The experimental monoclonal antibody treatment for COVID-19 developed by the New York company Regeneron has attracted a lot of press in the past two weeks, in part because it is one of the most promising treatments targeting SARS-CoV-2 and COVID-19, but largely because the treatment was used on President Trump when he was diagnosed with COVID-19.
A report has recently been published that assesses the effectiveness of the antibodies at targeting SARS-CoV-2 and reducing viral load and the severity of the symptoms. In the report, the effectiveness of the treatment was evaluated in studies on rhesus monkeys and golden hamsters, which are believed to model severe forms of the disease. In those studies, the treatment was effective at reducing viral load in the upper and lower airways and reducing virus-induced symptoms.
In rhesus monkeys the treatment was shown to be effective when administered prophylactically and therapeutically. In studies on golden hamsters, treatment was also shown to be effective, limiting weight loss and reducing lung titers and evidence of pneumonia. Previous studies in humanized mice also showed the antibody treatment to be effective at treating COVID-19.
The Regeneron treatment – named REGN-COV2 – consists of two neutralizing antibodies that target non-overlapping epitopes on the protein spikes of SARS-CoV-2, which are used by the virus to gain entry into cells. Phase I clinical trials of REGN-COV2 commenced in June, with phase III trials now underway on at least 11,074 individuals.
In the study on rhesus monkeys, 6 were given an intravenous injection of REGN-COV2 and three were given a placebo. The monkeys were then exposed to SARS-CoV-2, intranasally and intratracheally, three days after receiving the injection. Swabs were taken from the monkeys and bronchoalveolar lavage (BAL) fluid was collected on day 1, day 3, and day 5 after being introduced to the virus. Genomic RNA and subgenomic RNA were then measured to gauge the effect of the antibodies on viral replication.
Monkeys that received REGN-COV2 had “accelerated clearance of gRNA with almost complete ablation of sgRNA in the majority of the animals was observed, showing that REGN-COV2 can almost completely block establishment of virus infection.” Monkeys treated with REGN-COV2 1-day post infection, exhibited faster viral clearance than the control group. There were similar findings in studies on golden hamsters when REGN-COV2 was administered two days before infection and one day after infection.
The researchers also report they observed no signs of increased viral load or worsening of pathology at higher and lower doses in either animal model.
Based on the findings of these studies, the researchers concluded REGN-COV2 has clinical benefits for both the prevention and treatment of COVID-19.