Download Challenges and new discoveries in the treatment of

J Infect Chemother (2004) 10:307–315
DOI 10.1007/s10156-004-0348-9
© Japanese Society of Chemotherapy and The Japanese Association for Infectious Diseases 2004
REVIEW ARTICLE
Sarman Singh · Ramu Sivakumar
Challenges and new discoveries in the treatment of leishmaniasis
Received: July 26, 2004 / Accepted: September 16, 2004
Abstract Leishmaniasis is a parasitic disease caused by a
hemoflagellate, Leishmania spp. The parasite is transmitted
by the bite of an infected female phlebotomine sandfly. The
disease is prevalent throughout the world and in at least 88
countries. Human leishmanial infections may manifest in
any of the four most common forms. Depending on the
causative species, it can manifest as cutaneous leishmaniasis
(CL), mucocutaneous leishmaniasis (MCL), diffused cutaneous leishmaniasis (DCL), or visceral leishmaniasis (VL).
Although there are nearly 25 compounds having antileishmanial effects, only a few are used for humans and
most of these are parenteral. The oldest was urea stibamine,
developed in India in 1922. The original drug had severe
toxic effects, and later on its pentavalent compounds were
prepared, which remained the sole treatment modality for
several decades and saved millions of lives. However, reports of unresponsiveness to pentavalent sodium antimony
gluconate (SAG) started in the 1970s, and in some parts of
India about a quarter of kala-azar cases are reported to
have developed resistance even to its higher doses. This
development led to successful clinical trials of pentamidine
and amphotericine B. The latter, an antifungal compound,
was also found to be highly nephrotoxic, and to minimize
these side effects various colloidal and lipid formulations
have been prepared. These preparations are comparatively
safe but are exorbitantly costly. In the past two decades,
more focus has been given to finding oral drugs to minimize
injection-associated complications, including blood-borne
infection. Various drugs were reported effective, including
antifungal ketoconazole. However, the most promising
drug found is an anticancer compound, miltefosine, that
belongs to the alkylphosphocholine group. The drug has
undergone experimental and clinical trials and found to be
94%–97% effective. However, the drug cannot be given
S. Singh (*) · R. Sivakumar
Division of Clinical Microbiology, All India Institute of Medical
Sciences, P.O. Box 4938, New Delhi, India
Tel. ⫹91-11-26588484/26594977; Fax ⫹91-11-26588641/26588663
e-mail: [email protected]
during pregnancy and shows severe gastrointestinal side
effects. Moreover, its cost will be another limiting factor.
Other drugs such as paromomycin, allopurinol, and
sitamaquine have been reported with variable cure rates.
Because of these limitations, a combination therapy, preferably coupled with specific parasite enzyme inhibitors, is the
only hope.
Key words Kala-Azar · Sodium antimony gluconate ·
Amphotericin B · Miltefosine · Edelfosine · HIV
Introduction
Leishmaniasis is a vector-borne parasitic disease caused by
a hemoflagellate, Leishmania spp., that is transmitted by the
bite of an infected phlebotomine sandfly. Leishmaniasis is
prevalent throughout the world, in at least 88 countries.
More than 90 percent of the cutaneous cases appear in
Afghanistan, Saudi Arabia, Algeria, Brazil, Iran, Iraq,
Syria, and Sudan, whereas more than 90% of visceral cases
appear in India and Sudan. The mucocutaneous form is
mostly found in Latin America.1,2 Approximately 350 million people live in the area of active parasite transmission.1,2
Historically, the visceral form of leishmaniasis or kala-azar
had been known by various other names in the 19th century,
such as Jessore fever, Kala-dukh, Sarkari Beemari,
Burdwan fever, and fatal fever. The earliest kala-azar epidemic, which occurred in 1824 in the Jessore district of India
(now in Bangladesh), was confused with malaria and the
disease was named Jessore fever; however, the clinical
manifestations as inscribed in Indian history suggest that
the disease was visceral leishmaniasis. Later epidemics of
similar disease occurred in Bengal in the years 1832, 1857,
1871, 1877, and 1899. In Assam, kala-azar epidemics
occurred in 1885, 1897, 1913, 1925, 1944, and 1963. Bihar,
which is the present focus of this disease, had several epidemics earlier also. However, the first epidemic correlated
retrospectively in Bihar was in 1882–1885, 1917, 1933, and
1939. After independence, although kala-azar never dis-
308
appeared completely, after introduction of the National
Malaria Eradication Programme in 1955–1960 the number
of kala-azar cases decreased drastically.3–5 Unfortunately,
due to the cessation of DDT spraying in Bihar, the disease
reappeared in Bihar in 1977 and millions of people developed kala-azar in Bihar alone.3–5 The disease has been
rampant and endemic since then in India as a whole and
particularly in Assam, West Bengal, Bihar, and eastern
Uttar Pradesh (UP), with an east to west shifting trend. This
epidemic turned into an endemic form and continues to
take the lives of several million people, resulting in unimaginable economic loss to the state and to the country.5,6
in Spain and France. A review of current literature found
that 20%–40% of cases had an absence of splenomegaly.8
In India, where mucocutaneous leishmaniasis has not been
reported so far, healed visceral leishmaniasis may manifest
as mucocuaneous leishmaniasis involving the oral cavity,
