An article by K Bloem et al at three institutions in the Netherlands, published in the June 2018 edition of Bioanalysis, compared Mitra® devices with VAMS® technology to dried blood spot (DBS) cards for measuring seven known monoclonal antibodies (MAbs) drugs in blood. The paper is entitled “Capillary blood microsampling to determine serum biopharmaceutical concentration: Mitra® microsampler vs dried blood spot.”
This study showed that excellent extraction recoveries were observed for both matrices, but Mitra was reported to be more precise and easier to work with compared to the legacy dried blood technology.
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In November 2022, the BBC reported that the National Health Service (NHS) had reached a commercial deal to provide a triple-negative breast cancer treatment drug alongside other chemotherapeutic agents.
Triple-negative breast cancer affects 8,000 women per year and accounts for 15% of all breast cancers. The drug pembrolizumab, a monoclonal antibody therapeutic manufactured by Merck Sharpe and Dohme, acts as a Programmed cell death protein 1, also known as PD-1 receptor blocks or the PD-1 ligand (PD-1L), which block the PD-1/PD-1L pathway and remove immune response inhibition, allowing the immune system to fight cancer cells.
The Rise of MAbs for Targeted Disease Treatment
There has been a steady increase in the development and approval of novel MAb therapeutics. Indeed, in October 2022 it was reported that since 1985 there have been over 100 MAbs approved as drug therapies and new MAb drug registrations are continuing to increase.
Like many other drugs (small and large) optimizing the dosing of MAb therapeutics is critical to ensure dug efficacy and minimize side effects. The paper by K Bloem et al highlighted that TNF inhibitor MAb therapies, such as adalimumab (ADL) and infliximab, have been reported to require dose adjustments to allow for a narrow therapeutic range.
The authors highlighted that they had developed a methodology to measure MAbs from dried blood spots (DBS). They reported this eliminated what they describe as “the cumbersome logistics of handling wet plasma / serum samples” including cold chain shipping.
In previous work, the same group reported that when working with a fixed hematocrit level (0.368 l/l), incomplete recoveries were observed when punching a fixed volume from spots of different dimensions.
They solved the issue by eluting the whole spot and scanning the size of spot, to allow them to mathematically compensate for what they called the HCT-dependent variation in blood flow. Also, as MAbs are excluded from the hematocrit fraction, they used hemaglobin (Hb) measurement to correct for the HCT fraction, a technique used by other groups as discussed in a previous blog.
Due to the volumetric nature of VAMS devices, the research group wanted to compare the performance of these to DBS to try to circumvent the hematocrit issues associated with DBS.
MAbs Study Methods and Findings
Seven common MAbs drugs (adalimumab, infliximab, natalizumab, rituximab, tocilizumab, ustekinumab, vedolizumab) were selected.
The group evaluated the volumetric nature of the VAMS devices by weighing tips or sampler bodies before and after sampling of either blood or water. They reported an accuracy for blood of 107% (SD:3%) compared to the Neoteryx QC values with no %HCT bias. Sampling water, on the other hand, showed greater accuracy (101%. SD 4%).
When comparing blood collected from capillary blood, the volumes didn’t differ from the Neoteryx reported volumes.
Fixed volumes of blood (20 µL) from a range of hematocrits (30-50%) spiked when the 7 MAbs were pipetted onto DBS cards, then dried, and the whole blood spot was cut out for extraction. For Mitra, the samplers (20 µL) were used to sample the same blood, also dried and then extracted.
Extraction from both DBS and the Mitra-VAMS devices was in a mixture of BPS, Tween and sodium azide. The samples were then analyzed by previously validated immunoassays (ELISA and RIA).
Both hematocrit and potassium were evaluated as a means to correct for hematocrit. Both approaches of HCT correction yielded similar results.
Recovery calculations, compared to plasma samples, were then conducted from both dried blood matrices and HCT compensation was applied. For adalimumab (5μg/ml in plasma) mean recovery values from dried blood were reported to be 101% (±3.9%) for VAMS and 99.6% (±4.8%).
Analyte stability was also evaluated.
No significant loss of signal was seen on both matrices (95.2% (SD = 10.2%) for VAMS and 92.9% (SD=11.7%) DBS) at room temperature or 4 °C degrees for 1 month and 2 days at 37 °C.
Study Author Discussion and Conclusions
Both matrices yielded similar results, but CVs were reported as somewhat larger for DBS.
It was difficult to conclude why they saw a slightly larger volume absorbed (23 vs 21.5 µL) when sampling from a vial vs a fingertip.
Of all blood samples used (including from different lots) they saw a <7% difference in values obtained on Mitra-VAMS devices.
They recommended good training of study participants if sampling with Mitra-VAMS.
VAMS was a good alternative to DBS, with lower sample variation in the study.
VAMS samples were found to be less labor intensive.
The work conducted by K Bloem et al demonstrated that the seven monoclonal antibodies which were evaluated eluted almost quantitatively from both Mitra-VAMS and DBS. Furthermore, the extracts were found to be stable at room temperature for a month. Moreover, this extraction recovery was independent of hematocrit.
The team had previously developed an excellent method for obtaining quantitation from DBS cards, however, this required either pipetting a constant volume onto the cards or conducting a whole spot extraction. Moreover, in previous studies, the team had employed imaging to measure spot size to correct for differences in concentration when spots of different volumes were applied to the card and when sub-punching was involved. This "spot spread" phenomenon was also highlighted in a previous study by AJ Lawson et al when evaluating issues with DBS for newborn screening and was reported to be a source of inaccuracy when using dried blood spot cards.
As shown in this study paper by K Bloem et al, as well as in many other publications, the volumetric nature of devices such as Mitra® and hemaPEN® overcome many of the hurdles that must be overcome with DBS samples, leading to validated methods on many classes of analyte.
This article was summarized for our readers by James Rudge, PhD, Neoteryx Technical Director. This is curated content. To learn more about the important research outlined in this blog, visit the original article in Bioanalysis.