Purpose

Define user requirements for a standalone FUZKK utility that accepts laboratory CSV data, evaluates the records using limits embedded in code, and produces LabWare-compatible JSON.

Scope

The utility is intended for preliminary QC/QA review, integration testing, LIMS/LabWare flow and evidence-trail preparation. Final release decisions remain under the laboratory's validated procedure and responsible personnel.

Users

QC analyst, QA reviewer, CSV/validation engineer, LIMS/LabWare integration engineer, responsible laboratory specialist.

User requirements

1. The utility shall run without arguments and print its self-description, a built-in input.csv example from GetDemoData(), and demo evaluation for the embedded records.
2. The utility shall run with two arguments: input.csv output.json.
3. The utility shall not read input.csv and shall not write output.json when started without arguments.
4. CSV numeric values shall be parsed using CultureInfo.InvariantCulture.
5. Output shall be generated as LabWare-compatible JSON with Header, Samples, Results, Status, StatusCode, ErrorMessage, Description and DescriptionEN.
6. For PASS records, ErrorMessage shall be an empty string.
7. Embedded limits shall follow this priority: Ph. Eur. → British Pharmacopoeia / UK implementation → EAEU / regional requirements → EMA/ICH/EU guidance → USP fallback.
8. If an exact monograph is not known, strict standard API limits are used where applicable: assay 98–102%, total impurities ≤1.0%, individual impurity ≤0.5%.
9. For biologics and mAb-like products, aggregation, sterility and endotoxin checks shall be included where relevant to the utility purpose.
10. If a parameter may arrive in different units, the unit shall be represented as a separate input field or explicitly reflected in the input.csv field name.

Input CSV

BatchNumber,ADCName,LinkerType,PlasmaStability_HalfLife_h,LysosomalRelease_Rate_h,PrematureCleavage_Percent,StorageStability_Months,IntactADC_Percent_24h,Medium
ADC-LS-2026-001,Trastuzumab-Deruxtecan,GGFG (Cleavable),120.0,15.0,3.5,24.0,96.5,Human Plasma
ADC-LS-2026-002,Sacituzumab-Govitecan,CL2A (Cleavable),72.0,12.0,8.0,18.0,92.0,Human Plasma
ADC-LS-2026-003,T-DM1,SMCC (Non-cleavable),200.0,2.0,1.0,36.0,99.0,Human Plasma

input.csv fields

Utility description

ADC Linker Stability Profiler — ADC Linker Stability Profiler

ADC Linker Stability Profiler — ADC Linker Stability Profiler

ℹ️ Utility evaluates linker kinetics and stability:
• Plasma half-life (≥48 h)
• Lysosomal release rate (≥5 %/h)
• Premature cleavage (≤10%)
• Intact ADC at 24h (≥90%)
• Predicted shelf life (≥12 months)

⚠️ CRITICAL: Balance between blood stability and tumor release!
Unstable linker = systemic toxicity.
Too stable linker = lack of efficacy.

Usage:
ADCLinkerStabilityProfiler.exe → demo mode (console output)
ADCLinkerStabilityProfiler.exe input.csv output.json → evaluate your data

Input format:
BatchNumber,ADCName,LinkerType,PlasmaStability_HalfLife_h,LysosomalRelease_Rate_h,PrematureCleavage_Percent,StorageStability_Months,IntactADC_Percent_24h,Medium

Example:
ADC-LS-2026-001,Trastuzumab-Deruxtecan,GGFG (Cleavable),120.0,15.0,3.5,24.0,96.5,Human Plasma

— WHY IS THIS NEEDED?
Linker determines therapeutic window of ADC (Hengrui, BeiGene, Hansoh):
• Must be stable in systemic circulation to prevent "off-target" toxicity
• Must efficiently cleave inside tumor cell (lysosome/cytoplasm) to release toxin
• Cleavable linkers (Val-Cit, GGFG) enable bystander killing effect
• Non-cleavable linkers (SMCC) require complete antibody degradation in lysosome

⚠️ CRITICAL:
• Plasma T1/2 ≥48 h — ensures drug delivery to tumor
• Release rate ≥5 %/h — guarantees effective cytotoxicity
• Premature cleavage ≤10% — minimizes systemic toxicity of free toxin
• Intact ADC ≥90% (24h) — confirms stability in biological media
• Shelf life ≥12 months — commercial product viability

