Treatment of Ganciclovir-Resistant Cytomegalovirus in Adult Solid Organ Transplant Recipients

Caught Between a Rock and a Hard Place?

Emily Gordon, Pharm.D.

PGY-1 Pharmacy Resident Department of Pharmacy, University Health System, San Antonio, Texas

Division of Pharmacotherapy, The University of Texas at Austin College of Pharmacy Pharmacotherapy Education and Research Center,

University of Texas Health Science Center at San Antonio

November 1, 2013

Learning Objectives:

1. Describe the impact of cytomegalovirus infection and disease following solid organ transplantation and the current practice methods for prophylaxis and treatment.

2. Define the mechanisms and risk factors associated with the development of antiviral-resistant cytomegalovirus.

3. Explain when antiviral resistance should be suspected in the clinical setting and what diagnostic tests can be used for confirmation.

4. Evaluate the treatment options for ganciclovir-resistant cytomegalovirus infection and disease.

2

Cytomegalovirus

I. Epidemiology1-7

a. Cytomegalovirus (CMV) is a member of the human herpesviruses

i. Transmitted from infected individuals to others through direct contact with bodily fluids b. Evidence of prior exposure to CMV is present in about two-thirds of the United States population

i. Immunocompetent individuals

Figure 1. Stages of initial CMV infection in immunocompetent host8

ii. Solid organ transplant (SOT) recipients 1. CMV is the most common infection leading to major complications after

transplantation a. Rate is highly variable on type of transplantation, presence of associated risk

factors, and the use of prolonged prophylaxis 2. CMV is a major cause of morbidity and mortality

a. Increased incidence of rejection and crude mortality among SOT recipients who have CMV disease compared to those who do not

3. Growing rates of CMV antiviral resistance becoming an increased concern a. Association with poor clinical outcomes b. Lack of alternate antiviral treatment options

II. Definitions1,3,5,9

a. CMV infection

i. Evidence of CMV replication regardless of symptoms b. CMV disease (see Table 1)

i. Evidence of CMV infection with attributable symptoms 1. CMV syndrome 2. Tissue invasive disease

a. Most severe form of CMV disease b. Transplanted allograft is commonly involved c. Biopsy required for diagnosis

c. Latent CMV i. Virus exists as closed circular DNA

ii. Virus reactivation induced by many factors present in the transplant recipient 1. Therapy with antilymphocyte antibodies and cytotoxic drugs 2. Allogeneic reactions 3. Systemic infection and inflammation

Primary Infection

• First time patient is infected with the virus

• Asymptomatic or non-specific viral illness

• Easily overcome by the host immune system

Life-long Latency

• Established in individuals following primary infection

• Latency of virus maintained primarily via cell-mediated immunity

• Reservoirs for reactivation and spread of infection when immune system impaired

3

III. Manifestations1,4,6

(see Table 1) a. Direct effects

i. Caused by viral infection itself b. Indirect effects

i. Viral infection results in modification of the host immune system

1. Immunosuppressive, immunomodulatory, and inflammatory changes

2. Cytokine and growth factor response to viral replication

Table 1. Direct and Indirect Effects of Cytomegalovirus Infection1,4

Direct Effects Indirect Effects

CMV Syndrome

Fever

Malaise

Weakness

Myalgias/arthralgias

Leukopenia

Thrombocytopenia

Tissue Invasive Disease

Colitis

Pneumonitis

Hepatitis

Nephritis

Gastroenteritis

Retinitis

Acute rejection

Chronic rejection

Bacterial, viral, fungal infections

Mortality

Assessing the Transplant Patient

I. Pretransplant assessment1,2,10

a. Risk factors for development of posttransplant CMV infection and disease

i. Donor/recipient CMV immunoglobulin G (IgG) serostatus 1. Greatest risk factor for development of CMV disease (see Table 2)

a. Overall rate of CMV infection and disease among CMV naïve recipients receiving seropositive organs is approximately 56% to 68%

2. Measure anti-CMV IgG before transplantation a. Indicates prior exposure to CMV b. Performed on both the organ donor and recipient c. Recorded as Donor +/Recipient + (D+/R+) d. Determines pharmacologic prophylactic strategy

