Standard Operating Procedure for Viral Filtration Using 20 nm Filters in Biosimilar Manufacturing

Department	Biosimilars
SOP No.	SOP/BS/174/2025
Supersedes	SOP/BS/174/2022
Page No.	Page 1 of 10
Issue Date	04/05/2025
Effective Date	06/05/2025
Review Date	04/05/2026

1. Purpose

To define a validated GMP procedure for performing viral filtration using 20 nm filters during downstream purification of biosimilar drug substances to ensure effective removal of potential viral contaminants.

2. Scope

This SOP applies to all biosimilar batches undergoing viral clearance processing in the final purification stage, prior to bulk drug substance pooling and formulation.

3. Responsibilities

• Production: Execute filtration steps and monitor process parameters including pressure and flow.
• QA: Review pre-use integrity test, filtration batch record, and post-use filter integrity verification.
• Engineering: Maintain integrity testing units and verify filter compatibility with product and cleaning agents.

4. Accountability

The Downstream Manufacturing Head is accountable for successful execution and documentation of the viral filtration process in accordance with GMP and regulatory expectations.

5. Procedure

5.1 Filter Selection and Preparation

1. Use validated 20 nm-rated virus removal filters (e.g., Millipore Viresolve®, Sartorius Virosart®).
2. Verify filter part number, lot number, expiry, and Certificate of Quality (CoQ).
3. Assemble the filter into the single-use or stainless steel TFF skid system.
4. Pre-flush with 1–2 L of WFI or formulation buffer to remove preservatives.

5.2 Filter Integrity Testing (Pre-use)

1. Perform bubble point or diffusion test using integrity tester.
2. Record pass/fail status in Annexure-1.
3. Filters must pass integrity test prior to use.

5.3 Filtration Execution

1. Transfer the clarified protein bulk into feed tank under aseptic conditions.
2. Maintain inlet pressure <30 psi and flow rate per filter validation protocol (e.g., 10–20 L/hr/m²).
3. Monitor for pressure rise (filter fouling); stop if differential pressure exceeds 1.5 bar.
4. Collect filtrate directly into pre-labeled sterile holding container.

5.4 Filter Integrity Testing (Post-use)

1. Immediately after use, perform post-use integrity test on the same filter.
2. If post-use integrity fails, discard product and initiate deviation (Annexure-2).

5.5 Sample Collection

1. Collect pre- and post-filtration samples for:
   • Bioburden
   • Endotoxin
   • Protein concentration
2. Send for analysis and record results in Annexure-3.

6. Abbreviations

• nm: Nanometer
• GMP: Good Manufacturing Practice
• CoQ: Certificate of Quality
• TFF: Tangential Flow Filtration
• WFI: Water for Injection

7. Documents

1. Filter Integrity Test Report – Annexure-1
2. Filtration Deviation Log – Annexure-2
3. Sample Test Results Record – Annexure-3

8. References

• ICH Q5A – Viral Safety Evaluation of Biotechnology Products
• USP <1225> – Validation of Compendial Procedures
• WHO TRS 978 – Guidelines on Viral Safety

9. SOP Version

Version: 2.0

10. Approval Section

	Prepared By	Checked By	Approved By
Signature
Date
Name
Designation
Department

11. Annexures

Annexure-1: Filter Integrity Test Report

Filter ID	Lot No.	Test Type	Result	Performed By	Date
VF-2025-001	F5V2102	Bubble Point	Pass	Ajay Verma	04/05/2025

Annexure-2: Filtration Deviation Log

Date	Issue	Corrective Action	Responsible Person	QA Review
04/05/2025	Post-use integrity failed	Batch rejected, CAPA initiated	Sunita Reddy	QA Head

Annexure-3: Sample Test Results Record

Sample ID	Test	Result	Limit	Analyst
VF-BS-01	Endotoxin	0.05 EU/mL	<0.25 EU/mL	Sunita Reddy
VF-BS-02	Bioburden	None Detected	Absent	Sunita Reddy

Revision History:

Revision Date	Revision No.	Details	Reason	Approved By
04/05/2025	2.0	Added pre- and post-use integrity testing and pressure monitoring	Process optimization