Standard Operating Procedure for Cell Retention System Use (ATF, TFF) in Biosimilar Manufacturing

Department	Biosimilars
SOP No.	SOP/BS/144/2025
Supersedes	SOP/BS/144/2022
Page No.	Page 1 of 11
Issue Date	04/05/2025
Effective Date	06/05/2025
Review Date	04/05/2026

1. Purpose

To establish a standard procedure for the installation, operation, monitoring, and cleaning of cell retention systems such as Alternating Tangential Flow (ATF) and Tangential Flow Filtration (TFF) units used in high-density perfusion-based biosimilar production.

2. Scope

This SOP applies to upstream operations in biosimilar manufacturing where continuous culture and high cell density are maintained using ATF or TFF modules integrated with bioreactor systems.

3. Responsibilities

• Upstream Production: Setup, monitor, and operate cell retention system during batch/perfusion process.
• Engineering: Maintain and calibrate ATF/TFF hardware and monitor pressure integrity.
• QA: Approve protocols and deviations related to the retention system.

4. Accountability

The Upstream Process Head is accountable for ensuring proper operation, maintenance, and documentation of cell retention systems in accordance with validated protocols and GMP guidelines.

5. Procedure

5.1 Equipment Preparation

1. Verify system model and specifications from approved list in Annexure-1: ATF/TFF System Tracker.
2. Check availability of:
   • Single-use hollow fiber or membrane module
   • Tubing sets and clamps
   • Sterile filtration units (0.2 µm)
3. Connect system to designated bioreactor port with flow direction matching diagram.

5.2 Pre-Use Integrity and Flushing

1. Flush the loop with WFI to remove preservative.
2. Perform pressure hold test:
   • Maintain 0.8 bar for 5 mins with ≤10% pressure drop.
3. Record results in Annexure-2: Retention System Integrity Log.

5.3 Operation During Culture

1. Initiate perfusion by activating ATF/TFF circulation at defined start cell density (e.g., 20 x 10⁶ cells/mL).
2. Set recirculation rate and transmembrane pressure (TMP):
   • ATF: 0.3–0.5 bar TMP
   • TFF: 10–20 L/m²/hr flux rate
3. Monitor:
   • Cell viability and retention rate
   • Fouling indicators (pressure rise)
   • Filtrate turbidity
4. Log parameters every 4 hours in Annexure-3.

5.4 End-of-Batch Handling

1. Stop feed and disconnect cell retention loop under aseptic conditions.
2. Flush loop with WFI and decontaminate with NaOH or peracetic acid as per membrane compatibility.
3. Dispose of single-use components in biohazard containers.

5.5 Deviation Management

1. Record:
   • Flow interruption
   • Pressure anomalies
   • Unexpected filtrate appearance
2. Notify QA and file deviation report (Annexure-4).

6. Abbreviations

• ATF: Alternating Tangential Flow
• TFF: Tangential Flow Filtration
• TMP: Transmembrane Pressure
• QA: Quality Assurance
• WFI: Water for Injection

7. Documents

1. ATF/TFF System Tracker – Annexure-1
2. Retention System Integrity Log – Annexure-2
3. Perfusion Run Monitoring Log – Annexure-3
4. Deviation Report – Annexure-4

8. References

• WHO TRS 1025 – Guidelines on Continuous Manufacturing
• USP <1051> – Bioreactor Systems
• EU GMP Annex 15 – Qualification and Validation

9. SOP Version

Version: 2.0

10. Approval Section

	Prepared By	Checked By	Approved By
Signature
Date
Name
Designation
Department

11. Annexures

Annexure-1: ATF/TFF System Tracker

System ID	Type	Module Serial No.	Installation Date	Status
CR-ATF-102	ATF	HF-5087A	01/05/2025	Active

Annexure-2: Retention System Integrity Log

Date	System ID	Pressure Hold (bar)	Drop %	Status	Checked By
02/05/2025	CR-ATF-102	0.8	5%	Pass	Ajay Verma

Annexure-3: Perfusion Run Monitoring Log

Time	VCD	Viability	TMP (bar)	Flow Rate (L/hr)	Remarks
10:00	26.4	95%	0.42	1.2	Normal

Annexure-4: Deviation Report

Date	Description	Action Taken	Reported By	QA Status
04/05/2025	Spike in TMP	Membrane flushed with WFI	Sunita Reddy	Open

Revision History:

Revision Date	Revision No.	Revision Details	Reason for Revision	Approved By
04/05/2025	2.0	Included deviation management and TMP monitoring	Regulatory compliance update