Synthesis and Biological Evaluation of an isoDGR‐Paclitaxel Conjugate Containing a Cell‐Penetrating Peptide to Promote Cellular Uptake

Abstract

Two new Drug Delivery Systems (DDS) cyclo[DKP‐isoDGR]‐PEG‐4‐Val‐Ala‐PTX (2) and cyclo[DKP‐isoDGR]‐PEG‐4‐sC18‐Val‐Ala‐PTX (3), containing the cyclo[DKP‐isoDGR] integrin ligand and the cytotoxic agent Paclitaxel (PTX), were synthesized to investigate the influence of a PEG‐4 chain and of the sC18 cell‐penetrating peptide (CPP) on the cellular uptake and the cytotoxicity of the constructs. A “double click‐reaction strategy” was planned, to realize the connection of cyclo[DKP‐isoDGR] and PTX to the CPP moiety. Anti‐proliferative bioassays were performed on the αVβ3‐positive U87 human glioblastoma cell line using a short contact time (15 min) followed by draining, washing of the cells, and re‐incubation for 72 h. Compound 3 was significantly more potent (IC50=27.6 μM) than compound 2 (IC50>100 μM), and showed a reduced potency loss with respect to PTX (IC50=71 nM).

Optimizing the enzymatic release of MMAE from isoDGR-based small molecule drug conjugate by incorporation of a GPLG-PABC enzymatically cleavable linker

“…Integrins are transmembrane receptors that are over-expressed on the cell surface of several tumors like glioblastoma ( Gladson and Cheresh, 1991 ), melanoma ( Brooks et al, 1994 ), prostate ( Heß et al, 2014 ), pancreatic cancer ( Hosotani et al, 2002 ) and others, and are involved in several biological processes linked to the tumor growth. To this aim, we designed a cyclic peptidomimetic containing a diketopiperazine (DKP) and the α v β 3 integrin recognizing sequence Arg-Gly-Asp (RGD) ( Marchini et al, 2012 ; da Ressurreição et al, 2009 ) or iso Asp-Gly-Arg ( iso DGR) ( Mingozzi et al, 2013 ; Panzeri et al, 2015 ) with low-nanomolar affinity, which were conjugated to different cytotoxic payloads such as α-amanitin ( Bodero et al, 2018 ), paclitaxel (PTX) ( Dal Corso et al, 2015 ; Dias et al, 2017 ; Rivas et al, 2018 ; Bodero et al, 2021 ), and auristatin derivatives ( Dias et al, 2019 ) through the cathepsin-sensitive VA linker. In addition, the self-immolative spacer p -aminobenzyloxycarbamate (PABC) was inserted to facilitate the release of the drug upon enzymatic cleavage.…”