Preclinical and clinical trials are important steps in the process of developing gene therapies, as they protect the safety of the patients. These trials provide a structured, stepwise approach for evaluating safety, efficacy, and risks over the long term for a new gene therapy before approval for general use in humans.
Preclinical Trials
Before any gene therapy reaches human testing, it undergoes preclinical trials, which involve lab-based tests on cell cultures (in vitro) and animal models (in vivo). These early studies aim to predict how the therapy might behave in humans, and to identify major risks that could affect patient safety.
One key focus of preclinical trials is toxicity testing. Researchers use animal models like mice or rats to observe how different doses of the therapy impact cells, tissues, and organs. This provides details of the safe dose range and early signs of toxicity, which plays an essential role in setting the dosing guidelines during clinical trials.
Another critical aspect of preclinical testing is biodistribution, as gene therapies must target specific tissues or organs while avoiding off-target effects. These studies track where the gene therapy vector travels and accumulates in the body, ensuring it reaches the intended site—like the liver or brain—while avoiding non-targeted tissues that could lead to harmful side effects.
By understanding the therapy’s distribution and persistence, researchers can refine its safety profile and reduce the risk of toxicity before advancing to human trials.
Preclinical studies also assess genotoxicity and tumorigenesis to evaluate the risk of the gene therapy causing harmful genetic changes. Researchers investigate whether the therapy could accidentally integrate into the host’s genome in a way that might activate cancer-causing genes or disrupt tumor-suppressing genes, both of which could lead to cancer. These tests help minimize the risk of tumor formation, ensuring the gene therapy is as safe as possible before moving to clinical trials.
Preclinical trials also evaluate immunogenicity, which refers to the potential of the gene therapy to trigger an immune response. This is important because an overactive immune reaction can lead to serious side effects, such as cytokine storms or immune-mediated tissue damage. By identifying these risks early, researchers can adjust the therapy to reduce its immunogenicity and help prevent severe immune reactions during human testing.
Clinical Trials
Once preclinical studies confirm that the gene therapy appears safe, it goes on to clinical trials in humans. Clinical trials are conducted under strict ethical standards and regulations aimed at protecting participants. These would include checks by Institutional Review Boards, informed consent processes, and ongoing monitoring for safety during the time of the trial.
Clinical trials are divided into phases, each with an important role to play in ensuring patient safety.
Phase 0 trials are optional trials in which a very low dose of the therapy is given to a small number of subjects in order to learn more about how the body processes the therapy (known as pharmacokinetics).
Phase I trials, sometimes referred to as "first-in-human studies", are more often the first stage of testing in human subjects. These test the safety of the therapy and define safe doses for further testing.
If Phase I results are promising, the therapy progresses to Phase II trials, which confirm its safety in a larger population and provide data on the potential benefits of the therapy. This phase will help identify other risks that may not have appeared in Phase I.
In Phase III, the therapy is tested on an even larger and more diverse group of patients. The large sample size detects adverse events that are rare and may not have been visible in earlier phases. At this point, the therapy may be approved for use in the general population.
However, the process doesn’t end with approval. Phase IV trials, also known as post-approval monitoring, continue to track the therapy’s long-term effects in the general population. Ongoing monitoring for safety is particularly vital in gene therapies, as this might have very long-term or even permanent effects on the body.
The data gathered from both preclinical and clinical trials play an important role in protecting patients. These trials help minimize risks by identifying potential hazards early in development, ensuring only the safest therapies move forward. They also provide the scientific evidence required for regulatory approval by agencies like the FDA or EMA, which demand proof of safety and efficacy before allowing a therapy to reach the market.
(This answer was provided by Maryam Taghdiri, a GETRADI Fellow based at Freiburg University Medical Center)
In order to develop a gene or cell therapy for a condition, scientists must first understand the genetic and/or cellular cause of the condition. Understanding these causes, and the extent of their effects on the body, can be a lengthy process. This process can become longer when a condition is rare, and there is limited opportunity to study it.
