MASS SPECTROMETRY QUANTITATION OF P450 PROTEIN ISOFORMS IN HEPATOCYTES | Patent Publication Number 20150045256
US 20150045256 A1Subhasish Purkayastha
A method for screening a drug for cytochrome P450 (CYP) induction is provided and can include incubating the drug with a microsome-containing biological sample and then quantitating at least one cytochrome P450 isoform. The isoforms can be selected from 2B6, 3A4, 1A2, and 3A5 isoforms. In some embodiments, the method uses liquid chromatography tandem mass spectrometry (LC-MSMS). A quantitated value can be compared to a threshold value and the drug can be determined to exhibit an acceptable CYP induction potential when the quantitated value does not exceed the threshold value. Isolated peptides are also provided.
- 1. A method for determining an amount of at least one isoform of cytochrome P450 (CYP) in a sample, said method comprising subjecting said sample to an analysis with a liquid chromatograph tandem mass spectrometer system, said system comprising a triple quadrupole instrument and Multiple Reaction Monitoring (MRM), said analysis comprising detecting at least one isolated peptide of CYP 3A4, CYP 1A2 or CYP 3A5.
- 18. A method for screening a drug for cytochrome P450 (CYP) induction, comprising:nincubating the drug with a microsome-containing biological sample;determining a quantitated value of at least one of a CYP 3A4, CYP 1A2 or CYP 3A5 isoform in said drug incubated with the microsome-containing biological sample, said determining comprising,subjecting said drug incubated with the microsome-containing biological sample to an analysis with a liquid chromatography tandem mass spectrometer system, said system comprising a triple quadrupole instrument and multiple reaction monitoring, said analysis comprising detecting an isolated peptide of said isoform;comparing the quantitated value to a threshold value;determining that the drug has an acceptable CYP induction potential when the quantitated value does not exceed the threshold value.
The present application is a divisional of U.S. application Ser. No. 12/904,520, filed Oct. 13, 2010, which claims the benefit of priority from U.S. Provisional Patent Application Nos. 61/252,648, filed Oct. 17, 2009, and 61/252,430, filed Oct. 16, 2009, all of which are incorporated herein in their entireties by reference.
The present teachings relate to cytochrome P450 enzymes (CYPs) and detection of enzymes using mass spectrometry.
Cytochrome P450 enzymes (CYPs) are major drug metabolizing enzymes and experimental pharmaceutical compounds are generally evaluated for their CYP induction potential early in the development process. Measurement of a CYP induction profile in response to a chemical can be used as a fundamental aspect of drug safety evaluation, but expression of these proteins is regulated by transcriptional, post transcriptional and translational mechanisms. As a result, mRNA-based assays are not reliable predictors of CYP induction. Further, CYPs exhibit extensive amino acid sequence homology, particularly within subfamilies, so that P450 protein expression methods are also poorly discriminatory.
According to various embodiments of the present teachings, a method of quantitating the 1A2, 2B6, 3A4, and 3A5 isoforms of cytochrome P450 enzymes (CYPs) is provided without the need for any chemical labeling. Isoform-specific tryptic peptides can be observed in liquid chromatography-Tandem Mass Spectrometry (LC-MSMS) analysis of samples derived from hepatocytes, for example, in microsomes, along with their optimal Q1 and Q3 transitions. Those observed peptides and transitions, can be used to enable a reliable CYP quantitation of the isoforms 1A2, 2B6, 3A4, and 3A5.
According to various embodiments, a set of peptides and optimal MRM transistors are provided as “house keeping†microsomol proteins whose concentrations are unaffected by drug incubation. The set can be used as normalization proteins for quantitative analysis. In some embodiments, quantitation can be performed by spiking into the sample heavy forms of the isoform-specific peptides, for example, forms that have been enriched with C13 and/or N15.
The present teachings will be described with reference to the accompanying drawings. The drawings are intended to illustrate, not limit, the present teachings.
