miR-122 inhibitor SPC3649 successfully inhibits HCV replication in chimps...

Posted 8/30/12 on Texas Biomed.org. Texas Biomedical Research Institute scientists in collaboration with Denmark's Santaris Pharma A/S have successfully inhibited HCV replication in chimpanzees using SPC3649, a DNA-based drug developed from Santaris's proprietary LNA ('Locked Nucleic Acid') technology. SPC3649 inhibits a host-based RNA molecule microRNA122 (miR-122) which HCV uses to replicate.  The drug is currently in phase II trials in humans and looks particularly compelling because of it's lack of any known side effects. 

Attacking the Silent Killer

Texas Biomed scientists have demonstrated that a new and novel class of drug targeting hepatitis C infections successfully inhibited replication of the virus in the liver of chimpanzees. The drug is now in phase two human clinical trials.

The drug was developed by the biopharmaceutical firm Santaris Pharma A/S in Denmark using its proprietary nucleic acid chemistry called “locked nucleic acid” or LNA. The drug, known as SPC3649, is a DNA-based drug that captures a small RNA molecule in the liver, called microRNA122 (miR-122) that is required for hepatitis C virus (HCV) replication.

“Our collaboration with Santaris Pharma proved that the drug worked exceptionally well in treating HCV infections in chimpanzees,” said Texas Biomed’s Robert E. Lanford, Ph.D., of the Department of Virology and Immunology. He was the lead author on the study appearing in the journal Science in January 2010.

One of the novel aspects of this drug is that it targets a host factor, miR-122, required by the virus, rather than directly targeting the virus itself. This helped prevent antiviral resistance, a major problem with therapies that directly target the virus.  Remarkably, this drug continued to work for several months after administration of the last dose.

The other novel aspect was the use of a DNA based therapy in what is called antisense technology. Antisense was supposed to be one of the “magic bullets” along with siRNA technology, but thus far no one has gotten them to work when systemically administered. Thus, this proof-of-concept study suggests that the LNA technology might also prove useful in using DNA based antisense drugs to treat many other diseases such as AIDS, cancer, and inflammatory diseases.

The study was conducted under a sponsored research grant to Texas Biomed. The primate studies were performed at Texas Biomed’s Southwest National Primate Research Center, which is supported by the National Institutes of Health.

HCV infections affect 170 million people worldwide and may progress over years to end-stage liver disease, including cirrhosis and liver cancer. In the United States, 4 percent of the adult population is chronically infected with HCV. The only U.S. FDA-approved therapy is pegylated-interferon and ribavirin, which is highly toxic, requires 48 weeks of treatment, and works in less than half of patients who are able to complete the full course of treatment. HCV infection is the leading reason for liver transplantation in the U.S, and HCV associated liver cancer is the most rapidly increasing cause of cancer death in the U.S.

Because it provides a high barrier to resistance, the new therapy could potentially replace interferon in future drug cocktails. “This antiviral could be used alone in long-term therapy to treat disease progression,” Lanford said. The new therapy may also be good to use after liver transplantation, because it may help suppress the replication of HCV in the new liver. The therapy has no known toxic or adverse reactions, and this is critical in the transplant setting.

In the study, four chimpanzees chronically infected with HCV were treated with the new antiviral drug. The two animals that received the higher dose had a reduction in virus levels in the blood and liver of approximately 350-fold. Additional surprising findings were the lack of antiviral resistant mutants and the fact that the therapy continued to work for several months after dosing stopped. An additional benefit of the drug was the reduction of total serum cholesterol by up to 45%, due to inhibition of the normal function of miR122 in cholesterol and fatty acid metabolism.

The new study was a critical proof of concept that the LNA technology could work for HCV. It proved that miR-122 is essential for HCV replication in an animal infected with HCV. Previously the role of miR-122 in HCV replication had only been shown in tissue culture. A second advance was the finding that LNA therapy could work against an important human disease in the chimpanzee model, suggesting that the new technology could be applied to other diseases.