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Logo of nihpaAbout Author manuscriptsSubmit a manuscriptHHS Public Access; Author Manuscript; Accepted for publication in peer reviewed journal;
 
Curr Opin Investig Drugs. Author manuscript; available in PMC 2016 June 30.
Published in final edited form as:
Curr Opin Investig Drugs. 2005 August; 6(8): 845–853.
PMCID: PMC4928195
NIHMSID: NIHMS796639

SPK-843 Aparts/Kaken

Abstract

SPK-843 is a water-soluble antibiotic under co-development by Aparts and Kaken for the potential treatment of systemic fungal infections. By November 2004, SPK-843 was in phase II trials for systemic mycosis.

Graphical Abstract

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Introduction

Infections by fungi range from superficial conditions such as those of the skin and nails, to systemic illnesses. Superficial infections can be treated with topical antifungal drugs, but systemic infections involve organs and tissue and are often life-threatening. The majority of systemic mycoses are caused by Aspergillus fumigatus, Candida albicans, Cryptococcus neoformans, Fusarium sp, Histoplasma capsulatum and Pneumocystis carinii. During the past two decades, the prevalence of systemic mycoses has increased significantly as a result of several factors. The first of these is the increasing number of severely ill and immunocompromised patients with conditions such as azotemia, diabetes mellitus, bronchiectasis, emphysema, tuberculosis, lymphoma, leukemia or burns. These illnesses frequently result in a weakened immune system that leaves the patient susceptible to fungal invasion. The growing population of immunocompromised patients with HIV infection (despite the use of highly active antiretroviral therapy), chemotherapy-induced neutropenia or those receiving organ transplant-associated immunosuppressive therapy are also at heightened risk of infection. Immunocompromised patients include those with either immunodeficiency or those who are immunosuppressed. Immune suppression affects patients whose immune defences are impaired as a result of underlying diseases or management by cytotoxic, immunosuppressive agents or radiation therapy. HIV-infected patients are susceptible to mucosal candidiasis, cryptococcal meningitis, disseminated histoplasmosis and coccidioidomycosis. P carinii is a significant cause of mortality in HIV-infected patients. Invasive pulmonary Aspergillus contributes to mortality of bone marrow transplant recipients. A growing reason for systemic mycosis is attributed to exposure caused by the increased use of invasive medical procedures such as extensive surgery, and the use of prosthetic devices and vascular catheters. Other factors such as the use of broad-spectrum antibiotics or glucocorticosteroids, parenteral nutrition and peritoneal dialysis or hemodialysis, and an aging patient population also contribute to the increase in prevalence of systemic mycoses [201418], [359562], [440538], [586043].

At present the antifungal agents available for the treatment of life-threatening fungal infections are limited. The six major classes of systemic antifungal compounds used clinically are the polyenes, azoles, allylamines, thiocarbamate, morpholines and nucleoside analogs (reviewed in [586044]). The polyene antibiotics, azole derivatives, morpholine, allylamines and thiocarbamates target ergosterol and are ineffective against Pneumocystis carinii, which utilizes cholesterol instead of ergosterol. The polyene antibiotic forms a complex with ergosterol causing membrane disruption, increased permeability, leakage of cytoplasmic contents and cell death. The azoles inhibit biosynthesis of ergosterol at the C(14)-demethylation stage. Allylamine and thiocarbamate inhibit oxidosqualene causing depletion of ergosterol. The morpholines inhibit sterol Δ14 reductase and Δ78 isomerase in ergosterol biosynthesis and the nucleoside analogs inhibit DNA synthesis [201418]. The echinocandins are a new class of antifungal antibiotics, which inhibit glucan synthesis causing disruption of fungal cell walls. They are non-competitive inhibitors of the synthesis of 1,3-β-d-glucan, a major and essential component in the cell wall of many important fungal pathogens that is not present in mammalian cells. Caspofungin, a hexapeptide from this class, has been approved and launched [466492], [608829].

