Covalent Modifiers

An enantioselective covalent inhibitor of BAX confers cytoprotection in vivo

2026-08-31T06:48:19.135-07:00

Peiwen Shi, Bruno Melillo, Matthew W. McHenry, Christina M. Camara, Ka Yang, Evert Njomen, Marina Godes, Maria F. Pazyra-Murphy, Mary Rose Branch, Bethany Tesar, Rosalind A. Segal, Lee L. Rubin, Michael D. Cameron, Gregory H. Bird, Thomas E. Wales, Steven P. Gygi, Benjamin F. Cravatt, and Loren D. Walensky.

Nat Chem Biol (2026).

https://doi.org/10.1038/s41589-026-02297-9

No therapies directly block apoptosis in tissue injury or the many diseases driven by cell loss. The BCL-2 family protein BAX is a central mediator of this pathway and C126 resides within a key regulatory region where physiologic or pharmacologic ligands can activate or inhibit its function. Here, we report enantioselective covalent BAX inhibitors that site-specifically react with C126 and confer cytoprotection across multiple cell types. These ligands constrain BAX conformation and suppress apoptosis in a strictly BAX-dependent manner. Medicinal chemistry optimization yielded covalent BAX inhibitor 3 (CBI-3), an analog with pharmacokinetics suitable for in vivo studies. In a murine model of Fas-induced fulminant hepatic failure, CBI-3 reduced hepatocyte apoptosis and preserved liver histology and survival. CBI-3 also conferred cytoprotection of motor neurons derived from human induced pluripotent stem cells of healthy and amyotrophic lateral sclerosis donors. These findings establish covalent BAX inhibition as a therapeutic strategy to directly block pathologic cell death.

Enhancing De Novo Designed Peptides and Proteins via Irreversible Covalent Isoquinolinium Capture

2026-08-30T20:45:49.711-07:00

Paul M. Levine, Patrick W. Erickson, Timothy W. Craven, Aaron T. Balana, Derrick R. Hicks, Green Ahn, Chan J. Kim, Lisa S. Brandenburg, Wei Yang, Danielle P. Johnson Erickson,

ACS Chem. Biol. (2026)

https://doi.org/10.1021/acschembio.6c00584

Irreversible covalent inhibitors have garnered significant attention in recent years. Despite encouraging progress, the vast majority contain electrophiles that target the least abundant amino acid, cysteine, substantially limiting target inhibitor design for therapeutic intervention. Here, we generalize 2-ethynylbenzaldehyde as a proximity-induced electrophile for generating irreversible covalent peptide and protein inhibitors that specifically target native lysine residues. Leveraging this warhead, we designed a covalent de novo peptide that potently engages MCL1 to block its interaction with Bak. We show it is faster, more site-selective, and increases potency by 61-fold for MCL1 relative to a sulfonyl fluoride warhead. Additionally, with the guide of a computational script to predict "reactive hotspots" at the protein level, we developed a minibinder that labels PD-L1 in vitro and in live cells, displays a slower off-rate, and potently blocks the native PD-1 and PD-L1. These results establish isoquinolinium capture as a promising strategy to inhibit protein–protein interactions and for the development of novel covalent peptide and protein therapeutics.

Sulfonyl-Imidazopyridines Decouple Reactivity from Stability for Ligandability Mapping and Covalent Inhibitor Discovery

2026-08-30T09:38:03.614-07:00

Zhihong Li; Madeleine L. Ware; Phillip W. Gingrich; Bissan Al-Lazikani; Ku-Lung Hsu *

Journal American Chemical Society (2026)

https://doi.org/10.1021/jacs.6c07487

Covalent probes and therapeutics must balance electrophilicity and stability for function in biological systems, yet gains in stability can sacrifice proteome coverage and limit ligand discovery. Here, we show that single-atom N-to-C substitutions of sulfonyl purines at the nucleofuge position decouple reactivity from stability. Systematic chemical proteomic profiling identifies sulfonyl-imidazopyridines as a class of electrophiles with enhanced cellular and in vivo stability while retaining tunable reactivity toward functional tyrosine and lysine sites. These electrophiles expand access to proteomic sites not engaged by parent sulfonyl-purines or related -triazoles. Importantly, the differential binding of N7- vs N9-sulfonyl-imidazopyridine regioisomer pairs expedites the discovery of proteome-wide-selective inhibitors of metabolic targets, including lanosterol synthase (LSS), phosphoglycerate mutase 1 (PGAM1), and DCTP pyrophosphatase 1 (DCTPP1). Collectively, this work establishes a general strategy for stabilizing electrophiles and introduces a platform for global ligandability mapping guided by regioselective recognition.

