Estimated Annual Spending on Aducanumab in the US Medicare Program

This cross-sectional study examines upper bound and lower bound annualized Medicare costs for administering aducanumab to beneficiaries with the approved indications of mild cognitive impairment or mild dementia.

presence of an informal caregiver. For example, patients with moderate dementia more frequently reported the presence of a caregiver than patients with mild dementia. Based on this work and in consultation with Dr. Kenneth Langa, the study's lead author, we also further classified dementia severity using the following threshold scores for the 27-point and 11-point scales, respectively (1) mild dementia: 5-6 and 6; (2) moderate dementia 3-4 and 7; and (3) severe dementia 0-2 and 8-11. Of note, because of some differences between the survey used in Langa's original paper and our 2016 HRS core survey used for our study, we used similar but not identical measures of dementia stage to Langa's measure. Working in consultation with Dr. Langa, we adapted our measures to match Langa's measures as closely as possible. Nonetheless, because these measures were similar but not identical to Langa's measures, we performed an additional sensitivity analysis to ensure that our own modified measures remained valid.
Specifically, we used the presence of informal caregiver as a proxy for functional status limitations and thereby dementia stage, expecting that as dementia stage worsened, there would be a monotonic increase in the presence of an informal caregiver. 2,3 Using data from our 2016 HRS core sample on informal caregivers among non-institutionalized community-dwelling older adults, we found a strong relationship between our own measures of dementia stage and the presence of informal caregivers, shown in eTable 1.
Ultimately, when we quantified patients without using dementia staging, we did obtain similar results to the more refined estimates. For the upper bound, we identified 0.95 million eligible participants with MCI and 6.7 million eligible participants with MCI or any dementia. When we applied the more refined dementia staging estimates, we identified 1.1 million eligible participants with MCI and mild dementia and 5.7 million eligible participants with MCI and mild dementia. We chose the latter, more refined estimates to be more consistent with the revised FDA label, which stated that aducanumab should be prescribed in patients with AD-related MCI or mild dementia.
Of note, per NIA-AA guidelines we did not exclude vascular dementia and instead focused on amyloid plaque burden as a marker for treatment eligibility, given that AD often co-exists with other dementia types. 5

Drug Costs
Using patient weight data from the 2016 HRS core sample, we used a patient weight-based drug cost method, more precise than the manufacturer's estimates, which had assumed average patient weight of 74 kg. While the HRS collects self-reported weights from nearly all participants, the HRS also provides actual weights for a subsample of respondents who participate in in-person interviews. To affirm the validity of the self-reported weights, we provide comparisons of summary statistics of self-reported versus actual weights among the subset of participants (n=7,733 participants) who provide both actual and self-reported weights. We also provide summary statistics for all participants who provide self-reported weights (n=20,684 participants). This exercise, shown below in eTable 2, shows similar distributions of patient weights between measured and self-reported weights. Summary statistics of self-reported versus actual patient weights were also similar among patients with MCI and dementia (data not shown). These sensitivity analyses suggest that self-reported patient weights are a reasonable proxy for actual patient weights, and these self-reported weights are what we incorporated to determine weight-based dosing.
Nevertheless, before we can explain how to incorporate these weights into our cost model, we must first explain the weight-based dosing costs for aducanumab, which have a nonlinear relationship with the patient's weight because the drug only comes in either 300 mg/3 ml or 170 mg/1.7 ml vials. In The manufacturer's press release in December 2021, aducanumab's $28,200 annual whole sale acquisition cost (e.g., "list price" [reduced from the previous $56,000 per year announced in June 2021]) was based on the assumption that the average patient with MCI or mild dementia would weigh 74 kilograms. 7

Associated Ancillary Health Services Costs
Per review of published FDA documents and reviews of clinical trial data, we assumed each patient would receive a one-time PET scan to screen for plaque, and, of those, 37%-68% would show substantial plaque burden based on population studies of patients with MCI and dementia. 5 Therefore, the final average unit cost for IV infusions applied non-facility professional fees 50% of the time and applied facility fees plus professional fees the remaining 50% of the time. We applied facility fees 15% of the time for all other remaining outpatient services such as neurology visits based on the MedPAC report finding that 15% of outpatient oncology visits occurred in hospital outpatient department settings. 12 In addition, to estimate facility fees for diagnostic imaging, we used published data from the Brookings Institution, which found that 69% of MRIs in 2018 occurred in the hospital outpatient department setting. Therefore, we incorporated facility fees to 70% of MRI and PET scan studies. 13 Finally, approximately 9% (9.1%) of trial participants dropped out of the treatment arm for any reason, 190 range of anticipated out-of-pocket costs. Nevertheless, we can say these beneficiaries will be expected to also pay out of pocket, but not less than $0 and not more than $6,864.66. The caveat, as noted above, is that Medicare Advantage beneficiaries might pay more (or less) than this upper limit, however, the total costs would remain the same regardless of the coverage split policy. Unfortunately, we cannot provide more precise estimates of out-of-pocket costs than an estimated range until private supplemental insurance and Medicare Advantage coverage policies are announced.