Miltefosine Against Scedosporium and Lomentospora Species: Antifungal Activity and Its Effects on Fungal Cells

Targeting CCR5 with miltefosine as a therapeutic strategy for thrombocytopenia

Thrombocytopenia remains a challenging clinical condition with limited treatment options. Here, we demonstrated that miltefosine stimulated megakaryocyte (MK) differentiation in vitro. Miltefosine significantly accelerated platelet recovery, enhanced platelet function, and boosted MK production and differentiation in irradiated mice. RNA sequencing revealed association of CCR5, MAPK, and JAK2/STAT3 signaling pathways in miltefosine-mediated MK differentiation. Molecular docking, drug affinity responsive target stability (DARTS), and surface plasmon resonance (SPR) assays confirmed direct binding of miltefosine to CCR5. Inhibition of CCR5 disrupted miltefosine's effects on MK differentiation and activation of MAPK and JAK2/STAT3 signaling pathways, as well as key transcription factors GATA1, EGR1, and TAL1. Similarly, blockade of the MAPK or JAK2/STAT3 signaling pathways hindered miltefosine-induced MK differentiation and transcription factor activation. Our findings establish CCR5 as a therapeutic target for thrombocytopenia and identify miltefosine as a CCR5 agonist that promotes MK differentiation and platelet production via MAPK and JAK2/STAT3 signaling.

A polyene macrolide targeting phospholipids in the fungal cell membrane

The global spread of multidrug-resistant pathogenic fungi presents a serious threat to human health, necessitating the discovery of antifungals with unique modes of action1. However, conventional activity-based screening for previously undescribed antibiotics has been hampered by the high-frequency rediscovery of known compounds and the lack of new antifungal targets2. Here we report the discovery of a polyene antifungal antibiotic, mandimycin, using a phylogeny-guided natural-product discovery platform. Mandimycin is biosynthesized by the mand gene cluster, has evolved in a distinct manner from known polyene macrolide antibiotics and is modified with three deoxy sugars. It has demonstrated potent and broad-spectrum fungicidal activity against a wide range of multidrug-resistant fungal pathogens in both in vitro and in vivo settings. In contrast to known polyene macrolide antibiotics that target ergosterol, mandimycin has a unique mode of action that involves targeting various phospholipids in fungal cell membranes, resulting in the release of essential ions from fungal cells. This unique ability to bind multiple targets gives it robust fungicidal activity as well as the capability to evade resistance. The identification of mandimycin using the phylogeny-guided natural-product discovery strategy represents an important advancement in uncovering antimicrobial compounds with distinct modes of action, which could be developed to combat multidrug-resistant fungal pathogens.

A Novel Niosomal Gel for Topical Delivery of Miltefosine Against Trichophyton indotineae Dermatophytosis in Animal Model

INTRODUCTION

Dermatophytosis, a cutaneous fungal infection worldwide, is generally localised to the skin's superficial layers and keratinised structures. Although most agents are susceptible to current antifungal drugs available in clinical settings, frequent relapses and failures, especially in cases due to Trichophyton indotineae, have been frequently reported. Therefore, alternative targets and therapeutic approaches are highly required. In the present study, we compared the efficacies of terbinafine with conventional and niosomal forms of miltefosine (MFS) against dermatophytosis in the guinea pig model.

MATERIAL AND METHODS

Initially, 30 guinea pigs were divided into five groups (e.g., untreated control, treated groups by MFS niosomal gel 1%, MFS gel 1%, terbinafine 1% and niosome) and were infected with terbinafine-resistant Trichophyton indotineae and subsequently scored both clinically and mycologically until day 35 of inoculation. MFS was encapsulated into niosomes, elastic vesicles made of non-ionic surfactants that enhance drug delivery through the skin.

RESULTS

Results showed that the MFS niosomal gel 1% significantly reduced lesion scores, mycological evidence of infection and inflammation compared to the untreated control and terbinafine-treated groups (p < 0.05). Moreover, the lesion score in the niosomal gel and terbinafine groups did not differ from the untreated control (p > 0.05). Histopathological analysis confirmed reduced epidermal thickening and fungal burden in treated models with the MFS niosomal gel 1%.

