Organ transplantation is the strategy of choice for end-stage organ disease. Immunosuppressive therapies have allowed patients to extend the life of the organ but require careful monitoring to prevent toxicity and rejection. Therapeutic choice should be carefully considered based on the clinical setting, and blood levels should be carefully monitored for adequate dosing and toxicity. Important factors include the organ transplanted, time posttransplant, age and clinical status of the patient, metabolic pathways, liver and kidney function, and concomitant medications.
Diagnosis
Indications for Testing
- Immunosuppressant dose optimization
- Failure to respond to immunosuppressants
- Signs or symptoms consistent with inadequate immunosuppression
- Signs or symptoms of immunosuppressant toxicity
- Changes to concomitant medications
- Change in kidney function, liver function, or other conditions that affect drug concentrations
- Change to generic form of medication
Laboratory Testing
- Whole blood specimens are used for therapeutic drug monitoring (TDM) of immunosuppressive drugs due to drug accumulation in red blood cells (RBCs) (serum/plasma not acceptable), including
- Cyclosporine A
- Tacrolimus
- Everolimus
- Sirolimus
- Thiopurine
ARUP Test | Indications | Therapeutic Rangea/Toxic Level |
---|---|---|
Cyclosporine A by Tandem Mass Spectrometry 0070035 |
Optimize drug therapy and monitor patient adherence |
Therapeutic range – 100-400 ng/mL Kidney transplant (in combination with everolimus) Heart transplant Liver transplant – 290-525 ng/mL Toxic – >700 ng/mL |
Cyclosporine A, 2-Hour Post Dose (C2) by Tandem Mass Spectometry 0058902 |
Optimize drug therapy and monitor patient adherence |
Renal transplant (suggested target range) – 800-1700 ng/mL Liver transplant (suggested target range) – 600-1000 ng/mL |
Everolimus by Tandem Mass Spectrometry 0092118 |
Optimize drug therapy and monitor patient adherence |
Kidney transplant (in combination with cyclosporine) – 3-8 ng/mL Liver transplant (in combination with tacrolimus) – 3-8 ng/mL Toxic value – >15 ng/mL |
Leflunomide Metabolite, Serum or Plasma 2007460 |
Therapeutic monitoring and evaluating full elimination of the drug (eg, toxicity, pregnancy) |
Therapeutic range – >40.000 µg/mL |
Mycophenolic Acid and Metabolites 2010359 |
Optimize drug therapy and monitor patient adherence |
Mycophenolic acid Mycophenolic acid glucuronide Mycophenolic acid acyl-glucuronide |
Sirolimus by Tandem Mass Spectrometry 0098467 |
Optimize drug therapy and monitor patient adherence |
Therapeutic range Kidney transplant (in combination with cyclosporine) – 4-12 ng/mL Toxic – >25 ng/mL |
Tacrolimus by Tandem Mass Spectrometry 0090612 |
Optimize drug therapy and monitor patient adherence |
Therapeutic range Kidney transplant Heart transplant Liver transplant Toxic – >25 ng/mL |
Thiopurine Methyltransferase, RBC 0092066 |
Phenotype test to assess risk for severe myelosuppression with standard dosing of thiopurine drugs Use for individuals being considered for thiopurine therapy Must be performed before thiopurine therapy is initiated Can also detect rapid metabolizer phenotype. |
Normal TPMT activity – 24-44 U/mL Intermediate TPMT activity – 17-23.9 U/mL Low TPMT activity – <17 U/mL High TPMT activity – >44 U/mL Therapeutic drug management recommended |
aThe therapeutic range is based on serum predose (trough) draw at steady-state concentration TPMT, thiopurine methyltransferase |
Monitoring
Therapeutic drug monitoring is required for patients on therapy
Drug
|
Kidney (KDOGO, 2010) | Liver (Lucey, AASLD/AST, 2013) | Heart (Costanzo, ISHLT, 2010) |
---|---|---|---|
Cyclosporine (CYA) |
Monitor using
Measure blood levels every other day during immediate post operation until target reached, then with any change in patient status, kidney function, or medication |
n/a |
12-hr trough recommended over 2 hrs post dose |
Tacrolimus |
Monitor using 12-hr trough Measure blood levels every other day during immediate post operation until target reached, then with any change in patient status, kidney function, or medication |
n/a |
12-hr or 24-hr trough, depending on dosing schedule and type |
Sirolimus |
No recommendation provided |
n/a |
Measure trough concentration at least 5 days after dosage adjustment |
Everolimus |
Measure trough concentration at 4-5 days after initiation or dosage adjustment (van Gelder, 2017) |
Measure trough concentration at 4-5 days after initiation or dosage adjustment (van Gelder, 2017) |
Measure trough concentration at least 5 days (ISHLT, 2010) or 4-5 days (van Gelder, 2017) after initiation or dosage adjustment |
Mycophenolic acid |
Monitoring suggested (no schedule provided) |
Need for therapeutic monitoring unclear |
No recommendations for routine monitoring |
