Introduction and Background of the Project

Introduction

Schistosomiasis elimination programs urgently require new tests. Recognizing this, WHO issued two TPPs in 2021. Schistosomiasis is a WHO top-priority, surpassed in worldwide case numbers only by malaria. More than 200 million people are estimated to be affected, with 90% of cases occurring in Africa, caused by Schistosoma mansoni (intestinal disease) and Schistosoma haematobium (urogenital disease). None of the current diagnostics meets all needs. The reference test for S. mansoni – Kato-Katz stool examination – requires skilled personnel and underestimates infection prevalence due to low sensitivity. Antigen tests (CCA/CAA) are showing promise when monitoring active infection in medium-to-high endemicity settings but may be suboptimal when nearing interruption of transmission. Experts agree that serological testing of preschool-aged children offers a viable, practical, and cost-effective solution to monitor progress of schistosomiasis control and elimination programs, particularly in low-prevalence settings. In previous work (G2023-110), we developed excellent serological RDT prototypes for S. mansoni which meet all the minimal, in some cases also the ideal TPP criteria. In this follow-on project, we will progress them to the stage of being ready for subsequent regulatory review and commercialization.

Project objective

The overarching objective of this project is to deliver a fully TPP-compliant, easy-to-use, low-cost point-of-care test able to detect IgG1-type antibodies raised by the human host against selected S. mansoni antigens as an indicator for current or prior infection. The RDT delivered at the end of G2024-202 will have the required sensitivity and specificity to support decisions for Schistosomiasis Transmission Interruption and subsequent Surveillance in hypo-endemic areas post-MDA where stool-based or antigen-based diagnostics struggle to accurately determine disease prevalence. Targeting young children as sentinel groups, the RDT will mainly be used with fingerstick blood but will be designed to also work with dried blood spots, which will facilitate integration with other NTD programs conducting seroprevalence studies. Our test will come with a complete set of laboratory and field validation data generated jointly by  the Nagasaki University Institute of Tropical Medicine (NEKKEN), the Kenya Medical Research Institute (KEMRI), and the Noguchi Memorial Institute for Medical Research (NMIMR), and with an ISO13485-compliant automated large-scale, low-cost manufacturing process validated through pilot production of 3 x 10’000 tests, hence will be ready for Expert Review Panel for Diagnostics (ERPD) Review and programmatic adoption by WHO in 2027. Our RDT will be further supplemented with a heat-stable formulation of a positive control antibody that will allow end users to periodically check whether the RDT still performs to specifications, as well as with our new mobile reader app that will ensure objective result interpretation through removal of operator bias, as well as global data access, traceability and sharing.

Project design

We will pursue the following 6 specific objectives:

- Objective 1: This first activity is aimed at defining the optimal use case(s) for our new serological test: Since serological testing is a new approach for schistosomiasis control and elimination programs, this work will be modelled in as much as appropriate on other NTDs that have already incorporated serological testing in their programmatic concepts (onchocerciasis, lymphatic filariasis, trachoma). We will also finalize the study plan for the field evaluation in Kenya (Objective 5) and establish a commercialization plan for the new test.

- Objective 2: In the predecessor project, G2023-110, MBL produced the S. mansoni antigens and positive control antibodies in R&D grade quality. The production will now be moved to larger scale and ISO/QMS grade quality. Once available in sufficient amount, the positive control antibodies will be converted into a heat-stable formulation using DDTD’s proprietary technology.

- Objective 3: Given that the two prototype tests delivered at the end of G2023-110 (one for each S. mansoni antigen) already meet the TPP criteria, only limited further optimization work will be required, which may include generating and evaluating a biplex test as an alternative to the two singleplex tests. The final choice of the candidate test for further development will be based on a multi-parametric comparison of sensitivity, specificity, time-to-result, result stability, matrix equivalence, shelf life/thermal stability, and anticipated production cost. The candidate RDT will be design-locked and delivered to NUITM, KEMRI, and NMIMR for laboratory and field evaluations of its diagnostic and operational performance.

- Objective 4: NEKKEN, KEMRI and NMIMR will independently evaluate the laboratory diagnostic performance of the candidate RDT using extended patient sample panels and compare the results with egg count, PCR, CCA and/or CAA data as available, and determine the concordance with laboratory-based serological assays (ELISA/MBA).

- Objective 5: NUITM, KEMRI, and NMIMR will follow the clinical study plan established in Objective 1 to evaluate the diagnostic and operational performance of the candidate RDT in both endemic and non-endemic regions of Kenya and, potentially, Ghana. Besides sensitivity and specificity in comparison with classical stool-based methods and serological laboratory tests, the test will also be assessed for reliability and user-friendliness in low-infrastructure point-of-care settings as reported by the field workers involved in the study.

