Carefully Assess Effectiveness, Challenges Prior to Practical Use

Approval for a new drug for the treatment of Alzheimer’s disease, which accounts for 70% of dementia cases, has been applied for in Japan. It is vital to carefully assess how well the drug can meet the expectations of people who are eagerly awaiting it.

The U.S. Food and Drug Administration has granted accelerated approval for lecanemab, a new drug jointly developed by pharmaceutical giant Eisai Co. and Biogen Inc. of the United States. The makers have already begun selling the drug in the United States and are aiming for its approval in Japan by the end of this year.

Dementia causes memory loss and other symptoms that make it difficult for people to perform their daily activities. An estimated 55 million people worldwide suffer from dementia, but there is no fundamental cure for the disease.

All the drugs currently approved in Japan merely provide supportive measures that temporarily relieve symptoms.

Lecanemab is a drug that targets the cause of the disease. A clinical trial in which the drug was administered to patients in the early stages of the disease for 18 months reportedly showed a 7½-month delay in the decline of cognitive functions. This could be said to be unprecedented progress.

Alzheimer’s disease occurs when cerebral nerves are damaged, causing brain atrophy. There is a theory that the disease is caused by an abnormal accumulation of a certain protein in the brain, so removing this protein can possibly inhibit the progression of the disease.

Lecanemab is a drug that works to remove this protein. In 2021, another drug with the same function was given accelerated approval in the United States, but it has not been widely used due to insufficient data showing its effectiveness, and its approval in Japan has been shelved.

The development of drugs for dementia has encountered difficulties. Therefore, the expectations for a new drug are immeasurable. Nevertheless, it remains important to thoroughly screen the drug first and steadily specify the conditions for approval.

Even if the drug is approved, there are many challenges before it can become widely used. A special assessment is necessary to determine whether the patient is likely to benefit from the drug, but a limited number of facilities and staff are available to perform the test. If the drug is to be put to practical use, a medical system must be established to make it easier for patients to receive treatment.

The impact on medical finances cannot be overlooked. More than 1 million people in Japan are said to be suffering from early-stage Alzheimer’s disease. The treatment is estimated to cost millions of yen per person annually in Japan. It is necessary to consider whether the effectiveness of the treatment will be worth the cost, such as if it reduces the burden of care on family members.

Lecanemab is not a drug that prevents or restores the decline in cognitive functions, and it cannot be used for patients whose symptoms have already progressed. Caution must also be paid to the risk of side effects, such as brain hemorrhage. The effectiveness and safety of the drug when administered over a long period of time are not known.

To prevent patients and their family members from misjudging the actual effects and risks due to excessive expectations, frontline doctors should strive to provide clear and easy-to-understand explanations.

(From The Yomiuri Shimbun, Jan. 30, 2023)