FDA Warning Letter Highlights Deficiencies in SST and HPLC Practices

In a recent Warning Letter dated 9 October 2025 and published on 11 November 2025, FDA cites extensive CGMP violations at a drug manufacturer based in China, with several critical findings directly linked to chromatographic practices and system suitability testing (SST). At the centre of the agency’s concerns were deficiencies in HPLC-based assay determination and the lack of robust SST controls.

Following an inspection conducted in March 2025, the investigators reported that the firm’s approved HPLC test method did not include an appropriate system suitability check as outlined in USP <621>. Instead of demonstrating instrument performance prior to sample analysis, analysts were instructed to construct a standard curve only at long intervals. This approach effectively masked system drift and compromised the accuracy of assay results.

In addition, the agency identified fundamental weaknesses in data acquisition and calculation processes:

• Excel spreadsheets used for chromatographic calculations were not validated, not version-controlled and not included in the laboratory’s data governance system.
• Several files that were used to perform suitability and assay calculations had been deleted, and no audit trail existed to reconstruct the original calculations.
• Access rights were shared across user groups/job titles, making results non-attributable and violating basic ALCOA principles.

These issues represent significant data integrity risks and impair the laboratory’s ability to ensure accurate, reliable assay outcomes. FDA requested a comprehensive investigation into the extent of data inaccuracies, a thorough risk assessment for affected products, and a global CAPA strategy addressing analytical controls, SST and data governance.

Beyond the analytical and data-integrity topics, the Warning Letter also addresses additional deficiencies, including inadequate sterility controls and inconsistent product specifications.

FDA notes that the company has initiated a recall of all affected products within expiry that were already in distribution to the U.S. market, following discussions with the agency.

The complete Warning Letter to Taizhou Kangping Medical Science and Technology Co., Ltd. is available on the FDA's website.