Table 2. Risk Stratification Based on Donor and Recipient Serostatus1,2

Donor status Recipient status

High risk + -

Moderate risk +/- +

Low risk - -

ii. Degree of immunosuppression

1. Small bowel/heart/lung > kidney/pancreas > liver 2. Lung and small bowel considered to be at highest risk

iii. Use of lymphocyte-depleting agents 1. Alemtuzumab, antithymocyte globulin, rituximab

iv. Host factors 1. Age, comorbidity, leukopenia and lymphopenia, genetic factors

v. Others 1. Cold ischemia time, critical illness, stress

4

II. Posttransplantation assessment and monitoring1-3,11

a. Viral load testing

i. Important aid for diagnosing disease and monitoring response to therapy ii. Antigenemia assay

1. Detects pp65 antigen in CMV-infected peripheral blood leukocytes a. Reported as positive cells per 200,000 leukocytes

2. High specificity (99%) 3. Limitations

a. Poor sensitivity b. Labor intensive c. Limited utility in patients with leukopenia

i. Need an ANC ≥1000 cells/mL d. Lack of standardization

4. Mostly replaced by polymerase chain reaction iii. Quantitative nucleic acid testing (QNAT) by polymerase chain reaction (PCR)

1. Preferred method of diagnosis and monitoring of CMV infection and disease a. Increased precision, faster turnaround time, and high sensitivity and specificity

(94% and 92%, respectively) 2. Measures viral load

a. Reported as copies per milliliter b. Must be aware of institution-specific limit of detection (LOD) and limit of

quantification (LOQ) i. LOD is defined as lowest concentration of DNA that can be detected in

95% of replicates ii. Upper and lower LOQ are highest and lowest concentrations of DNA that

can be quantified with precision c. Lack of standardization between institutions

3. World Health Organization International Reference Standard (2011) a. Makes it possible for comparison of CMV PCRs across institutions

i. Reported as international units (IU) per milliliter b. Not all institutions have adopted this standard

Prevention of CMV Infection and Disease Following Solid Organ Transplantation

I. Optimal prevention of CMV infection and disease after SOT can significantly improve outcomes II. Prior to development of anti-CMV therapy

1,3,12

a. CMV infection occurred in up to 80% of transplant recipients with a mortality rate of those who developed tissue invasive disease being about 80 to 90%

b. Development of prophylactic strategies have reduced the incidence of CMV disease during the early posttransplantation period and minimized the effects of CMV disease

III. Prophylactic agents1,3,13-16,17

a. Ganciclovir (GCV) and valganciclovir (vGCV)

i. Nucleoside analogues active against CMV and HSV 1. GCV

a. Developed in the mid-1980s b. Indicated for the treatment of CMV retinitis in immunocompromised patients

and for the prevention of CMV in transplant recipients at risk for CMV disease 2. vGCV

a. Valyl ester prodrug of GCV b. Enhanced bioavailability and comparable efficacy to GCV c. Indicated for treatment of CMV retinitis in patients with AIDS, prevention of

CMV in high-risk patients (D+/R-) undergoing kidney, heart, kidney/pancreas transplantation

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ii. Mechanism of action (see Figure 2)

Figure 2. Ganciclovir mechanism of action13

iii. Dosing 1. GCV 5 mg/kg IV daily, adjusted for renal dysfunction 2. vGCV 900 mg by mouth daily, adjusted for renal dysfunction

a. Improved bioavailability with decreased pill burden iv. Monitoring

1. Complete blood count (CBC): neutropenia>anemia>thrombocytopenia 2. Renal function

b. CMV immunoglobulin (CMV Ig) i. Immunoglobulin containing standardized amount of antibody to CMV

1. Reduce incidence of serious CMV in those exposed to the virus ii. Indicated for prophylaxis of CMV disease after kidney, lung, liver, pancreas and heart

transplantation iii. Limited data to support its use for prophylaxis

1. Typically used only as an adjunct to antivirals IV. Methods of prophylaxis

1,2,10,18,19

a. Universal prophylaxis i. Prophylactic antivirals initiated immediately posttransplantation

