Template-assisted covalent modification underlies activity of covalent molecular glues

Yen-Der Li, Michelle W. Ma, Muhammad Murtaza Hassan, Moritz Hunkeler, Mingxing Teng, Kedar Puvar, Justine C. Rutter, Ryan J. Lumpkin, Brittany Sandoval, Cyrus Y. Jin, Anna M. Schmoker, Scott B. Ficarro, Hakyung Cheong, Rebecca J. Metivier, Michelle Y. Wang, Shawn Xu, Woong Sub Byun, Brian J. Groendyke, Inchul You, Logan H. Sigua, Isidoro Tavares, Charles Zou, Jonathan M. Tsai, Paul M. C. Park, Hojong Yoon, Felix C. Majewski, Haniya T. Sperling, Jarrod A. Marto, Jun Qi, Radosław P. Nowak, Katherine A. Donovan, Mikołaj Słabicki, Nathanael S. Gray, Eric S. Fischer & Benjamin L. Ebert

 Nat Chem Biol, 2024

https://doi.org/10.1038/s41589-024-01668-4

Molecular glues are proximity-inducing small molecules that have emerged as an attractive therapeutic approach. However, developing molecular glues remains challenging, requiring innovative mechanistic strategies to stabilize neoprotein interfaces and expedite discovery. Here we unveil a trans-labeling covalent molecular glue mechanism, termed ‘template-assisted covalent modification’. We identified a new series of BRD4 molecular glue degraders that recruit CUL4DCAF16 ligase to the second bromodomain of BRD4 (BRD4BD2). Through comprehensive biochemical, structural and mutagenesis analyses, we elucidated how pre-existing structural complementarity between DCAF16 and BRD4BD2 serves as a template to optimally orient the degrader for covalent modification of DCAF16Cys58. This process stabilizes the formation of BRD4–degrader–DCAF16 ternary complex and facilitates BRD4 degradation. Supporting generalizability, we found that a subset of degraders also induces GAK–BRD4BD2 interaction through trans-labeling of GAK. Together, our work establishes ‘template-assisted covalent modification’ as a mechanism for covalent molecular glues, which opens a new path to proximity-driven pharmacology.

Direct RAS inhibitors turn 10

 Ostrem, J.M.L., Peters, U. & Shokat, K.M

 Nat Chem Biol (2024). 

https://doi.org/10.1038/s41589-024-01691-5

RAS proteins, central drivers of cancer, appeared ‘undruggable’ for almost 30 years. Here we provide a personal perspective on the effort leading to our initial report of KRASG12C inhibitors in 2013, and the decade of discoveries that followed.

Direct RAS inhibitors turn 10

Restoring susceptibility to β-lactam antibiotics in methicillin-resistant Staphylococcus aureus

Van T. Nguyen, Biruk T. Birhanu, Vega Miguel-Ruano, Choon Kim, Mayte Batuecas, Jingdong Yang, Amr M. El-Araby, Eva Jiménez-Faraco, Valerie A. Schroeder, Alejandra Alba, Neha Rana, Safaa Sader, Caitlyn A. Thomas, Rhona Feltzer, Mijoon Lee, Jed F. Fisher, Juan A. Hermoso, Mayland Chang & Shahriar Mobashery 

Nat Chem Biol 2024

https://www.nature.com/articles/s41589-024-01688-0

Infections by Staphylococcus aureus have been treated historically with β-lactam antibiotics. However, these antibiotics have become obsolete in methicillin-resistant S. aureus by acquisition of the bla and mec operons. The presence of the β-lactam antibiotic is detected by the sensor domains of BlaR and/or MecR, and the information is transmitted to the cytoplasm, resulting in derepression of the antibiotic-resistance genes. We hypothesized that inhibition of the sensor domain would shut down this response system, and β-lactam susceptibility would be restored. An in silico search of 11 million compounds led to a benzimidazole-based hit and, ultimately, to the boronate 4. The X-ray structure of 4 is covalently engaged with the active-site serine of BlaR. Compound 4 potentiates by 16- to 4,096-fold the activities of oxacillin and of meropenem against methicillin-resistant S. aureus strains. The combination of 4 with oxacillin or meropenem shows efficacy in infected mice, validating the strategy.

