microorganisms

Review Promising Drug Candidates and New Strategies for Fighting against the Emerging Superbug Candida auris

Muriel Billamboz 1,2,*, Zeeshan Fatima 3, Saif Hameed 3 and Samir Jawhara 4,*

1 Inserm, CHU Lille, Institut Pasteur Lille, Université Lille, U1167—RID-AGE—Facteurs de Risque et Déterminants Moléculaires des Maladies liées au Vieillissement, F-59000 Lille, France 2 Junia, Health and Environment, Laboratory of Sustainable Chemistry and Health, F-59000 Lille, France 3 Amity Institute of Biotechnology, Amity University Haryana, Manesar, Gurugram 122413, India; [email protected] (Z.F.); [email protected] (S.H.) 4 UMR 8576-UGSF-Unité de Glycobiologie Structurale et Fonctionnelle, Centre National de la Recherche Scientifique, INSERM U1285, University of Lille, F-59000 Lille, France * Correspondence: [email protected] (M.B.); [email protected] (S.J.)

Abstract: Invasive fungal represent an expanding threat to public health. During the past decade, a paradigm shift of candidiasis from to non-albicans Candida species has fundamentally increased with the advent of Candida auris. C. auris was identified in 2009 and is now recognized as an emerging species of concern and underscores the urgent need for novel drug development strategies. In this review, we discuss the genomic epidemiology and the main virulence factors of C. auris. We also focus on the different new strategies and results obtained during the past decade in the field of design against this emerging C. auris pathogen yeast, based on a medicinal chemist point of view. Critical analyses of chemical features and physicochemical   descriptors will be carried out along with the description of reported strategies.

Citation: Billamboz, M.; Fatima, Z.; Keywords: Candida auris; antifungal drugs; repurposed drugs; combinatorial therapy; natural Hameed, S.; Jawhara, S. Promising compounds; nanoparticles Drug Candidates and New Strategies for Fighting against the Emerging Superbug Candida auris. Microorganisms 2021, 9, 634. https://doi.org/10.3390/ microorganisms9030634 1. Introduction First identified in 2009 from the ear canal of a patient in Japan [1], C. auris is now recog- Academic Editor: Eric Dannaoui nized as an emerging species of concern [2,3], and more and more publications are related to C. auris studies (Figure1). When searching for “ Candida auris” key words on Scifinder, Received: 25 January 2021 fewer than 1000 reports have been compiled, most of them during the two last years, Accepted: 8 March 2021 proving the acceleration of research and clinical studies around this emerging pathogen. Published: 18 March 2021 Its emergence is defined by the occurrence of C. auris infections in a dozen of countries all around the world. In Europe, since 2015, sporadic epidemics have been reported in Publisher’s Note: MDPI stays neutral Spain [4], United-Kingdom [5], Germany, or Norway [6], for example. Simultaneously, with regard to jurisdictional claims in candidiasis caused by C. auris were reported in Korea [7], South Korea [8], India [9–11], published maps and institutional affil- South-Africa [12], or Kowait [13]. In the same period, the United States were also af- iations. fected [14–16]. This human pathogen is associated with severe invasive infections with high mortality rates ranging from 35 to 72% [8,12,17,18]. Since June 2016, governmental in- stitutions (Centers for Disease Control and Prevention (CDC), European Centre for Disease Prevention and Control (ECDC), World Health Organization (WHO), Pan American Health Copyright: © 2021 by the authors. Organization (PAHO), National institute for Communicable Diseases (NICD) ... ) have Licensee MDPI, Basel, Switzerland. issued clinical alerts to health care facilities and provided interim guidelines for clinical This article is an open access article management, laboratory testing and control of C. auris [19,20]. This fungus poses distributed under the terms and significant challenges to microbiologists and clinicians because of its frequent multidrug conditions of the Creative Commons resistance; high transmissibility and severe outcomes coupled with misidentification by Attribution (CC BY) license (https:// standard biochemical identification systems such as Vitek 2 [21]. creativecommons.org/licenses/by/ 4.0/).