1. Continued for three to twelve months ii. Prevention rates from 58% to 80%

b. Preemptive therapy i. Serial testing performed weekly or biweekly for the first few months posttransplantation

ii. Regardless of symptoms, treatment doses of antivirals are administered with any early evidence of CMV replication

iii. No widely acceptable viral load threshold to guide therapy due to lack of standardization of PCR results across centers

c. Hybrid approach i. Short term prophylaxis followed by preemptive therapy

ii. Clinical utility and efficacy not validated

d. Advantages and disadvantages of prophylactic regimens (see Table 3) i. Optimal preventive regimens are undefined due to the lack of randomized, controlled trials

Table 3. Comparison of Universal Prophylaxis and Preemptive Therapy4

Universal Prophylaxis Preemptive Therapy

Efficacy Good Good*

Late onset disease Common Rare

Cost Drug costs

$7678 + 6486 Monitoring costs

$7130 + 3748

Monitoring Drug toxicity PCR

Seroconversion benefit May improve --

Prophylaxis Against Other Herpes Viruses HSV, VZV No

Reduced indirect effects Yes Unknown

Antiviral resistance Yes Yes

*Less optimal in high risk populations; potential failure of weekly surveillance with rapid viral replication

HSV=herpes simplex virus; PCR=polymerase chain reaction; VZV=varicella zoster virus

Drug phosphorylation by UL97 kinase

Further phosphorylation

by cellular kinases

Active nucleoside analogue

triphosphate

Competitive inhibition of viral DNA polymerase

6

e. Consensus1-3

(see Table 4) i. Universal prophylaxis is the preferred strategy for high risk D+/R- transplant recipients

ii. Preemptive therapy can be considered in moderate risk SOT patients 1. R+ 2. Kidney, liver, and heart transplants

Table 4. Consensus on the Use of Cytomegalovirus Prophylaxis Regimens*

D+/R- R+ D-/R-

Duration Liver, heart

Kidney, pancreas Lung

3-6 months

6 months 6-12 months

3 months 3 months

≥6 months

-- -- --

Medication Regimen Kidney, pancreas

Liver Lung, heart

vGCV or GCV vGCV or GCV

vGCV or GCV, + CMV Ig

Acyclovir Acyclovir Acyclovir

*See Appendix A for summary of major CMV prophylaxis trials GCV= 5 mg/kg IV daily; vGCV= 900 mg by mouth daily

f. Late-onset disease after prophylaxis discontinuation i. Disease occurring after discontinuation of antiviral prophylaxis

1. Typically within 3 to 6 months of antiviral discontinuation ii. Associated with higher rates of mortality and graft loss

iii. About 30% of D+/R- kidney, heart, pancreas, and liver recipients develop late-onset CMV after completing three months of prophylaxis

Treatment of CMV Posttransplantation

I. Indications for treatment initiation1,2,CDVPI

a. CMV viremia

i. All patients with CMV disease ii. Asymptomatic viremia

1. Patient and provider-specific II. Treatment regimen

25,26,13

a. Immunosuppressive dose reduction b. Antiviral medications

Figure 3. Timeline of antiviral development

7

i. Foscarnet (FOS) 1. Pyrophosphate analogue indicated for:

a. Treatment of CMV retinitis in patients with acquired immunodeficiency syndrome (AIDS)

b. Mucocutaneous acyclovir-resistant herpes simplex virus (HSV) infections in immunocompromised patients

2. Directly inhibits viral DNA polymerase without prior phosphorylation (see Figure 4) a. Forms a complex with the pyrophosphate binding site of viral DNA polymerase

i. Prevents the cleavage of pyrophosphate from deoxynucleotide triphosphates

3. Limitations a. Nephrotoxicity

i. Major dose-limiting side effect ii. Adequate hydration for prophylaxis recommended

1. Prior to first infusion: 750 to 1000 mL NS or D5W 2. Then, 750 to 1000 mL with each 90 to 120 mg/kg dose of FOS

b. Electrolyte abnormalities c. Neurotoxicity d. Fever, nausea and vomiting, anemia, and diarrhea

4. Use limited to patients who experience treatment failure with GCV or for those who have GCV contraindications due to neutropenia

Figure 4. Pharmacologic mechanisms of antivirals used for CMV13

ii. Cidofovir (CDV) 1. Acyclic nucleoside phosphonate (ANP) derivative

a. Must be phosphorylated via cellular kinases to diphosphoryl derivative to exert its antiviral activity (see Figure 4)