CONCLUSION

The findings highlighted MFS niosomal gel 1% as a potentially effective, targeted therapy for drug-resistant T. indotineae, offering a safer and more effective alternative to topical and oral antifungal treatments. However, further studies are warranted to continue correlating these findings with more clinical outcomes.

Two cases of fungemia due to Lomentospora prolificans in haematological patients with different outcome

Lomentospora prolificans is an uncommon cause of invasive fungal disease, but it is associated with high mortality because it is difficult to treat. Most of severe cases are produced in immunossupressed patients, especially in those with neutropenia and/or hematological malignancies. Resistance to the majority of antifungal agents can be still observed. Here we report two cases of L. prolificans fungemia with different outcome, since in one of these patients treatment with one of the new antifungals could be applied. Both patients were treated with different antifungal drugs, but only the second one survived due to therapy with fosmanogepix®. The current treatment is still based on a combination of conventional antifungal drugs, although in much cases this strategy is not sufficient. The introduction of new promising antifungal agents such as fosmanogepix® and olorofim® may open new perspectives in the treatment of invasive infections caused by L. prolificans, as in our patient.

Milteforan, a promising veterinary commercial product against feline sporotrichosis

Sporotrichosis, the cutaneous mycosis most commonly reported in Latin America, is caused by the Sporothrix clinical clade species, including Sporothrix brasiliensis and Sporothrix schenckii sensu stricto. Due to its zoonotic transmission in Brazil, S. brasiliensis represents a significant health threat to humans and domestic animals. Itraconazole, terbinafine, and amphotericin B are the most used antifungals for treating sporotrichosis. However, many strains of S. brasiliensis and S. schenckii have shown resistance to these agents, highlighting the importance of finding new therapeutic options. Here, we demonstrate that milteforan, a commercial veterinary product against dog leishmaniasis, whose active principle is miltefosine, is a possible therapeutic alternative for the treatment of sporotrichosis, as observed by its fungicidal activity in vitro against different strains of S. brasiliensis and S. schenckii. Fluorescent miltefosine localizes to the Sporothrix cell membrane and mitochondria and causes cell death through increased permeabilization. Milteforan decreases S. brasiliensis fungal burden in A549 pulmonary cells and bone marrow-derived macrophages and also has an immunomodulatory effect by decreasing TNF-α, IL-6, and IL-10 production. Our results suggest milteforan as a possible alternative to treat feline sporotrichosis.

IMPORTANCE

Sporotrichosis is an endemic disease in Latin America caused by different species of Sporothrix. This fungus can infect domestic animals, mainly cats and eventually dogs, as well as humans. Few drugs are available to treat this disease, such as itraconazole, terbinafine, and amphotericin B, but resistance to these agents has risen in the last few years. Alternative new therapeutic options to treat sporotrichosis are essential. Here, we propose milteforan, a commercial veterinary product against dog leishmaniasis, whose active principle is miltefosine, as a possible therapeutic alternative for treating sporotrichosis. Milteforan decreases S. brasiliensis fungal burden in human and mouse cells and has an immunomodulatory effect by decreasing several cytokine production.

Ophthalmic adverse effects of miltefosine in the treatment of leishmaniasis: a systematic review

OBJECTIVE

Miltefosine stands as the sole oral medication approved for the treatment of leishmaniasis. The appearance of severe ophthalmic toxicities induced by miltefosine in the context of leishmaniasis treatment is a matter of significant concern. The main objective of this study is to present a comprehensive summary of the ophthalmic adverse effects associated with miltefosine when used in the treatment of leishmaniasis.

METHODS

A systematic search was performed on PubMed, ScienceDirect, Embase, Scopus, and Google Scholar, covering articles from inception up to June 2023, without language restrictions, to identify relevant studies documenting ocular toxicity following miltefosine treatment for leishmaniasis.

