A Sub-picogram Quantification Method for Desmopressin in Plasma using the AB SCIEX Triple Quad 6500 System A high-throughput method for detecting ultra-low levels (0.5 pg/ml) of a therapeutic peptide in human plasma using an AB SCIEX Triple Quad 6500 LC/MS/MS System and UHPLC Chromatography Rahul Baghla 1, Swati Guttikar 2, Dharmesh Patel 2, Abhishek Gandhi 2, Anoop Kumar 1, and Manoj Pillai 1 1 AB SCIEX, 121, Udyog Vihar, Phase IV, Gurgaon, Haryana, India 2 Veeda Clinical Research India, Ahmadabad, India Key challenges of desmopressin quantitation Impaired sensitivity in complex matrices Very low-level peptide detection (sub-pg/ml) can be suppressed by high background and competing ions in biological samples. Poor data quality Precision and accuracy can be compromised at low peptide levels, giving results below accepted bioanalytical standards. Key benefits of peptide quantitation on the AB SCIEX Triple Quad 6500 LC/MS/MS System Technology High sensitivity Very low level peptide detection in human plasma (at sub pg/ml concentrations) is enabled by IonDrive TM Technology. Excellent precision and accuracy at the LOQ level Data quality (for LOQ, LQC, MQC and HQC levels) met or exceeded USFDA bioanalytical method validation criteria. Figure 1: Triple Quad TM 6500 System. High throughput High sensitivity was achieved under highflow conditions (0.750 ml/min), optimal for multi-sample analysis. Unique features of the Triple Quad TM 6500 System for low-level peptide detection IonDrive Turbo V Source Increased ionization efficiency and heat transfer contribute to sensitivity enhancements, including improved signal-to-noise. IonDrive QJet Ion Guide Increased ion sampling improves method efficiency and ruggedness. IonDrive High Energy Detector Innovative detector technology boosts dynamic range and sensitivity. Figure 2: Unique features of Triple Quad TM 6500 System. p 1
Figure 3. Structure of desmopressin. Figure 4. Structure of internal standard, desmopressin-d 5. Introduction Low-level peptide detection has a number of applications in clinical studies and in the pharmaceutical discovery and development processes, highlighting the increasing relevance of sensitive and selective mass spectrometric platforms in the bioanalytical laboratory. Regulatory requirements demand intensive and rigorous quantitation of therapeutic peptides during pharmacokinetic, bioequivalence, and metabolic studies. In addition, drug discovery and development strategies seek to monitor and quantitate peptide biomarkers in complex biological samples, necessitating highly-selective separations of low concentration analytes from high background noise and prominent levels of competing ions. The AB SCIEX Triple Quad 6500 LC/MS/MS System, equipped with IonDrive Technology for enhanced detector performance, has demonstrated particular strength in the detection of low-level amounts of small molecules, and in this study, we extend the augmented signal-to-noise, broad dynamic range, and the efficient method development capacities of the Triple Quad 6500 System to the detection of sub-picogram levels of a therapeutic peptide under high-throughput conditions. We have developed a reliable, fast, and sensitive method for the detection of a nine-amino-acid peptide, desmopressin (1-desamino-8-D-arginine, vasopressin), which is structurally