Microorganisms 2021, 9, 634. https://doi.org/10.3390/microorganisms9030634 https://www.mdpi.com/journal/microorganisms Microorganisms 2021, 9, 634 2 of 40 Microorganisms 2021, 9, x 2 of 42

350

300

250

200 year 150

100

Number of publications per of publications Number 50

0 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020

FigureFigure 1.1. Evolution of of annual annual reports reports dealing dealing with with C.C. auris auris studiesstudies (Scifinder (Scifinder search, search, keykey word word Candida auris, Data Compiled on 31 December 2020). Candida auris, Data Compiled on 31 December 2020).

Moreover,Moreover, the the widespread widespread and and prolonged prolonged use use of of available available antifungal antifungal drugs drugs has has given given riserise to to multidrug multidrug resistance resistance that that alters alters the therapeuticthe therapeutic available available options. opti Itons. has It been has reported been re- thatported nearly that 90% nearly of C .90%auris ofisolates C. auris exhibit isolates resistance exhibit resistance to fluconazole, to , around 30% around resistance 30% toresistance amphotericin to , and less B, thanand less 5% than resistance 5% resistance to to echinocandins [22,23]. [22,23]. Under Under such compellingsuch compelling circumstances, circumstances,C. auris C. displaysauris displays all the all features the features of a “superbug”of a “superbug” and effortsand ef- areforts ongoing are ongoing to identify to identify newtherapeutic new therapeutic alternatives alternatives to fight to againstfight againstC. auris C. infections.auris infec- Aftertions. introducing After introducingC. auris C.genomic auris genomic epidemiology epidemiology and virulence and viru factors,lence thisfactors, review this aims review at compilingaims at compiling the different the strategiesdifferent strategies and results and obtained results during obtained the pastduring ten the years past in ten the fieldyears ofin antifungal the field of research antifungal against research emerging againstC. emerging auris from C. a medicinalauris from chemista medicinal point chemist of view. point To summarize,of view. To summarize, six complementary six complementary strategies have strate beengies developed, have been developed, from the most from attractive the most toattractive the less reported:to the less (i) reported: repurposing (i) repurposin of drugs;g (ii) of evaluation drugs; (ii) ofevaluation combination of combination drugs; (iii) discoverydrugs; (iii) of discovery new drug-candidates; of new drug-candidates; (iv) traditional (iv) traditional medicines medicines and natural andcompounds; natural com- (v)pounds; metal, (v) metalloids metal, metalloids and complexes; and complexes; (vi) others (vi) approaches others approaches including including nanoparticles nanopar- and irradiation.ticles and irradiation. Results and Results data will and be data analyzed will be from analyzed a chemical from approach a chemical based approach on chemical based featureson chemical and physicochemicalfeatures and physicochemical descriptors suchdescriptors as lipophilicity such as lipophilicity (expressed by(expressed logP) and by topologicallogP) and polartopological surface polar area (TPSA)surface inarea order (TPSA) to establish in order a comparison to establish between a comparison classes be- of compoundstween classes and of definecompounds potential and common define potential pharmacophoric common moieties.pharmacophoric moieties.

