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Liu J, Lukka PB, Ektnitphong VA, Parmar KR, Wagh S, Lu Y, Lee RB, Scherbakov D, Wang H, Zimmerman MD, Meibohm B, Robertson GT, Dartois V, Böttger EC, Lenaerts AJ, Lee RE. Enhancing the therapeutic window for Spectinamide anti-tuberculosis Agents: Synthesis, Evaluation, and activation of phosphate prodrug 3408. Bioorg Med Chem Lett 2024; 112:129934. [PMID: 39214506 PMCID: PMC11403708 DOI: 10.1016/j.bmcl.2024.129934] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2024] [Revised: 08/19/2024] [Accepted: 08/27/2024] [Indexed: 09/04/2024]
Abstract
Spectinamides are a novel class of narrow-spectrum antitubercular agents with the potential to treat drug-resistant tuberculosis infections. Spectinamide 1810 has shown a good safety record following subcutaneous injection in mice or infusion in rats but exhibits transient acute toxicity following bolus administration in either species. To improve the therapeutic index of 1810, an injectable prodrug strategy was explored. The injectable phosphate prodrug 3408 has a superior maximum tolerated dose compared to 1810 or Gentamicin. Following intravenous administration in rodents, prodrug 3408 was quickly converted to 1810. The resulting 1810 exposure and pharmacokinetic profile after 3408 administration was identical to equivalent molar amounts of 1810 given directly by intravenous administration. 3408 and the parent 1810 exhibited similar overall efficacy in a BALB/c acute tuberculosis efficacy model. Delivery of 1810 in phosphate prodrug form, therefore, holds the potential to improve further the therapeutic index of an already promising tuberculosis antibiotic.
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Lee RE, Yoshida M. Winners of the 2022 JA Ōmura Awards for excellence. J Antibiot (Tokyo) 2024:10.1038/s41429-024-00767-7. [PMID: 39354163 DOI: 10.1038/s41429-024-00767-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2024] [Accepted: 08/01/2024] [Indexed: 10/04/2024]
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Bauman AA, Sarathy JP, Kaya F, Massoudi LM, Scherman MS, Hastings C, Liu J, Xie M, Brooks EJ, Ramey ME, Jones IL, Benedict ND, Maclaughlin MR, Miller-Dawson JA, Waidyarachchi SL, Butler MM, Bowlin TL, Zimmerman MD, Lenaerts AJ, Meibohm B, Gonzalez-Juarrero M, Lyons MA, Dartois V, Lee RE, Robertson GT. Spectinamide MBX-4888A exhibits favorable lesion and tissue distribution and promotes treatment shortening in advanced murine models of tuberculosis. Antimicrob Agents Chemother 2024:e0071624. [PMID: 39345140 DOI: 10.1128/aac.00716-24] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2024] [Accepted: 09/08/2024] [Indexed: 10/01/2024] Open
Abstract
The spectinamides are novel, narrow-spectrum semisynthetic analogs of spectinomycin, modified to avoid intrinsic efflux by Mycobacterium tuberculosis. Spectinamides, including lead MBX-4888A (Lee-1810), exhibit promising therapeutic profiles in mice, as single drugs and as partner agents with other anti-tuberculosis antibiotics including rifampin and/or pyrazinamide. Here, we show that MBX-4888A, given by injection with the front-line standard of care regimen, is treatment shortening in multiple murine tuberculosis infection models. The positive treatment responses to MBX-4888A combination therapy in multiple mouse models, including mice exhibiting advanced pulmonary disease, can be attributed to favorable distribution in tissues and lesions, retention in caseum, along with favorable effects with rifampin and pyrazinamide under conditions achieved in necrotic lesions. This study also provides an additional data point regarding the safety and tolerability of spectinamide MBX-4888A in long-term murine efficacy studies.
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Marreddy RKR, Phelps GA, Churion K, Picker J, Powell R, Cherian PT, Bowling JJ, Stephan CC, Lee RE, Hurdle JG. Chemical genetic analysis of enoxolone inhibition of C. difficile toxin production reveals adenine deaminase and ATP synthase as anti-virulence targets. J Biol Chem 2024:107839. [PMID: 39343002 DOI: 10.1016/j.jbc.2024.107839] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2024] [Revised: 09/06/2024] [Accepted: 09/20/2024] [Indexed: 10/01/2024] Open
Abstract
Toxins TcdA and TcdB are the main virulence factors of Clostridioides difficile, a leading cause of hospital-acquired diarrhea. Despite their importance, there is a significant knowledge gap of druggable targets for inhibiting toxin production. To address this, we screened non-antibiotic phytochemicals to identify potential chemical genetic probes to discover anti-virulence drug targets. This led to the identification of 18β-glycyrrhetinic acid (enoxolone), a licorice metabolite, as an inhibitor of TcdA and TcdB biosynthesis. Using affinity-based proteomics, potential targets were identified as ATP synthase subunit alpha (AtpA) and adenine deaminase (Ade, which catalyzes conversion of adenine to hypoxanthine in the purine salvage pathway). To validate these targets, a multi-faceted approach was adopted. Gene silencing of ade and atpA inhibited toxin biosynthesis, while SPR and ITC molecular interaction analyses revealed direct binding of enoxolone to Ade. Metabolomics demonstrated enoxolone induced the accumulation of adenosine, while depleting hypoxanthine and ATP in C. difficile. Transcriptomics further revealed enoxolone dysregulated phosphate uptake genes, which correlated with reduced cellular phosphate levels. These findings suggest that enoxolone's cellular action is multi-targeted. Accordingly, supplementation with both hypoxanthine and triethyl phosphate (TEP), a phosphate source, was required to fully restore toxin production in the presence of enoxolone. In conclusion, through the characterization of enoxolone, we identified promising anti-virulence targets that interfere with nucleotide salvage and ATP synthesis, which may also block toxin biosynthesis.