similar to the hormone arginine vasopressin, but contains a deaminated first amino acid and dextro-arginine (rather than levo-) in the eighth position. Therapeutically, desmopressin reduces urine production, restricting water elimination from the kidneys by binding to the V2 receptors in renal-collecting ducts, thereby facilitating increased reabsorption. The longer half-life of desmopressin over vasopressin offers some therapeutic advantages, and typical doses of desmopressin to treat diabetes insipidus and bedwetting range between 0.200 to 1.20 mg per day, resulting in very low plasma concentrations. In this bioanalytical study, we have established a sensitive and selective LC/MS/MS method for the quantitation of desmopressin in human plasma, detecting peptide levels as low as 0.500 pg/ml with excellent accuracy and precision. This technique should facilitate additional mass spectrometric method development for accurate quantitation of a range of therapeutic peptides in biological matrices on the Triple Quad 6500 System. Materials and Methods Sample Preparation Plasma samples (1000 µl) containing 2% desmopressin standard and 50µL internal standard were vortexed and spiked with 50µL of orthophosphoric acid (OPA). Samples were extracted on weak cation exchange cartridges conditioned with methanol followed by 100mM ammonium acetate solution. After loading, samples were washed in three steps: 1) 2% OPA:methanol (80:20 v/v); 2) 2% NaOH:Methanol (60:40 v/v); and 3) water:methanol (60:40 v/v). Analytes were eluted with 5% acetic acid in methanol, dried under nitrogen at 40 ºC, and reconstituted with 0.1% acetic acid (150 µl) prior to Table 1. Compound-dependent parameters for desmopressin and desmopressin-d 5 on the Triple Quad 6500 System Instrument Parameter Desmopressin Desmopressin-d 5 CUR 40 40 TEM 600 C 600 C ISV 5500 5500 GS1 50 50 GS2 60 60 CAD 10 10 DP 50 71 EP 10 10 CE 23 23 CXP 12 12 p 2
analysis by mass spectrometry. Chromatography LC System: GL Sciences LC 800 System Column: Agilent 300 Extend C 18 (150 x 2.1 mm, 3.5 μm) Column Temp.: 40 C Injection: 50 μl Flow Rate: 0.750 ml/min Mobile phase: A) water, 0.1 % acetic acid B) acetonitrile, 0.1% acetic acid Gradient: Time/min A% B% 0 85 15 1.5 85 15 3.5 50 50 3.51 85 15 5 85 15 A) B) Mass Spectrometry Analysis of desmopressin and desmopressin-d5 required different mass spectrometry settings (Table 1). The MRM transition monitored for desmopressin was m/z 525.4/328.0 and 537.9/328.0 at a dwell time of 50 msec. Five replicate injections were performed at all concentrations. Data System: Interface: Triple Quad 6500 System IonDrive Turbo V Source in positive ion mode Data processing All Triple Quad 6500 System data was processed using MultiQuant Software.. The concentration curves were analyzed using a linear fit with a 1/x 2 weighting. Data acquired on the Triple Quad 6500 System was processed using the quantitation tools within Analyst 1.6 Software. Figure 5. Desmopressin MRM signal (shown in left side ) panes for multiple concentrations and Desmopressin D5 MRM signal ( Shown in right side panes). Results and Discussion Method analysis and data quality The desmopressin quantitative assay was validated by generating an internal standard curve using standards alone and standards spiked into human plasma. Left side pane of Figure 5 shows