addresses relevant pharmacokinetic questions and drug safety concerns.

Laboratory Technicians: Execute the study protocol, including administering the drug to animals, collecting tissue samples, and monitoring animal health.

Data Analysts: Analyze biodistribution data to determine drug concentration in various tissues and organs, interpret the results, and assist in reporting.

Quality Assurance (QA): Ensure that the study complies with Good Laboratory Practice (GLP) and regulatory requirements, and that data are accurately recorded and reported.

4) Procedure

The following steps outline the procedure for conducting biodistribution studies:

1. Step 1: Study Design and Protocol Development
   1. Define the study objectives, which should include identifying the distribution of the drug or its metabolites in various tissues and organs at specified time points.
   2. Develop the study protocol, specifying animal models (e.g., rats, mice), drug dosing regimens, sample collection time points, and organs to be analyzed (e.g., liver, kidneys, brain, lungs, blood, etc.).
   3. Determine appropriate analytical methods for detecting and quantifying drug concentrations in tissues (e.g., radioisotope labeling, mass spectrometry, liquid chromatography).
2. Step 2: Ethical Approval
   1. Submit the study protocol for ethical review by the Institutional Animal Care and Use Committee (IACUC) or relevant ethics committee to ensure compliance with animal welfare regulations.
   2. Ensure that the study design minimizes animal suffering and includes appropriate controls, and that the housing and care of animals follow regulatory guidelines.
3. Step 3: Animal Selection and Grouping
   1. Select appropriate animal models based on the study objectives and the anticipated drug’s pharmacokinetic profile. Commonly used species include rodents (rats, mice) for initial studies and larger animals (dogs, rabbits) for later-stage studies.
   2. Randomly assign animals to control and treatment groups, ensuring that each group is large enough to provide statistically significant data.
   3. Ensure that animals are healthy and free from disease prior to the study and are housed under appropriate conditions with access to food and water.
4. Step 4: Dosing and Monitoring
   1. Administer the drug candidate to the animals according to the dosing regimen specified in the study protocol. This could involve different routes of administration such as oral, intravenous, or subcutaneous.
   2. Monitor animals closely throughout the study period for clinical signs of toxicity or adverse effects, and record any observations of abnormal behavior or changes in health.
5. Step 5: Tissue Sample Collection
   1. At predetermined time points, euthanize the animals humanely according to IACUC-approved protocols.
   2. Collect tissues and organs (e.g., liver, kidney, lung, brain, muscle, blood) as per the study protocol, ensuring that samples are collected consistently and stored appropriately.
   3. Record the weight of organs and any visible signs of pathological changes during necropsy.
6. Step 6: Data Collection and Analysis
   1. Analyze the collected tissue samples to measure the concentration of the drug or its metabolites using the specified analytical method (e.g., liquid chromatography, mass spectrometry, radioisotope tracing).
   2. Perform pharmacokinetic analysis on the data to determine the distribution of the drug across different tissues and organs over time.
   3. Use statistical analysis to compare the drug concentrations in various tissues and correlate these with observed effects or toxicity.
7. Step 7: Reporting and Documentation
   1. Prepare a detailed study report summarizing the methodology, results, and conclusions of the biodistribution study. Include data on drug concentrations in tissues, time points of sampling, and any observed tissue-specific effects.
   2. Ensure that the report clearly presents the biodistribution data, including tables and graphs showing drug concentration in different organs and tissues over time.
   3. Discuss the implications of the findings for drug development, including insights into the drug’s pharmacokinetic profile and potential target organs or tissues.
8. Step 8: Archiving of Study Data
   1. Ensure that all raw data, analysis results, and study reports are archived in compliance with GLP standards.
   2. Store archived materials securely and ensure they are accessible for future reference, audits, or regulatory review.
9. Step 9: Sample Disposal
   1. Dispose of all biological samples, chemicals, and laboratory waste in accordance with biosafety and waste disposal regulations.
   2. Ensure that all hazardous materials are disposed of in designated biohazard or chemical waste containers to minimize environmental impact.

5) Documents

The following documents should be maintained during the biodistribution study process:

1. Study Protocols
2. Raw Data Logs
3. Sample Collection and Tissue Analysis Logs
4. Study Reports
5. Animal Health and Welfare Logs
6. Deviations and Justifications
7. Waste Disposal Records

6) Abbreviations

• GLP: Good Laboratory Practices
• FDA: Food and Drug Administration
• PK: Pharmacokinetics
• PD: Pharmacodynamics
• IACUC: Institutional Animal Care and Use Committee
• QA: Quality Assurance

7) References

References to regulatory guidelines and scientific literature that support this SOP:

• OECD Principles of Good Laboratory Practice (GLP)
• FDA Guidelines for Pharmacokinetic and Biodistribution Studies
• ICH Guidelines for Preclinical Safety Testing
• International Guidelines on Animal Testing and Welfare

8) Version

Version 1.0: Initial version of the SOP.

9) Annexure

Biodistribution Study Report Template

Study ID	Study Title	Study Director	Study Start Date	Study End Date