Drug research is a unique multidisciplinary process leading to the development of novel therapeutic agents for diseases, which have no proper treatment or treatment at all. The search for new biopharmaceuticals is driven by a medical need and perceived likelihood of technological success. Also, the search for new biopharmaceuticals is bound to both therapeutic efficacy and safety parameters.
There are several factors that should be taken into consideration to carry out a safety testing of a new biopharmaceutical. As most of the biopharmaceutical products are proteinaceous in nature, few non-allergic adverse reactions other than those attributable to the primary pharmacological activity are anticipated. Nevertheless, both good laboratory practice (GLP) and good manufacturing practice (GMP), as established for other modes of pharmaceutical production, are essential to biopharmaceuticals.
We know that before every launch of a space shuttle, all systems are carefully checked to prevent anything from going wrong. The same thing applies to the manufacturing of vaccines. Every vaccine is unique and during each step of production these must be inspected, and adjusted if necessary, to ensure they are safe and that they retain their activity.
For a vaccine candidate to be safe it has to be pure and the process of eliminating any potentially harmful substances takes substantial time and money. For instance, let us take a type of experimental vaccine that consists of deoxyribonucleic acid (DNA). It takes just a few days to prepare the same in a research laboratory. Nevertheless, regulatory agencies like the US Food and Drug Administration (FDA) and the European Medicines Agency (EMEA) will not allow vaccine candidates that are made in a research laboratory to be tested in humans, even for early phase I clinical trials.
Much of the manufacturing costs for candidate vaccines used in human trials are due to the conditions required by a set of standards called GMP, which are required by regulatory agencies for products that are tested in humans. GMP conditions require, among other things, clean and highly purified air and water. In addition, everything a person does is double checked.
Maintaining a GMP facility costs more than $100,000 a week. It is estimated that 80 per cent of the expense to manufacture a vaccine is due to maintaining GMP conditions.
Pathogens - Restricted admission
Each kind of vaccine needs to be free of disease causing agents known as pathogens, or any other potentially harmful substances. For example, DNA vaccine candidates are produced using bacteria. The outer membrane of these bacteria can contain endotoxins (bacterial endotoxins), which are a concern because they are toxic to humans and therefore must be carefully removed from vaccine candidates. To remove these endotoxins, the DNA vaccines are filtered and then tested to detect any remaining impurities.
Some other vaccines use weakened viruses as vectors to carry genes that encode fragments of human immunodeficiency virus (HIV), or immunogens. Some kind of viral vaccine vectors are grown in the cells of chicken eggs, which are required to be free from pathogens like avian viruses or bacteria. This is important because live viruses grown in the chicken cells cannot be chemically treated to kill contaminants, as is done for inactivated influenza vaccines that are also grown in eggs, because that would render the viral vector inactive. These pathogen free eggs aren't cheap. IDT, a Germany-based vaccine manufacturer buys them at about 20 times the cost of regular eggs.
Another category includes vaccines that use adenovirus as a vector. These are typically grown in the cells derived from humans and these vaccines need to fulfil certain safety criteria before they get approved by regulatory agencies. For example, prions are infectious protein particles that cause diseases in animals, like mad cow disease and a fatal variant known as Creutzfeldt-Jakob disease in humans. Due to this, there are only a handful of cell lines available to grow adenovirus vector-based vaccines.
Standardising the process
With DNA vaccines, manufacturers identify the best bacteria for manufacturing the DNA and find the ideal time to stop bacterial growth before harvesting the DNA. Simple steps like this help to optimise the process and make a big difference in the efficiency of vaccine production.
Manufacturers also have to formulate the ideal growth conditions for vaccines made in animal cells. Some chicken embryo cells that are used to grow a viral vector called modified vaccinia ankara (MVA), for example, prefer growing while adhered to surfaces, while others grow best in liquid suspension. Growth efficiency drops as soon as HIV immunogens are introduced into the vector.
But once a vaccine is manufactured at a large scale, the price is likely to come down. Making large batches is easier for some vaccines than others, depending on how they are made. It is relatively easy for DNA vaccines that are manufactured in bacteria.
