Issues to Consider in Human Vaccine Trials [3,24]

Human. Pharmacological evaluation studies including mechanism of action in animals will be used as a basis for recommending further clinical trials.

Selection of experimental animals

The selection of the most appropriate animal species for testing is a major issue in pre-clinical studies. A suitable species is one in which the test material has a pharmacological effect due to the expression of a receptor or antigenic determinant. A number of different techniques can be used to determine the appropriate species, such as functional or immunochemical tests.

Animal species for testing monoclonal antibodies are those that express the desired antigenic determinant and provide information on cross-reactivity in animal tissues similar to human tissues. An animal species that does not express the antigenic determinant may still be suitable for toxicity assessment if cross-reactivity in unspecified tissues with the corresponding human fraction is demonstrated.

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Safety studies are usually performed in two animal species. However, in some cases, for example when only one species is relevant or when the biological properties of the biological product are well understood, testing in one species may be sufficient. On the other hand, two species may be needed to determine toxicity in short-term studies, but only one species may be used to determine toxicity in long-term studies.

Toxicological studies in inappropriate species can lead to misleading results and are therefore not recommended. In the absence of appropriate species, compatible transgenic animals with similar human receptors or homologous proteins may be used to perform studies. When it is not possible to use compatible transgenic animal models or homologous proteins, some toxicological properties can be assessed by repeated dosing over 14 days. In recent years, there has been much progress in developing studies in animal models similar to humans.

These models can help researchers gain insight not only into pharmacology, pharmacokinetics, and dosing, but can also aid in determining the safety of investigational products.

Select dose and route of administration

The route and frequency of administration should be as similar as possible to those expected in the clinical trial. The pharmacokinetics and bioavailability of the product in the species being tested and the safe dosage for human use should be considered. In these cases, the extent to which animal exposures correlate with clinical exposures should be determined, taking into account the effects of mass, concentration, formulation, and route of administration. However, the route of administration in animals may differ from the clinical route if the route of administration is necessitated by limited bioavailability, limitations due to the route of administration, or size/physiology of the animal species being tested. Dose levels vary based on information about the dose-response relationship. In some cases, the product being tested has little or no toxicity, and no maximum dose can be determined. In these cases, a scientifically based assessment of the underlying factors should be used to select the dose.

Immunogenicity

Many biotechnologically derived pharmaceuticals for human use elicit immune responses in animals. Therefore, it is necessary to measure the antibodies produced by the body after administration of the investigational product in order to interpret the results of the study. The characteristics of the antibodies, such as the antibody titer in the number of responding animals, whether the antibodies are neutralizing or not, should also be specified. In addition, the effects of antibody production on pharmacokinetic parameters, prevalence, severity, adverse effects, etc. should also be considered when interpreting the data. In most cases, the immune response of animals to biological products is very different from that of humans. If the data interpretation

Failure to consider this issue will result in a failure to appreciate the significance of the immune response process. Antibody production in animals cannot predict the ability to form antibodies in humans because humans can produce humoral antibodies against human-like proteins and these antibodies persist for a long time in the body. The appearance of a strong hypersensitivity response to recombinant proteins is very rare in humans. Therefore, positive research results with protein-based drugs in guinea pigs are often not predictive of reactions in humans and are of little value when applied to humans.

Thus, based on the above information, pharmaceutical companies will decide whether the new drug meets scientific requirements to continue research and development.

1.5.2. Phase I

Phase 1 is the first phase of testing a new active ingredient or new formulation of a drug in humans. Typically, this phase is conducted on a small group of healthy volunteers, about 20-50 people. The purpose of a phase 1 study is to establish a preliminary assessment of the safety, pharmacokinetics and pharmacodynamics of the active ingredient in human subjects. This phase is usually conducted in an inpatient setting so that patients can be continuously monitored by medical staff. The subjects are usually monitored until the drug's half-life has passed. Phase I often includes dose-tracing to determine the most appropriate dose for humans. Although phase I is usually conducted on healthy people, some cases are still conducted on patients with terminal illnesses and no treatment options. These exceptions often apply to patients with cancer or HIV. There are several different types of phase I trials.

1.5.3. Phase II

Once safety has been established in phase I, phase II is conducted in larger groups, but still with a limited number of patients, approximately 20-300. The purpose of phase 2 studies is to evaluate the therapeutic activity and safety of the active ingredient in patients, and to determine the appropriate dose and dosing regimen to provide optimal therapy for clinical trials. Phase II is sometimes divided into two phases, IIA and IIB.

- Phase IIA is designed to evaluate the dose required.

- Phase IIB to evaluate the efficacy of pharmaceutical/biological products.

1.5.4. Phase III

Phase III is a multicenter, randomized, controlled trial that is conducted on a larger number of patients, from 300 to 3,000 or more, depending on the disease and the product under investigation. The purpose of phase III research is to determine the stability of the formulation, the short-term and long-term safety/efficacy of the active ingredient, and evaluate the overall therapeutic value. To study frequently occurring adverse reactions and to detect special characteristics of the product under investigation. Clinical trial conditions in this phase are conducted close to those of normal use [3,19].

Although not required in all cases, it is common for a new drug or pharmaceutical product to be successfully tested at least twice to demonstrate its efficacy and safety and then approved by regulatory agencies such as the US Food and Drug Administration (FDA), the Australian Therapeutic Goods Administration (TGA) and the European Medicines Agency (European Community). Once a drug has successfully passed phase III testing, the test results will be compiled into a report that comprehensively describes the methodology, results on animals and humans, the formulation, and the process.

manufacturing and shelf life. This document will become the official document provided to other countries for review and approval for domestic use. Most drugs that have undergone phase III trials can be marketed according to FDA standards. However, when serious adverse events are reported after the drug/pharmaceutical has been marketed, the drug/pharmaceutical may be withdrawn from the market.

