CCIT Q&A with Andreas Hohenleutner, PhD.

Our recent white paper on FDA Complete Response Letters (CRLs) and Container Closure Integrity Testing (CCIT) has sparked strong interest across the industry. CRLs are formal notifications issued by the U.S. Food and Drug Administration (FDA) outlining why a drug application cannot be approved in its current form. As such, they provide a rare window into where sponsors most often stumble—and an opportunity to identify recurring challenges and share strategies that help developers avoid the same costly pitfalls.

The paper analyzes CCIT-related observations from recent FDA CRLs to identify recurring pitfalls and clarify the regulatory expectations behind them.

Drawing directly from FDA language and relevant guidance documents, it highlights where submissions most often fall short and translates regulatory feedback into clear, actionable lessons for drug developers.

To provide a concise overview of the key takeaways, we sat down with Andreas Hohenleutner, PhD, Senior Director, Operations Drug Product CMC & Characterization at Solvias, to discuss what FDA feedback is really telling developers — and how to build a more defensible CCIT strategy.

Download the full white paper for comprehensive insights and detailed regulatory analysis.

1) What is Container Closure Integrity (CCIT)?

Container closure integrity is the ability of a vial, syringe, ampoule, cartridge, or other container system to keep the product in and contaminants out over the full lifecycle. For sterile products, integrity is non-negotiable.

2) What are the two main categories of CCIT methods?

CCIT methods fall into two broad categories:

• Probabilistic methods
• Deterministic methods

Probabilistic methods rely on visual or observational outcomes and can be operator-dependent (e.g., dye ingress, bubble emission, microbial ingress).

Deterministic methods measure a quantifiable physical parameter (e.g., vacuum decay, pressure decay, helium leak detection, high-voltage leak detection), making results more reproducible and easier to validate statistically.

Probabilistic methods can still be viable. However, regulators expect sponsors to control subjectivity and demonstrate reproducibility. That typically requires clearly defined acceptance criteria, strong precision data, and, where possible, instrument-assisted readouts.

3) What’s a common CCIT failure seen in FDA Complete Response Letters (CRLs)?

One recurring issue in CRLs is the use of a method that cannot detect leaks at a sensitivity relevant to microbial ingress risk. FDA feedback often challenges defect size detectability and low positive-control detection rates.

It is important to understand that most systems are not “absolutely leak-free.” The objective is not zero leakage, but rather demonstrating that leakage remains below a scientifically justified threshold — and that the chosen method can reliably detect defects at or below that threshold.

A key concept here is the Maximum Allowable Leakage Limit (MALL) — the greatest leakage rate (or equivalent defect size) that can be tolerated without compromising product quality or safety.

MALL is not a fixed regulatory number. It depends on the product, container–closure system, and microbial ingress risk. Your CCIT method should be validated to detect leaks relevant to your MALL.

Another frequent shortcoming is insufficient worst-case validation. This means failing to challenge the container–closure system under conditions most likely to expose leaks. Testing only under ideal laboratory conditions may mask integrity risks that appear later in the product lifecycle.

4) What does FDA typically expect to see for CCIT in stability protocols?

The CRLs emphasize the importance of demonstrating integrity across the full shelf life — not just at a single time point.

This typically means incorporating CCIT at defined stability intervals (for example, 12-month intervals throughout shelf life) to generate a longitudinal dataset capable of identifying late-emerging integrity issues.

Closure integrity can degrade over time due to physical, chemical, or environmental stress. A one-time test is rarely sufficient to demonstrate sustained package performance.

5) How do I select a CCIT method that stands up to FDA scrutiny?

Start with a structured risk assessment of the product–package system and define the Maximum Allowable Leakage Limit (MALL).

Then select a method capable of reliably detecting leaks relevant to microbial ingress risk.

Deterministic methods are generally preferred due to their objectivity and reproducibility. However, regardless of the method selected, it must be validated thoroughly and demonstrated to be fit-for-purpose within the specific product context.