Development of Covalent Inhibitors of Chikungunya Virus nsP2 Cysteine Protease Enabled by Direct-to-Biology Synthesis and Screening D

2026-08-25T17:20:18.875-07:00

Zhengjun Cai § ; Kan Li § ; Sainetra Sridhar; Haozhou Tan; Hiwot Demssie; Gaungjin Fan; Wenyi Zhang; Bobby Brooke Herrera; Jun Wang

J. Med. Chem. (2026)

https://doi.org/10.1021/acs.jmedchem.5c03672

Chikungunya virus (CHIKV), an arthropod-borne alphavirus, has emerged as a global health threat due to its rapid transmission and the lack of effective antiviral therapies. The cysteine protease activity of the virus-encoded nonstructural protein 2 (nsP2) is critical for CHIKV replication, as it processes viral polyproteins and counteracts host antiviral defenses, establishing it as a highly attractive target for therapeutic intervention. In this study, we present a rapid drug development platform that integrates covalent docking with direct-to-biology (D2B) synthesis and screening to identify nsP2 inhibitors. Candidates prioritized by in silico docking were synthesized and directly tested in FRET enzymatic assays without purification. This approach led to the identification of several nsP2 inhibitors with diverse chemical scaffolds, potent enzymatic inhibition, and antiviral activity. Together, these findings establish a streamlined strategy for covalent inhibitor development and provide promising leads for CHIKV antiviral development.

Covalent allosteric inhibition of AARS1 lactyltransferase

2026-08-23T18:54:50.497-07:00

Yunyuan Huang, Siying Liu, Luyang Tian, Yang Tang, Yilin Dou, Huiling Wang, Tao Zheng, Mingyang Wang, Runhao Li, Zhi Wang, Zhaocai Zhou, Xin Chen & Jinrong Min

Nature Communications (2026)

https://doi.org/10.1038/s41467-026-76732-9

Alanyl-tRNA synthetase 1 (AARS1) was recently identified as a lactyltransferase responsible for protein lactylation, a modification associated with epigenetic regulation and metabolic adaptation. Here, we report compound XY353, which covalently binds C184 of AARS1, inducing steric clashes with F175 and triggering structural rearrangements in the region that displace W176, a key residue for lactate binding. By means of a combination of a variety of biophysical and enzymatic assays with MD simulations and structural analysis, we show that XY353 and its derivative XY353-1 inhibit AARS1 by competing with lactate via the C184–F175–W176 relay, supporting a covalent allosteric mechanism of inhibition, which is further confirmed by our cellular data that XY353-1 reduces lactylation of the AARS1 substrate YAP and suppresses the proliferation of HGC-27 cells. Collectively, these findings identify a covalent allosteric mechanism for AARS1 inhibition and provide chemical tools to explore its biological functions.

Sulfonyl-Imidazopyridines Decouple Reactivity from Stability for Ligandability Mapping and Covalent Inhibitor Discovery

2026-08-22T12:51:53.693-07:00

Zhihong Li; Madeleine L. Ware; Phillip W. Gingrich; Bissan Al-Lazikani; Ku-Lung Hsu *

Journal American Chemical Society (2026)

https://doi.org/10.1021/jacs.6c07487

Late-stage functionalization with strain-release warheads enables tunable covalent inhibition.

2026-08-15T20:06:26.845-07:00

Zachary P. Shultz, Ansar Lee-Sam, Yun-Pu Chang, Luxin Sun, Dylan Grassie, Alessio Gabellini, Kyle Pedretty, Thomas Scattolin, Victoria Izumi, Bin Fang, Samer Sansil, Ramu Kakumanu, Lukasz Wojtas, John Koomen, Ernst Schönbrunn, Andrii Monastyrskyi, Derek Duckett, and Justin M. Lopchuk.

Science 393,408-416(2026).

DOI:10.1126/science.adx7219

INTRODUCTION

Covalent drugs are transforming targeted therapy by forming durable bonds with disease-driving proteins, yet most rely on a narrow set of reactive groups, particularly acrylamides. These conventional approaches, although effective, can lead to off-target interactions and restrict broader application by their limited structural design. Expanding covalent drug design beyond these established chemotypes is essential to improve both selectivity and therapeutic performance.

RATIONALE

We sought to establish a general platform for replacing acrylamide-based covalent reactive groups in complex drug molecules with alternative chemotypes that offer improved control over reactivity. Our approach centers on bicyclobutanes that are integrated with sulfur-based functional groups commonly used in medicinal chemistry. To enable broad application, we developed a reagent-based strategy that allows these strain-release elements to be installed at the final stage of a synthesis from widely accessible amine precursors. This modular S(IV)-based platform provides a unified entry to multiple sulfur oxidation states and connectivity patterns, enabling systematic tuning of covalent reactivity and target engagement while preserving the parent-drug architecture. By design, this approach allows direct, head-to-head comparison with established covalent inhibitors.

RESULTS

We developed stable, scalable reagents that enable efficient late-stage installation of strain-release bicyclobutane groups across a wide range of clinically relevant scaffolds, including multiple approved kinase inhibitors. This strategy enables direct bioisosteric replacement of acrylamide warheads without modifying the underlying pharmacophore. These S(VI) strain-release groups are highly chemoselective for thiols, and their intrinsic reactivity can be tuned over a broad range through structural modification.

Notably, compounds with similar intrinsic reactivity displayed markedly different levels of target inhibition, demonstrating that productive covalent engagement depends not only on electrophile reactivity but also on molecular orientation within the protein binding site. In cellular systems, the modified inhibitors retained potent activity and effectively suppressed target signaling. Structural analysis confirmed covalent bond formation at the intended site. Across kinase panels and proteome-wide profiling experiments, these strain-release analogs displayed improved selectivity and reduced off-target interactions relative to their acrylamide counterparts. Importantly, these advances translated beyond in vitro systems, with strain-release analogs demonstrating favorable pharmacokinetic properties and efficacy in preclinical in vivo mice models.

