FDA Highlights Systemic Quality Failures in OOS Investigations and HPLC Controls

In January 2026, the U.S. FDA issued a Warning Letter (dated 23 December 2025) to Tower Laboratories Ltd., citing significant CGMP violations identified during a July 2025 inspection of its Michigan OTC drug manufacturing facility. The letter emphasizes deficiencies in out-of-specification (OOS) investigations and HPLC-based analytical controls.

The agency found repeated failures to conduct scientifically sound investigations into OOS assay and stability results. Stability failures were retested without identifying root causes, corrective and preventive actions (CAPAs) were inadequate, and customers were not notified of affected lots. The FDA criticized the company’s continued attribution of failures to “packaging defects” without supporting data—a recurring concern from prior inspections.

HPLC analyses were also problematic, with sample preparation procedures insufficiently validated, potentially contributing to inaccurate results. Method validation gaps were acknowledged, but historical impacts were not assessed, and interim controls were insufficient.

The FDA now requires an independent retrospective review of OOS results, full remediation of investigation and CAPA systems, enhanced quality oversight, and revalidation of analytical methods to restore compliance and regulatory confidence.

14-01-2026