Global consensus meeting: potency testing of new TB vaccines, considerations of generic issues
2-3 October 2012, Geneva, Switzerland
This was the third consensus workshop tackling rate-limiting steps in TB vaccine development organized by the same three co-sponsors (WHO, Aeras and TBVI). While the two previous meeting addressed the criteria to bring TB vaccines (“Geneva Consensus I”) and live vaccines in particular (“Geneva Consensus II) into clinical trials, this meeting tackled the question of potency assays of new TB vaccine for QC purposes.
The range of new TB vaccines that are currently under development covers virtually every vaccine type including whole live micro-organisms, viral vectored, antigens extracted or secreted from the micro-organisms or produced by genetic engineering or chemical synthesis. Vaccines may contain an adjuvant.
Testing for characterization or for QC purposes in general and potency-related testing in particular will have to be appropriate for the type of vaccine under consideration. As expected, currently available potency-related tests for TB vaccines in development vary considerably depending upon the vaccine strategy/ technology being employed.
The meeting sought to address the following key questions:
- If no agreed or proven correlates are available for potency testing, would the use of animals for potency testing be useful, ethical and meaningful?
- Would antibody responses against selected epitopes of the antigen (e.g. in mice) be adequate for QC of new sub-unit vaccines in the light of the absence of potency correlates?
- Would thorough physico-chemical characterization, alone or possibly combined with one or more of the above described scenarios, be adequate for QC of new sub-unit vaccines in the light of the absence of correlates of protection?
- What regulatory testing regimen would be the minimum likely requirement?
The expected outcomes of the meeting were:
- Consensus on the above questions, to be published in the peer-review press, and
- Initiation (“kick-off”) of a discussion that is ultimately intended to lead to formal WHO guidance via the ECBS mechanism.