CONCLUSION

This work establishes a reagent-enabled, late-stage functionalization platform for the bioisosteric replacement of acrylamides using strain-release bicyclobutanes, bridging chemical innovation to preclinical validation. More broadly, it further supports that effective covalent inhibition is governed not only by intrinsic electrophile reactivity but also by its integration with molecular recognition, providing a framework for designing more selective and clinically effective covalent therapies.

Discovery and Optimization of a WRN Helicase Inhibitor Series through Structure-Guided Drug Design from a Covalent Fragment Binding Insight

2026-08-13T13:43:55.556-07:00

Momar Toure * ; Xin Cindy Yan; Yonghong Bai; Brian A. Sosa-Alvarado; Cen Gao; Theresa Baker; Erin Brophy; John R. Butler; Yuchen Yuan; Michael H. Reutershan; Anthony Tubbs; Laurie Schenkel; Giulia Bottoni; Erica Evans; Peter Hammerman; Allison Drew; Timothy Guzi; Meredeth A. McGowan

J. Med. Chem. (2026) 69 (15): 18162–18181.

https://doi.org/10.1021/acs.jmedchem.6c00443

WRN helicase activity inhibition has emerged as a promising therapeutic approach for targeting cancer cells with specific DNA repair deficiencies, especially those with microsatellite instability (MSI). Herein, we report a novel covalent WRN helicase inhibitor series discovered and optimized by leveraging insights from a covalent fragment investigation. Initial structure-based design led to potency-optimized compounds from this series that exhibited unbound cellular potency in the nanomolar range in both p21 induction and HCT116 CTG viability assays, albeit with high intrinsic warhead reactivity. Further refinement of the ADME properties by modulating the warhead reactivity yielded lead WC-2 with excellent cellular potency, low reactivity toward GSH, excellent plasma and blood stabilities, good oral bioavailability, and long in vivo half-lives in rat (T_1/2 = 7.2 h; F = 62%) and dog (T_1/2 = 18.9 h). WC-2 has the potential as a next-generation, low-dose WRN helicase clinical candidate for treating patients with MSI-classified tumors.

Discovery of a covalent FGFR2-selective inhibitor overcoming clinically-acquired resistance mutations

2026-08-09T15:44:57.798-07:00

Huang, X., Cao, X., Zheng, L. et al.

Nat Commun (2026).

https://doi.org/10.1038/s41467-026-76339-0

Abnormal activation of fibroblast growth factor receptor 2 (FGFR2) drives tumorigenesis in various cancers. Clinical use of pan-FGFR inhibitors is limited due to emerging acquired resistance mutations within the FGFR2 kinase domain and adverse effects associated with FGFR1/4 off-target inhibition. Herein, we describe the structure-based discovery of LC-F2-1, an FGFR2-selective inhibitor that demonstrates irreversible covalent binding to the P-loop. Cellular assays confirm the high selectivity of LC-F2-1 for FGFR2 over FGFR1 and FGFR4, along with potent inhibition of FGFR2 signaling. LC-F2-1 maintains strong activity against clinically observed FGFR2 resistance variants, including gatekeeper, molecular brake, and activation loop variants. X-ray crystallography reveals conformational rearrangement of the kinase domain by LC-F2-1, which overcomes the recalcitrant V565F gatekeeper mutation. In vivo, LC-F2-1 induces tumor regression in xenograft models harboring FGFR2 resistance mutations without affecting serum phosphate levels. In this work, we identify LC-F2-1 as a therapeutic candidate for FGFR2-driven cancers.

A covalent PFKL activator suppresses tumor growth

2026-08-06T05:28:11.786-07:00

Jiang, X.; Lynch, E. M.; Lyu, C.; Wilson, C. N.; Salay, L. E.; Hess, H. T.; Lyons, S. N.; Lu, M.-J.; Luo, S.; Kim, G.; Chan, H.-R.; Wolfe, W. J.; Zacharias, L. G.; Mathews, T. P.; Lin, Y.-C.; Webb, B. A.; Kollman, J. M.; Cambronne, X. A.; Hsu, K.-L.

Nat. Chem. Biol. 2026.

https://doi.org/10.1038/s41589-026-02289-9

Glycolysis fuels vital cellular functions, and its dysregulation has been implicated in cancer, neurodegeneration, antibiotic resistance and diabetes. The glycolytic dependency of cancer, known as the Warburg effect, represents a key vulnerability for development of targeted anticancer agents; however, the development of such agents remains challenging owing to metabolic heterogeneity and resistance. Here we developed a covalent phosphofructokinase-1 liver type (PFKL) activator that couples glycolytic activation with delivery of a cytotoxic carnitine palmitoyltransferase 2 (CPT2)-targeting payload to cancer cells in vitro and in vivo. The electrophile–drug conjugate site-specifically and proteome-wide selectively modifies K677 in the allosteric effector site to stabilize the R-state tetramer of PFKL, while concomitantly releasing a CPT2-selective inhibitor to destabilize cell metabolism. The delivery mechanism of electrophile–drug conjugates is analogous to that of antibody–drug conjugates, but differentiated by their selective covalent targeting of intracellular proteins.

