Volumetric absorptive microsampling coupled with hybridization LC-MS/MS for quantitation of antisense oligonucleotides.

Background: Volumetric absorptive microsampling has emerged as a less invasive alternative to venous sampling for small-molecule pharmacokinetic studies, but its application to novel therapeutics such as antisense oligonucleotides (ASOs) is not well-established. Results: A workflow was developed using Mitra microsampling coupled with hybridization LC-MS/MS for accurate determination of fomivirsen, a 21-mer ASO, in human blood. Quantitative recovery was achieved regardless of blood hematocrit level or microsample age by implementing impact-assisted extraction. A thorough method evaluation confirmed sensitivity, linearity, precision/accuracy, matrix effect, metabolite interference and four months of microsample stability. Conclusion: The combined impact-assisted extraction and hybridization LC-MS/MS workflow demonstrated the successful quantitation of fomivirsen, establishing the validity and applicability of the approach for ASO drug candidates.

A validated capillary microsampling liquid chromatography-tandem mass spectrometry method for quantification of antisense oligonucleotides in mouse serum.

Background: Capillary microsampling (CMS) has been used for quantitative bioanalysis of small molecules; however, there is no report of applying this technique in the bioanalysis of antisense oligonucleotides (ASOs). Results: A CMS liquid chromatography-tandem mass spectrometry method was successfully developed and validated for the quantification of ASO1 in mouse serum. The validated method was applied in a safety study in juvenile mice. Equivalent performance between CMS samples and conventional samples was demonstrated in the mouse study. Conclusion: This work is the first to report using CMS for liquid chromatography-tandem mass spectrometry quantitative bioanalysis of ASOs. The validated CMS method was successfully applied to support good laboratory practice safety studies in mice and the CMS strategy has subsequently been applied to other ASOs.

A Novel Hybridization LC-MS/MS Methodology for Quantification of siRNA in Plasma, CSF and Tissue Samples.

Therapeutic oligonucleotides, such as antisense oligonucleotide (ASO) and small interfering RNA (siRNA), are a new class of therapeutics rapidly growing in drug discovery and development. A sensitive and reliable method to quantify oligonucleotides in biological samples is critical to study their pharmacokinetic and pharmacodynamic properties. Hybridization LC-MS/MS was recently established as a highly sensitive and specific methodology for the quantification of single-stranded oligonucleotides, e.g., ASOs, in various biological matrices. However, there is no report of this methodology for the bioanalysis of double-stranded oligonucleotides (e.g., siRNA). In this work, we investigated hybridization LC-MS/MS methodology for the quantification of double-stranded oligonucleotides in biological samples using an siRNA compound, siRNA-01, as the test compound. The commonly used DNA capture probe and a new peptide nucleic acid (PNA) probe were compared for the hybridization extraction of siRNA-01 under different conditions. The PNA probe achieved better extraction recovery than the DNA probe, especially for high concentration samples, which may be due to its stronger hybridization affinity. The optimized hybridization method using the PNA probe was successfully qualified for the quantitation of siRNA-01 in monkey plasma, cerebrospinal fluid (CSF), and tissue homogenates over the range of 2.00-1000 ng/mL. This work is the first report of the hybridization LC-MS/MS methodology for the quantification of double-stranded oligonucleotides. The developed methodology will be applied to pharmacokinetic and toxicokinetic studies of siRNA-01. This novel methodology can also be used for the quantitative bioanalysis of other double-stranded oligonucleotides.

Validation and application of hybridization liquid chromatography-tandem mass spectrometry methods for quantitative bioanalysis of antisense oligonucleotides.

Background: Antisense oligonucleotide (ASO), an emerging modality in drug research and development, demands accurate and sensitive bioanalysis to understand its pharmacokinetic and pharmacodynamic properties. Results: By combining the advantages of both ligand binding and liquid chromatography-mass spectrometry/tandem mass (LC-MS/MS), hybridization LC-MS/MS methods were successfully developed and validated/qualified in a good lab practice (GLP) environment for the quantitation of an ASO drug candidate in monkey serum, cerebrospinal fluid (CSF) and tissues in the range of 0.5-500 ng/ml. Special treatment of CSF samples was employed to mitigate nonspecific binding, improve long-term storage stability and enable the usage of artificial CSF as a more accessible surrogate matrix. The method was also qualified and applied to ASO quantitation in various monkey tissue samples using a cocktail tissue homogenate as a surrogate matrix. Conclusion: This work was the first reported GLP validation and application of ASO bioanalysis using the hybridization LC-MS/MS platform.

Orthogonal analysis of dystrophin protein and mRNA as a surrogate outcome for drug development.

