Tim Sandle published a recent blog post concerning a (FDA) Warning Letter related to an inadequate validation of a rapid microbiological method by Sage Products Inc. Tim's post reviews the warning letter findings and poses a number of follow up questions.
My opinions are as follows. Tim's original blog post is reproduced after my opinion. Tim's blog on this topic may be viewed by clicking here.
The FDA warning letter may be viewed by clicking here.
MY OPINION
This was an unfortunate event that should, in no way, dissuade firms from implementing rapid methods. To support my opinion, I need to provide clarity around the warning letter points, which are presented below in quotation marks.
“Your firm failed to establish and document the accuracy, sensitivity, specificity, and reproducibility of its test methods. Specifically, you use the [redacted] method to screen for microbiological contamination in drugs produced entirely at your facility and those manufactured under contract. This [redacted] screening method [redacted] for microbiological examination of your liquid drug products is not adequate for its intended use. You attempted to validate your [redacted] microbial detection method, but were not able to demonstrate that it could reliably and repeatedly determine whether objectionable microorganisms were present in your drugs.”
This tells me two things. First the rapid method was not adequately validated to demonstrate equivalency to the compendial method, which is a requirement in USP and the other compendia.
“After receiving three consumer complaints for discoloration of this product, you initiated testing of your retains using both the modified U.S. Pharmacopeia (USP) microbiological limits method and the [redacted] method. Both analyses found microbial contamination. Notably, the USP modified method [redacted] found an exceedingly high microbial count of over 57,000 CFU/ml, and also identified Burkholderia cepacia, an objectionable microorganism, in this product lot.”
“Had your firm been utilizing a screening method capable of consistently detecting B. cepacia, these products may not have been released in the first instance.”
Obviously! It appears the “validated” rapid method did not detect the presence of microorganisms in the original sample (which is why it was apparently released) and as such, there was no positive response to illicit confirmatory testing of an objectionable, such as B. cepacia.
“FDA informed you that your [redacted] method [redacted] has not been adequately validated for detecting the presence of microorganisms, including the presence of B. cepacia. In a subsequent meeting on November 30, 2016, FDA advised you to use a verified compendial method for all bulk drug solutions and finished product microbiological testing until you could further assess the suitability of the [redacted] method.”
This statement could mean a number of things. An alternative method, including a rapid method, must be equivalent to the compendial method. For nonsterile drugs, which I assume is the case with this warning letter, you must demonstrate the finished product is within aa appropriate quantitative specification (the reason why we perform USP 61) and does not contain any objectionable or specified microorganisms (which is why we perform USP 62 and additional tests for organisms that may not be specifically covered in the compendia). Some of the reasons why the rapid method could not detect microorganisms, including B. cepacia, could be fond in the next FDA statement.
“It specifies a [redacted] dilution factor. USP <62> requires a 1:10 dilution factor. Your dilution factor is [redacted] times greater than the USP method and provides insufficient detectability to rule out the presence of objectionable microorganisms and unacceptable total counts.”
Well, this is an issue regardless of whether the method used was USP 62 or an alternative method. Diluting out the test sample more than what is prescribed in the compendia may dilute out organisms that could be present. This was a mistake that should have been avoided.
Furthermore the rapid method it not account for the enrichment step called for in USP <62>. Also “it does not include the scraping step during sample preparation, which your submitted laboratory data indicates is required to validate organism recovery.”
Again, the same sample preparation steps must be performed in an alternative method, unless you can show a different procedure gives equivalent results to the compendial or original sampling and sample preparation strategy.
There was also a comment about the use of stressed organism as part of method validation (a controversial point within pharmaceutical microbiology): “it lacks evidence that small numbers of various microorganisms, including those that are injured and stressed, can be reliably recovered. Specifically, sample effect (defined by your firm as the inhibitory effect of a sample on the growth of various microorganisms) data for B. cepacia was collected using a fresh-grown culture, not a stressed organism.”
This was an interesting finding. The use of stressed organisms fueling the validation of rapid methods has been suggesting in PDA Technical Report #33 (TR33) and up until recently, the prior version of Ph. Eur. 5.1.6. Obviously, the FDA continues to require the use of stressed organisms when validating an alternative or rapid microbiological method because organisms normal found in finished product, especially if the product is preserved, will be stressed to some extent.
The final charge was that the method validation did not “establish potential sample interference factors (e.g., enhancing or quenching) for each product formulation.”
This tells me the firm did not perform method suitability on the product to eliminate the potential for false positives and false negatives. This is a current requirement in the USP, Ph. Eur. and TR33 and if Sage did not perform these tests during their rapid method validation studies, this is a significant issue.
There was also concern that the replacement method, unlike the USP method, did “not provide for potential speciation of the detected microbial contamination in the [redacted] initial screening test.”
Some rapid methods are based on the growth of microorganisms and may provide CFUs for subsequent analysis, including confirmation of an objectionable organisms and/or microbial identification. However, other rapid methods may not be based on growth and as such, follow up analysis of positive results may not be possible unless a separate sample was tested specifically for this purpose. Because eh exact rapid method under dispute is not disclosed in the warning letter, it is not possible to conclude the capabilities of the alternative method at this time.