Late-stage functionalization with strain-release warheads enables tunable covalent inhibition

2026-07-27T21:41:06.091-07:00

Science393,408-416(2026).DOI:10.1126/science.adx7219

Structured Abstract

INTRODUCTION

RATIONALE

RESULTS

CONCLUSION

Peptidic Phosphonates as Irreversible Covalent Inhibitors of Plasmodium falciparum Serine Protease PfSUB1.

2026-07-24T11:54:57.432-07:00

Armands Kazia, Elina Lidumniece, Chrislaine Withers-Martinez, Liva Eglite, Owain Donnelly, David A. Fidock, Michael J. Blackman, Aigars Jirgensons;

ACS Med. Chem. Lett. 2026

https://doi.org/10.1021/acsmedchemlett.6c00268

Malaria, caused by Plasmodium parasites, remains a major global health challenge, exacerbated by the widespread emergence of drug-resistant plasmodium strains. Subtilisin-like serine protease SUB1 triggers escape of the parasite from the red cell via a process called egress, rendering the enzyme a prospective antimalarial drug target. While several SUB1 inhibitors have been developed, irreversible covalent inhibition has not been explored so far. In this work, we report our studies of peptidic inhibitors bearing covalent serine traps such as β-lactam, β-lactone, epoxide, and diaryl phosphonate. Out of these, peptidic diaryl phosphonates were found to be irreversible PfSUB1 inhibitors, with the best inhibitor 3b showing a PfSUB1 inhibitory potency (IC50) of 167 nM.

CHARMM-GUI Covalent Ligand Docker as a Web-based Molecular Docking Platform for Covalent Ligands

2026-07-23T07:28:28.551-07:00

Lingyang Kong, Donghyuk Suh, Wonpil Im

bioRxiv 2026.07.13.738313; doi: https://doi.org/10.64898/2026.07.13.738313

Covalent inhibitor research is an emerging topic in drug discovery due to its superior performance in specificity and inhibition effects. While molecular docking is a popular strategy in prediction and assessment of ligand conformations or poses in receptor proteins, covalent ligand docking requires nontrivial preparation efforts, as the ligand structure changes during the covalent complex formation. In order to facilitate molecular docking for covalent ligands, we have developed CHARMM-GUI Covalent Ligand Docker (CGUI-CLD), a new module for covalent ligand docking supported by AutoDock4. CGUI-CLD automates ligand preparation, supports ligand modification, implements docking simulation, and presents results through an intuitive user interface. A knowledge-based library built in CGUI-CLD currently supports 66 warheads and 8 amino acids, which can be used to automate the covalent ligand transformation from a pre-reaction to a post-reaction adduct form seamlessly. Moreover, CHARMM-GUI High-Throughput Simulator is integrated for rapid generation of multiple molecular dynamics simulation systems. CGUI-CLD is expected to significantly reduce a massive workload of covalent ligand docking and advance covalent ligand research.

Covalent remodeling of CRBN creates a non-canonical neosubstrate interface with NTAQ1

2026-07-22T05:53:53.958-07:00

Andres H. de la Peña, Justin T. Cruite, Jianwei Che, Mary E. Matyskiela, Philip P. Chamberlain, Eric S. Fischer, Lyn H. Jones

bioRxiv 2026.07.14.738385;

doi: https://doi.org/10.64898/2026.07.14.738385

Molecular glue degrader EM12-FS covalently modifies cereblon (CRBN) His353, enabling selective recruitment of the neosubstrate NTAQ1 to the CRL4CRBN ubiquitin ligase. We determined the cryo-EM structure of the NTAQ1–EM12-FS–CRBN–DDB1 complex, revealing a non-canonical neosubstrate interface created by covalent remodeling of the CRBN sensor loop. Imidazylation repositions His353 to eliminate the steric clash that prevents NTAQ1 engagement by reversible IMiDs, and the engineered interface is stabilized by a distinctive T-shaped C-H/π interaction between sulfated His353 and NTAQ1 Phe126. Biochemical and mutational analyses define the determinants of ternary complex formation and ubiquitination. These findings show that site-specific synthetic modification of CRBN can reprogram induced-proximity pharmacology, expanding specificity beyond the G-loop degron and establishing a framework for covalent engineering of new degrader modalities.