Structural Dynamics of the Ubiquitin Specific Protease USP30 in Complex with a Cyanopyrrolidine-Containing Covalent Inhibitor

Darragh P O’Brien, Hannah BL Jones, Yuqi Shi, Franziska Guenther, Iolanda Vendrell, Rosa Viner, Paul E Brennan, Emma Mead, Tryfon Zarganes-Tzitzikas, John B Davis, Adán Pinto-Fernández, Katherine S England, Emma J Murphy, Andrew P Turnbull, Benedikt M Kessler

bioRxiv 2024.07.20.604388; 

doi: https://doi.org/10.1101/2024.07.20.604388

Inhibition of the mitochondrial deubiquitinating enzyme USP30 is neuroprotective and presents therapeutic opportunities for the treatment of idiopathic Parkinson’s Disease and mitophagy-related disorders. We have integrated structural and quantitative proteomics with biochemical assays to decipher the mode of action of covalent USP30 inhibition by a small molecule containing a cyanopyrrolidine reactive group, USP30-I-1. The inhibitor demonstrated high potency and selectivity for endogenous USP30 in neuroblastoma cells. Enzyme kinetics and Hydrogen Deuterium eXchange mass spectrometry (HDX-MS) infers that the inhibitor binds tightly to regions surrounding the USP30 catalytic cysteine and positions itself to form a binding pocket along the thumb and palm domains of the protein, thereby interfering its interaction with ubiquitin substrates. A comparison to a non-covalent USP30 inhibitor containing a benzosulfonamide scaffold revealed a slightly different binding mode closer to the active site Cys77, which may provide the molecular basis for improved selectivity towards USP30 against other members of the DUB enzyme family. Our results highlight advantages in developing covalent inhibitors, such as USP30-I-1, for targeting USP30 as treatment of disorders with impaired mitophagy.

DCAF16-Based Covalent Handle for the Rational Design of Monovalent Degraders

Melissa Lim, Thang Do Cong, Lauren M. Orr, Ethan S. Toriki, Andrew C. Kile, James W. Papatzimas, Elijah Lee, Yihan Lin, and Daniel K. Nomura

ACS Central Science 2024 10 (7), 1318-1331

DOI: 10.1021/acscentsci.4c00286

Targeted protein degradation with monovalent molecular glue degraders is a powerful therapeutic modality for eliminating disease causing proteins. However, rational design of molecular glue degraders remains challenging. In this study, we sought to identify a transplantable and linker-less covalent handle that could be appended onto the exit vector of various protein-targeting ligands to induce the degradation of their respective targets. Using the BET family inhibitor JQ1 as a testbed, we synthesized and screened a series of covalent JQ1 analogs and identified a vinylsulfonyl piperazine handle that led to the potent and selective degradation of BRD4 in cells. Through chemoproteomic profiling, we identified DCAF16 as the E3 ligase responsible for BRD4 degradation─an E3 ligase substrate receptor that has been previously covalently targeted for molecular glue-based degradation of BRD4. Interestingly, we demonstrated that this covalent handle can be transplanted across a diverse array of protein-targeting ligands spanning many different protein classes to induce the degradation of CDK4, the androgen receptor, BTK, SMARCA2/4, and BCR-ABL/c-ABL. Our study reveals a DCAF16-based covalent degradative and linker-less chemical handle that can be attached to protein-targeting ligands to induce the degradation of several different classes of protein targets.

Contribution of Noncovalent Recognition and Reactivity to the Optimization of Covalent Inhibitors: A Case Study on KRasG12C

Nikolett Péczka, Ivan Ranđelović, Zoltán Orgován, Noémi Csorba, Attila Egyed, László Petri, Péter Ábrányi-Balogh, Márton Gadanecz, András Perczel, József Tóvári, Gitta Schlosser, Tamás Takács, Levente M. Mihalovits, György G. Ferenczy, László Buday, and György M. Keserű