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Dharuman S, Phelps GA, Dunn CM, Wilt LA, Murphy PA, Lee RB, Snoke HE, Selchow P, Haldimann K, Böttger EC, Hobbie SN, Sander P, Lee RE. Synthesis and antibacterial action of 3',6'-disubstituted spectinomycins. J Antibiot (Tokyo) 2024; 77:577-588. [PMID: 38890386 PMCID: PMC11347369 DOI: 10.1038/s41429-024-00750-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2024] [Revised: 05/22/2024] [Accepted: 05/24/2024] [Indexed: 06/20/2024]
Abstract
Spectinomycin is an aminocyclitol antibiotic with a unique ribosomal binding site. Prior synthetic modifications of spectinomycin have enhanced potency and antibacterial spectrum through addition at the 6'-position to produce trospectomycin and to the 3'-position to produce spectinamides and aminomethyl spectinomycins. This study focused on the design, synthesis, and evaluation of three 3',6'-disubstituted spectinomycin analogs: trospectinamide, N-benzyl linked aminomethyl, and N-ethylene linked aminomethyl trospectomycins. Computational experiments predicted that these disubstituted analogs would be capable of binding within the SPC ribosomal binding site. The new analogs were synthesized from trospectomycin, adapting the previously established routes for the spectinamide and aminomethyl spectinomycin series. In a cell-free translation assay, the disubstituted analogs showed ribosomal inhibition similar to spectinomycin or trospectomycin. These disubstituted analogs demonstrated inhibitory MIC activity against various bacterial species with the 3'-modification dictating spectrum of activity, leading to improved activity against mycobacterium species. Notably, N-ethylene linked aminomethyl trospectomycins exhibited increased potency against Mycobacterium abscessus and trospectinamide displayed robust activity against M. tuberculosis, aligning with the selective efficacy of spectinamides. The study also found that trospectomycin is susceptible to efflux in M. tuberculosis and M. abscessus. These findings contribute to the understanding of the structure-activity relationship of spectinomycin analogs and can guide the design and synthesis of more effective spectinomycin compounds.
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Tangallapally R, Subramanian C, Yun MK, Edwards A, Sharma LK, Yang L, Creed K, Wang J, Jackowski S, Rock CO, White SW, Lee RE. Development of Brain Penetrant Pyridazine Pantothenate Kinase Activators. J Med Chem 2024; 67:14432-14442. [PMID: 39136313 PMCID: PMC11345825 DOI: 10.1021/acs.jmedchem.4c01211] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2024] [Revised: 08/05/2024] [Accepted: 08/06/2024] [Indexed: 08/23/2024]
Abstract
Conversion of pantothenate to phosphopantothenate in humans is the first dedicated step in the coenzyme A (CoA) biosynthesis pathway and is mediated by four isoforms of pantothenate kinase. These enzymes are allosterically regulated by acyl-CoA levels, which control the rate of CoA biosynthesis. Small molecule activators of the PANK enzymes that overcome feedback suppression increase CoA levels in cultured cells and animals and have shown great potential for the treatment of pantothenate kinase-associated neurodegeneration and propionic acidemias. In this study, we detail the further optimization of PANK pyridazine activators using structure-guided design and focus on the cellular CoA activation potential, metabolic stability, and solubility as the primary drivers of the structure-activity relationship. These studies led to the prioritization of three late-stage preclinical lead PANK modulators with improved pharmacokinetic profiles and the ability to substantially increase brain CoA levels. Compound 22 (BBP-671) eventually advanced into clinical testing for the treatment of PKAN and propionic acidemia.
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Lewis K, Lee RE, Brötz-Oesterhelt H, Hiller S, Rodnina MV, Schneider T, Weingarth M, Wohlgemuth I. Sophisticated natural products as antibiotics. Nature 2024; 632:39-49. [PMID: 39085542 DOI: 10.1038/s41586-024-07530-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2022] [Accepted: 05/07/2024] [Indexed: 08/02/2024]
Abstract
In this Review, we explore natural product antibiotics that do more than simply inhibit an active site of an essential enzyme. We review these compounds to provide inspiration for the design of much-needed new antibacterial agents, and examine the complex mechanisms that have evolved to effectively target bacteria, including covalent binders, inhibitors of resistance, compounds that utilize self-promoted entry, those that evade resistance, prodrugs, target corrupters, inhibitors of 'undruggable' targets, compounds that form supramolecular complexes, and selective membrane-acting agents. These are exemplified by β-lactams that bind covalently to inhibit transpeptidases and β-lactamases, siderophore chimeras that hijack import mechanisms to smuggle antibiotics into the cell, compounds that are activated by bacterial enzymes to produce reactive molecules, and antibiotics such as aminoglycosides that corrupt, rather than merely inhibit, their targets. Some of these mechanisms are highly sophisticated, such as the preformed β-strands of darobactins that target the undruggable β-barrel chaperone BamA, or teixobactin, which binds to a precursor of peptidoglycan and then forms a supramolecular structure that damages the membrane, impeding the emergence of resistance. Many of the compounds exhibit more than one notable feature, such as resistance evasion and target corruption. Understanding the surprising complexity of the best antimicrobial compounds provides a roadmap for developing novel compounds to address the antimicrobial resistance crisis by mining for new natural products and inspiring us to design similarly sophisticated antibiotics.
