An LC-MS/MS Method for Quantification of Donanemab in Serum

Monoclonal antibodies hold significant promise for the treatment of Alzheimer's disease (AD), with donanemab being a recent therapeutic human IgG1 antibody approved for clinical use. The development and pharmacokinetic evaluation of antibody drugs necessitate accurate quantification. While immunoassays are currently used mainly by clinical trials to measure those antibody drugs for AD, they often face limitations such as cross-reactivity, insufficient specificity, and poor interlaboratory comparability. In response, researchers at Fudan University and Shanghai AB Sciex Analytical Instrument Trading Co., Ltd. (both in Shanghai, China) have developed a robust liquid chromatography-tandem mass spectrometry (LC-MS/MS) method which includes immunoaffinity enrichment for serum donanemab. A paper based on this research was published in ACS Omega.¹ which states that their method “can effectively distinguish donanemab from endogenous immunoglobulins in serum and have sufficient sensitivity.”

The global prevalence of dementia was estimated at approximately 50 million cases, and is projected to triple by 2050, with AD accounting for most these cases; once AD-related dementia is diagnosed, the reported median survival period is only 6.2 years (95% cognitive impairment: 6.0–6.5 years).^2-4 Due to its high prevalence, mortality rate, and substantial socioeconomic burden, AD has emerged as one of the most costly and debilitating diseases of the 21st century; despite this, treatment currently remains limited because of an inadequate comprehension of the disease’s pathological mechanisms. In addition, most of the available AD treatments offer only short-term symptomatic relief and do not halt the progression of the disease.^5,6

Donanemab has shown considerable efficiency in the reduction of the neuropathological hallmarks of AD─cerebral amyloid plaques, with clinical trials showing that the drug slows cognitive and functional decline by 35% in patients with early-stage AD; even greater benefits were observed in those with low to intermediate tau (a protein associated with pathologies and dementias of the nervous system such as AD) pathology.^7-9

The researchers report that their LC-MS/MS method involved: (1) immunoaffinity capture and enrichment of serum donanemab and its internal standard using protein G-conjugated magnetic beads; (2) tryptic digestion of the purified antibodies; and (3) targeted quantification of unique signature peptides via LC-MS/MS for quantification. “This method,” the authors state in their study,¹ “demonstrated acceptable performance, including a lower limit of quantification of 0.1 μg/mL, satisfactory precision (total CV < 8%), high accuracy (95-100% recovery), and a wide linear range (0.2-200 μg/mL), and is the first reported LC-MS/MS method for donanemab offering an alternative for therapeutic antibody monitoring of monoclonal antibody drugs.”

The authors pointed out that “cetuximab IS was added at the beginning of the sample preparation process and underwent the entire immunocapture and enzymatic digestion procedure alongside donanemab, which can better compensate for errors arising during sample preparation, particularly during the digestion step. However, its ability to correct chromatographic separation, ionization variability, and matrix effects is somewhat inferior to that of isotope-labeled peptides.”¹ Despite these limitations, however, the authors believe that their validation results demonstrated that the method met all acceptance criteria for accuracy, precision, and matrix effect, thus supporting the adequacy of the analogue-protein internal standard for donanemab quantification in this study.¹

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References

1. Deng, Y.; Xie, F.; Wu, W. et al. Immunocapture-LC-MS/MS Method for Quantification of the Anti-Alzheimer's Monoclonal Antibody Donanemab in Human and Mice Serum. ACS Omega 2026, 11 (6), 9138-9144. DOI: 10.1021/acsomega.5c08058
2. Alzheimer’s Disease International website. https://www.alzint.org/resource/numbers-of-people-with-dementia-worldwide/ (accessed 2026-02-25)
3. Rhodius-Meester, H. F. M.; Tijms, B. M.; Lemstra, A. W. et al. Survival in Memory Clinic Cohort is Short, Even in Young-Onset Dementia. J Neurol Neurosurg Psychiatry 2019, 90 (6), 726-728. DOI: 10.1136/jnnp-2018-318820
4. Mayeda, E. R.; Glymour, M. M.; Quesenberry, C. P. et al. Survival After Dementia Diagnosis in Five Racial/Ethnic Groups. Alzheimers Dement 2017, 13 (7), 761– 769. DOI: 10.1016/j.jalz.2016.12.008
5. Scheltens, P.; De Strooper, B.; Kivipelto, M. Alzheimer’s Disease. Lancet 2021, 397 (10284), 1577– 1590, DOI: 10.1016/S0140-6736(20)32205-4
6. Jucker, M.; Walker, L. C. Alzheimer's Disease: From Immunotherapy to Immunoprevention. Cell 2023, 186 (20), 4260-4270. DOI: 10.1016/j.cell.2023.08.021