All of the drugs available for treatment of invasive fungal infections have advantages and disadvantages. Amphotericin B is still the most widely used drug for the treatment of fungal infections and for serious disseminated dimorphic fungal and yeast infections caused by Blastomyces, Candida, Cryptococcus and Histoplasma sp. Amphotericin B has been reported to cause nephrotoxicity, reduction of renal blood flow, nausea, vomiting and anorexia [586044]. Three lipid formulations of amphotericin B: amphotericin B lipid complex, amphotericin B cholesteryl sulfate and liposomal amphotericin B have been approved by the Food and Drugs Administration. These lipid formulations are less toxic and are favorable for safe application at higher doses. However, lipid formulations are ineffective for treating amphotericin-resistant isolates and are expensive [384559]. Nystatin is too toxic to be used systemically but is used in cases of mucous membrane candidiasis. Griseofulvin is used for the treatment of certain dermatophyte infections caused by Epidermophyton, Microsporum and Trichophyton sp but can cause hepatotoxicity and gastrointestinal distress [586044]. Fluorocytosine (Kolon Industries Inc) is a pyrimidine antifungal drug that interferes with DNA synthesis, however, it has a limited spectrum of activity and significant toxicity, including skin rash, nausea, vomiting, diarrhea, bone-marrow toxicity, leucopenia, liver enzyme elevation and rapid development of resistance to fungal pathogens. Azole antifungal agents represent a major advance in the treatment of systemic fungal infections. Ketoconazole, itraconazole and fluconazole are frequently used as alternatives to amphotericin B. Azoles have some advantages such as broad spectrum activity, ease of administration, high bioavailability, high water solubility, low degree of protein binding, wide volume of distribution into body tissue and fluids, and a long half-life. The major disadvantage of azoles is the frequent incidence of toxicity, including hepatic necrosis and abdominal cramping. As a result, they are mainly used topically in the treatment of candidiasis, coccidian meningitis, cutaneous dermatophytes and histoplasmosis. In addition, these drugs are known to interact with a large number of pharmaceuticals and result in hepatotoxicity. Another potential limitation of azoles is the emergence of Candida sp resistant to fluconazole [608835]. Caspofungin has demonstrated activity against Aspergillus sp and Candida sp and is well tolerated, however, it has common side effects, including fever, phlebitis, headache and rash [466492]. Limitations of these available antifungal antibiotics all drive the search for novel and safe broad-spectrum antifungal antibiotics [586044], [586046].

One such novel compound is SPK-843, a water-soluble polyene antibiotic derived from partricin A [586050]. This drug has a broad-spectrum of antifungal activity comparable to that of amphotericin B, but is less toxic. SPK-843 is being developed by Aparts (formerly Societa Prodotti Antibiotici SpA) and Kaken and is undergoing phase II clinical trials for the potential treatment of systemic fungal infections [5718847], [612404].

Synthesis and SAR

SPK-843 (N-dimethylaminoacetylpartricin A 2-dimethylaminoethylamide diascorbate salt) is a derivate of partricin A [586050]. Partricins are polyene antibiotics isolated from the Streptomyces aerofaciens strain NRRL3878 as a mixture of partricin A, B and C. Separation of the three partricins was conducted by countercurrent distribution [610557]. Fermentation of a novel mutant strain, S aureofaciens, yielded partricin A largely free from partricin B. Partricin A demonstrated potent antifungal activity, particularly against Candida albicans, and antiprotozoal activity but has limited utility in the clinic due to its toxicity. In order to improve the chemical and biological properties, amide derivatives of partricin A were prepared. The new amides were converted to diamide derivatives by substitution with an amino group at the carboxy position of partricin A and substitution with acyl groups at the amino group of mycosamine. Both the amino and the acyl substituent carry a basic group, which is in agreement with structure-activity relationship data reported for a few derivatives of amphotericin B and nystatin. Basic substituents are generally useful for preparation of aqueous soluble salts for injectable formulations. Substitution of secondary and tertiary amides of partricin A with lower alkyl groups generated analogs that had greater antifungal efficacy in vitro than amphotericin B. However, the toxicity of these analogs remained high and they were poorly water-soluble, posing problems for generating injectable formulations. The antifungal activity of the basic amide analogs were even more potent. Moreover, salts of these amide analogs were water soluble but the toxicity of these compounds remained similar to that of amphotericin B. Basic diamides were less potent than most other derivatives produced in this study, but they maintained a higher antifungal activity than amphotericin B and could be converted to hydrosoluble salts [586050].

Partricin A 2-dimethylaminoethyl amide (SPA-S-710) and N-dimethylamino acetyl-partricin A 2-dimethylaminoethyl amide (SPA-S-752) were selected for further development due to high potency and tolerability. SPA-S-752 can be made soluble in the form of the diaspartate (SPA-S-753) or the diascorbate salt (SPK-843) [586050].

SPK-843 is a heptaene polyene antibiotic. Polyene antibiotics are characterized by the presence of a series of conjugated double bonds that are essential for antifungal activity and contribute to the photo-instability and water insolubility of the drugs. Irradiation (with ultraviolet light at 365 nm) of SPK-843 in methanol-aqueous solution yields the E isomer (with all conjugated double bond in the trans configuration). The isomer has the same activity as SPK-843 against yeast but lower activity against mold and protozoa. In order to determine the best conditions for SPK-843, the photostability of SPK-843 in solution was evaluated using different light sources, intensities and exposure times. The data revealed the degradation effect of violet and ultraviolet radiations. The light emitted by red varnished wire lamps was much less damaging than the light of standard wire, neon and sodium lamps. The photodegradation can be reduced by lowering the light emission in the violet and ultraviolet region [291454].