2. Potent inhibitor and alternate substrate for viral DNA polymerase 3. Indicated for treatment of CMV retinitis in patients with acquired immunodeficiency

syndrome (AIDS) 4. No data from randomized clinical trials to support its use in SOT recipients 5. Advantageous pharmacokinetic profile allows once weekly dosing

8

6. Toxicity profile limits its use a. Nephrotoxicity

i. Prophylaxis with fluids and probenecid recommended 1. 1000 mL NS over 1 to 2 hours prior to CDV infusion 2. Additional 1000 mL, infused over 1 to 3 hours, with start of CDV

infusion or immediately following infusion, if tolerable 3. Probenecid 2 g by mouth 3 hours prior to CDV 4. Probenecid 1 g by mouth at 2 hours and 8 hours after completion of

CDV infusion b. Neutropenia

III. Monitoring11

a. Response to treatment

i. PCR monitoring on day of treatment initiation and weekly thereafter b. Adverse reactions

IV. Duration1

a. Continue treatment until one to two consecutive negative samples are obtained i. Minimum two weeks of treatment

ii. Minimizes risk of disease recurrence and antiviral resistance V. Secondary prophylaxis

1

a. Treatment course followed by prophylactic dosing of antiviral medications to prevent recurrent disease

i. Typically for one to three months

Figure 5. Risk factors for CMV disease recurrence1

CMV Antiviral Resistance

I. Increasing or persistent viral load despite adequate antiviral therapy for greater than two weeks with confirmed resistance on genotypic and/or phenotypic testing

7

II. Prevalence and outcomes7,20-22

a. Estimates of antiviral resistance among SOT recipients varies greatly

i. D+/R- recipients have highest incidence 1. Rates of about 5% to 10% in D+/R- recipients being treated for CMV

ii. Lung transplant recipients have been observed to experience higher rates of antiviral resistance than rates observed in other SOT recipients

1. 17.6% of viremic lung transplant recipients versus 6.2% of viremic kidney recipients b. Clinical outcomes in SOT recipients after antiviral resistance development are poor

i. Mortality rates 19% to 100%

Increased Risk

Recurrent CMV

Primary CMV Infection

Multiorgan Disease

High Initial Viral Load

Slow Reduction in

Viral Load with Treatment

Persistent Viremia

Concurrent Treatment of

Rejection

9

III. Risk factors for antiviral resistance development1,2,7,23

a. Absence of preexisting CMV specific immunity prior to transplantation (D+/R-)

i. Most consistently identified risk factor b. Prolonged or inadequate antiviral drug exposure c. Ongoing active viral replication d. High levels of immunosuppressive medications e. Lung transplant f. High peak viral load

i. Greater than 105 copies/mL in peripheral blood

IV. Mutations associated with antiviral resistance7,13,20,24

a. UL97 mutation (see Figure 6)

i. Constitute greater than 95% of antiviral-resistant strains ii. Mutations in UL97 gene

1. Prevents initial phosphorylation of GCV 2. Confer various degrees of GCV resistance

a. Zero to 15 fold over baseline 3. These mutants will remain susceptible to FOS and CDV

iii. No significant fitness cost to the virus has been observed iv. Mechanisms of resistance

1. Modify substrate recognition 2. Modify ATP binding

Figure 6. Mutations associated with antiviral resistance to cytomegalovirus13

b. UL54 mutation (see Figure 6) i. UL54 gene encodes the viral DNA polymerase

ii. Antiviral resistance depends of the site of the mutation of the viral DNA polymerase 1. Can confer resistance to GCV, vGCV, FOS, and/or CDV

iii. Isolated UL54 mutations uncommon 1. Typically evolve after UL97 mutations 2. Dual UL97/UL54 mutations present with high-grade GCV resistance (IC50≥30μM)

iv. Mechanisms of resistance 1. Reduced antiviral affinity

a. Proposed mechanism for FOS resistance 2. Reduced DNA chain incorporation 3. Increased antiviral excision out of the DNA chain

10

V. Laboratory diagnosis of antiviral resistance7,13,20,24

a. Rapid laboratory confirmation of antiviral resistance is important

i. Increasing viral loads or disease progression may be due to host factors rather than antiviral resistance

1. Empiric changes in antiviral treatment may therefore lead to unnecessary toxicity through exposure to other drug therapies

