Consultative meeting to develop a strategy for treatment of cutaneous leishmaniasis. Institute Pasteur, Paris. 13-15 June, 2006

Abstract

Background: A meeting was organized by Drugs for Neglected Diseases initiative (DNDi) and the Institute Pasteur (IP), Paris, to review the treatment for all forms of cutaneous leishmaniasis (CL) and to propose a strategy for the development of new efficacious and affordable treatments.

Method: The global burden of CL was discussed with respect to financial impact; relation to poverty; the stigma of CL lesions and scars (particularly in young women); lack of effective, affordable, easily implemented tools and political will and resources to implement available control tools; and lack of input from pharmaceutical and biotechnology companies to develop new drugs and vaccines.

Results: According to the experts from different endemic countries present, the financial and social burdens of CL are high, but we have limited quantitative data. The analysis of published trials indicates that the quality of most trials is poor and requires both improvement and standardization. The available drugs are inadequate. Criteria by which different CL types could be prioritized as target disease were set. These criteria included: severity of the disease; lack of response to available drugs; overall incidence and prevalence of the disease; sequelae of the disease, (including recidivans and mucosal leishmaniasis); the impact of treatment of individuals on control of transmission and lack of other major parties involved in drug development. Based on these, the anthroponotic CL and its sequel "recidivans" caused by L. tropica and CL caused by L. braziliensis and its sequel, mucosal leishmaniasis were considered to be the target diseases. The mechanism for controlling Leishmania infection to reach a stable self healing process is a balanced immune response. Immune stimulation during chemotherapy can enhance cure. There is no adequately effective vaccine, but some encouraging results have been obtained with whole killed Leishmania parasites or imiquimod (an immuno-modulator) plus antimonials. Further studies are needed. One safety/immunogenicity clinical trial is currently ongoing with a Second Generation Vaccine (SGV).

Conclusions and recommendations: There is an urgent need for new treatments for all CL types. CL should be considered as a neglected disease and organizations, such as DNDi, should include it in their list of target diseases. It was agreed that immuno-chemotherapy (with "therapeutic" vaccines or immunomodulators) has a strong potential to make an impact as a new therapy of CL with the view of shortening/reducing duration and dose of drug treatment and preventing resistance. There is also a need for safe, affordable and efficacious new chemotherapeutics. The quality of clinical trials needs to be enhanced and standardized. Short and long-term objectives and activities were defined as a part of meeting recommendations.

Figure 1

Schematic representation of decision matrix for short-term objectives (3 years). ctivities related to trials of selected combination of anti-parasitic drugs will proceed in parallel with development of immuno-chemotherapy approach using available drugs, immun-modulators, with or without leishmanial antigens. Efforts will be focused on enhancing the quality of clinical trials through development of standard protocols and ICH-GCP training.

Figure 2

Schematic representation of decision matrix for long-term objectives (7–10 years). Two parallel activities similar to those in short-term objectives is envisaged. New potential drug identified through synthesis/screening against L. donovani will be tested against isolates of Leishmania causing CL in a mouse model. Active compounds will be identified for further development and eventually tested in combined immuno-chemotherapy trials. New immuno-modulators will be tested in the B6 mouse model; however, the CpG's with human-specific motifs being developed for cancer therapy will be adopted for CL treatment.

Figure 3

Poverty and CL. Inverse relationship of incidence of CL (green diamond) to GDP/capita (black diamonds) in various states of Brazil. AC = Acre, AM = Amazonas, PA = Para, RO = Rondonia, RS = Rio Grande do Sul, SC = Santa Catarina, SP = Sao Paulo. (Adopted from A. Rabello).

Figure 4

Analyses of published clinical trials involving CL. Of 75 studies only 20 were randomized, control trial (RCT), double blind (DB) with placebo control (PC). There were 27 trials that had no control arm. For a self healing disease, a control arm is necessary if it is ethically correct. There is a need to improve the quality of clinical trials.

