Novel drug candidates against antibiotic-resistant microorganisms: A review

Document Type : Review Article


1 School of Pharmacy, Faculty of Health and Medical Sciences, Taylor’s University, Subang Jaya, Malaysia

2 Medical Advancement for Better Quality of Life Impact Lab, Taylor’s University, 47500 Selangor, Malaysia

3 Department of Pharmaceutical Life Sciences, Faculty of Pharmacy, Universiti Malaya, Kuala Lumpur, Malaysia


Antibiotic resistance is fast spreading globally, leading to treatment failures and adverse clinical outcomes. This review focuses on the resistance mechanisms of the top five threatening pathogens identified by the World Health Organization’s global priority pathogens list: carbapenem-resistant Acinetobacter baumannii, carbapenem-resistant Pseudomonas aeruginosa, carbapenem-resistant, extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae, vancomycin-resistant Enterococcus faecium and methicillin, vancomycin-resistant Staphylococcus aureus. Several novel drug candidates have shown promising results from in vitro and in vivo studies, as well as clinical trials. The novel drugs against carbapenem-resistant bacteria include LCB10-0200, apramycin, and eravacycline, while for Enterobacteriaceae, the drug candidates are LysSAP-26, DDS-04, SPR-206, nitroxoline, cefiderocol, and plazomicin. TNP-209, KBP-7072, and CRS3123 are agents against E. faecium, while Debio 1450, gepotidacin, delafloxacin, and dalbavancin are drugs against antibiotic-resistant S. aureus. In addition to these identified drug candidates, continued in vitro and in vivo studies are required to investigate small molecules with potential antibacterial effects screened by computational receptor docking. As drug discovery progresses, preclinical and clinical studies should also be extensively conducted on the currently available therapeutic agents to unravel their potential antibacterial effect and spectrum of activity, as well as safety and efficacy profiles.


Main Subjects

1. Teoh L, Stewart K, Marino R, and McCullough M. Antibiotic resistance and relevance to general dental practice in Australia. Aust Dent J 2018; 63:414-421. 
2. Plackett B. Why big pharma has abandoned antibiotics. Nature 2020; 586:S50–S50. 
3. C Reygaert W. An overview of the antimicrobial resistance mechanisms of bacteria. AIMS Microbiol 2018; 4:482-501. 
4. Elshamy AA, Aboshanab KM. A review on bacterial resistance to carbapenems: epidemiology, detection and treatment options. Futur Sci OA 2020;6:FSO438-452. 
5. Centre WM. WHO publishes list of bacteria for which new antibiotics are urgently needed. World Health Organization. 2017; [cited 2023 Mar 12]. Available from: URL:
6. Exner M, Bhattacharya S, Christiansen B, Gebel J, Goroncy-Bermes P, Hartemann P, et al. Antibiotic resistance: What is so special about multidrug-resistant Gram-negative bacteria? GMS Hyg Infect Control 2017; 12:1-24. 
7. Ongenae V, Briegel A, Claessen D. Cell wall deficiency as an escape mechanism from phage infection. Open Biol 2021;11:210199-210205. 
8. Santajit S, Indrawattana N. Mechanisms of antimicrobial resistance in ESKAPE pathogens. Biomed Res Int 2016;2016:2475067-2475074. 
9. Bush K, Jacoby GA. Updated functional classification of beta-lactamases. Antimicrob Agents Chemother 2010; 54:969-976. 
10. Breijyeh Z, Jubeh B, Karaman R. Resistance of Gram-negative bacteria to current antibacterial agents and approaches to resolve it. Molecules 2020; 25:1340-1362. 
11. Lee CR, Lee JH, Park M, Park KS, Bae IK, Kim YB, et al. Biology of Acinetobacter baumannii: Pathogenesis, antibiotic resistance mechanisms, and prospective treatment options. Front Cell Infect Microbiol 2017; 7:55-89. 