nasal mucosa, conjunctiva, and tongue. Leishmania
amastigotes are commonly found in Kaposi’s sarcoma and
herpes zoster lesions concomitant with VL in AIDS
patients. Leishmaniasis has also been reported presenting
as a dermatomyositis-like eruption in three patients with
AIDS.1,8
Causative agent and vector
Clinical manifestations
Human leishmanial infections may manifest in four most
common forms. Depending on the causative species, it can
manifest as cutaneous leishmaniasis (CL), mucocutaneous
leishmaniasis (MCL), diffused cutaneous leishmaniasis
(DCL), or visceral leishmaniasis (VL). Visceral leishmaniasis is also commonly known as kala-azar, which is characterized by prolonged fever with or without double peaks,
anemia, loss of appetite and weight, and gross hepatosplenomegaly. If untreated, the peculiarity of Indian kala-azar is
that the skin of the patient becomes darkened, from which
is derived its name, kala (blackening)-azar (fever).5
Although the infection produces only moderate toxic symptoms, due to severe weight loss, anemia, and systemic
impairment, the patient dies. The fatality rate is almost
100% in children and females from poor families.5,6
Approximately 2%–5% successfully treated cases of kalaazar develop cutaneous sequelae, which are characterized
by hypopigmentation with or without maculopapular lesions on the skin. This sequela is seen a few months or years
after a kala-azar cure or sometimes even simultaneously.7
This condition is known as post-kala-azar-dermal leishmaniasis (PKDL). Recently, apart from visceralizing species
of Leishmania, visceralization by dermotropic species
of this parasite has also been reported as a complication of immunosuppressive conditions such as acquired
immunodeficiency syndrome (AIDS). Because human
immunodeficiency virus (HIV)-1 is a frequent cause of
immunosuppression, an increasing number of cases of
HIV–Leishmania coinfection are being described from areas where both infections overlap. HIV modifies the clinical
presentation of all form of leishmaniasis in the coinfected
patients. Several atypical etiological agents have been
described in leishmanial syndromes affecting HIV-infected
subjects. In HIV-associated leishmaniasis, parasitic dissemination throughout the reticuloendothelial system by the
nonvisceralizing species and to atypical locations in the
visceralizing syndrome are reported. Fulminant presentation of VL is frequent in patients with AIDS, and relapses
are usual. We have encountered five HIV cases, all from the
kala-azar endemic area, in whom the first clinical manifestation was leishmaniasis. VL is now the fourth most common
opportunistic parasitic disease in HIV-positive individuals
Kala-azar in India is caused by a parasite called Leishmania
(donovani) donovani, which is a hemoflagellate. The parasite was reported by Leishman and Donovan in London and
Madras, respectively, in the same year, 1903.1,2 Epidemiologically, infections may be zoonotic or anthroponotic,
when animals and humans, respectively, serve as reservoirs.
More than 25 species of Leishmania are capable of producing disease in humans. Since its recognition, extensive studies have shown that the Indian kala-azar is anthroponotic
and is transmitted chiefly through the bites of the female
sandfly, Phlebotomus argentipes. Occasional reports of
transmittal through unscreened blood transfusions and
transplacental transmission are also on record.1,2,8,9 Although several animal reservoirs for leishmaniasis have
been identified in different countries, in India, no animal
reservoir of the parasite is identified yet. In Europe, the
Middle East, and Mediterranean countries, VL is caused by
L. infantum whereas in the New World the causative agent
is L. chagasi.1,2 Similarly, various species of Leishmania are
responsible for causing cutaneous and mucocutaneous
leishmaniasis; detailed description of their epidemiology is
beyond the scope of this review.
Treatment
There are nearly 25 compounds having antileishmanial effects, but only a few are classified as antileishmanial drugs
used for humans and most of these are parenteral. However, the first effective drug was ureastibamine, which was
discovered in 1912 and was first reported to be effective
against Leishmania donovani by Brahmchari of India in
1922. This discovery saved millions of lives of poor Indians,
for which Prof. Brahmchari was nominated for the Nobel
Prize in 1929 (Nobel Prize official website). Later on, the
refinement and development of pentavalent antimonials
[Sb(v)] reduced the side effects, and these compounds are
still the mainstay of treating all forms of leishmaniasis. The
most commonly used organic compounds of antimony (Sb)
are sodium antimony gluconate (SAG) (manufactured by
Albert-David of the UK) and meglumine antimoniate
(manufactured by Rhone-Poulence, Paris). However, local
manufacturers have been able to produce cost-effective
309
generic formulations in India. Although the precise mechanism of action is not fully known, the antimonials are known
to inhibit glycolytic enzymes and fatty acid oxidation in
Leishmania amastigotes, and there is a dose-dependent inhibition in net formation of adenosine triphosphate (ATP)
and guanosine triphosphate (GTP).4,10,11 These compounds
continued to be used successfully to treat millions of patients throughout the world for almost a half century, but
reports of unresponsiveness to the standard 10 mg/kg body
weight (BW) of sodium stibogluconate started in the 1970s.
