Introduction and Background of the Project

Introduction

Strongyloidiasis is a neglected tropical disease (NTD) caused by the parasitic roundworm Strongyloides stercoralis, which inhabits the mucosa of the small intestines in infected individuals. As S. stercoralis can infect people through contact with contaminated soil or water, it is commonly included among the soil-transmitted helminths (STHs). Strongyloidiasis is present in more than 70 countries worldwide, including some high-income countries, and may affect up to 600 million people globally, according to some estimates. If left untreated, strongyloidiasis can have different manifestations, ranging from subclinical to severe, and may even lead to fatal complications in immunosuppressed people. Despite these alarming facts, strongyloidiasis has remained ‘the silent NTD’, with little attention in epidemiological surveys or control programs, largely due to the complexities in accurate diagnosis and the lack of a gold-standard diagnostic method. Moreover, the widely used mass drug administration (MDA) targeting STH infection (i.e., single-dose albendazole or mebendazole) has no, or only very low, efficacy against Strongyloides spp., thus the infection has largely remained unchecked. Recognizing this, the WHO issued a guideline on preventive chemotherapy with ivermectin for public health control of strongyloidiasis in July 2024, followed by a target product profile (TPP) for S. stercoralis diagnostics, which was published for public consultation in May 2025. Releasing a TPP is the strongest signal the WHO can give to underline the urgency of developing new diagnostics and making them available to strongyloidiasis control programs.

Project objective

The overarching goal of this project is to deliver an easy-to-use, low-cost point-of-care test to detect S. stercoralis infection. The new test, termed S. stercoralis Rapid Test Plus (SsRT+), will be an improved version of SsRapid, which was developed and validated by the Consultant, Prof. R. Noordin, and has been shown to be 80-97% sensitive and 90-100% specific in a series of laboratory and field studies. A first SsRT+ prototype has already been generated, which showed diagnostic performance comparable to, or better than, SsRapid. SsRT+ will be fully optimized in this project to meet all key criteria of the new TPP for S. stercoralis diagnostics. SsRT+ will come with a complete set of diagnostic performance data generated in a large, multi-center study involving two independent laboratories (UKM, IRCCS) and two field evaluations, in Australia (QIMR Berghofer) and Argentina (Mundo Sano), as well as a high-throughput, automated ISO-13485 compliant manufacturing process. Thus, at the end of the proposed project, SsRT+ will be ready for regulatory review and approval by the Expert Review Panel for Diagnostics (ERPD), followed by programmatic adoption by the WHO and commercialization starting in 2028. Designed for use with blood (fingerstick or venous), serum/plasma, or dried blood spot (DBS) in countries with limited or no technical infrastructure, SsRT+ will address an urgent unmet need of WHO strongyloidiasis control programs.

Project design

- Objective-1: This first activity aims to review the optimal use case(s) and define the key experimental data to be generated with SsRT+ to align with the WHO strongyloidiasis control programs. The project team will also finalize the study plans for the field evaluations in Australia and Argentina and complete a business/commercialization plan.

- Objective-2: Having access to high-quality antigens and positive control antibodies is key for efficient test development, optimization, and manufacturing under ISO-13485:2016 standards. As for all our other GHIT Fund projects, MBL will be entrusted with the production of high-quality recombinant NIE and IgG4-anti-NIE.

- Objective-3: The SsRT+ prototype available at the outset of G2025-101 will be fully optimized, according to all key criteria listed in the TPP for S. stercoralis diagnostics, including sensitivity, specificity, time to result, result stability, reproducibility (CV values), and cost. Since the precursor of SsRT+, SsRapid, already meets most of the TPP criteria, the project team considers this a very realistic objective.

- Objective-4: Prof. R. Noordin of Universiti Kebangsaan Malaysia (UKM), who has developed and validated SsRapid in numerous laboratory and field studies, and Prof. D. Buonfrate of IRCCS Sacro Cuore Don Calabria Hospital, who has previously run an in-depth diagnostic accuracy study involving SsRapid, will independently evaluate the diagnostic performance of SsRT+ to demonstrate that it complies with the TPP and is not inferior to SsRapid.

- Objective-5: Once validated for TPP-compliant performance in the laboratory, SsRT+ will be evaluated in two field studies in Australia and Argentina, conducted by the groups of Prof. D. Gray of QIMR Berghofer and Prof. A. Krolewiecki of Mundo Sano, respectively.

