Monoclonal antibody cocktail: Glimmer of hope against Covid-19
As the city’s management and medical experts prepare for an anticipated third wave of Covid-19, an experimental drug has offered a glimmer of hope against the virus.
Known as monoclonal antibody cocktail, the drug’s response has been analysed in 199 patients who were admitted to Mumbai’s Seven Hills Hospital, and the findings are promising, say doctors. Their analysis underlined two important findings – persistent fever in patients resolved within 48 hours and the days of hospitalisation were reduced. This suggests that the drug could play a role in reducing the number of severe Covid-19 cases and thereby the fatality. More studies with larger sample sizes can provide a better understanding of the drug’s usefulness in the fight against Covid-19.
Here’s everything that we know about monoclonal antibodies and the drug cocktail.
What are monoclonal antibodies?
When our bodies are attacked by an infection caused by viruses or bacteria, they produce natural antibodies or proteins to fight back. These antibodies are crucial in our immune system’s defence mechanism. Monoclonal antibodies are similar to natural antibodies except that they are laboratory-made. They are designed to target a specific disease and are often referred to as ‘designer antibodies’.
Monoclonal antibodies have been widely used in cancer and autoimmune diseases. A 2020 review published in the Journal of Biomedical Science stated that antibody engineering has evolved dramatically since the first monoclonal antibody was approved by the US Food and Drug Administration in 1986 and over the past five years, antibodies have become the best-selling drugs in the pharmaceutical market worldwide.
Monoclonal antibody cocktail drug used for Covid-19
A monoclonal antibody cocktail drug is a combination of two or more monoclonal antibodies that are administered to patients. Last November, the US FDA issued an emergency use authorisation to REGEN-COV, which contains two monoclonal antibodies – casirivimab and imdevimab – to be administered together for treating mild to moderate Covid-19 patients. The cocktail is indicated for adults and paediatric patients (12 years of age or older weighing at least 40 kg) who were at the risk of progressing to severe Covid-19. India granted an emergency use authorisation to the drug in May and it is the same used by doctors at Seven Hills Hospital. The drug is available in India through a tie-up between Roche India and Cipla.
There are other monoclonal antibody drugs in the fray for Covid-19. In June, India’s drug regulator gave an emergency use approval to American pharmaceutical company Eli Lilly’s antibody-drug combination – bamlanivimab and etesevimab. The same month, Indian company Zydus Cadila was granted permission to conduct clinical trials for its antibody-drug therapy.
How does the drug work?
The monoclonal antibodies mimic the actions performed by natural antibodies during an attack by a pathogen. For instance, casirivimab and imdevimab present in REGEN-COV are specifically made to target the spike protein of SARS-CoV-2, designed to block the virus’ attachment and entry into human cells.
“Thanks to its specific engineering of two neutralising antibodies which bind to different parts of the virus spike, the casirivimab and imdevimab cocktail remains efficacious against the widest spreading variants and reduces the risk of losing its neutralisation potency against new emerging variants,” said a release from Cipla.
Doctors who have used the cocktail drug said that timing is the key to get good results.
“One must also select the patients carefully,” said infectious disease specialist Dr Tanu Singhal, who practices at Mumbai’s Kokilaben Dhirubhai Ambani Hospital.
She has administered the drug to two patients – a 75-year-old woman with multiple comorbidities and a 50-year-old man with hypertension – and found that their fever went away within 24 hours of drug infusion and they recovered well.
“It’s ideal to give the drug within seven to 10 days and only to patients who are likely to progress to severe disease. It is an expensive therapy, therefore it’s crucial to choose the right candidates and not misuse it,” she said.
Drugs like tocilizumab and itolizumab that were repurposed for Covid-19 are also monoclonal antibodies. While they are indicated in severe patients who have already developed inflammation, cocktail therapies like REGEN-COV have to be administered much earlier, in order to stop the patient from developing the inflammatory syndrome.
A pack of REGEN-COV contains one vial of casirivimab (1,200 mg) and one vial of imdevimab (1,200 mg) and is priced at ₹1.19 lakh (inclusive of all taxes). One pack can be used for two patients, thus the cost per patient comes to ₹59,750. The vials need to be stored at 2 degrees Celsius to 8 degrees Celsius. Once opened, the vials should be stored at the same temperature and used within 48 hours.