A covalent irreversible inhibitor binds in two mutually exclusive conformations to the active-site cysteine residue of human aldehyde dehydrogenase 1A3

2026-07-19T19:41:47.466-07:00

Daniela Covaleda, David Vizarraga, Tulsi Upadhyay, Jiyun Zhu, Daniel Abegg, Raquel Pequerul, Martín Hugo, Alexander Adibekian, Ignacio Fita, Xavier Parés, Francesc Xavier Avilés, Matthew Bogyo, Jaume Farrés

doi: https://doi.org/10.64898/2026.07.14.738401

Aldehyde dehydrogenases (ALDH) are enzymes that catalyze the NAD(P)+-dependent oxidation of aldehydes into carboxylic acids, playing roles in detoxification, biosynthesis, and regulatory functions. Dysfunction of ALDH is associated with serious conditions such as alcohol intolerance, cancer, cardiovascular problems, and neurological disorders. In humans, ALDH1A1 and ALDH1A3 isoforms act as retinaldehyde dehydrogenases and are overexpressed in various cancers, where high levels are associated with increased tumor malignancy, cancer stem cell traits, and therapeutic resistance. ALDH1A3 is recognized as a promising target for anticancer therapies, with several inhibitors, mainly reversible, developed to specifically target it or the enzyme family.

Since ALDH enzymes can also display esterase activity, we used this property to develop an in vitro assay specifically targeting the esterase function of ALDH1A3. A highly conserved active-site cysteine in ALDH1A3 is located at the bottom of two converging channels, which define the substrate- and cofactor-binding pockets. To target this catalytic cysteine, we screened a library of 3,200 cysteine-focused covalent fragments. This led to the identification of Z3405279217 (Z34), an acrylamide-based covalent compound that inhibits both ALDH1A1 and ALDH1A3 at sub-micromolar levels. Biochemical and biophysical tests confirmed that Z34 acts as a time-dependent, covalent, and irreversible binder to the active-site cysteine. In this work, we determined the Cryo-EM structure of the ALDH1A3-Z34 complex at 2.26 Å resolution, confirming the covalent attachment to the catalytic cysteine of Z34. Notably, two mutually exclusive covalent binding modes were observed: one occupying the substrate-binding pocket and the other the cofactor-binding region. Z34 displayed unexpected binding modes within the active site and holds promise as a lead compound for future drug development.

A covalent inhibitor targeting Cys-349 of LIMK1 confers selectivity over LIMK2

2026-07-17T14:05:45.478-07:00

Jon B. Patteson, Ioannis Manolaridis, Mee Ra Hong, Jennifer M. Johnston, Samaneh Mesbahi-Vasey, Michael C. Gregory ,Daniel V. Iwamoto John C. Reid John M. Sanders, Ditte Lovatt, Terrence P. McDonald, Valerie W. Shurtleff, Sandra B. Gabelli, Marina Bukhtiyarova

Journal of Biological Chemistry, 2026, 113322,

https://doi.org/10.1016/j.jbc.2026.113322

LIM domain kinase 1 (LIMK1) has been identified as a promising therapeutic target for a variety of conditions, such as chronic pain, open-angle glaucoma, various cancers, schizophrenia, and Fragile X syndrome. However, identifying inhibitors that selectively inhibit LIMK1 over LIM domain kinase 2 (LIMK2) has proven to be challenging. A viable strategy to overcome this difficulty is the development of covalent inhibitors, which can offer both potency and selectivity for LIMK1 due to a reactive cysteine, C349, near the active site absent in its paralog LIMK2. Here we identify an irreversible covalent inhibitor of LIMK1 (cLIMK1i), which is highly selective for LIMK1 over both LIMK2 and a panel of over 100 kinases. A crystal structure of LIMK1 soaked with cLIMK1i reveals it is a type I inhibitor occupying the ATP-binding site with its acrylamide moiety oriented toward the P-loop where C349 resides. Computational modeling supports that the P-loop of LIMK1 can adopt a conformation compatible with covalent bond formation. Biochemical and biophysical characterization of the interaction of cLIMK1i with LIMK1 demonstrates that the covalent bond with LIMK1-C349 is essential for its potent inhibition. These results support covalent inhibition of LIMK1 as a viable strategy for selectively inhibiting LIMK1 over LIMK2 and other kinases.

Machine learning-guided discovery of covalent sortase A inhibitors targeting MRSA virulence

2026-07-14T20:28:29.160-07:00

Xu-liang Xu, Ti-ti Ying, Xiao-wen Wu, Yun-jun Chen, Gang-ao Hu, Yu-tian Guan, Shi-yi Liu, He Wang, Mohamed Seif, Mahmoud Emam, Hong Wang, Wei Hou, Bin Wei,

European Journal of Medicinal Chemistry, 2026, 119139,

https://doi.org/10.1016/j.ejmech.2026.119139

The global rise of methicillin-resistant Staphylococcus aureus (MRSA) has highlighted the urgent need for alternative therapeutic strategies beyond conventional bactericidal antibiotics. Targeting bacterial virulence rather than viability represents a promising approach to mitigate selective pressure and delay resistance development. Sortase A (SrtA), a membrane-associated transpeptidase responsible for anchoring virulence-associated surface proteins, is an attractive anti-virulence target due to its non-essential role in bacterial survival. Here, we report a machine learning-guided strategy for the discovery of novel covalent SrtA inhibitors based on a 1,2-benzoselenazol-3-one (BSEA) scaffold featuring a tunable electrophilic Se–N bond. A scaffold-aware classification model with a Tanimoto similarity constraint trained on 529 SrtA inhibitors enabled prospective virtual screening of over 35,000 BSEA and BTA derivatives, leading to a high hit rate of 89% upon experimental validation. Representative compounds exhibited submicromolar SrtA inhibition (IC50 = 0.84–1.04 μM) while showing minimal effects on bacterial growth (MIC = 8–32 μM), indicating effective functional decoupling of virulence and viability. Mechanistic studies demonstrated time-dependent irreversible inhibition kinetics, supported by jump dilution assays and Nano-LC-MS/MS identification of covalent modification at the catalytic residue Cys184. These inhibitors effectively disrupted MRSA biofilm formation at sub-inhibitory concentrations and significantly improved host survival in a Galleria mellonella infection model. Collectively, this study establishes a data-driven framework integrating machine learning and covalent chemistry for anti-virulence drug discovery and provides promising lead compounds targeting SrtA to combat MRSA infections.