Insolubility of polyene in water causes difficulties for administration by systemic routes. Complexes, colloidal dispersions or liposomal formulations are used for injectable formulation. Studies demonstrated that Intralipid 10% emulsion containing SPK-843 (0.1 to 0.5 mg/ml) at mildly acid or basic pH was physically stable. SPK-843 solution in an Intralipid 10% emulsion, at natural and mildly basic pH, was chemically stable for 2 h at 25°C even in a well-lit room. The opacity of the emulsion most likely protects SPK-843 from light [440552].

Preclinical Development

The in vitro potency and antifungal activity of SPK-843 was examined against clinical isolates. Senda et al reported the activity of SPK-843 against clinical isolates of Candida sp, C neoformans and Aspergillus sp (n = 107, 12 and 31, respectively). SPK-843 is highly effective against Candida sp, C neoformans and Aspergillus sp, with comparable or superior activity to that of amphotericin B. A comparison of in vitro activity is shown in Table 1. At concentrations between 0.125 and 2 µg/ml, SPK-843 was able to eliminate viable C albicans and C neoformans cells to below detectable levels within 1 h, and more rapidly than an equivalent concentration of amphotericin B [382488].

Table 1
In vitro activity of SPK-843 against clinical yeast isolates.

Kantarcioglu et al reported further data on the activity of SPK-843 against clinical isolates of C albicans, non-albicans Candida, C neoformans and Aspergillus sp (n = 70, 39, 49 and 36, respectively). The MIC range (µg/ml) of SPK-843 for C albicans, non-albicans Candida, C neoformans and Aspergillus sp were 0.007 to 4, 0.007 to 8, 0.007 to 4 and 0.007 to > 16, respectively. Amphotericin B MIC (µg/ml) values ranged from 0.015 to 16 for C albicans, 0.03 to 16 for non-albicans Candida, 0.03 to 2 for C neoformans and 0.06 to > 16 for Aspergillus sp. MIC and minimum fungicidal concentration (MFC) values are shown in Table 2. The MFC of SPK-843 (µg/ml) ranged from 0.03 to 16 for C albicans, 0.03 to 16 for non-albicans Candida, 0.03 to 8 for C neoformans and 0.007 to > 16 for Aspergillus sp. Amphotericin MFC ranged from 0.125 to 16, 0.25 to 16, 0.03 to 8 and 0.06 to > 16 µg/ml, respectively. [489355], [571210].

Table 2
MIC and MFC values of SPK-843 against Candida sp, C neoformans and Aspergillus sp clinical isolates.

The in vitro activity of SPK-843 was tested against a range of yeast, including C albicans (n = 48), C glabrata (n = 11), C krusei (n = 10), C parapsilosis (n = 4), C tropicalis (n = 12), C neoformans (n = 21) and Saccharomyces cerevisiae (n = 10). The MIC range, MIC50, MIC90 and geometric mean MIC values (µg/ml) of SPK-843 and amphotericin B are shown in Table 3. SPK-843 had lower MIC values than amphotericin B against S cerevisiae, C tropicalis, C neoformans and C glabrata. The range of MFC99 values and geometric means (µg/ml) are shown in Table 4. SPK-843 had greatest activity against C krusei, C tropicalis and C albicans. This study demonstrated that SPK-843 has better inhibitory activity against all yeast and better fungicidal activity against C albicans, C glabrata, C krusei and C tropicalis [308269].

Table 3
MIC values of SPK-843 and amphotericin B against a range of yeast.
Table 4
MFC values of SPK-843 and amphotericin B against a range of yeast.

The in vitro activity of SPK-843 against filamentous fungi demonstrated that the in vitro inhibitory activity of SPK-843 against Aspergillus sp was superior to that of amphotericin B, while the activity against Rhizopus oryzae, Paecilomyces variotti, Penicillium sp and Sporothrix schenkii were similar. The MFC values were 12.53, 12 and 19.2 µg/ml, respectively, against Aspergillus sp, Penicillium sp and S schenkii [374266].