RESULTS

A total of eight studies involving 31 leishmaniasis patients who developed ocular toxicities while undergoing miltefosine treatment were included in the analysis. These studies were conducted in various regions, with five originating from India, two from Bangladesh, and one from Nepal. Patients presented a spectrum of ophthalmic complications, including uveitis, keratitis, scleritis, and Mooren's ulcer. Commonly reported symptoms included pain, redness, excessive tearing, partial vision impairment, permanent blindness, light sensitivity, and the appearance of white spots on the eye. On average, patients received miltefosine treatment for a duration of 47 days before experiencing the onset of ocular problems. It is important to note that the risk of ocular toxicities increases with prolonged use of miltefosine.

CONCLUSIONS

Therefore, to mitigate the potential for irreversible damage to the eyes, it is imperative that all individuals undergoing miltefosine therapy undergo regular eye examinations.

Strategies of Pharmacological Repositioning for the Treatment of Medically Relevant Mycoses

Fungal infections represent a worldwide concern for public health, due to their prevalence and significant increase in cases each year. Among the most frequent mycoses are those caused by members of the genera Candida, Cryptococcus, Aspergillus, Histoplasma, Pneumocystis, Mucor, and Sporothrix, which have been treated for years with conventional antifungal drugs, such as flucytosine, azoles, polyenes, and echinocandins. However, these microorganisms have acquired the ability to evade the mechanisms of action of these drugs, thus hindering their treatment. Among the most common evasion mechanisms are alterations in sterol biosynthesis, modifications of drug transport through the cell wall and membrane, alterations of drug targets, phenotypic plasticity, horizontal gene transfer, and chromosomal aneuploidies. Taking into account these problems, some research groups have sought new therapeutic alternatives based on drug repositioning. Through repositioning, it is possible to use existing pharmacological compounds for which their mechanism of action is already established for other diseases, and thus exploit their potential antifungal activity. The advantage offered by these drugs is that they may be less prone to resistance. In this article, a comprehensive review was carried out to highlight the most relevant repositioning drugs to treat fungal infections. These include antibiotics, antivirals, anthelmintics, statins, and anti-inflammatory drugs.

Scedosporiosis and lomentosporiosis: modern perspectives on these difficult-to-treat rare mold infections

SUMMARYAlthough Scedosporium species and Lomentospora prolificans are uncommon causes of invasive fungal diseases (IFDs), these infections are associated with high mortality and are costly to treat with a limited armamentarium of antifungal drugs. In light of recent advances, including in the area of new antifungals, the present review provides a timely and updated overview of these IFDs, with a focus on the taxonomy, clinical epidemiology, pathogenesis and host immune response, disease manifestations, diagnosis, antifungal susceptibility, and treatment. An expansion of hosts at risk for these difficult-to-treat infections has emerged over the last two decades given the increased use of, and broader population treated with, immunomodulatory and targeted molecular agents as well as wider adoption of antifungal prophylaxis. Clinical presentations differ not only between genera but also across the different Scedosporium species. L. prolificans is intrinsically resistant to most currently available antifungal agents, and the prognosis of immunocompromised patients with lomentosporiosis is poor. Development of, and improved access to, diagnostic modalities for early detection of these rare mold infections is paramount for timely targeted antifungal therapy and surgery if indicated. New antifungal agents (e.g., olorofim, fosmanogepix) with novel mechanisms of action and less cross-resistance to existing classes, availability of formulations for oral administration, and fewer drug-drug interactions are now in late-stage clinical trials, and soon, could extend options to treat scedosporiosis/lomentosporiosis. Much work remains to increase our understanding of these infections, especially in the pediatric setting. Knowledge gaps for future research are highlighted in the review.