2. Antiviral resistance should be confirmed before altering antiviral treatment regimens a. Except in life or sight-threatening disease

b. Phenotypic assay i. Reference standard for assessing antiviral susceptibility

1. Labor intensive 2. Four to six week turnaround time for results 3. Rarely used in clinical practice

ii. Determination of drug concentration required to inhibit 50% or 90% (IC50 or IC90) of viral growth

1. Specific sequence of clinical strain is transferred to a reference laboratory CMV strain iii. Proposed cutoffs for antiviral susceptibilities

1. GCV IC50>6 to 12 μM 2. FOS IC50>300-500 μM 3. CDV IC50 ≥2 μM

c. Genotypic testing i. More commonly used in the clinical setting to test for CMV antiviral resistance

1. Produces results in as quick as a few hours or up to three days ii. PCR amplification and sequencing of resistance loci from clinical specimens

1. Compared to known resistant or wild-type strain to categorize mutation sensitivity to antivirals

2. IC50 ratio = IC50 of mutant/IC50 of wild type a. IC50 ratio>3 is classified as resistance b. IC50 ratio>5 is classified as major resistance

iii. Disadvantage 1. Resistance mutations cannot be distinguished from sequence polymorphisms without

confirmation with phenotypic assays VI. Cross-resistance between antiviral therapies

20

Figure 7. Cross-resistance observed among antiviral therapies20

Treatment of GCV-Resistant CMV

I. No controlled clinical trials to support the use of specific treatment regimens in cases where drug resistance is suspected or proven

II. Standardized approach to the treatment of antiviral-resistant CMV infection and disease is difficult a. Diversity of host factors affect clinical outcome in SOT recipients

•GCV/vGCV resistance

•Cross-resistance with other antivirals not seen

UL97 Mutations

• Common: GCV and CDV cross-resistance

• Rare: GCV and FOS cross-resistance

• Rare: FOS and CDV cross-resistanceUL54 Mutations

11

b. Changes in therapy must consider potency, toxicity, and logistical complexity of the available alternative antiviral agents

III. Reduction of immunosuppressive therapy25

a. Retrospective review of patient population included in the VICTOR trial

25

i. Significantly greater proportion of patients treated with dual versus triple immunosuppressive therapy eradicated CMV DNAemia by day 21 (71.3% vs. 52%)

ii. No effect on risk of recurrence IV. Antiviral therapy

13,26

Table 5. Comparison of Antiviral Agents Approved for Treatment of CMV13,26,27

GCV FOS CDV Mechanism of action Inhibit viral DNA polymerase

Indication -CMV retinitis

-CMV prophylaxis -CMV retinitis in AIDS

-HSVa

-CMV retinitis in AIDS

Doseb

5 mg/kg IV twice daily 90 mg/kg IV twice daily 5 mg/kg IV once weekly

Major adverse effects Neutropenia > anemia >

thrombocytopenia Nephrotoxicity, electrolyte

abnormalities Nephrotoxicity,

neutropenia Mutations that confer

resistance UL97 UL54

UL54 UL54

a Mucotaneous acyclovir-resistant herpes simplex virus infections in immunocompromised patients

b Adjusted for renal function

a. Foscarnet i. Case Reports

28,29

Table 6. Case Reports of Severe CMV Disease Treated with Foscarnet28,29

Patient 1 Patient 2 Patient 3 Patient 4

Age (years) 59 64 40 52

Type of transplant Kidney Kidney Kidney Heart

Serology D?/R- D?/R- D?/R- D-/R-

Induction -- -- -- ATG

IS regimen CsA + CCSa

CsA + CCSa

CsA + CCS

TAC, AZA, CCS

Rejection (day) 29 44 28, 74, 128 --

Rejection treatment CCS CCS CCS --

Type of CMV disease PNA, Renal CNS?, PNA? PNA GI?, Renal?

CMV symptoms (day)

48 50 <60 (not treated);

134 37

FOS initiation (day) 69 66 143 43

FOS dose 3.3 mg/kg/hr 3.3 mg/kg/hr 3.24 mg/kg/hr ?