representative peaks for A) blank extract, B) plasma spiked with 0.5 pg/ml desmopressin and the right side pane of Figure 5 shows the MRM response from the internal standard. Standard concentrations varied from 0.5 to 100 pg/ml generating an LLOQ in plasma of 0.5 pg/ml resulting in a signal to noise ratio of 60.7 (Figure 6). Reproducibility of the assay was assessed by multiple technical replicates of the same sample (n = 6, Figure 7) on an LLOQ quality control sample of 0.5 pg/ml. The calibration curve for desmopressin in plasma shows excellent linearity over 2.5 orders of magnitude concentration range with an r value of >0.99 (Figure 8). Figure 6: High signal-to-noise ratio for desmopressin.. The signalto-noise ratio was calculated for desmopressin extracted from plasma at LLOQ level (0.500 pg/ml in plasma, S/N = 60.7). p 3
Figure 8: Calibration curve of desmopressin in plasma from 0.500 pg/ml to 100.760 pg/ml. The method has shown excellent linearity over the concentration range with r = 0.9996. mean accuracy was calculated to be 108% with a %CV of 10.5%. The percent recovery and plasma matrix effect were evaluated by comparing the peak areas for standard curve samples with and without plasma (Table 5). The mean percent recovery was calculated to be 93%. The recovery of the internal standard was calculated to be 78% (Table 6). Figure 7: Desmopressin technical replicates. Chromatograms of six LLOQ quality control samples (0.502 pg/ml) for precision and accuracy calculations are shown (Table 2). The data collected for a single calibration curve are presented in Table 2. Analyte retention time and internal standard peak retention times were consistent, with both eluting at approximately 2.6 min. The calculated concentration correlates well with the actual spiked-analyte concentration in plasma matrix with a percent accuracy of the standard curve very close to 100% for all concentrations of standard, and the quality control samples had a percent accuracy of 110%. Table 3 shows the individual statistics for three separate batch runs of desmopressin. Data from Table 2 are taken from Batch 3. Table 4 shows the mean values for the percent accuracy and % CV for three separate batch runs. For the LLOQ quality control, the p 4
Sample ID Sample Type Table 2. Data quality analysis of desmopressin from human plasma samples Analyte Retention Time (min) Analyte Peak Area IS Retention Time (min) IS Peak Area Area Ratio Analyte Conc. (pg/ml) Calculated Conc. (pg/ml) AQM 18122013 Unknown 2.60 119046 2.57 119,422 0.997 N/A 60.309 N/A % Accuracy BLANK 01 Blank 0 0 0 0 #DIV/0! N/A #DIV/0! N/A BLANK+IS 01 Unknown 0 0 2.57 120,418 0 N/A No Peak N/A STD A 01 Standard 2.61 2,148 2.58 141,964 0.015 0.500 0.507 101.40 STD B 01 Standard 2.60 3,567 2.57 157,232 0.023 1.000 0.967 96.73 STD C 01 Standard 2.60 8,190 2.57 168,629 0.049 2.498 2.544 101.85 STD D 01 Standard 2.60 20,050 2.57 180,711 0.111 6.448 6.344 98.39 STD E 01 Standard 2.60 51,086 2.57 187,669 0.272 16.122 16.167 100.28 STD F 01 Standard 2.60 94,706 2.57 145,728 0.65 40.304 39.173 97.19 STD G 01 Standard 2.60 218,389 2.57 163,086 1.339 80.608 81.158 100.68 STD H 01 Standard 2.60 321,985 2.57 187,366 1.718 100.760 104.268 103.48 LLOQ QC 01 Qual. Control 2.62 2,395 2.58 153,948 0.016 0.502 0.533 106.19 LQC 01 Qual. Control 2.60 5,296 2.57 160,710 0.033 1.492 