Meeting the Therapeutic Challenges of Emergent and Rare Invasive Fungal Diseases Through Novel Clinical Trial Designs

Treatments for emerging and rare invasive fungal diseases (IFDs) represent a critical unmet medical need. For IFDs that occur less frequently than invasive aspergillosis, such as mucormycosis, hyalohyphomycosis, and phaeohyphomycosis, randomized controlled clinical trials are impractical and unlikely to meet urgent public health needs. Understanding regulatory approaches for approval of drugs for rare cancers and rare metabolic diseases could help meet the challenges of studying drugs for rare IFDs. A single-arm, controlled clinical trial with a high-quality external control(s), with confirmatory evidence from nonclinical studies, including pharmacokinetic/pharmacodynamic data in predictive animal models of the disease may support findings of effectiveness of new drugs and biologics. Control populations may include historical controls from published literature, patient registries, and/or contemporaneous external control groups. Continuous engagement among clinicians, industrial sponsors, and regulatory agencies to develop consensus on trial design and innovative development pathways for emergent and rare invasive fungal diseases is important.

Miltefosine: A Repurposing Drug against Mucorales Pathogens

Mucorales are a group of non-septated filamentous fungi widely distributed in nature, frequently associated with human infections, and are intrinsically resistant to many antifungal drugs. For these reasons, there is an urgent need to improve the clinical management of mucormycosis. Miltefosine, which is a phospholipid analogue of alkylphosphocholine, has been considered a promising repurposing drug to be used to treat fungal infections. In the present study, miltefosine displayed antifungal activity against a variety of Mucorales species, and it was also active against biofilms formed by these fungi. Treatment with miltefosine revealed modifications of cell wall components, neutral lipids, mitochondrial membrane potential, cell morphology, and the induction of oxidative stress. Treated Mucorales cells also presented an increased susceptibility to SDS. Purified ergosterol and glucosylceramide added to the culture medium increased miltefosine MIC, suggesting its interaction with fungal lipids. These data contribute to elucidating the effect of a promising drug repurposed to act against some relevant fungal pathogens that significantly impact public health.

Structural and Functional Alterations Caused by Aureobasidin A in Clinical Resistant Strains of Candida spp

Candida species are one of the most concerning causative agents of fungal infections in humans. The treatment of invasive Candida infections is based on the use of fluconazole, but the emergence of resistant isolates has been an increasing concern which has led to the study of alternative drugs with antifungal activity. Sphingolipids have been considered a promising target due to their roles in fungal growth and virulence. Inhibitors of the sphingolipid biosynthetic pathway have been described to display antifungal properties, such as myriocin and aureobasidin A, which are active against resistant Candida isolates. In the present study, aureobasidin A did not display antibiofilm activity nor synergism with amphotericin B, but its combination with fluconazole was effective against Candida biofilms and protected the host in an in vivo infection model. Alterations in treated cells revealed increased oxidative stress, reduced mitochondrial membrane potential and chitin content, as well as altered morphology, enhanced DNA leakage and a greater susceptibility to sodium dodecyl sulphate (SDS). In addition, it seems to inhibit the efflux pump CaCdr2p. All these data contribute to elucidating the role of aureobasidin A on fungal cells, especially evidencing its promising use in clinical resistant isolates of Candida species.

Miltefosine repositioning: A review of potential alternative antifungal therapy

Fungal infections are a global health problem with high mortality and morbidity rates. Available antifungal agents have high toxicity and pharmacodynamic and pharmacokinetic limitations. Moreover, the increased incidence of antifungal-resistant isolates and the emergence of intrinsically resistant species raise concerns about seeking alternatives for efficient antifungal therapy. In this context, we review literature data addressing the potential action of miltefosine (MFS), an anti-Leishmania and anticancer agent, as a repositioning drug for antifungal treatment. Here, we highlight the in vitro and in vivo data, MFS possible mechanisms of action, case reports, and nanocarrier-mediated MFS delivery, focusing on fungal infection therapy. Finally, many studies have demonstrated the promising antifungal action of MFS in vitro, but there is little or no data on antifungal activity in vertebrate animal models and clinical trials, so have a need to develop more research for the repositioning of MFS as an antifungal therapy.

