Many researchers around the world are looking for drugs to treat COVID-19, but no effective treatments have yet been discovered. However, there are promising leads. The new coronavirus is genetically very similar to the viruses that caused severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS), so medication used to treat these infections might be effective against COVID-19 too. Other established antiviral drugs could also work and these could be re-purposed to treat COVID-19. Any new drug must be tested in clinical trials – where it is investigated for safety in and efficacy in COVID-19 patients – before it goes to market. These are some of the approaches now being taken to develop treatments for COVID-19.
This drug was originally developed to treat the Ebola virus. Remdesivir was not as effective as other treatments for Ebola but, in laboratory experiments, it has been shown to reduce the coronavirus infection that causes MERS. The drug works by blocking an enzyme that is needed for the virus to replicate. Remdesivir has been safely used to treat other illnesses and could now be tested in COVID-19 patients.
This is a combination of two drugs – lopinavir and ritonavir – which is used to treat people with HIV infection. Both drugs work by preventing the virus from multiplying in the body. This treatment has been shown to act in a similar way for the SARS coronavirus. The use of lopinavir/ritonavir in SARS has previously shown positive results. One small trial of this drug combination found no benefit for the treatment of COVID-19, but the effectiveness of these drugs remains an open question.
Chloroquine phosphate is an old medicine used to treat malaria. Large scale screening of many existing medicines indicated it as a potentially promising candidate and its use is currently being trialled in China for treatment of COVID-19 related pneumonias. It might also be used in combination with remdesivir.
Interferons are naturally occurring proteins produced by human cells when they are infected with a virus. These proteins act as signals to other cells that heighten their antiviral defences. They can be artificially produced and given to patients. Several interferons are effective against the MERS coronavirus using cells in a laboratory but it is unclear how well they would work in humans.
This drug has been used to treat hepatitis C and severe respiratory syncytial virus (RSV). Ribavirin, combined with interferons, showed no clear benefit in a large trial against MERS coronavirus. The World Health Organisation is not pursuing ribavirin as a potential drug for COVID-19 because it could cause anaemia, a red blood cell deficiency. However, trials of ribavirin are taking place in China.
Plasma or immunoglobulin
SARS and also influenza (during the 2009 pandemic) have been treated using plasma taken from patients who have recovered from their infections. This is called convalescent plasma. Plasma is the liquid component of blood, which contains the antibodies that provide immunity to recovering patients. It must be made safe before it is given by infusion into a vein, using routine methods to ensure the inactivation of any potential viruses or other harmful agents that could be present. The protective antibody component of plasma, which is named immunoglobulin, can be purified and given intravenously instead of whole plasma as a treatment. This is known as intravenous immunoglobulin or IVIG. This has the advantage that it can be prepared in bulk from large pools of plasma collected from convalescent patients. Like plasma, IVIG is given by intravenous infusion but in a much smaller and more convenient volume compared with plasma.
Monoclonal antibodies (mAbs)
Antibodies are produced in the blood as part of the body’s immune response against a virus. Artificially produced antibodies can be made to match and bind to a virus exactly (mono-specifically), preventing it from entering cells. Several promising candidates already exist, and have shown favourable results in preliminary trials.
Drugs that are not effective or that make symptoms worse
Negative results – for example discovering which antivirals have no effect – are extremely important to avoid both patient harm and waste of effort. There have been suggestions that ibuprofen, an effective means of lowering temperature, should not be used to reduce fever as fever helps clear the virus from the body. There are also some suggestions that it may worsen symptoms in respiratory disease. The evidence remains unclear.