2.2.Candida Candida aurisaurisGenomic Genomic Epidemiology Epidemiology and and Virulence Virulence Factors Factors 2.1. Global View 2.1. Global View C. auris is taxonomically placed as a close relative to the Candida haemulonii since its C. auris is taxonomically placed as a close relative to the Candida haemulonii since its discovery in 2009 from the ear canal of a patient in Japan [1]. C. auris was isolated in all discovery in 2009 from the ear canal of a patient in Japan [1]. C. auris was isolated in all continents except Antarctica. Munoz et al. found that four of the five clades of C. auris are continents except Antarctica. Munoz et al. found that four of the five clades of C. auris are genetically related to other Candida species including C. haemulonii, C. duobushaemulonii, genetically related to other Candida species including C. haemulonii, C. duobushaemulonii, and C. psuedohaemulonii [24]. These five genetically distinct clades of C. auris correspond to: Cladeand C. I frompsuedohaemulonii India and Pakistan [24]. These (South five Asian), genetically Clade distinct II from Japanclades (Eastof C. Asian),auris correspond Clade III fromto: Clade South I from Africa India (African), and Pakistan Clade IV (South from VenezuelaAsian), Clade (South II from American) Japan (East and most Asian), recently Clade aIII potential from South Clade Africa V from (African), Iran [22 Clade,25]. OverIV from the Venezuela past ten years, (SouthC. Am auriserican)has been and isolatedmost re- acrosscently all a majorpotential continents, Clade V including from Iran elsewhere [22,25]. Over in Asia, the Africa, past ten North years, and C. South auris America,has been Australia,isolated across Europe, all andmajor the continents, Middle East. including elsewhere in Asia, Africa, North and South America,Outbreaks Australia, in United Europe, States and have the Middle been reported East. to different clades of C. auris that are introducedOutbreaks from in other United continents. States have In terms been ofreported the analysis to different of whole-genome clades of C. auris sequencing that are studies,introduced Chow from et al. other found continents. that the 133 In clinicalterms of isolates the analysis of C. auris of whole-genomeidentified in United-States sequencing betweenstudies, 2013Chow and et al. 2017 found were that related the to133 South clinical Asian, isolates South of American,C. auris identified African, in and United- East AsianStates isolatesbetween but 2013 unexpectedly, and 2017 were only related 7% of to theseSouth clinical Asian, SouthC. auris American,isolates wereAfrican, identi- and fiedEast from Asian patients isolates with but unexpected clear evidencely, only of being 7% of acquired these clinical through C. auris health-care isolates exposureswere iden- abroadtified from [16]. patients Outbreaks with in clear Europe evidence were also of being attributed acquired to recent through spread health-care from other exposures conti- nents.abroad For [16]. example, Outbreaks the firstin Europe case of wereC. auris alsoinfection attributed in Franceto recent has spread been reportedfrom other in conti- 2018 nents. For example, the first case of C. auris infection in France has been reported in 2018

Microorganisms 2021, 9, 634x 3 3of of 42 40

fromfrom a a patient patient who who travelled travelled in in India and Iran two months before his hospitalization in FranceFrance [26]. [26]. C.C. auris auris isis believed believed to to have have been been misidentified misidentified as as C.C. haemulonii onon several occasions, occasions, suggestingsuggesting that that C.C. auris auris hashas likely been circulating as a human fungal pathogen before 2009.2009. However, However, retrospective retrospective analysis of the SENTRY Antifungal Surveillance collection ofof over over 15,000 15,000 CandidaCandida isolatesisolates from from 135 135 participating participating medical medical centers centers in in North North America, America, Europe,Europe, Latin America,America, andand the the Asia-Pacific Asia-Pacific regions regions since since 1997 1997 shows shows no misidentificationsno misidentifica- tionsof C. of auris C. aurisbefore before 2009 [200927]. [27].

2.2.2.2. Virulence Virulence Factors Factors of of C. C. auris auris LikeLike C.C. albicans albicans,, C.C. auris auris expressesexpresses several several virulence virulence fact factorsors that that contribute contribute to to patho- patho- genesisgenesis including including the the transition transition between between blas blastoconidiatoconidia and and filamentous filamentous forms, hydrolytic enzymeenzyme production, production, thermotolerance, /ad biofilm/adhesionhesion to to host host cells, cells, osmotolerance, osmotolerance, fila- fila- mentation,mentation, and and phenotypic phenotypic switching (Figure 22).).

FigureFigure 2. 2. SchematicSchematic overview overview of ofC.C. auris auris virulencevirulence factors. factors. Stress Stress resistance, resistance, hydrolytic hydrolytic enzyme enzyme production,production, thermotolerance, biofilm/adhesionbiofilm/adhesion toto hosthost cells,cells, osmotolerance,osmotolerance, filamentation, filamentation, and and white whiteand opaque and opaque switching switching are important are important virulence virulence traits intraitsC. auris. in C. auris.