In 2005, Nobilon International, part of Akzo Nobel, a biotechnology company, obtained a European GMP approval to produce human influenza vaccines for use in clinical trials. Nobilon employs a novel vaccine production system, which uses large scale cell culture technology in 2000 litter fermentors, as opposed to the traditional method of using commercial embryonated chicken eggs.
This advanced technology is more reliable and results in pure, safe and efficacious vaccines with constant quality. Also, during the pandemic bird flu outbreak, Nobilon's cell culture production can be used immediately in contrast to the traditional production system based on chicken eggs, which needs a significant logistical coordination and could lead to eggs becoming unavailable.
Assuring quality, safety, efficacy & acceptability of plant based vaccines
Dr P. Minor, National Institute for Biological Standardisation and Control, Potters Bar, UK, focused on the adventitious agents that might be present in plants. Presently available vaccines and biologicals are derived from cells originated in humans (MRC5, WI38, etc.), monkeys (primary kidney), chickens (chick embryo fibroblast), or rodents (hybridomas, Chinese hamster ovary and primary hamster kidney).
Viruses of concern from human cells include HIV and hepatitis B and C. Practically, human viruses have not been a major issue in vaccine production because they are dealt with through verified procedures, although there is a concern about the occasional failure to adhere to GMP.
In fact, animal viruses are more dangerous, especially if they are capable of infecting humans. Even if they do not infect humans, adventitious animal viruses may adversely affect production. In the case of chicken eggs, it is not proven that avian viruses such as avian retroviruses (e.g. avian leucosis virus in yellow fever vaccines) and other agents excluded from specific pathogen free (SPF) flocks are dangerous. Also, the use of rodent cell lines is not free from risks as many serious human viral diseases are transmitted by rodents, including viruses which cause little disease in the normal host. Thus viruses in animal cells can be dangerous.
Regulatory perspectives
The World Health Organisation (WHO) guidelines on good agricultural and collection practices (GACP) for medicinal plants provide general technical guidance on obtaining medicinal plant materials of good quality for the sustainable production of herbal products classified as medicines.
WHO guidelines for clinical evaluation of vaccines are available to assist in evaluation of clinical trials as a part of the regulatory overview. The guidelines outline the data that should be obtained during the different stages of vaccine development to support a marketing approval. Additionally, that apply to all existing vaccines, several specific issues should be considered as prerequisites for initiation of clinical trials of plant-derived vaccines. First of all, consistency of production should be carefully monitored and arrogate parameters for a vaccine in question identified during the development of a vaccine. Since there is not much evidence on vaccine quality at the stage of clinical trial approval, consistency of production is an essential element in assuring vaccine quality. Secondly, characterisation of starting materials as well as intermediates and final products is of great importance. Specifically, genetic stability of a plant-derived vaccine should be demonstrated. Thirdly, justification of the use of plants instead of currently used substrates should be provided.
The problem to date is the production of a single dose delivery that is made under current GMP (cGMP) type manufacturing control. Employing food protein manufacturing techniques, the antigens could be extracted and concentrated using lose cost high throughput methods.
In early 2008, four of India's biggest vaccine manufacturers - Pasteur Institute of India, Haffkine Bio-Pharmaceutical Corporation, BCG Vaccines and Central Research Institute - have had their licenses suspended by the Government of India after failing to meet GMP requirements.
In May 2008, Merck's bulk drug substances used to manufacture many of its vaccines were found adulterated and the FDA is requesting a meeting with senior management to expedite the firm's corrective actions.
The principle of the existing GMPs for drugs/biologics should be applied in general. However, considering the unique aspects of manufacturing vaccines in transgenic plants, additional requirements and modification of the existing regulations should be implemented. GMP should apply from the beginning, i.e., plant banking system to the final product.
In sum one can say that all action proving, in accordance with the principles of GMP that any procedure, process, equipment, material, activity or system actually leads to the expected result.
(The author is with Accure Labs Pvt. Ltd, Noida)