12. Pang Z, Raudonis R, Glick BR, Lin TJ, Cheng Z. Antibiotic resistance in Pseudomonas aeruginosa: Mechanisms and alternative therapeutic strategies. Biotechnol Adv 2019; 37:177-192. 
13. Hsu LY, Apisarnthanarak A, Khan E, Suwantarat N, Ghafur A, Tambyah PA. Carbapenem-resistant Acinetobacter baumannii and Enterobacteriaceae in south and southeast asia. Clin Microbiol Rev 2017; 30:1-22. 
14. Naas T, Dortet L, I. Iorga B. Structural and functional aspects of class a carbapenemases. Curr Drug Targets 2016; 17:1006-1028. 
15. Blanco P, Hernando-Amado S, Reales-Calderon JA, Corona F, Lira F, Alcalde-Rico M, et al. Bacterial multidrug efflux pumps: Much more than antibiotic resistance determinants. Microorganisms 2016; 4:14-33. 
16. Li-Jing Zhu, Yan Pan, Chun-Yan Gao P-FH. Distribution of carbapenemases and efflux pump in carbapenem-resistance Acinetobacter baumannii-pubmed. Ann Clin Lab Sci 2020; 50:241-246. 
17. Wong MH yin, Chan BK wai, Chan EW chi, Chen S. Over-expression of ISAba1-linked intrinsic and exogenously acquired OXA type carbapenem-hydrolyzing-class D-ß-lactamase-encoding genes is key mechanism underlying carbapenem resistance in Acinetobacter baumannii. Front Microbiol 2019; 10:2809-2817. 
18. Yoon EJ and Jeong SH. Mobile carbapenemase genes in Pseudomonas aeruginosa. Front Microbiol 2021; 12:30-50. 
19. Meletis G, Exindari M, Vavatsi N, Sofianou D, Diza E. Mechanisms responsible for the emergence of carbapenem resistance in Pseudomonas aeruginosa. Hippokratia 2012; 16:303-307. 
20. Kang AD, Smith KP, Eliopoulos GM, Berg AH, McCoy C, Kirby JE. In vitro apramycin activity against multidrug-resistant Acinetobacter baumannii and Pseudomonas aeruginosa. Diagn Microbiol Infect Dis 2017; 88:188-191. 
21. Becker K, Aranzana-Climent V, Cao S, Nilsson A, Shariatgorji R, Haldimann K, et al. Efficacy of EBL-1003 (apramycin) against Acinetobacter baumannii lung infections in mice. Clin Microbiol Infect 2021; 27:1315-1321. 
22. Seifert H, Stefanik D, Sutcliffe JA, Higgins PG. In vitro activity of the novel fluorocycline eravacycline against carbapenem non-susceptible Acinetobacter baumannii. Int J Antimicrob Agents 2018; 51:62-64. 
23. Solomkin J, Evans D, Slepavicius A, Lee P, Marsh A, Tsai L, et al. Assessing the efficacy and safety of eravacycline vs ertapenem in complicated intra-abdominal infections in the investigating Gram-negative infections treated with eravacycline (ignite 1) trial: A randomized clinical trial. JAMA Surg 2017; 152:224-232. 
24. Solomkin JS, Gardovskis J, Lawrence K, Montravers P, Sway A, Evans D, et al. IGNITE4: Results of a phase 3, randomized, multicenter, prospective trial of eravacycline vs meropenem in the treatment of complicated intraabdominal infections. Clin Infect Dis 2019; 69:921-929. 
25. Nguyen LP, Park CS, Pinto NA, Lee H, Seo HS, Vu TN, et al. In vitro activity of a novel siderophore-cephalosporin LCB10-0200 (GT-1), and LCB10-0200/avibactam, against carbapenem-resistant Escherichia coli, Llebsiella pneumoniae, Acinetobacter baumannii, and pseudomonas aeruginosa strains at a tertiary hospital in Korea. Pharmaceuticals 2021; 14:370-384. 
