Up to now there have been no effective treatments that can get rid of the coronavirus that causes infection. Yesterday there was an announcement in the UK that a trial had started of a promising new drug – which is a ‘monoclonal antibody’. In this post I discuss the science behind this drug, what the current situation is and what are the prospects for its future success.
- As widely discussed in this blog, one of the keys to successful treatment of Covid-19 is blocking with antibodies the spike protein that the virus uses to get into our cells
- Following infection, affected people develop antibodies naturally, which do wane over time but hopefully will protect against a subsequent infection
- Indeed, some patients, who have been very ill, produce large amounts of antibodies and have been giving donations of their plasma, which can then be used to treat seriously ill patients
- This is a labour intensive and costly procedure, and cannot easily be scaled up for mass use. It is also not clear how effective it is in the most ill patients
- The vaccines that are being developed also aim to stimulate the body to produce natural antibodies that will provide protection; but again the time it takes for the antibody response means that vaccines cannot be used as a treatment.
- The obvious next step is to produce the antibody as ‘a drug’ which can be injected into patients when they become ill or even are known to have had contact with the virus
- Antibodies can now be manufactured for use in this way and are referred to as monoclonal antibodies. The ‘monoclonal’ means that they are very ‘pure’ and have very specific targets
- These manufactured antibodies can be more powerful than natural antibodies
Is this a new technology?
- Absolutely not!
- There are a vast number of monoclonal antibodies manufactured and used by millions of patients worldwide
- They have transformed the treatment of many cancers and also immune disorders such as rheumatoid arthritis
- Indeed, one of the world’s largest selling drugs is adalimumab, used to treat rheumatoid arthritis, which has annual global sales of $20 billion
- I helped lead a worldwide effort to examine the safety of these drugs following their introduction in around 2000
What is the technology for Covid-19?
- The US biotech company Regeneron has produced two monoclonal antibodies against the spike protein and combined them as REGN-COV2 – a dual antibody cocktail
- This is an interesting design approach, and makes sense as proteins are complex structures so there are several places one can select for an antibody to attach itself.
- In animal studies the Regeneron cocktail was successful in reducing the level of virus, and the severity of pneumonia, in affected monkeys, but did not completely eliminate the pneumonia
- Other companies are also working to develop further monoclonals, including the UK’s AstraZeneca (which is also producing the Oxford vaccine)
The clinical trial programme
- Regeneron has started two trials in the USA
- These trials will assess the safety, how well the injection is tolerated and how it affects outcome in patients with Covid-19
- Interestingly one of these trials is also recruiting people who are asymptomatic but who have the virus – presumably to see if the injection prevents them becoming ill
- Yesterday (September 14th) it was announced that the UK study of different treatments for Covid-19 in hospitalised patients – The Recovery Trial – would also start researching whether this antibody cocktail works
Should we get excited?
- The technology has been incredibly successful in cancers and other diseases, so obviously worth trying in Covid-19
- We don’t know yet if these (or indeed other) monoclonals will be effective in stopping the disease and at which stage they should be used
- We also don’t know whether one dose will be enough (the Regeneron trials are only of a single shot)
- There may be significant side effects – though other monoclonal drugs are generally safe and well tolerated
- They are not cheap to produce. It is a complete guess but, based on other monoclonal drugs, a single shot might cost £1000.
- The challenge will be therefore finding the appropriate target group:
- It will be too expensive and difficult to produce in sufficient quantities to give to asymptomatic people
- It might not be effective to give it when people are already quite ill with pneumonia
- Development of this antibody cocktail is welcomed and might be the best hope of a truly effective anti-viral drug for Covid-19
- At this stage we need to be realistic as to what contribution we can expect it to make to reducing the impact of the epidemic
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