Many of the items debated at the 50th meeting of the WHO Expert Committee on Biological Standardization (ECBS)¹ reflect the increasing complexity of biomedicines. It seems possible that within the next few years the number of new biological medicines may supersede that of new chemical entities coming onto the market. The challenge now facing manufacturers and national regulatory authorities is how to continue to assure the quality and safety of new and existing biologicals. Biological standardization is set to play a key role in this respect.

¹ The WHO Expert Committee on Biological Standardization (ECBS) held its 50th meeting in October 1999. The ECBS is responsible for setting global standards for biological substances used in medicine, including vaccines, blood products, biological therapeutics and diagnostic procedures. Members were from Belgium, Canada, China, the Netherlands, the Russian Federation, the United Kingdom and the United States of America. Temporary Advisers were invited from Austria, Belgium, Canada, Finland, Germany, the Netherlands, Japan, South Africa, Switzerland, the United Kingdom and the United States of America. Representatives were present from the Council of Europe, European Association of the Plasma Products Industry, International Association for Biologicals, International Federation of Clinical Chemistry, International Federation of Pharmaceutical Manufacturers Associations, and the International Society of Thrombosis and Haemostasis.

Recommendations for oral poliovirus vaccine

Revised recommendations (formerly requirements) for production and control of oral poliovirus vaccine (OPV) were agreed by the ECBS. New quality control procedures have now been introduced with the potential to increase the stringency of control. This is an important consideration given the considerable success of the polio eradication initiative and enhanced risk/benefit considerations of OPV use. The new quality control procedures will also decrease vaccine testing time. This will speed up OPV availability and respond to increased demands for supplies of vaccine to complete the eradication programme.

For the first time, a test for molecular consistency of production for a live virus vaccine is now available. Mutant analysis by polymerase chain reaction (PCR) and restriction enzyme cleavage — MAPREC — quantifies reversion of a key base, 472C, that correlates in type 3 poliovirus vaccine with results of the WHO neurovirulence test (1). WHO-supported studies of the method have shown it to be a robust and reliable procedure. Results showed that MAPREC provided a very valuable additional test for consistency of production and the method was endorsed as the in vitro test of preference for control of poliovirus type 3. Excellent progress with MAPREC assays for poliovirus types 1 and 2 was also reported and the possibility of introducing MAPREC for these serotypes will be considered as soon as possible.

The discovery of the gene for the cellular receptor for poliovirus led to development of the TgPVR21 transgenic mouse susceptible to poliovirus infection (2, 3). A neurovirulence test for poliovirus vaccine has now been developed in the TgPVR21 transgenic mouse line and was shown in WHO-sponsored studies to be a suitable alternative to the test in monkeys for poliovirus type 3. It was therefore introduced in the new recommendations. Excellent progress with TgPVR21 neurovirulence tests for poliovirus types 1 and 2 was reported and the possibility of introducing a neurovirulence test in TgPVR21 mice for these serotypes will be considered as soon as possible.

The entire cycle from basic scientific research, through method development to standardization and application as control tests of MAPREC and the transgenic mouse model were all paradigms for regulatory research. This work clearly illustrated the need for long-term commitment of resources if significant advances in control and standardization of biologicals are to be made.

Reference reagents and panels for diagnostic procedures for TSEs

A WHO Consultation on International Reference Materials for Diagnosis and Study of Transmissible Spongiform Encephalopathies (TSEs) held in May 1999 identified the need for international harmonization and the establishment of reference reagents and panels to compare diagnostic procedures.

Reference brain-derived materials and human and animal lymphoid tissue were considered necessary to compare assay systems. A working group established by WHO to develop appropriate standards was taking steps to obtain these materials. However, preparation of these reference materials will require dedicated facilities to comply with strict levels of laboratory containment. Candidate reference materials will be characterized in bioassays and immunoassays.

International standards

The ECBS established 28 new or replacement International Standards and Reference Reagents covering a wide range of products (Table 1, page 234). Additionally, several International Standards, Reference Materials and Requirements that are no longer needed were discontinued following a public consultative process (Table 2, page 235) (5). The Committee also proposed to discontinue the first International Reference Preparation for protamine (salmon) at its next meeting, subject to public comment to this notice (Table 3, page 235).

Discontinuation of requirements

As recommended by the 49th meeting of the ECBS, the intention to discontinue the WHO Requirements for Cholera Vaccine and Smallpox Vaccine was circulated for public comment. As a consequence, it was decided that the WHO Requirements for Cholera Vaccine should be discontinued in order to ensure correct testing of the new oral inactivated vaccines. However, in the case of smallpox virus, laboratory stocks had not been destroyed as expected and the Requirements for Smallpox Vaccine were retained.

Database and electronic publication

Following a recommendation of the ECBS, the catalogue of WHO International Biological Standards and Reference Materials has been fully updated and made available on the Internet. The entire list of WHO biological standards and reference reagents is now available on the WHO home page at the following address:

http://www.who.int/technology/biological.html

A number of future developments concerning the new database include proposed linkages to the custodian laboratory holding the standards and to the corresponding WHO documents and publications and reports in the scientific literature.

Other activities

The ECBS endorsed several other new projects including new or replacement reference materials for pertussis toxin and quality control of nucleic acid amplification tests (parvovirus B19 DNA, hepatitis A RNA, HTLV-1 RNA and HTLV-2 RNA). The Committee was also updated on many projects that are in progress. These included evaluation of mouse protection models for acellular pertussis vaccines; harmonization of antigen content and potency measurement of diphtheria and tetanus vaccines; standardization and control of oral cholera vaccines; standardization of antibody measurement; development of guidelines on preclinical and clinical testing of vaccines; abnormal toxicity test; consideration of the use of thiomersal as a preservative in vaccines, and evaluation of safety issues associated with the use of cell substrates for vaccine production.

Ongoing activities for blood and plasma derived products include a project on quality assurance of plasma-derived medicinal products and plasma fractionation activities; quality control of virus markers (HBsAg, anti-HCV and anti-HIV) in blood screening; standardization of unfractionated heparin and development of new international reference materials for blood grouping reagents.

Progress in standardization of biological therapeutics was also reported and the Committee endorsed proposals to establish new reference materials for vascular endothelial growth factor, ciliary neuro-trophic factor, keratinocyte growth factor, neurotrophin-3 and relaxin. Given the rapidly expanding cytokines sector and limited resources available to carry out these activities, the Committee considered a policy to prioritize work in this area. A decision tree, developed during a WHO Consultation on Cytokine Standards, was modified for use in prioritizing work for all categories of biologicals.

References

1. Chumakov, K.M. et al. Correlation of the amount of virus with altered nucleotide sequence and monkey test for acceptability of oral poliovirus vaccine. Proceedings of the National Academy of Science, 88: 199-203 (1991).

2. Ren, R. Transgenic mice expressing a human poliovirus receptor: a new model for poliomyelitis. Cell, 63: 353-362(1990).

3. Koike, S. Transgenic mice susceptible to polioviruses. Proceedings of the National Academy of Science, 88: 951-955(1991).

4. WHO Drug Information, 13: 2, 86-90 (199).