26. Nguyen M and Joshi SG. Carbapenem resistance in Acinetobacter baumannii, and their importance in hospital-acquired infections: A scientific review. J Appl Microbiol 2021; 131:2715-2738. 
27. Oh SH, Park HS, Kim HS, Yun JY, Oh K, Cho YL, et al. Antimicrobial activities of LCB10-0200, a novel siderophore cephalosporin, against the clinical isolates of Pseudomonas aeruginosa and other pathogens. Int J Antimicrob Agents 2017; 50:700-706. 
28. Mmatli M, Mbelle NM, Maningi NE, Sekyere JO. Emerging transcriptional and genomic mechanisms mediating carbapenem and polymyxin resistance in Enterobacteriaceae: A systematic review of current reports. mSystems 2020;5:e00783-20. 
29. Kim S, Jin JS, Choi YJ, Kim J. LysSAP26, a new recombinant phage endolysin with a broad spectrum antibacterial activity. Viruses 2020; 12:1340-1348. 
30. Breidenstein E. Novel small-molecule inhibitors of bacterial lipoprotein transport against Enterobacteriaceae. 2019. 
31. Zhang Y, Zhao C, Wang Q, Wang X, Chen H, Li H, et al. Evaluation of the in vitro activity of new polymyxin B analogue SPR206 against clinical MDR, colistin-resistant and tigecycline-resistant Gram-negative bacilli. J Antimicrob Chemother 2020; 75:2609-2615. 
32. Brown P, Abbott E, Abdulle O, Boakes S, Coleman S, Divall N, et al. Design of next generation polymyxins with lower toxicity: The discovery of SPR206. ACS Infect Dis 2019; 5:1645-1656. 
33. Grosser L, Heang K, Teague J, Warn P, Corbett D, Dawson MJ RA. In vivo efficacy of SPR206 in murine lung and thigh infection models caused by multidrug resistant pathogens Pseudomonas aeruginosa and Acinetobacter baumannii. ECCMID 2018. 
34. Phase 1 Study of PK and Safety of SPR206 in Subjects With Various Degrees Of Renal Function - Full Text View - [cited 2023 Mar 14]. Available from: URL:
35. Study to Assess the Intrapulmonary Pharmacokinetics of SPR206 in Healthy Volunteers - Full Text View - [cited 2023 Mar 14]. Available from: URL:
36. Sobke A, Makarewicz O, Baier M, Bär C, Pfister W, Gatermann SG, et al. Empirical treatment of lower urinary tract infections in the face of spreading multidrug resistance: In vitro study on the effectiveness of nitroxoline. Int J Antimicrob Agents 2018; 51:213-220. 
37. Fuchs F, Becerra-Aparicio F, Xanthopoulou K, Seifert H, Higgins PG. In vitro activity of nitroxoline against carbapenem-resistant Acinetobacter baumannii isolated from the urinary tract. J Antimicrob Chemother 2022; 77:1912-1915. 
38. Hackel MA, Tsuji M, Yamano Y, Echols R, Karlowsky JA, Sahm DF. In vitro activity of the siderophore cephalosporin, cefiderocol, against carbapenem-nonsusceptible and multidrug-resistant isolates of Gram-negative bacilli collected worldwide in 2014 to 2016. Antimicrob Agents Chemother 2018;62:e01968-17. 
39. A Study of Efficacy and Safety of Intravenous Cefiderocol (S-649266) Versus Imipenem/Cilastatin in Complicated Urinary Tract Infections - Full Text View - [cited 2023 Mar 29]. Available from: URL:
40. Study of Cefiderocol (S-649266) or Best Available Therapy for the Treatment of Severe Infections Caused by Carbapenem-resistant Gram-negative Pathogens - Full Text View - [cited 2023 Mar 29]. Available from: URL:
41. Plazomicin. National Center for Biotechnology Information. 2022; [cited 2023 Mar 12]. Available from: URL:
42. Connolly LE, Riddle V, Cebrik D, Armstrong ES, Miller LG. A multicenter, randomized, double-blind, phase 2 study of the efficacy and safety of plazomicin compared with levofloxacin in the treatment of complicated urinary tract infection and acute pyelonephritis. Antimicrob Agents Chemother 2018; 62. 