A chemoproteomic atlas of the human purine interactome for regioselective ligand discovery

2026-06-07T20:08:39.986-07:00

Zhihong Li, Hsiao-Kuei Tsai, Adam H. Libby, Michael W. Founds, Olivia L. Murtagh, Madeleine L. Ware, David M. Leace, Wesley J. Wolfe, Phillip W. Gingrich, Bissan Al-Lazikani, Chin-Yuan Chang & Ku-Lung Hsu

Nat Commun (2026).

https://doi.org/10.1038/s41467-026-73407-3

Purines are essential bioactive molecules that interact with a large fraction of the human proteome. Despite their importance, the scope of actionable purine-binding pockets for ligand discovery remains limited. Here, we develop a quantitative chemoproteomics platform using sulfonyl-purine (SuPUR) chemistry to produce a massive and functional map of the human purine interactome. The SuPUR platform captures 31,000+ targetable tyrosine and lysine sites, representing the most comprehensive beyond cysteine chemoproteomics database for enabling protein ligand discovery. SuPUR ligands that bind through a regioselective fashion serve as enabling starting points for developing potent (nanomolar) and proteome-wide-selective modulators of enzymatic and protein-protein interaction function. Phenotypic screening identifies a site-specific (Y237) and regioselective SuPUR ligand of ACAT2 to reveal an unexpected metabolic dependency in cancer cells. A crystal structure of SuPUR ligand-bound ACAT2 reveals the purine group binds deep in the CoA pocket forming key interactions with catalytic residues via a water bridge to guide future structure-based ligand design.

Linking of fragments in neighboring binding sites is one of the optimization strategies in fragment-based drug discovery, where additive or even more substantial bioactivity improvements can be realized. However, such efforts present a considerable challenge when one fragment binds covalently to the target protein, as small modifications can influence the correct positioning of the covalent warhead toward the targeted nucleophilic residue. Here, we present a case study of fragment linking that yielded single-digit micromolar, covalent inhibitors of the SARS-CoV-2 main protease, starting from fragments that were inactive in the biochemical assay. Using structural information from a recent, high-throughput crystallographic fragment screen, we show that the success of fragment linking in the design of targeted covalent inhibitors is heavily impacted by several factors, including the warhead type, the labeling chemistry, and even subtle changes in the designed linker. Notably, we observe that induced fit effects might override the original fragment orientations in the linked molecule, highlighting the need for reliable structure verification, especially in consecutive rounds of fragment elaboration.

2026-05-27T06:25:15.890-07:00

Levente Kollár, Levente M. Mihalovits, Dávid Bajusz, DamijanKnez, József Simon, Blake H. Balcomb, Daren Fearon, Stanislav Gobec, György M. Keserű,

ChemMedChem 2026, 21, e202501108.

https://doi.org/10.1002/cmdc.202501108

Linking of fragments in neighboring binding sites is one of the optimization strategies in fragment-based drug discovery, where additive or even more substantial bioactivity improvements can be realized. However, such efforts present a considerable challenge when one fragment binds covalently to the target protein, as small modifications can influence the correct positioning of the covalent warhead toward the targeted nucleophilic residue. Here, we present a case study of fragment linking that yielded single-digit micromolar, covalent inhibitors of the SARS-CoV-2 main protease, starting from fragments that were inactive in the biochemical assay. Using structural information from a recent, high-throughput crystallographic fragment screen, we show that the success of fragment linking in the design of targeted covalent inhibitors is heavily impacted by several factors, including the warhead type, the labeling chemistry, and even subtle changes in the designed linker. Notably, we observe that induced fit effects might override the original fragment orientations in the linked molecule, highlighting the need for reliable structure verification, especially in consecutive rounds of fragment elaboration.

Characterization of the Second-Generation Covalent Fragment Library (CovLib Gen2): Thiol Reactivity Profiling and p53-Y220C Rescue

2026-05-23T17:16:45.001-07:00

Schwer, M., Aldea, S. R., Engelhardt, M. U., Stahlecker, J., Rheinganz, J., Langkamp, A., & Boeckler, F. M.

Drug Design, Development and Therapy, (2026). 20.

https://doi.org/10.2147/DDDT.S598622

Purpose

Covalent Fragment-Based Drug Discovery (FBDD) has emerged as a powerful strategy for unlocking challenging pharmacological targets and engaging shallow or “cryptic” binding pockets. In this study, we present the design and characterization of the Second Generation Covalent Fragment Library (CovLib Gen2), an expanded collection of 81 structurally diverse electrophiles tailored for Covalent Fragment-Based Drug Discovery (FBDD) using an electrophile-first approach. The library spans five distinct warhead classes, including epoxides, vinyl sulfones, acrylamides, α-cyanoacrylamides, and a core set of SɴAr-reactive heteroarenes.