The anticandidal activity of SPK-843 was reported to be higher than amphotericin B against C albicans in culture and in contact tests. The activity of SPK-843 was influenced by pH and electrical conductivity. SPK-843 killed C albicans in 3 min in contact tests. The highest activity was achieved in a medium with low electrical conductivity (0.001 M buffer strength) and with acidic pH (pH 5.8), which induced cell permeability. The activity of SPK-843 was related to the induction of greater cellular damage following increased leakage of K+ ions. Treatment of C albicans with SPK-843 induced a significantly greater leakage of K+ ions over a 4 min test (80%) than amphotericin B (35%) [358056]. In another study in yeasts, filamentous fungi and protozoa, contact tests with SPK-843 (10 and 100 mg/l) were undertaken directly on cell suspensions and on colony forming units after 48-h incubation at 37°C. Killing times were reported as a measure of cytocidal activity. The killing times were 3 to 10 min for Candida sp, with a complete release of K+ ions detected within 3 min at 10-mg/l of SPK-843. Killing times against filamentous fungi were 15 to 30 min, and for all protozoa tested were within 10 min (0.03 mg/l of SPK-843) [417871].

Clinical potency of SPK-843 for candidiasis and aspergillosis is promising compared with amphotericin B deoxycholate (D-AMPH) and liposomal amphotericin B (AmBisome). In a murine model of systemic candidiasis, CD-1 mice were inoculated intravenously with C albicans. Intravenous therapy was initiated 1 h after infection and was administered daily, one, three or five times (on days 1, 3 and 5). By the fifth treatment, the activity of SPK-843 was 2-fold higher than D-AMPH at doses of 0.2 to 0.4 mg/kg/day. After five doses of 0.8 mg/kg, SPK-843 completely eradicated the pathogen in eight out of ten mice, whereas the same dose of D-AMPH had no effect. In a murine model of pulmonary aspergillosis, DBA/2N mice pretreated with triamcinolon acetonide were challenged by an aerosol of conidial Aspergillus and then administered five daily treatments. In pulmonary aspergillosis caused by A fumigatus, SPK-843 significantly and dose-dependently prolonged survival at doses of ≥ 1 mg/kg/day. During further studies, SPK-843 (2 mg/kg/day) had a greater effect than D-AMPH (1 or 2 mg/kg/day) and AmBisome (8 mg/kg/day). In addition SPK-843 demonstrated good therapeutic effect against A flavus and A niger compared with D-AMPH [382489].

In a murine model of cerebral cryptococcosis, female CD-1 mice aged 6 to 8 weeks were infected with 105 C neoformans ATCC 11240 cells/mouse. Different doses (0.1, 0.3, 1, 3, 6 mg/kg) of SPA-S-753 (the diaspartate analog of SPK-843; Aparts BV) or amphotericin B were administered intraperitoneally, 1 h post-challenge and daily for 4 days. SPA-S-753 and amphotericin B enhanced the median survival time of infected mice in a dose-dependent manner. The median survival times for SPA-S-753 were 27, 27, 41, 50 and > 60 days at doses of 0.1, 0.3, 1, 3, 6 mg/kg, respectively. The median survival times for amphotericin B at the same doses were 24, 26, 45, 47 and 51 days, respectively. When treatment was expanded to 9 days post-infection, both SPA-S-753 and amphotericin B, at 6 mg/kg, were able to protect 100% of mice [374274]. In a related study involving a C neoformans model, 8-week-old male BALB/c mice were infected intravenously with approximately 5 × 105 C neoformans YC-11 cells and were treated intravenously with SPK-843 (0.5 and 1.0 mg/kg), amphotericin B (1.0 mg/kg) or fluconazole (10 mg/kg) once daily for 3 days. All control mice died within 12 to 20 days but administration of the drugs prolonged the survival of infected mice. SPK-843, at a dose of 1.0 mg/kg, prolonged survival longer than the 0.5 mg/kg dose [568942].

The eradicative efficacy of SPK-843 was evaluated in CD-1 mice (n = 8) infected intravenously with 5 × 106 C albicans KSG-27 cells, and treated with daily intravenous amphotericin B, micafungin or voriconazole. In time-killing studies, (conducted without serum) SPK-843 (0.125 µg/ml) reduced viable C albicans more rapidly than the equivalent or higher concentrations of amphotericin B and micafungin. When this test was conducted in the presence of human serum (50 to 100%), the fungicidal activity of SPK-843 was maintained at 0.5 µg/ml. In the candidiasis model, SPK-843 (0.25 mg/kg) reduced the viable Candida cell count in the kidney to < 1/100 of control levels. Higher concentrations of the other tested drugs were required to achieve the same activity: 1 mg/kg of amphotericin B, 4 mg/kg of micafungin and 16 mg/kg of voriconazole. SPK-843 (0.25 mg/kg) eradicated fungi by day 4 in 50 to 100% of mice, whereas 1 mg/kg of amphotericin B was required. Micafungin and voriconazole did not show any activity at 4 and 16 mg/kg, respectively [568943].