Figure 5

Real time quantitative measurement of L. major infection in C57/Bl mice. Mice were infected with 10⁴ luciferase – expressing L. major metacyclic promastigotes intradermally. The bio-reagent can then be measured quantitatively during the rise and fall of the parasite population at various times. (adopted from T. Lang's presentation)

Figure 6

The public health aspect of paromomycin-urea ointment. The true benefit of the paromomycin (aminocidine) ointment in ZCL patients (caused by L. major) in Isfahan, Iran. About 30–40% self heal within 5–6 months from onset of disease, With an efficacy of the ointment about 35–40%, 75–80 would cure within this period leaving 20–25% of refractory patients who would need other treatment. This figure indicates the importance of a placebo (control) arm in all CL studies. In addition, the duration of lesion prior to enrolment into any trial is critical, since with time, more and more cases self heal.

Figure 7

A patient (Afghanistan) with lupoid CL before and after DAC N-055 therapy. (Adopted from K-W Stahl, A F Jebran, F M Amin, R Steiner, A G Faramol, F Mahfuz, C Kurzmann, U Schleicher, C Bogdan – unpublished. Presented by K-W Stahl).

Figure 8

Response to topical treatment with different buparvaquones (BPQ). BALB/c mice were infected with 2 × 10⁶ L. major J118 promastigotes and 20 daily topical application began 3 days post-infection. Both a BPQ hydrous gel and a BPQ water-in-oil (w/o) emulsion significantly reduced both parasite burden (P < 0.05, 22 days post infection; as determined by real time PCR) and lesion size compared to the untreated control; P < 0.0001, 13 days post start of treatment, (adopted from T. Garnier).

Figure 9

Schematic representation of the mode of action of Imiquimod. IFN-γ = Interferon-gamma, IL-12 = Interleukin-12, MHC-II = Type 2 major histocompatibility antigen, NO = Nitrous oxide, TCR = T-cell receptor, Th1 = T-helper cell type 1, Th0 = Undifferentiated T-cells, TLR-7 = Toll like receptor-7. (presented by G. Matlashewski)

Figure 10

Response to Immunochemotherapy of CL in Peru. Double-blind randomized placebo-controlled trial of topical Imiquimod plus antimony vs placebo plus antimony. Forty subjects with clinical resistance to antimony received Sb⁺⁵ (20 mg/kg/day im or iv) and were randomized to receive either topical imiquimod 5% cream (Aldara; 3 M Pharmaceuticals) or vehicle control every other day for 20 days. With permission from Miranda et al. Clin. Infect. Dis. 2005, 40: 1395.

Figure 11

Immuno-chemotherapy of CL caused by L. braziliensis in Brazil. Double-blind controlled trial of Mayrink's vaccine (killed L. amazonensis) plus low dose (8 mg/Kg/d) Sb⁺⁵ vs. low dose Sb⁺⁵. Patients received daily injections of the combination or drug alone for 10 days followed by 10-day rest (one cycle). All patients (47/47) were cured in the combination group after 4 cycles (80 days) vs. 4/47 in the chemotherapy alone group. The non-responders were rescued with full dose antimony. (Adopted from Machado-Pinto et al. Int. J. Dermat. 2002; 41:73-8.)

Figure 12

Immuno-chemotherapy of persistent PKDL patients in Sudan. Double-blind randomized antimony alone controlled vs. immunochemotherapy trial of 30 persistent PKDL patients. All patients received the standard daily injections of Sodium Stibo-Gluconate (SSB) for 40 days. Patients were randomized to receive 4 weekly injections of alum-precipitated autoclaved L. major (alum-ALM) + one tenth of normal dose of BCG or a placebo (BCG diluent). On day 60, 87% in the combined immuno-chemotherapy group were cured and the rest improved vs. 53% in chemotherapy alone group cured and the rest failed (efficacy = 72%, 95% CI: 0.8–1.18). By day 90 all patients in immunochemotherapy had cured vs. Adopted from Musa, A. & Khalil, EAG, et al.)

Figure 13

Immunotherapy of CL lesions in macaque monkeys. Systemic administration of oligo-deoxy-nucleotide (ODN) class D/A limits the size of lesions following an intradermal infection with L. major. Importantly, the reduced morbidity was not associated with a reduction in long-term immunity, as such treated macaques were still protected following a secondary challenge. This suggests a potential role for CpG ODN in L. major treatment. These findings support the development of clinical studies to assess the use of CpG ODN types D/A as immunoprotective and therapeutic agents. (From Flyn B. et al Infect.& Immun. 73:4948, 2005 with permission)