n/a, not available Sources: AASLD/AST, American Association for the Study of Liver Diseases and the American Society of Transplantation; AUC, area under the curve; ISHLT, International Society of Heart and Lung Transplantation; KDIGO, Kidney Disease: Improving Global Outcomes |
Kidney and liver function, other medications, anemia, and other changes in the patient’s condition may affect serum concentrations
Antimicrobials | Antifungals | Antiretroviral Therapy | Cardiovascular | Nutraceuticals | Others | |
---|---|---|---|---|---|---|
Increase Levels |
Clarithromycin Erythromycin Azithromycin Metronidazole and tinidazole Quinupristin/dalfopristin Levofloxacin Ofloxacin Ciprofloxacin |
Clotrimazole Itraconazole Ketoconazole Fluconazole Posaconazole Voriconazole |
Protease inhibitors (general) Amprenavir Atazanavir Darunavir Fosamprenavir Indinavir Nelfinavir Ritonavir Saquinavir Tipranavir |
Amiodarone Diltiazem Verapamil |
Bitter orange Grapefruit juice |
Rilonacept Theophylline Cimetidine Fluvoxamine Glipizide Glyburide Imatinib Nefazodone Ganciclovir Valganciclovir |
Antiepileptics | Antimicrobials | Antiretroviral Therapy | Others | |||
Decrease Levels |
Carbamazepine Fosphenytoin Phenobarbital Phenytoin |
Caspofungin Nafcillin Rifabutin Rifampin Rifapentine |
Efavirenz Etravirine Nevirapine |
Antacids containing magnesium, calcium, or aluminum (tacrolimus only) Deferasirox Modafinil St. John’s wort Thalidomide Ticlopidine Troglitazone |
||
Sources: Adapted from Costanzo, International Society of Heart and Lung Transplantation (ISHLT), 2010; Lucey, American Association for the Study of Liver Diseases and the American Society of Transplantation (AASLD/AST), 2013 |
Pharmacogenetics
- Thiopurine drugs
- Thiopurine prodrugs are metabolized via thiopurine methyltransferase (TPMT) and nudix hydrolase 15 (NUDT15) enzymatic activity
- Deficiency of TPMT and NUDT15 predicts hematopoietic toxicity after thiopurine treatment
- Testing to determine activity level may be helpful in dosing thiopurine drugs and averting bone marrow suppression
- A significant dose reduction may be needed in patients with TPMT and/or NUDT15 variants or patients with demonstrated TPMT enzyme activity deficiency
- Guidelines for thiopurine dosing are published
- Genotype for TPMT and/or NUDT15 cannot be inferred from TPMT activity (phenotype)
- TPMT phenotype testing does not replace need for clinical monitoring of patients treated with thiopurine drugs
- Phenotype testing should not be requested for patients currently treated with thiopurine drugs; results will be falsely low
- Current TPMT phenotype may not reflect future TPMT phenotype, particularly in patients who received blood transfusions within 30-60 days of testing
Background
Epidemiology
- Incidence – ~33,600 organ transplants in U.S. in 2016 (U.S. Department of Health and Human Services, 2017)
- Prevalence – >30,000 liver transplant 5-year survivors in the U.S. in 2011 (Lucey, 2013)
- Survival rate 1 year post graft – 90%
Available Immunosuppressivesb | Mechanism of Action | Toxicity | Therapeutic Ranges |
---|---|---|---|
Alemtuzumab (Campath-IH, Lemtrada) |
Lymphocyte-depleting antibody (targets CD52 on T cells, B cells, and NK cells, causing depletion) |
Increases risk of infection |
n/a |
Antithymocyte globulin (Atgam) |
Lymphocyte-depleting agent |
Increases risk of infection |
Aim for 0.1-0.3 lymphocytes/mL |
Azathioprine (Imuran, Azasan) 6-mercaptopurine (Puinethol, Purixan) |
Antiproliferative agent |
Increases risk of infection and malignancy (acute myeloid leukemia and myelodysplastic syndromes) |
n/a |
Belatacept (Nulojix) |
Binds to T cells to prevent CD28 signaling |
Increases risk of infection |
n/a |
Corticosteroids |
Proapoptotic effect on lymphoid cells; suppresses eicosanoid production; increases TGF expression |
Increases risk of infection and malignancy (NMSC) |
n/a |
Cyclosporine A (Sandimmune, Neoral, Gengraf) |
Calcineurin inhibitor |
Increases risk of malignancy, nephrotoxicity, cardiotoxicity, hyperlipidemia Toxic level – >700 ng/mL |
General therapeutic range – 100-400 ng/mL Kidney transplant (in combination with everolimus)
Heart transplant
Liver transplant
|
IL-2 antibodies
|
IL-2 receptor antagonist (selectively blocks IL-2 receptors on T-helper cells, preventing T-cell proliferation) |
Increases risk of malignancy (NMSC and lymphomas) |
n/a |
Muromonab-CD3 (Orthoclone OKT3) |
Lymphocyte-depleting agent |
Increases risk of infection |
500-1,500 ng/mL during steady-state treatment |
Mycophenolic acid (CellCept, Myfortic) |
Antiproliferative agent (selectively inhibits inosine monophosphate dehydrogenase – interferes with DNA purine synthesis) |
Increases risk of infection Toxic ranges are not well established, except for mycophenolic acid (>25 μg/mL) |
