Cancer Selective Target Degradation by Folate-Caged PROTACs

Abstract

PROTACs (proteolysis targeting chimeras) are an emerging class of promising therapeutic modalities that degrade intracellular protein targets by hijacking the cellular ubiquitin–proteasome system. However, potential toxicity of PROTACs in normal cells due to the off-tissue on-target degradation effect limits their clinical applications. Precise control of a PROTAC’s on-target degradation activity in a tissue-selective manner could minimize potential toxicity/side-effects. To this end, we developed a cancer cell selective delivery strategy for PROTACs by conjugating a folate group to a ligand of the VHL E3 ubiquitin ligase, to achieve targeted degradation of proteins of interest (POIs) in cancer cells versus noncancerous normal cells. We show that our folate-PROTACs, including BRD PROTAC (folate-ARV-771), MEK PROTAC (folate-MS432), and ALK PROTAC (folate-MS99), are capable of degrading BRDs, MEKs, and ALK, respectively, in a folate receptor-dependent manner in cancer cells. This design provides a generalizable platform for PROTACs to achieve selective degradation of POIs in cancer cells.

Strategies for designing proteolysis targeting chimaeras (PROTACs)

“…250 Wei et al developed a folate-PROTAC conjugation strategy to improve the selectivity of protein degradation in cancer cells over normal cells (Figure 28). 251 The folate-PROTAC conjugates were designed by attaching a folate group onto the hydroxyl group of the VHL ligand via an ester linker. The folate part was recognized by FOLR1, which mediated the entrance and enrichment of the whole conjugate into cancer cells.…”

Light-Controllable PROTACs for Temporospatial Control of Protein Degradation

“…A major disadvantage of antibody-conjugated PROTAC is its relatively high molecule weight and weak stability. Thus, we have recently developed a small molecule version of targeting delivery platform for PROTACs, namely folate-PROTAC ( Liu et al, 2021 ), by conjugating a folate group on the hydroxyl group of VHL ligand, to specific deliver PROTACs into cancer cells that express relatively high levels of folate receptor α (FOLR1) ( Scaranti et al, 2020 ). Moreover, PROTACs that recruits cancer-specific E3 ligase might provide a way to achieve cancer-selective action of PROTACs ( Nalawansha and Crews, 2020 ).…”

“…An alternative approach for controllable action of PROTACs in cancer cells could be taking advantage of cancer-specific receptors or transporters, such as HER2 and FOLR1 ( Scaranti et al, 2020 ) for the guided delivery of PROTACs into cancer, but not normal cells. To this end, other types of third generation PROTACs, including antibody-conjugated PROTACs ( Dragovich et al, 2020 , 2021a , b ; Maneiro et al, 2020 ; Pillow et al, 2020 ) and folate-PROTAC ( Liu et al, 2021 ), have been recently developed, which specifically deliver PROTAC to cancer cells, thus avoiding potential toxicity to normal cells. Compared with the light-controllable PROTACs, folate-PROTAC ( Liu et al, 2021 ) have relatively higher molecule weight of over 1,000 Da, and antibody-conjugated PROTACs ( Dragovich et al, 2020 , 2021a , b ; Maneiro et al, 2020 ; Pillow et al, 2020 ) are macromolecule drug that could only be administrated by injection.…”

“…To this end, other types of third generation PROTACs, including antibody-conjugated PROTACs ( Dragovich et al, 2020 , 2021a , b ; Maneiro et al, 2020 ; Pillow et al, 2020 ) and folate-PROTAC ( Liu et al, 2021 ), have been recently developed, which specifically deliver PROTAC to cancer cells, thus avoiding potential toxicity to normal cells. Compared with the light-controllable PROTACs, folate-PROTAC ( Liu et al, 2021 ) have relatively higher molecule weight of over 1,000 Da, and antibody-conjugated PROTACs ( Dragovich et al, 2020 , 2021a , b ; Maneiro et al, 2020 ; Pillow et al, 2020 ) are macromolecule drug that could only be administrated by injection. Taken together, further studies are needed to make these third generation PROTACs (light-controllable PROTACs, antibody-conjugated PROTACs and folate-PROTAC) more practical in clinic.…”

Options to Improve the Action of PROTACs in Cancer: Development of Controlled Delivery Nanoparticles

“…Recent advances of VHL-and CRB-based PROTACs for treatment of diseases were summarized by C. Wang et al (2021); 2022. The challenges of the emerging degradation platforms LYsosome-TArgeting Chimaeras (LYTACs) and Antibody-based PROTACs (AbTACs) to target extracellular and membrane proteins are described by Lin et al (2021), and the advantages and disadvantages of lightcontrollable PROTACs for clinical application as a method of controlling induced protein degradation by light have been recently summarized by Liu et al (2021a); Reynders and Trauner 2021. Most of PROTACs currently under development are targeting cancer, neurologic disorders, and inflammation diseases. In relation to cancer, there is a great variety of PROTACs formulated against oncogenic proteins including transcription factors such as BET, STAT3, androgen, estrogen receptors; transmembrane receptors like, FLT-3, the epidermal growth factor receptor (EGFR); or intracellular signalling mediators, such as BRAF, KRAS, the fusion protein BCR-ABL, or the pro-survival protein MCL1, among others (Sun et al, 2019).…”