- Objective 6: A ISO13485-compliant automated large-scale manufacturing process will be developed by DDTD, modeled on those we have previously put in place for other tests. BEDx will then conduct an independent validation of the manufacturing process by producing 3 pilot lots of 10’000 units each, and quantifying the inter-lot consistency. All team members and key stakeholders (donors, WHO Schisto-DTAG) will convene to review the entire dossier compiled on the candidate RDT. The goal is to obtain a unanimous recommendation for programmatic adoption and regulatory review (if required by WHO).

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

We propose to bring to commercialization readiness a first-in-class serological RDT that leverages biomarkers used for decades at the Centers for Disease Control and Prevention (CDC) for the diagnosis of schistosomiasis. Based on a growing body of evidence gathered in schistosomiasis and other NTD programs, we believe that our serological RDT will be complementary to the antigen tests currently in development by allowing to better detect the disease in low-prevalence settings where infections will be of low-intensity, as will be the case when approaching interruption of transmission. Part of the purpose of this grant is to explore when one test will be more useful than the other, and when the combination of both tests will provide the most useful information. Because serological tests are a tried-and-true technology, and because of the excellent results obtained with our prototype RDTs under G2023-110, we are certain that a safe and affordable commercial RDT is within reach that will respond to WHO’s call for new diagnostics detailed in the TPPs. We respectfully submit that our test will address a major global health problem, insofar as it will help improve the lives of hundreds of millions of people living mostly in neglected, underprivileged regions of the world with patent schistosomiasis or the threat of newly contracting the disease.

What sort of innovation are you bringing in your project?

- Innovation 1: DDTD has introduced a novel test architecture combined with a proprietary sample pad material to further increase the sensitivity of our tests and ensure flawless behavior with blood samples (no red streaking).

- Innovation 2: DDTD has developed a novel method for rendering positive control antibodies entirely heat-stable, hence no longer requiring a cold chain for shipping or storage. Based on flash-freezing followed by freeze-drying, we have used this method to generate a positive control antibody for our onchocerciasis test and shown it to be stable at 50°C for > 2 weeks.

- Innovation 3: DDTD has developed a new smartphone-based app in collaboration with Novarum and with funding from British charity LifeArc, which provides lightning-fast data acquisition and interpretation, upload of data in a cloud-based repository, and the ability to retrieve the data in real time from a web portal which can be accessed from anywhere in the world and by anyone having been granted access. The main value of this new app consists in an increased ease of use, more objective result interpretation (removal of operator bias), and global data traceability and sharing.

Role and Responsibility of Each Partner

- Drugs & Diagnostics for Tropical Diseases (DDTD): as the Designated Development Partner, will provide management of the project and the Collaboration Partners to ensure that the deliverables and Milestones set forth in Section 3 above are met. Furthermore, DDTD will optimize and evaluate the diagnostic performance of the prototype RDTs to detect exposure to S. mansoni, and transfer the final design-locked candidate RDT to manufacturing process development. All experimental procedures, as well as chemical, biochemical, biophysical, and clinical data generated during the project will be recorded by DDTD in its ISO13845-certified quality management system.

- Medical & Biological Laboratories Co., Ltd. (MBL): will be responsible for producing S. mansoni antigens and positive control antibodies in ISO/QMS-grade quality, and for maintaining any records necessary to reproduce the expression and purification of these key biological resources in view of future ISO13485-compliant test manufacturing.

- Nagasaki University Institute of Tropical Medicine (NEKKEN): will be involved in both laboratory and field evaluations of the candidate S. mansoni RTD, and will also have major contributions to the tasks of determining the optimal use case(s) for a serological S. mansoni test, establishing the clinical study plans, and creating a commercialization plan.

- Kenya Medical Research Institute (KEMRI): will be leading the field evaluation of the candidate S. mansoni RTD in Kenya, and will have major contributions to the tasks of determining the optimal use case(s) for a serological S. mansoni test.

- Noguchi Memorial Institute for Medical Research (NMIMR): will be involved in both laboratory and field evaluations of the candidate S. mansoni RTD, and will also have major contributions to the tasks of determining the optimal use case(s) for a serological S. mansoni test and establishing the clinical study plans.

- Big Eye Diagnostics, Inc. (BEDx): will be responsible for validating DDTD’s manufacturing SOPs and QC protocols by producing 3 pilot lots of 10-20’000 S. mansoni test units and quantifying inter-lot consistency. In the long term, beyond G2024-202, BEDx will be in charge of test manufacturing and commercialization.