Degradation of nanoparticles G2 under accelerated conditions (Figure ), led to 26 % decrease in M n after 3 days and reached 69 % after nearly a month, like the Ptx-based counterparts (PT2). Similarly to Ptx-based copolymer prodrug nanoparticles, the cytotoxicity of POEGMA 28 -b-P(LMA-co-BMDO-co-GemMA) nanoparticles was then evaluated on A549 cancer cells and expressed in terms of copolymer mass concentration and gemcitabine molar concentration (Figures ). G1-G3 nanoparticles clearly showed high toxicity in A549 cancer cells as early as 0.01-0.1 mg.mL -1 , conversely to the drug-free nanoparticles C0 leading to 70 % cell viability at 1 mg.mL -1 (Figure ). While free drugs usually lead to much lower IC 50 values than the corresponding polymer prodrugs, due to the necessary time for their release while free drugs are immediately active, nanoparticles G1 and G3 gave IC 50 values very close to those of free Gem (190-390 vs. 180 nM), demonstrating rapid and efficient release of the drug. Interestingly, insertion of BMDO units in the copolymer seems to lead higher IC 50 values (190 vs. 390 nM), which has already been observed with other types of polymer prodrug systems. Presence of BMDO is thought to increase the hydrophobicity of the polymer prodrug, leading to slower drug release.