Shanghai-based nanobody specialist Novamab Biopharmaceuticals Co. Ltd. is developing a new neutralizing nanobody, Nb11-59, as a potential inhaled therapy for COVID-19 – a convenient treatment if developed successfully. Similar research is being conducted worldwide.

Researchers from the Shanghai startup said Nb11-59 exhibited potent antiviral activity against SARS-CoV-2 and high stability. The candidate can also be produced on a large scale.

“The delivery system is totally different from that of the current investigational drugs as we can use nebulizers to treat patients, and its stability will not be affected by nebulization,” Novamab CEO Yakun Wan told BioWorld. “The potential use of this drug is not only for treatment, but also for prevention. This nanobody can be nebulized. When you go to high-risk areas, you can just inhale it to prevent the coronavirus,” he added.

Nanobodies are derived from camels and llamas. They possess fully functional antibodies consisting only of heavy chains. These single domain antibodies are a quarter of the size of human antibodies, which make them small enough to be nebulized.

Wan and his team argue that nanobodies could be nebulized and delivered directly to lungs via an inhaler to target respiratory pathogens such as SARS-CoV-2. They say nanobodies show higher stability than most antibodies. Also, due to their structure, nanobodies can be easily constructed into multivalent or multispecific formats and produced via convenient steps of purification at costs lower than those of traditional antibodies.

Wan and his team have identified 381 nanobodies derived from four camels that recognized the SARS-CoV-2 spike receptor-binding domain. They found that seven of them could block the interaction between ACE2 and SARS-CoV-2-RBD as well as eight RBD mutants.

Among these seven nanobodies, Nb11-59 was singled out to be the most promising candidate as it exhibited the best neutralization activity against SARS-CoV-2 with ND50 of 0.55 μg/mL. It also binds to the RBD region of the spike protein.

Nb11-59 also has the potential for relatively low-cost mass production in Pichia pastoris, a kind of yeast used for rapid and cost-effective expression of recombinant proteins, with 20 g/L titer and 99.36% purity.

In the course of their work, outlined in an article published as a preprint on Biorxiv, the team expressed the humanized Nb11-59 in P. pastoris by fermentation. During the process, they found that Nb11-59 expression could reach 20 g/L through fermentation using the yeast expression system, which they believed to be the highest-yield expression of nanobodies yet reported.

The team also found that the specific purity of Nb11-59 was 99.36% through size-exclusion chromatography analysis, leading to a conclusion that “the commercial manufacturing and purification processes have been successfully developed and validated, and the key methods in analytical quality characterization have been already established.”

Moving toward the clinic

Wan said Novamab is now trying to move the candidate to clinical studies in China and the U.S. “We’re planning for an IND submission in the U.S. by the end of this year or early next year. We’re going to prepare the data package to do the same in China simultaneously,” he told BioWorld.

He believes nanobody-based drugs will be a long-term solution. Monoclonal antibodies and vaccines may induce antibody-dependent enhancement, which is associated with the Fc domain of antibodies. Nanobodies, however, lack Fc domains and could be ideal as neutralizing antibodies against viral infections.

Besides Novamab, other researchers have also had similar ideas and are doing their own studies. On August 11, researchers from The University of California San Francisco (UCSF) said they have developed an aerosol formulation known as Aeronabs made of nanobodies. Last month, Belgian firm Exevir Bio BV also unveiled plans to develop a nanobody-based antiviral therapy.

Novamab has specialized in developing nanobody-based drugs since its establishment in 2017. It has four portfolios covering immuno-oncology, autoimmune diseases, eye diseases and CAR T therapies, with all assets still in preclinical stage. The startup raised ¥30 million (US$4.3 million) in financing in 2017.

“We are not only working on treatments for COVID-19. With our technology platform, we’re developing a drug to treat asthma. We have other assets that can be used with a nebulizer.” Wan told BioWorld. “Our team is specialized in nanobody discovery, so we are able to identify functional nanobodies against different targets,” he added.