Reviewed by the Help Dementia Editorial Team — our editors review every article for accuracy against guidance from the National Institute on Aging, the Alzheimer’s Association, and peer-reviewed sources.
Yes, new drugs can treat Alzheimer’s disease before amyloid plaques fully build up in the brain—marking a fundamental shift in how we approach this disease. The FDA has already approved two anti-amyloid drugs designed to slow cognitive decline in early stages: lecanemab (Leqembi), which gained full approval in July 2023, and donanemab (Kisunla), approved in July 2024. These medications target amyloid beta in early symptomatic stages, and clinical evidence shows measurable benefits.
For example, in the Clarity AD trial involving 1,795 patients with early-stage Alzheimer’s, lecanemab reduced cognitive decline by 27% over 18 months, slowing the rate of decline compared to untreated disease progression. Beyond these approved treatments, researchers are investigating even earlier intervention—in people who show brain amyloid accumulation but have no memory loss or cognitive symptoms yet. The AHEAD 3-45 study, an NIH-funded trial, is testing whether lecanemab can prevent cognitive decline in cognitively unimpaired adults with elevated amyloid levels, potentially stopping disease before symptoms ever appear. Meanwhile, experimental approaches using nanobody therapeutics and drugs like NU-9 are targeting soluble amyloid oligomers—the toxic form that accumulates before plaques develop—suggesting that the next generation of treatments may work even earlier in the disease process.
Table of Contents
- What Makes Early Intervention Different From Past Alzheimer’s Treatments?
- How These Drugs Work—And Why Timing Matters
- Clinical Evidence—What the Trials Actually Show
- Cost, Access, and the Affordability Challenge
- Side Effects and the Need for Close Monitoring
- The Experimental Pipeline—Targeting Amyloid Before Plaques Form
- The Future of Alzheimer’s Prevention—When Will We Treat Before Symptoms?
- Conclusion
How Drugs Target Build Up of Plaques Differently Now
For decades, Alzheimer’s treatments focused on managing symptoms like memory loss and confusion, rather than addressing the underlying disease. Drugs like donepezil temporarily boosted neurotransmitter levels but didn’t slow the progression of amyloid and tau accumulation. The shift to anti-amyloid monoclonal antibodies represents a change in philosophy: instead of treating symptoms after neurological damage occurs, these drugs target the proteins believed to cause the damage in the first place. The distinction between early symptomatic treatment and preclinical prevention is important.
Early symptomatic treatment means patients have mild cognitive impairment or mild dementia—they’ve noticed memory problems or their doctors have identified cognitive decline—but they’re still in the earliest treatable stages. Lecanemab and donanemab work in this population. Preclinical intervention, tested in trials like AHEAD 3-45, means treating people who have amyloid in their brains but haven’t yet experienced measurable cognitive decline. This approach rests on research showing that amyloid accumulation occurs silently in the brain for 15-20 years before symptoms appear, creating a wide window for preventive treatment.
How These Drugs Work—And Why Timing Matters
Lecanemab and donanemab are monoclonal antibodies, laboratory-created proteins engineered to bind to amyloid beta and facilitate its removal from the brain. Lecanemab targets amyloid monomers and fibrils, while donanemab targets amyloid protofibrils—slightly different forms of the protein. Both work through a process called clearance, where the immune system removes tagged amyloid from brain tissue. Donanemab is administered as a monthly IV infusion, which means patients need to visit an infusion center regularly throughout treatment.
The critical limitation to understand is that these drugs work best early, before extensive neurological damage has occurred. Waiting until advanced dementia has developed, when cognitive decline is severe and widespread brain atrophy is evident, means less benefit from amyloid removal alone. This creates a clinical challenge: the disease must be caught and diagnosed early, which requires regular cognitive screening, access to amyloid biomarker testing (PET imaging or blood tests), and willingness to start treatment based on amyloid levels before significant cognitive problems appear. A warning for patients and families: amyloid accumulation is silent. You won’t feel it happening, and many people with brain amyloid never develop dementia in their lifetime—yet the current approach is to treat everyone with elevated amyloid, regardless of future risk.
Clinical Evidence—What the Trials Actually Show
The Clarity AD trial, which led to lecanemab approval, enrolled 1,795 people with mild cognitive impairment or mild dementia stage Alzheimer’s. Over 18 months, those receiving lecanemab showed a mean cognitive decline of -0.45 on the Clinical Dementia Rating-Sum of Boxes (CDR-SB) scale, compared to steeper decline in the placebo group. To put this in context: this 27% slowing of decline means that instead of experiencing six months of cognitive progression in 18 months, treated patients experienced about four months of progression. This is meaningful but modest—lecanemab does not stop Alzheimer’s or reverse damage; it slows decline.
For donanemab, the drug showed similarly modest but statistically significant benefits in early stages. Both drugs also showed concerning side effects during trials: amyloid-related imaging abnormalities (ARIA), which include brain microhemorrhages and microinfarcts, occurred in roughly 10-20% of treated patients depending on apolipoprotein E4 status (a genetic risk factor). Most were asymptomatic, but a small percentage experienced cognitive symptoms or headaches. The AHEAD 3-45 study is still enrolling and treating, but results will be crucial for understanding whether treating cognitively unimpaired people with elevated amyloid can prevent cognitive symptoms from ever emerging—a question not yet answered by completed trials.
