https://www.fda.gov/media/193349/download
With the FDA’s briefing documents now public ahead of the July Pharmacy Compounding Advisory Committee meeting, we finally have a detailed explanation of why FDA staff recommended againstadding TB-500 to the 503A Bulks List.
The briefing document identifies several significant weaknesses in the nomination. Some relate to the evidence submitted, while others concern the quality and consistency of the nomination itself.
1. No human clinical evidence for TB-500
The FDA states that the nominator cited three published references in support of the nomination.
However, none of those studies involved TB-500 being administered to humans.
The FDA therefore concluded that the nomination did not provide clinical evidence supporting the use of TB-500 for wound healing.
The agency also discusses the published literature on Thymosin Beta-4 (TB4) elsewhere in the review but did not consider that sufficient to establish the safety or effectiveness of TB-500, which is the substance that had been nominated.
2. Insufficient evidence of effectiveness
Beyond the lack of human studies, the FDA concluded that the available evidence was insufficient to demonstrate that TB-500 is effective for wound healing.
The agency reviewed the published literature and determined that the nomination did not provide adequate evidence to support the proposed clinical use.
3. Significant gaps in the safety data
The FDA found that the nomination lacked an adequate safety package.
Among the concerns were:
No human safety studies.
No adequate nonclinical toxicology studies.
Limited pharmacokinetic information.
Insufficient data to properly assess the risks associated with injectable TB-500.
The FDA also highlighted concerns regarding immunogenicity, noting that peptide aggregation and impurities could increase the risk of immune responses.
4. Inadequate chemical characterisation
The briefing document concludes that TB-500 was not sufficiently characterised.
The FDA identified several issues, including:
Inconsistent naming of the substance.
Limited analytical characterisation.
Insufficient impurity information.
Lack of validated analytical methods.
Limited information regarding aggregates.
Inadequate information on endotoxins and microbiological quality.
Without this information, the FDA said it could not adequately assess the quality of the active pharmaceutical ingredient.
5. Inconsistencies within the nomination
The FDA also identified inconsistencies within the submission itself.
For example:
The nomination was submitted for TB-500 free base.
The supporting Certificate of Analysis was for TB-500 acetate.
The FDA also noted discrepancies involving molecular information and chemical identifiers contained within the nomination package.
These inconsistencies weakened the overall submission.
6. Little evidence of historical pharmacy compounding
One factor considered by the FDA is whether there is evidence that the substance has historically been compounded by licensed pharmacies.
Despite TB-500 being well known within the research peptide community, the FDA found very little evidence of historical pharmacy compounding.
7. No compelling clinical need
The FDA also considered whether there was sufficient justification for allowing compounded TB-500 when approved therapies for wound management are already available.
According to the briefing document, the nomination did not establish a compelling clinical need.
The FDA’s conclusion
After reviewing the nomination, FDA staff concluded that the evidence weighed against adding TB-500 to the 503A Bulks List.
The recommendation was based on multiple factors, including:
No human clinical evidence for TB-500.
Insufficient evidence of effectiveness.
Significant gaps in the safety data.
Poor chemical characterisation.
Inconsistencies within the nomination.
Limited evidence of historical pharmacy compounding.
Failure to establish a compelling clinical need.
It’s important to remember that this is an FDA staff briefing document, not the agency’s final decision. The Pharmacy Compounding Advisory Committee will review the evidence, hear public comments, and make recommendations before the FDA reaches its final determination.
The FDA believed the nomination itself was not robust enough to support inclusion on the 503A Bulks List.
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