Most of these cases were reported from India. However, the
disease remained treatable with high doses of 20 mg/kg
BW.11 During the last epidemic, which occurred in India in
the 1980s, about a quarter of kala-azar cases were reported
to have developed resistance even to the higher doses of
sodium stibogluconate (SAG) and even to the second-line
pentamidine therapy.11–13 Because most of the cases were
treated with higher doses of SAG and were followed up
during this epidemic, results of these studies demonstrated
several side effects of this regimen.13–15 Gasser et al.14 also
reported that Sb routinely causes pancreatitis during treatment and that pancreatic inflammation is probably the
cause of the nausea and abdominal pain experienced by
many patients.
Other side effects of antimonial therapy include pancytopenia and reversible peripheral neuropathy.15 Although
cardiotoxicity can occur with Sb treatment and may be the
cause of sudden death, significant electrocardiographic
changes (concave ST segments or QTC prolongation) do
not occur in patients given single courses of Pentostam
(20 mg/kg · day) for up to 28 days. However, the SAG
produced in India had a comparatively higher rate of
cardiotoxicity, probably a result of the longer duration of
treatment and manufacturing quality.10,11,13,14
However, some authors thought that several manifestations considered to be side effects of antimonials could
actually be the systemic manifestations of visceral leishmaniasis. Therefore, Berman13 in his review mentioned that
systemic toxicity caused by the antimonials may be best
determined in patients treated for mucocutaneous leishmaniasis, which is a nonsystemic disease. He cited a study in
which, of the 29 Peruvian MCL patients treated with
Pentostam for 28 days, 83% had myalgias and/or
arthralgias, 28% had abdominal symptoms, and 21% had
headache; 10% of patients had increased liver enzymes, but
these enzyme levels declined in spite of continued therapy.
None the less, this drug still remains the cheapest method of
treating leishmaniasis in developing countries.13
Pentamidine
To circumvent the problem of clinical resistance to Sb in
India, pentamidine isethionate was tried for the treatment
of visceral disease.16,17 This drug was primarily used for
treating Pneumocystis carinii pneumonia. The exact mechanism of action of pentamidine isethionate is not known, but
some workers hypothesized that this polyamine compound
4
acts on the kinetoplast DNA and inhibits its functions. The
pentamidine treatment was successfully used in the late
1970s and early 1980s by Jha,16 and a cure rate of 98.8% was
reported without any relapse. The regimen consisted of
4 mg/kg given three times a week for 3–4 weeks (10–12
injections). However, the success rate started declining in
the 1980s when even after 20 injections only 75.2% of patients were cured.10,11,17 The repeated administration of 2 mg
pentamidine isethionate/kg every other day for 7 days was
studied for the treatment of cutaneous disease in Colombia.
This regimen was 96% effective. To decrease the dosing
further, 2 mg/kg pentamidine was administered every other
day for only 4 days, but this decreased the cure rate to 84%.
However, a slightly higher dose (3 mg/kg/IM) administered
on 4 alternate days resulted in a 96% cure rate for 51
evaluable patients.18
The low-dose, short-course regimens for cutaneous leishmaniasis commonly result in myalgias, pain at the injection
site, nausea, and headache and less commonly result in a
metallic taste, a burning sensation, numbness, and hypotension. Reversible hypoglycemia occurred in about 2% of
cases. The incidence and severity of these side effects are
higher when the high-dose, long-course regimens are used
for treatment of visceral disease, as in India. However, it
can be difficult to distinguish side effects that are due to
pentamidine from those that are due to kala-azar or to Sb if
it is administered concomitantly. Jha et al.17 reported a 20%
incidence of tachycardia and/or hypotension and a 1% incidence of hyperglycemia among patients receiving pentamidine. Thakur10 reported a 10% incidence of hyperglycemia
and an 8% incidence of hypoglycemia, but most of his
patients received Sb in addition to pentamidine.
Because of the higher rate of toxicity in pentamidine
compared to Sb and recent reports of emergence of drug
resistance to pentamidine in India, this drug is rarely being
used for visceral disease in India. Moreover, the supply of
pentamidine is only through government hospitals in India,
which makes it less accessible to many patients. For cutaneous disease, the high cure rate associated with a low dose of
pentamidine given for a short period makes it an attractive
alternative to Sb and the treatment of choice in cases of
fresh cases as well as Sb treatment failure cases.13
Amphotericin B and lipid-associated amphotericin B
Amphotericin B is a polyene antifungal antibiotic agent,
discovered in 1956, from a bacterium of genus Streptomyces.