1.593 106.75 MQC 01 Qual. Control 2.60 114,782 2.57 180,711 0.635 40.692 38.277 94.07 HQC 01 Qual. Control 2.60 244,061 2.57 183,047 1.333 81.384 80.806 99.29 LLOQ QC 02 Qual. Control 2.63 2,379 2.58 152,201 0.016 0.502 0.538 107.11 LQC 02 Qual. Control 2.6 5,433 2.57 154,564 0.035 1.492 1.727 115.74 MQC 02 Qual. Control 2.60 119,912 2.57 183,163 0.655 40.692 39.465 96.99 HQC 02 Qual. Control 2.60 227,932 2.57 179,913 1.267 81.384 76.760 94.32 LLOQ QC 03 Qual. Control 2.61 2,387 2.57 145,187 0.016 0.502 0.587 116.93 LQC 03 Qual. Control 2.61 5,266 2.58 153,330 0.034 1.492 1.678 112.44 MQC 03 Qual. Control 2.60 117,712 2.57 178,847 0.658 40.692 39.678 97.51 HQC 03 Qual. Control 2.60 228,311 2.58 175,270 1.303 81.384 78.936 96.99 LLOQ QC 04 Qual. Control 2.61 2,203 2.57 142,754 0.015 0.502 0.526 104.70 LQC 04 Qual. Control 2.61 4,940 2.58 155,534 0.032 1.492 1.520 101.90 MQC 04 Qual. Control 2.60 102,226 2.58 156,822 0.652 40.692 39.294 96.56 HQC 04 Qual. Control 2.61 222,646 2.58 167,585 1.329 81.384 80.516 98.93 LLOQ QC 05 Qual. Control 2.62 2,323 2.58 144,891 0.016 0.502 0.562 111.96 LQC 05 Qual. Control 2.61 5,299 2.58 161,308 0.033 1.492 1.587 106.33 MQC 05 Qual. Control 2.60 101,960 2.58 157,530 0.647 40.692 39.013 95.87 HQC 05 Qual. Control 2.60 225,914 2.58 169,163 1.335 81.384 80.937 99.45 LLOQ QC 06 Qual. Control 2.62 2,309 2.58 144,368 0.016 0.502 0.560 111.50 LQC 06 Qual. Control 2.61 5,414 2.58 161,549 0.034 1.492 1.627 109.05 MQC 06 Qual. Control 2.61 103,636 2.58 159,865 0.648 40.692 39.076 96.03 HQC 06 Qual. Control 2.60 223,129 2.58 168,042 1.328 81.384 80.471 98.88 Table 2. Full analysis of precision and accuracy measurements for desmopressin (batch 1 samples) in human plasma. p 5
PA BATCH 01 PA BATCH 02 Table 3: Precision and accuracy for multi-batch desmopressin technical replicates Nominal Concentration (pg/ml) DESMOPRESSIN LLOQ QC LQC MQC HQC 0.502 1.492 40.692 81.384 1 0.533 1.593 38.277 80.806 2 0.538 1.727 39.465 76.760 3 0.587 1.678 39.678 78.936 4 0.526 1.520 39.294 80.516 5 0.562 1.587 39.013 80.937 6 0.560 1.627 39.076 80.471 Mean 0.5510 1.6220 39.1338 79.7377 S.D (+/-) 0.02287 0.07302 0.48653 1.62681 C.V. (%) 4.15 4.50 1.24 2.04 % Nominal 109.76 108.71 96.17 97.98 N 6 6 6 6 7 0.519 1.590 39.191 79.548 8 0.491 1.283 40.359 82.140 9 0.490 1.509 39.486 78.094 10 0.571 1.436 39.828 78.854 11 0.526 1.387 40.624 78.472 12 0.680 1.319 40.355 79.635 Mean 0.5462 1.4207 39.9738 79.4572 S.D (+/-) 0.0719 0.1159 0.5636 1.4443 C.V. (%) 13.17 8.16 1.41 1.82 % Nominal 108.80 95.22 98.24 97.63 N 6 6 6 6 Table 4. Precision and accuracy of desmopressin technical replicates measured as a single group Nominal Concentration (pg/ml) Desmopressin LLOQ QC LQC MQC HQC Sample 0.502 1.492 40.692 81.384 1 0.533 1.593 38.277 80.806 2 0.538 1.727 39.465 76.760 3 0.587 1.678 39.678 78.936 4 0.526 1.520 39.294 80.516 5 0.562 1.587 39.013 80.937 6 0.560 1.627 39.076 80.471 7 0.519 1.590 39.191 79.548 8 0.491 1.283 40.359 82.140 9 0.490 1.509 39.486 78.094 10 0.571 1.436 39.828 78.854 11 0.526 1.387 40.624 78.472 12 0.680 1.319 40.355 79.635 13 0.418 1.364 41.098 79.992 14 0.602 1.446 39.814 80.103 15 0.520 1.399 40.988 79.854 16 0.463 1.350 39.391 80.937 17 0.563 1.274 39.960 80.577 18 0.528 1.332 39.188 82.162 Mean 0.5376 1.4678 39.7269 79.9330 S.D (+/-) 0.05691 0.14051 0.73499 1.36511 C.V. (%) 