Icosavax dis­cov­ers what caused its lead vac­cine to flop, and does­n't see it af­fect­ing fol­low-up pro­grams

Seat­tle-based Icosavax was one of the com­pa­nies in the rat race to de­vel­op Covid-19 vac­cine shots bet­ter than Pfiz­er and Mod­er­na. How­ev­er, when clin­i­cal tri­als showed that its vac­cine can­di­date, IVX-411, fared ‘be­low ex­pec­ta­tions,” the com­pa­ny launched an in­ves­ti­ga­tion. Now those re­sults are out.

The prob­lem, Icosavax says, had to do with the re­cep­tor bind­ing do­main (RBD) of the anti­gen com­po­nent of the vac­cine, which be­came un­sta­ble dur­ing man­u­fac­tur­ing and sub­se­quent stor­age at 2-8 °C. Icosavax us­es a “virus-like par­ti­cle” (VLP) shaped like a soc­cer ball, with the “white” parts mak­ing up the vi­ral struc­ture and the “black” spots rep­re­sent­ing the dis­played anti­gens.

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