The efficacy of SPK-843 in pulmonary aspergillosis was evaluated and compared to amphotericin B and micafungin. Male, 6-week-old DBA/2N mice were injected with 10 ml of conidial suspension of A fumigatus MF-13 at concentrations of 5 × 106 cells/ml. Mice were treated once daily from days 1 to 5 with SPK-843 B (0.25, 0.5, 1.0 and 2.0 mg/kg iv) or amphotericin B (0.25, 0.5, 1.0 and 2.0 mg/kg iv) or micafungin (2.0, 4.0 and 8.0 mg/kg iv). All antifungal agents prolonged survival; the greatest efficacy with SPK-843 was achieved following a 2.0-mg/kg dose [568944].

Metabolism and Pharmacokinetics

The pharmacokinetic properties of intravenously administered SPA-S-753 were studied in rats (1.25, 2.5 and 5 mg/kg) and mice (1.25 and 2.5 mg/kg), with amphotericin B (1 mg/kg) as a reference drug. Blood samples were obtained 5 min to 96 h after injection. In rats, the mean population half-lives at the elimination phase in serum were approximately 21, 27 and 39 h and the mean AUC values were 33, 53, 84 µg.h/ml at 1.25, 2.5 and 5 mg/kg, respectively. In mice, the mean half-lives were 11 and 14 h while the mean AUC0-∞ values were 41 and 85 µg.h/ml at doses of 1.25 and 2.5 mg/kg, respectively. For comparison, the half-life of amphotericin B was 10.8 h in rats and 19.8 h in mice, and the AUC0-∞ was 23.6 µg.h/ml in mice. The AUC0-∞ for SPA-S-753 was 2-fold higher in mice, but 5-fold higher in rats. The mean cumulative urinary recovery of SPA-S-753 in rats 48 h after intravenous injection of 1.25 mg/kg accounted only for 0.5% of the dose, while the cumulative recovery from bile at 10 h after administration of 2.5 mg/kg accounted for 5.5% of the dose [170283], [374244], [608844]. The concentration of SPA-S-753 was lower than amphotericin B in the liver, lung and kidney [608844]. Single oral doses of SPA-S-753 (200 or 500 mg/kg) were poorly absorbed in rats [374244].

A pharmacokinetic study of a single intravenous dose of SPK-843 (1.25 mg/kg; equivalent to 1 mg/kg of free-base drug) was also conducted in rats, and compared to a single intravenous dose of amphotericin B (1 mg/kg). The elimination half-lives for SPK-843 and amphotericin B were 22.15 and 18.15 h, respectively, and AUC0-∞ values were 35.52 and 10.33 µg.h/ml, respectively. SPK-843 demonstrated extensive tissue distribution, with highest uptake to the kidneys, followed by the liver, spleen and lungs. The multiple-dose administration study was also conducted with SPK-843 (1.25 mg/kg/day), administered for 7 days. On the seventh day, the rats were bled at intervals from 5 min to 96 h after dosing. The serum elimination half-life for SPK-843 was 41.4 h and AUC0-∞ was 72.1 µg.h/ml [440534].

The pharmacokinetics and tissue distribution properties of single intravenous doses of three preparations of SPK-843 (1.25 mg/kg) were compared in rats. The dosage forms of the antibiotic were a 5% glucose solution, a 10% lipid emulsion at pH 5.3, and a 10% lipid emulsion at pH 7.5. The half-lives were comparable for these formulations (22.2, 26.5 and 23.2 h, respectively) and AUC values were 35.5, 40 and 44.8 µg.h/ml, respectively, indicating the influence of lipid solvents and pH [440546].

The pharmacokinetics of single doses of SPK-843 (0.0625, 0.125, 0.25 and 0.5 mg/kg) were investigated in healthy Japanese males (n = 6). Each dose group contained eight patients, two of which received placebo. SPK-843 dissolved in 10% lipid was administered to fasted patients as a 1 h continuous infusion. The plasma pharmacokinetic parameters are shown in Table 5. A linear dose response was obtained in both blood and plasma. SPK-843 was renally excreted (> 90%), with < 1% of the administered dose excreted unchanged in the urine after 120 h [503618].

Table 5
Pharmacokinetic parameters of single-dose SPK-843.

In another randomized phase I study, multiple intravenous doses of SPK-843 (0.0625, 0.125 or 0.25 mg/kg) were examined in Japanese male individuals (n = 8). Drug was administered as a constant rate intravenous infusion over 1 h, once daily for 14 days. The Cmax of blood increased with dose, but plasma Cmax was saturated at high doses after repeated administration because of transition to blood cells. Blood Cmax values were 0.647, 1.180 and 2.030 µg/ml in the respective dose groups, and plasma Cmax values were 0.888, 1.185 and 1.250 µg/ml, respectively [567762], [568890].