1.5.5. Phase IV

Phase IV clinical trials are conducted after a drug has been approved for marketing. These trials are conducted on the basis of the characteristics of the approved product, usually in the form of post-marketing surveillance or evaluation of therapeutic value or evaluation of treatment strategies. These trials also aim to monitor safety after the drug is marketed. Safety monitoring is designed to detect rare adverse effects or those that occur with long-term use in a larger population. The methods used in this phase may be different, but the same scientific and ethical standards are used for pre-marketing trials.

1.6. Issues to note in human vaccine trials [3,24]

The phases of vaccine testing generally follow the phases of clinical trials for a new drug or pharmaceutical product. For a vaccine to be approved for use on the market, it must also undergo animal and human testing phases (Figure 1.6). Phase I and II are intended to evaluate safety and immunogenicity in a small group of subjects. If the vaccine has been shown to be safe and immunogenic in Phase I and Phase II, it will be tested in Phase III to demonstrate efficacy. Phase III must be designed with clear hypotheses and conducted on

The community will use this vaccine in the future. After being licensed, phase IV is conducted to monitor the vaccine's protective ability. The protective ability of the vaccine can be assessed by assessing the immune response to the vaccine in the community after the vaccine is introduced into the immunization schedule. However, a more accurate way is to directly evaluate and compare the subjects who receive the vaccine with the subjects who do not receive the vaccine to answer the question of whether the vaccine is actually effective and safe when used in the community. The design used for this phase is usually a descriptive study, which can be a cohort or a case-control study.

However, when conducting the actual testing stages, there are also

Some issues to consider.

Purpose

 Is there an immune response?

 Has protection against VR/VK infection

 Is it safe?

 Does it meet MD?

 What is the most appropriate dose?

 Is it safe?

 MD response level?

 Effective

stable?

 Is it safe?

 Are vaccines safe in the community?

Pre-Contract Stage I Stage II Stage III Stage IV

Object

Animal

30-50 people

200-300 people

300-3000 people

Community

Figure 1.6. Summary of vaccine testing phases

1.6.1. Research outline

For a successful vaccine trial, the development of a quality and scientific protocol is a decisive factor. Phase I protocols may not need to be as detailed as those for phases II, III, and IV, but they must clearly define the required elements of the protocol. According to the provisions of the Code of Federal Regulations - USA, the protocol must include the following elements: (1) details of the objectives and purposes of the study; (2) the names and addresses of the researchers, the research facilities, and the Ethics Committees that will participate in the review of the study; (3) the number of subjects participating in the study and the inclusion and exclusion criteria; (4) the study design and characteristics of the control group; (6) a description of how the outcomes will be evaluated; (7) a description of the methods of monitoring the study subjects and methods of minimizing adverse effects on the subjects. In addition, the protocol also includes the content of the overview and the need for the study, information about the disease under study such as clinical characteristics, epidemiology, known information about protective immunity as well as an assessment of the need for the study and the risks to the participants. The protocol also needs to clearly describe the type of study such as whether it is controlled or not, single-blind or double-blind, randomization method, sample size, and how the results will be analyzed.

In research designs involving children, more careful consideration is needed. The first issue to consider is the age at which the vaccine is given. This depends entirely on the age at which the vaccine is given. For most pathogens, it is ideal to give a protective vaccine as young as possible. However, in the early stages of life, children inherit immunity from their mothers and can inactivate some live virus vaccines such as measles vaccine. Therefore, measles vaccine cannot be given in the first months. On the other hand, early life is a time when children receive many vaccines, so it is necessary to consider testing new vaccines at the same time as existing vaccines. Typically, phase I trials involve children receiving vaccines.

It is recommended that the other vaccines be administered within 2 weeks of each other to reduce confounding factors in safety or immune responses to concomitant vaccines. It is economically and practically preferable that the new vaccine be scheduled to coincide with routine vaccinations to reduce costs and time. Therefore, safety and efficacy assessments with the effects of concomitant vaccines will be evaluated in phase II, with consideration given to the number of doses per child. Designing a study protocol in children requires careful consideration to minimize inconvenience to the study subjects while still ensuring the necessary data are collected.

Another issue of concern is for vaccines using recombinant DNA technology or containing recombinant DNA because although molecular DNA technology is very precise, some people believe that recombinant DNA will be a threat to the natural environment. Therefore, vaccines using this technology in the outline should explain the consequences for the environment after using this vaccine for humans, the ability of the strains in the vaccine to survive in different environmental conditions such as water, soil, food, especially with comparisons with wild strains.

Many vaccines currently use live bacterial or viral strains that can be released into the environment through the respiratory tract (such as Rubella vaccine) or through feces (such as Cholera vaccine or Polio vaccine) and are capable of transmitting from person to person. Transmission of oral polio vaccine virus has been a concern since the first use of the vaccine because this vaccine creates community immunity. In addition, transmission of vaccine virus or recombinant viruses can in some cases cause disease due to vaccine virus. Therefore, the protocols for phases I and II must focus on describing measures to measure the ability of live vaccines to transmit from person to person.

1.6.2. Selection of volunteers to participate in the study

The research phases need to recruit healthy people, especially phase I, to avoid confounding factors that affect the assessment of vaccine safety. In order to be able to select the right subjects for the vaccine.

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