Key features:
• Cleavage kinetics assessment in different media (plasma, lysosome)
• Stability/efficacy balance control
• Shelf life prediction based on accelerated stability
• Support for various linker types (cleavable/non-cleavable)

Critical parameters:
• Plasma T1/2: ≥48 h
• Lysosomal release: ≥5 %/h
• Premature cleavage: ≤10%
• Intact ADC (24h): ≥90%
• Shelf life: ≥12 months

💡 Usage tips:
1. Use LC-MS to monitor appearance of free toxin over time
2. Test stability in human and mouse plasma (species differences in enzymes!)
3. For cleavable linkers check specificity to cathepsin B or other proteases
4. Compare stability profiles at pH 7.4 (blood) and pH 5.0 (lysosome)
5. If high premature cleavage observed, consider linker replacement or stabilizing mutations

⚠️ Note: Linker stability is the main factor distinguishing successful ADCs from failed ones. Historically many candidates failed in clinic due to linker instability in human plasma (despite good stability in mouse plasma). The utility helps identify such risks at preclinical stage.

Traceability and limitations

• The URS is used as the source document for functional specification, CSV review and later validation work.
• This document does not replace an approved pharmacopoeial monograph, validated analytical method or internal product specification.
• For product-specific limits, the approved customer specification takes priority.

The functional specification describes the behaviour of the standalone FUZKK console utility, input-data format, evaluation algorithm and output JSON structure.

Functional flow

1. Main() checks the number of arguments.
2. If no arguments are provided: PrintHello() prints the description and built-in input.csv example, then RunDemoEvaluation() executes Evaluate() over GetDemoData() and prints demo JSON.
3. If two arguments are provided: RunWithFiles(input.csv, output.json) reads CSV, evaluates each record and writes LabWare-compatible JSON.
4. LoadData() uses CultureInfo.InvariantCulture and shall not be called in no-arguments mode.
5. Evaluate() returns a named tuple with BatchNumber, ProductName, Parameters, CriticalFailCount, WarningCount, Recommendation and RecommendationEN.
6. GetIssues() builds messages for ErrorMessage in WARNING/FAIL cases.

Evaluation rules

• PASS: CriticalFailCount = 0 and WarningCount = 0.
• WARNING: CriticalFailCount = 0 and WarningCount > 0.
• FAIL: CriticalFailCount > 0.
• ERROR: exception during reading or processing.
• ErrorMessage remains empty for PASS.
• Limits are embedded in Program.cs; no external limit configuration is required.

Input and fields

BatchNumber,ADCName,LinkerType,PlasmaStability_HalfLife_h,LysosomalRelease_Rate_h,PrematureCleavage_Percent,StorageStability_Months,IntactADC_Percent_24h,Medium
ADC-LS-2026-001,Trastuzumab-Deruxtecan,GGFG (Cleavable),120.0,15.0,3.5,24.0,96.5,Human Plasma
ADC-LS-2026-002,Sacituzumab-Govitecan,CL2A (Cleavable),72.0,12.0,8.0,18.0,92.0,Human Plasma
ADC-LS-2026-003,T-DM1,SMCC (Non-cleavable),200.0,2.0,1.0,36.0,99.0,Human Plasma

Output JSON

{
  "Header": {
    "UtilityName": "ADC_LinkerStability_Profiler",
    "Version": "1.0.0",
    "Timestamp": "UTC",
    "InstrumentID": "FUZKK-QC-WORKSTATION",
    "OperatorID": "Admin"
  },
  "Samples": [
    {
      "SampleID": "from BatchNumber",
      "BatchNumber": "from CSV",
      "ProductName": "from CSV",
      "TestName": "utility-specific test",
      "AnalysisCode": "utility-specific code",
      "Status": "PASS | WARNING | FAIL | ERROR",
      "StatusCode": "1 | 2 | 0 | -1",
      "ErrorMessage": "",
      "Description": "Russian recommendation",
      "DescriptionEN": "English recommendation",
      "Results": [
        {
          "ParameterName": "parameter",
          "ResultValue": 0.0,
          "UnitOfMeasure": "unit",
          "SpecificationLimit": "limit",
          "IsWithinSpec": true
        }
      ]
    }
  ]
}