To continue the analogy with polymer synthesis, the third synthetic strategy to design polymer prodrugs is termed the "grafting from" or "drug-initiated" method. It is perhaps the most simple and efficient route to construct polymer prodrugs by RDRP due to its simplicity, versatility and robustness, 189 compared with the "grafting to" and "grafting through" approaches, which still possess some limitations (e.g., multistep synthetic routes, significant workup, moderate yields, etc.). It relies on the growing by RDRP of a polymer chain from the drug previously functionalized by controlling agent (e.g., alkoxyamine for NMP, ATRP initiator, RAFT agent), resulting in polymer prodrug consisting of one drug molecule linked at the chain-end of a welldefined polymer (Figure ). After polymerization, a simple purification step is required to remove the unreacted monomer which is often a volatile. In addition, due to the flexibility and tolerance of RDRP towards functional groups, the "grafting from" approach represents an efficient route to produce a wide range of polymer prodrugs with tunable properties (e.g., soluble, amphiphilic, hydrophobic), thanks to the easy modulation of the nature of the drug, the linker and the polymer (Figure ).