According to various embodiments, a method for screening a drug for cytochrome P450 (CYP) induction is provided that comprises incubating the drug with a microsome-containing biological sample and quantitating at least one CYP isoform. In some embodiments, the isoforms con comprise one or more isoform selected front 2B6, 3A4, 1A2, and 3A5 isoforms. The method can comprise using a liquid chromatography tandem mass spectrometry (LC-MSMS) technique to quantitate the amount of each isoform. The quantitated value of each can be compared to a threshold value, and the drug can be identified as having an acceptable CYP induction potential when the quantitated value does not exceed the threshold value. The threshold value can be selected or predetermined based on a desired CYP induction potential or based on the CYP induction potential of one or more different drugs, similar or non-similar to the drug being screened. In some embodiments, the microsome-containing biological sample can be derived from a mammal, from a primate, or from a human.
According to various embodiments, the drug can be incubated with a sample containing human hepatocytes. In some embodiments, after incubation with the drag, the sample containing human hepatocytes can be used to obtain at least one microsome fraction by, for example, 16 G centrifugation. The microsome fraction can be analyzed for CYP induction by the drug, by detecting isolated peptides specific to CYP (isoform-specific peptides). According to some embodiments, after incubation with the drug, the sample containing human hepatocytes can be used to obtain at least one S9 fraction by, for example, 9 G centrifugation. The S9 fraction can be analyzed to detect CYP induction by the drug, for example, by detecting isolated peptides specific to CYP (isoform-specific peptides). According to some embodiments, the microsome fraction or the S9 faction can be analyzed using a liquid chromatography tandem mass spectrometry (LC-MSMS) technique in order to quantitate at least one CYP isoform. The quantitated value of each can be compared to a threshold value, and the drug can be identified as having an acceptable CYP induction potential when the quantitated value does not exceed the threshold value.
According to various embodiments, a method is provided for directly analyzing CYP from hepatocytes. In some embodiments, antibody peptides can be used to pull the isoform-specific peptides directly out of hepatocyctes. According to some embodiments, using antibody peptides to pull the isoform-specific peptides directly out of hepatocytes would have the advantage of not needing to prepare S9 or microsome fractions, and would require less hepatocyte cells for drug incubation.
In some embodiments, the method comprises comparing detected induction to a control. For example, became little or no drug induction of CYPs is desirable, a threshold can be set such that the drug mug show less than (<) 40% induction compared to the positive control, to be considered acceptable. In some embodiments, the drug must show less than (<) 30% induction compared to the positive control, to be considered acceptable. In other embodiments, the drug mast show less than (<) 20% induction compared to the positive control, to be considered acceptable.
According to various embodiments, a method for determining an amount of at least one isoform of cytochrome P450 (CYP) in a sample, is provided. The method can comprise the use of a mass spectrometry technique, wherein the at least one isoform of cytochrome P450 comprises at least one of CYP 2B6, CYP 3A4, CYP 1A2, and CYP 3A5. The mass spectrometry technique can comprise a tandem mass spectrometry (MS/MS) technique and/or a liquid chromatography tandem mass spectrometry (LC-MS/MS) technique. In some embodiments, the technique comprises an LC-MS/MS technique and the use of a triple quadrupole instrument and Multiple Reaction Monitoring (MRM).
The isolated peptides comprising the amino acid sequence of SEQ ID NOs: 15, 15, or 17 identified in Table 4 below are specific to CYP 3A5.
According to various embodiments, the method can comprise determining an amount or CYP 2B6 in the sample by detecting an isolated peptide specific to cytochrome P450 (CYP) isoform CYP 2B6, for example, one or more of the isoforms comprising the amino acid sequence of SEQ ID NO: 1, SEQ ID NO: 2, or SEQ ID NO: 3 identified herein. The amount can be determined using a triple quadrupole instrument and Multiple Reaction Monitoring (MRM). In some embodiments, the isolated peptide can comprise the amino acid sequence of SEQ ID NO: 1 identified herein, and the method can comprise monitoring precursor-product ion pair transitions having an m/z value of about 548/911, 548/681, or 548/566, wherein the term “about†as used herein means within a range of +/− one (1) atomic mass unit. In some embodiments, the isolated peptide can comprise the amino acid sequence of SEQ ID NO: 2 identified herein, and the method can comprise monitoring precursor-product ion pair transitions having an m/z value of about 494/777, 494/437, or 494/874. In some embodiments, the isolated peptide can comprise the amino acid sequence of SEQ ID NO: 3 identified herein, and the method can comprise monitoring precursor-product ion pair transitions having an m/z value of about 421/508, 421/607, or 421/694. In some embodiments, the isolated peptide can comprise the amino acid sequence of SEQ ID NO: 4, and the method can comprise monitoring precursor-product ion pair transitions having an m/z value of about 479/499, 479/614, or 479/727.