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Ali MZ, Dutt TS, MacNeill A, Walz A, Pearce C, Lam H, Philp J, Patterson J, Henao-Tamayo M, Lee RE, Liu J, Robertson GT, Hickey AJ, Meibohm B, Gonzalez-Juarrero M. A Modified BPaL Regimen for Tuberculosis Treatment replaces Linezolid with Inhaled Spectinamides. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2023.11.16.567434. [PMID: 38014249 PMCID: PMC10680823 DOI: 10.1101/2023.11.16.567434] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2023]
Abstract
The Nix-TB clinical trial evaluated a new 6-month regimen containing three-oral- drugs; bedaquiline (B), pretomanid (Pa) and linezolid (L) (BPaL regimen) for treatment of tuberculosis (TB). This regimen achieved remarkable results as almost 90% of the multidrug resistant (MDR) or extensively drug resistant (XDR) TB participants were cured but many patients also developed severe adverse events (AEs). The AEs were associated with the long-term administration of the protein synthesis inhibitor linezolid. Spectinamide 1599 is also a protein synthesis inhibitor of Mycobacterium tuberculosis with an excellent safety profile but which lacks oral bioavailability. Here, we propose to replace L in the BPaL regimen with spectinamide (S) administered via inhalation and we demonstrate that inhaled spectinamide 1599, combined with BPa --BPaS regimen--has similar efficacy to that of BPaL regimen while simultaneously avoiding the L-associated AEs. The BPaL and BPaS regimens were compared in the BALB/c and C3HeB/FeJ murine chronic TB efficacy models. After 4-weeks of treatment, both regimens promoted equivalent bactericidal effect in both TB murine models. However, treatment with BPaL resulted in significant weight loss and the complete blood count suggested development of anemia. These effects were not similarly observed in mice treated with BPaS. BPaL and BPa, but no the BPaS treatment, also decreased myeloid to erythroid ratio suggesting the S in the BPaS regimen was able to recover this effect. Moreover, the BPaL also increased concentration of proinflammatory cytokines in bone marrow compared to mice receiving BPaS regimen. During therapy both regimens improved the lung lesion burden, reduced neutrophil and cytotoxic T cells counts while increased the number of B and helper and regulatory T cells. These combined data suggest that inhaled spectinamide 1599 combined with BPa is an effective TB regimen that avoids L-associated AEs. IMPORTANCE Tuberculosis (TB) is an airborne infectious disease that spreads via aerosols containing Mycobacterium tuberculosis (Mtb), the causative agent of TB. TB can be cured by administration of 3-4 drugs for 6-9 months but there are limited treatment options for patients infected with multidrug (MDR) and extensively resistant (XDR) strains of Mtb. BPaL is a new all-oral combination of drugs consisting of Bedaquiline (B), Pretomanid (Pa) and Linezolid (L). This regimen was able to cure ∼90% of MDR and XDR TB patients in clinical trials but many patients developed severe adverse events (AEs) associated to the long-term administration of linezolid. We evaluated a new regimen in which Linezolid in the BPaL regimen was replaced with inhaled spectinamide 1599. In the current study, we demonstrate that 4-weeks of treatment with inhaled spectinamide 1599 in combination with Bedaquiline and Pretomanid has equivalent efficacy to the BPaL drug combination and avoids the L-associated-AEs.
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Bauman AA, Sarathy JP, Kaya F, Massoudi LM, Scherman MS, Hastings C, Liu J, Xie M, Brooks EJ, Ramey ME, Jones IL, Benedict ND, Maclaughlin MR, Miller-Dawson JA, Waidyarachchi SL, Butler MM, Bowlin TL, Zimmerman MD, Lenaerts AJ, Meibohm B, Gonzalez-Juarrero M, Lyons MA, Dartois V, Lee RE, Robertson GT. Spectinamide MBX-4888A exhibits favorable lesion and tissue distribution and promotes treatment shortening in advanced murine models of tuberculosis. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.05.13.593953. [PMID: 38798577 PMCID: PMC11118289 DOI: 10.1101/2024.05.13.593953] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2024]
Abstract
The spectinamides are novel, narrow-spectrum semisynthetic analogs of spectinomycin, modified to avoid intrinsic efflux by Mycobacterium tuberculosis . Spectinamides, including lead MBX-4888A (Lee-1810), exhibit promising therapeutic profiles in mice, as single drugs and as partner agents with other anti-tuberculosis antibiotics including rifampin and/or pyrazinamide. To demonstrate that this translates to more effective cure, we first confirmed the role of rifampin, with or without pyrazinamide, as essential to achieve effective bactericidal responses and sterilizing cure in the current standard of care regimen in chronically infected C3HeB/FeJ mice compared to BALB/c mice. Thus, demonstrating added value in testing clinically relevant regimens in murine models of increasing pathologic complexity. Next we show that MBX-4888A, given by injection with the front-line standard of care regimen, is treatment shortening in multiple murine tuberculosis infection models. The positive treatment responses to MBX-4888A combination therapy in multiple mouse models including mice exhibiting advanced pulmonary disease can be attributed to favorable distribution in tissues and lesions, retention in caseum, along with favorable effects with rifampin and pyrazinamide under conditions achieved in necrotic lesions. This study also provides an additional data point regarding the safety and tolerability of spectinamide MBX-4888A in long-term murine efficacy studies.
