Caspofungin

BackgroundRezafungin (RZF) is a novel echinocandin exhibiting distinctive pharmacokinetics/pharmacodynamics. STRIVE was a phase 2, double-blind, randomized trial designed to compare the safety and efficacy of RZF once weekly (QWk) to caspofungin (CAS) once daily for treatment of candidemia and/or invasive candidiasis (IC).MethodsAdults with systemic signs and mycological confirmation of candidemia and/or IC were randomized to RZF 400 mg QWk (400 mg), RZF 400 mg on week 1 then 200 mg QWk (400/200 mg), or CAS 70 mg as a loading dose followed by 50 mg daily for ≤4 weeks. Efficacy assessments included overall cure (resolution of signs of candidemia/IC + mycological eradication) at day 14 (primary endpoint), investigator-assessed clinical response at day 14, and 30-day all-cause mortality (ACM) (secondary endpoints), and time to negative blood culture. Safety was evaluated by adverse events and ACM through follow-up.ResultsOf 207 patients enrolled, 183 were in the microbiological intent-to-treat population (~21% IC). Overall cure rates were 60.5% (46/76) for RZF 400 mg, 76.1% (35/46) for RZF 400/200 mg, and 67.2% (41/61) for CAS; investigator-assessed clinical cure rates were 69.7% (53/76), 80.4% (37/46), and 70.5% (43/61), respectively. In total, 30-day ACM was 15.8% for RZF 400 mg, 4.4% for RZF 400/200 mg, and 13.1% for CAS. Candidemia was cleared in 19.5 and 22.8 hours in RZF and CAS patients, respectively. No concerning safety trends were observed; ACM through follow-up was 15.2% (21/138) for RZF and 18.8% (13/69) for CAS.ConclusionsRZF was safe and efficacious in the treatment of candidemia and/or IC.Clinical trials registrationNCT02734862.

Aneuploidy is common both in tumor cells responding to chemotherapeutic agents and in fungal cells adapting to antifungal drugs. Because aneuploidy simultaneously affects many genes, it has the potential to confer multiple phenotypes to the same cells. Here, we analyzed the mechanisms by which Candida albicans, the most prevalent human fungal pathogen, acquires the ability to survive both chemotherapeutic agents and antifungal drugs. Strikingly, adaptation to both types of drugs was accompanied by the acquisition of specific whole-chromosome aneuploidies, with some aneuploid karyotypes recovered independently and repeatedly from very different drug conditions. Specifically, strains selected for survival in hydroxyurea, an anticancer drug, acquired cross-adaptation to caspofungin, a first-line antifungal drug, and both acquired traits were attributable to trisomy of the same chromosome: loss of trisomy was accompanied by loss of adaptation to both drugs. Mechanistically, aneuploidy simultaneously altered the copy number of most genes on chromosome 2, yet survival in hydroxyurea or caspofungin required different genes and stress response pathways. Similarly, chromosome 5 monosomy conferred increased tolerance to both fluconazole and to caspofungin, antifungals with different mechanisms of action. Thus, the potential for cross-adaptation is not a feature of aneuploidy per se; rather, it is dependent on specific genes harbored on given aneuploid chromosomes. Furthermore, pre-exposure to hydroxyurea increased the frequency of appearance of caspofungin survivors, and hydroxyurea-adapted C. albicans cells were refractory to antifungal drug treatment in a mouse model of systemic candidiasis. This highlights the potential clinical consequences for the management of cancer chemotherapy patients at risk of fungal infections.

Candida species are known to differ in their ability to cause infection and have been shown to display varied susceptibilities to antifungal drugs. Treatment with the echinocandin, caspofungin, leads to compensatory alterations in the fungal cell wall. This study was performed to compare the structure and composition of the cell walls of different Candida species alone and in response to caspofungin treatment, and to evaluate how changes at the fungal cell surface affects interactions with macrophages. We demonstrated that the length of the outer fibrillar layer varied between Candida species and that, in most cases, reduced fibril length correlated with increased exposure of β-1,3-glucan on the cell surface. Candida glabrata and Candida guilliermondii, which had naturally more β-1,3-glucan exposed on the cell surface, were phagocytosed significantly more efficiently by J774 macrophages. Treatment with caspofungin resulted in increased exposure of chitin and β-1,3-glucan on the surface of the majority of Candida species isolates that were tested, with the exception of C. glabrata and Candida parapsilosis isolates. This increase in exposure of the inner cell wall polysaccharides, in most cases, correlated with reduced uptake by macrophages and in turn, a decrease in production of TNFα. Here we show that differences in the exposure of cell wall carbohydrates and variations in the repertoire of covalently attached surface proteins of different Candida species contributes to their recognition by immune cells.

Hyphal forms of human pathogenic fungi cause invasive disease in humans, but the hyphal response to antifungals is understudied. In the major fungal pathogens Aspergillus fumigatus and Candida albicans, we used microfluidic-coupled, fluorescence-mediated live-cell imaging to capture the real-time responses of fungal hyphae to clinical concentrations of AmBisome or Caspofungin. In both fungi, AmBisome exposure caused rapid growth arrest (2 M deaths per year and we have a limited number of antifungals in the clinic to combat these infections. Those drugs are increasingly meeting resistance in killer fungi and our understanding of drug responses are limited. Our main assessment of antifungal resistance comes from end-point 48 h drug culture of the fungus and is performed by eye for presence of absence of growth in a well. Further, these tests are performed on the pre-invasive form of the fungus, the yeast or spore (for speed and simplicity), not the invasive filamentous form present during systemic infection of organs in humans. This work shows how the invasive filamentous form of two major human fungal pathogens respond to two frontline clinical antifungal drugs with real time microscopy. We describe the cell death and/or adaptive growth responses via live-cell microscopy to understand the morphological and cellular responses over time. We were able to do this by coupling fluorescently engineered pathogens and live-cell 4D microscopy to microfluidic delivery of culture media and/or antifungal drug. We used the triggerable microfluidics to first establish invasive filamentous growth without drug, and keep the cells in the same focal plane (with shallow roof that kept the filaments growing up out of the focal plane). We then triggered the switch to media with drug(s) to perfuse drug while observing comparative cellular responses live, up to 10 h in two pathogenic fungi. In both pathogens (Aspergillus fumigatus and Candida albicans) we saw similar immediate responses to one drug (Ambisome), which inhibited filamentous growth almost immediately. In stark contrast, Caspofungin induced different but continued forms of growth to known inhibitory doses against invasive fungal filaments. A. fumigatus (a filamentous mould fungus) appeared hard-wired to continue filamentous growth by various compensatory regenerative growth forms, including a novel 'resuscitative' form we describe which occurs after the drug causes filament bursting. However, C. albicans filaments (a polymorphic yeast) respond by transitioning from filamentous to yeast growth (all filaments eventually burst, leaving only budding yeast). This study details the short- and long-term responses of invasive pathogenic fungal filaments to drugs and highlights that the traditional spore/yeast-derived inhibitory doses for these fungi may be insufficient for the invasive form of the fungus, where more attention to the filamentous form is needed.