Rifampicin treatment of cutaneous leishmaniasis

Advances in Development of New Treatment for Leishmaniasis

Leishmaniasis is a neglected infectious disease caused by several different species of protozoan parasites of the genus Leishmania. Current strategies to control this disease are mainly based on chemotherapy. Despite being available for the last 70 years, leishmanial chemotherapy has lack of efficiency, since its route of administration is difficult and it can cause serious side effects, which results in the emergence of resistant cases. The medical-scientific community is facing difficulties to overcome these problems with new suitable and efficient drugs, as well as the identification of new drug targets. The availability of the complete genome sequence of Leishmania has given the scientific community the possibility of large-scale analysis, which may lead to better understanding of parasite biology and consequent identification of novel drug targets. In this review we focus on how high-throughput analysis is helping us and other groups to identify novel targets for chemotherapeutic interventions. We further discuss recent data produced by our group regarding the use of the high-throughput techniques and how this helped us to identify and assess the potential of new identified targets.

Contact dermatitis-like cutaneous leishmaniasis in a Libyan HIV patient

Background

Cutaneous leishmaniasis (CL) is one of the common tropical protozoal diseases caused by various Leishmania species, and transmitted by the sand-fly vectors, Phlebotomus and Lutzomyia species. Herein, we report for the first time a case of CL that presented as large eczematous plaques occurring on the dorsi of both feet in a Libyan drug addicted, alcoholic patient with HIV infection.

Findings

A 34 year-old HIV-positive, alcoholic, drug addicted Libyan male presented to us with a history of a non-itchy skin lesions on the dorsi of both feet of 5-weeks duration. Systemic and topical antibiotics were given without improvement. Diagnosis of this patient was confirmed by observation of Leishmania amastigote bodies in stained slit-skin smear skin biopsy. After parenteral administration of sodium stiboglyconate (Pentostam) (20 mg/kg/day) for 28 days the lesions did not show any marked improvement. Concurrently, combination therapy of oral rifampicin (600 mg/day) and isoniazide (300 mg/day) was given for 8 weeks. Complete healing of lesions was achieved after this treatment and skin-slit smears turned negative.

Conclusions

Localized cutaneous leishmaniasis should be remembered in deferential diagnosis of unresponsive contact dermatitis especially for HIV-positive patients in CL endemic areas.

This patient was not responding to Pentostam therapy, which is not very common in Libya. Interestingly, combination of oral rifampicin (600 mg/day) and isoniazide (300 mg/day) can be a successful alternative therapy.

Identification of potent chemotypes targeting Leishmania major using a high-throughput, low-stringency, computationally enhanced, small molecule screen

Patients with clinical manifestations of leishmaniasis, including cutaneous leishmaniasis, have limited treatment options, and existing therapies frequently have significant untoward liabilities. Rapid expansion in the diversity of available cutaneous leishmanicidal chemotypes is the initial step in finding alternative efficacious treatments. To this end, we combined a low-stringency Leishmania major promastigote growth inhibition assay with a structural computational filtering algorithm. After a rigorous assay validation process, we interrogated ∼200,000 unique compounds for L. major promastigote growth inhibition. Using iterative computational filtering of the compounds exhibiting >50% inhibition, we identified 553 structural clusters and 640 compound singletons. Secondary confirmation assays yielded 93 compounds with EC₅₀s ≤ 1 µM, with none of the identified chemotypes being structurally similar to known leishmanicidals and most having favorable in silico predicted bioavailability characteristics. The leishmanicidal activity of a representative subset of 15 chemotypes was confirmed in two independent assay formats, and L. major parasite specificity was demonstrated by assaying against a panel of human cell lines. Thirteen chemotypes inhibited the growth of a L. major axenic amastigote-like population. Murine in vivo efficacy studies using one of the new chemotypes document inhibition of footpad lesion development. These results authenticate that low stringency, large-scale compound screening combined with computational structure filtering can rapidly expand the chemotypes targeting in vitro and in vivo Leishmania growth and viability.

