Limoges University Hospital's Sodium Thiosulfate Subcutaneous Injection for Ectopic Calcification Enters Phase 2 Clinical Trial
High Unmet Medical Need for Calcification in Rare Autoimmune Diseases
Ectopic calcification, a severe complication characterized by abnormal calcium crystal deposition in tissues, occurs in patients with dermatomyositis and systemic sclerosis. This condition causes severe pain, tissue necrosis, and impaired bodily functions. Currently, there are no FDA-approved disease-modifying agents specifically for this condition. Existing treatments rely on off-label use of bisphosphonates or diltiazem, a calcium channel blocker, or are limited to invasive surgical removal of severely affected areas. Therefore, securing an innovative drug treatment option that is non-invasive and can directly dissolve calcified lesions has become an urgent task for the biopharmaceutical industry.
Drug Repurposing of Sodium Thiosulfate and Local Subcutaneous Administration Strategy
The research team at the University Hospital, Limoges, France, is pursuing a drug repurposing strategy, focusing on the calcium-chelating properties of sodium thiosulfate (STS), which has been used as an antidote for cyanide poisoning and to prevent cisplatin toxicity. Sodium thiosulfate works by binding to calcium crystals in tissues, forming water-soluble sodium thiosulfate complexes, thereby chemically dissolving calcified lesions. Previous systemic intravenous administration had limitations due to systemic side effects and low local delivery efficiency. However, this clinical trial adopts a local subcutaneous injection method to maximize drug efficacy by directly administering it to the affected area. This modification in formulation and administration route offers significant advantages in terms of reducing costs and time compared to developing new drugs.
Precise Phase 2 Clinical Trial Design and Evaluation Metrics
This Phase 2 clinical trial (NCT03582800) is a multi-center, exploratory study conducted on patients with dermatomyositis, systemic sclerosis, and type 2 inactivating PTH/PTHrP signaling disorder (iPPSD2). Trial participants undergo a six-month observation period before treatment to establish baseline data on calcification progression using computed tomography (CT). They then receive periodic local subcutaneous injections of 10% sodium thiosulfate for six months. The clinical research team measures the reduction rate of calcified volume using three-dimensional image analysis and quantitatively evaluates changes in patients' pain index (VAS) and quality of life (QoL). This sophisticated quantitative trial design aims to clearly demonstrate the clinical utility of the drug beyond simply verifying its safety.
Paradigm Shift in Non-Invasive Treatment and Commercial Impact
If the efficacy of sodium thiosulfate subcutaneous injection is proven in this Phase 2 clinical trial, the treatment paradigm for calcification, which has been centered on invasive surgical procedures, is expected to fundamentally shift to a non-invasive outpatient injection therapy. The possibility of obtaining orphan drug designation through drug repurposing opens up commercial opportunities, including development exclusivity and fast-track review benefits. Given that the global systemic sclerosis treatment market is projected to reach approximately $2.7 billion in 2025 and there is a high unmet need in the rare disease area, the results of this study are expected to be a catalyst for increasing the interest of global pharmaceutical companies in licensing and expanding their autoimmune disease pipelines.
In the absence of FDA-approved therapies for calcinosis cutis, the Phase 2 clinical trial (NCT03582800) of sodium thiosulfate (STS) subcutaneous injection by the University Hospital, Limoges, represents a critical milestone in developing a non-invasive standard of care to replace surgical resection and off-label bisphosphonates. By leveraging the drug repurposing approach and transforming STS, previously used as a cisplatin toxicity antidote, into a calcium-chelating agent, the development costs of new drugs are reduced, and the potential for obtaining orphan drug designation and associated development exclusivity is secured. With the global systemic sclerosis treatment market projected to reach approximately $2.7 billion (USD) by 2025 and the dermatomyositis treatment market at $1.3 billion (USD), the results of this exploratory clinical trial will serve as a benchmark for re-evaluating the value of target rare disease pipelines. In the long term, the demonstration of precise, imaging-based data on calcified volume reduction is expected to lead to active discussions on technology transfer (L/O) and commercial licensing agreements with global major pharmaceutical companies.
Source: ClinicalTrials.gov (api_ct)