Nanocrystal Technology Applied to the Treatment and Diagnosis of Neurodegenerative Diseases

Amphotericin B Fluconazole Itraconazole Voriconazole Posaconazole Echinocandin Terbinafine

Candida auris +

A calidoustus +

Fusarium solani

+ Scedosporium spp NA Lomentospora prolificans C tropicalis + Candida parapsilosis NA C glabrata +

Aspergillus fumigatus Mucorales NA

Trichophyton spp. NA ++ NA + NA NA

+ NA + NA

+ NA NA

++ NA ++ NA

+ NA NA

NA NA + NA

NA

NA

++ NA NA NA NA NA

NA

NA NA NA

NA

NA

Table 3: Fungal species with their resistant anti-fungals; ++ Highly resistant to anti-fungals, + some resistance, NA = not active or used

selected. This may be observed among the patients with chronic fungal infections who are supposed to take prolonged anti-fungal treatment courses. Some of these patients show poor compliance with drug regimens (often linked with toxicity or poverty) allowing for the selection of resistance fungi. For example, increased use of azole for prophylaxis and long-term use of azole in chronic conditions are linked with azole resistance in Aspergillus species [Verweij, P.E., et al. 2020].

Anti-fungals have been used widely in the agriculture sector to prevent fungal infections in crops. Azole-based agricultural fungicides are a cornerstone of the crop protection market(including prochloraz, difenoconazole, propiconazole, hexaconazole and tebuconazole) [Darwin, J., et al. 2015]. However, the wide use of fungicides in agriculture is closely linked to creating environmental niches for fungi (Aspergillus in particular) to become resistant. Agricultural fungicides which share similar molecular targets with systemic azole anti-fungals are reported to cause the selection of resistant fungal species. [Verweij, P.E., et al. 2020] [Denning, D.W., 2022].

Why we need to prevent antifungal resistance

Anti-fungals play a pivotal role in the treatment of human fungal infections and a successful therapeutic outcome mandates effective anti-fungal treatment. Emerging and spreading antifungal resistance make existing antifungals ineffective. The only oral class of anti-fungals for Aspergillus infections is the azole, and so pan-azole resistance commits patients to intravenous therapy only. Even common fungal infections become harder to treat resulting in severe infections and death. Since a few classes of anti-fungals are available, the emergence of drug resistance severely limits the therapeutic options while multi-drug resistance and pan drug resistance annihilate almost all options. In addition, patients with resistant fungal infections require specific expensive management and prolonged hospital stay.

With the rising at-risk population, the requirement for new strong antifungals is growing. However, the development of new powerful anti-fungals is at a slow pace. Moreover, some anti-fungals show a limited spectrum of activity. Consequently, it is vital to curb anti-fungal resistance because so few anti-fungals are currently available, with only a few new molecules in development.

Moreover, low, and middle-income countries commonly have only some of the quality anti-fungals available in high-income countries. A rising incidence of resistant strains there is not manageable in many of these countries.

How to prevent anti-fungal resistance

The emergence and spread of resistant fungi is now a widespread and global threat. Consequently, we all must fight this problem together, linked with antibacterial resistance countermeasures. A multifaceted approach at the healthcare level, community level, and industry level is necessary.

The health care sectors in each country can contribute to the containment of resistant fungi through meticulous screening by culture, species identification, and susceptibility testing. Good infection control measures are essential, including air protection measures for vulnerable patients. The incorporation of anti-fungal stewardship programs (including rapid diagnostics to minimise unnecessary antibacterial or antifungal therapy) into routine practice will minimise the emergence and spread of resistance among fungi.

Meanwhile, scientists are continuing to develop new laboratory tests to detect resistant fungal infections. Such novel methods will need clinical trials to demonstrate their worth, and these trials need public funding.

Epidemiological research and surveillance are also key to understanding the emergence and spread of anti-fungal resistance. The gathering of data on anti-fungal resistance through

FUNGAL INFECTION GLOBAL BURDEN REFERENCE

Fungal keratitis 1.0 to 1.4 million eyes affected annually, at least 60 per cent blindness and ~10 per cent loss of eye

IA in COPD populations 760,017 – 2,272,322 cases annually, 45-70 per cent mortality when diagnosed and treated

Cryptococcal meningitis 223,100 cases in HIV/AIDS annually, 15-70 per cent mortality when treated

Recurrent vulvovaginal candidiasis

Chronic pulmonary aspergillosis

Candidemia

Mucormycosis 137 million women affected in any one year

~ 3 million affected in any one year, 20 per cent 1 year mortality, 50 per cent five year mortality

3-21/100,000 globally (ie>750,000) with ~45 per cent annual mortality treated

Pre-COVID-19, 140 /million in India (170,000), with ~45 per cent mortality treated. Brown, L., Leck, A.K., Gichangi, M., Burton, M.J. and Denning, D.W., 2021. The global incidence and diagnosis of fungal keratitis. The Lancet Infectious Diseases, 21(3), pp.e49-e57. 1 051 787 cases

Hammond, E.E., McDonald, C.S., Vestbo, J. and Denning, D.W., 2020. The global impact of Aspergillus infection on COPD. BMC pulmonary medicine, 20(1), pp.1-10.