Leishmaniasis is a parasitic disease with cutaneous, mucocutaneous and visceral clinical manifestations, depending on the Leishmania spp. and human host. Globally, there are 350 million people at risk of leishmaniasis, but current treatment options rely predominantly on ancient pentavalent antimonials, which have the potential to cause serious systemic toxicity. Our research focuses on the rapid expansion of potential anti-leishmanial compounds that could function as novel chemical structures for future drug development and offer additional therapeutic options to patients with leishmaniasis. We combined high throughput screening methodologies with computational algorithms and multiple confirmatory assay formats to identify and characterize new potent L. major promastigote growth inhibitors, including one that displays in vivo activity without toxicity to human cells. Our use of a large, broadly distributed compound library enabled the identification of these new chemotypes. In addition, since this chemical library is publicly available and annotated, we were able to cross-query archived bioassays and to identify new molecular targets that may be involved in L. major growth and viability as well as identify new protein targets for future leishmanicidal drug discovery.

Fluconazole for the treatment of cutaneous leishmaniasis caused by Leishmania major

BACKGROUND

Whereas certain oral antifungal azoles are well documented to have activity against leishmania, data on the efficacy of fluconazole for leishmaniasis are limited. We conducted a controlled trial in Saudi Arabia of fluconazole for the treatment of cutaneous leishmaniasis caused by Leishmania major.

METHODS

This randomized, double-blind, placebo-controlled trial assessed the efficacy of oral fluconazole, in a dose of 200 mg daily for six weeks, in the treatment of parasitologically confirmed cutaneous leishmaniasis. The primary outcome measure was the time to the complete healing of all lesions.

RESULTS

A total of 106 patients were assigned to receive fluconazole, and 103 patients were assigned to receive placebo. Follow-up data were available for 80 and 65 patients, respectively. At the three-month follow-up, healing of lesions was complete for 63 of the 80 patients in the fluconazole group (79 percent) and 22 of the 65 patients in the placebo group (34 percent; relative risk of complete healing, 2.33 [95 percent confidence interval, 1.63 to 3.33]). According to an intention-to-treat analysis, the rates of healing were 59 percent and 22 percent, respectively (relative risk, 2.76 [95 percent confidence interval, 1.84 to 4.12]). Sodium stibogluconate was offered to 11 patients in the fluconazole group who returned for follow-up (14 percent) and 33 of those in the placebo group (51 percent) in whom oral treatment was judged to have failed. According to a Kaplan-Meier analysis, the time to healing was shorter for the fluconazole group (median, 8.5 weeks, as compared with 11.2 weeks in the placebo group; P<0.001 by the log-rank test). Side effects were mild and similar in both groups.

CONCLUSIONS

A six-week course of oral fluconazole is a safe and useful treatment for cutaneous leishmaniasis caused by L. major.

Use of rifampin in nonstaphylococcal, nonmycobacterial disease

Rifampin has very broad antimicrobial properties with in vitro activities against many bacteria, mycobacteria, higher bacteria, chlamydia, fungi, parasites, and viruses (Table 1). The clinical use of rifampin is more limited, in part because of the lack of in vivo human clinical studies demonstrating its efficacy. Investigators have valid concerns regarding the emergence of resistance of mycobacteria if widespread use of rifampin becomes common, although this has not been well documented. Because rifampin obtains therapeutic levels intracellularly and is distributed widely throughout the body, the antibiotic potentially could be used on a broader scale, but more studies will be needed to demonstrate its clinical utility.

Use of in vitro method to assess different brands of anti-leishmanial drugs

Reports in the literature indicate the use of animal models for testing newer anti-leishmanial drugs in vivo. However, in certain established cell lines and macrophages in vitro models have the advantage over the in vivo system of simplicity and speed with which the results can be obtained. A simple in vitro system using peritoneal exudate macrophages of BALB/c mice infected with Leishmania donovani promastigotes has been tested for its use in determining the efficacy of several new drugs. Two well-established drugs, amphotericin B and sodium stibogluconate, as expected, could kill the intracellular parasites effectively. Two relatively new drugs not routinely used against leishmania, rifampicin and metronidazole at concentrations of 20 micrograms/ml and 10 micrograms/ml, respectively, were also able to kill the intracellular leishmania parasites effectively. Critical factors for drug testing in vitro have been elucidated: the most important being the temperature of incubation after infection.

Antileishmanial effects of clofazimine and other antimycobacterial agents

In the search for more effective alternatives to the presently-used antileishmanial drugs, the activity of the major groups of antimycobacterial compounds has been examined, both in vitro and in animal models of infection. In vitro, clofazimine was the most active compound tested, with a mean ED50 of 2.3 mg l-1 against Leishmania mexicana amazonensis, 1.4 mg l-1 against L. donovani and 0.5 mg l-1 against L. major. Other active compounds were the thiosemicarbazone, thiambutosine, and salinazid, a derivative of isoniazid. Isoniazid itself was inactive, and rifampicin only partially active. In vivo, only clofazimine displayed significant activity, and it was most effective against the cutaneous infections. It is concluded that antimycobacterial activity is in general a poor predictor of antileishmanial potency.