43. NCT01096849. Study of plazomicin (ACHN-490) compared with levofloxacin for the treatment of complicated urinary tract infection and acute pyelonephritis. 2010. 
44. Achaogen I. A Study of Plazomicin Compared With Colistin in Patients With Infection Due to Carbapenem-Resistant Enterobacteriaceae (CRE)(CARE). 2016; [cited 2023 Mar 15]:1-6. Available from: URL:
45. Therapeutics S. A First in Human Study of the Safety and Tolerability of Single and Multiple Doses of SPR206 in Healthy Volunteers. 2020; [cited 2023 Mar 14]. Available from: URL:
46. Zhou X, Willems RJL, Friedrich AW, Rossen JWA, Bathoorn E. Enterococcus faecium: From microbiological insights to practical recommendations for infection control and diagnostics. Antimicrob Resist Infect Control 2020; 9:1-13. 
47. Rivera AM, Boucher HW. Current concepts in antimicrobial therapy against select gram-positive organisms: Methicillin-resistant Staphylococcus aureus, penicillin-resistant pneumococci, and vancomycin-resistant enterococci. Mayo Clin Proc 2011; 86:1230-1243. 
48. O’Driscoll T, Crank CW. Vancomycin-resistant enterococcal infections: epidemiology, clinical manifestations, and optimal management. Infect Drug Resist 2015; 8:217-230. 
49. Zerrouki H, Rebiahi SA, Hadjadj L, Ahlem F, Elhabiri Y, Sedrati T, et al. High frequency and diversity of Vancomycin-resistant Enterococci (VRE) in algerian healthcare settings. Infect Genet Evol 2021;92:104889. 
50. Hollenbeck BL, Rice LB. Intrinsic and acquired resistance mechanisms in enterococcus. Virulence 2012; 3:421-569. 
51. Smith TT, Tamma PD, Do TB, Dzintars KE, Zhao Y, Cosgrove SE, et al. Prolonged linezolid use is associated with the development of linezolid-resistant Enterococcus faecium. Diagn Microbiol Infect Dis 2018; 91:161-163. 
52. Klare I, Fleige C, Geringer U, Thürmer A, Bender J, Mutters NT, et al. Increased frequency of linezolid resistance among clinical Enterococcus faecium isolates from German hospital patients. J Glob Antimicrob Resist 2015; 3:128-131. 
53. Chen H, Wu W, Ni M, Liu Y, Zhang J, Xia F, et al. Linezolid-resistant clinical isolates of enterococci and Staphylococcus cohnii from a multicentre study in China: Molecular epidemiology and resistance mechanisms. Int J Antimicrob Agents 2013; 42:317-321. 
54. Olearo F, Both A, Belmar Campos C, Hilgarth H, Klupp EM, Hansen JL, et al. Emergence of linezolid-resistance in vancomycin-resistant Enterococcus faecium ST117 associated with increased linezolid-consumption. Int J Med Microbiol 2021;311:151477. 
55. Ma Z, Lynch AS. Development of a dual-acting antibacterial agent (TNP-2092) for the treatment of persistent bacterial infections. J Med Chem 2016; 59:6645-6657. 
56. Yuan Y, Wang X, Xu X, Liu Y, Li C, Yang M, et al. Evaluation of a dual-acting antibacterial agent, TNP-2092, on gut microbiota and potential application in the treatment of gastrointestinal and liver disorders. ACS Infect Dis 2020;6:820-831. 
57. TNP-2092 to Treat Acute Bacterial Skin and Skin Structure Infection-Full Text [cited 2023 Mar 15]. Available from: URL:
58. Kaminishi T, Schedlbauer A, Ochoa-Lizarralde B, Astigarraga E de, Çapuni R, Yang F, et al. The third-generation tetracycline KBP-7072 exploits and reveals a new potential of the primary tetracycline binding pocket. bioRxiv 2018; 1-14. 
