SCH-39304 in prevention and treatment of disseminated candidiasis in persistently granulocytopenic rabbits

Hydroxysulfonylation of alkenes: an update

The direct difunctionalization of inexpensive and widely available alkenes has been recognized as a strong and straightforward tool for the rapid fabrication of complex molecules and pharmaceutical targets by introducing two different functional groups on adjacent carbon atoms of common alkene moieties in a single operation. This synthetic strategy avoids the purification and isolation of the intermediates and thus makes synthetic schemes shorter, simpler and cleaner. In this family of reactions, the hydroxysulfonylation of alkenes has emerged as an increasingly promising strategy for the synthesis of β-hydroxysulfones, which are found in many biologically important molecules and widespread applications in organic synthesis. The objective of this review is to illustrate the advancements in the field of hydroxysulfonylation of alkenes with special emphasis on the mechanistic details of the reaction pathways.

The direct difunctionalization of alkenes recognized as a straightforward tool for the rapid fabrication of complex molecules and pharmaceutical targets by introducing two different functional groups on adjacent carbon atoms of common alkene moieties.

Pharmacokinetics of the active antifungal enantiomer, SCH 42427 (RR), and evaluation of its chiral inversion in animals following its oral administration and the oral administration of its racemate genaconazole (RR/SS)

Genaconazole (SCH 39304) is a potent triazole antifungal agent that is active both orally and topically. Genaconazole is a racemic mixture which contains 50% of the RR (SCH 42427) and 50% of the SS (SCH 42426) enantiomers. The RR isomer accounts for most of the antifungal activity of genaconazole. Serum concentrations of the RR and SS enantiomers were analyzed by a chiral HPLC method which involved extraction of serum with organic solvent followed by separation on a Cyclobond I column and quantification by UV absorbance at 205 nm. The bioavailability and pharmacokinetic profiles of the two enantiomers after oral administration of the racemate (genaconazole) were very similar in cynomolgus monkeys. In rats following dosing with genaconazole, the RR enantiomer had a lower C(max) and a longer t(1/2) than the SS enantiomer, while the AUC(I) values of the two enantiomers were similar. Based on chiral HPLC analysis, there was no evidence for the inversion of the RR to the SR isomer, or of the SS to the SR isomer, indicating that there was no chiral inversion of the RR or SS enantiomers in either species. Genaconazole at 20 mg/kg and the RR (SCH 42427) enantiomer at 10 mg/kg had very similar serum concentration-time profiles and C(max), AUC(I), and t(1/2) values for the RR enantiomer in both rats and monkeys, indicating that the two treatments were equivalent with respect to the bioavailability of the RR enantiomer.

Pharmacokinetics of the triazole antifungal agent genaconazole in healthy men after oral and intravenous administration

The pharmacokinetics of genaconazole, a potent new difluorophenyl-triazole antifungal agent, was studied in 12 healthy male volunteers following a single oral or intravenous administration of the drug. In a randomized two-way crossover design, each volunteer received either two 50-mg genaconazole tablets orally or a parenteral preparation containing 100 mg of genaconazole given as a 30-min intravenous infusion. Both dosage regimens were well tolerated. Blood and urine samples were collected up to 10 days after drug administration. Concentrations of genaconazole in plasma and urine were determined by a specific high-performance liquid chromatography assay with a limit of quantitation of 0.1 microgram/ml. Pharmacokinetic evaluation following oral and intravenous doses indicated that mean values for the area under the concentration-time curve from 0 h to infinity (137 and 136 micrograms.h/ml), half-life (50 and 49 h), volume of distribution (52 and 52 liters), and clearance (12 and 12 ml/min) were independent of the route of drug administration. The oral and intravenous administrations of genaconazole yielded virtually superimposable plasma concentration-time curves, resulting in an absolute bioavailability of 100%. Amounts of unchanged genaconazole found in urine samples from 0 to 240 h after oral and intravenous doses were comparable, and urinary excretion accounted for 76 and 78% of the administered dose, respectively. Renal clearances for the two routes of administration were also similar, and renal clearance accounted for over 80% of the total body clearance. The 100% absolute bioavailability of genaconazole regardless of the route of administration provides greater dosing flexibility in various clinical settings than currently exists.

