FDA Warning Letter: Significant Violations of Aseptic Manufacturing Procedures uncovered

In March 2026, the US Food and Drug Administration (FDA) issued a Warning Letter to Simtra BioPharma Solutions. This was based on an unannounced inspection of the Simtra Deutschland GmbH (formerly Baxter Oncology GmbH) manufacturing site in Halle/Westphalia, Germany, which took place from 18 to 26 September 2025. During the inspection, the authority identified several serious violations of the requirements of Current Good Manufacturing Practice (CGMP) as set out in 21 CFR Parts 210 and 211.

According to the FDA, the methods, facilities and controls used in the manufacture, processing, packaging or storage of the medicinal products do not comply with regulatory requirements. The products manufactured are therefore considered "adulterated" within the meaning of the Federal Food, Drug, and Cosmetic Act, i.e. they have not been manufactured in accordance with GMP.

One of the main points is the controls in the aseptic manufacturing process. The FDA found that the facility did not have clearly enough defined or segregated areas to reliably prevent contamination or product mix-ups during aseptic manufacturing. Several production lines were particularly affected, including facilities with Restricted Access Barrier Systems (RABS) used to manufacture sterile medicinal products for the US market.

Further significant deficiencies concerned the cleaning and disinfection systems. According to the inspection report, a cleaning solution was fed to the cleaning points via pipes with very long so-called "dead legs". Such dead legs can lead to stagnation of liquids and thus promote the growth of microorganisms. In fact, between June 2023 and September 2025, a total of 47 microbiological detections were identified during routine testing, 14 of which exceeded the specified limits.
Internal investigations identified the design of the cleaning system’s pipework as the likely cause of the contamination. However, the FDA considered that the corrective and preventive actions (CAPA) implemented were insufficient to resolve the underlying design issues.

In addition, as part of the Environmental Monitoring programme, Gram-negative microorganisms were repeatedly detected in ISO 5 areas of the aseptic production facility. From the FDA’s perspective, this indicates fundamental weaknesses in the hygiene management system and in the control of critical production environments.

The FDA has called on the company to submit detailed measures to address the identified deficiencies in the Warning Letter. These include, in particular, improvements to the design of the systems, an effective root cause analysis of the microbiological findings, and sustainable corrective actions to ensure aseptic process control.  

This case once again highlights the high level of regulatory scrutiny that the FDA applies to aseptic manufacturing (also with unannounced inspections). In particular, the combination of technical design flaws, repeated microbiological findings and inadequate CAPA measures is frequently viewed by inspectors as an indicator of systemic weaknesses in quality management. Read the full Warning Letter to Simtra BioPharma Solutions on the FDA website.