Aashish Manglik, MD, PhD, envisions a future in which inhaled medications provide a barrier to protect the nose and throat from invading pathogens, including SARS-CoV-2, the virus that causes COVID-19. People heading into situations where there could be crowds — and therefore germs in the air — could use an inhaled targeted therapy to prevent illness, a nanobody facemask of sorts.
Manglik, a physician by training, leads a lab at the University of California, San Francisco, and has spent the past few years building a massive library of nanobodies that can be used investigate their use. The rising star in his field made Scientific American‘s 30 under 30 list in 2013.
When the pandemic hit, Manglik’s work, like that of so many others around the world, changed. He wanted to help find something “simple and self-administered” that could shield people from harm.
The SARS-CoV-2 virus takes hold in a person’s body when the spike protein comes into contact with an angiotensin-converting enzyme 2 (ACE2) cell receptor. Once the virus has infected the cell, it takes over and begins to make copies of itself.
But what if, investigators wonder, they could block the invader by giving the spike something else to attach to?
The COVID messenger RNA vaccines — like the Pfizer and Moderna ones authorized in the United States — are designed to teach the body how to protect against future infection. The vaccines give instructions to cells to make a piece of the spike protein found on the surface of the virus that causes COVID-19. This triggers an immune response, which produces antibodies that protect against infection should the actual virus enter the body.
But for people who test positive for COVID-19 before the vaccine has a chance to provide protection, treatment options are needed in addition to the monoclonal antibody drugs approved for emergency use by the US Food and Drug Administration.
The majority of the monoclonal antibodies under development for SARS-CoV-2 target the spike protein, as the vaccines do. Although they are showing therapeutic promise, there are drawbacks, Manglik says. Monoclonal antibodies are difficult to make, are expensive, and are administered intravenously, usually at high doses.
This is where nanobodies come in, he explains. Because of their small size, these single-domain antibodies, or antibody fragments, are promising building blocks for the next-generation of biologic drugs: needle-free treatments that can be converted into a fine mist.
And single-domain antibodies can be produced in bacteria or yeast and are durable, so they don’t have to be kept at exact temperatures and can withstand aerosol delivery.
It is not hard to imagine a world in which people who test positive for COVID-19 take inhaled medications before symptoms ever worsen, says Manglik.
So when the opportunity arose for his lab to join forces with the Walter lab — helmed by Peter Walter, PhD, also at the University of California, San Francisco — it made sense. Walter’s many honors include a prestigious Lasker Award, often seen as a precursor to a Nobel Prize.
Walter understood that the capacity of SARS-CoV-2 to bind with ACE2 proteins could theoretically be over-ridden by a precisely shaped nanobody. The team began screening the 2 billion nanobodies amassed in Manglik’s library. Together, they developed synthetic nanobodies that bind tightly to the spike and efficiently neutralize SARS-CoV-2 in cells. The discovery, published in Science, demonstrates a potential mechanism to disrupt the function of the spike protein.
Nanobodies Energizing Efforts
Another body of work, published in the same issue of Science, shows nanobodies produced by a llama binding tightly enough to the spike to inactivate it.
For their research, the team turned to a black llama named Wally, who resembled the black Labrador Retriever owned by senior investigator Yi Shi, PhD, from the University of Pittsburgh, and shares the dog’s name. They immunized Wally with the SARS-CoV-2 spike protein and, after about 2 months, the llama’s immune system produced mature nanobodies to help fight off infection from the virus.
Using a mass-spectrometry-based technique that Shi has been fine tuning for the past 3 years, his colleague Yufei Xiang, PhD, identified the nanobodies in Wally’s blood that would create the strongest bond with the spike.
When the scientists exposed those nanobodies to live virus, they found that a very small amount — just a fraction of a nanogram — could neutralize enough virus to protect a million human cells.
“It’s impressive work,” says Manglik. “The mass-spectrometry-based technique is really innovative.”
Manglik’s own work bypasses the need for a llama. As a graduate student, his lab spent thousands of dollars and had to wait months to receive harvested nanobodies. To democratize access for researchers everywhere, Manglik began to assemble one of the world’s largest nanobody libraries. To date, his lab has shared nanobodies housed in yeast cells with hundreds of labs around the world.
But with the pharmaceutical industry consumed with vaccine development and efforts to make conventional antibodies, the path for nanobody commercialization has proven difficult.
It is a struggle shared by Yakun Wan, 6000 miles away in Shanghai, China. The founder of Novamab Biopharmaceuticals estimates that their durable nanobodies are less than a year away from clinical study, and the company is looking for international partners to help move into clinical trials.
Novamab was initially developing inhaled nanobodies to treat asthma, but changed course to focus on COVID-19.
The Novamab library contains nanobodies from four camels immunized with the SARS-CoV-2 spike receptor. Wan says that as a child growing up in Xinjiang, a province in the northwest of China that shares a border with Russia, he looked across the desert to watch thousands of wild camels roam free. That these long-legged mammals with broad cushioned feet would one day factor so prominently in his work defies imagination, but today Wan’s farm houses about 100 camels. And his vision of patients with COVID-19 using an at-home nebulizer to inhale nanobodies is approaching realization.
Fine Mist of Possibilities
An estimated 117 million people around the world have been infected with COVID-19. There is a “pressing need” for medications that curb viral replication, says Xavier Saelens, PhD, from Ghent University in Belgium.
A positive COVID-19 test could soon be followed with an easily administered, inexpensive inhaled medication, he explains.
Global access to an affordable biologic for COVID-19 is essential, Saelens says, and could factor into future pandemic planning.
He wonders how things could have been different had more work been done after the first SARS outbreak, when scientists had the sequencing for SARS-CoV-1, and how many of the 2.6 million people who have died from COVID-19 might have been spared.
Saelens, whose lab focuses on influenza viruses, says it is very likely the next pandemic will be another respiratory virus. “The building blocks to prepare are already in hand, and now is the time to lay the regulatory groundwork that will be needed to fast-track future medications.”
Manglik’s work, which already changed in the pandemic, will move forward too. “In the next pandemic, once we have the sequence for a new pathogen, we could have a molecule in a matter of weeks,” he says.
The unique structure of the tiny nanobodies that have become such an enormous part of this small scientific community will help shape the next generation of biologic drugs. For some, it could one day be a breath of fine mist.