Treatment of coccidioidomycosis with SCH 39304

A new oral triazole antifungal, SCH 39304, was administered to 54 patients with progressive infections due to Coccidioides immitis from six collaborating centers. Patients were grouped according to site of infection including chronic pulmonary (25), bone/joint (17) and skin/soft tissue (12). The median age was 40 years; 83% were male, 52% white, 13% HIV-infected and 35% had failed previous therapy. The majority of patients were treated with either 100 mg or 200 mg day-1. One patient on renal dialysis received 300 mg day-1. Baseline abnormalities were reassessed for evidence of efficacy every 4 months and expressed in a standardized scoring system. Cumulative overall response rates at 4, 8 and 12 months were 7%, 36% and 66% respectively. Twelve month response rates by disease were 77% (pulmonary), 62% (skin/soft tissue) and 31% (bone/joint). Fifteen patients failed therapy although seven of these were still on treatment when the study was discontinued. Two failed due to toxicity. Possible symptoms or signs of toxicity occurred in 24 (44%) patients and were generally mild. SCH 39304 is an effective and well tolerated therapy for progressive forms of coccidioidomycosis.

Effects of antifungal therapy on inflammation, sterilization, and histology in experimental Candida albicans meningitis

To assess the effects of antifungal therapy on the course of Candida albicans central nervous system infection and inflammation, we inoculated intracisternally 10(5) CFU of C. albicans into rabbits. Fluconazole (10 mg/kg of body weight) or amphotericin B (1 mg/kg) was infused intravenously daily for 14 days. Treatment was initiated 24 h or 5 days after infection. Cerebrospinal fluid (CSF) was repeatedly obtained to culture the organisms, assess the level of inflammation, and measure drug concentrations. Brain tissue was obtained at the end of therapy for culture, drug concentration determinations, and histopathology. The median number of days of treatment required to sterilize CSF cultures was 4 days for fluconazole therapy and 1 day for amphotericin B therapy (P = 0.037). There was a significant reduction in tumor necrosis factor alpha and leukocyte concentrations in the CSF of animals treated early versus those in untreated control animals (P < 0.05 and P < 0.001, respectively; analysis of variance). Compared with treated animals, a higher proportion of cultured CSF samples from untreated animals were positive for Candida (P < 0.001). A cultured brain sample from 1 of the 12 animals treated early with amphotericin B was positive for C. albicans (P < 0.01 versus controls); cultures of brain samples from 3 of 12 animals treated early with fluconazole were positive, whereas cultures of brain samples from 10 of 12 controls were positive (P < 0.05). The mean density of C. albicans was lower in the single culture-positive amphotericin B recipient (1 x 10(1) CFU/g of brain tissue) than in those treated with fluconazole (1 x 10(3) CFU/g) and in controls (8 x 10(4) CFU/g). In animals treated late, the density of C. albicans in the brain in relation to the number of days of therapy was significantly lower in amphotericin B recipients than in those treated with fluconazole (P < 0.01) and untreated controls (P < 0.01; analysis of covariance). By histopathology, a larger proportion of untreated animals compared with those treated early demonstrated features of severe infection such as perivasculitis, ventriculitis, and evidence of fungal organisms. Compared with amphotericin B-treated rabbits, those given fluconazole had a trend toward more severe pathologic lesions. Reduced susceptibility to both fluconazole and amphotericin B was observed in the C. albicans organisms isolated from the brain of one fluconazole-treated animal. These data suggest that amphotericin B is the preferred treatment for C. albicans infections of the central nervous system.

Sch 39304, a new antifungal agent: oral and topical treatment of vaginal and superficial infections

Sch 39304 is a new broad spectrum triazole antifungal agent that is active, orally and topically, against superficial Trichophyton mentagrophytes and vaginal Candida albicans infections. Sch 39304 was compared to fluconazole (FLZ) in a T. mentagrophytes infection model in guinea pigs. Following topical administration, Sch 39304 (0.125%, twice daily, 10 days), was 5-8-fold more effective than FLZ, based on culture and lesion score results. Following oral administration, Sch 39304 (2.5 mg kg-1, once daily, 10 days) produced a dramatic reduction in lesion scores and was 20-fold more active than FLZ; however, due to the length of time it takes for the drugs to reach the infected area of the skin and eradicate the infections, most animals remained culture positive with both drugs. Sch 39304 was also compared with FLZ in a vaginal C. albicans infection in hamsters. Following oral administration (4 days), Sch 39304 (1.6 mg kg-1), cured all hamsters and was 4-fold more active than FLZ. In addition, Sch 39304 as a single oral dose (10 mg kg-1) also cured all hamsters. When treatment was intravaginal (8 days), Sch 39304 was again more active than FLZ (2-fold), and also micronazole (8-fold), with 100% of the hamsters cured at concentrations as low at 0.025%.

