Clinical development of CpG-D35 for combined treatment of cutaneous leishmaniasis

Introduction and Background of the Project


Cutaneous leishmaniasis (CL) is a severely neglected tropical disease. It is endemic in 87 countries worldwide, mainly affecting poor populations in developing countries. The World Health Organization (WHO) has estimated that there are around 0.6 to 1.2 million new CL cases every year. While CL is not life-threatening, it is a disfiguring disease that results in stigma and economic loss.

Currently, there are no satisfactory treatments for any form of CL. Treatments recommended for CL have sub-optimal effectiveness and have long depended on antiquated drugs.

CpG-D35 is being developed as a combination therapy for the treatment of patients with CL. It triggers the Toll-like receptor-9 (TLR-9) expressed on plasmacytoid dendritic cells and thereby activates the innate and adaptive immune system of the host. Data generated to date support the hypothesis that CpG-D35 alone or in combination with chemotherapy will reduce infection and accelerate the healing of CL lesions, as demonstrated in preclinical studies with CpG-D35. Consequently, CpG-D35 is expected to improve CL patient care.


Project objective

This is a continuation from the project previously funded by the GHIT Fund, aiming to:

  1. Determine the safety, tolerability, pharmacokinetics (PK) and pharmacodynamics (PD) after single subcutaneous dose of CpG-D35 in heathy volunteers (HVs), compared to matching placebo (SAD study) and after multiple doses administration in subjects having active infection with L. major parasites (MAD study).
  2. Refine current active pharmaceutical ingredient (API) manufacturing process to improve efficiency/overall quality of CpG-D35 drug substance.
  3. Develop a more concentrated, affordable, and field-adapted subcutaneous dosage form for later-stage clinical trials.
  4. Further optimize the CAL-1 potency assay used for CpG-D35 quality control and stability testing.


Project design

A single ascending dose (SAD) study will be conducted in the UK. A randomized, double-blind, placebo-controlled, single-centre study with CpG-D35 administered subcutaneously to healthy subjects will aim to assess safety and tolerability of CpG-D35 after single dose compared to a matching placebo. As secondary objectives, PK and PD of CpG-D35 after single dose will be investigated, including but not limited to changes in cytokine levels in plasma over time as PD markers.

If no safety concerns are encountered during the SAD study, then a Phase Ib, multiple ascending dose (MAD) study will be implemented. It will be a randomized, double-blind, placebo-controlled, multiple-dose escalation study to investigate safety, tolerability, and immunogenicity of CpG-D35 in patients with CL lesions due to L. major. The study will be performed in a single-site hospital specialized in Phase Ib studies in Turkey. Secondary objectives of this study are: 1) Assess PK and PD of CpG-D35; 2) Characterize the immune response produced by CpG-D35 in L. major infected patients; 3) Determine the value of using CXCL10 as PD marker; and 4) Establish CL lesions’ time to heal after multiple doses of CpG-D35.

Refinement of the current API manufacturing process will include optimization of the coupling step and washing step(s), change to other sulfurizing reagents, and preparation of a demonstration batch. To assess the feasibility of producing a more concentrated liquid formulation, the ease with which current liquid clinical formulation can be reconstituted after lyophilisation with lower volumes will also be evaluated. Different excipients will be screened in parallel to provide solutions that can be reconstituted to tonicity. The in vitro CAL-1 cell-based potency assay will also be refined.

How can your partnership (project) address global health challenges?

CL is one of the 20 neglected tropical diseases (NTDs) included in the WHO Road Map for NTDs 2021-2030, which aims to align efforts across stakeholders and bring focused attention to the fight against NTDs, including the prevention, control, elimination, and eradication of these diseases to achieve the UN Sustainable Development Goals.

There are few drugs available for the treatment of CL and all have significant side effects. Pentavalent antimonials – either sodium stibogluconate or meglumine antimoniate – have been used since the 1940s but remain the recommended drugs for the treatment of all forms of CL despite their toxicity and difficulty of administration, and despite concerns over their efficacy in many regions affected by CL.