Amphotericin B binds to cell wall sterols but preferentially
to ergosterol, which is the major cell membrane sterol of
fungi as well as Leishmania, but not mammalian cell membranes. It selectively inhibits the membrane synthesis of the
parasite and causes holes in the membrane, leading to parasite death. Hence, its use in the treatment of the leishmaniasis has a biochemical rationale. However, to a lesser extent
it binds to human cell wall cholesterol, leading to its toxic
effects. Before 1990, amphotericin B was administered infrequently because of its known infusion-related side effects
310
such as fever, chills, bone pain, and, rarely, cardiac
arrest and delayed side effects such as hypokalemia and
nephrotoxicity.13,19
Amphotericin B (deoxycholate) has been given to large
numbers of patients with kala-azar that is clinically resistant
to Pentostam and pentamidine. In Bihar, 99% of patients
were cured with the standard regimen of 20 injections (1 mg/
kg/AD) of amphotericin B. Further studies showed that the
duration of therapy could be reduced by administering the
drug daily rather than every alternate day (AD) and that, in
India, a dose of 1 mg/kg/day could be administered initially
rather than incrementally.20,21
Mishra et al.22 found that the daily dose could be diminished from 1 mg/kg to 0.5 mg/kg/AD in patients who had not
received Sb(v) for 14 days with a 100% cure rate. Thakur et
al.21 found that amphotericin B could also be administered
to children (1 mg/kg every other day, for a total of 20 injections), in whom the success rate was 100%. In addition,
these authors found that amphotericin B was effective at a
dosage of 1 mg/kg for 20 days, without apparent harm to the
fetus, in five pregnant women. However, amphotericin B
formulations are now being more widely used for visceral
leishmaniasis and constitute the major advance in antileishmanial chemotherapy of the past two decades. The
reasons for the increased use of amphotericin B are a
greater demand due to the rise of kala-azar resistant to antimony and to pentamidine, coupled with its better formulations by various pharmaceutical companies, synthesized
from different species of Streptomyces that are less toxic.
In the new formulations, deoxycholate has been replaced
by other lipids. These formulations include liposomal
amphotericin B [L-AmB (Ambisome)],23,24 amphotericin B
colloidal dispersion [ABCD (Amphocil)],25 and amphotericin B lipid complex [ABLC (Abelcet)].26 Davidson et
al.23 from the UK reported the first clinical use of lipidassociated amphotericin B formulations for leishmaniasis in
a patient who was cured with 50 mg of the drug (~1 mg/kg)
given daily for 21 days. Other populations have also been
treated with L-AmB. Ten Indian patients with kala-azar
were cured with a dose of 2 mg/kg given on days 1, 5, and 10
(total dose, 6 mg/kg). In Sudan, a regimen of 3–5 mg/kg
given on 3 days had a poorer cure rate than 3–5 mg/kg given
for 6 days. This study showed that, at least under field
conditions, a total dose of ⱕ12 mg/kg is not effective.13
The L-AmB is well tolerated by children. However, the
success rate for HIV-infected patients is not better. Although patients are initially cured, half of them will have
relapses.13,23 Although ABCD was the first formulation,
only a few patients have received this formulation. In spite
of its low dose for a short period and 100% success rate, the
high incidence of infusion-related side effects such as chills,
fever, and increased respiratory rate has limited its wider
use.25 ABLC is the most recent formulation studied for the
treatment of kala-azar. A dose of 3 mg/kg administered
every other day for five injections was 100% successful to
cure patients with antimony-resistant kala-azar. Infusionrelated toxicity occurred with this formulation also, and
50% of patients had chills and fever during the last infusion.
The primary use of these formulations, which are exorbi-
tantly priced, has remained limited to severe and resistant
cases of visceral leishmaniasis, because several afore mentioned drugs are still effective for the nonvisceral disease
forms.13,19
In spite of the fact that lipid-associated amphotericin B
formulations are designed to replace amphotericin B, in the
absence of comparative studies it is not yet clear whether
lipid-associated amphotericin B should actually replace
amphotericin B for the treatment of visceral leishmaniasis.13
Mishra et al.22 found that amphotericin B at a total dose of
7 mg/kg was highly effective in Indian patients with visceral
leishmaniasis. As the recommended total dose of L-AmB is
~22 mg/kg in the UK, an effective dose of L-AmB in India is
6 mg/kg, the minimal effective dose of ABLC in India
is ~10 mg/kg, and the minimal effective dose of ABCD in
Brazil is ~10 mg/kg, it is not likely that the new formulations
will be more effective than amphotericin B deoxycholate
itself.13,22–26 The major advantage of the new formulations is
that they are less toxic than amphotericin B; therefore, the
total doses can be administered over a brief interval of 5–10
days. For clinical conditions where toxicity and duration of
therapy are the major concerns, these formulations will be
attractive propositions, but in situations where cost is a
major concern, as in India, Nepal, and Bangladesh, the new
formulation will be extremely costly and unsuitable. For
these situations, amphotericin B or even SAG may still be
preferred to the new and relatively expensive formulations.
