In a study in mammalian cells, an extract from edible seaweeds was found to outperform remdesivir, in effectiveness against SARS-CoV-2 that causes Covid-19.
Heparin, a common blood thinner, and a heparin variant stripped of its anticoagulant properties, performed on par with remdesivir in inhibiting the virus.
The spike protein on SARS-CoV-2 latches onto the ACE-2 receptor on the surface of human cells. But in the study, the virus could be persuaded to lock onto a decoy molecule that offers a similar fit.
The neutralised virus would be trapped and eventually degrade naturally. Previous research has shown this decoy technique works in trapping other viruses, including dengue.
The new research tested antiviral activity in three variants of heparin (heparin, trisulfated heparin, and a non-anticoagulant low molecular weight heparin) and two extracts (RPI-27 and RPI-28) from seaweed.
With each compound, the researchers performed a dose-response study on mammalian cells. They compared a value called EC50 (a lower value signals a more potent compound).
RPI-27 yielded an EC50 value of about 83 nanomolar, while a similar previous test of remdesivir on the same mammalian cells yielded an EC50 of 770 nanomolar (RPI-27 was, therefore, more potent).
Heparin yielded an EC50 2.1 micromolar or about one-third as active as remdesivir, and a non-anticoagulant analogue of heparin yielded an EC50 of 5.0 micromolar, about one-fifth as active as remdesivir.