ACS Chemical Biology 2024

DOI: 10.1021/acschembio.4c00217

Covalent drugs might bear electrophiles to chemically modify their targets and have the potential to target previously undruggable proteins with high potency. Covalent binding of drug-size molecules includes a noncovalent recognition provided by secondary interactions and a chemical reaction leading to covalent complex formation. Optimization of their covalent mechanism of action should involve both types of interactions. Noncovalent and covalent binding steps can be characterized by an equilibrium dissociation constant (KI) and a reaction rate constant (kinact), respectively, and they are affected by both the warhead and the scaffold of the ligand. The relative contribution of these two steps was investigated on a prototypic drug target KRASG12C, an oncogenic mutant of KRAS. We used a synthetically more accessible nonchiral core derived from ARS-1620 that was equipped with four different warheads and a previously described KRAS-specific basic side chain. Combining these structural changes, we have synthesized novel covalent KRASG12C inhibitors and tested their binding and biological effect on KRASG12C by various biophysical and biochemical assays. These data allowed us to dissect the effect of scaffold and warhead on the noncovalent and covalent binding event. Our results revealed that the atropisomeric core of ARS-1620 is not indispensable for KRASG12C inhibition, the basic side chain has little effect on either binding step, and warheads affect the covalent reactivity but not the noncovalent binding. This type of analysis helps identify structural determinants of efficient covalent inhibition and may find use in the design of covalent agents.

High-Throughput Covalent Modifier Screening with Acoustic Ejection Mass Spectrometry

Xiujuan Wen, Chang Liu, Kiersten Tovar, Patrick Curran, Matthew Richards, Sony Agrawal, Richard Johnstone, Ryan E. Loy, Joey L. Methot, My Sam Mansueto, Markus Koglin, Mary Jo Wildey, Lyle Burton, Thomas R. Covey, Kevin P. Bateman, Michael Kavana, and David G. McLaren

Journal of the American Chemical Society 2024 

https://pubs.acs.org/doi/abs/10.1021/jacs.4c02377

Interests in covalent drugs have grown in modern drug discovery as they could tackle challenging targets traditionally considered “undruggable”. The identification of covalent binders to target proteins typically involves directly measuring protein covalent modifications using high-resolution mass spectrometry. With a continually expanding library of compounds, conventional mass spectrometry platforms such as LC–MS and SPE-MS have become limiting factors for high-throughput screening. Here, we introduce a prototype high-resolution acoustic ejection mass spectrometry (AEMS) system for the rapid screening of a covalent modifier library comprising ∼10,000 compounds against a 50 kDa-sized target protein─Werner syndrome helicase. The screening samples were arranged in a 1536-well format. The sample buffer containing high-concentration salts was directly analyzed without any cleanup steps, minimizing sample preparation efforts and ensuring protein stability. The entire AEMS analysis process could be completed within a mere 17 h. An automated data analysis tool facilitated batch processing of the sample data and quantitation of the formation of various covalent protein–ligand adducts. The screening results displayed a high degree of fidelity, with a Z′ factor of 0.8 and a hit rate of 2.3%. The identified hits underwent orthogonal testing in a biochemical activity assay, revealing that 75% were functional antagonists of the target protein. Notably, a comparative analysis with LC–MS showcased the AEMS platform’s low risk of false positives or false negatives. This innovative platform has enabled robust high-throughput covalent modifier screening, featuring a 10-fold increase in library size and a 10- to 100-fold increase in throughput when compared with similar reports in the existing literature.

Covalent isothiocyanate inhibitors of macrophage migration inhibitory factor as potential colorectal cancer treatments

Joel Tyndall, Lohitha Putha, Liang K. Kok, Matthias Fellner, Malcolm T. Rutledge, Allan B. Gamble, Sigurd M. Wilbanks, Andrea J. Vernall,

 ChemMedChem 2024, e202400394.

https://doi.org/10.1002/cmdc.202400394

Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine with roles in innate and adaptive human immune responses, as well as inflammation. MIF exerts its biological activity by binding to the cell surface receptor CD74 as well as intracellular signalling proteins. MIF also possesses keto-enol tautomerase activity. Inhibition of the tautomerase activity has been associated with loss of biological activity of MIF and a potential anticancer target. Isothiocyanates (ITCs) are a class of compounds present in cruciferous vegetables that inhibit the MIF tautomerase activity via covalent modification of the N-terminal proline. A range of substituted ITCs featuring benzyl, phenethyl and phenyl propyl isothiocyanates were designed, synthesised and tested to determine any structure activity relationship for inhibiting MIF. Crystal structures of covalent compounds 8 and 9 in complex with rhMIF revealed key hydrogen bonding and edge-to-face π stacking interactions. Compound 9 and 11 with sub micromolar activity were tested in the NCI60 cancer cell lines panel. Both compounds showed tissue-specific reduced growth in colon and renal cancer cell lines, while one of these showed potent, dose-dependent inhibition of growth against all seven colon cancer cell lines (GI50 < 2.5 µM) and all eight renal cancer cell lines (GI50 < 2.2 µM).