According to various embodiments, the method can comprise determining an amount of CYP 3A4 in the sample by detecting an isolated peptide specific to cytochrome P450 (CYP) isoform CYP 3A4, comprising the amino acid sequence of SEQ ID NO: 5, SEQ ID NO: 6, or SEQ ID NO: 7 identified herein. The method can use, for example, a triple quadrupole instrument and Multiple Reaction Monitoring (MRM). In some embodiments, the isolated peptide can comprise the amine acid sequence of SEQ ID NO: 5 identified herein, and the method can comprise monitoring precursor-product ion pair transitions having an m/z value of about 440/549, 440/650, or 440/532. In some embodiments, the isolated peptide can comprise the amino acid sequence of SEQ ID NO: 6 identified herein, and the method can comprise monitoring precursor-product ion pair transitions having an m/z value of about 704/794, 704/929, 564/639, 564/745, or 564/790. In some embodiments, the isolated peptide can comprise the amino acid sequence of SEQ ID NO: 7 identified herein, and the method can comprise monitoring precursor-product ion per transitions having an m/z value or about 798/819, 798/932, or 798/1004.
According to various embodiments, the method can comprise determining en amount of CYP 1A2 in the sample by detecting an isolated peptide specific to cytochrome P450 (CYP) isobar CYP 1A2, comprising the amino acid sequence of SEQ ID NO: 8, SEQ ID NO: 9, SEQ ID NO: 10, SEQ ID NO: 11, SEQ ID NO: 12, SEQ ID NO: 13, or SEQ ID NO: 14, identified herein. The method can use, for example, a triple quadrupole instrument and Multiple Reaction Monitoring (MRM).
In some embodiments, the isolated peptide can comprise the amino acid sequence of SEQ ID NO: 8 identified herein, and the method can comprise monitoring precursor-product ion pair transitions having an m/z value of about 432/636, 432/535, or 432/478. In some embodiments, the isolated peptide can comprise the amino acid sequence of SEQ ID NO: 9 identified herein, and the method can comprise monitoring precursor-product ion pair transitions having an m/z value of about 482/800, 482/628, or 482/743. In some embodiments, the isolated peptide can comprise the amino acid sequence of SEQ ID NO: 10 identified herein, and the method can comprise monitoring precursor-product ion pair transitions having an m/z value of about 491/721, 491/834, or 491/535. In some embodiments, the isolated peptide can comprise the amino acid sequence of SEQ ID NO: 11 identified herein, and the method can comprise monitoring precursor-product ion pair transitions having an m/z value of about 528/501, 528/614, or 528/727. In some embodiments, the isolated peptide can comprise the amino acid sequence of SEQ ID NO: 12 identified herein, and the method can comprise monitoring precursor-product ion pair transitions having an m/z value of about 571/783, 571/971, 571/1028, 381/587, 381/474, or 381/375. In some embodiments, the isolated peptide can comprise the amino acid sequence of SEQ ID NO: 13 identified herein, and the method can comprise monitoring precursor-product ion pair transitions having an m/z value of about 695/695, 695/837, or 695/950. In some embodiments, the isolated peptide can comprise the isolated peptide comprises the amino acid sequence of SEQ ID NO: 14 identified herein, and the method can comprise monitoring precursor-product ion pair transitions having an m/z value of about 536/795, 536/584, or 536/698.
According to various embodiment the method can comprise determining an amount of CYP 3A5 in the sample by detecting an isolated peptide specific to cytochrome P450 (CYP) isoform CYP 3A5, comprising the amino acid sequence of SEQ ID NO: 15, SEQ ID NO: 16, or SEQ ID NO: 17 identified herein. The method can use, for example, a triple quadrupole instrument and Multiple Reaction Monitoring (MRM). In some embodiments, the isolated peptide can comprise an amino acid sequence of SEQ ID NO: 15 identified herein, and the method can comprise monitoring precursor-product ion pair transitions having an m/z value of about 468/581, 468/679, or 468/736. In some embodiments, the isolated peptide can comprise on amino acid sequence of SEQ ID NO: 16 identified herein, and the method can comprise monitoring precursor-product ion pair transitions having an m/z value of about 470/494, 470/608, or 470/722. In some embodiments, the isolated peptide can comprise an amino acid sequence of SEQ ID NO: 17 identified herein, and the method can comprise monitoring precursor-product ion pair transitions having an m/z value of about 589/747, 589/696, or 589/647.
