Organ Transplantation - Immunosuppressive Drugs

  • Diagnosis
  • Monitoring
  • Pharmacogenetics
  • Background
  • Lab Tests
  • References
  • Related Topics

Indications for Testing

  • Immunosuppressant dose optimization
  • Failure to respond to immunosuppressants
  • Signs or symptoms consistent with inadequate or excessive immunosuppression
  • Changes to concomitant medications or other variables that affect pharmacokinetics
  • Therapeutic drug monitoring is required for patients on therapy
  • Thiopurine drugs
    • Thiopurine prodrugs are metabolized via thiopurine methyltransferase (TPMT) enzymatic activity
    • Deficiency of TPMT predicts hematopoietic toxicity after thiopurine treatment
    • Testing to determine activity level may be helpful in dosing thiopurine drugs and help avert bone marrow suppression
      • For deficient activity, dose reduction of 80-90% may be required
      • For intermediate activity, dose reduction of 20-50% may be required
    • Genotype for TPMT 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

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 ranges and toxic thresholds should be carefully considered based on the clinical setting. Important factors include the organ transplanted, time posttransplant, age and clinical status of the patient, and concomitant medications.

Epidemiology

  • Prevalence – in 2005, >60,000 patients in the U.S. were living with functioning organ transplants
  • Survival rate 1 year post graft – 90%
Immunosuppressive Drug Regimens for Organ Transplants*

Available Immunosuppressives (immunosuppressive regimen depends on organ transplanted)

Mechanism of Action

Toxicity

Therapeutic Ranges (if known)

Alemtuzumab (Campath-IH, Lemtrada)

Targets CD52 on T-cells, B-cells, and NK-cells, causing depletion

Increases risk of infection

 

Antithymocyte globulin (Atgam)

Depletes lymphocytes

Increases risk of infection

Aim for 0.1-0.3 lymphocytes/mL

Azathioprine (Imuran, Azasan)

6-mercaptopurine (Puinethol, Purixan)

Inhibits purine nucleotide synthesis, which interferes with DNA synthesis

Increases risk of infection and malignancy (acute myeloid leukemia and myelodysplastic syndromes)

 

Belatacept (Nulojix)

Binds to T-cells to prevent CD28 signaling

Increases risk of infection

 

Corticosteroids

Proapoptotic effect on lymphoid cells; suppresses eicosanoid production; increases TGF expression

Increases risk of infection and malignancy (nonmelanoma skin cancers [NMSC])

 

Cyclosporine A (Sandimmune, Neoral, Gengraf)

Inhibits calcineurin phosphatase and reduces IL-2 expression

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)

  • 1 month posttransplant – 100-200 ng/mL
  • 2-3 months posttransplant – 75-150 ng/mL
  • 4-5 months posttransplant – 50-100 ng/mL
  • 6-12 months posttransplant – 25-50 ng/mL

Heart transplant

  • Up to 3 months posttransplant – 350-525 ng/mL
  • ≥4 months posttransplant – 145-350 ng/mL

Liver transplant

  • 290-525 ng/mL

IL-2 antibodies

  • Daclizumab (Zenapax)
  • Basiliximab (Simulect)

Selectively blocks IL-2 receptors on T helper cells, preventing T-cell proliferation

Increases risk of malignancy (NMSC and lymphomas)

 

Muromonab-CD3 (Orthoclone OKT3)

Depletes lymphocyte T-cells

Increases risk of infection

500-1,500 ng/mL during steady state treatment

Mycophenolic acid (CellCept, Myfortic)

Selectively inhibits inosine monophosphate dehydrogenase – interferes with DNA purine synthesis

Increases risk of infection

Toxic ranges are not well established, except for mycophenolic acid

Mycophenolic acid – >25 μg/mL

Suggested therapeutic range (for 2 g/day dosing

Mycophenolic acid – 1.0-3.5 μg/mL

  • 3 g/day dose may have up to 5.0 μg/mL concentration
  • 2-4 μg/mL range is suggested for maximal efficacy with minimal toxicity

Mycophenolic acid glucuronide – 35-100 μg/mL

Mycophenolic acid acyl-glucuronide – not well established

Rituximab (Rituxan, MabThera)

Binds CD20 and B-cells mediating lysis

Increases risk of infection

 

Sirolimus (Rapamune)

 

Everolimus (Zortress, Afinitor)