Gene therapy is not always an appropriate way of treating a condition.
Cell therapy relies on a thorough understanding of how the cells being used will behave when they are transplanted into the body, and how that part of the body will respond to transplanted cells.
DIfferent conditions require different means of delivering a therapy. For example, blood cancers can be treated with an infusion of a therapeutic agent, while solid tumours require a more targeted approach. This means that there are different technological and safety challenges when it comes to administering treatments.
Finally, there are logistical considerations.
You can find more detail in our Factsheet on this topic.
There are several reaons why you might not be able to receive a therapy or treatment which has been approved for use. These include:
You can read about these reasons in more detail in our Factsheet on this topic.
Genreally speaking, a medicine can only be placed on the market when its quality, safety and efficacy has been assessed by the Regulatory Authority (EMA for EU and MHRA for UK), met the standards for its intended use, and granted a Marketing Authorisation (MA). Here we compile reliable sources, databases and registries for these approved medicines in EU and UK:
For medicines approved in EU countries:
For medicines approved in UK:
Medicines development, often used interchangeably with drug development, refers to the scientific and regulatory processes involved in bringing a new medicine to the market. Medicine development is costly and time-consuming. It takes an average of 10-15 years and more than US$2 billion before it can reach the pharmacy shelf.
It starts from the pre-discovery phase during which researchers try to understand the mechanisms underlying diseases and propose possible biological targets for treating them. In the discovery phase, scientists look for potential small molecules or biologics, the “leads”, that will modulate this target and possess a therapeutic effect. Scientists then chemically modify the lead to further improve the lead's properties and therapeutic effects.
The resulting lead, now an optimised drug candidate, then moves to pre-clinical testing for studying how effective (the efficacy) and safe it is using different testing approaches. These testing approaches include in vitro testing (in a controlled environment outside a living organism like a petri dish) and in vivo testing (in a living organism) before it can be tested on humans. The results from pre-clinical studies provide information for a safe and efficacious product dosage to be used in clinical trials.
The drug candidate is next tested in clinical trials in humans if its clinical trial application is approved by regulatory authorities based on pre-clinical data, and the clinical research protocol. Clinical trials are an important part of medicine development, with the purpose to evaluate the active ingredient by finding the appropriate dosage range and identifying the side effects. Clinical trials are generally carried out in three phases, phase I, II and III. In an ideal scenario, the active ingredient would first be tested in phase 1 trials for general safety on a small group of healthy volunteers, followed by phase II trials on a larger group including patients, further followed by phase III trials for confirmatory studies on a large group of subjects.
Upon completion of the phase III trial, the sponsor submits a marketing authorisation application file to the regulatory authority (EMA for Europe) to demonstrate drug safety and efficacy. For a medicine to be authorised, the sponsor needs to show that it is effective, safe, and good quality. This requires preparing and submitting a marketing authorisation dossier that contains information drawn from pre-clinical/clinical studies and the manufacturing process description, prepared in accordance with regulatory, scientific, and procedural guidelines. After EMA’s scientific evaluation, EMA will provide a recommendation to the European Commission, which decides on granting the marketing authorisation. If granted, this results in one Marketing Authorisation that is valid in the entire EU/EEA, this means an approval for a medicine to be marketed for commercial use in the entire EU/EEA. In EU, another possible route for medicines’ approval is through a national route in which the medicine is assessed and approved by one Member State only.
After the medicine is authorised, it may be used in patients. During clinical trials, the safety and efficacy of a medicine has only been evaluated on a carefully selected small group of patients in controlled conditions for a limited amount of time. After authorisation, however, the medicine may be used in a larger number of patients and for a longer period of time. Through monitoring these activities, some previously unidentified adverse effects may be observed. To ensure patient safety, EMA and the EU Member States will constantly monitor the medicine’s safety and take according actions if new information indicates that the medicine is no longer as safe and effective as previously thought.