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Zhou Y, Phelps GA, Mangrum MM, McLeish J, Phillips EK, Lou J, Ancajas CF, Rybak JM, Oelkers PM, Lee RE, Best MD, Reynolds TB. The small molecule CBR-5884 inhibits the Candida albicans phosphatidylserine synthase. mBio 2024; 15:e0063324. [PMID: 38587428 PMCID: PMC11077991 DOI: 10.1128/mbio.00633-24] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2024] [Accepted: 03/12/2024] [Indexed: 04/09/2024] Open
Abstract
Systemic infections by Candida spp. are associated with high mortality rates, partly due to limitations in current antifungals, highlighting the need for novel drugs and drug targets. The fungal phosphatidylserine synthase, Cho1, from Candida albicans is a logical antifungal drug target due to its importance in virulence, absence in the host, and conservation among fungal pathogens. Inhibitors of Cho1 could serve as lead compounds for drug development, so we developed a target-based screen for inhibitors of purified Cho1. This enzyme condenses serine and cytidyldiphosphate-diacylglycerol (CDP-DAG) into phosphatidylserine (PS) and releases cytidylmonophosphate (CMP). Accordingly, we developed an in vitro nucleotidase-coupled malachite-green-based high throughput assay for purified C. albicans Cho1 that monitors CMP production as a proxy for PS synthesis. Over 7,300 molecules curated from repurposing chemical libraries were interrogated in primary and dose-responsivity assays using this platform. The screen had a promising average Z' score of ~0.8, and seven compounds were identified that inhibit Cho1. Three of these, ebselen, LOC14, and CBR-5884, exhibited antifungal effects against C. albicans cells, with fungicidal inhibition by ebselen and fungistatic inhibition by LOC14 and CBR-5884. Only CBR-5884 showed evidence of disrupting in vivo Cho1 function by inducing phenotypes consistent with the cho1∆∆ mutant, including a reduction of cellular PS levels. Kinetics curves and computational docking indicate that CBR-5884 competes with serine for binding to Cho1 with a Ki of 1,550 ± 245.6 nM. Thus, this compound has the potential for development into an antifungal compound. IMPORTANCE Fungal phosphatidylserine synthase (Cho1) is a logical antifungal target due to its crucial role in the virulence and viability of various fungal pathogens, and since it is absent in humans, drugs targeted at Cho1 are less likely to cause toxicity in patients. Using fungal Cho1 as a model, there have been two unsuccessful attempts to discover inhibitors for Cho1 homologs in whole-cell screens prior to this study. The compounds identified in these attempts do not act directly on the protein, resulting in the absence of known Cho1 inhibitors. The significance of our research is that we developed a high-throughput target-based assay and identified the first Cho1 inhibitor, CBR-5884, which acts both on the purified protein and its function in the cell. This molecule acts as a competitive inhibitor with a Ki value of 1,550 ± 245.6 nM and, thus, has the potential for development into a new class of antifungals targeting PS synthase.
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Zhou J, Qian Y, Lang Y, Zhang Y, Tao X, Moya B, Sayed ARM, Landersdorfer CB, Shin E, Werkman C, Smith NM, Kim TH, Kumaraswamy M, Shin BS, Tsuji BT, Bonomo RA, Lee RE, Bulitta JB. Comprehensive stability analysis of 13 β-lactams and β-lactamase inhibitors in in vitro media, and novel supplement dosing strategy to mitigate thermal drug degradation. Antimicrob Agents Chemother 2024; 68:e0139923. [PMID: 38329330 PMCID: PMC10916406 DOI: 10.1128/aac.01399-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2023] [Accepted: 01/06/2024] [Indexed: 02/09/2024] Open
Abstract
Non-clinical antibiotic development relies on in vitro susceptibility and infection model studies. Validating the achievement of the targeted drug concentrations is essential to avoid under-estimation of drug effects and over-estimation of resistance emergence. While certain β-lactams (e.g., imipenem) and β-lactamase inhibitors (BLIs; clavulanic acid) are believed to be relatively unstable, limited tangible data on their stability in commonly used in vitro media are known. We aimed to determine the thermal stability of 10 β-lactams and 3 BLIs via LC-MS/MS in cation-adjusted Mueller Hinton broth at 25 and 36°C as well as agar at 4 and 37°C, and in water at -20, 4, and 25°C. Supplement dosing algorithms were developed to achieve broth concentrations close to their target over 24 h. During incubation in broth (pH 7.25)/agar, degradation half-lives were 16.9/21.8 h for imipenem, 20.7/31.6 h for biapenem, 29.0 h for clavulanic acid (studied in broth only), 23.1/71.6 h for cefsulodin, 40.6/57.9 h for doripenem, 46.5/64.6 h for meropenem, 50.8/97.7 h for cefepime, 61.5/99.5 h for piperacillin, and >120 h for all other compounds. Broth stability decreased at higher pH. All drugs were ≥90% stable for 72 h in agar at 4°C. Degradation half-lives in water at 25°C were >200 h for all drugs except imipenem (14.7 h, at 1,000 mg/L) and doripenem (59.5 h). One imipenem supplement dose allowed concentrations to stay within ±31% of their target concentration. This study provides comprehensive stability data on β-lactams and BLIs in relevant in vitro media using LC-MS/MS. Future studies are warranted applying these data to antimicrobial susceptibility testing and assessing the impact of β-lactamase-related degradation.
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Phelps GA, Cheramie MN, Fernando DM, Selchow P, Meyer CJ, Waidyarachchi SL, Dharuman S, Liu J, Meuli M, Molin MD, Killam BY, Murphy PA, Reeve SM, Wilt LA, Anderson SM, Yang L, Lee RB, Temrikar ZH, Lukka PB, Meibohm B, Polikanov YS, Hobbie SN, Böttger EC, Sander P, Lee RE. Development of 2nd generation aminomethyl spectinomycins that overcome native efflux in Mycobacterium abscessus. Proc Natl Acad Sci U S A 2024; 121:e2314101120. [PMID: 38165935 PMCID: PMC10786304 DOI: 10.1073/pnas.2314101120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2023] [Accepted: 11/11/2023] [Indexed: 01/04/2024] Open
Abstract
Mycobacterium abscessus (Mab), a nontuberculous mycobacterial (NTM) species, is an emerging pathogen with high intrinsic drug resistance. Current standard-of-care therapy results in poor outcomes, demonstrating the urgent need to develop effective antimycobacterial regimens. Through synthetic modification of spectinomycin (SPC), we have identified a distinct structural subclass of N-ethylene linked aminomethyl SPCs (eAmSPCs) that are up to 64-fold more potent against Mab over the parent SPC. Mechanism of action and crystallography studies demonstrate that the eAmSPCs display a mode of ribosomal inhibition consistent with SPC. However, they exert their increased antimicrobial activity through enhanced accumulation, largely by circumventing efflux mechanisms. The N-ethylene linkage within this series plays a critical role in avoiding TetV-mediated efflux, as lead eAmSPC 2593 displays a mere fourfold susceptibility improvement against Mab ΔtetV, in contrast to the 64-fold increase for SPC. Even a minor shortening of the linkage by a single carbon, akin to 1st generation AmSPC 1950, results in a substantial increase in MICs and a 16-fold rise in susceptibility against Mab ΔtetV. These shifts suggest that longer linkages might modify the kinetics of drug expulsion by TetV, ultimately shifting the equilibrium towards heightened intracellular concentrations and enhanced antimicrobial efficacy. Furthermore, lead eAmSPCs were also shown to synergize with various classes of anti-Mab antibiotics and retain activity against clinical isolates and other mycobacterial strains. Encouraging pharmacokinetic profiles coupled with robust efficacy in Mab murine infection models suggest that eAmSPCs hold the potential to be developed into treatments for Mab and other NTM infections.