According to various embodiments of the present teachings, a kit is provided that can comprise one or more of the isolated peptides specific to one or more of cytochrome P450 (CYP) isoform CYP 2B6, CYP 3A4, CYP 1A2, and CYP 3A5. For example, the kit can comprise one or more isolated proteins specific to CYP 2B6, comprising the amino acid sequence of SEQ ID NO: 1, SEQ ID NO: 2, SEQ ID NO: 3, or SEQ ID NO: 4. The kit can comprise one or more isolated proteins specific to CYP isoform CYP 3A4, comprising the amino acid sequence of SEQ ID NO: 5, SEQ ID NO: 6, or SEQ ID NO: 7. The kit can comprise one or more isolated proteins specific to CYP isoform CYP 1A2, comprising the amino acid sequence of SEQ ID NO: 8, SEQ ID NO: 9, SEQ ID NO: 10, SEQ ID NO: 11, SEQ ID NO: 12, SEQ ID NO: 13, or SEQ ID NO: 14. The kit can comprise one or more isolated proteins specific to CYP isoform CYP 3A5, comprising the amino acid sequence of SEQ ID NO: 15, SEQ ID NO 16, or SEQ ID NO: 17.
In some embodiments, the kit can comprise at least one isolated peptide specific to each of CYP isoforms CYP 2B6, CYP 3A4, CYP 1A2, and CYP 3A5. For example, the kit can comprise each of the isolated peptides of SEQ ID NOS: 1-17 identified herein, and further can comprise instructions for measuring Q1 and Q3 transition values for each of the isoform-specific peptides. The kit can comprise enzyme digestion components including buffers and enzymes, other buffers, and optionally other reagents and/or components. In some embodiments, the kit can comprise, for example, a homogeneous assay such that the user need only add a sample. In some embodiments, the kit can comprise calibration or normalization reagents or standards. Information pertaining to instrument settings that can or should be used to perform an assay can also be included in the kit. Information pertaining to sample preparation, operating conditions, volumetric amounts, temperature settings, and the like, can be included with the kit.
According to various embodiments, different transitions can be used to measure and benchmark assay results, depending on various factors. Accordingly, the kit can comprise different transition values and/or suggested settings, useful to make comparative measurements between a sample and one or more control reagents. The kit can include instructions to measure specific pairs of transition values, for example, the Q1/Q3 transition pair, or the values of one or more different transition pairs.
The kit can be packaged in a hermetically sealed container containing one or more regent vessels and appropriate instructions. An electronic medium can be included in the kit, having stored thereon electronic information pertaining to one or more assays, measurement values, transition pairs, operating instructions, software for carrying out operations, a combination thereof, or the like.
The present teachings can be even more fully understood with reference to the examples and resulting data that follow. In the examples below and the results shown in the attached drawing figures, a CYP induction study was undertaken as follows.
Primary cultures of humus hepatocytes were treated for 72 hours with the prototypical liver enzyme inducers 3-methylcholanthrene (3-MC, 2 μM), phenobarbital (PB, 1 mM), or rifampicin (RIF, 10 μM) to enhance the expression and activity of CYP1A2, CYP2B6, and CYP3A4, respectively. The CYP quantitation method of the present teachings was used to determine the amount of CYP in the sample after treatment with the liver enzyme inducers. In addition, CYP activity was measured by metabolite formation from selective substrates (phenacetin, bupropion and testosterone, respectively) and mRNA was measured by qRT-PCR (Taqman®, Applied Biosystems).
Microsomal subcellular fractions were prepared by lysing treated hepatocytes in homogenization buffer (50 mM TRIS-HCl, pH 7.0, 150 mM KCl, 2 mM EDTA) followed by centrifugation at 9,000×g for 20 minutes at 4° C. The supernatant (S9 fraction) was then spun at 100,000×g for 60 minutes at 4° C. The resulting microsomal pellet was resuspended in 0.25 M sucrose and stored at −80° C. until analysis.