Paromomycin (aminosidine)
Paromomycin is an aminoglycoside used for the treatment
of bacterial diseases. However, paromomycin has also been
found to have broad antiparasitic activity not shared by the
other aminoglycosides. Oral paromomycin is recommended
for the clinical treatment of intestinal amebic infections and
tapeworm infections. Injectable paromomycin has been
used for visceral leishmaniasis at dosages of 14–16 mg/
kg/day given for up to 3 weeks. This regimen showed a
cure rate of 79%.27 Paromomycin in combination with
stibogluconate has also been attempted successfully. The
combination of paromomycin plus pentostam given for 20
days cured 82% of Indian patients. Similarly, in Sudan,
paromomycin and pentostam reduced the total treatment
period to almost half the usual duration of pentostam
therapy.13 Injectable paromomycin has been used less successfully and even occasionally for the treatment of cutaneous leishmaniasis. A combination of paromomycin and
stibogluconate has also been used as therapy for the more
serious syndrome of diffuse cutaneous disease. Because
paromomycin is an aminoglycoside, it has potential for
renal toxicity and eighth cranial nerve toxicity.13,28
Cytokines
Badaro et al.29 first reported use of human recombinant
interferon-γ as an adjunct antimony therapy for visceral
311
leishmaniasis. These investigators found that seven of nine
cases of Sb-resistant kala-azar could be cured with the combination of interferon-γ given for 28 days. A subsequent
trial showed that interferon-γ was only partially effective by
itself.30 It was found that interferon-γ, in combination with
Sb, could speed the elimination of parasites in previously
untreated patients: both Kenyans and Indians experienced
more rapid elimination of parasites when treated with the
combination for 28 days than with antimony alone. The
combination of interferon-γ and antimony was not as effective against Brazilian Sb-resistant disease as originally
thought, but the combination did cure 9 (69%) of 13
patients with antimony-resistant visceral disease in India.
However, 2 patients died of drug toxicity, perhaps because
of the cumulative effect of previous therapy plus that of the
combination therapy. Moreover, its price is exorbitantly
high for a poor population.13,28–30
Oral agents
All the aforementioned drugs are given parenterally, which
has several disadvantages including hospitalization or
multiple hospital visits, injection expenses, and injectionassociated transmission of blood-borne infections such as
HIV and hepatitis B and C.31 Hence, oral treatment has an
obvious appeal and advantage, particularly for cutaneous
and post-kala-azar dermal leishmaniasis, which can be
treated on an outpatient basis. Although more than 20
drugs have been studied or tried to treat leishmaniasis, only
a few have been found effective.13,32–41
Allopurinol
Allopurinol was the first oral drug. This hypoxanthine analogue inhibits purine catabolism in mammalian cells and
purine anabolism in Leishmania. It works on the principle
that Leishmania spp. are unable to synthesize purines. Allopurinol is hydrolyzed to allopurinol riboside, an analogue
of inosine that is incorporated instead of ATP into leishmanial RNA. There it interferes with the normal protein
synthesis (purine salvage cycle) of the parasite. Although
allopurinol has been used to treat leishmaniasis for decades,
a recent placebo-controlled double-blinded trial in Colombian patients of cutaneous leishmaniasis caused by L.
panamensis showed that allopurinol (20 mg/kg/day for 28
days) was no better than placebo. It was concluded that
allopurinol monotherapy is ineffective against Colombian
cutaneous disease and therefore is unlikely to be effective
against other forms of leishmaniasis.13 Its efficacy against
Indian kala-azar was first reported in 1983 by Jha.34
Imidazole derivatives
Metronidazole and other imidazole derivatives as well as
several other oral drugs have been studied as antileishmanial agents.32,33 Metronidazole eliminated only 30% of
the parasites even when used at its peak serum levels (30 µg/
ml) after intravenous administration. However, ketoconazole was found effective against Leishmania. The principle
quoted for using imidazoles as antileishmanial drugs was
that the sterol composition of Leishmania species is similar
to that of yeast and other fungi. Almost 3 years before the
sterol structure of Leishmania was elucidated, it was shown
that ketoconazole has an important action on sterol synthesis and led to the conclusion that ketoconazole affected
ergosterol biosynthesis at one of the reaction sites. In a
study from the United States, the antileishmanial activity of
four imdiazole derivatives was determined in Leishmania
tropica-infected human monocyte-derived macrophage
cultures. The drugs used were miconazole, cotrimazole,
ketoconazole, and hydrolyzed ketoconazole. The results
showed that only hydrolyzed ketoconazole was the most
effective drug that eliminated all parasites at a dose of
3.0 µg/ml and 80%–95% of the parasites at drug concentrations that are achievable. However, other derivatives were
found ineffective or toxic.13,35–37
The mechanism of action of ketaconazole against Leishmania promastigotes is the same as for Candida albicans,
i.e., interference with membrane permeability (cytochrome
P450) secondary to loss of desmethyl sterols and accumulation of 14a-methyl sterols. These sterols have a detrimental
effect on the membrane permeability and hence on the
viability of the organism. Thus, the working hypothesis is
that the accumulation of 14-methylsterols consequently
leads to an alteration in the membrane fluidity and permeability. Weinrauch et al.35 reported on the use of ketoconazole (400 mg/day) for 28 days in eight patients with
cutaneous lesions caused by L. major; five of these were
cured. There are other reports of favorable response to
ketoconoazole in cutaneous leishmaniasis of the Old World.
