Enzymatic on-site amplification:

Enzyme converts as much drug as its weight every minute
Sustained Cytotoxicity compared to decaying cytotoxicity in direct drug delivery.

Amino-acid depletion and / or cytotoxic drug production

Capability to simultaneously starve and poison cancer cells

Reduced off-target toxicity:

Enzyme loses catalytic activity due to low pH in RES macrophages

More personalized medicine:

Prodrug dose can be externally controlled/modulated
Large window of controllability due to much less toxic nature of prodrug