Systemically administered antifungal agents. A review of their clinical pharmacology and therapeutic applications

Systemic antifungal agents express great diversity in their pharmacokinetic profiles, mechanisms of action, and toxicities. Understanding the diverse pharmacokinetic properties of systemic antifungals is critical to their appropriate application. Amphotericin B, drug of choice for most invasive mycoses, has unique pharmacokinetic properties, binding initially to serum lipoproteins and redistributing from blood to tissues. Dosing recommendations are based on the specific infection and the status of the host. Lipid formulations of amphotericin B may be able to attenuate some of its toxicities. Flucytosine is a water-soluble, fluorinated pyrimidine that possesses excellent bioavailability. It is administered only in combination with amphotericin B because of frequent development of secondary drug resistance, and is associated with dose-dependent bone marrow suppression. The antifungal azoles are relatively well tolerated, have broad spectrum antifungal activity, and are fungistatic in vitro. Ketoconazole and itraconazole are highly bound to plasma proteins, are extensively metabolised by the liver, and are relatively insoluble in aqueous solution. By comparison, fluconazole is only weakly bound to serum proteins, is relatively stable to metabolic conversion, and is water soluble. Fluconazole penetrates the cerebrospinal fluid well and is approved for primary and suppressive therapy of cryptococcal meningitis in AIDS patients. The echinocandins have a narrow spectrum of antifungal activity, being effective only against Candida spp.

In vitro and in vivo activities of SCH 42427, the active enantiomer of the antifungal agent SCH 39304

SCH 39304, a new triazole antifungal agent, is a 50:50 racemic mixture of two enantiomers, SCH 42427 and SCH 42426. The activities of these three compounds were compared in a series of in vitro and in vivo experiments. SCH 42427 was twofold more active in vitro against a variety of yeasts and dermatophytes than SCH 39304, while SCH 42426 was inactive (MICs greater than 64 micrograms/ml). In a systemic Candida albicans infection in mice, SCH 42427 administered orally (p.o.) (50% protective dose [PD50], 0.17 mg/kg of body weight; 50% effective dose, [ED50], 0.47 mg/kg) had greater efficacy than SCH 39304 (PD50, 0.21 mg/kg; ED50, 0.62 mg/kg) and SCH 42426 (greater than 100 mg/kg for PD50 and ED50). In a pulmonary Aspergillus flavus infection in mice, SCH 42427 p.o. (PD50, 13 mg/kg) was also more effective than SCH 39304 (18 mg/kg) and SCH 42426 (greater than 250 mg/kg). In a C. albicans vaginal infection in hamsters, SCH 42427 p.o. (ED50, 3.5 mg/kg) was more active than SCH 39304 (8.5 mg/kg) and SCH 42426 (320 mg/kg). Following topical administration, against a Trichophyton mentagrophytes infection in guinea pigs, SCH 42427 was about 2-fold more active than SCH 39304 and about 100-fold more active than SCH 42426. These and other results indicated that SCH 42427 is the active enantiomer, responsible for all the antifungal activity observed with SCH 39304.

Comparison of SCH 39304, fluconazole, and ketoconazole for treatment of systemic infections in mice

SCH 39304 was compared with fluconazole and ketoconazole in a systemic Candida albicans infection in mice (10(6) CFU per mouse). Results were based on survival rates and CFU in kidneys following once-daily oral treatment of 2, 5, or 10 days duration. In normal mice, SCH 39304 (dose to reduce kidney counts by 4 log units, 0.5 mg/kg of body weight) was 3 and 200 times more active than fluconazole and ketoconazole, respectively. In immunocompromised mice (gamma irradiation, 600 rads), SCH 39304 (dose to reduce kidney counts by 4 log units, 1.3 mg/kg) was 35 and greater than 100 times more active than fluconazole and ketoconazole, respectively. In normal mice, when the infecting inoculum varied from 10(5) to 10(7) CFU, only a fivefold increase in the dose to reduce kidney counts by 4 log units was observed with SCH 39304. Excellent protection was also seen when mice were treated with a single oral dose of SCH 39304 up to 24 h prior to infection with C. albicans. Studies in a systemic C. albicans infection model indicated that SCH 39304 is equally efficacious following either oral or intravenous administration. In a systemic Aspergillus flavus infection, mice treated with SCH 39304 (5 mg/kg) survived twice as long (16 days) as those treated with fluconazole (50 mg/kg) or controls did.