Toxicity

The toxicity of SPK-843 was compared to amphotericin B and micafungin. Cell toxicity tests were conducted using human embryonic lung fibroblast cells. The cells were preincubated at 37°C under 5% CO2 for 1 day in Eagle's Minimal Essential medium with 1% fetal calf serum and followed by incubation with each drug at final concentrations of 0.125, 0.25, 0.5, 1 or 2 µg/ml. Leakage of lactose dehydrogenase (LDH) to culture fluid was measured at 4 or 24 h after drug addition. LDH leakage due to SPK-843 and amphotericin B was dose dependent. In cells treated with SPK-843, acceleration of LDH leakage occurred 4 h after drug addition, while amphotericin B caused LDH leakage immediately after drug addition. Both SPK-843 and amphotericin B at a dose of 1 µg/ml did not show any effect on LDH leakage. Micafungin caused LDH leakage at 32 µg/ml [568943].

Venous toxicity trials were conducted in rabbits. SPK-843 was repeatedly perfused in the marginal ear vein for 30 min, at intervals of ≥ 24 h. SPK-843 dissolved in 10% emulsion was better tolerated than when dissolved in ordinary 5% glucose solution (p < 0.05). Increasing the pH to 8 increased venous toxicity compared with pH 7.5 (p < 0.05) and pH 5.3 (p < 0.1) [440552].

Histopathological examination of the kidney was conducted to observe nephrotoxicity due to SPK-843. Mice were treated with amphotericin B and SPK-843 for 5 days and then sacrificed on day 7. No significant histopathological lesions were found following treatment with SPK-843 (1.0 or 4.0 mg/kg/day) while kidney damage was observed following administration of 1 mg/kg of amphotericin B [568944].

Clinical Development

Phase I

As described, two phase I clinical trials were conducted in healthy Japanese males, one with a single intravenous dose of SPK-843 (0.0625, 0.125, 0.25 or 0.5 mg/kg; eight individuals per dose group) [503618], and the other with multiple intravenous doses of SPK-843 (0.0625, 0.125 or 0.25 mg/kg/day for 14 days; eight individuals per dose group) [567762], [568890].

Phase II

SPK-843 entered phase II clinical trials for systemic mycosis in November 2004 [571884]. However, data from this trial were not available at the time of publication.

Side Effects and Contraindications

The most common side effects observed during phase I studies were transiently mild albuminuria and glucosuria. The severity of albuminuria was dose related but glucosuria was detected at only > 0.25 mg/kg. No decrease in creatinine clearance was observed. All adverse effects were resolved without treatment, even following multiple doses [503618], [567762], [568890].

Patent Summary

A number of published patents and applications make claims surrounding SPK-843 and related polyene macrolide antibiotic derivatives, all of which feature the named inventor Bruzzese Tiberio, a researcher at Societa Prodotti Antibiotici. The earliest of these, EP-00434943, was published by Societa Prodotti Antibiotici in July 1991. A novel series of secondary and tertiary amide derivatives of partricin are claimed as antifungal and antiprotozoal agents with less toxicity than the parent compound; in vitro data are provided for 16 compounds. Further partricin derivatives were claimed in the June 1992 application EP-00489308, which have an acylated mycosamine primary amino group. SPK-843 is a specifically claimed compound, and synthetic routes for 18 compounds are described.

Novel fungicidal complexes comprising SPA-S-753 (the specified compound, or analogs) and cholesterol-3-sulfate were disclosed by Societa Prodotti Antibiotici SpA in the January 1998 application WO-09802168. These compounds are claimed to be useful for the treatment of systemic mycotic infections, particularly in patients with cancer or AIDS, for simple and reduced-toxicity administration in both hospital and home. Antifungal agents for the curative treatment of cell cultures and tissues were further claimed in US-05914321 (June 1999) and EP-01013289 (June 2000). WO-09966902, published in December 1999 by the individual inventors Bruzzese Tiberio and Ferrari Valerio Maria, claimed novel injectable formulations of SPK-843. Most recently, WO-2005053677 (June 2005) claimed reduced toxicity formulations comprising a partricin derivative, preferably SPK-843, for the oral treatment of fungal and/or protozoal, oral or intestinal infections.