Methods

We comprehensively profiled the library for physicochemical properties and intrinsic thiol reactivity using high-throughput 5,5’-dithiobis-(2-nitrobenzoic acid) (DTNB) and high-performance liquid chromatography (HPLC)-based glutathione (GSH) reactivity assays. To demonstrate the library’s utility, we performed differential scanning fluorimetry (DSF) screening against the oncogenic, thermally unstable p53-Y220C mutant and subsequent specificity testing with two control mutants.

Results

The library exhibited a broad dynamic range of reactivities with a clear correlation between the assay methods. Additionally, we identified 12 fragments with desirable mild reactivity profiles (t1/2GSH = 1–10 h). The DSF screen yielded 15 hits, primarily SɴAr-reactive heteroarenes and vinyl sulfones. Notably, the fragment SN054 emerged as the most potent stabilizer, inducing a maximal thermal shift of 4.5 °C. Specificity was confirmed using a cysteine-light variant (T-p53C-Y220C-CL), where SN054 retained significant stabilizing activity.

Conclusion

Our findings validate CovLib Gen2 as a versatile tool for ligand discovery, including electrophilic fragments covering a broad range of reactivity, and provide tractable starting points for the pharmacological rescue of p53-Y220C.

Accelerating SuFEx Reactions via Aryl Fluorosulfate Structural Engineering for Enhanced Covalent Targeted Cancer Therapy

2026-05-20T22:38:55.355-07:00

Gao, W.; Zhang, C.; Li, D.; Liu, Y.; Zhao, M.; Xia, X.-X.; Huang, W.; Xia, X.; Yan, D.

Angew. Chem. Int. Ed. 2026

https://doi.org/10.1002/anie.4497440

https://onlinelibrary.wiley.com/doi/full/10.1002/anie.4497440 Aryl fluorosulfate warheads, possessing sulfur(VI) fluoride exchange (SuFEx) reaction, hold significant promise for the development of covalent protein drugs. However, their SuFEx reactivity remains limited within the complex microenvironment of protein interactions. To address this challenge, we sought to enhance their reactivity by adjusting the electronic and steric properties of warheads. Herein, we synthesized various maleimide-functionalized aryl fluorosulfate (MFS) bearing different substituents (e.g., o-F, o-CF3, o-NO2, o-CH3, o-OCH3, o-Cl, o-Br, o-I, 2,6-diF, and m-F), which were then chemically conjugated to Adnectin (an EGFR-targeting protein). The SuFEx reactivity of the resulting xMFS-modified Adnectin was systematically investigated by comparing their covalent cross-linking efficiency to EGFR. Notably, the meta-Fluoro-substituted MFS warhead, featuring moderate electrophilicity and minimal steric hindrance, exhibited the highest reactivity, achieving a 3.5-fold increase in cross-linking efficiency compared to unsubstituted control. The m-F MFS-modified Adnectin was further attached to the surface of albumin-bound DXd. Leveraging its enhanced SuFEx reactivity, the resulting covalent albumin-bound drug exhibited 6.4-fold higher intracellular accumulation, 3.0-fold greater tumor retention, and 4.0-fold higher antitumor efficiency compared to unsubstituted control. Overall, fine-adjusting the electronic and steric properties of warheads significantly enhances their SuFEx reactivity, enabling the rational design of SuFEx-based warheads and facilitating the application in covalent protein drugs.

Covalent Inhibitors of Monoacylglycerol Lipase Induce Conformational Changes and Proteasomal Degradation

2026-05-09T19:10:00.000-07:00

Jordan A. Pham, Thanawat Thaingtamtanha, William McLeish, David Lefebvre, Spencer M. Uguccioni, Roxana Filip, Francesco Gentile, and John Paul Pezacki

J. Am. Chem. Soc. 2026

https://doi.org/10.1021/jacs.5c22859

Monoacylglycerol lipase (MGLL) is a key serine hydrolase that regulates 2-arachidonoylglycerol (2-AG) and eicosanoid signaling. Inhibition of MGLL blocks the conversion of 2-AG into arachidonic acid (AA) with broad therapeutic implications in inflammation, cancer, and viral infection. Carbamate/urea inhibitors such as MJN110, JZL184, and SAR629 are widely used to irreversibly inhibit MGLL through covalent modification of the catalytic serine residue. Here, we demonstrate that this inhibitor class also induces proteasome-dependent degradation of MGLL, functioning as monovalent degraders. We show that loss of MGLL following covalent inhibitor treatment is dependent on the 26S proteasome, while detailed simulations of MGLL dynamics following inhibitor binding suggest that these inhibitors do not destabilize their protein target but instead induce conformational changes that likely facilitate polyubiquitination by exposing two lysine residues. Taken together, these findings establish carbamate/urea inhibitors as dual functional molecules with the propensity to both covalently inhibit their target and act as structural degraders, potentially functioning as monovalent molecular glues, highlighting the need to evaluate the degradation potential alongside inhibitory potency in future screening and drug discovery.