Duration of FOS (days) 5 5 8 15

Clinical improvement during treatment

Y Y Y Y

Adverse events (SrCrBeg-SrCrEnd)

↑SrCrb,c

(3.17-4.63)

-- (2-1.38)

-- (3.17-3.17)

↑SrCrb,d

(7.12-3.39)

Outcome (day) Death (75)

Alive + graft (290)

Alive + graft (290)

Alive + graft (180)

Alive + graft=patient alive with functioning graft; ATG=antithymocyte globulin; AZA=azathioprine; CCS=corticosteroid; CNS=encephalitis; CsA=cyclosporine; FOS=foscarnet; PNA=pneumonitis; SrCrBeg-SrCrEnd=serum creatinine (mg/dL) at beginning and end of FOS therapy; TAC=tacrolimus a

Immunosuppression discontinued with symptom onset or initiation of FOS; b

Patient also received gentamicin; c FOS discontinued

due to nephrotoxicity; d

Patient required hemodialysis even before initiation of FOS or gentamicin

12

c. Recent use of foscarnet and cidofovir i. Single center, retrospective analysis

30

ii. 1549 SOT recipients who all received vGCV universal prophylaxis iii. 284 (18.3%) patients tested positive for CMV infection

1. 20/56 recipients genotypically tested had resistance mutations a. 80% D+/R- b. Detected a median of 9 months posttransplantation

Table 7. 20 Patients with Resistant Strains30

16 UL97 1 UL54 3 UL97 and UL54

7 kidney 3 heart 3 lung 2 liver

1 kidney/pancreas

1 lung 3 lung

iv. Foscarnet and cidofovir therapy

Figure 8. Patient population in Perez et al.

30

v. Toxicity

1. No significant changes in renal function were observed vi. Take-home points

1. FOS appears useful for the treatment of severe, symptomatic CMV disease 2. Cases with known antiviral resistance were only presented in abstract form

a. Many details unknown 3. CDV appears useful for the treatment of CMV containing UL97 mutations

20 patients with resistant strains

6 recipients treated with FOS

-2 UL97

-1 UL54

-3 UL97 and UL54

2 responded

(relapsed once FOS discontinued)

1 maintained low level viremia

CDV added and viremia cleared

1 patient still on FOS

2 deaths

14 recipients treated with CDV

All UL97 mutations

13 achieved CMV clearance

1 death

13

b. High-dose GCV31

i. Case series

1. To assess the utility of high-dose GCV for the treatment of non-severe CMV replication in patients with GCV-resistant strains

2. Clinical resistance a. Persistent viral load or symptom development after 2 weeks GCV or vGCV

treatment b. Patients 1, 2, 3, and 5 had mutations conferring high grade resistance

Table 8. Use of High-Dose GCV in Patients with Asymptomatic CMV Posttransplantation31

Patient 1 Patient 2 Patient 3 Patient 4 Patient 5 Patient 6a

Type of transplant

Kidney Kidney Kidney Kidney-

pancreas Liver Kidney

Induction ATG -- -- -- -- --

IS regimen T/M/S T/M/S T/M/S T/M/S T/M/S T/M/S

CMV serology D+/R- D-/R+ D+/R- D+/R- D+/R- D+/R-

Prophylaxis PT PT UP UP UP UP

Symptomatic CMV

replication N N N

Y (Colitis)

N N

Mutation UL97b UL97

b UL97

b UL97 UL97

b UL54

Treatment regimen

(duration in days)

Int GCV (12) Int GCV (7),

Full GCV (21) Int GCV (21) Int GCV (28)

Int GCV (14), Full GCV (14), Int vGCV (14)

Full vGCV (56)

Dose limiting neutropenia

Y (GCSF)

N N N N N

Outcome (time post-infection)

Alive + graft (10 months)

Alive + graft (1 year)

Alive + graft (2 years)

Alive + graft (1 year)

Alive + graft (2 years)

Alive + graft (2 years)

Alive + graft=patient alive with functioning graft; ATG=antithymocyte globulin; Full GCV=ganciclovir 10 mg/kg IV every 12 hours, adjusted for renal function; Full vGCV=valganciclovir 1800 mg by mouth twice daily, adjusted for renal function; GCSF=granulocyte colony-stimulating factor 30 x 10