Recruitment of FBXO22 for targeted degradation of NSD2 [@CherylArrowsmi1]

Nie, D.Y., Tabor, J.R., Li, J. et al.

Nat Chem Biol (2024). 

https://doi.org/10.1038/s41589-024-01660-y

Targeted protein degradation (TPD) is an emerging therapeutic strategy that would benefit from new chemical entities with which to recruit a wider variety of ubiquitin E3 ligases to target proteins for proteasomal degradation. Here we describe a TPD strategy involving the recruitment of FBXO22 to induce degradation of the histone methyltransferase and oncogene NSD2. UNC8732 facilitates FBXO22-mediated degradation of NSD2 in acute lymphoblastic leukemia cells harboring the NSD2 gain-of-function mutation p.E1099K, resulting in growth suppression, apoptosis and reversal of drug resistance. The primary amine of UNC8732 is metabolized to an aldehyde species, which engages C326 of FBXO22 to recruit the SCFFBXO22 Cullin complex. We further demonstrate that a previously reported alkyl amine-containing degrader targeting XIAP is similarly dependent on SCFFBXO22. Overall, we present a potent NSD2 degrader for the exploration of NSD2 disease phenotypes and a new FBXO22-recruitment strategy for TPD.

Evaluation of a Covalent Library of Diverse Warheads (CovLib) Binding to JNK3, USP7, or p53

Klett, T., Schwer, M., Ernst, L. N., Engelhardt, M. U., Jaag, S. J., Masberg, B., … Boeckler, F. M.

Drug Design, Development and Therapy, 2024 18, 2653–2679. https://doi.org/10.2147/DDDT.S466829

Purpose

Over the last few years, covalent fragment-based drug discovery has gained significant importance. Thus, striving for more warhead diversity, we conceived a library consisting of 20 covalently reacting compounds. Our covalent fragment library (CovLib) contains four different warhead classes, including five α-cyanoacacrylamides/acrylates (CA), three epoxides (EO), four vinyl sulfones (VS), and eight electron-deficient heteroarenes with a leaving group (SNAr/SN).

Methods

After predicting the theoretical solubility of the fragments by LogP and LogS during the selection process, we determined their experimental solubility using a turbidimetric solubility assay. The reactivities of the different compounds were measured in a high-throughput 5,5'-dithiobis-(2-nitrobenzoic acid) DTNB assay, followed by a (glutathione) GSH stability assay. We employed the CovLib in a (differential scanning fluorimetry) DSF-based screening against different targets: c-Jun N-terminal kinase 3 (JNK3), ubiquitin-specific protease 7 (USP7), and the tumor suppressor p53. Finally, the covalent binding was confirmed by intact protein mass spectrometry (MS).

Results

In general, the purchased fragments turned out to be sufficiently soluble. Additionally, they covered a broad spectrum of reactivity. All investigated α-cyanoacrylamides/acrylates and all structurally confirmed epoxides turned out to be less reactive compounds, possibly due to steric hindrance and reversibility (for α-cyanoacrylamides/acrylates). The SNAr and vinyl sulfone fragments are either highly reactive or stable. DSF measurements with the different targets JNK3, USP7, and p53 identified reactive fragment hits causing a shift in the melting temperatures of the proteins. MS confirmed the covalent binding mode of all these fragments to USP7 and p53, while additionally identifying the SNAr-type electrophile SN002 as a mildly reactive covalent hit for p53.

Conclusion

The screening and target evaluation of the CovLib revealed first interesting hits. The highly cysteine-reactive fragments VS004, SN001, SN006, and SN007 covalently modify several target proteins and showed distinct shifts in the melting temperatures up to +5.1 °C and −9.1 °C.