Introduction
January 6th 2023, the U.S. Food and Drug Administration approved Leqembi (lecanemab-irmb) via the Accelerated Approval pathway for the treatment of Alzheimer’s disease. Leqembi is the second of a new category of medications approved for Alzheimer’s disease that target the fundamental pathophysiology of the disease. These medications represent an important advancement in the ongoing fight to effectively treat Alzheimer’s disease. The FDA granted this application Fast Track, Priority Review and Breakthrough Therapy designations. The approval of Leqembi was granted to Eisai R&D Management Co., Ltd.
Billy Dunn, M.D., director of the Office of Neuroscience in the FDA’s Center for Drug Evaluation and Research said “Alzheimer’s disease immeasurably incapacitates the lives of those who suffer from it and has devastating effects on their loved ones. This treatment option is the latest therapy to target and affect the underlying disease process of Alzheimer’s, instead of only treating the symptoms of the disease.”
What is Alzheimer’s disease: It is an irreversible, progressive brain disorder affecting more than 6.5 million Americans that slowly destroys memory and thinking skills and, eventually, the ability to carry out simple tasks. While the specific causes of Alzheimer’s are not fully known, it is characterized by changes in the brain—including amyloid beta plaques and neurofibrillary, or tau, tangles—that result in loss of neurons and their connections. These changes affect a person’s ability to remember and think.
Who is affected by Alzheimer’s disease?
Age is the best-known risk factor for Alzheimer’s disease with symptoms usually appearing after age 60. Older African American and Hispanic/Latino adults are more likely to have Alzheimer’s disease than older white adults. You may also be at higher risk of developing Alzheimer’s disease if you:
- Are a woman.
- Have ever had a moderate or severe head injury.
- Have heart disease, stroke, high blood pressure, diabetes, or obesity.
- Have an immediate family member with Alzheimer’s disease.
- Engage in few physical, mental, or social activities.
Treatment: Lecanemab-irmb is a recombinant humanized immunoglobulin gamma 1 (IgG1) monoclonal antibody directed against aggregated soluble and insoluble forms of amyloid beta, and is expressed in a Chinese hamster ovary cell line. Lecanemab-irmb has an approximate molecular weight of 150 kDa. LEQEMBI (lecanemab-irmb) injection is a preservative-free, sterile, clear to opalescent and colorless to pale yellow solution for intravenous use by infusion after dilution. LEQEMBI is supplied in single-dose vials available in concentrations of 500 mg/5 mL (100 mg/mL) or 200 mg/2 mL (100 mg/mL). Leqembi was approved using the Accelerated Approval pathway, under which the FDA may approve drugs for serious conditions where there is an unmet medical need and a drug is shown to have an effect on a surrogate endpoint that is reasonably likely to predict a clinical benefit to patients. The results of a Phase 3 randomized, controlled clinical trial to confirm the drug’s clinical benefit have recently been reported and the agency anticipates receiving the data soon.
Clinical Trials: Researchers evaluated Leqembi’s efficacy in a double-blind, placebo-controlled, parallel-group, dose-finding study of 856 patients with Alzheimer’s disease. Treatment was initiated in patients with mild cognitive impairment or mild dementia stage of disease and confirmed presence of amyloid beta pathology. Patients receiving the treatment had significant dose- and time-dependent reduction of amyloid beta plaque, with patients receiving the approved dose of lecanemab, 10 milligram/kilogram every two weeks, having a statistically significant reduction in brain amyloid plaque from baseline to Week 79 compared to the placebo arm, which had no reduction of amyloid beta plaque. These results support the accelerated approval of Leqembi, which is based on the observed reduction of amyloid beta plaque, a marker of Alzheimer’s disease. Amyloid beta plaque was quantified using positron emission tomography (PET) imaging to estimate the brain levels of amyloid beta plaque in a composite of brain regions expected to be widely affected by Alzheimer’s disease pathology compared to a brain region expected to be spared of such pathology.
Warning and precautions:
- Amyloid-related imaging abnormalities (ARIA): The prescribing information for Leqembi includes a warning for amyloid-related imaging abnormalities (ARIA), which are known to occur with antibodies of this class. ARIA usually does not have symptoms, although serious and life-threatening events rarely may occur. ARIA most commonly presents as temporary swelling in areas of the brain that usually resolves over time and may be accompanied by small spots of bleeding in or on the surface of the brain, though some people may have symptoms such as headache, confusion, dizziness, vision changes, nausea and seizure. Another warning for Leqembi is for a risk of infusion-related reactions, with symptoms such as flu-like symptoms, nausea, vomiting and changes in blood pressure. The most common side effects of Leqembi were infusion-related reactions, headache and ARIA. As specified in the prescribing information, Leqembi is indicated for the treatment of Alzheimer’s disease. The labeling states that treatment with Leqembi should be initiated in patients with mild cognitive impairment or mild dementia stage of disease, the population in which treatment was studied in clinical trials. The labeling also states that there are no safety or effectiveness data on initiating treatment at earlier or later stages of the disease than were studied.
- Infusion-Related Reactions: Infusion-related reactions were observed in 20% (32/161) of patients treated with LEQEMBI compared to 3% (8/245) of patients on placebo; and the majority (88%, 28/32) occurred with the first infusion. Infusion-related reactions were mild (56%) or moderate (44%) in severity. Infusion-related reactions resulted in discontinuations in 2% (4/161) of patients treated with LEQEMBI. Symptoms of infusion-related reactions include fever and flu-like symptoms (chills, generalized aches, feeling shaky, and joint pain), nausea, vomiting, hypotension, hypertension, and oxygen desaturation. After the first infusion, 38% of patients treated with LEQEMBI had transient decreased lymphocyte counts to less than 0.9 x109 /L compared to 2% in patients on placebo, and 22% of patients treated with LEQEMBI had transient increased neutrophil counts to greater 7.9 x109 /L compared to 1% of patients on placebo. In the event of an infusion-related reaction, the infusion rate may be reduced, or the infusion may be discontinued, and appropriate therapy initiated as clinically indicated. Prophylactic treatment with antihistamines, acetaminophen, nonsteroidal anti-inflammatory drugs, or corticosteroids prior to future infusions may be considered.
Sources:
https://www.accessdata.fda.gov/drugsatfda_docs/label/2023/761269Orig1s000lbl.pdf#page=16
https://www.fda.gov/consumers/minority-health-and-health-equity-resources/alzheimers-disease