Encouraged by the results with ketoconazole, the congener
itraconazole has also been tried in patients with cutaneous
leishmaniasis. Despite its varied use in cutaneous leishmaniasis, the efficacy of ketoconazole in visceral leishmaniasis
was reported for the first time from India by our group.37
The initial report of this study showed ketoconazole to be
efficacious in the treatment of kala-azar, and 80% of patients were cured with a regimen of ketoconazole 600 mg/
day for 28 days. However, others working in Bihar did not
find it effective even at 400 mg/day.38 Our study on patients
resistant to antimony or pentamidine therapy showed a
consistently favorable outcome in which seven of nine
patients had complete cure with 200 mg ketoconazole given
thrice daily. The common side effect of ketoconazole
we noticed was hepatotoxicity. Less commonly observed
were endocrine dysfunction, reduction in cortisol levels,
reduced cortisol response to corticotrophin, and, rarely,
adrenal insufficiency, hyponatremia, confusion, and
hypoadrenalism.37
Itraconazole is more easily tolerated than ketoconazole.
In essentially uncontrolled studies, itraconazole (200 mg/
day given for 4–8 weeks) cured 15 (79%) of 19 patients from
the Old World with cutaneous leishmaniasis and 10 (66%)
of 15 patients from India. Akuffo et al.36 pointed out the
requirement for controlled studies of Old World cutaneous
312
A new primaquine analogue, sitamaquine (WR 6026), was
developed by Walter Reed Army Institute of Research
(United States) originally for malaria and has no biochemical rationale. Although animal studies showed very encouraging results against visceral leishmaniasis, human trials
done on Kenyan patients did not find it more than 50%
effective in kala-azar treatment at 1 mg/kg/day for 28 days.
In another study done on Brazilian patients using escalated
doses, the optimum safe dose was 2 mg/kg/day for 28 days
but the cure rate did not increase above 67%. The higher
doses showed nephrotoxicity.39
and been approved by the World Health Organization for
kala-azar treatment in India and for other forms of leishmaniasis. In a phase II multicentric clinical trial in which doses
of 50 mg, 100 mg or 150 mg/day of miltefosine in adult patients were tried, of 120 patients, 114 patients had complete
cure while 6 (5%) patients had relapses within 6 months.43
Miltefosine is an effective and safe treatment for immunocompetent adult male patients at the 100 mg/day dose, with
an overall cure rate of 97% in VL patients and 94% in new
World CL.The major side effects noticed were gastrointestinal disturbances. Other side effects were elevated liver
enzymes and renal toxicity.43–46 In a phase III clinical trial
concluded recently on a large group of patients, the study
showed an initial cure rate of 100%, but the final cure rate
after 6 months was only 94% of patients cured compared to
a 97% cure rate for amphotericin B-treated cases. The
major side effects in this trial were also gastrointestinal,
vomiting (38%) and diarrhea (20%) at the 100 mg/day dose
for 28 days.44 However, very recently unresponsive strains
of Leishmania spp. have been reported against this drug
too.47,48
Alkylphosphocholine analogues
Local therapeutic agents
Recently, two compounds of the alkylphosphocholine
group developed by Zentaris (Frankfurt, Germany) have
been found to have antineoplastic activity, and the mode of
action involves protein kinase C. The knowledge of this
protein kinase C enzyme being present on the plasma membrane of Leishmania led some investigators to try these
compounds on cutaneous leishmaniasis.40,41 These compounds were found to be well absorbed from the intestinal
tract and have more potent action than by the parentral
route. The preliminary studies on Leishmania major skin
lesions showed encouraging results. In this study, two compounds from the alkylphosphocholine group, hexadecylphosphocholine [HePC (present trade name, Miltefosin)]
and Octadecyl-phosphocholine (DoPC), were evaluated for
their antileishmanial activity in the mouse model of cutaneous leishmaniasis as local therapy. Although both compounds healed the lesions within 30 days, the lesions
relapsed in DoPC-treated animals whereas HePC-treated
animals showed a complete cure.42 To advance further, the
effect of these compounds was also studied in vitro on L.
donovani strains from India for the first time. HePC demonstrated a high degree of parasiticidal action on all five
Indian strains: DD8, RMRI68, SS, AG83, and UR6, and all
promastigotes died within 48 h of exposure.42
The inhibitory or lethal effects of these two compounds
on L. donovani were compared with sodium antimony gluconate (SAG) and pentamidine isothionate. Encouragingly,
with these results, the animal studies also indicated that
these compounds were highly effective for visceral leishmaniasis.42 The drugs were tolerated well by the animals with
only minor noticeable side effects such as 10% loss of
weight and sluggishness.42 Hexa-decylphosphocholine or
miltefosine has now successfully undergone clinical trials
Local threatment of superficial tegumentary diseases such
as cutaneous leishmaniasis is undoubtedly preferable because of the ease of drug administration and its appropriateness for outpatient use. Also, absorption of the drug into
the circulation and risk of systemic toxicity are minor.