6 for two doses; Int GCV=ganciclovir 7.5 mg/kg IV every 12 hours, adjusted

for renal function; Int vGCV=valganciclovir 1350 mg by mouth twice daily, adjusted for renal function; IS=immunosuppressive; M=mycophenolate mofetil; N=no; PT=preemptive therapy; S=steroid; T=tacrolimus; UP=universal prophylaxis for 90 days with vGCV; Y=yes a

UL54 mutation detected, but patient refused foscarnet; b High grade antiviral resistance

ii. Take-home points

1. Non-severe, asymptomatic disease with UL97 mutations 2. Dose-limiting neutropenia occurred in one of six patients 3. Increasing doses of GCV were effective despite mutations conferring high-grade

resistance

14

c. Combination therapy i. Synergy between GCV and FOS has been demonstrated in vitro

32

ii. Other immunocompromised populations 1. Addition of FOS to failing GCV monotherapy, or addition of GCV to failing FOS, has

been shown to be superior to continuing monotherapy or switching to monotherapy with another medication

33

iii. Case series34

1. Massachusetts General Hospital

a. Oral GCV prophylaxis for 3 months posttransplantation i. D+/R-

ii. R+ patients who receive antilymphocyte agents for induction or graft rejection

b. CMV antigenemia assay monitored monthly i. Persistently positive antigenemia

1. Treatment dose GCV IV and monthly CMV Ig c. CMV Disease

i. Diagnosed 3 months to 2 years posttransplantation (median 5 months)

Figure 9. Patient population in Mylonakis et al.34

d. Treatment i. Combination therapy

1. GCV 5 mg/kg IV daily 2. FOS titrated to max of 125 mg/day 3. CMV Ig

e. Secondary prophylaxis i. Oral GCV and monthly CMV Ig for 3 months

f. Adverse effects i. FOS-induced electrolyte abnormalities, specifically magnesium wasting

g. All patients had antigenemia levels of zero by 4 to 8 weeks h. No relapses observed after 12 to 36 month follow-up i. Take-home points

i. Low-dose combination therapy of GCV and FOS can be beneficial in SOT recipients infected with GCV-resistant CMV 1. Unknown which mutation was being treated

ii. Magnesium wasting was the major adverse effect observed

6 SOT Recipients

•2 Lung, 2 liver, 1 kidney, 1 heart

•5 D+/R-, 1 R+

GCV Resistance

•Suspected based on persistent symptoms despite ≥3 weeks of GCV

•Confirmed with minimum inhibitory concentration (MIC) testing

Susceptibility Testing

•All isolates had high level ganciclovir resistance (MIC ≥3 μg/mL)

15

1. Patients required 10 g to 24 g of magnesium supplementation daily iii. Regimen did not lead to increased antiviral resistance

V. Adjunct therapy1,35,36

a. Immunosuppressive drugs with anti-CMV activity

i. Leflunomide 1. Prodrug indicated for the treatment of rheumatoid arthritis 2. Immunosuppressive and antiviral properties

a. Novel mechanism of action compared to currently used antivirals for CMV i. Inhibits B-cell and T-cell proliferation

ii. Interferes with viral capsid assembly 3. Dosing

a. 100 mg/day by mouth for 3 days , followed by 20 mg/day b. Therapeutic monitoring

i. Target range 50-80 mcg/mL 4. Adverse reactions

a. Diarrhea, anemia, hepatotoxicity b. Viral clearance delayed when compared to IV GCV

5. Retrospective chart review36

a. 15 SOT recipients who received leflunomide after failure of other antivirals

i. 13 D+/R-, 1 D-/R-, 1 unknown ii. 3 kidney, 1 pancreas, 5 kidney/pancreas, 2 heart, and 2 lung

b. Patients receiving a calcineurin inhibitor, mycophenolate mofetil (MMF), and corticosteroid for immunosuppression i. Dose of MMF was typically reduced or removed from the regimen due to

antirejection effects of leflunomide c. 53% of patients achieved long-term suppression of CMV recurrences d. Testing form UL97 and UL54

i. Via genotyping in 16 patients ii. Mammalian target of rapamycin (mTOR) inhibitor

