Degradation of the copolymers (obtained from the nanoparticle dry extracts) was carried out under accelerated conditions in THF with 5 wt % KOH (Table and Figure ). As expected, due to the absence of BMDO units, PT1 showed no decrease in M n , conversely to C0, which exhibited 76% decrease in M n and whose SEC traces approached that of the starting macro-CTA (Figure ), confirming the presence of ester groups in the copolymer chain (F BMDO = 0.07). Degradation of copolymers PT2-PT5 under the same conditions yielded very similar results with significant decrease in M n in the 70-87 % range, despite different F BMDO values, supporting the successful synthesis of degradable polymer prodrugs. Using MPDL instead of BMDO under the same experimental conditions as PT4 (see PT6, Table ) resulted in very similar outcome (except for F MPDL , which was significantly higher than F BMDO ), showing that the synthetic route is also applicable to other CKAs. Degradation of copolymer PT6 under accelerated conditions resulted in lower decrease in M n , which can be explained by the higher amount of close MPDL units compared to BMDO-based copolymers. The direct degradation of nanoparticle was first assessed under accelerated conditions (2.5 wt % KOH; pH = 14). Degradation of nanoparticles C0 (F BMDO = 0.07) resulted in a clear shift of the SEC trace towards a lower M n value, accounting for 44 % decrease in M n after 3 days (Figure ). It is interesting to note that, probably due to the high hydrophobicity and steric hindrance of Ptx, making access to the ester bond more difficult, the degradation of nanoparticles PT2 (F BMDO = 0.16, F Ptx = 0.01) was much slower than that of C0, showing only The anticancer cytotoxicity of the nanoparticles was then evaluated by cell viability assays on A549 lung cancer cells. As expected, Ptx-free nanoparticles C0 showed no toxicity (> 70% cell viability) up to at least 1 mg.mL -1 (Figure ), demonstrating the good biocompatibility of the empty nanoparticles and of its building blocks. In contrast, all the polymer prodrug nanoparticles tested (PT1, PT2* which are fluorescently labeled, PT4 and PT6) reached the IC 50 value as early as 0.1 mg.mL -1 (Figure ), which suggested an efficient release of Ptx from the nanoparticles and a significant cytotoxic effect. Cytotoxicity results were also expressed in terms of dose in Ptx (Figure and). While free Ptx gave an IC 50 value of 18 nM, in agreement with the literature, 37 all polymer prodrug nanoparticles showed higher IC 50 values, ranging from 1.4 to 14.9 µM. These results are in line with the prodrug concept, requiring cleavage of the drug-polymer linker before the active drug is released and can exert its cytotoxic mechanism.