Tim Sandle poses the following questions in his original post on this subject, based on the Sage warning letter. I will answer each in turn:
Q. Does the validation of methods require the use “stressed” organisms?
A. Depending on the application, the use of stressed organisms should be considered. Firms do not have to test dozens of stressed organisms but should select relevant strains and use a stressing condition that is defendable. Novartis published a number of papers on stressing organisms when they validated a rapid sterility test (see the reference page at rapidmicromethods.com for downloads or links to the papers). IN any case, firms should discuss their validation plans with the relevant regulatory authority to understand if the use of stressed organisms is expected.
Q. Does validation always need to be against each product formulation (not just the strongest concentration of the most inhibitory ingredient)?
A. If method suitability testing takes into consideration the greatest (and least) challenge to the alternative method, then you may be able to justify bracketing formulations to support these studies. But this will depend on the actual formulations intended for testing. Again, discuss your strategy with the regulators up front.
Q. How are representative samples built into the validation process?
A. Samples should be selected for validation studies identical to what will be tested routinely (by the rapid method). Consideration for sample preparation, dilutions, etc. should also be noted and as required by the compendia or regulatory expectations.
Q. Does a list of objectionable organisms need to be prepared ahead of the method validation? Or is this just a B cepacia issue?
A. Firms should understand what organisms should be detected by the method, based on a product’s intended use and patient population. This should be done regardless of whether an alternative method will be validated or if the standard compendial method is utilized.
TIM'S ORIGINAL POST
In July 2017 Sage Products Inc. received a warning letter from the U.S. Food and Drug Administration (FDA). Within the warning letter was a concern about the implementation of rapid microbiological method, where the method had been used to replace a compendial method.
In the warning letter, the FDA state “Your firm failed to establish and document the accuracy, sensitivity, specificity, and reproducibility of its test methods.” This relates to the use of a rapid method.
Specifically: “You use the (b)(4) method to screen for microbiological contamination in drugs produced entirely at your facility and those manufactured under contract. This (b)(4) screening method (b)(4) for microbiological examination of your liquid drug products is not adequate for its intended use. You attempted to validate your (b)(4) microbial detection method, but were not able to demonstrate that it could reliably and repeatedly determine whether objectionable microorganisms were present in your drugs.”
The FDA are concerned about the comparative findings from the USP method and the replacement rapid method: “After receiving three consumer complaints for discoloration of this product, you initiated testing of your retains using both the modified U.S. Pharmacopeia (USP) microbiological limits method and the (b)(4) method. Both analyses found microbial contamination. Notably, the USP modified method (b)(4) found an exceedingly high microbial count of over 57,000 CFU/ml, and also identified Burkholderia cepacia, an objectionable microorganism, in this product lot.”
It seems that the firm elected to run with the results from the alternative method, despite the USP method finding an objectionable microorganism. This led the FDA to state: “Had your firm been utilizing a screening method capable of consistently detecting B. cepacia, these products may not have been released in the first instance.” Part of the reason was “because [the company] failed to include B. cepacia on the list of objectionable organisms.”
The use of the alternative method had also gone against FDA advice: “FDA informed you that your (b)(4) method (b)(4) has not been adequately validated for detecting the presence of microorganisms, including the presence of B. cepacia. In a subsequent meeting on November 30, 2016, FDA advised you to use a verified compendial method for all bulk drug solutions and finished product microbiological testing until you could further assess the suitability of the (b)(4) method.”
The concerns the FDA had with the rapid method were:
“It specifies a (b)(4) dilution factor. USP <62> requires a 1:10 dilution factor. Your dilution factor is (b)(4) times greater than the USP method and provides insufficient detectability to rule out the presence of objectionable microorganisms and unacceptable total counts.”
Furthermore the rapid method it not account for the enrichment step called for in USP <62>. Also “it does not include the scraping step during sample preparation, which your submitted laboratory data indicates is required to validate organism recovery.”
There was also a comment about the use of stressed organism as part of method validation (a controversial point within pharmaceutical microbiology): “it lacks evidence that small numbers of various microorganisms, including those that are injured and stressed, can be reliably recovered. Specifically, sample effect (defined by your firm as the inhibitory effect of a sample on the growth of various microorganisms) data for B. cepacia was collected using a fresh-grown culture, not a stressed organism.”
The final charge was that the method validation did not “establish potential sample interference factors (e.g., enhancing or quenching) for each product formulation.”
There was also criticism about the sampling and sample plan used to ensure the tested sample was representative of the lot. There was also concern that the replacement method, unlike the USP method, did “not provide for potential speciation of the detected microbial contamination in the (b)(4) initial screening test.”
The implications from the FDA letter, as well as signaling a pertinent lesson when implementing a rapid method that needs to be equivalence to or better than the rapid method, are:
- Does the validation of methods require the use “stressed” organisms?
- Does validation always need to be against each product formulation (not just the strongest concentration of the most inhibitory ingredient)?
- How are representative samples built into the validation process?
- Does a list of objectionable organisms need to be prepared ahead of the method validation? Or is this just a B cepacia issue?
If you have views on this, please add a comment.
Thanks to Nigel Halls for the heads-up about this warning letter and its considerable implications.