Potential Inhibitory Effect of Miltefosine against Terbinafine-Resistant Trichophyton indotineae

Several prolonged and significant outbreaks of dermatophytosis caused by Trichophyton indotineae, a new emerging terbinafine-resistant species, have been ongoing in India in recent years, and have since spread to various countries outside Asia. Miltefosine, an alkylphosphocholine, is the most recently approved drug for the treatment of both visceral and cutaneous leishmaniasis. Miltefosine in vitro activity against terbinafine-resistant and susceptible T. mentagrophytes/T. interdigitale species complex, including T. indotineae, is limited. The current study aimed to assess miltefosine's in vitro activity against dermatophyte isolates, which are the most common causes of dermatophytosis. Miltefosine, terbinafine, butenafine, tolnaftate, and itraconazole susceptibility testing was performed using Clinical and Laboratory Standards Institute broth microdilution methods (CLSI M38-A3) against 40 terbinafine-resistant T. indotineae isolates and 40 terbinafine-susceptible T. mentagrophytes/T. interdigitale species complex isolates. Miltefosine had MIC ranges of 0.063-0.5 µg/mL and 0.125-0.25 µg/mL against both terbinafine-resistant and susceptible isolates. In terbinafine-resistant isolates, the MIC₅₀ and MIC₉₀ were 0.125 µg/mL and 0.25 µg/mL, respectively, and 0.25 µg/mL in susceptible isolates. Miltefosine had statistically significant differences in MIC results when compared to other antifungal agents (p-value 0.05) in terbinafine-resistant strains. Accordingly, the findings suggest that miltefosine has a potential activity for treating infections caused by terbinafine-resistant T. indotineae. However, further studies are needed to determine how well this in vitro activity translates into in vivo efficacy.

Antifungal activity of miltefosine against both azole-susceptible and -resistant Aspergillus strains

Miltefosine, an alkylphosphocholine, has been approved recently for the treatment of visceral leishmaniasis. Miltefosine has shown promise as a treatment for paracoccidioidomycosis, and has mixed activity against other fungi and yeast. There are limited data on the in-vitro activity of miltefosine against azole-resistant and -susceptible Aspergillus spp. As such, the aim of this study was to determine the in-vitro activity of miltefosine against Aspergillus strains. Miltefosine was tested against 108 azole-susceptible and -resistant Aspergillus strains isolated from Iran and other countries using the broth microdilution method. Miltefosine was found to be effective against azole-resistant Aspergillus isolates, with minimum inhibitory concentrations (MICs) ranging from 1.562 to 6.25 µg/mL. MIC₅₀ and MIC₉₀ were 1.562 and 3.125 µg/mL, respectively. Miltefosine had a higher geometric mean MIC (2.459 µg/mL) for wild-type Aspergillus isolates than itraconazole (0.220 µg/mL) and voriconazole (0.298 µg/mL). No significant difference was found between miltefosine MICs for azole-resistant Aspergillus isolates and azole-susceptible Aspergillus isolates (P>0.05). Miltefosine appears to have good in-vitro activity against azole-resistant Aspergillus strains, according to these findings. Furthermore, the findings suggest that miltefosine could be used to treat infections caused by azole-resistant Aspergillus spp.

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

Scedosporium and Lomentospora species are opportunistic filamentous fungi that cause localized and disseminated infections in immunocompetent and immunocompromised patients. These species are considered resistant fungi due to their low susceptibility to most current antifungal agents used in healthcare settings. The search for new compounds that could work as promising candidate antifungal drugs is an increasing field of interest. In this context, in the present study we screened the Pandemic Response Box® library (Medicines for Malaria Venture [MMV], Switzerland) to identify compounds with antifungal activity against Scedosporium and Lomentospora species. An initial screening of the drugs from this collection at 5 μM was performed using a clinical Scedosporium aurantiacum isolate according to the EUCAST protocol. Compounds with activity against this fungus were also tested against four other species (S. boydii¸ S. dehoogii, S. apiospermum and L. prolificans) at concentrations ranging from 0.078 to 10 μM. Seven compounds inhibited more than 80% of S. aurantiacum growth, three of them (alexidine, amorolfine and olorofim) were selected due to their differences in mechanism of action, especially when compared to drugs from the azole class. These compounds were more active against biofilm formation than against preformed biofilm in Scedosporium and Lomentospora species, except alexidine, which was able to decrease preformed biofilm about 50%. Analysis of the potential synergism of these compounds with voriconazole and caspofungin was performed by the checkerboard method for S. aurantiacum. The analysis by Bliss methodology revealed synergistic effects among selected drugs with caspofungin. When these drugs were combined with voriconazole, only alexidine and amorolfine showed a synergistic effect, whereas olorofim showed an antagonistic effect. Scanning electron microscopy revealed that alexidine induces morphology alterations in S. aurantiacum biofilm grown on a catheter surface. Reactive oxygen species production, mitochondrial activity and surface components were analyzed by fluorescent probes when S. aurantiacum was treated with selected drugs and revealed that some cell parameters are altered by these compounds. In conclusion, alexidine, amorolfine and olorofim were identified as promising compounds to be studied against scedosporiosis and lomentosporiosis.

