This PAT Guidance replaces the former Draft Guidance of August 2003. In comparison with the draft, the final version has almost the same structure. The only exception is that more stress has been put on the chapter on "Process Understanding", which represents the main concern of PAT. Before, it had just been a subtopic of "Principles and Tools". Here and there, the text of the new guideline has been shortened a bit. Some sections have been interchanged.

As far as we can see, no significant changes have been made in comparison with the draft version! If you would like to see the differences, you have to have a very close look at the documents.

One of the differences is that the guidance is now also applicable to specified biologic products that fall within the area of responsibility of CDER.

The four 'PAT Tools' listed in the guidance are now described a bit more concise as:

• Multivariate tools for design, data acquisition and analysis
• Process analysers
• Process control tools
• Continuous improvement and knowledge management tools

Their description has remained nearly unchanged. The striking thing is that the concrete methods mentioned in the draft, like NIR spectroscopy or acoustics, have been left out. This might have been done in order to underline the generality of the statements. Surprisingly enough, also the reference to the GAMP Guideline (GAMP Guide for Validation of Automated Systems) has been omitted both from the text and from the literature section. Instead, the ASTM Technical Committee E55 has been included.

As the main source of information on the topic 'PAT', the guideline now indicates the link to FDA's PAT web page.