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Subramanian C, Frank MW, Sukhun R, Henry CE, Wade A, Harden ME, Rao S, Tangallapally R, Yun MK, White SW, Lee RE, Sinha U, Rock CO, Jackowski S. Pantothenate Kinase Activation Restores Brain Coenzyme A in a Mouse Model of Pantothenate Kinase-Associated Neurodegeneration. J Pharmacol Exp Ther 2024; 388:171-180. [PMID: 37875310 DOI: 10.1124/jpet.123.001919] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2023] [Accepted: 09/28/2023] [Indexed: 10/26/2023] Open
Abstract
Pantothenate kinase-associated neurodegeneration (PKAN) is characterized by a motor disorder with combinations of dystonia, parkinsonism, and spasticity, leading to premature death. PKAN is caused by mutations in the PANK2 gene that result in loss or reduction of PANK2 protein function. PANK2 is one of three kinases that initiate and regulate coenzyme A biosynthesis from vitamin B5, and the ability of BBP-671, an allosteric activator of pantothenate kinases, to enter the brain and elevate coenzyme A was investigated. The metabolic stability, protein binding, and membrane permeability of BBP-671 all suggest that it has the physical properties required to cross the blood-brain barrier. BBP-671 was detected in plasma, liver, cerebrospinal fluid, and brain following oral administration in rodents, demonstrating the ability of BBP-671 to penetrate the brain. The pharmacokinetic and pharmacodynamic properties of orally administered BBP-671 evaluated in cannulated rats showed that coenzyme A (CoA) concentrations were elevated in blood, liver, and brain. BBP-671 elevation of whole-blood acetyl-CoA served as a peripheral pharmacodynamic marker and provided a suitable method to assess target engagement. BBP-671 treatment elevated brain coenzyme A concentrations and improved movement and body weight in a PKAN mouse model. Thus, BBP-671 crosses the blood-brain barrier to correct the brain CoA deficiency in a PKAN mouse model, resulting in improved locomotion and survival and providing a preclinical foundation for the development of BBP-671 as a potential treatment of PKAN. SIGNIFICANCE STATEMENT: The blood-brain barrier represents a major hurdle for drugs targeting brain metabolism. This work describes the pharmacokinetic/pharmacodynamic properties of BBP-671, a pantothenate kinase activator. BBP-671 crosses the blood-brain barrier to correct the neuron-specific coenzyme A (CoA) deficiency and improve motor function in a mouse model of pantothenate kinase-associated neurodegeneration. The central role of CoA and acetyl-CoA in intermediary metabolism suggests that pantothenate kinase activators may be useful in modifying neurological metabolic disorders.
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Hausmann LRM, Cohen AJ, Eliacin J, Gurewich DA, Lee RE, McCoy JL, Meterko M, Michaels Z, Moy EM, Procario GT, Russell LE, Schaefer JH. Developing a brief assessment of social risks for the Veterans Health Administration Survey of Healthcare Experiences of Patients. Health Serv Res 2023; 58:1209-1223. [PMID: 37674359 PMCID: PMC10622278 DOI: 10.1111/1475-6773.14220] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/08/2023] Open
Abstract
OBJECTIVE To determine whether a 6- or 12-month look-back period affected rates of reported social risks in a social risk survey for use in the Veterans Health Administration and to assess associations of social risks with overall health and mental health. STUDY DESIGN Cross-sectional survey of respondents randomized to 6- or 12-month look-back period. DATA SOURCES AND STUDY SETTING Online survey with a convenience sample of Veterans in June and July 2021. DATA COLLECTION/EXTRACTION METHODS Veteran volunteers were recruited by email to complete a survey assessing social risks, including financial strain, adult caregiving, childcare, food insecurity, housing, transportation, internet access, loneliness/isolation, stress, discrimination, and legal issues. Outcomes included self-reported overall health and mental health. Chi-squared tests compared the prevalence of reported social risks between 6- and 12-month look-back periods. Spearman correlations assessed associations among social risks. Bivariate and multivariable logistic regression models estimated associations between social risks and fair/poor overall and mental health. PRINCIPAL FINDINGS Of 3418 Veterans contacted, 1063 (31.10%) responded (87.11% male; 85.61% non-Hispanic White; median age = 70, interquartile range [IQR] = 61-74). Prevalence of most reported social risks did not significantly differ by look-back period. Most social risks were weakly intercorrelated (median |r| = 0.24, IQR = 0.16-0.31). Except for legal issues, all social risks were associated with higher odds of fair/poor overall health and mental health in bivariate models. In models containing all significant social risks from bivariate models, adult caregiving and stress remained significant predictors of overall health; food insecurity, housing, loneliness/isolation, and stress remained significant for mental health. CONCLUSIONS Six- and 12-month look-back periods yielded similar rates of reported social risks. Although most individual social risks are associated with fair/poor overall and mental health, when examined together, only adult caregiving, stress, loneliness/isolation, food, and housing remain significant.
