DiscoveryProbe™ FDA-approved Drug Library: High-Throughput Screening for Drug Repositioning and Target Identification

Executive Summary: The DiscoveryProbe™ FDA-approved Drug Library (L1021) from APExBIO comprises 2,320 bioactive compounds, each approved by major global regulatory agencies for clinical use (product page). Compounds are provided as 10 mM DMSO solutions, stable for up to 12 months at -20°C and 24 months at -80°C. The library supports high-throughput screening (HTS) and high-content screening (HCS) for drug repositioning, novel target identification, and mechanistic studies (Terawaki et al., 2025). Established research demonstrates its utility in areas such as cancer, neurodegenerative disease, and rare lysosomal storage disorders. The resource accelerates translational research by reducing lead identification time and enabling mechanistic validation (contrast).

Biological Rationale

Drug discovery is hindered by high attrition rates and lengthy development timelines. Repositioning clinically approved compounds shortens these cycles by leveraging known safety and pharmacodynamic profiles. The DiscoveryProbe™ FDA-approved Drug Library aggregates 2,320 compounds that have been approved by regulatory agencies including the FDA, EMA, HMA, CFDA, and PMDA or are listed in major pharmacopeias (APExBIO product page). Such libraries offer a verified starting point for phenotypic screening and mechanistic interrogation. For example, recent studies have identified triclabendazole—a compound present in this library—as a candidate for treatment of mucopolysaccharidosis-plus syndrome (MPSPS), a rare lysosomal storage disorder (Terawaki et al., 2025).

This approach is especially valuable for diseases with unmet therapeutic needs, such as rare genetic disorders, cancer, and neurodegenerative diseases. By enabling systematic interrogation of clinically validated chemical space, the DiscoveryProbe™ FDA-approved Drug Library supports rapid hypothesis testing and target validation.

Mechanism of Action of DiscoveryProbe™ FDA-approved Drug Library

The library encompasses diverse mechanisms of action, including:

• Receptor agonists and antagonists (e.g., propranolol, metoprolol)
• Enzyme inhibitors (e.g., atorvastatin, doxorubicin)
• Ion channel modulators (e.g., amlodipine)
• Signal transduction pathway regulators (e.g., sorafenib)

Each compound’s mechanism, clinical indication, and target class are annotated based on regulatory documents and peer-reviewed literature. The inclusion of drugs targeting G-protein coupled receptors, kinases, nuclear hormone receptors, and ion channels facilitates pathway mapping and functional genomics studies (see contrast: mechanistic focus). For instance, the identification of triclabendazole as an inhibitor of glycosaminoglycan accumulation in MPSPS models demonstrates the utility of mechanism-agnostic screening (Terawaki et al., 2025).

Evidence & Benchmarks

• The DiscoveryProbe™ FDA-approved Drug Library enabled the identification of triclabendazole as a lead compound reducing intracellular glycosaminoglycan levels in MPSPS model cells (Terawaki et al., 2025, DOI).
• Library compounds are provided in 10 mM DMSO stock solutions, validated for stability for 12 months at -20°C and up to 24 months at -80°C (APExBIO, specification).
• HTS using this library supports robust hit rates across diverse disease models, including oncology and neurodegenerative diseases (application summary).
• Compounds are pre-dissolved and aliquoted in 96-well, deep-well plates, and 2D barcoded storage tubes, compatible with automation (workflow extension).
• Shipping validated at both room temperature and on blue ice, ensuring compound integrity during transit (APExBIO, logistics).

Applications, Limits & Misconceptions

This library is optimized for:

• Drug repositioning studies in cancer, neurodegeneration, and rare diseases
• Pharmacological target identification and signal pathway mapping
• Combination screening for synergistic or additive effects
• Validation of disease models via phenotypic screening

For example, screening this library enabled the identification of triclabendazole as a modulator of glycosaminoglycan metabolism in MPSPS, a disease for which no targeted therapy previously existed (Terawaki et al., 2025).

Compared to non-curated compound collections, this library provides a higher probability of clinical translation due to the known pharmacology and toxicity profiles of included molecules (combination therapy strategies). This extends previous work by providing mechanistic annotations and standardized formats that ensure reproducibility in HTS/HCS platforms.

Common Pitfalls or Misconceptions

• Not all compounds are suitable for every disease model: Mechanistic fit and model compatibility must be evaluated prior to screening.
• Hit identification does not guarantee clinical efficacy: Further validation in relevant in vivo models is essential.
• DMSO sensitivity: Some cell types or assays are incompatible with DMSO concentrations above 0.5% v/v.
• Intellectual property (IP) constraints: While compounds are clinically approved, repurposing for new indications may face patent or regulatory hurdles.
• Compound stability post-thaw: Repeated freeze-thaw cycles may reduce compound integrity; single-use aliquots are preferred.

Workflow Integration & Parameters

The DiscoveryProbe™ FDA-approved Drug Library is designed for seamless integration into automated HTS and HCS pipelines. Key workflow parameters include:

• Format: 10 mM DMSO solutions in 96-well or deep-well plates, or 2D barcoded tubes
• Storage: -20°C (12 months), -80°C (24 months)
• Shipping: Blue ice for evaluation samples; room temperature or blue ice for bulk shipments
• Assay compatibility: Validated for cell-based, biochemical, and phenotypic assays
• Data integration: Each compound is annotated with clinical indication, target, and mechanism for informatics workflows

Researchers can integrate this resource into multi-omics and functional genomics pipelines for comprehensive target validation. The library's standardized solutions and barcoded formats support traceability and reproducibility, extending the findings of prior translational research (strategic deployment).

Conclusion & Outlook

The DiscoveryProbe™ FDA-approved Drug Library (L1021) from APExBIO provides a rigorously curated, mechanistically diverse set of compounds for HTS and HCS applications. Its proven use in identifying new therapeutic applications—such as the repositioning of triclabendazole for MPSPS—demonstrates its value across disease domains. This library accelerates discovery, enhances reproducibility, and supports translational success in modern biomedical research. For details and ordering, see the DiscoveryProbe™ FDA-approved Drug Library product page.