Intralesional administration of antileishmanial agents is a
method of treatment that has been used for decades; in two
recent reports (one containing ⬎1000 cases), investigators
reiterate that there is a cure rate of ~75% with intralesional
Sb(v) therapy.49,50 This technique is effective; however, the
injections are administered intermittently over ~1 month,
each lesion has to be injected individually, and there are no
data on large series from the New World.50,51 Major emphasis has been placed on topical application of paromomycincontaining formulations. El-On et al.49 showed, in Israel,
that L. major lesions treated with 15% paromomycin plus
12% methylbenzethonium chloride in soft white paraffin
twice a day for 10 days cleared more rapidly (cure rate,
100% at 21–30 days) than did untreated lesions on the same
patients (cure rate, 100% at 51–60 days), and this formulation has now been marketed in Israel. In the New World,
this formulation was reported to be highly effective in
Ecuador, where 90% of 52 patients were cured 100 days
after therapy; however, the trial was uncontrolled, and the
natural cure rate in Ecuador can be 75%.51 In Colombia,
investigators studied the combination of topical paromomycin (15%) and methylbenzethonium chloride (5%) plus a
short course of parenteral glucantime because it was believed that the topical agent by itself was unlikely to be
effective and that the systemic agent might clear parasites
that had already disseminated from the cutaneous site. The
cure rate was low for patients given the topical agent for 10
days plus glucantime for 3 day [8 (42%) of 19 patients were
leishmaniasis; these investigators found in a small doubleblinded study that itraconazole (200 mg/day for 4 weeks)
was not better than placebo.36 Another azole derivative,
fluconazole, is inactive in vitro. Therapeutic studies done in
India on kala-azar patients using a dose of 6 mg/kg/day for
30 days showed apparent clinical and parasitological cure in
only 50% of cases, but these had relapses within 2 months.38
Sitamaquine
313
cured], but the rate was high for patients given the topical
agent for 10 days plus glucantime for 7 days [18 (90%) of 20
patients were cured]. These results showed that the topical
agent by itself would not be appreciably effective in Colombia but that the combination of the topical agent and a
weeklong course of meglumine was as effective as had been
found historically for a standard 20-day course of glucantime.51–54 Nevertheless, the usefulness of a topical agent plus
a short course of Sb(v) remains to be confirmed in a controlled trial.13
Because there is an appreciable rate of local reaction to
the paromomycin/methylbenzethonium chloride formulation, in that 25% of patients develop a burning sensation
and pruritis and 15% develop vesicles, another formulation
has been developed in which methylbenzethonium chloride
has been replaced by 10% urea. Although 10% paromomycin ⫹ 10% urea administered for ⱕ12 weeks cured 23
(85%) of 27 patients with Old World leishmaniasis in an
open study, this formulation, administered for 2 weeks, was
no more effective than placebo in controlled trials for L.
major disease. In Tunisia and in Iran, the percentage of
treated patients who were cured at 4.5 weeks and at 3 weeks
after treatment was virtually identical to the percentage
who were cured in the placebo group. The results of these
controlled trials show that the paromomycin/urea ointment
is ineffective when administered for 14 days and that the
natural cure rate for Old World cutaneous leishmaniasis can
be high 15 weeks after medical attention has been sought. It
is possible that the paromomycin/urea formulation might be
effective if it is administered for longer than 2 weeks. However, a longer treatment period will make it more difficult to
show a cure rate that is different from that for placebo and
will make the regimen less attractive. The use of commercially available topical imidazole creams is financially
attractive and is a biochemically rational approach. Topical
miconazole (2%) and topical clotrimazole (1%) were
administered twice a day for 30 days to patients in Saudi
Arabia. However, 1 month after therapy only 16% of
clotrimazole-treated lesions had fully healed, and none of
the miconazole-treated lesions had fully healed.13,51–54
The fundamental problem with local treatment for cutaneous leishmaniasis is that this disease is not a superficial
problem as are infections due to the dermatophytes. Leishmania amastigotes reside deep in the dermis and also disseminate to the lymphatic system and mucosal membranes.
For successful treatment of cutaneous lesions with local
injections, the drug has to deeply infiltrate the lesion, which
is difficult to achieve in a standardized manner, particularly
for Western clinicians who rarely treat this diseases. Even
when topical agents are effective in vitro, they also must
penetrate deeply to be effective against cutaneous lesions.
