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Covid-19 Nasal Spray Vaccine Discontinued

Nasal spray

(Wikimedia Commons)

30 June 2021. A biotechnology company is discontinuing further work on a Covid-19 vaccine nasal spray after clinical trial results show it produces little immune response. Altimmune Inc. in Gaithersburg, Maryland says it will focus instead on developing its therapies for obesity and liver disorders.

Altimmune is a developer of drugs that invoke the immune system, including vaccines against infectious diseases. Among the company’s pipeline products is NasoVax, an influenza vaccine formulated as a nasal spray that Altimmune says in clinical trials generates protective antibodies much like injected flu vaccines. In addition, says the company, NasoVax protects against infections in mucous membranes and generates T-cell responses in the immune system, with those immune responses lasting 12 to 14 months in about half of the participants.

With the Covid-19 pandemic, Altimmune began work on AdCovid, a vaccine in nasal spray form to protect against the disease. Like NasoVax, the vaccine’s chemistry resembles receptor proteins in cells, where the SARS-CoV-2 virus’s spike protein binds, to begin the infection process. When binding to the spike protein, AdCovid aims to generate immunoglobulin G and A, or IgG and IgA, neutralizing antibodies in the blood and mucous membranes respectively, to prevent immediate Covid-19 infections, but also prevent infections from developing in the respiratory tract.

As reported in Science & Enterprise in July 2020, AdCovid produces immune responses in preclinical tests with lab mice. Findings show AdCovid generates detectable levels of IgG antibodies in mice 14 days after a single dose, and twice the concentration of IgA antibodies of convalescent plasma after 28 days. Other results show show a single dose of AdCovid produces antibodies in mouse respiratory fluids in mucous membranes at levels 29 times higher than before vaccination.

Immune responses lower than expected

Altimmune’s early-stage clinical trial of AdCovid aims to assess the vaccine’s safety and ability to produce an immune response in healthy adults. The trial, however, ran into trouble almost from the beginning when the Food and Drug Administration temporarily stopped the study in December 2020 until the company cleared up questions about the trial protocol as well as chemistry, manufacturing, and control issues about the vaccine.

Results from 80 trial participants, says AltImmune, show AdCovid is well tolerated with about the same rate of adverse effects as a placebo. However, immune responses of participants are lower than expected. Altimmune says results show AdCovid recipients produce antibodies that bind to the spike protein on SARS-CoV-2 viruses, but the volume of those antibodies and percentage of participants responding to the vaccine are lower than other vaccines already authorized by FDA.

Scot Roberts, Altimmune’s chief scientist, says the weaker immune response from AdCovid may be due to the lack of earlier immunity in trial participants, which differs from its studies of NasoVax. “Unlike the NasoVax study,” notes Roberts in a company statement, “the AdCovid study population lacked immunity from prior infection or vaccination. We believe that prior immunity in humans may be important for a robust immune response to intranasal dosing with AdCovid.”

Altimmune says it will stop enrolling participants in the AdCovid trial, and transfer those resources to its obesity and liver disease treatment candidates. Earlier this month, the company reported initial results from an early-stage trial of a synthetic peptide code-named ALT-801, a glucagon-like peptide 1, or GLP-1 agonist that acts like the hormone glucagon to work with insulin keeping blood glucose levels in a safe range. The findings show obese and overweight participants reported an average weight loss of more than a five percent with few adverse effects.

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