Design andEvaluation of a Folate-Targeted PEG-MMAEConjugate with Enzyme-Activated Drug Release for Enhanced Tumor Selectivityand Antitumor Efficacy

Abstract Polymer-drug conjugates hold significant promise for drug delivery applications. Water-soluble polymers prolong circulation, enhance solubility, reduce immunogenicity, and promote tumor accumulation via an enhanced permeability and retention effect. We first present the design and evaluation of an enzyme-activatable folate-targeted polyethylene glycol–monomethyl auristatin E conjugate. The folate-targeted conjugate 4A-BFA-11 maintains affinity for the folate receptor while achieving tumor enrichment through the synergistic effects of PEG-mediated prolonged circulation and folate-driven targeting. Subsequently, the conjugate undergoes enzymatic cleavage at the tumor site to release the active payload, enabling precise therapy. In vivo studies demonstrated that 4A-BFA-11, constructed using a folate-targeting strategy and a multiarm PEG carrier, effectively prolongs circulation time, improves tumor selectivity, and enhances antitumor efficacy. This strategy offers a novel approach for the efficient delivery of potent cytotoxic drugs through an enzyme-controlled activation mechanism, significantly broadening the therapeutic window while reducing systemic toxicity.