Regen-Cov^® Antibody Cocktail Bioanalytical Strategy: Comparison of Lc-Mrm-Ms and Immunoassay Methods for Drug Quantification

Figures & data

Figure 1. The linear regression between the ECL immunoassay and the LC-MRM-MS assay results.

(A) For casirivimab, the correlation coefficient between the two methods is r²=0.9568, p<0.0001 and slope=1.014. (B) For imdevimab, the correlation coefficient between the two methods is r²=0.9562, p<0.0001, and slope=1.117. The 95% prediction intervals are shown with dotted lines.

Figure 2. The frequency distribution of logarithmic transformed (Log10) differences between the ECL immunoassay and the LC-MRM-MS assay for casirivimab and imdevimab.

The D'Agostino and Pearson test for normal distribution (A) for casirivimab (p=0.2394) and (B) for imdevimab (p=0.2099).

Figure 3. Bland-Altman analyses for the ECL immunoassay and the LC-MRM-MS assay.

(A & B) The x-axis in each plot is the mean of the two measures and the y-axis is the difference between methods (ECL immunoassay result minus LC-MRM-MS assay result). (A) For casirivimab (n=424), the bias from immunoassay to LC-MRM-MS (±SD) is -4.2 (±61.3; 95% limits of agreement -124.3 to 115.9). (B) For imdevimab (n=444), the bias from immunoassay to LC-MRM-MS (±SD) is -23.6 (±68.7; 95% limits of agreement -158.2 to 111.0). (C & D) The x-axis in each plot is the average of the two measures and the y-axis is the percentage of the values on the axis ([ECL immunoassay result minus LC-MRM-MS assay result], divided by mean and expressed as a percentage). (C) For casirivimab, the bias from immunoassay to LC-MRM-MS (±SD) is -0.5% (±16.2; 95% limits of agreement -32.2 to 31.2). (D) For imdevimab, the bias from immunoassay to LC-MRM-MS (±SD) is -6.0% (±13.17; 95% limits of agreement -31.8 to 19.9).

Figure 4. Comparison of drug concentration in serum by time for casirivimab (left) and imdevimab (right) in hospitalized (Study 2066, top) and non-hospitalized (Study 2067, bottom) patients with SARS-CoV-2.

Error bars indicate standard deviation.

Figure 5. Pharmacokinetic parameters per platform for each casirivimab (left) and imdevimab (right) in non-hospitalized patients with SARS-CoV-2 diagnosis (Study 2067).

For the 1.2 gand 4g doses per mAb, the following parameters are presented as mean±standard deviation (SD) with number of subjects identified for each calculation (n): (top) maximum drug concentration in blood (C_max), (middle) area under concentration by time curve up to 28days post-dose (AUC_0–28), and (bottom) drug concentration in serum at 28days after dose (C₂₈).

Table 1. Analytical parameters of the LC-MRM-MS and ECL immunoassay platforms.

Method	Analyte	LLOQ (μg/ml)	Accuracy (%)	Precision (%)	Range (μg/ml)	Development time	Analysis throughput
LC-MRM-MS	Casirivimab	20	95–103	3–13	20–2000	Shorter	Lower
	Imdevimab	10	96–106	3–9	10–2000
ECL immunoassay	Casirivimab	0.156	93–103	7–11	0.156–10	Longer	Higher
	Imdevimab	0.156	94–103	8–10	0.156–10