Cost, Access, and the Affordability Challenge
Donanemab’s list price is approximately $32,000 per year, with out-of-pocket costs estimated at $6,400-$9,600 annually for people with commercial insurance and around $8,000 per year for those covered by Medicare Part D. Lecanemab costs similarly. These prices place anti-amyloid drugs out of reach for uninsured and underinsured populations, and even for insured patients, the annual out-of-pocket expense represents a significant financial burden. For comparison, many Alzheimer’s symptom-management drugs cost a few hundred to a few thousand dollars annually; anti-amyloid treatments are an order of magnitude more expensive. Insurance coverage varies.
Medicare now covers lecanemab for Medicare beneficiaries with mild cognitive impairment or mild dementia due to Alzheimer’s disease. Many commercial plans have followed, though some still restrict coverage or require prior authorization and documentation of amyloid positivity via PET scan or blood test. Access disparities exist along geographic, racial, and economic lines. Rural patients may lack nearby infusion centers and neurology specialists trained to diagnose and treat early Alzheimer’s. Black Americans and Hispanic Americans have been historically underrepresented in Alzheimer’s clinical trials and may have less access to amyloid biomarker testing, creating a two-tier system where access to these early interventions depends partly on where you live and your insurance status.
Side Effects and the Need for Close Monitoring
Amyloid-related imaging abnormalities (ARIA) are the primary safety concern with anti-amyloid drugs. ARIA-E (edema, or fluid accumulation in brain tissue) and ARIA-H (microhemorrhages) occur in a meaningful percentage of treated patients, particularly those carrying the APOE4 gene variant, which is associated with higher Alzheimer’s risk. In the lecanemab trials, ARIA-E occurred in approximately 3-8% of treated patients (compared to 1-2% in placebo), and some experienced cognitive symptoms or headaches. ARIA-H was rarer but occurred more frequently in treated groups.
These side effects necessitate baseline and ongoing MRI monitoring—typically MRI scans at baseline, weeks 4-6 of treatment, and periodically thereafter. This adds cost, requires access to imaging, and introduces additional medical appointments into the treatment regimen. Some patients experience headaches, flu-like symptoms, or infusion reactions. Because these drugs require IV infusion, patients who cannot tolerate regular medical procedures or who live far from infusion centers face practical barriers to treatment. A key warning: stopping treatment abruptly or discontinuing early because of side effects or access issues means stopping amyloid removal, and the long-term consequences of this approach are not yet fully understood.
The Experimental Pipeline—Targeting Amyloid Before Plaques Form
Beyond approved drugs, research is pursuing even earlier intervention through drugs like NU-9, which targets soluble amyloid beta oligomers—the toxic form that accumulates inside neurons before hardened plaques develop. Laboratory studies show that NU-9 effectively clears amyloid oligomers from hippocampal neurons in cultured brain cells, suggesting the potential to intervene at the earliest molecular stage of disease. Similarly, nanobody therapeutics, which are small engineered antibodies smaller and potentially more efficient than full monoclonal antibodies, have shown in 2024-2025 preclinical studies that they can reduce amyloid burden and improve cognitive performance in mouse models of Alzheimer’s.
These experimental approaches are still years away from clinical use in humans, requiring multiple phases of safety testing, dosing studies, and efficacy trials. However, the direction is clear: researchers are racing to develop treatments that work earlier and more efficiently than current anti-amyloid drugs. One practical example is the shift toward blood-based biomarkers for amyloid and tau, which allow screening without expensive PET imaging. This technological progress could eventually make it feasible to identify and treat people with preclinical Alzheimer’s on a population-wide scale.
The Future of Alzheimer’s Prevention—When Will We Treat Before Symptoms?
The AHEAD 3-45 study, which is enrolling 1,400 cognitively unimpaired adults aged 55-80 with elevated amyloid levels and will continue through 2028, will provide the first rigorous evidence of whether treating asymptomatic amyloid accumulation can prevent cognitive decline. If positive results emerge, it will shift the paradigm toward population screening and preventive treatment—essentially turning Alzheimer’s from a symptomatic disease treated late into a chronic condition managed preventively, much like how we now treat hypertension and high cholesterol before heart attacks occur.
This future raises important questions. Should everyone with elevated amyloid be treated, or only those at highest genetic risk? What is the long-term safety and tolerability of anti-amyloid therapy given for decades? Will the relatively modest slowing of cognitive decline in early symptomatic stages translate to meaningful prevention of symptoms entirely? The coming years will likely bring answers, and they will shape how aggressively we screen for and treat preclinical Alzheimer’s in the general population.
Conclusion
New drugs are already treating Alzheimer’s before all plaques have accumulated, with lecanemab and donanemab offering modest but measurable slowing of cognitive decline in early stages. These drugs represent a genuine shift from symptom management to disease-modifying treatment, though their benefits are limited to the earliest stages of disease and come with risks including brain microhemorrhages that require monitoring. Cost and access remain significant barriers, with annual out-of-pocket expenses reaching $6,400-$9,600 for many patients, creating disparities in who can access these treatments.
Looking forward, the critical question is whether treating people before symptoms develop—those with amyloid accumulation but no cognitive decline—can prevent Alzheimer’s disease entirely. Ongoing trials like AHEAD 3-45 will provide answers, and the next generation of experimental therapies targeting soluble oligomers before plaques form may eventually allow intervention even earlier in the disease cascade. If these approaches succeed, the future may bring population-wide amyloid screening and preventive treatment starting in middle age, transforming Alzheimer’s from a disease of cognitive decline into a managed chronic condition.
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For more on this topic, see Alzheimer’s Association.
