Abstract
Multiple myeloma (MM) is a neoplasm of plasma cells that secrete patient specific monoclonal immunoglobulins. A recognized problem in MM treatment is the early recognition of minimal residual disease (MRD), the major cause of relapse. Current MRD detection methods (multiparameter flow cytometry and next generation sequencing) are based on the analysis of bone marrow plasma cells. Both methods cannot detect extramedullary disease and are unsuitable for serial measurements. We describe the methodology to generate high affinity DNA aptamers that are specific to a patient’s monoclonal Fab region. Such aptamers are 2000-fold more sensitive than immunofixation electrophoresis and enabled detection and quantification of MRD in serum when conventional MRD methods assessed complete remission. The aptamer isolation process that requires small volumes of serum is automatable, and Fab specific aptamers are adaptable to multiple diagnostic formats including point-of-care devices.
Highlights
Multiple myeloma (MM) is a neoplasm of plasma cells that secrete patient specific monoclonal immunoglobulins
The overall strategy was to first isolate target-specific aptamers by eliminating binders to common immunoglobulin G (IgG) features or beads with two counter-selection steps per systematic evolution of ligands by exponential enrichment (SELEX) round (Fig. 1a left), and to select aptamers that were most sensitive in serum
Sequences were tested by enzyme linked oligonucleotide assay (ELONA) and, based on results obtained for binding to daratumumab in buffer and serum, distributed into two families (Supplementary Fig. 1e)
Summary
Multiple myeloma (MM) is a neoplasm of plasma cells that secrete patient specific monoclonal immunoglobulins. Current MRD detection methods (multiparameter flow cytometry and generation sequencing) are based on the analysis of bone marrow plasma cells. Both methods cannot detect extramedullary disease and are unsuitable for serial measurements. We describe the methodology to generate high affinity DNA aptamers that are specific to a patient’s monoclonal Fab region Such aptamers are 2000-fold more sensitive than immunofixation electrophoresis and enabled detection and quantification of MRD in serum when conventional MRD methods assessed complete remission. Several studies showed that patients with negative MRD status attain superior clinical outcomes[3,4,5,6,7] These findings prompted the international myeloma working group (IMWG) to include MRD detection as a measure of response[8] and regulatory agencies, Federal Drug. Mass spectrometry is 100-fold more sensitive than IFE (LoD 0.0001 g dl−1) but is not suitable for MRD detection because of its inaccuracy in the presence of endogenous polyclonal immunoglobulin levels over 0.8 g dl−1 (i.e., within normal range)[19,20,21,22]
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