Promising Antifungal Molecules against Mucormycosis Agents Identified from Pandemic Response Box®: In Vitro and In Silico Analyses

Mucormycosis is considered concerning invasive fungal infections due to its high mortality rates, difficult diagnosis and limited treatment approaches. Mucorales species are highly resistant to many antifungal agents and the search for alternatives is an urgent need. In the present study, a library with 400 compounds called the Pandemic Response Box^® was used and four compounds were identified: alexidine and three non-commercial molecules. These compounds showed anti-biofilm activity, as well as alterations in fungal morphology and cell wall and plasma membrane structure. They also induced oxidative stress and mitochondrial membrane depolarization. In silico analysis revealed promising pharmacological parameters. These results suggest that these four compounds are potent candidates to be considered in future studies for the development of new approaches to treat mucormycosis.

In Vitro Antifungal Susceptibility Profile of Miltefosine against a Collection of Azole and Echinocandins Resistant Fusarium Strains

Fusarium species are filamentous fungi that cause a variety of infections in humans. Because they are commonly resistant to many antifungal drugs currently available in clinical settings, research into alternative targets in fungal cells and therapeutic approaches is required. The antifungal activity of miltefosine and four comparators, amphotericin B, voriconazole, itraconazole, and caspofungin, were tested in vitro against a collection of susceptible and resistant clinical (n = 68) and environmental (n = 42) Fusarium isolates. Amphotericin B (0.8 μg/mL) had the lowest geometric mean (GM) MICs/MECs values followed by miltefosine (1.44 μg/mL), voriconazole (2.15 μg/mL), caspofungin (7.23 μg/mL), and itraconazole (14.19 μg/mL). Miltefosine was the most effective agent against Fusarium isolates after amphotericin B indicating that miltefosine has the potential to be studied as a novel treatment for Fusarium infections.

Sporothrix spp. Biofilms Impact in the Zoonotic Transmission Route: Feline Claws Associated Biofilms, Itraconazole Tolerance, and Potential Repurposing for Miltefosine

Sporotrichosis is the most prevalent subcutaneous mycosis globally, and it is typically caused by direct inoculation of the soil saprophytic fungus Sporothrix spp. into the patients’ skin. However, sporotrichosis has an important zoonotic transmission route between cats and humans in hot-spot endemic areas such as Brazil. Antifungal itraconazole is the first-line treatment; however, it is frequently associated with recurrence after withdrawal, mainly on cats. Biofilms are important resistance structures related to the environmental persistence of most microorganisms. In the present work, we evaluated Sporothrix yeasts’ ability to form biofilms in an ex vivo model of infected claws of cats. Using scanning electron microscopy, we demonstrated the presence of fungal biofilms in the claws of cats diagnosed with sporotrichosis confirmed by isolation of Sporothrix spp. in culture. We present here evidence of antibiofilm activity of miltefosine and suggest its use off-label as an antifungal as a putative alternative to itraconazole against Sporothrix biofilms. Claw contamination could sustain infections through a continuous inoculation cycle between open lesions and cat claws. Our results further support the off-label use of miltefosine as a promising alternative, especially for mycosis refractory to conventional treatment.