Rajasingham, R., Smith, R.M., Park, B.J., Jarvis, J.N., Govender, N.P., Chiller, T.M., Denning, D.W., Loyse, A. and Boulware, D.R., 2017. Global burden of disease of HIV-associated cryptococcal meningitis: an updated analysis. The Lancet Infectious Diseases, 17(8), pp.873-881.

Denning, D.W., Kneale, M., Sobel, J.D. and Rautemaa-Richardson, R., 2018. Global burden of recurrent vulvovaginal candidiasis: a systematic review. The Lancet infectious diseases, 18(11), pp.e339-e347.

Denning, D.W., Pleuvry, A. and Cole, D.C., 2011. Global burden of chronic pulmonary aspergillosis as a sequel to pulmonary tuberculosis. Bulletin of the World Health Organization, 89, pp.864-872.

Centers for Disease Control and Prevention. Invasive Candidiasis Statistics https:// www.cdc.gov/fungal/diseases/candidiasis/invasive/statistics.html Accessed April 20, 2022.

WHO.Mucormycosis .https://www.who.int/india/emergencies/coronavirus-disease(covid-19)/mucormycosis Accessed April 20 2022

Table 4: Incidence or prevalence of several serious fungal infections, in which anti-fungal resistance compromises therapy

anti-fungal resistance surveillance (hospital, and environmental) programs aids in mapping resistance trends. Resistance should be sought not only in the healthcare sector but also in agriculture settings. Surveillance of anti-fungal resistance should be a global enterprise, and databases of anti-fungal resistance openly shared. In addition, financial and technical assistance for low-resource countries should be provided to identify and contain resistant fungal species. The expansion of infrastructure for tracing and testing anti-fungal resistance and for surveillance programs should be a priority.

The consumption of anti-fungals in a responsible manner will help to curtail this issue. As a community, we should avoid sub-therapeutic doses of anti-fungals (and poorly bioavailable generic preparations) which are more likely to select resistant strains. Overthe-counter anti-fungal treatment is strongly associated with the development of anti-fungal resistance in the skin fungus Trichophyton and should be avoided. Azole fungicide use should be minimised and alternative means of addressing crop fungal pathogens utilised.

References are available at www.pharmafocusasia.com

AUTHOR BIO

L Shamithra M Sigera is a Sri Lankan who is currently attached to Manchester Fungal Infection Group as a research fellow for the completion of overseas postgraduate training in medical mycology. She did her undergraduate medical training at the University of Kelaniya, Sri Lanka. She then completed internship in General Surgery and Paediatrics and worked as a Medical Officer in Paediatrics. She has a special interest in medical mycology.

David W Denning is an infectious diseases clinician with expertise in fungal diseases. He serves as the Chief Executive of Global Action For Fungal Infections (GAFFI) and Professor of Infectious Diseases and Global Health at the University of Manchester, UK. He leads LIFE (Leading International Fungal Education (http://fungaleducation.org/), which is focused on improving patient outcomes through online education and the Aspergillus Website (www.Aspergillus.org.uk). GAFFI (www.GAFFI. org) advocates for universal access to fungal diagnostics and antifungal therapies. He is also a member of the SEARO Task Force on Antimicrobial Resistance (AMR).

Poor bioavailability of many approved and yet-to-be-approved drugs for the treatment of brain disorders represents a pharmaceutical challenge. Despite the high pharmacological activity, limited water solubility leads to poor absorption and sub-therapeutic drug concentrations at the target site. The formulation of drug nanocrystals (NCs) emerges as a promising approach for different administration routes to enhance the brain delivery of hydrophobic drugs.

Elide Zingale, University of Catania Angela Bonaccorso, Researcher, Department of Drug and Health Sciences, University of Catania Rosario Pignatello, Full Professor, Pharmaceutical Technology and Legislation, University of Catania

An obstacle in the development of new therapies is often the poor solubility of many drugs in the research pipeline. Almost 90 per cent of them have a little or no water solubility. The term 'poor solubility' applies when the maximum concentration of drug dissolved in water is <10 mg/mL; a molecule is defined as 'insoluble' at a maximum dissolved concentration of 0.1 mg/mL. Water solubility affects dissolution in aqueous fluids and thus the bioavailability of the molecule. A common consequence is an increased required dosage or repeated administrations to reach the wished therapeutic concentrations. Many of these molecules belong to classes II and IV of the Biopharmaceutical Classification System (BCS) and are suitable to be designed as NCs. In fact, nanonisation is one of the simplest and most effective strategies to increase the solubility, dissolution and bioavailability performance of these drugs.

Nanocrystals technology

Drug NCs are solid drug particles in the nanometer range surrounded by a stabiliser layer. If prepared as aqueous suspension, they can also be called nanosuspensions. The choice of the stabiliser is important since it can influence the physico-chemical properties of the formulation and its in vivo behaviour. Many stabilisers act as absorption promoters improving the bioavailability of the drug.