Stimuli‐Responsive PROTACs for Controlled Protein Degradation

Abstract

Proteolysis Targeting Chimeras (PROTACs) represent a promising therapeutic modality to address undruggable and resistant issues in drug discovery. However, potential on‐target toxicity remains clinically challenging. We developed a generalized caging strategy to synthesize a series of stimuli‐responsive PROTACs (sr‐PROTACs) with diverse molecular blocks bearing robust and cleavable linkers, presenting “turn on” features in manipulating protein degradation. By leveraging pathological cues, such as elevated ROS, phosphatase, H2S, or hypoxia, and external triggers, such as ultraviolet light, X‐Ray, or bioorthogonal reagents, we achieved site‐specific activation and traceless release of original PROTACs through de‐caging and subsequent self‐immolative cleavage, realizing selective uptake and controlled protein degradation in vitro. Especially, in vivo study revealed that two sr‐PROTACs with phosphate‐ and fluorine‐containing cages exhibited high solubility and long plasma exposure, and were specifically activated by tumor overexpressing phosphatase or low dosage of X‐Ray irradiation in situ, leading to efficient protein degradation and potent tumor remission. With more reactive biomarkers to be screened from clinical practice, our caging library could provide a general tool to design activatable PROTACs, prodrugs, antibody drug conjugates, and smart biomaterials for personalized treatment, tissue engineering or regenerative medicine.

Nano-PROTACs: state of the art and perspectives

“…Based on the various membrane receptors on the cell surface in the targeted tissue, folate-caged, 18,19 aptamer-conjugated, 20,21 and antibody-conjugated 22,23 PROTACs have been widely developed to facilitate PROTAC drug delivery by receptor-mediated endocytosis. To enable discrete control over PROTACs’ function, some labile protecting groups (such as photo-activated 24–26 and hypoxia-activated 27 ) have been installed on the POI ligands 24,27 or E3 ligase ligands 25,26,28 to form stimuli-responsive caged PROTACs. For example, after light exposure with a specific wavelength, the optical activation of small molecule-induced protein degradation was observed in terms of photo-caged PROTACs.…”

New-generation advanced PROTACs as potential therapeutic agents in cancer therapy

“…have made significant advancements in the field of controllable targeted drug design by developing a novel radiation-responsive PROTAC prodrug NGP-25 (Fig. 10 C) for traceless release [ 77 ]. This innovative approach utilizes carbamate-bearing cages that exhibit excellent chemical and proteolytic stabilities, ensuring the stability of NGP-25 in blood.…”

“…D Chemical structures of the enzyme-responsive PROTAC (adapted from [ 82 ]). E Chemical structures of the enzyme-responsive PROTAC (adapted from [ 77 ]) …”

“…An et al . developed a novel and versatile approach for synthesizing a phosphatase-responsive PROTAC prodrug with diverse molecular blocks that possess both robustness and cleavable linkers [ 77 ]. This strategy allows for the precise manipulation of protein degradation by introducing a "turn on" feature.…”

Liposomal STAT3-Degrading PROTAC Prodrugs Promote Anti-Hepatocellular Carcinoma Immunity via Chemically Reprogramming Cancer Stem Cells

“…To investigate if the liposomal PROTAC prodrug could deplete STAT3 in HCC-derived CSCs, we incubated hepa1-6-derived CSCs with inS3, inS3 + VL, and inS3-TEG-VL and found that only inS3-TEG-VL treatment induced obvious reduction in the STAT3 levels, suggesting that inS3-TEG-VL was responsible for degrading CSC-intrinsic STAT3 rather than those separated components (Figure L). WB analysis also revealed a positive correlation between STAT3 deletion efficacy and the inS3-TEG-VL dose, which could be explained by the catalyst-like protein-degrading properties according to previous reports , (Figure J,K). The PROTAC-dependent STAT3 deletion was highly efficient, as a low inS3-TEG-VL dose of 3.2 μM almost abolished STAT3 in hepa1-6-derived CSCs, which was selected as the standard condition for subsequent in vitro and in vivo analyses.…”