Blocks B- and T-cell proliferation by blocking pathway between IL-2 receptor and nucleus; does not block calcineurin pathway; synergistic with cyclosporine

Increases risk of hyperlipidemia and infection

Measured as trough level

Sirolimus therapeutic ranges for kidney transplant (in combination with cyclosporine)

  • 4-12 ng/mL

Liver transplant

  • 12-20 ng/mL (suggested range)

Everolimus

  • 3-8 ng/mL

Tacrolimus (Prograf, Hecoria, Envarsus XR, Astagraf XL)

Inhibits calcineurin phosphatase and reduces IL-2 expression

Increases risk of malignancy, nephrotoxicity, cardiotoxicity, hyperlipidemia

Toxic level – ≥25 ng/mL

Measured as trough level

Therapeutic ranges for kidney transplant

  • 0-3 months posttransplant – 7.0-20.0 ng/mL
  • ≥3 months posttransplant – 5.0-15.0 ng/mL

Heart transplant

  • 0-3 months posttransplant – 10.0-20.0 ng/mL
  • ≥3 months posttransplant – 5.0-15.0 ng/mL

Liver transplant

  • 1-12 months posttransplant – 5-20 ng/mL

*Trade names are in parentheses

Tests generally appear in the order most useful for common clinical situations. Click on number for test-specific information in the ARUP Laboratory Test Directory.

Cyclosporine A by Tandem Mass Spectrometry 0070035
Method: Quantitative Liquid Chromatography-Tandem Mass Spectrometry

Limitations 

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

Cyclosporine A, 2-Hour Post Dose (C2) by Tandem Mass Spectrometry 0058902
Method: Quantitative Liquid Chromatography-Tandem Mass Spectrometry

Everolimus by Tandem Mass Spectrometry 0092118
Method: Quantitative Liquid Chromatography-Tandem Mass Spectrometry

Limitations 

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

Mycophenolic Acid and Metabolites 2010359
Method: Quantitative Liquid Chromatography-Tandem Mass Spectrometry

Limitations 

Toxic and therapeutic ranges are not well established for metabolites except for mycophenolic acid (>25 μg/mL)

Sirolimus by Tandem Mass Spectrometry 0098467
Method: Quantitative High Performance Liquid Chromatography-Tandem Mass Spectrometry

Limitations 

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

Tacrolimus by Tandem Mass Spectrometry 0090612
Method: Quantitative Liquid Chromatography-Tandem Mass Spectrometry

Limitations 

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

Thiopurine Methyltransferase, RBC 0092066
Method: Enzymatic/Quantitative Liquid Chromatography-Tandem Mass Spectrometry

Limitations 

Does not replace clinical monitoring

Genotype cannot be inferred from TPMT activity (phenotype)

TPMT inhibitors may contribute to false-low test results

TPMT activity should be assessed prior to treatment with thiopurine drugs

Blood transfusion within 30 days will reflect donor status

Thiopurine Drug Metabolites 2011134
Method: Quantitative Liquid Chromatography/Tandem Mass Spectrometry

Limitations 

Limit of quantification (LOQ)

  • LOQ – 12.5 pmol/8 x 108 RBC (6-TGN)
  • LOQ – 325 pmol/8 x 108 RBC (6-methyl mercaptopurine nucleotide [6-MMPN])

Does not replace clinical monitoring

TPMT inhibitors may contribute to false-low test results

TPMT activity should be assessed prior to treatment with thiopurine drugs

TPMT testing – blood transfusion within 30 days will reflect donor status

Thiopurine Methyltransferase (TPMT) Genotyping, 4 Variants 2012233
Method: Polymerase Chain Reaction/Fluorescence Monitoring

Limitations 

Only targeted TPMT allele variants will be detected by this panel

Diagnostic errors can occur due to rare sequence variations

Genotyping in patients who have received allogenic stem cell/bone marrow transplant will reflect donor status

Genotyping cannot distinguish the *1/*3A genotype from the *3B/*3C genotype

Thiopurine drug metabolism and risk for toxicity may be affected by genetic and nongenetic factors that are not evaluated by this test

Test does not assess for TPMT allele variants associated with ultra-high enzyme activity

Genotyping does not replace the need for therapeutic drug monitoring or clinical observation

Lymphocyte Transplantation CD3 0095949
Method: Quantitative Flow Cytometry

Follow-up 

For testing of immunocompromised patients, order Lymphocyte Subset Panel 4 – T-Cell Subsets Percent and Absolute 