Development and Structural Characterization of UTE-156, a Covalent Inhibitor of the VCP/p97 AAA+ ATPase

2026-05-08T06:37:00.000-07:00

Tamayo-Jaramillo D, Hegde S, Jia X, Coffman K, Vankayalapati H, Bearss D, Jones KB, Stark AW, Shen PS.

Adv Sci. 2026; 13(25):e20545.

https://doi.org/10.1002/advs.202520545

The AAA+ ATPase valosin-containing protein (VCP/p97) is a central regulator of protein homeostasis that is well characterized for its role in extracting and remodeling ubiquitinated substrates. Dysregulation of VCP activity contributes to the pathogenesis of neurodegenerative diseases and cancer, making it an important therapeutic target. Here, we report the development and characterization of UTE-156, a novel covalent small-molecule inhibitor that modifies Cys522 within the D2 ATPase domain of VCP. UTE-156 potently inhibits VCP ATPase activity, while losing activity against a C522A mutant, supporting a covalent mechanism of action. High-resolution cryo-electron microscopy (cryo-EM) structures reveal that UTE-156 occupies the D2 nucleotide-binding site, sterically blocking ATP binding and inducing conformational remodeling of the pocket. Biochemical and cell-based assays demonstrate strong inhibitory potency but limited solubility and rapid metabolic turnover. These pharmacochemical limitations preclude immediate therapeutic use but underscore its value as a chemical probe. Together, these findings establish UTE-156 as a powerful tool for dissecting VCP function and provide a framework for future optimization of covalent modulators of protein homeostasis.

Nitro-Diphenyl Ethers as Emerging Cysteine-Targeting Covalent Warheads Enable Identification of Novel Target LDLRAP1 for Anticoronaviral Activity

2026-05-08T05:49:00.000-07:00

Zeyue Huang, Xiuqi Hu, Zheng Liu, Hongxuan Cao, Yunjie Xiang, Jian Wan, Ivailo Slavchev, Li Rao, Ivanka Nikolova, Petar Grozdanov, Nadya Nikolova, Georgi M. Dobrikov, and Yanliang Ren

Journal of Medicinal Chemistry 2026

DOI: 10.1021/acs.jmedchem.5c03394

Targeted covalent inhibitors (TCIs) are powerful tools in drug discovery, but the high intrinsic reactivity of conventional warheads often compromises selectivity and increases the off-target liability. Here, we reported nitrodiphenyl-ether compounds as a novel irreversible and released-type covalent warhead with exceptionally low reactivity that potently inhibits coronavirus HCoV-OC43 infection. To identify their molecular targets, we designed a panel of active and inactive alkyne-tagged probes and performed chemical proteomic profiling in human host cells. An integrated approach combining activity- and inactivity-based proteome profiling (AIBPP), competitive ABPP, LC–MS/MS, and fluorescence polarization (FP) assays identified low-density lipoprotein receptor adapter protein 1 (LDLRAP1) as the primary target, modified selectively at C119, thereby disrupting the LDLR–LDLRAP1 interaction. Inhibition of this interaction strongly correlated with antiviral efficacy, confirming LDLRAP1 as the functional target. Collectively, this study establishes LDLRAP1 as an unexploited host antiviral target and expands the repertoire of cysteine-targeted covalent warheads for host-directed therapy.

Shifting the PPARγ conformational ensemble toward a transcriptionally repressive state improves covalent inhibitor efficacy

2026-05-07T13:32:00.000-07:00

Liudmyla Arifova, Brian S MacTavish, Zane Laughlin, Mithun Nag, Karadi Giridhar, Jinsai Shang, Min-Hsuan Li, Xiaoyu Yu, Di Zhu, Theodore M Kamenecka, Douglas J Kojetin,

eLife 2025 14:RP106697

https://doi.org/10.7554/eLife.106697.2

The nuclear receptor peroxisome proliferator-activated receptor gamma (PPARγ) regulates transcription in response to ligand binding at an orthosteric pocket within the ligand-binding domain (LBD). We previously showed that two covalent ligands, T0070907 and GW9662—extensively used as PPARγ inhibitors to assess off-target activity—weaken but do not completely block ligand binding via an allosteric mechanism associated with pharmacological inverse agonism (Shang et al., 2024). These covalent inhibitors shift the LBD towards a repressive conformation, where the activation function-2 (AF-2) helix 12 occupies the orthosteric pocket, competing with orthosteric ligand binding. Here, we provide additional support for this allosteric mechanism using two covalent inverse agonists, SR33065 and SR36708, which better stabilize the repressive LBD conformation and are more effective inhibitors of—but also do not completely inhibit—ligand cobinding. Furthermore, we show that ligand cobinding can occur with a previously reported PPARγ dual-site covalent inhibitor, SR16832, which appears to weaken ligand binding through a direct mechanism independent of the allosteric mechanism. These findings underscore the complex nature of the PPARγ LBD conformational ensemble and highlight the need to develop alternative methods for designing more effective covalent inhibitors.