But antibody therapy has disadvantages. They are expensive and must be administered by infusion or injection. This makes them a poor choice for many low- and middle-income countries. And they may not perform well against certain popular variants. In fact, on June 25, the FDA suspended the nationwide distribution of Eli Lilly’s antibody cocktail because two worrying variants that did not seem to respond to the drug became more common.
When it comes to antiviral drugs, which interrupt the ability of the virus to replicate, there are fewer options available. Remdesivir is the only drug of its kind approved for the treatment of covid-19, largely because it is one of the few drug candidates that have been tested for human safety when the pandemic hits. It is one step ahead. But how effective it is is still an open question. Some studies have found that it can shorten the duration of the disease, while other studies have shown that it has little effect. The World Health Organization does not recommend its use.
Due to a variety of reasons, the development of antiviral drugs is lagging behind. Before covid-19, companies did not have much financial incentives to produce these drugs. The antiviral drugs that do exist only target 10 viruses, half of which are used to treat HIV. Chronic infections require longer treatments and thus make more money. “If there is no obvious market for treatments, then generally speaking, they will not invest in these types of treatments,” said John Bamforth, interim executive director of Peking University’s public-private partnership READDI. Carolina was established in Chapel Hill to develop new antiviral drugs.
There are also some scientific obstacles. In order to inhibit replication, the drug must bind to some essential viral proteins or enzymes and block its activity without harming the host cell. But unlike bacteria, viruses rely on the machines in the cells in which they live to replicate themselves, so they have very few proteins of their own. Even if researchers do encounter an effective compound, its effectiveness is often short-lived because the virus is constantly evolving.
Some researchers, including those at READDI, are working on drugs that target cellular proteins that are essential for virus replication. Most antiviral drugs only work on one virus. It is hoped that these compounds will be effective for their entire family. They may also be unlikely to cause resistance.
But new therapies need more time to develop. This is why the fastest way to put a drug on the shelves is to reuse an approved compound. They have been tested for safety and have fewer regulatory hurdles to gain approval for new uses of existing drugs. DNDi is testing various existing compounds in a clinical trial called ANTI-COV. The latest research focuses on the combination of the antiparasitic drug nitazoxanide and inhaled steroids. “The consensus is that you need a strong antiviral drug or a combination of antiviral drugs with different mechanisms of action, combined with a certain anti-inflammatory drug,” Cohen said.