Lymphocyte Transplantation Profile 0095798
Method: Quantitative Flow Cytometry

General References

Chadban S, Morris R, Hirsch HH, Bunnapradist S, Arns W, Budde K. Immunosuppression in renal transplantation: some aspects for the modern era. Transplant Rev (Orlando). 2008; 22(4): 241-51. PubMed

Geissler EK, Schlitt HJ. Immunosuppression for liver transplantation. Gut. 2009; 58(3): 452-63. PubMed

Rhee J, Al-Mana N, Freeman R. Immunosuppression in high-risk transplantation. Curr Opin Organ Transplant. 2009; 14(6): 636-42. PubMed

Rosen HR. Transplantation immunology: what the clinician needs to know for immunotherapy. Gastroenterology. 2008; 134(6): 1789-801. PubMed

Schonder KS, Mazariegos GV, Weber RJ. Adverse effects of immunosuppression in pediatric solid organ transplantation. Paediatr Drugs. 2010; 12(1): 35-49. PubMed

Srinivas TR, Meier-Kriesche H, Kaplan B. Pharmacokinetic principles of immunosuppressive drugs. Am J Transplant. 2005; 5(2): 207-17. PubMed

Urschel S, Altamirano-Diaz LA, West LJ. Immunosuppression armamentarium in 2010: mechanistic and clinical considerations. Pediatr Clin North Am. 2010; 57(2): 433-57, table of contents. PubMed

References from the ARUP Institute for Clinical and Experimental Pathology®

De BK, Jimenez E, De S, Sawyer JC, McMillin GA. Analytical performance characteristics of the Abbott Architect i2000 Tacrolimus assay; comparisons with liquid chromatography-tandem mass spectrometry (LC-MS/MS) and Abbott IMx methods. Clin Chim Acta. 2009; 410(1-2): 25-30. PubMed

Delgado JC, Fuller A, Ozawa M, Smith L, Terasaki PI, Shihab FS, Eckels DD. No occurrence of de novo HLA antibodies in patients with early corticosteroid withdrawal in a 5-year prospective randomized study. Transplantation. 2009; 87(4): 546-8. PubMed

Gross TG, Orjuela MA, Perkins SL, Park JR, Lynch JC, Cairo MS, Smith LM, Hayashi RJ. Low-dose chemotherapy and rituximab for posttransplant lymphoproliferative disease (PTLD): a Children's Oncology Group Report. Am J Transplant. 2012; 12(11): 3069-75. PubMed

Hasserjian RP, Chen S, Perkins SL, de Leval L, Kinney MC, Barry TS, Said J, Lim MS, Finn WG, Medeiros J, Harris NL, O'Malley DP. Immunomodulator agent-related lymphoproliferative disorders. Mod Pathol. 2009; 22(12): 1532-40. PubMed

Johnson-Davis KL, Juenke JM, Thomas RL, Bradshaw T. Everolimus method comparison between Waters MassTrak™ Immunosuppressants XE (IUO) kit and an in-house laboratory developed LC-MS/MS method in renal transplant patients Ann Clin Lab Sci. 2015; 45(1): 27-31. PubMed

Lundell R, Elenitoba-Johnson KS J, Lim MS. T-cell posttransplant lymphoproliferative disorder occurring in a pediatric solid-organ transplant patient. Am J Surg Pathol. 2004; 28(7): 967-73. PubMed

McMillin GA, Johnson-Davis K, Dasgupta A. Analytical performance of a new liquid chromatography/tandem mass spectrometric method for determination of everolimus concentrations in whole blood. Ther Drug Monit. 2012; 34(2): 222-6. PubMed

Schniedewind B, Niederlechner S, Galinkin JL, Johnson-Davis KL, Christians U, Meyer EJ. Long-term cross-validation of everolimus therapeutic drug monitoring assays: the Zortracker study Ther Drug Monit. 2015; 37(3): 296-303. PubMed

Scott JR, Courter JD, Saldaña SN, Widemann BC, Fisher M, Weiss B, Perentesis J, Vinks AA. Population pharmacokinetics of sirolimus in pediatric patients with neurofibromatosis type 1. Ther Drug Monit. 2013; 35(3): 332-7. PubMed

Medical Reviewers

Last Update: August 2016