Even if pH-sensitivity was successfully demonstrated in vitro on various types of polymer prodrug nanocarriers as a promising strategy to perform spatio-temporal drug release, achieving such selective drug delivery in vivo by taking advantage of the small pH difference with the tumor microenvironment is much more challenging. Therefore, other relevant stimuli related to cancer cells, 47 such as the hypoxia-specific environment, 56 could constitute an interesting alternative. The presence of hypoxic cells in solid tumors is a specific feature that stimuli-sensitive nanocarriers could take advantage of to trigger drug release, 54 via the design of reducible drug linkers.