臨床試験の4つの相（フェーズ）

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Pre-Clinical Development

Before an investigational treatment can be given to people in a clinical trial, sponsors must find out if it might be harmful. They first test the treatment in the lab on cells or animals to see if there are any risks and to prove that it might help patients. Once they have enough information, they ask government regulatory agencies and ethics committees for approval to start clinical trials in humans. [US FDA, Preclinical Research, 2018]

Clinical Development

Before new medical treatments like drugs or medical devices can be used widely, they must first be tested in clinical trials to check if they are safe and work well. The medical treatment being studied is often called an “investigational treatment” because it is not yet approved for use outside of a clinical trial. The information from these clinical trials is then reviewed by government regulatory agencies to see if the investigational treatment should be approved for use.

Most investigational treatments must pass through several stages of research before they can be approved for use. These stages are called “phases.”Each phase has a different purpose and helps answer different questions.

The 4 phases are:

• Phase 1 - Checking safety and dosage
• Phase 2 - Testing effectiveness and side effects
• Phase 3 - Confirming efficacy and comparing to standard treatments
• Phase 4 - Tracking long-term effects after approval

The process is long but important to make sure the treatment works and is safe for people with a certain condition or disease.

Phase 1 clinical trials: Is the treatment safe?

第1相試験では、通常100人以下の少数の人々を対象に、開発中の治療が安全かどうかを調べます。この段階では、よく見られる副作用を特定し、試験の次の相で使用する適切な投与量を見つけます。場合によっては、健康なボランティアに投与したり、その他の治療が存在しない、または十分でない患者さんを対象に治験薬の研究が行われます。

Phase 1 trials study how an investigational treatment behaves in the body and what side effects it might cause. They start with low doses and slowly increase them, watching for harmful side effects. The goal is to find the optimal dose and dosing method (for example, by mouth, infusion into a vein or injection) for treating the condition or disease with the fewest side effects.

Phase 1 trials may also study how the treatment is taken up, moves through, is broken down, and leaves the body. These are called Pharmacokinetic studies. Sometimes these trials check if food or other drugs affect the investigational treatment. Phase 1 trials include many tests, like checking vital signs or blood tests to make sure the treatment is safe.

All this information helps the sponsors design safe plans for the next phases of testing. The main goal of a phase 1 trial is to find safe doses to use in phase 2.

Phase 2 clinical trials: Does the treatment work?

Phase 2 clinical trials usually have more participants, up to several hundred people. この段階でも、治験薬の安全性について調べますが、同時に、特定の疾患または病状がある人々に効果があるかどうかを調べ始めます。

In these clinical trials, participants who have a specific disease or condition get the study treatment at the safe doses found in phase 1. The research team watches their health and symptoms to see how well the treatment works. For example, researchers may measure tumor size in cancer drug trials or viral load in antiviral medication trials. They also look at specific genes, proteins, or other biological signs (called biomarkers) to study the treatment's effect.

Phase 2 clinical trials give sponsors more information about how safe a treatment is and how well it works before moving to phase 3. Information from phase 2 trials also helps set the goals and research plan for phase 3 studies.

Phase 3 clinical trials: Is it better than what’s already available?

Phase 3 clinical trials collect more information about how safe an investigational treatment is and how well it works. 通常、第3相試験には多数の参加者が参加し、時には数千人に及びます。

Phase 3 trials will compare an investigational treatment with the current standard-of-care to see if it works as well or better, or has fewer side effects, than what is already available to patients. Some phase 3 trials use a placebo which looks like a treatment but does not have any active product in it. Using a placebo alone without another active treatment (such as standard of care treatment) may not be appropriate in some conditions or diseases.

Phase 3 trials can take many years. Sponsors might study the investigational treatment in different doses or combine the investigational treatment with other treatments. They often study how well it works over a longer time and with different groups of people, like younger or older people and people of different racial and ethnic groups. Participants in these trials should represent the patients who may use the treatment if it gets approved.

Phase 4 clinical trials: What else do we need to know?

承認前の試験では安全性と有効性について調べますが、この時点では、特に長期的な使用について、多くの疑問が残っています。第4相試験は、年齢、性別、人種や民族、また健康状態の異なるより多くの人々を対象に観察が行われます。この段階の試験では、規模の小さい、短期の試験では確認されなかった副作用が見つかる場合があります。また、治験薬がどのように患者さんの生活の質に影響を及ぼすかについて調べます。

Phase 4 trials might test the treatment for other medical uses, different doses, or new combinations with other treatments. Even though sponsors may want to expand how the treatment is used, safety is still the most important focus.

Summary of clinical trial phases

The 4 phases of clinical trials show the steps for testing investigational treatments thoroughly:

• Phase 1: focuses on safety, dosage and best way to give the treatment in a small number of people
• Phase 2: expands to refine methods, check safety and see how well the treatment works
• Phase 3: large-scale, often international, studies that compare the treatment to the standard-of-care. They provide strong data on risks and benefits
• Phase 4: continues to check safety and gathers real-world data on long-term effects

Each phase builds on the one before, ensuring safety while bringing potential innovative treatments from the lab to patients.

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