The expectation based on preclinical data is that combining CpG-D35 with chemotherapy for the treatment of patients with CL will speed lesion re-epithelization, minimize scarring, reduce the rate of relapse, and hopefully reduce the risk of developing drug resistance1,2,3. Furthermore, a combined treatment with CpG-D35 plus an antiparasitic drug will benefit patients with complicated CL disease, such as patients with large or multiple lesions, patients who do not respond to standard-of-care treatment or who show relapses, or patients with lesions due to L. braziliensis or L. tropica, where the standard treatment has limited efficacy (<60% cure rate) or requires multiple rounds of therapy.

What sort of innovation are you bringing in your project?

Our proposed approach is clearly differentiated from the current treatment recommendations for CL. Developing a novel D class CpG to promote the immune response required for the control of Leishmania infection, in combination with chemotherapy, will provide a major step forward over existing monotherapies or combination therapies targeting the parasite only.

Conventional chemotherapy of CL aims to kill most of the Leishmania parasites, thereby reducing the burden of infection, and it is hypothesized that by promoting the appropriate immune response in the host, the immune system will be able to limit and remove any remaining parasites. Fostering an effective immune response by the host has been shown to improve control of parasites and determine the clinical outcome of subjects infected with Leishmania parasites.

CpG-D35 triggers the Toll-like receptor-9 (TLR-9) expressed on plasmacytoid dendritic cells and thereby activates the innate and adaptive immune system of the host. The very specific stimulation of the immune response fosters innate immune activation favouring the Th1 type responses known to be essential for clearing parasites and may hasten lesion repair. We hypothesize CpG-D35 alone or in combination with chemotherapy will reduce infection and accelerate the healing of CL lesions, as shown in preclinical studies with CpG-D35. In humans, the expectation based on preclinical studies is that a combined treatment will speed re-epithelization of lesions, minimize scarring, reduce the rate of relapses or re-infections, and reduce the risk of developing drug resistance1,2,3.

Moreover, addition of CpG-D35 to the therapeutic regimen will provide optimal treatment choices to benefit patients and ultimately control the disease.

Role and Responsibility of Each Partner

DNDi will have overall responsibility for project management and coordination and will conduct procurement to select CROs.

The SAD study will be conducted by a CRO with expert advice from consultants. For the MAD study, a hospital-based study site coordinated and supervised by a CRO specialized in this type of study will organize the study with expert advice from DNDi, The University of Tokyo, and other consultants. The University of Tokyo will provide technical support and expertise for the selection of the study site, as well as oversee the analysis and interpretation of the immunological markers collected from subjects through the duration of the study.

Ajinomoto Bio-Pharma Services, GeneDesign (GeneDesign) will use its expertise in designing, processing, developing, and mass producing oligonucleotides. In particular, GeneDesign will continue the development of the CpG-D35 manufacturing process. Formulation development and clinical supplies suitable for Phase I & II clinical studies will be outsourced to a CDMO specialized in parenteral formulations. Further optimization of the CAL-1 potency assay will be conducted at Intertek with expert advice from consultants.

The project will be overseen by the CpG-D35 Advisory Committee, comprised of appropriate senior representatives of DNDi, The University of Tokyo, GeneDesign, and relevant consultant(s). It will convene at least every 6 months by tele/video conference and no less than once per year in a face-to-face meeting. The role of the CpG-D35 Advisory Committee is to provide guidance and monitor progress against the project plan and to ensure that adequate resources have been assigned to the project.

Others (including references if necessary)

1. Flynn B, Wang V, Sacks DL, Seder RA, Verthelyi D. 2005. Prevention and treatment of cutaneous leishmaniasis in primates by using synthetic type D/A oligodeoxynucleotides expressing CpG motifs. Infect Immun;73(8):4948-54.

2. Verthelyi D, Gursel M, Kenney RT, Lifson JD, Liu S, Mican J, Klinman DM. 2003. CpG oligodeoxynucleotides protect normal and SIV-infected macaques from Leishmania infection. J Immunol; 170(9):4717-23.

3. Miranda-Verastegui C, Tulliano G, Gyorkos TW, Calderon W, Rahme E, Ward B, Cruz M, Llanos-Cuentas A, Matlashewski G. 2009. First-line therapy for human cutaneous leishmaniasis in Peru using the TLR7 agonist imiquimod in combination with pentavalent antimony. PLoS Negl Trop Dis; 3(7):e491. doi: 10.1371/journal.pntd.0000491