Current Opinion

To date, only amphotericin B from the polyene class of antifungal antibiotics has been approved for systemic fungal infections. Due to the broad-spectrum of activity and the low frequency of resistant pathogens, polyene antibiotics are being investigated as potential new antifungal agents. An ideal antifungal antibiotic should be selective, effective and safe. Selecting a target is important in order to determine the selectivity and toxicity of potential antifungal candidates. The target of the polyenes is ergosterol, meaning they are selective inhibitors since mammalian cells do not utilize this sterol. The affinity of polyenes to ergosterol causes disruption of fungal cell membranes. As a polyene, SPK-843 induces cellular damage causing the leakage of K+ ions, which leads to fungal cell death. There is no published report comparing the affinity of SPK-843 to ergosterol and cholesterol, however, these data are important because of the possibility that the toxicity of polyenes may be related to its affinity to cholesterol in mammalian cells.

SPK-843 has demonstrated activity against fungi in preclinical studies both in vitro and in vivo. SPK-843 possesses broad-spectrum antifungal activity against yeast, dimorphic fungi and filamentous fungi. SPK-843 possesses a more rapid fungicidal action than amphotericin B or micafungin. The eradicative efficacies of SPK-843 in candidiasis were superior compared with amphotericin B, micafungin and voriconazole. No significant lesions in the kidney were observed compared with amphotericin B during the pathological study, which at a dose of 1 mg/kg produced renal impairment in mice. SPK-843 was well tolerated in studies to date, with only minor side effects reported. Furthermore, the ability of SPK-843 to kill fungi more rapidly than current standard treatments offers advantage for the treatment of acute infections. In comparison with amphotericin B, SPK-843 offers several advantages and may fulfill substantial requirements for an effective, more selective and safe antifungal antibiotic.

The efficacy of an antimicrobial agent is determined by complex interactions between the administered drug, the host and the infecting agent. SPK-843 interferes with the infecting agent without any impact on the host. However, in a clinical situation, the interaction of drug, host and an infecting agent leads to high variability in the dose-response relationship. Data regarding dose-response variability should be collected in future clinical trials. However, based on preclinical and phase I data, SPK-843 appears to be a highly promising antifungal candidate. If the drug achieves similar success in phase II and III studies, SPK-843 may fulfill the medical and market requirements for better and safer antifungal agents.

Appendix A

Licensing

Aparts BV

By July 2005, Aparts had acquired worldwide rights, except in Japan and the Far East, of SPK-843 from the Societa Prodotti Antibiotici. [612404], [612421].

Kaken Pharmaceutical Co Ltd

By 1996, Kaken had licensed SPK-843 in Japan and the Far East [223847].

Development history

SPK-843 belongs to the same research program as SPA-S-753, but was selected as the lead compound as a result of its increased chemical stability in vitro [359931].

DeveloperCountryStatusIndicationDateReference
Kaken Pharmaceutical Co LtdJapanPhase IIFungal infection19-NOV-04571884
Aparts BVNetherlandsPhase IFungal infection14-JUN-05612404
SPA Societa Prodotti Antibiotici SpAItalyDiscontinuedFungal infection13-JUL-05612421
SPA Societa Prodotti Antibiotici SpAGermanyDiscontinuedFungal infection13-JUL-05612421

Literature classifications

Chemistry

Study TypeResultReference
Synthesis.Partricin A was modified to generate analogs. Most of the amide derivates were more potent
antifungals, less toxic and produced less hemolysis than amphotericin B. Two analogs were selected for
further development, SPA-S-710 and SPA-S 752. SPA-S-753 is the diaspartate salt of SPA-S-752 and
SPK-843 is the diascorbate salt.
586047
Photostability.Light induced the formation of the E isomer. Violet and ultraviolet radiation yielded damaging effects.
The light emitted by red varnished wire lamps was much less damaging than the light of usual wire,
neon and sodium lamps. Lowering the light emission in the violet and ultraviolet regions reduced
photodegradation.
291454
Stability.Intralipid 10% emulsion containing SPK-843 (0.1 to 0.5 mg/ml) at mildly acid or basic pH was physically
stable. SPK-843 in Intralipid 10% emulsion, at natural and mildly basic pH, was chemically stable for 2 h
at 25°C even in a well-lit room.
440552

