Continuous Manufacturing is a type of production system in which materials being processed are continuosly in motion. Continuous manufacturing, like mass production, is a flow production method.
During continuous processing, distinct parts flow from one machine to the next to make a finished product. There are no interruptions between the stages of production. It’s a very organized system involving advanced machinery and producing high volumes.
Advantages of Continuous Manufacturing (CM)
• Integrated processing with fewer steps – No manual handling, increased safety
– Shorter processing times
– Increased efficiency
• Smaller equipment and facilities
– More flexible operation
– Reduced inventory
– Lower capital costs, less work-in-progress materials – Smaller ecological footprint
• On-line monitoring and control for increased product quality assurance in real-time
– Amenable to Real Time Release Testing approaches – Consistent quality
Potential for reduced cost.
Regulations & Continuous Manufacturing
• No specific regulations or guidance for continuous manufacturing, other than the definition of “lot”
• Nothing inregulations or guidance prohibiting continuous manufacturing
• Continuous manufacturing consistent with FDA’s Quality by Design (QbD) efforts
– More modern manufacturing approach
– Potential to improve assurance of quality and
consistency of drugs
– Enables quality to be directly built into process design.
Regulatory Definition of “Batch”
21 CFR 210.3.
Batch - a specific quantity of a drug or other material that is intended to have uniform character and quality, within specified limits, and is produced according to a single manufacturing order during the same cycle of manufacture
Batch refers to the quantity of material and does not specify the mode of manufacture.
Regulatory Definition of “Lot”
21 CFR 210.3.
Lot - a batch, or a specific identified portion of a batch, having uniform character and quality within specified limits; or, in the case of a drug product produced by continuous process, it is a specific identified amount produced in a unit of time or quantity in a manner that assures its having uniform character and quality within specified limits.
Definitions for both “batch” and “lot” are applicable to continuous processes.
Defining a Batch/Lot
Why does it matter under cGMP?
• Laboratory determination of final specifications for release.
– 21 CFR 211.165(a): For each batch of drug product, there shall be appropriate laboratory determination of satisfactory conformance to final specifications for the drug product..... prior to release.
• Documentation of Manufacturing
– 21 CFR 211.188 Batch product and control records shall be prepared for each batch of drug product produced and shall include complete information relating to the production and control of each batch
• Extended investigations of unexplained discrepancies
– 21 CFR 211.192: The investigation shall extend to other batches... that
may have been associated with the specific failure of discrepancy.
• Recall situation
21CFR211.150(b):Distribution procedures shall include...asystem by which the distribution of each lot of drug product can be readily
determined to facilitate its recall if necessary.
Considerations for Defining a Batch/Lot
• Ways to define a batch/lot at the product collection step?
– Production time period
– Production variation (e.g., different lots of
feedstock)
– Dependent on equipment cycling capability
– Other definition.
Steady-State in Continuous Manufacturing
• Steady state is when material properties in the system remains constant with time
– Not the same as equilibrium!
– Time to reach steady state depends upon flow properties
• When is product acceptable or not acceptable to collect? – During process start-up and shut-down
– After a disturbance (e.g., spike in feed rate)
– Handling of rejects?
• When do all component concentrations and physical properties reach steady state?
– May necessitate measurements other than concentration of active component(s).
Considerations for Control Strategy for Continuous Manufacturing (CM)
Methods to assure that product has “uniform character and quality within specified limits”?
– Characterization of in-coming materials
– In-process measurements
• Selection of sampling frequency
• In-process parameters and material attributes • Setting of appropriate acceptance criteria
– Dependent on cycling capacity of equipment – Consider interactions amongst unit operations.
Specific Sampling Considerations for Continuous Processing
• Dependent on system dynamics
– Sample frequency capable of detecting process upsets – Residence Time distributions
– Start-up frequency vs. steady state
– Measurement device and controller delays
– “Blind” times (e.g., refilling hoppers)
• Blenduniformitychallengingtomeasure
– Stratification
– Interference due to flow
– Time of acquisition of single spectra vs. flow rate – Number of probes and their distribution.
System Integration
For continuous manufacturing, increased need to :
• Understand interaction between unit operations – Ensure stable operation
– Helps support feedback/feed forward controls
– Impact of residence time distributions
– Impact of recycle loops
• Characterize propagation of changes and disturbances through system
– Understand interface between different lots of raw material – Be able to isolate bad material from disturbances
• Have an integrated data acquisition system over all unit operations
– Manage data from all on-line/in-line measurement systems
ONDQA/FDA Sponsored Research on Microreactors
• Joint research with CPAC (Center for Process Analytical Chemistry), University of Washington, Seattle and Corning
– Funded by the FDA
– Initiated in November, 2008
– Also utilize CPAC’s New Sampling/Sensor Initiative (NESSI)
• Goal of this project is to enhance our understanding of continuous manufacturing and microreactors:
– Developing a drug substance synthesis using microreactors following the QbD paradigm
– Effective implementation of sampling and online analytics
– Leveraging data from analytical tools to design an integrated control strategy
Current Challenges
• Need for integration of analytical tools to the control system to support implementation of feed-back or feed-forward control
– Sophisticated data management tools
• Defining representative sampling to consistently assure product quality over time
• Location of sampling probes
• Sample size and sampling frequency
• Need for enhanced process understanding
– Availability of mechanistic models for all processing steps
– Implementation of multivariate analysis for determination of product quality.
Concluding Thoughts
• The science exists to enable continuous manufacturing of pharmaceuticals
– Specific scientific considerations related to sampling frequency for continuous manufacturing
• There are no regulatory hurdles for implementing continuous manufacturing
– However, there is a lack of experience
• FDA supports the implementation of continuous
manufacturing using a science and risk-based approach.
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