Analogous to tisagenlecleucel, axi-cel targets CD19, however, it contains a CD28 co-stimulatory domain together with CD3ζ instead of 4-1BB.74,75 The most common side effects of both therapies are cytokine release syndrome (CRS) and neurotoxicity, where CRS is managed using IL-6 inhibition (further discussed in the section “CAR T-cell side effects”). Here, CD28 is linked to congenital rubella syndrome.