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Buchholz C, Sneddon MS, McPherson JE, Das S, Gee CT, Grillo MJ, Chai SC, Lee RE, Chen T, Harki DA, Shelat AA, Pomerantz WCK. Fragment-Based NMR Screening of the BPTF PHD Finger Methyl Lysine Reader Leads to the First Small-Molecule Inhibitors. ACS Med Chem Lett 2023; 14:1441-1447. [PMID: 37849548 PMCID: PMC10577693 DOI: 10.1021/acsmedchemlett.3c00343] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2023] [Accepted: 09/27/2023] [Indexed: 10/19/2023] Open
Abstract
Methyl lysine readers, specifically PHD fingers, are emerging epigenetic targets in human diseases. For example, several PHD finger fusions are implicated in clinical cases of acute myeloid leukemia, highlighting the potential for PHD inhibitors in disease regulation. However, limited chemical matter targeting PHD fingers exists. Here we report the first fragment-based screen against the BPTF PHD to identify several of the first reported BPTF PHD-targeting small-molecule ligands. We used ligand-observed NMR to first screen a fragment library, followed by biophysical validation to prioritize two scaffolds, pyrrolidine- and pyridazine-containing fragments. Structural predictions show that these respective scaffolds may engage two distinct subpockets on the protein. The demonstrated ligandability of the BPTF PHD supports the future development of methyl lysine reader chemical probes to study their oncogenic functions.
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Benoit JB, Finch G, Ankrum AL, Niemantsverdriet J, Paul B, Kelley M, Gantz JD, Matter SF, Lee RE, Denlinger DL. Reduced male fertility of an Antarctic mite following extreme heat stress could prompt localized population declines. Cell Stress Chaperones 2023; 28:541-549. [PMID: 37392307 PMCID: PMC10468472 DOI: 10.1007/s12192-023-01359-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2023] [Revised: 06/05/2023] [Accepted: 06/06/2023] [Indexed: 07/03/2023] Open
Abstract
Climate change is leading to substantial global thermal changes, which are particularly pronounced in polar regions. Therefore, it is important to examine the impact of heat stress on the reproduction of polar terrestrial arthropods, specifically, how brief extreme events may alter survival. We observed that sublethal heat stress reduces male fecundity in an Antarctic mite, yielding females that produced fewer viable eggs. Females and males collected from microhabitats with high temperatures showed a similar reduction in fertility. This impact is temporary, as indicated by recovery of male fecundity following return to cooler, stable conditions. The diminished fecundity is likely due to a drastic reduction in the expression of male-associated factors that occur in tandem with a substantial increase in the expression of heat shock proteins. Cross-mating between mites from different sites confirmed that heat-exposed populations have impaired male fertility. However, the negative impacts are transient as the effect on fertility declines with recovery time under less stressful conditions. Modeling indicated that heat stress is likely to reduce population growth and that short bouts of non-lethal heat stress could have substantial reproductive effects on local populations of Antarctic arthropods.
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Parmar KR, Lukka PB, Wagh S, Temrikar ZH, Liu J, Lee RE, Braunstein M, Hickey AJ, Robertson GT, Gonzalez-Juarrero M, Edginton A, Meibohm B. Development of a Minimalistic Physiologically Based Pharmacokinetic (mPBPK) Model for the Preclinical Development of Spectinamide Antibiotics. Pharmaceutics 2023; 15:1759. [PMID: 37376207 DOI: 10.3390/pharmaceutics15061759] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2023] [Revised: 06/11/2023] [Accepted: 06/12/2023] [Indexed: 06/29/2023] Open
Abstract
Spectinamides 1599 and 1810 are lead spectinamide compounds currently under preclinical development to treat multidrug-resistant (MDR) and extensively drug-resistant (XDR) tuberculosis. These compounds have previously been tested at various combinations of dose level, dosing frequency, and route of administration in mouse models of Mycobacterium tuberculosis (Mtb) infection and in healthy animals. Physiologically based pharmacokinetic (PBPK) modeling allows the prediction of the pharmacokinetics of candidate drugs in organs/tissues of interest and extrapolation of their disposition across different species. Here, we have built, qualified, and refined a minimalistic PBPK model that can describe and predict the pharmacokinetics of spectinamides in various tissues, especially those relevant to Mtb infection. The model was expanded and qualified for multiple dose levels, dosing regimens, routes of administration, and various species. The model predictions in mice (healthy and infected) and rats were in reasonable agreement with experimental data, and all predicted AUCs in plasma and tissues met the two-fold acceptance criteria relative to observations. To further explore the distribution of spectinamide 1599 within granuloma substructures as encountered in tuberculosis, we utilized the Simcyp granuloma model combined with model predictions in our PBPK model. Simulation results suggest substantial exposure in all lesion substructures, with particularly high exposure in the rim area and macrophages. The developed model may be leveraged as an effective tool in identifying optimal dose levels and dosing regimens of spectinamides for further preclinical and clinical development.
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18
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Temrikar ZH, Kodidela S, Kumar S, Liu J, Robertson GT, Lee RE, Hickey AJ, Gonzalez-Juarrero M, Meibohm B. Characterization of spectinamide 1599 efficacy against different mycobacterial phenotypes. Tuberculosis (Edinb) 2023; 140:102342. [PMID: 37120915 PMCID: PMC10247484 DOI: 10.1016/j.tube.2023.102342] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2023] [Revised: 03/31/2023] [Accepted: 04/09/2023] [Indexed: 05/02/2023]
Abstract
Spectinamides are a novel series of spectinomycin analogs being developed for the treatment of tuberculosis. The preclinical lead spectinamide 1599 is an antituberculosis drug that possesses robust in vivo efficacy, good pharmacokinetic properties, and excellent safety profiles in rodents. In individuals infected with Mycobacterium tuberculosis or Mycobacterium bovis, causative agents of tuberculosis, the host immune system is capable of restraining these mycobacteria within granulomatous lesions. The harsh microenvironmental conditions of these granuloma lead to phenotypic transformation of mycobacteria. Phenotypically transformed bacteria display suboptimal growth, or complete growth arrest and are frequently associated with drug tolerance. Here we quantified the effect of spectinamide 1599 on log-phase and phenotypically tolerant isoforms of Mycobacterium bovis BCG using various in vitro approaches as a first indicator of spectinamide 1599 activity against various mycobacterial isoforms. We also used the hollow fiber infection model to establish time-kill curves and deployed pharmacokinetic/pharmacodynamic modeling to characterize the activity differences of spectinamide 1599 towards the different phenotypic subpopulations. Our results indicate that spectinamide 1599 is more efficacious against log phase bacteria when compared to its activity against other phenotypically tolerant forms such as acid phase bacteria and hypoxic phase bacteria, a behavior similar to the established antituberculosis drug isoniazid.
