Poster Presentation The 47th Lorne Conference on Protein Structure and Function 2022

Developing inhibitors against fungal inositol polyphosphate kinases (IPK) as a novel class of antifungal drug (#337)

Desmarini Desmarini 1 2 3 , Daniel Truong 4 , Philip Thompson 4 , Xiaodong Wang 5 , Lorna Wilkinson-White 6 , Mario Torrado 6 , Sophie Lev 1 2 3 , Julie Djordjevic 1 2 3
  1. Centre for Infectious Diseases and Microbiology, The Westmead Institute for Medical Research, Westmead, NSW, Australia
  2. Faculty of Medicine and Health, The University of Sydney, Sydney, NSW, Australia
  3. Sydney Institute for Infectious Diseases, Sydney, NSW, Australia
  4. Medicinal Chemistry, Monash Institute of Pharmaceutical Science, Monash University, Melbourne, VIC, Australia
  5. Center for Integrative Chemical Biology and Drug Discovery, Eshelman School of Pharmacy, University of North Carolina, Chapel Hill, NC, USA
  6. Sydney Analytical Core Facility, The University of Sydney, Sydney, NSW, Australia

Background:

Invasive fungal infections (IFIs) kill ~1.5 million people each year. Despite this, few antifungal drug classes are available to treat IFIs and they have poor efficacy and/or significant toxicity. Furthermore, drug-resistant fungi have emerged. New drug classes are urgently required to address this unmet global medical need.

Aim:

Our aim is to develop a novel class of antifungal drug targeting inositol polyphosphate (IP) kinases (IPK). These drugs would have a different mode of action to current drugs, which predominantly block cell wall and ergosterol biosynthesis. We and others showed that genetically ablating the kinase that produces IP4 and IP5 (IP3-4 kinase) in the major human fungal pathogens, Cryptococcus neoformans and Candida albicans, leads to multiple cellular defects and avirulence or lethality [1-3]. These data suggest that inhibition of IP3-4 kinase would clear a fungal infection by inhibiting numerous cellular functions as opposed to a single function inhibited by the current drugs.

Methods:       

We used 2 approaches to develop IPK inhibitors:

(1) rational design from two molecular starting points; dibenzylpurines (DBP), which we showed have selectivity for fungal over human IPKs (Monash collaboration) and a novel scaffold provided by University of North Carolina (UNC);

(2) fragment-based drug discovery (FBDD).

To complete each approach, we purified recombinant IP3K from C. neoformans and C. albicans and developed assays to assess inhibitor potency.

Results:

We synthesised 44 DBP analogues. However, the half-inhibitory concentration (IC50) of these analogues remained too high against Cryptococcus IP3-4 kinase (µM IC50s) and none inhibited Candida IP3-4 kinase. In contrast, UNC analogues had IC50s of 30nM/400nM for Cryptococcus/Candida IP3-4 kinase. FBDD identified 3 new molecular scaffolds that inhibited both fungal IP3-4 kinase.

Conclusion:

(1) The UNC compounds are a promising scaffold for developing potent, pan fungal IP3-4 kinase inhibitors.

(2) FBDD identified additional novel lead scaffolds with scope for development into pan fungal IPK inhibitors.

  1. Lev, S., Desmarini, D., Li, C., Chayakulkeeree, M., Traven, A., Sorrell, T. C., & Djordjevic, J. T. (2013). Phospholipase C of Cryptococcus neoformans regulates homeostasis and virulence by providing inositol trisphosphate as a substrate for Arg1 kinase. Infection and immunity, 81(4), 1245–1255. https://doi.org/10.1128/IAI.01421-12
  2. Li, J., Zhang, B., Ma, T., Wang, H., Zhang, B., Yu, Q., & Li, M. (2017). Role of the Inositol Polyphosphate Multikinase Ipk2 in Regulation of Hyphal Development, Calcium Signaling and Secretion in Candida albicans. Mycopathologia, 182(7-8), 609–623. https://doi.org/10.1007/s11046-017-0138-4
  3. Li, C., Lev, S., Desmarini, D., Kaufman-Francis, K., Saiardi, A., Silva, A., Mackay, J. P., Thompson, P. E., Sorrell, T. C., & Djordjevic, J. T. (2017). IP3-4 kinase Arg1 regulates cell wall homeostasis and surface architecture to promote Cryptococcus neoformans infection in a mouse model. Virulence, 8(8), 1833–1848. https://doi.org/10.1080/21505594.2017.1385692