Zwitterionic Internalizable Peptide‐Drug Conjugates: Tumor‐Selective Ultrafast Uptake and Transcytosis for Enhanced Antitumor Therapy

Here a novel class of zwitterionic internalizable peptide (ZIP)-drug conjugates is presented. The conjugates incorporate γ-glutamyl-α-aminobutyrylamino-functionalized lysine peptides as the ZIP backbones and disulfide-linked camptothecin (CPT) as the toxic payload. The ZIPs significantly enhance the water solubility of CPT without compromising its cytotoxicity. Cellular uptake profiling shows ultrafast internalization of the conjugates in tumor cells within 5 min. Mechanistic studies reveal that they enter cells via lipid raft-mediated pathways, involving both energy-driven active transport and membrane fluidity-dependent passive uptake. Furthermore, these conjugates exhibit robust transcytosis abilities across dense cell monolayers and tumor spheroids. These characteristics confer prolonged blood circulation, enhanced tumor accumulation, and deep tumor penetration on the conjugates, which result in potent in vivo antitumor activity and minimal systemic toxicity. This study underscores the potential of the conjugates for safer and more effective cancer therapies and presents ZIPs as a new category of molecularly defined delivery tools for biomedical applications.