Biology

Study TypeEffect StudiedExperimental ModelResultReference
In vitroActivity.Susceptibility testing by
the macro dilution
reference method of the
National Center for
Clinical Laboratory
Standards (NCCLS).
In vitro inhibitory activity of SPA-S-843 against
Aspergillus sp was superior than that of amphotericin
B. While the activity against R oryzae, P variotti,
Penicillium sp and S schenkii were similar. The MFC
values were 12.53, 12.00 and 19.20 µg/ml against
Aspergillus sp, Penicillium sp and S schenkii,
respectively.
374266
In vitroActivity.Broth and agar
microdilution by the
NCCLS.
SPK-843 had significantly lower MIC values than
amphotericin B against S cerevisae, C tropicalis, C
neoformans and C glabrata. SPK-843 was most
fungicidal against C krusei, C tropicalis and C
albicans.
308269
In vitroActivity.Contact test and germ
tube inhibition test.
SPK-843 killed C albicans in 3 min. The best fungicidal
activity occurred in a medium with low electrical
conductivity (0.001 M buffer strength) and pH 5.8. The
activity of SPK-843 is associated with the induction of
greater cellular damage following increasing leakage
of K+. SPK-843 produced 80% leakage in 4 min, while
amphotericin B produced 35% in the same time.
358056
In vivoActivity.CD-1 mice intravenously
infected with C albicans.
The activity of SPK-843 was 2-fold higher than
D-AMPH at doses of 0.2 to 0.4 mg/kg/day for 5 days.
At 0.8 mg/kg/day for 5 days, SPK-843 completely
eradicated C albicans in eight out of ten mice, whereas
the same dose of D-AMPH had no effect.
382489
In vivoEfficacy.CD-1 mice infected with
5 × 106 C albicans
KSG-27 cells.
SPK-843 (0.25 mg/kg) reduced viable C albicans cell
count in the kidney to less than 1/100 of control on day
1. At the same dose, SPK-843 eradicated fungi by day
4 from 50 to 100% of mice, whereas amphotericin B
required a dose of 1 mg/kg to reach these eradication
levels.
568943

Metabolism

Study TypeEffect StudiedModel UsedResultReference
In vivoPharmacokinetics.SPA-S-753
intravenously
administered to rats
(1.25, 2.5 and 5 mg/kg)
and mice (1.25 and 2.5
mg/kg).
In rats, the half-lives were approximately 21, 27, 39 h
and the mean AUC values were 33, 53, 84 µg.h/ml,
respectively. In mice, mean half-lives were 11 and 14
h, respectively. Compared with amphotericin B (1
mg/kg) the AUC0−∞ for SPA-S-753 was 2-fold higher
in mice and 5-fold higher in rats.
374244
In vivoPharmacokinetics.Rats intravenously
injected with SPK-843
(1.25 mg/kg) as single
and multiple
administrations (7 days).
The half-life of SPK-843 was 22.15 h and AUC0−∞
was 35.52 µg.h/ml after a single administration. In
multiple administrations the half-life was 41.4 h and
the AUC0−∞ was 72.1 µg.h/ml.
440534
In vivoPharmacokinetics.Rats injected with three
single dosage forms of
SPK-843 (1.25 mg/kg in
5% glucose solution,
10% lipid emulsion at
pH 5.3 and 10% lipid
emulsion at pH 7.5).
The half-lives of SPK-843 were 22.2 h in 5%
glucose, 26.5 h in 10% lipid emulsion pH 5.3 and
23.2 h in lipid emulsion at pH 7.5. The AUC values
were 35.5 µg.h/ml in 5% glucose, 40 µg.h/ml in 10%
lipid emulsion pH 5.3 and 44.8 µg.h/ml in lipid
emulsion at pH 7.5.
440546
In vivoPharmacokinetics.Phase I trial in healthy
Japanese male
individuals administered
SPK-843 (0.0625, 0.125
or 0.25 mg/kg iv) as a
1 h infusion every day
for 14 days.
Blood Cmax values were 0.647, 1.180 and 2.030
µg/ml, respectively, and plasma Cmax values were
0.888, 1.185 and 1.250 µg/ml, respectively.
568890

Clinical

Effect StudiedModel UsedResultReference
Safety and tolerability.Phase I trial in healthy
Japanese males
administered a single dose
of SPK-843 (0.0625, 0.125,
0.25 or 0.5 mg/kg).
The main side effects were transiently mild albuminuria
and glucosuria. SPK-843 up to 0.5 mg/kg was well-
tolerated in Japanese individuals and demonstrated
linear kinetics.
503618
Safety and tolerability.Phase I trial in healthy
Japanese male individuals
administered intravenous
SPK-843 (0.0625, 0.125 or
0.25 mg/kg) as a 1 h infusion
every day for 14 days.
The severity of albuminuria was dose related but
glucosuria was detected only at > 0.25 mg/kg. No
decrease in creatinine clearance was observed. All
adverse effects were resolved without treatment. The
administration of SPK-843 up to 0.25 mg/kg for 14 days
was safe and well tolerated.
568890

Associated patent

Title Use of partricin derivatives for treating fungal and protozoal infections.

Assignee Individual

Publication WO-2005053677 16-JUN-05

Priority IT-2003MI02280 24-NOV-03

Inventors Bruzzese T.

Associated references

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