InIn contrast contrast to to other other close close relatives relatives including including C.C. haemulonii haemulonii or orC. C.pseudohaemulonii pseudohaemulonii, C., aurisC. auris is ableis able to togrow grow at at42 42 °C◦ C[[1].1 ].The The thermotolerance thermotolerance of of C.C. auris auris contributescontributes to to persist againstagainst the the high high fever fever response response and and causes causes an an invasive invasive candidemia candidemia [28]. [28]. Casadevall Casadevall et et al. al. suggestedsuggested that that the the thermotolerance thermotolerance of ofC. C.auris auris is relatedis related to climate to climate change change and global and global tem- peraturetemperature changes changes supporting supporting the thehypothesis hypothesis that that C. C.auris auris is isthe the first first example example of of a a new new pathogenicpathogenic fungus emerging from human-induced global warming [[29].29]. C.C. auris auris isis also also osmotolerant osmotolerant and and known known to to survive survive at at high high salt salt concentrations, concentrations, which which mightmight enable itit toto survivesurvive environmentally environmentally including including hypersaline hypersaline desert desert lakes, lakes, salt-evaporat- salt-evap- oratinging ponds, ponds, or tidalor tidal pools pools (Figure (Figure2)[ 2)28 [28].]. C. C. auris aurisis is able able to to survive survive onon humanhuman skinskin and environmentalenvironmental surfaces surfaces for for several several weeks weeks and and can can even tolerate being exposed to some commonlycommonly used used disinfectants [30]. [30]. InIn terms terms of of filamentation filamentation of of C.C. auris auris, Yue, Yue et al. et showed al. showed that thatC. aurisC. auriscan switchcan switch to three to distinctthree distinct cell types cell including types including typical typical yeast, yeast,filamentation-competent filamentation-competent (FC) yeast, (FC) and yeast, a fila- and mentousa filamentous form form[31]. [Of31 ].note, Of note, typical typical yeast yeast cells cells are filamentation-incompetent are filamentation-incompetent while while FC yeastFC yeast and and filamentous filamentous cells cells are are filamentation-competent filamentation-competent under under specific specific inin vitro vitro culture conditionsconditions [31]. [31]. Furthermore, Furthermore, the the difference difference between between the typical typical yeast yeast and and filamentous filamentous cell typestypes was was variable variable among among the the expression expression levels levels of of metabolism genes. In In particular, particular, both

Microorganisms 2021, 9, 634 4 of 40

Krebs cycle- and glycolytic pathway-associated genes were downregulated in filamentous C. auris cells while fatty acid metabolism-related genes were upregulated, supporting that C. auris employs different metabolic modes to adapt to its host to reap the overall benefits of its commensal and pathogenic lifestyle [31]. Additionally, some strains of C. auris do not produce pseudohypae and show a decreased ability to assimilate different carbon sources (galactose, l−sorbose, cellobiose, l−arabinose, , glycerol, salicin, or citrate) [1]. Another morphological switch implicates the interconversion between white and opaque forms of C. auris [32]. Opaque yeast cells are more frequent colonizers in skin infections than white cells, whereas white yeast cells are much virulent in systemic infec- tions than opaque cells [33,34]. Bentz et al. showed that C. auris phenotypic switching is regulated by WOR1 that control phenotypic switching in C. auris [33]. Like C. albicans, C. auris can produce the extracellular hydrolytic enzymes that are recognized as an important virulence trait including proteinases, hemolysins, lipases and phospholipases. Regarding secreted aspartyl proteinases (SAPs), that are one of the most significant extracellular enzymes produced in Candida species [35], SAPs contribute to degradation of host tissue by providing nutrients for pathogen propagation and promote the inactivation of host peptides, the evasion of the immune responses and the induction of inflammatory mediator release from host cells [36]. In terms of the difference of SAP activity between C. auris and C. albicans, C. auris is able to maintain high SAP activity at 42 ◦C when compared to that of C. albicans supporting that C. auris maintains its pathogenicity at higher temperatures [36]. Another important group of lytic enzymes are the lipases and phospholipases that are involved in the host damage, immune evasion and biofilm formation [37,38]. In contrast to C. albicans, the production of C. auris lipases or phospholipases appears to be decreased and strain-dependent although C. auris and C. albicans share the same quantity of lipase encoding genes in the genome [39]. Hemolysin is an exotoxin that is capable of lysing red blood cells as well as nucle- ated cells and different pathogenic Candida species including C. auris display hemolysin activity [40]. C. auris strains isolated from hospital infections exhibit a high production of hemolysin when compared to those from environmental sources suggesting that hemolysin activity is involved in C. auris virulence factors (Figure2)[41]. In terms of stress sensitivities of C. auris, Hog1-related stress-activated protein kinase is an important virulence trait for fungal survival against host-imposed stresses and are highly required for the pathogenicity of many fungal pathogens during infection [42]. Day et al. showed that Hog1 is involved in regulating stress resistance, cell morphology, aggregation, and virulence in C. auris [43]. With regard to biofilm formation, in contrast to C. albicans which forms the heteroge- neous architecture of biofilms combined with blastoconidia and hyphae embedded within the extracellular matrix, C. auris produces thin biofilms composed mostly of blastoconidia and occasionally pseudohyphae embedded within very limited extracellular matrix [40]. In- terestingly, these C. auris biofilms display lower susceptibility against including polyenes, , echinocandins and when compared to those of C. albicans suggesting other mechanisms to be more important for this antifungal-resistant biofilm than the reduced biomass of C. auris or limited extracellular matrix [43–45]. Additionally, adhesion plays a key role in C. auris virulence and biofilm formation. Agglutinin-like sequence (ALS) proteins, in particular Als3, are involved in C. auris adherence [46]. Singh et al. showed that sera containing anti-Als3 antibodies prevent C. auris biofilm formation supporting an important role of Als3 in biofilm formation [47]. Knowing the specificity of C. auris and its virulence factors, different strategies are conducted to fight this emerg- ing superbug. MicroorganismsMicroorganisms2021 2021,,9 9,, 634 x 55 of 4042

