Olorofim and the azoles are antagonistic in A. fumigatus and functional genomic screens reveal mechanisms of cross resistance.

Abstract

Aspergillosis, in its various manifestations, is a major cause of morbidity and mortality. Very few classes of antifungal have been approved for clinical use to treat these diseases and resistance to the first line therapeutics is increasing. A new class of antifungals, the orotomides, are currently in development with the first compound in this class olorofim in late-stage clinical trials. In this study, we characterise a network of genes that govern olorofim response in A. fumigatus. We reveal that the number of transcription factors that regulate olorofim susceptibility are far fewer than we have previously observed for the azoles and the change in sensitivity observed in these isolates is less extreme. Intriguingly, loss of function in two higher order transcriptional regulators, HapB a member of the heterotrimeric HapB/C/E (CBC) complex or the regulator of nitrogen metabolic genes AreA, leads to cross resistance to both the azoles and olorofim. However, a clinical azole resistant isolate with a point mutation in HapE (hapEP88L) retains sensitivity to olorofim. Our transcriptomic analysis suggests that altered sensitivity to olorofim may emerge via modification of genes involved in the production of pyrimidine biosynthetic precursors. Finally, we also show that the action of the azoles are antagonistic to olorofim in vitro.

The importance of antimicrobial resistance in medical mycology

“…Alternatively, studies may be initiated earlier in new drug development, based on careful PK-PD studies in animal models, and driven by industry or academia. Care should be taken that combinations are not used without good evidence of efficacy -especially given that some combinations maybe antagonistic, at least in vitro 112 . Within industry, the priority must be to obtain licensure, usually with use in monotherapy, although in tuberculosis and HIV there is strong precedent for the licensing of treatments in combination 113 , which provides a possible additional pathway for new drugs including any selected from the start for synergies with current agents.…”

Pandemic Response Box® library as a source of antifungal drugs against Scedosporium and Lomentospora species

“…Interactions between olorofim and antifungal drugs revealed antagonist effect with voriconazol. Antagonism between olorofim and azoles, specifically itraconazole and voriconazole, has also been previously reported for A. fumigatus [52]. However, the mechanism that leads to antagonism between olorofim and azoles remains unclear and further studies are needed for its elucidation.…”

Exploring the intersection of Aspergillus fumigatus biofilms, infections, immune response and antifungal resistance

“…Olorofim is currently undergoing phase III of clinical trials to assess its safety and efficacy against different mould infections, including for IA. 104 Related studies have demonstrated high fungicidal activity of TA B L E 1 Different genes encoded in A. fumigatus and their associated virulence characteristics including conidial virulence properties and biofilm formation. Regulates the expression of genes, uge3 and agd3, of the GAG gene cluster, and the expression of medA and stuA by forming a complex of SomA/PtaB, mediates fungal growth, adherence and development olorofim against azole-resistant A. fumigatus in its planktonic and early developmental stages of biofilm formation, particularly during conidia adhesion and germination.…”

“…This results in vital cellular processes requiring pyrimidine, such as DNA and RNA synthesis, to stop, 103 and subsequently, induces fungal cell lysis and death. Olorofim is currently undergoing phase III of clinical trials to assess its safety and efficacy against different mould infections, including for IA 104 . Related studies have demonstrated high fungicidal activity of olorofim against azole‐resistant A. fumigatus in its planktonic and early developmental stages of biofilm formation, particularly during conidia adhesion and germination 105 …”