Efficacy of rifampicin and isoniazid in cutaneous leishmaniasis

Thirty-nine patients with cutaneous leishmaniasis caused by Leishmania major were treated with rifampicin alone or in combination with isoniazid. No significant difference was found between these two therapeutic regimens, and about half of the patients were cured 2 months from the beginning of treatment. A review of rifampicin in cutaneous leishmaniasis is attached.

Topical treatment of cutaneous leishmaniasis

Sixty-seven patients, 19 females and 48 males, 4-66 years old, suffering from lesions of cutaneous leishmaniasis were treated topically with an ointment comprising 15% paromomycin sulfate and 12% methylbenzethonium chloride in white soft paraffin (P-ointment, U.K. patent GB117237A). After 10 days of treatment, twice daily, the lesions in 72% of the treated patients were free of parasites, 15% became free within an additional 20 days, without further treatment, and 13% failed to respond. Pigmentation developed in 18% of the treated lesions and inflammation of varying degree was associated with the treatment. These developments did not affect the clinical healing process which was generally completed in a period of 10-30 days after termination of treatment. In addition, 94% of the treated lesions healed with little or no scarring. No adverse clinical or laboratory side effects were observed except for a burning sensation at the site of treatment. Parasites isolated from patients who failed to respond to topical treatment were found to be susceptible to PR-MBCl in both in vitro infected macrophages and in vivo in experimentally infected BALB/c mice.

Clinical aspects of cutaneous leishmaniasis acquired in Texas

Five patients with cutaneous leishmaniasis are described. Four of these patients acquired leishmaniasis in Texas. Four cases represent acute cutaneous leishmaniasis, and one case probably represents chronic cutaneous leishmaniasis. The classification and treatment of cutaneous leishmaniasis are reviewed. One patient in this report was successfully treated with topical antimony cream. Cutaneous leishmaniasis must be considered in the differential diagnosis of nonhealing ulcerated papules and nodules even in patients who do not have a foreign travel history.

Interaction of aminoglycosides and ionophores in the killing of Crithidia fasciculata

Crithidia fasciculata was utilized as a prescreen to determine the antiprotozoal action of aminoglycoside antibiotics alone and in combination with surface-altering agents. Paromomycin was tested with the carrier ionophores nigericin and valinomycin, the channel ionophore gramicidin and the polyene antibiotics amphotericin B and nystatin. After exposure to the drugs in suspension, organisms were plated out to determine the survival of C. fasciculata. Killing was time dependent for both the antibiotic and the ionophore. Paromomycin action was found to be potentiated by all the surface altering agents. The aminoglycosides kanamycin, gentamycin and streptomycin were studied alone and in combination with nigericin. Synergistic effects were demonstrated both with kanamycin and gentamycin in combination with nigericin. Streptomycin was ineffective both alone and with surface-altering agents.

Growth inhibition of Leishmania tropica amastigotes in vitro by rifampicin combined with amphotericin B

Rifampicin and Amphotericin B (AMB) were studied separately and in combination to determine their effect in vitro on intracellular Leishmania tropica amastigotes. On the fourth day of treatment, rifampicin at 200 micrograms ml-1 or AMB at 0.15 microgram ml-1 reduced the parasites' survival index (PSI) to 10% compared with the untreated control. In combination, there was a significant synergistic effect at several concentrations. The synergistic therapeutic effects were not accompanied by toxicity to the host cells, although each drug alone caused cellular degeneration in the ultrastructure of the parasites with the formation of large autophagic-like vacuoles, while the combination increased the percentage of degenerate cells.

Combination therapy of sodium stibogluconate and rifampin in cutaneous leishmaniasis

Thirty-two patients having cutaneous leishmaniasis were divided into two groups: 16 were treated with sodium stibogluconate 600 mg intramuscularly daily for 12 days and 16 were treated with 600 mg rifampin daily for 21 days. The failure rate was 56% and 50%, respectively. The 17 patients who did not respond were treated with a combination of the two drugs, which produced better results in 13 of the 17 patients.