Suggested therapeutic range (for 2 g/day dosing) Mycophenolic acid – 1.0-3.5 μg/mL
Mycophenolic acid glucuronide – 35-100 μg/mL |
Rituximab (Rituxan, MabThera) |
B-cell-depleting agent (binds CD20 and B cells mediating lysis) |
Increases risk of infection |
n/a |
Sirolimus (Rapamune) Everolimus (Zortress, Afinitor) |
mTOR inhibitor |
Increases risk of hyperlipidemia and infection Sirolimus toxic level – >25 ng/mL Everolimus toxic level – >15 ng/mL |
Measured as trough level Sirolimus therapeutic ranges for kidney transplant (in combination with cyclosporine)
Liver transplant
Everolimus
|
Tacrolimus (Prograf, Hecoria, Envarsus XR, Astagraf XL) |
Calcineurin inhibitor |
Increases risk of malignancy, nephrotoxicity, cardiotoxicity, hyperlipidemia Toxic level – ≥25 ng/mL |
Measured as trough level Therapeutic ranges for kidney transplant
Heart transplant
Liver transplant
|
aTrade names are in parentheses bImmunosuppressive regimen depends on organ transplanted n/a, not available; NMSC, nonmelanoma skin cancers; TGF, transforming growth factor |
ARUP Laboratory Tests
Optimize drug therapy and monitor patient adherence
Quantitative Liquid Chromatography-Tandem Mass Spectrometry
Optimize drug therapy and monitor patient adherence
Results from different methodologies (mass spectrometry versus immunoassay) cannot be used interchangeably
Generally, immunoassay methods have been reported to have a positive bias in results when compared to mass spectrometry due to antibody cross-reactivity
Quantitative Liquid Chromatography-Tandem Mass Spectrometry
Optimize drug therapy and monitor patient adherence
Trough concentrations should be assessed ~2 weeks after beginning treatment
Interferences from commonly used drugs and associated metabolites have not been observed
Results from different methodologies (mass spectrometry versus immunoassay) cannot be used interchangeably
Generally, immunoassay methods have been reported to have a positive bias in results when compared to mass spectrometry due to antibody cross-reactivity
Quantitative Liquid Chromatography-Tandem Mass Spectrometry
Optimize drug therapy and monitor patient adherence
Predose (trough) concentration at steady state should be assessed
Toxic and therapeutic ranges are not well established for metabolites except for mycophenolic acid (>25 μg/mL)
Quantitative Liquid Chromatography-Tandem Mass Spectrometry
Optimize drug therapy and monitor patient adherence
Results from different methodologies (mass spectrometry versus immunoassay) cannot be used interchangeably
Generally, immunoassay methods have been reported to have a positive bias in results when compared to mass spectrometry due to antibody cross-reactivity
Quantitative High Performance Liquid Chromatography-Tandem Mass Spectrometry
Optimize drug therapy and monitor patient adherence
Results from different methodologies (mass spectrometry versus immunoassay) cannot be used interchangeably
Generally, immunoassay methods have been reported to have a positive bias in results when compared to mass spectrometry due to antibody cross-reactivity
Quantitative Liquid Chromatography-Tandem Mass Spectrometry
Phenotype test to assess risk for severe myelosuppression with standard dosing of thiopurine drugs
Testing should be performed prior to initiation of thiopurine therapy
For therapy optimization or toxicity evaluation, order thiopurine metabolites by LC-MS/MS
Does not replace clinical monitoring
Genotype cannot be inferred from thiopurine methyltransferase (TPMT) activity (phenotype)
TPMT inhibitors may contribute to falsely low test results
TPMT activity should be assessed prior to treatment with thiopurine drugs
Blood transfusion within 30 days may reflect donor status
Enzymatic/Quantitative Liquid Chromatography-Tandem Mass Spectrometry
Phenotype test used to optimize therapy for patients who are taking thiopurine drugs
Thiopurine metabolite concentrations are identified to assess therapeutic and toxic concentrations
If thiopurine therapy has not been initiated, order thiopurine methyltransferase, red blood cell
Quantitative Liquid Chromatography/Tandem Mass Spectrometry
Genotype test to assess risk, due to genetics, for severe myelosuppression with standard dosing of thiopurine drugs
Use for individuals being considered for thiopurine therapy or who have had an adverse reaction to thiopurine therapy
Preferred test for patients with recent heterologous blood transfusion
Can be performed irrespective of thiopurine therapy
Polymerase Chain Reaction/Fluorescence Monitoring
Monitor response to CD3 immunosuppressive therapy
Quantitative Flow Cytometry
Medical Experts
Johnson-Davis

McMillin

Wittwer

References
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Annotation of CPIC Guideline for mercaptopurine and NUDT15, TPMT
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