Antifungal Siderophore Conjugates for Theranostic Applications in Invasive Pulmonary Aspergillosis Using Low-Molecular TAFC Scaffolds.

Joachim Pfister,Barbara Matuszczak,Fabio Gsaller,Hubertus Haas,Milos Petrik,Matthias Misslinger,Ulrike Binder,Katerina Bendova,Clemens Decristoforo,Alexander Kühbacher

doi:10.3390/jof7070558

Abstract

Invasive pulmonary aspergillosis (IPA) is a life-threatening form of fungal infection, primarily in immunocompromised patients and associated with significant mortality. Diagnostic procedures are often invasive and/or time consuming and existing antifungals can be constrained by dose-limiting toxicity and drug interaction. In this study, we modified triacetylfusarinine C (TAFC), the main siderophore produced by the opportunistic pathogen Aspergillus fumigatus (A. fumigatus), with antifungal molecules to perform antifungal susceptibility tests and molecular imaging. A variation of small organic molecules (eflornithine, fludioxonil, thiomersal, fluoroorotic acid (FOA), cyanine 5 (Cy5) with antifungal activity were coupled to diacetylfusarinine C (DAFC), resulting in a “Trojan horse” to deliver antifungal compounds specifically into A. fumigatus hyphae by the major facilitator transporter MirB. Radioactive labeling with gallium-68 allowed us to perform in vitro characterization (distribution coefficient, stability, uptake assay) as well as biodistribution experiments and PET/CT imaging in an IPA rat infection model. Compounds chelated with stable gallium were used for antifungal susceptibility tests. [Ga]DAFC-fludioxonil, -FOA, and -Cy5 revealed a MirB-dependent active uptake with fungal growth inhibition at 16 µg/mL after 24 h. Visualization of an A. fumigatus infection in lungs of a rat was possible with gallium-68-labeled compounds using PET/CT. Heterogeneous biodistribution patterns revealed the immense influence of the antifungal moiety conjugated to DAFC. Overall, novel antifungal siderophore conjugates with promising fungal growth inhibition and the possibility to perform PET imaging combine both therapeutic and diagnostic potential in a theranostic compound for IPA caused by A. fumigatus.

Highlights

Invasive aspergillosis (IA) is a severe infection in humans, associated with high mortality and an estimated incidence of 250,000 cases a year worldwide [1,2]
Exact analytical data are provided in the Supplementary Materials
Antimicrobial siderophores have been attracting the interest of scientists for many decades

Summary

Introduction

Invasive aspergillosis (IA) is a severe infection in humans, associated with high mortality and an estimated incidence of 250,000 cases a year worldwide [1,2]. IA most commonly involves the lungs resulting in invasive pulmonary aspergillosis (IPA) in immunocompromised patients with Aspergillus fumigatus (A. fumigatus) as the most common opportunistic pathogen involved [3,4]. J. Fungi 2021, 7, 558 monly involves the lungs resulting in invasive pulmonary aspergillosis (IPA) in immun of ocompromised patients with Aspergillus fumigatus (A. fumigatus) as the most common opportunistic pathogen involved [3,4]

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