59. Huband MD, Mendes RE, Pfaller MA, Lindley JM, Strand GJ, Benn VJ, et al. In vitro activity of KBP-7072, a novel third-generation tetracycline, against 531 recent geographically diverse and molecularly characterized Acinetobacter baumannii species complex isolates. Antimicrob Agents Chemother  2020;64:e02375-19. 
60. Safety, Tolerability and Pharmacokinetics of KBP-7072 - Full Text View - [cited 2023 Mar 15]. Available from: URL:
61. A Multiple Ascending Dose Study to Investigate Safety of KBP-7072 in Healthy Subjects. [cited 2023 Mar 15]. Available from: URL:
62. Zhang B, Wang Y, Chen Y, and Yang F. Single ascending dose safety, tolerability, and pharmacokinetics of KBP-7072, a novel third generation tetracycline. Open Forum Infect Dis 2016; 3:S515. 
63. Online D. CRS-3123. DrugBank Online. 2021; [cited 2023 Mar 15]. Available from: URL:
64. Lomeli BK, Galbraith H, Schettler J, Saviolakis GA, El-Amin W, Osborn B, et al. Multiple-ascending-dose phase 1 clinical study of the safety, tolerability, and pharmacokinetics of CRS3123, a narrow-spectrum agent with minimal disruption of normal gut microbiota. Antimicrob Agents Chemother 2019;64:e01395-19. 
65. Critchley IA, Green LS, Young CL, Bullard JM, Evans RJ, Price M, et al. Spectrum of activity and mode of action of REP3123, a new antibiotic to treat Clostridium difficile infections. J Antimicrob Chemother 2009; 63:954-963. 
66. Ochsner UA, Bell SJ, O’Leary AL, Hoang T, Stone KC, Young CL, et al. Inhibitory effect of REP3123 on toxin and spore formation in Clostridium difficile, and in vivo efficacy in a hamster gastrointestinal infection model. J Antimicrob Chemother 2009; 63:964-971. 
67. National Institute of Allergy and Infectious Diseases (NIAID). Phase I Trial of a Single Dose of CRS3123. 2017; [cited 2023 Mar 15]. Available from: URL:
68. Nayak SU, Griffiss JML, Blumer J, O’Riordan MA, Gray W, McKenzie R, et al. Safety, tolerability, systemic exposure, and metabolism of CRS3123, a methionyl-tRNA synthetase inhibitor developed for treatment of clostridium difficile, in a phase 1 study. Antimicrob Agents Chemother 2017;61:e02760-27616. 
69. A Multiple Ascending Dose Study of KBP-7072 in Healthy Subjects - Full Text View - [cited 2023 Mar 15]. Available from: URL:
70. Guo Y, Song G, Sun M, Wang J, Wang Y. Prevalence and therapies of antibiotic-resistance in Staphylococcus aureus. Front Cell Infect Microbiol 2020; 10:107-117. 
71. Keseru JS, Gál Z, Barabás G, Benko I, and Szabó I. Investigation of beta-Lactamases in clinical isolates of Staphylococcus aureus for further explanation of borderline methicillin resistance. Chemotherapy 2005; 51:300-304. 
72. Foster TJ. Can β-lactam antibiotics be resurrected to combat MRSA? Trends Microbiol 2019; 27:26-38. 
73. Gao Y, Chen Y, Cao Y, Mo A, Peng Q. Potentials of nanotechnology in treatment of methicillin-resistant Staphylococcus aureus. Eur J Med Chem 2021;213:113056. 
74. Cong Y, Yang S, and Rao X. Vancomycin resistant Staphylococcus aureus infections: A review of case updating and clinical features. J Adv Res 2019; 21:169-176. 