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19
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Scott DC, King MT, Baek K, Gee CT, Kalathur R, Li J, Purser N, Nourse A, Chai SC, Vaithiyalingam S, Chen T, Lee RE, Elledge SJ, Kleiger G, Schulman BA. E3 ligase autoinhibition by C-degron mimicry maintains C-degron substrate fidelity. Mol Cell 2023; 83:770-786.e9. [PMID: 36805027 PMCID: PMC10080726 DOI: 10.1016/j.molcel.2023.01.019] [Citation(s) in RCA: 19] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2022] [Revised: 12/19/2022] [Accepted: 01/18/2023] [Indexed: 02/18/2023]
Abstract
E3 ligase recruitment of proteins containing terminal destabilizing motifs (degrons) is emerging as a major form of regulation. How those E3s discriminate bona fide substrates from other proteins with terminal degron-like sequences remains unclear. Here, we report that human KLHDC2, a CRL2 substrate receptor targeting C-terminal Gly-Gly degrons, is regulated through interconversion between two assemblies. In the self-inactivated homotetramer, KLHDC2's C-terminal Gly-Ser motif mimics a degron and engages the substrate-binding domain of another protomer. True substrates capture the monomeric CRL2KLHDC2, driving E3 activation by neddylation and subsequent substrate ubiquitylation. Non-substrates such as NEDD8 bind KLHDC2 with high affinity, but its slow on rate prevents productive association with CRL2KLHDC2. Without substrate, neddylated CRL2KLHDC2 assemblies are deactivated via distinct mechanisms: the monomer by deneddylation and the tetramer by auto-ubiquitylation. Thus, substrate specificity is amplified by KLHDC2 self-assembly acting like a molecular timer, where only bona fide substrates may bind before E3 ligase inactivation.
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Rogers PD, Lee RE. Editorial overview: Recent advances in antimicrobial drug discovery and resistance. Curr Opin Microbiol 2023; 71:102242. [PMID: 36423503 PMCID: PMC10364994 DOI: 10.1016/j.mib.2022.102242] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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21
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Subramanian C, Frank MW, Tangallapally R, Yun MK, White SW, Lee RE, Rock CO, Jackowski S. Relief of CoA sequestration and restoration of mitochondrial function in a mouse model of propionic acidemia. J Inherit Metab Dis 2023; 46:28-42. [PMID: 36251252 PMCID: PMC10092110 DOI: 10.1002/jimd.12570] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/17/2022] [Revised: 10/06/2022] [Accepted: 10/10/2022] [Indexed: 01/19/2023]
Abstract
Propionic acidemia (PA, OMIM 606054) is a devastating inborn error of metabolism arising from mutations that reduce the activity of the mitochondrial enzyme propionyl-CoA carboxylase (PCC). The defects in PCC reduce the concentrations of nonesterified coenzyme A (CoASH), thus compromising mitochondrial function and disrupting intermediary metabolism. Here, we use a hypomorphic PA mouse model to test the effectiveness of BBP-671 in correcting the metabolic imbalances in PA. BBP-671 is a high-affinity allosteric pantothenate kinase activator that counteracts feedback inhibition of the enzyme to increase the intracellular concentration of CoA. Liver CoASH and acetyl-CoA are depressed in PA mice and BBP-671 treatment normalizes the cellular concentrations of these two key cofactors. Hepatic propionyl-CoA is also reduced by BBP-671 leading to an improved intracellular C3:C2-CoA ratio. Elevated plasma C3:C2-carnitine ratio and methylcitrate, hallmark biomarkers of PA, are significantly reduced by BBP-671. The large elevations of malate and α-ketoglutarate in the urine of PA mice are biomarkers for compromised tricarboxylic acid cycle activity and BBP-671 therapy reduces the amounts of both metabolites. Furthermore, the low survival of PA mice is restored to normal by BBP-671. These data show that BBP-671 relieves CoA sequestration, improves mitochondrial function, reduces plasma PA biomarkers, and extends the lifespan of PA mice, providing the preclinical foundation for the therapeutic potential of BBP-671.
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Hurst-Hess KR, Phelps GA, Wilt LA, Lee RE, Ghosh P. Mab2780c, a TetV-like efflux pump, confers high-level spectinomycin resistance in mycobacterium abscessus. Tuberculosis (Edinb) 2023; 138:102295. [PMID: 36584486 PMCID: PMC10228334 DOI: 10.1016/j.tube.2022.102295] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2022] [Revised: 12/08/2022] [Accepted: 12/15/2022] [Indexed: 12/24/2022]
Abstract
Mycobacterium abscessus is highly resistant to spectinomycin (SPC) thereby making it unavailable for therapeutic use. Sublethal exposure to SPC strongly induces whiB7 and its regulon, and a ΔMab_whiB7 strain is SPC sensitive suggesting that the determinants of SPC resistance are included within its regulon. In the present study we have determined the transcriptomic changes that occur in M. abscessus upon SPC exposure and have evaluated the involvement of 11 genes, that are both strongly SPC induced and whiB7 dependent, in SPC resistance. Of these we show that MAB_2780c can complement SPC sensitivity of ΔMab_whiB7 and that a ΔMab_2780c strain is ∼150 fold more SPC sensitive than wildtype bacteria, but not to tetracycline (TET) or other aminoglycosides. This is in contrast to its homologues, TetV from M. smegmatis and Tap from M. tuberculosis, that confer low-level resistance to TET, SPC and other aminoglycosides. We also show that the addition of the efflux pump inhibitor (EPI), verapamil results in >100-fold decrease in MIC of SPC in bacteria expressing Mab2780c to the levels observed for ΔMab_2780c; moreover a deletion of MAB_2780c results in a decreased efflux of the drug into the cell supernatant. Together our data suggest that Mab2780c is an SPC antiporter. Finally, molecular docking of SPC and TET on models of TetVMs and Mab2780c confirmed our antibacterial susceptibility findings that the Mab2780c pump preferentially effluxes SPC over TET. To our knowledge, this is the first report of an efflux pump that confers high-level drug resistance in M. abscessus. The identification of Mab2780c in SPC resistance opens up prospects for repurposing this relatively well-tolerated antibiotic as a combination therapy with verapamil or its analogs against M. abscessus infections.