3.3. Repurposing Drugs 3.1.3.1. Drugs: In Vitro Screening RepurposingRepurposing ofof drugs drugs is is an an attractive attractive pathway pathway to discoverto discover new new applications applications to already to al- developedready developed and filed and drugs. filed Drugdrugs. repositioning Drug repositioning could help could spare help substantial spare substantial costs linked costs to newlinked drug to discoverynew drug anddiscovery development. and development. It is also highly It is interestingalso highly because interesting it involves because the it useinvolves of de-risked the use compounds,of de-risked avoidingcompounds, high avoidi attritionng high rate [attrition47,48]. Therefore, rate [47,48]. this Therefore, strategy hasthis beenstrategy applied has been for repurposing applied for ofrepurposing drugs against of drugsC. auris against. It is notableC. auris. that It is the notable reported that studiesthe reported have beenstudies mainly have conductedbeen mainly in conducted vitro unless in specified. vitro unless specified. InIn thatthat context,context, thethe PrestwickPrestwick ChemicalChemical librarylibrary®®,, aa repurposingrepurposing librarylibrary ofof 12801280 smallsmall mainlymainly off-patentoff-patent molecules,molecules, hashas been screened several times by different research groups. Microorganisms 2021, 9, x 9 of 42 InIn 2018,2018, WallWall etet al.al. identified,identified, fromfrom thisthis library,library, ebselenebselen asas aa repositionablerepositionable moleculemolecule [[49].49]. EbselenEbselen isis aa synthetic synthetic organoselenium organoselenium drug drug molecule molecule with with antioxidant, antioxidant, anti-inflammatory, anti-inflamma- andtory, cytoprotective and cytoprotective activity activity (Figure (Figure3). It exhibited 3). It exhibited 100% inhibition 100% inhibition of growth of of growthC. auris ofat C. a concentrationauris at a concentration of 2.5 µM. of In 2.5 addition, µM. In addition, ebselen also ebselen inhibited also inhibited the formation the formation of biofilm of andbio- N wasfilm definedand was as defined a broad-spectrum as a broad-spectrum antifungal, antifungal, not only activenot only on activeCandida onspecies, Candida but species, also againstbut also a against variety a of variety medically of medically important important fungi, including fungi, including yeasts and yeasts molds. and molds. O Zotepine Antipsychotic 59 63 56