10.56 9.59 1.85 1.71 % Nominal 107.57 98.53 97.64 98.21 N 18 18 18 18 Table 4: Mean precision and accuracy calculations for desmopressin for three batches of measurements from different days. PA BATCH 03 13 0.418 1.364 41.098 79.992 14 0.602 1.446 39.814 80.103 15 0.520 1.399 40.988 79.854 16 0.463 1.350 39.391 80.937 17 0.563 1.274 39.960 80.577 18 0.528 1.332 39.188 82.162 Mean 0.5157 1.3608 40.0732 80.6042 S.D (+/-) 0.05867 0.05867 0.80200 0.86337 C.V. (%) 11.38 4.31 2.00 1.07 % Nominal 102.73 91.21 98.48 99.04 N 6 0 6 6 Table 3: Precision and accuracy calculations for individual batches of desmopressin samples. p 6
Conclusions A highly sensitive and high-throughput bioanalytical method was developed and validated for the detection of ultra-low-levels of the therapeutic peptide, desmopressin, in human plasma on the AB SCIEX Triple Quad 6500 LC/MS/MS System. Method sensitivity for desmopressin detection was exceptional (0.5 pg/ml or 2.5 fg on column), and demonstrated high-reproducibility and cost effectiveness with good precision and accuracy. Analyte recovery is 92.7%, even under high-throughput conditions. Total run time for each sample was only 5 min, using a flow rate rapid enough for high-throughput analysis in the bioanalytical laboratory. References 1. Friedman, F and Weiss JP. Desmopressin in the treatment of nocturia: clinical evidence and experience. Therapeutic Advances in Urology. 2013; 5(6): 310-317. Table 6. Recovery of internal standard desmopressin-d 5 PA Batch No. 03 Sample ID Extracted (MQC) Unextracted 01, 013 251,778 301,602 02, 014 241,864 297,780 03, 015 253,224 305,778 04, 016 256,487 313,985 05, 017 217,971 316,703 06, 018 208,773 300,178 Mean 238,349.5 306,004.3 S.D 20,164.07 773,5.25 % C.V. 8.46 2.53 N 6 6 % Recovery 77.89 Table 6: Recovery for desmopressin-d 5 from plasma at the MQC level was 77.89%. Acknowledgements The authors are indebted to Dr.Venu Madhav, Chief Operating Officer (COO), Veeda Clinical Research, India, for his encouragement and support for the successful completion of the work. 2. Neudert, L, Zaugg, M, Wood, S, Struwe, P. A high sensitivity dual solid phase extraction LC/MS/MS assay for the determination of the therapeutic peptide desmopressin in human plasma. Celerion white paper. Table 5. Recovery of desmopressin from human plasma, batch 03 LQC RESPONSE MQC RESPONSE HQC RESPONSE Sample ID Extracted Unextracted Extracted Unextracted Extracted Unextracted 01, 013 5,923 6,282 145,169 148,017 292,234 290,315 02, 014 6,645 6,157 135,153 145,270 267,547 291,138 03, 015 6,572 6,319 145,616 153,630 302,953 288,730 04, 016 5,879 6,446 141,823 156,298 270,214 318,201 05, 017 5,823 6,072 122,242 154,238 240,994 304,383 06, 018 5,263 5,825 114,853 146,425 260,462 287,647 Mean 6,017.5 6,183.5 134142.7 150,646.3 272,400.7 296,735.7 S.D 517.00 218.46 12860.35 4,634.26 22,289.26 12,153.15 C.V 8.59 3.53 9.59 3.08 8.18 4.10 N 6 6 6 6 6 6 % Recovery 97.32 89.04 91.80 Mean 92.72 SD (+/-) 4.216 CV(%) 4.547 N 3 Table 5: Recovery of desmopressin from plasma at three different concentrations, LQC, MQC and HQC, was 92.72%. For Research Use Only. Not for use in diagnostic procedures. 2014 AB SCIEX. The trademarks mentioned herein are the property of AB Sciex Pte. Ltd. or their respective owners. AB SCIEX is being used under license. Publication number: 9490114-01 p 7