Even a huge concentration of agent and a vehicle designed
to aid penetration may not be sufficient to achieve the
necessary penetration. For example, the concentration of
paromomycin in the paromomycin/urea formulation is
15 000 µg/ml, whereas a 100% lethal dose of paromomycin
in vitro is 10 µg/ml; although urea is added as an aid to
penetration, the paromomycin ⫹ urea formulation has so
far been ineffective in controlled trials. An additional major
concern about the use of local therapy is that it should not
cure lymph node infection or protect against mucosal disease if metastasis has already started. In spite of these problems, it is possible to conceive of strategies by which
virtually all cutaneous disease could be topically treated.
An effective topical agent would be the treatment of choice
for L. major and L. (mexicana) mexicana infections, which
generally do not disseminate. Topical treatment would also
be appropriate for cutaneous disease that relapses after
systemic therapy is administered, because nascent metastasis would probably be eliminated by the systemic agent. A
topical agent in combination with short-course systemic
therapy might be appropriate for cutaneous disease that has
or is likely to have already disseminated.13 Although theoretically all cutaneous diseases could be treated with a topical agent or their combinations with short-course systemic
therapy, proving that such a regimen is effective will require
careful clinical studies. A high cure rate for infections due
to L. major and L. (mexicana) mexicana will be simple to
demonstrate in an uncontrolled experiment but difficult to
differentiate from rapid natural cure rates. A high cure rate
for disease due to L. braziliensis complex will be difficult to
achieve.
Combination therapy
After increasing unresponsiveness to most of the
monotherapeutic regimens, the combination therapy has
found new scope in the treatment of both cutaneous and
visceral leishmaniases.55–59 Recently, combination therapy
with sodium antimony gluconate (SAG) and indolylquinoline derivative A [2–2(2⬙-dichloroacetamidobenzyle)3-(39-indolylquinoline)] showed 100% clearance of the
parasites from liver and spleen of the hamsters as compared
to 93% and 80%, respectively, when indolylquinoline
derivative A and SAG were used singly.57 Similarly, the
combination of low dosage pentamidine and allopurinol
was more effective in achieving an ultimate cure in 91.25%
of kala-azar patients as compared to 74.35% using pentamidine alone.58,59 All monotherapies of cutaneous leishmaniasis are less effective as compared to topical paromomycin
plus methylbenzethonim chloride, curing 85.7%–91.4%
cases. Other drugs tried are atovaquone, roxithromycin,
and edelfosine.55–57 Bryceson55 suggests that drugs that have
a long half-life and low therapeutic ratio, e.g., miltefosine,
may induce drug resistance; therefore, such drugs should be
used only in combination with another drug that has a short
half-life and greater therapeutic ratio.
HIV–leishmania coinfection
In HIV-associated leishmaniasis, parasitic dissemination to
the skin in DCL, or throughout the reticuloendothelial system by the nonvisceralizing species, and to atypical locations in visceralizing syndromes is reported.60 Leishmania
amastigotes are commonly found in Kaposi’s sarcoma and
314
herpes zoster cutaneous lesions concomitant with VL.
Fulminant presentation of VL is possible in patients with
AIDS, and relapses are usual. A review of current literature
found that 20%–40% of cases had absence of splenomegaly.
Lack of anti-Leishmania antibodies is a characteristic feature seen in these patients.61,62 General treatment of leishmaniasis is indicated for each clinical presentation, although
localized cutaneous lesions may benefit from topical and/or
intralesional therapy as well. Tortajada et al.63 followed an
HIV-infected cohort of 3589 patients from 1985 to 2000.
Forty-five cases of visceral leishmaniasis were diagnosed at
a mean CD4 count of 97.78% and previously had an
AIDS-defining illness. Highly active antiretroviral therapy
(HAART) was protective against leishmaniasis. Six deaths
were associated with leishmaniasis among patients without
access to HAART. The probability of HAART patients
remaining free of relapse was 66% compared to 10%
for those not treated with HAART. The trend toward
fewer relapses is attributed to immune restoration due to
HAART.
Future perspectives
Although several drugs are in use for treating leishmaniasis,
a novel drug is yet to come. All drugs have some limitations
including unaffordable cost and toxicity. Mechanism of
drug resistance and interspecies variation in drug susceptibility are also important areas to explore. Drug susceptibility in relation to genetic heterogeneity in Leishmania
species and strains is another area of interest. Efforts should
be made to develop drugs that target well-characterized
genes essential for survival of the parasite selectively, such
as topoisomerase-II, reported recently by Das et al.64
Summary
Leishmaniasis is a major public health problem. The disease
manifests atypically in HIV co-infected persons. The most
significant development in visceral leishmaniasis has been
in the field of treatment. Although pentavalent antimony
compounds still remain the mainstay for primary treatment
of the cutaneous and even the visceral form of the disease,
more effective and safer drugs have been developed, including various formulations of amphotericin B and recently the
oral drug miltefosine. However, cost, safety, and duration of
treatment still remain major concerns. On the research
front, the mechanism of drug resistance is a major area to
which more attention needs to be paid.
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