Cl S

FigureFigureGowri 3.3. StructuresStructures et al. studied ofof ebselenebselen sertraline, andand alexidinealexidine a repurposing dichloride.dichloride. drug classically used for the treatment of depression, against three different isolates of C. auris (Figure 4). Sertraline demon- stratedMamoueiMamouei to effectively etet al.al. recentlyrecently kill C. auris reportedreported but also thethe to resultsresults inhibit issuedissued the formation fromfrom theirtheir of ownown biofilm. screeningscreening Its mode ofof thethe of samesameaction chemicalchemical was elucidated collectioncollection by against againstin silico C.C. studies aurisauris [[50].50 and]. TheyTheyrevealed focusedfocused the bindingonon inhibitorsinhibitors nature ableable of tosertralineto blockblock thethe to fungalfungalthe sterol growthgrowth 14 α-demethylase and and to to kill kill preformed preformed which is biofilms. involvedbiofilms. The inThe bis-biguanideergosterol bis- biosynthesis alexidine alexidine dihydrochloride[52]. dihydrochlo- (AXD)ride (AXD) (Figure (Figure3), aand potent 3), aits potent and derivatives selective and selective PTPMT1have PTPMT1been (Protein recently (Protein Tyrosine patented Tyrosine Phosphatase by Phosphatase Diluccio Localized andLo- tocalizedReidenberg the Mitochondrion to the for Mitochondrion the treatment 1) inhibitor, 1) of inhibitor, blood exhibited infection exhibited the highest by theC. auris antifungalhighest [53]. antifungal Taurolidine and antibiofilm and (Figure antibiofilm activity 4) is againstactivityan antimicrobial aagainst panel ofa thatpanel pathogens, is ofused pathogens, to including try to preventincludingC. auris infections. C. auris. in catheters. ® InInOctenidine parallel,parallel, fromfromdihydrochloride thethe PrestwickPrestwick is LibraryLibrarya cationic®,, a agemini-surfactant, majormajor workwork dealingdealing derived withwith repurposing repurposingfrom pyridine ofof compoundscompounds(Figure 4). More toto fightfight than specificallyspecifically two decades againstagainst ago, C.C.it was aurisauris designed hashas beenbeen for conductedconducted skin, mucous byby ZagarozaZagaroza membrane etet al.al. and inin 20192019wound [[51].51 antisepsis.]. From this It is massive currently screening, used as 27 drugsdrugs provedprovedin a large toto field inhibitinhibit of applications thethe growthgrowth ofofas threealter-three differentdifferentnative to strainsstrainschlorhexidine, ofof C.C. aurisauris polyvidone- withwith differentdifferent geographicalgeographical or origin: origin:[54]. In CL-10093,CL-10093, 2019, Ponnachan JCMJCM 15448,15448, et al. andand re- KCTCKCTCported 1781017810 the ability (Table(Table of1 ).1). octenidine From From this this pre-selection,dihydrochloride pre-selection, the the scientiststo scientists kill C. auris carried carried strains complementary complementary [55]. studies stud- onies 10onFiftydrugs, 10 drugs, commercially namely namely MK MKavailable 801 801 hydrogen hydrogen herbicides, maleate, maleate, targeting ciclopirox acetohydroxyacid ethanolamine, ethanolamine, trifluoperazinesynthase, trifluopera- were dihydrochloride,zinerecently dihydrochloride, evaluated suloctidil, by suloctidil,Guddat ebselen, et ebselen, al. tamoxifen against tamoxifen C. citrate, auris citrate,CBS10913 rolipram, rolipram, thiethylperazinestrain. thiethylperazine Among these dimalate, com- di- guanadrelmalate,pounds, guanadrel bensulfuron sulfate, andsulfate, methyl pyrvinium and (B pyrviniumSM), pamoate, belonging pamoate, and to also the and recentlysulfonylurea also recently confirmed chemical confirmed the describedsubfamily the de- repositionable compounds such as alexidine and ebselen. scribedwas the repositionablemost potent discovered compounds antibiofilm such as alexidineformation and and ebselen. antifungal agent (Figure 4) [56].

Table 1. Active repositionable drugs against C. auris according to Zagaroza et al.

Growth Inhibition (%) at 50 µM

Structure Name Class CL JCM 15448 KCTC 17810 10093

FigureFigure 4.4. StructuresStructures ofof iodoquinol, ,Antibacterial sertra sertraline, line, taurolidine, 97 octenidine octenidine 97 dihydrochloride dihydrochloride 97 andand bensulfuronbensulfuron methyl.methyl.