Aim: Detection of drug-induced dystrophin in patient muscle biopsy is a surrogate outcome measure for Duchenne muscular dystrophy. We sought to establish and validate an orthogonal approach to measurement of dystrophin protein and RNA in muscle biopsies. Materials & methods: Validated methods were developed for dystrophin western blotting, mass spectrometry, immunostaining and reverse transcriptase PCR of biopsy mRNA using muscle biopsy standards. Results: Both western blotting and mass spectrometry validated methods demonstrated good linearity, and acceptable precision and accuracy with a lower limit of quantitation at 1%. Immunostaining and reverse transcriptase PCR methods were shown to be reliable. Conclusion: The described orthogonal approach is sufficient to support measures of dystrophin as a surrogate outcome in a clinical trial.

Application of high-resolution MS in the quantification of a therapeutic monoclonal antibody in human plasma.

BACKGROUND: Monoclonal antibodies are the fastest growing class of protein therapeutics. Ligand-binding assays have been the technique of choice for the quantification of these large proteins; however, LC-MS and more recently LC-HRMS have been gaining momentum as robust alternatives for the bioanalysis of antibodies in biological matrices. RESULTS: Optimization of sample preparation and LC-HRMS analysis in MRM(HR) mode has allowed us to develop a highly specific dual-peptide targeted assay for the quantification of Rituximab, in human plasma. The linearity of the assay was established from 1.0 to 200 µg/ml for both light and heavy chain surrogate peptides, with accuracy and precision within 15%. CONCLUSION: LC-HRMS can be an effective tool for the quantification of monoclonal antibodies in regulated bioanalysis.

Minimizing the Contribution of Enterohepatic Recirculation to Clearance in Rat for the NCINI Class of Inhibitors of HIV.

A scaffold replacement approach was used to identifying the pyridine series of noncatalytic site integrase inhibitors. These molecules bind with higher affinity to a tetrameric form compared to a dimeric form of integrase. Optimization of the C6 and C4 positions revealed that viruses harboring T124 or A124 amino acid substitutions are highly susceptible to these inhibitors, but viruses having the N124 amino acid substitution are about 100-fold less susceptible. Compound 20 had EC50 values <10 nM against viruses having T124 or A124 substitutions in IN and >800 nM in viruses having N124 substitions. Compound 20 had an excellent in vitro ADME profile and demonstrated reduced contribution of biliary excretion to in vivo clearance compared to BI 224436, the lead compound from the quinoline series of NCINIs.

Human rhinovirus VPg uridylylation AlphaScreen for high-throughput screening.

As an obligate step for picornaviruses to replicate their genome, the small viral peptide VPg must first be specifically conjugated with uridine nucleotides at a conserved tyrosine hydroxyl group. The resulting VPg-pUpU serves as the primer for genome replication. The uridylylation reaction requires the coordinated activity of many components, including the viral polymerase, a conserved internal RNA stem loop structure, and additional viral proteins. Formation of this complex and the resulting conjugation reaction catalyzed by the polymerase, offers a number of biochemical targets for inhibition of an essential process in the viral life cycle. Therefore, an assay recapitulating uridylylation would provide multiple opportunities for discovering potential antiviral agents. Our goal was to identify inhibitors of human rhinovirus (HRV) VPg uridylylation, which might ultimately be useful to reduce or prevent HRV-induced lower airway immunologic inflammatory responses, a major cause of asthma and chronic obstructive pulmonary disease exacerbations. We have reconstituted the complex uridylylation reaction in an AlphaScreen suitable for high-throughput screening, in which a rabbit polyclonal antiserum specific for uridylylated VPg serves as a key reagent. Assay results were validated by quantitative mass spectrometric detection of uridylylation.

A high-throughput assay for HIV-1 integrase 3'-processing activity using time-resolved fluorescence.

HIV-1 integrase (HIV-1 IN), a well-validated antiviral drug target, catalyzes multistep reactions to incorporate viral DNA into the genome of the host cell; these include both a 3'-processing (3'P) reaction and a strand transfer reaction. These enzymatic activities can be measured in vitro with short DNA oligonucleotides that mimic a single viral LTR DNA end and purified IN. A highly sensitive and reproducible time-resolved fluorescence (TRF)-based assay for HIV-1 IN 3'P activity is now reported. This assay was optimized with respect to time and concentrations of metal ions, substrate and enzyme. The assay has now been used successfully to measure HIV-1 IN 3'P activity and has been shown to detect the anti-IN activity of several known 3'P inhibition compounds accurately. This assay, which is amenable to high-throughput screening, will be useful for identification of additional HIV-1 IN 3'P inhibitors.