A healthy volunteer is a person voluntarily participating in a clinical trial without the target disease and without health characteristics that would significantly distort the planned investigation or justify an unacceptable risk. Healthy volunteers are primarily included in early Phase I trials and in bioequivalence studies. Since participation regularly provides no direct therapeutic benefit for them, scientific necessity and particularly careful risk minimization are central.
Role in Phase I and bioequivalence studies
For suitable active substances, healthy volunteers allow a comparatively controlled investigation of safety, tolerability, pharmacokinetics, and optionally pharmacodynamics. This can facilitate the characterization of concentration-time profiles, food effects, or dose proportionality, because disease, concomitant therapy, and disease-related variability are not in the foreground. However, a first-in-human administration is not an automatic indication for the participation of healthy individuals. Selection depends on the mechanism of action, non-clinical findings, expected risks, and the medical question.
In bioequivalence studies, healthy adults are often included to compare the exposure of a test and reference formulation under standardized conditions. Suitability is to be verified based on predefined inclusion and exclusion criteria. Screening, medical history, examination, laboratory values, and, if applicable, further tests should identify risks and ensure a population suitable for the research question. The designation “healthy” is therefore not an absolute status, but a protocol-related suitability assessment.
Ethics, informed consent and compensation
Without self-benefit from participation, the relationship between foreseeable risk and expected knowledge must be justified particularly carefully. Regulation (EU) No 536/2014 requires that the rights, safety, dignity, and well-being of subjects are protected and that risks and burdens are justified against the expected benefit and the relevance of the study. Understandable, voluntary, and documented informed consent is a prerequisite. Participation must not be influenced by undue pressure or misleading promises.
Compensation can take into account time spent, burdens, and study-related expenses. However, it must not inappropriately influence free decision-making. The protocol, patient information, and investigator site must transparently define what payments or reimbursements are planned and how insurance coverage and the treatment of study-related harm are organized. Ethical evaluation is not based on the compensation amount alone, but on the entire protection concept, informed consent, and the appropriateness of the risk.
Distinction from the patient as a study participant
A patient as a study participant has the target disease or a clinical picture relevant to the trial. In therapeutic trials, there may be a prospect of individual benefit for them, even if this is not guaranteed. For healthy volunteers, this prospect is regularly absent. This changes the ethical consideration, but not the requirements for informed consent, scientific quality, safety monitoring, and voluntary consent. “Healthy volunteer” and “patient” therefore designate different study populations, not different standards of protection.
Certain substance classes or risks argue against testing in healthy individuals. For medicinal products against advanced cancers, clinical development according to ICH S9 is aimed at patients with cancer; if significant or inadequately predictable toxicity is expected, a patient population is usually more appropriate. The population must also be chosen critically in the case of cytotoxic mechanisms of action, potential genotoxicity, or a benefit that can only be meaningfully assessed in sick individuals. The protocol justifies this decision based on available data.
Relevance for clinical trials
Working with healthy volunteers requires closely coordinated operational planning. Recruitment must not compromise voluntariness; screening and inclusion must be documented consistently. During the study, dosing, sampling, adverse events, laboratory values, and discharge criteria must be monitored promptly. In early studies, particularly clear escalation rules, emergency preparedness, and independent medical evaluation of safety data are important. Inspections and audits look at data as well as the traceability of the consent and protection process.
Full-service CROs such as Mediconomics support the planning of suitable inclusion and exclusion criteria, the study protocol, and the documents for the ethics committee and authorities. Further services are the selection and management of qualified Phase I investigator sites, monitoring, data management, medical safety processes, organization of volunteer logistics, and medical writing for clinical study reports.
Frequently Asked Questions (FAQ)
Does a healthy volunteer receive an investigational medicinal product without any benefit?
A direct therapeutic benefit is regularly not expected. Participation can be ethically justifiable if risks and burdens are minimized and justified, consent is voluntary, and the study answers a relevant scientific question.
Is the participation of healthy volunteers restricted to Phase I?
No. It is also possible in bioequivalence, food effect, or other pharmacokinetic studies. Decisive are the suitability of the population for the research question and an acceptable risk, not the phase designation alone.
Why do healthy volunteers not participate in many oncology trials?
For many antineoplastic agents, an expected risk is not offset by a direct benefit for healthy individuals. Testing in patients can also be scientifically necessary if tumor biology or expected toxicity is essential for the assessment.
Regulatory references
- Regulation (EU) No 536/2014 on clinical trials on medicinal products for human use – regulates protection, informed consent, and risk assessment for subjects.
- EMA, Guideline on strategies to identify and mitigate risks for first-in-human and early clinical trials – describes the risk-based planning of early clinical trials.
- ICH M3(R2), Nonclinical Safety Studies for the Conduct of Human Clinical Trials and Marketing Authorization for Pharmaceuticals – categorizes non-clinical data to support human exposure.
- ICH S9, Nonclinical Evaluation for Anticancer Pharmaceuticals – concerns the development of medicinal products for patients with advanced cancers.