3.2. Drugs: In Vitro Screening and In Vivo Validation Using medicines for malaria venture’s pathogen box, Wall et al. recently confirmed iodoquinol and miltefosine as potent inhibitors of C. auris strain 0390, both under plank- tonic and biofilm growing conditions (Figure 4) [57]. Both compounds possess broad- spectrum of activity against Candida spp., including multiple strains of the emergent C. auris, irrespective of their resistance profiles. Miltefosine (MFS) was also reported in com- bination with amphotericin B [58]. In the last few months, Barreto et al. confirmed the interest of MFS as an alternative approach to fight against the emerging fungus C. auris [59]. They reported its fungicidal activity against planktonic cells of C. auris clinical iso- lates, and antibiofilm ability. They also studied the encapsulation of MFS in alginate na- noparticles (MFS-AN). Using a Galleria mellonella larvae infected by C. auris model, they demonstrated that both MFS and MFS-AN were able to increase the survival rate. The main advantage of MFS-AN over MFS was its reduced toxicity.

Microorganisms 2021, 9, x 5 of 42

3. Repurposing Drugs 3.1. Drugs: In Vitro Screening Repurposing of drugs is an attractive pathway to discover new applications to al- ready developed and filed drugs. Drug repositioning could help spare substantial costs linked to new drug discovery and development. It is also highly interesting because it involves the use of de-risked compounds, avoiding high attrition rate [47,48]. Therefore, this strategy has been applied for repurposing of drugs against C. auris. It is notable that the reported studies have been mainly conducted in vitro unless specified. In that context, the Prestwick Chemical library®, a repurposing library of 1280 small mainly off-patent molecules, has been screened several times by different research groups. In 2018, Wall et al. identified, from this library, ebselen as a repositionable molecule [49]. Ebselen is a synthetic organoselenium drug molecule with antioxidant, anti-inflamma- tory, and cytoprotective activity (Figure 3). It exhibited 100% inhibition of growth of C. auris at a concentration of 2.5 µM. In addition, ebselen also inhibited the formation of bio- film and was defined as a broad-spectrum antifungal, not only active on Candida species, but also against a variety of medically important fungi, including yeasts and molds.

Figure 3. Structures of ebselen and alexidine dichloride.

Mamouei et al. recently reported the results issued from their own screening of the same chemical collection against C. auris [50]. They focused on inhibitors able to block the fungal growth and to kill preformed . The bis-biguanide alexidine dihydrochlo- ride (AXD) (Figure 3), a potent and selective PTPMT1 (Protein Tyrosine Phosphatase Lo- calized to the Mitochondrion 1) inhibitor, exhibited the highest antifungal and antibiofilm activity against a panel of pathogens, including C. auris. In parallel, from the Prestwick Library®, a major work dealing with repurposing of compounds to fight specifically against C. auris has been conducted by Zagaroza et al. in 2019 [51]. From this massive screening, 27 drugs proved to inhibit the growth of three different strains of C. auris with different geographical origin: CL-10093, JCM 15448, and KCTC 17810 (Table 1). From this pre-selection, the scientists carried complementary stud- ies on 10 drugs, namely MK 801 hydrogen maleate, ciclopirox ethanolamine, trifluopera- zine dihydrochloride, suloctidil, ebselen, tamoxifen citrate, rolipram, thiethylperazine di- malate, guanadrel sulfate, and pyrvinium pamoate, and also recently confirmed the de- Microorganisms 2021, 9, x scribed repositionable compounds such as alexidine and ebselen. 6 of 42

Microorganisms 2021, 9, x Table 1. Active repositionable drugs against C. auris according to Zagaroza et al. 6 of 42

Microorganisms 2021, 9, x 6 of 42 Alexidine dihydrochloride MicroorganismsMicroorganisms 2021, 20219, x , 9, 634 Growth Inhibition (%) at 506 µM of 426 of 40

Microorganisms 2021, 9Alexidine, x dihydrochloride 6 of 42

StructureAlexidine dihydrochloride Name Class CL Microorganisms 2021Alexidine, 9, x dihydrochlorideTable 1. Active repositionable drugs against C. auris according to Zagaroza et al. 6 of 42 Artemisinin Antimalarial 65 JCM56 15448 KCTC61 17810 Al