According to this [1] it's cultivated in yeast:

> Su cultivo se realiza en células de levadura, lo que la diferencia de "Soberana 2"

"Iit's cultivated in yeats, what differentiates it from 'Soberana 2' " (Another Cuban vaccine)

[1] https://www.swissinfo.ch/spa/coronavirus-cuba--previsi%C3%B3...