Immunosuppressive Drug Optimization and Monitoring - Organ Transplantation Drugs

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

Monitoring

Therapeutic Drug Monitoring Recommendations for Organ Type
Drug

 

 Kidney (KDOGO, 2010) Liver (Lucey, AASLD/AST, 2013) Heart (Costanzo, ISHLT, 2010)

Cyclosporine (CYA)

Monitor using

  • 12-hr trough, or
  • 2 hrs post dose, or
  • Abbreviated AUC

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

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%
Immunosuppressive Drug Regimens for Organ Transplantsa
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)

  • 1 mo post transplant – 100-200 ng/mL
  • 2-3 mos post transplant – 75-150 ng/mL
  • 4-5 mos post transplant – 50-100 ng/mL
  • 6-12 mos post transplant – 25-50 ng/mL

Heart transplant

  • Up to 3 mos post transplant – 350-525 ng/mL
  • ≥4 months post transplant – 145-350 ng/mL

Liver transplant

  • 290-525 ng/mL

IL-2 antibodies

  • Daclizumab (Zenapax)
  • Basiliximab (Simulect)

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

  • 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

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)

  • 4-12 ng/mL

Liver transplant

  • 12-20 ng/mL (suggested range)

Everolimus

  • Kidney transplant (in combination with cyclosporine) – 3-8 ng/mL
  • Liver transplant (in combination with tacrolimus) – 3-8 ng/mL

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

  • 0-3 mos post transplant – 7.0-20.0 ng/mL
  • ≥3 mos post transplant – 5.0-15.0 ng/mL

Heart transplant

  • 0-3 mos post transplant – 10.0-20.0 ng/mL
  • ≥3 mos post transplant – 5.0-15.0 ng/mL

Liver transplant

  • 1-12 mos post transplant – 5-20 ng/mL

aTrade names are in parentheses

bImmunosuppressive regimen depends on organ transplanted

n/a, not available; NMSC, nonmelanoma skin cancers; TGF, transforming growth factor

ARUP Lab Tests

Optimize drug therapy and monitor patient adherence

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

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

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)

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

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

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

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

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

Monitor response to CD3 immunosuppressive therapy

Medical Experts

Contributor
Contributor

McMillin

Gwendolyn A. McMillin, PhD
Gwendolyn A. McMillin, PhD
Professor of Clinical Pathology, University of Utah
Scientific Director, Mass Spectrometry Platform; Medical Director, Clinical Toxicology and Pharmacogenomics, ARUP Laboratories
Contributor

References

Additional Resources

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