Standard Operating Procedure for Concentration Adjustment Post-UF in Biosimilar Manufacturing

Department	Biosimilars
SOP No.	SOP/BS/181/2025
Supersedes	SOP/BS/181/2022
Page No.	Page 1 of 9
Issue Date	04/05/2025
Effective Date	06/05/2025
Review Date	04/05/2026

1. Purpose

To define a standardized procedure for adjusting the protein concentration of biosimilar bulk drug substances after ultrafiltration (UF) to meet final specification prior to bulk storage or formulation.

2. Scope

This SOP applies to biosimilar batches requiring reconcentration or dilution following UF or diafiltration steps to achieve target concentration ranges specified in the batch manufacturing record (BMR).

3. Responsibilities

• Production: Perform dilution or reconcentration as per BMR and record processing details.
• QC: Analyze in-process samples for protein content (e.g., UV 280, Bradford, BCA).
• QA: Verify concentration adjustment log, review compliance with batch instructions.

4. Accountability

The Downstream Process Head is accountable for ensuring accurate concentration adjustment and documentation prior to batch disposition.

5. Procedure

5.1 Determination of Target Concentration

1. Refer to the product-specific BMR to identify target protein concentration (e.g., 40–60 mg/mL).
2. Review QC in-process result from post-UF sample to determine actual protein level.

5.2 Concentration Below Target

1. If the post-UF concentration is below the acceptable range:
   • Reconnect the UF system and continue filtration.
   • Sample periodically and re-test until target is reached.
2. Record volumes processed, flow rate, and membrane TMP in Annexure-1.

5.3 Concentration Above Target

1. If the product is over-concentrated:
   • Add pre-filtered formulation buffer gradually under controlled agitation.
   • Mix for at least 15 minutes with slow speed stirrer.
   • Take homogenized sample and analyze protein concentration.
2. Repeat stepwise dilution until final concentration is within limits.

5.4 Final Mixing and Homogeneity

1. Ensure complete mixing of final bulk solution by recirculation or gentle agitation for 30 minutes.
2. Confirm uniformity by sampling from top, middle, and bottom locations and test for protein content.

5.5 Documentation

1. Record batch number, adjustment method, volumes added/removed, and test results in Annexure-2.
2. QA to review and sign off before release for next step.

6. Abbreviations

• UF: Ultrafiltration
• BMR: Batch Manufacturing Record
• QC: Quality Control
• TMP: Transmembrane Pressure

7. Documents

1. UF Volume Adjustment Log – Annexure-1
2. Final Concentration Adjustment Record – Annexure-2

8. References

• ICH Q8 – Pharmaceutical Development
• WHO TRS 1004 – GMP Guidelines for Biotherapeutics
• FDA Guidance – Bulk Drug Substance Handling and Controls

9. SOP Version

Version: 2.0

10. Approval Section

	Prepared By	Checked By	Approved By
Signature
Date
Name
Designation
Department

11. Annexures

Annexure-1: UF Volume Adjustment Log

Time	Volume (L)	TMP (bar)	Protein Conc. (mg/mL)	Remarks
09:00	6.0	1.1	38.2	Under target
11:00	5.2	1.2	42.5	Achieved

Annexure-2: Final Concentration Adjustment Record

Batch ID	Initial Conc. (mg/mL)	Method	Final Conc. (mg/mL)	QC Analyst	Date
BS-PF-029	63.4	Dilution	59.8	Sunita Reddy	04/05/2025

Revision History:

Revision Date	Revision No.	Details	Reason	Approved By
04/05/2025	2.0	Clarified dilution steps and added homogeneity verification	Process robustness improvement