Discussion
Introduction
With an estimated 0.7 to 1 million new infections a year globally, cutaneous leishmaniasis (CL) is the most prevalent form of leishmaniasis; it clinically manifests as a variety of skin lesions ranging from closed nodules, to plaques and ulcers. Currently recommended drugs have proved to be clinically unsatisfactory indicating the urgent need for novel safe and efficacious drugs.
Oleylphosphocholine, an alkylphoshoplipid structurally similar to miltefosine, demonstrated potent activity against
Leishmania species causing visceral leishmaniasis (VL) both
in vitro and
in vivo. Given the discrepancies between the target product profiles of VL and CL, we here report the
in vitro and
in vivo efficacy of orally administered oleylphosphocholine-based formulations (two with a fast-release and two with a slow release profile) against CL-causing
Leishmania species.
Materials and methods
The antileishmanial activities of OLPC and miltefosine were evaluated against intracellular amastigotes of six
Leishmania species (
L. major,
L. tropica,
L. aethiopica,
L. mexicana,
L. braziliensis,
L. panamensis). Following promising results, the
in vivo efficacies of both drugs were investigated in two stages. First, the performance of the efficacious dose for OLPC for VL was evaluated using an experimental CL model. Secondly, the antileishmanial activity of various formulations of OLPC with diverse release profiles was investigated alongside a dose response using bioluminescent
L. major parasites. Tissue concentrations in skin of OLPC were determined using LC-MS/MS.
Results and discussion
The
in vitro activities of OLPC against CL-causing species ranged from 0.74 to 31.06 uM and are similar to those obtained for miltefosine. In the experimental CL models, OLPC administered orally at a dose of 35 mg/kg once daily for ten days was able to significantly reduce the lesion size to a similar extend as the positive control (paromomycin sulphate, ip, 50 mg/kg/day – repeated-measures ANOVA, post-hoc Tukey, p < 0.05). In contrast, the administration of miltefosine (same dose and regimen as OLPC) only resulted in a halt of the lesion size progression but was unable to decrease the lesion diameter. The second
in vivo study was able to confirm these results and demonstrated a superior activity of the fast- (OLPC with lactose or cellulose carrier) over the slow-release (OLPC absorbed into a diffusion-controlled silica carrier) test formulations as measured by a significantly greater bioluminescence signal (~ parasite load) decrease when compared to the untreated controls.
Extraction of the drugs from the infected skin site 24 hours after the oral administration of 1 dose (35 mg/kg) demonstrated higher concentrations of OLPC versus miltefosine (t-test). This difference was no longer present at the end of the 10-day treatment period even though OLPC blood concentrations at the end of treatment were 2-fold higher than for miltefosine.
Conclusions
OLPC demonstrated potent activity in the intracellular macrophage model using a range of CL-causing species and was able to reduce the parasite load in an experimental
L. major CL model after ten days of treatment. In a next step, the drug delivery profile into
Leishmania-infected and uninfected mouse skin will be compared using skin microdialysis.
Funding
This project received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No 815622. KVB is supported by a fellowship awarded from the Research Council United Kingdom Grand Challenges Researc