75. Conly JM and Johnston BL. VISA, hetero-VISA and VRSA: The end of the vancomycin era? Can J Infect Dis 2002;13:282-284. 
76. Sieradzki K, Tomasz A. Gradual alterations in cell wall structure and metabolism in vancomycin-resistant mutants of Staphylococcus aureus. J Bacteriol 1999; 181:7566-7570. 
77. Liu WT, Chen EZ, Yang L, Peng C, Wang Q, Xu Z, et al. Emerging resistance mechanisms for 4 types of common anti-MRSA antibiotics in Staphylococcus aureus: A comprehensive review. Microb Pathog 2021;156:104915. 
78. Sohlenkamp C, Geiger O. Bacterial membrane lipids: Diversity in structures and pathways. FEMS Microbiol Rev 2016; 40:133-159. 
79. Ernst CM, Staubitz P, Mishra NN, Yang SJ, Hornig G, Kalbacher H, et al. The bacterial defensin resistance protein MprF consists of separable domains for lipid lysinylation and antimicrobial peptide repulsion. PLOS Pathog 2009; 5:e1000660-e1000668. 
80. Hawser S, Gueny M, Le Bras Ch, Morrissey I, Valmont Th, Magnet FW S. Activity of debio 1452 against Staphylococcus spp collected in 2013/2014. In: Debiopharm Group. 2016. 
81. Menetrey A, Janin A, Pullman J, Scott Overcash J, Haouala A, Leylavergne F, et al. Bone and joint tissue penetration of the staphylococcus-selective antibiotic afabicin in patients undergoing elective hip replacement surgery. Antimicrob Agents Chemother 2019;63:e01669-18. 
82. Drug Penetration Into Bone After Repeated Oral Administration of Debio 1450 to Patients Undergoing Hip Replacement Surgery - Full Text View - [cited 2023 Mar 14]. Available from: URL:
83. Study of Debio 1450 for Bacterial Skin Infections - Full Text View - [cited 2023 Mar 14]. Available from: URL:
84. Study to Assess Safety, Tolerability and Efficacy of Afabicin in The Treatment of Participants With Bone or Joint Infection Due to Staphylococcus - Full Text View - [cited 2023 Mar 14]. Available from: URL:
85. Biedenbach DJ, Bouchillon SK, Hackel M, Miller LA, Scangarella-Oman NE, Jakielaszek C, et al. In vitro activity of gepotidacin, a novel triazaacenaphthylene bacterial topoisomerase inhibitor, against a broad spectrum of bacterial pathogens. Antimicrob Agents Chemother 2016; 60:1918-1923. 
86. A Study to Evaluate Efficacy and Safety of Gepotidacin in the Treatment of Uncomplicated Urinary Tract Infection (UTI) - Full Text View - [cited 2023 Mar 14]. Available from: URL:
87. A Study Evaluating Efficacy and Safety of Gepotidacin Compared With Ceftriaxone Plus Azithromycin in the Treatment of Uncomplicated Urogenital Gonorrhea - Full Text View - [cited 2023 Mar 14]. Available from: URL:
88. Saravolatz LD and Pawlak J. Delafloxacin activity against Staphylococcus aureus with reduced susceptibility or resistance to methicillin, vancomycin, daptomycin, or linezolid. Open Forum Infect Dis 2019; 6:S579-S580. 
89. Delafloxacin Versus Vancomycin and Aztreonam for the Treatment of Acute Bacterial Skin and Skin Structure Infections - Full Text View - [cited 2023 Mar 14]. Available from: URL:
90. Dalbavancin For The Treatment of Gram Positive Osteoarticular Infections - Full Text View - [cited 2023 Mar 14]. Available from: URL:
91. Turner NA, Zaharoff S, King H, Evans S, Hamasaki T, Lodise T, et al. Dalbavancin as an option for treatment of S. aureus bacteremia (DOTS): Study protocol for a phase 2b, multicenter, randomized, open-label clinical trial. Trials 2022;23:407-421.