Seattle-based vaccine company Icosavax posted disappointing clinical data today for its experimental COVID-19 vaccine, sending its stock into a dive.
Icosavax went public last June in an IPO that raised more than $180 million on the promise of vaccine technology spun out the University of Washington’s Institute for Protein Design. The company’s COVID-19 vaccine is a virus-like particle (VLP), a sphere studded with engineered copies of a key viral component, the spike protein.
Today the company announced interim results from its ongoing phase 1/2 trial of the two-dose shot. While the vaccine was well-tolerated by patients and yielded an immune response, “The level of response was below our expectations given what we know about VLPs, including from clinical studies in COVID-19 and from our own preclinical data,” said Niranjan Kanesa-thasen, Icosavax chief medical officer, in a statement.
Icosavax shares were down more than 60% in morning trading.
“Icosavax remains committed to its novel VLP platform and vision for combination and pan-respiratory vaccines,” said CEO Adam Simpson the statement. “We plan to investigate the potential causes of these discordant clinical results, including manufacture, shipment, and administration of the product.”
The new data showed that the shots raised an antibody immune response comparable to or below that of people who had been naturally infected with the virus. In contrast, previous studies with the mRNA-based vaccines made by Moderna and Pfizer/BioNTech have shown overall higher responses compared with natural infection.
A separate arm of the study used the Icosavax shot as a booster in patients who had received prior vaccination with one of the mRNA shots or another vaccine. That arm showed an eight-fold reduced antibody response to the Omicron variant compared with “wild type” virus.
The company is also developing a similar vaccine against respiratory syncytial virus (RSV) and is expecting interim data in the second quarter of this year. It also plans to launch a phase 1 study combining a vaccine against RSV and human metapneumovirus.