Usage Examples
- Every CQA in the control strategy maps to a named control, not just to the release specification.
- The control strategy summary sits in 3.2.S.4.5; the detailed controls sit in 3.2.S.2.2 through 3.2.S.4.1.
- We cannot rely on drug substance testing for bioburden, so that CQA is controlled upstream in the control strategy.
What is Control Strategy?
A control strategy is the complete planned set of controls, spanning input materials, process parameters, in-process tests, and release specifications, that together assure process performance and product quality. No single specification is the control strategy.
A control strategy exists because testing the finished batch cannot prove the batch is fit for use. A release assay detects only what it is sensitive to, at the point it is run, on the sample that was drawn. ICH Q10 answers that gap by defining a control strategy as the planned set of controls, derived from current product and process understanding, that assures process performance and product quality.
A control strategy covers four groups of controls under ICH Q11: controls on material attributes, controls implicit in the design of the manufacturing process, in-process controls including tests and process parameters, and controls on the drug substance itself. A control strategy is not the specification. ICH Q11 is explicit that the drug substance specification is one part of a total control strategy, and that not all CQAs need to appear on it.
A control strategy is applied by mapping each CQA to the control that actually holds it, then filing those controls where ICH M4Q places them: 3.2.S.2.2 for process controls, 3.2.S.2.3 for control of materials, 3.2.S.2.4 for critical steps and intermediates, 3.2.S.4 for control of drug substance, 3.2.S.6 for container closure. ICH Q11 recommends summarising the whole strategy in 3.2.S.4.5, tabular or diagrammatic.
Not to be confused with
- Critical Quality Attribute (CQA)
- a CQA is a property that has to be held within a range; the control strategy is the set of controls that holds it. CQAs are the outputs being protected, the control strategy is the mechanism doing the protecting, and every CQA needs a named control.
- Critical Process Parameter (CPP)
- a CPP is one input whose variability affects a CQA, and it sits inside the in-process controls group. The control strategy is the whole architecture, spanning material attributes, process design, in-process tests, and drug substance release.
- Design space
- ICH Q8 defines design space as the multidimensional combination and interaction of input variables and process parameters demonstrated to provide assurance of quality. Design space is optional and describes where you may operate; a control strategy is mandatory and describes how you stay there.
- Process validation
- process validation is documented evidence that the process, operated within established parameters, performs reproducibly. The control strategy is the prospective plan of controls; process validation is the demonstration that running to that plan delivers product meeting its predetermined specifications.
The obligations split between the ICH quality guidelines and, in the US, the CGMP regulation.
What you must do
- 1Define a control strategy for every drug substance manufacturing process, traditional or enhanced, covering material attributes, controls implicit in the process design, in-process controls, and drug substance release testingICH Q11 §6.1
- 2Hold each CQA within its range, limit, or distribution by one of three routes: on the specification and confirmed by final drug substance testing, on the specification and confirmed by upstream controls such as Real Time Release Testing, or off the specification and ensured entirely by upstream controlsICH Q11 §6.1.2
- 3Document the methods and frequency of monitoring and control for each parameter and attribute in the strategy, including facility and equipment operating conditions and finished product specificationsICH Q10 §5
- 4Establish and follow written procedures describing the in-process controls, tests, and examinations conducted on samples of in-process material from each batch21 CFR 211.110
- 5Make in-process specifications consistent with drug product final specifications and derive them from previous acceptable process average and process variability estimates, using suitable statistical procedures where appropriate21 CFR 211.110
- 6File the individual control strategy elements in their assigned CTD sections (3.2.S.2.2, 3.2.S.2.3, 3.2.S.2.4, 3.2.S.4.1) and summarise the overall drug substance control strategy in the specification justification, 3.2.S.4.5ICH Q11 §8.4
Common mistakes
Filing a specification and calling it the control strategy
ICH Q11 §6.1.2 states the drug substance specification is one part of a total control strategy and that not all CQAs need to be on it. A submission that shows only release limits gives the reviewer no line of sight from CQA to control, and the gap comes back as CMC information requests late in the review cycle, when the answer requires data you no longer have time to generate.
Setting in-process limits from whatever batches you happen to have
21 CFR 211.110(b) requires in-process specifications to be consistent with drug product final specifications and derived from previous acceptable process average and process variability estimates, determined by suitable statistical procedures where appropriate. Limits copied from a single development lot are not derived from process variability, and there is no statistical basis to defend the release decision the first time a commercial batch drifts.
Relying on drug substance testing for CQAs testing cannot see
ICH Q11 §6.1.2 notes that for sterilised chemical entities and biotechnological or biological drug substances there is an inherent limitation in detecting low levels of bacterial or viral contamination, so testing on the drug substance is considered to provide inadequate assurance of quality. Tight release limits on an insensitive assay are not a control; those CQAs must be held by attribute and in-process controls upstream.
When This Matters
- Every CQA in the control strategy maps to a named control, not just to the release specification.
- The control strategy summary sits in 3.2.S.4.5; the detailed controls sit in 3.2.S.2.2 through 3.2.S.4.1.
- We cannot rely on drug substance testing for bioburden, so that CQA is controlled upstream in the control strategy.
Frequently Asked Questions
Four groups, per ICH Q11: controls on material attributes, controls implicit in the design of the manufacturing process, in-process controls including in-process tests and process parameters, and controls on the drug substance such as release testing. ICH Q10 adds facility and equipment operating conditions, and the methods and frequency of monitoring.
Related Use Cases
- Pharma Use Cases
Cut NDA and sNDA prep time by 60% with AI-assisted drafting and automated readiness checks
- Biotech Use Cases
Compress IND prep from 8-12 weeks to under 3 weeks with AI-assisted drafting and validation
- CMC Workflows
Track ICH quality guidelines automatically and get alerts when changes impact your products
- Quality/QA Workflows
Track GxP regulation changes and enforcement trends
