1. Preclinical Studies of PROTACs in Hematological Malignancies
Radka Bokorova, Ota Fuchs Cardiovasc Hematol Disord Drug Targets . 2021;21(1):7-22. doi: 10.2174/1871529X21666210308111546.
Incorrectly expressed or mutated proteins associated with hematologic malignancies have been generally targeted by chemotherapy using small-molecule inhibitors or monoclonal antibodies. But the majority of these intracellular proteins are without active sites and antigens. PROTACs, proteolysis targeting chimeras, are bifunctional molecules designed to polyubiquitinate and degrade specific pathological proteins of interest (POIs) by hijacking the activity of E3-ubiquitin ligases for POI polyubiquitination and subsequent degradation by the proteasome. This strategy utilizes the ubiquitin-proteasome system for the degradation of specific proteins in the cell. In many cases, including hematologic malignancies, inducing protein degradation as a therapeutic strategy offers therapeutic benefits over classical enzyme inhibition connected with resistance to inhibitors. Limitations of small-molecule inhibitors are shown. PROTACs can polyubiquitinate and mark for degradation of "undruggable"proteins, e.g. transcription factor STAT3 and scaffold proteins. Today, this technology is used in preclinical studies in various hematologic malignancies, mainly for targeting drug-resistant bromodomain and extraterminal proteins and Bruton tyrosine kinase. Several mechanisms limiting selectivity and safety of PROTAC molecules function are also discussed.
2. Identification of probe-quality degraders for Poly(ADP-ribose) polymerase-1 (PARP-1)
Zhengrong Shen, Zunyuan Wang, Chixiao Zhang, Meihao Liang, Xinyue Chang, Shenxin Zeng, Zhen Ma, Zhimin Zhang, Wenhai Huang J Enzyme Inhib Med Chem . 2020 Dec;35(1):1606-1615. doi: 10.1080/14756366.2020.1804382.
Poly(ADP-ribose) polymerase-1 (PARP-1), a critical DNA repair enzyme in the base excision repair pathway, has been pursued as an attractive cancer therapeutic target. Intervention with PARP-1 has been proved to be more sensitive to cancer cells carryingBRCA1/2mutations. Several PARP-1 inhibitors have been available on market for the treatment of breast, ovarian and prostatic cancer. Promisingly, the newly developed proteolysis targeting chimaeras (PROTACs) may provide a more potential strategy based on the degradation of PARP-1. Here we report the design, synthesis, and evaluation of a proteolysis targeting chimaera (PROTAC) based on the combination of PARP-1 inhibitor olaparib and the CRBN (cereblon) ligand lenalidomide. In SW620 cells, our probe-quality degrader compound2effectively induced PARP-1 degradation which results in anti-proliferation, cells apoptosis, cell cycle arresting, and cancer cells migratory inhibition. Thus, our findings qualify a new chemical probe for PARP-1 knockdown.
3. TrkC-Targeted Kinase Inhibitors And PROTACs
Bosheng Zhao, Kevin Burgess Mol Pharm . 2019 Oct 7;16(10):4313-4318. doi: 10.1021/acs.molpharmaceut.9b00673.
A small molecule motif (IY-IY), which binds the tropomyosin receptor kinase C (TrkC), was used to deliver the promiscuous kinase inhibitor (KI) dasatinib into breast cancer. Conjugates with noncleavable (1) and cleavable (2) linkers were compared in cellular assays and shown to have more impact on the cell viabilities of TrkC+breast cancer cells over TrkC-epithelial cells. The IY-IY fragment was also used to recruit the E3 ligase cereblon, giving a potent proteolysis targeting chimeric (PROTAC) for TrkC degradation in metastatic breast cancer cells.