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Singh V, Grzegorzewicz AE, Fienberg S, Müller R, Khonde LP, Sanz O, Alfonso S, Urones B, Drewes G, Bantscheff M, Ghidelli-Disse S, Ioerger TR, Angala B, Liu J, Lee RE, Sacchettini JC, Krieger IV, Jackson M, Chibale K, Ghorpade SR. 1,3-Diarylpyrazolyl-acylsulfonamides Target HadAB/BC Complex in Mycobacterium tuberculosis. ACS Infect Dis 2022; 8:2315-2326. [PMID: 36325756 PMCID: PMC9673142 DOI: 10.1021/acsinfecdis.2c00392] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2022] [Indexed: 11/05/2022]
Abstract
Alternative mode-of-inhibition of clinically validated targets is an effective strategy for circumventing existing clinical drug resistance. Herein, we report 1,3-diarylpyrazolyl-acylsulfonamides as potent inhibitors of HadAB/BC, a 3-hydroxyl-ACP dehydratase complex required to iteratively elongate the meromycolate chain of mycolic acids in Mycobacterium tuberculosis (Mtb). Mutations in compound 1-resistant Mtb mutants mapped to HadC (Rv0637; K157R), while chemoproteomics confirmed the compound's binding to HadA (Rv0635), HadB (Rv0636), and HadC. The compounds effectively inhibited the HadAB and HadBC enzyme activities and affected mycolic acid biosynthesis in Mtb, in a concentration-dependent manner. Unlike known 3-hydroxyl-ACP dehydratase complex inhibitors of clinical significance, isoxyl and thioacetazone, 1,3-diarylpyrazolyl-acylsulfonamides did not require activation by EthA and thus are not liable to EthA-mediated resistance. Further, the crystal structure of a key compound in a complex with Mtb HadAB revealed unique binding interactions within the active site of HadAB, providing a useful tool for further structure-based optimization of the series.
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Divakaran A, Scholtz CR, Zahid H, Lin W, Griffith EC, Lee RE, Chen T, Harki DA, Pomerantz WCK. Development of an N-Terminal BRD4 Bromodomain-Targeted Degrader. ACS Med Chem Lett 2022; 13:1621-1627. [PMID: 36262390 PMCID: PMC9575167 DOI: 10.1021/acsmedchemlett.2c00300] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2022] [Accepted: 09/23/2022] [Indexed: 11/29/2022] Open
Abstract
Targeted protein degradation is a powerful induced-proximity tool to control cellular protein concentrations using small molecules. However, the design of selective degraders remains empirical. Among bromodomain and extra-terminal (BET) family proteins, BRD4 is the primary therapeutic target over family members BRD2/3/T. Existing strategies for selective BRD4 degradation use pan-BET inhibitors optimized for BRD4:E3 ubiquitin ligase (E3) ternary complex formation, but these result in residual inhibition of undegraded BET-bromodomains by the pan-BET ligand, obscuring BRD4-degradation phenotypes. Using our selective inhibitor of the first BRD4 bromodomain, iBRD4-BD1 (IC50 = 12 nM, 23- to 6200-fold intra-BET selectivity), we developed dBRD4-BD1 to selectively degrade BRD4 (DC50 = 280 nM). Notably, dBRD4-BD1 upregulates BRD2/3, a result not observed with degraders using pan-BET ligands. Designing BRD4 selectivity up front enables analysis of BRD4 biology without wider BET-inhibition and simplifies designing BRD4-selective heterobifunctional molecules, such as degraders with new E3 recruiting ligands or for additional probes beyond degraders.
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Sekar G, Singh G, Qin X, Guibao CD, Schwam B, Inde Z, Grace CR, Zhang W, Slavish PJ, Lin W, Chen T, Lee RE, Rankovic Z, Sarosiek K, Moldoveanu T. Small molecule SJ572946 activates BAK to initiate apoptosis. iScience 2022; 25:105064. [PMID: 36147946 PMCID: PMC9485059 DOI: 10.1016/j.isci.2022.105064] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2022] [Revised: 06/29/2022] [Accepted: 08/30/2022] [Indexed: 01/11/2023] Open
Abstract
Poration of the outer mitochondrial membrane by the effector BCL-2 proteins BAK and BAX initiates apoptosis. BH3-only initiators BID and BIM trigger conformational changes in BAK and BAX transforming them from globular dormant proteins to oligomers of the apoptotic pores. Small molecules that can directly activate effectors are being sought for applications in cancer treatment. Here, we describe the small molecule SJ572946, discovered in a fragment-based screen that binds to the activation groove of BAK and selectively triggers BAK activation over that of BAX in liposome and mitochondrial permeabilization assays. SJ572946 independently kills BAK-expressing BCL2allKO HCT116 cells revealing on target cellular activity. In combination with apoptotic inducers and BH3 mimetics, SJ572946 kills experimental cancer cell lines. SJ572946 also cooperates with the endogenous BAK activator BID in activating a misfolded BAK mutant substantially impaired in activation. SJ572946 is a proof-of-concept tool for probing BAK-mediated apoptosis in preclinical cancer research.
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