To 100 ul of each microsomal preparation, 5 ul 2% SDS was added, followed by 10 ul of 50 mM TCEP and incubated at 60° C. for 1 hr, 5 ul of 0.1M MMTS was added and incubated at room temperature for 10 minutes. 100 ul of 100 mM TRIS (pH=8.50) was then added followed by 50 ug of trypsin and the resultant solution was digested overnight at 37° C. On (1) ng of each isotopically enriched synthetic peptide was added to the digest and analyzed by LC-MS.
Chromatography was performed using an Agilent 1100 system (Agilent of Santa Clara, Calif.) coupled to a C18 Jupiter Proteo 50×2.0 mm column (Phenomenex of Torrance, Calif.). The gradient was 5-40% B over 15 minutes with A consisting of 2% ACN, 0.1% formic and B consisting of 90% ACN, 10% H2O, 0.1% formic acid. Flow rate was 700 μL/min.
Samples were analyzed on a Applied Biosystems MDS SCIEX 4000 QTRAPâ„¢ LC/MS/MS system, using a Turbo Vâ„¢ source and Analyst 1.5. For quantitation, scheduled MRM (sMRM) was used to maximize dwelt time on each transition.
Quantitative data was processed using MultiQuartâ„¢ 1.2 software available from Applied Biosystems, LLC of Foster City, Calif.
Table 1 below shows sequences of the peptides determined, according to the present teachings, to be specific to cytochrome P450 (CYP) isoform CYP 2B6, along with their optimal MRM Q1, Q3 transitions. According to various embodiments, these observed peptides and transitions can be used to enable a reliable CYP quantitation of the isoform CYP 2B6.
Table 2 below shows sequences of the peptides determined, according to the present teachings, to be specific to cytochrome P450 (CYP) isoform CYP 3A4, along with their optimal MRM Q1, Q3 transitions. According to various embodiments, these observed peptides and transitions can be used to enable a reliable CYP quantitation of the isoform CYP 3A4.
Table 3 below snows sequences of the peptides determined, according to the present teachings, to be specific to cytochrome P450 (CYP) isoform CYP 1A2, along with their optimal MRM Q1, Q3 transitions. According to various embodiments, these observed peptides and transitions can be used to enable a reliable CYP quantitation of the isoform CYP 1A2.
Table 4 below shows sequences of the peptides determined, according to the present teachings, to be specific to cytochrome P450 (CYP) isoform CYP 3A5, along with their optimal MRM Q1, Q3 transitions. According to various embodiments, these observed peptides and transitions can be used to enable a reliable CYP quantitation of the isoform CYP 3A5.
Table 5 below shows sequences of the peptides along with their optimal MRM Q1, Q3 transitions for the house-keeping microsomal protein Microsomal GST. According to various embodiments, the concentration of this observed peptide is unaffected by drug incubation and thus the peptide can be useful as a normalization protein to enable reliable CYP quantitation.
Table 6 below shows sequences of the peptides along with their optimal MRM Q1, Q3 transitions for the house-keeping microsomal protein Microsomal Triglyceride. According to various embodiments, the concentration of this observed peptide is unaffected by drug incubation and thus the peptide can be useful as a normalization protein to enable reliable CYP quantitation.
Table 7 below shows sequences of the peptides along with their optimal MRM Q1, Q3 transitions for the house-keeping microsomal protein Corticosteroid 11 beta. It should be understood that the Q1 and Q3 masses for the peptide of SEQ ID NO: 22 in Table 7 refers to the MMTS alkylated peptide and that changing to a different alkylating reagent will change the Q1, Q3 masses. In addition, alkylating reagents other than MMTS can be used. According to various embodiments, the concentration of this observed peptide is unaffected by drug incubation and thus the peptide can be useful as a normalization protein to enable reliable CYP quantitation.
The observed isoform-specific tryptic peptides that are detected using LC-MSMS analysis of microsomes, along with their optimal Q1, Q3 transitions, enable a method for CYP quantitation of the isoforms 1A2, 2B6, 3A4, and 3A5 without the need for any chemical labeling approaches.
Other embodiments of the present teachings will be apparent to the skilled in the art from consideration of the present specification and practice of the present teachings disclosed herein. It is intended that the present specification and examples be considered as exemplary only.