1. Both immunosuppressive and antiviral properties 2. Some evidence that switching recipients’ immunosuppressive therapy to an mTOR

inhibitor may lead to a lower incidence of CMV infection and disease

Future Options

I. Hexadecyloxypropyl cidofovir conjugate (CMX001)37

a. Orally bioavailable cidofovir derivative

i. Not concentrated in the renal tubules, so less likely to cause nephrotoxicity b. Major adverse effect: diarrhea c. Cross-resistance with CDV expected

II. Letermovir (AIC246)1

a. Inhibits formation and release of infectious virus particles via targeting the UL56 viral terminase complex

b. Currently undergoing phase II clinical trials c. No cross-resistance with current antivirals expected

III. Maribavir1,7

a. Oral UL97 inhibitor with good bioavailability and low toxicity b. Phase III trials in D+/R- liver SOT and hematopoietic stem cell transplant recipients

i. No antiviral efficacy observed ii. Currently undergoing trials to investigate efficacy of maribavir at higher dose

c. Resistance involves UL27 and UL97 genes IV. Vaccine

1

a. Currently under development, but none are available for clinical use

16

Summary and Recommendations

I. Summary a. CMV incidence has decreased dramatically with the implementation of ganciclovir prophylaxis b. When CMV does occur, it significantly impacts both patient and graft survival c. Resistance to ganciclovir is a growing problem among adult solid organ transplant recipients d. Inadequate literature to support treatment decisions when resistance is encountered e. Furthermore, lack of alternative antivirals, antiviral cross-resistance, and drug toxicity makes

choosing an optimal treatment regimen difficult II. Recommendations (see Figure 10)

a. Selection of an alternative treatment regimen for GCV-resistant CMV is highly patient-specific b. Factors to consider

i. Severity of disease, degree of immunosuppression, presence of concurrent organ rejection, viral load, mutations present, exposure and tolerability to previous antiviral medications

17

Figure 10. Suggested treatment algorithm for ganciclovir-resistant cytomegalovirus

Suspected Resistance

-Consider reducing immunosuppression

-Send for genotypic resistance testing

Asymptomatic or Non-Severe

CMV Disease

High-dose GCV

or

Combination low-dose GCV + FOS

Response?

Yes

Continue high-dose GCV

or

Combination therapy

No

FOS

Severe

CMV Disease

Life or sight-threatening disease

Immediate change in antiviral therapy

FOS

or

CDV

CDV=cidofovir; CMV=cytomegalovirus; FOS=foscarnet; GCV=ganciclovir

18

References

1. Kotton CN, Kumar D, Caliendo AM, et al. Updated international consensus guidelines on the management of cytomegalovirus in solid-organ transplantation. Transplantation 2013;96(4):333-60.

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Appendix

Appendix A. Summary of Major Cytomegalovirus Prophylaxis Studies19,38-40

Paya et al.38

IMPACT39

Palmer et al.19

Copeland et al.40

N 372 326 136 38

Study design P, R, DB, DD study MC, DB, R, PC trial P, MC, DB, PC, R trial Follow up of Palmer et al. study

Serostatus D+/R- D+/R- -D+/R- (33%) -D+/R+ (31%) -D-/R+ (36%)

-D+/R- (24%) -R+ (76%)

Type of transplant -Heart -Liver -Kidney -Multiorgan

-Kidney -Lung -Lung

Intervention vGCV 900 mg PO daily vs. GCV 1000 mg PO TID for prophylaxis

200 days vs. 100 days of vGCV 900 mg daily for CMV prophylaxis

vGCV 900 mg daily for 3 months vs. 12 months for prophylaxis

Mean follow up was 3.9 years

Outcome -vGCV found to be as clinically effective and of comparable safety to GCV in D+/R- recipients

-Significantly fewer patients in 200 day group developed confirmed disease at 12 months posttransplantation without the cost of additional safety concerns -Incidence of allograft function, graft loss, and survival were not different between groups at 1 and 2 years

-Incidence of CMV was significantly greater in patients who received 3 months of prophylaxis versus 12 months

-Long-term prophylaxis prevents rather than simply delays onset of CMV disease without increasing GCV resistance or adverse events

CMV=cytomegalovirus; DB=double blind; DD=double-dummy; D+/R+=donor/recipient serostatus; GCV=ganciclovir; MC=multicenter; N=number of patients; NS=not

significant; P=prospective; PC=placebo controlled; PO=by mouth; R=randomized; TID=three times a day; vGCV=valganciclovir