxide achieved using a clinically relevant concentration of this drug. However, this effect was characterized by a rather narrow therapeutic window with experimental values of EC50 and IC50 being 7 and 19 μM, respectively. Macromolecular prodrugs were obtained using an acrylate derivative of RBV, RAFT polymerization technique, and N-vinyl pyrrolidone as a partner monomer. The synthesized polymers were characterized with uniform molecular weights, relatively narrow polydispersities, and gradually increasing content of RBV. The resulting polymer therapeutics were effective in delivering their payload to the cultured macrophages and afforded a significantly wider therapeutic window, as much as >1000 μM (18-fold in relative values). Taken together, this work contributes significantly to the development of safer methods for delivery of RBV, as well as understanding the mechanism of action and origins of the side effects of this broad-spectrum antiviral agent.

Highly Active Macromolecular Prodrugs Inhibit Expression of the Hepatitis C Virus Genome in the Host Cells

“…In contrast and in accordance with the ineffectiveness of RBV mono‐therapy in the clinic, RBV revealed an EC 50 value of 80 × 10 −6 m (see Figure S5, Supporting Information). This concentration is markedly higher than the toxicity associated IC 50 value of RBV established in macrophages (mimics to the liver resident Kupffer cells). Furthermore, this concentration is much higher than the therapeutically relevant content of the drug in patients' plasma (6–20 × 10 −6 m ) .…”

“…The therapeutic effect associated with the designed MP was quantified in a hepatitis C virus subgenomic replicon system (Figure S3, Supporting Information) hosted within a hepatocyte cell lineage . Previous reports on MP of RBV analyzed toxicity or anti‐inflammatory activity of the released drug (in vitro) or quantified viral titer in blood (in vivo) . To the best of our knowledge, we present the first direct characterization of MP in their capacity to interfere with the proliferation of HCV as measured within the cells hosting infection.…”

Nitric oxide in liver diseases

“…Potential mechanisms of ribavirin's anti-HCV activity are through its anti-angiogenic [95] and anti-inflammatory [96] properties. Ribavirin was shown to inhibit endothelial cell proliferation, endothelial cell tube formation, and vessel formation by decreasing eNOS-derived NO through a sequence of events (decreased intracellular guanosine-5′-triphosphate (GTP) and decreased cofactor tetrahydrobiopterin (BH4)) initiated by the inhibition of intracellular inosine-5′-monophosphate dehydrogenase.…”

“…Ribavirin was shown to inhibit endothelial cell proliferation, endothelial cell tube formation, and vessel formation by decreasing eNOS-derived NO through a sequence of events (decreased intracellular guanosine-5′-triphosphate (GTP) and decreased cofactor tetrahydrobiopterin (BH4)) initiated by the inhibition of intracellular inosine-5′-monophosphate dehydrogenase. In cultured macrophages (RAW264.7), ribavirin also inhibited iNOS-derived NO, suggesting its anti-inflammatory activity [96]. However, use of ribavirin may need caution.…”

Replication of Equine arteritis virus is efficiently suppressed by purine and pyrimidine biosynthesis inhibitors

“…Interestingly, one of the most studied BSA is ribavirin which has been described as an inhibitor of porcine reproductive and respiratory syndrome virus (PRRSV) and porcine epidemic diarrhea virus (PEDV) 14 , two nidoviruses closely related to EAV. In vivo , ribavirin is used for treating humans or animals infected with emerging viruses such as Lassa virus or Hantavirus for which therapeutic options are limited 15-18 15,19-21 . Ribavirin is a synthetic analog of guanosine that interferes with viral replication through multiple direct and indirect mechanisms.…”