- Objective-6: An ISO-13485:2016 compliant automated manufacturing process commensurate with the anticipated demand will be developed by DDTD, modeled on the one the project team successfully puts in place for the Onchocerciasis rapid test in the GHIT Fund project G2023-111, and subsequently validated by BEDx through production of several pilot lots and quantification of inter-lot consistency.

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

In 2020, the WHO included strongyloidiasis in the 2030 targets for STH control programs, and in 2024, released a new guideline on MDA with ivermectin for public health control of strongyloidiasis. MDA programs critically depend on the availability of reliable, low-cost, point-of-care diagnostics to guide programmatic decision-making; however, all the existing Strongyloides diagnostic tools present some limitations. Recognizing this, WHO published a TPP for S. stercoralis diagnostics for public consultation earlier this year. The new rapid test (SsRT+) the project team proposes to progress to commercialization readiness in this project is well poised to become the first test to meet all criteria defined in the TPP for S. stercoralis diagnostics. Four of this project team members are already actively involved in strongyloidiasis control programs, and the project team also has the support of a key stakeholder, Dr. Patrick Lammie, Head of COR-NTD and Chairman of the WHO-DTAG, all of whom will ensure that this project will stay aligned with the strongyloidiasis WHO Global Strategy and programmatic needs at all times.

What sort of innovation are you bringing in your project?

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

- Innovation 2: In an earlier GHIT Fund project (G2023-111), DDTD and MBL identified a new anti-human-IgG4 secondary antibody which, when conjugated to the detector particles, showed superior performance compared to the best commercial products. This new antibody has already been introduced into three other DDTD rapid tests and will also be used for SsRT+.

- Innovation 3: DDTD has developed a novel method for rendering positive control antibodies entirely heat-stable, thereby eliminating the need for a cold chain for shipping or storage. Utilizing flash-freezing and freeze-drying, this new method has already been used to generate a positive control antibody for the onchocerciasis test, which was shown to be stable at 50°C for over two weeks. The project team will use the same technology to produce a heat-stable formulation of the IgG4-anti-NIE positive control antibody that will be generated by MBL.

- Innovation 4: DDTD has developed a new smartphone-based reader 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 principal value of this new app lies in an increased ease of use, more objective result interpretation (removal of operator bias), and global data integration, traceability and sharing.

Role and Responsibility of Each Partner

- Drugs & Diagnostics for Tropical Diseases (DDTD) will provide project management and collaborate with partners to ensure all Milestones are met. Furthermore, DDTD will optimize and evaluate the diagnostic performance of the SsRT+ prototypes and transfer the final design-locked candidate rapid test to manufacturing process development. All experimental procedures, as well as chemical, biochemical, biophysical, and clinical data, will be recorded by DDTD in its ISO-13845:2016 certified quality management system.

- Medical & Biological Laboratories Co., Ltd. (MBL) will be responsible for producing S. stercoralis antigen rNIE and an IgG4-anti-NIE positive control antibody, as well as maintaining any records necessary to reproduce the expression and purification of these key biological resources in view of future ISO-13485 compliant test manufacturing.

- IRCCS Sacro Cuore Don Calabria Hospital (IRCCS) will evaluate the diagnostic performance of SsRT+ using a unique sample collection from individuals infected with S. stercoralis and other parasites, especially helminths, including filarial species, Schistosoma spp, Toxocara spp, and soil-transmitted helminths, as well as intestinal protozoa, Plasmodium spp, Toxoplasma gondii, and others.

- QIMR Berghofer Medical Research Institute (QIMR) will lead the field evaluation of SsRT+ in baseline and follow-up surveys in Australia involving around 1,400 indigenous individuals from the remote endemic regions of Milingimbi and Gapuwiyak.

- Mundo Sano will lead the field evaluation of SsRT+ in Argentina, involving around 300 individuals from the regions of Orán (Salta) and Iguazú (Misiones).

- Big Eye Diagnostics, Inc. (BEDx) will be responsible for validating DDTD’s manufacturing SOPs and QC protocols by producing three pilot lots of 10-20’000 units of SsRT+ and quantifying inter-lot consistency. In the long term, BEDx will become the manufacturer of SsRT+.

In addition to the referenced Collaboration Partners, Prof. R. Noordin, the developer of SsRapid and a world-renowned expert in strongyloidiasis, is the key consultant and a full member of the team.