Valganciclovir hydrochloride

Valganciclovir hydrochloride is indicated for the induction and maintenance treatment of cytomegalovirus (CMV) retinitis in adult patients with acquired immunodeficiency syndrome (AIDS).

Valganciclovir hydrochloride is indicated for the prevention of CMV disease in CMV-negative adults and children (aged from birth to 18 years) who have received a solid organ transplant from a CMV-positive donor.

Caution - Strict adherence to dosage recommendations is essential to avoid overdose.

Valganciclovir hydrochloride is rapidly and extensively metabolised to ganciclovir after oral dosing. Oral Valganciclovir hydrochloride 900 mg twice daily is therapeutically equivalent to intravenous ganciclovir 5 mg/kg twice daily.

Posology

Treatment of cytomegalovirus (CMV) retinitis

Adult patients

Induction treatment of CMV retinitis:

For patients with active CMV retinitis, the recommended dose is 900 mg Valganciclovir hydrochloride (two Valganciclovir hydrochloride tablets) twice a day for 21 days and, whenever possible, taken with food. Prolonged induction treatment may increase the risk of bone marrow toxicity.

Maintenance treatment of CMV retinitis:

Following induction treatment, or in patients with inactive CMV retinitis, the recommended dose is 900 mg Valganciclovir hydrochloride (two Valganciclovir hydrochloride tablets) once daily and, whenever possible, taken with food. Patients whose retinitis worsens may repeat induction treatment; however, consideration should be given to the possibility of viral drug resistance.

Paediatric population

The safety and efficacy of Valganciclovir hydrochloride in the treatment of CMV retinitis have not been established in adequate and well-controlled clinical studies in paediatric patients.

Prevention of CMV disease in solid organ transplantation:

Adult patients

For kidney transplant patients, the recommended dose is 900 mg (two Valganciclovir hydrochloride tablets) once daily, starting within 10 days post-transplantation and continuing until 100 days post-transplantation. Prophylaxis may be continued until 200 days post-transplantation.

For patients who have received a solid organ transplant other than kidney, the recommended dose is 900 mg (two Valganciclovir hydrochloride tablets) once daily, starting within 10 days post-transplantation and continuing until 100 days post-transplantation.

Paediatric population

In paediatric solid organ transplant patients, aged from birth, who are at risk of developing CMV disease, the recommended once daily dose of Valganciclovir hydrochloride is based on body surface area (BSA) and creatinine clearance (derived from Schwartz formula (CrCLS), and is calculated using the equation below:

Paediatric Dose (mg) = 7 x BSA x CrCLS (see Mosteller BSA formula and Schwartz Creatinine Clearance formula below).

If the calculated Schwartz creatinine clearance exceeds 150 ml/min/1.73m², then a maximum value of 150 ml/min/1.73m² should be used in the equation:

Serum Creatinine (mg/dl)

where k = 0.45* for patients aged < 2 years, 0.55 for boys aged 2 to < 13 years and girls aged 2 to 16 years, and 0.7 for boys aged 13 to 16 years. Refer to adult dosing for patients older than 16 years of age.

The k values provided are based on the Jaffe method of measuring serum creatinine and may require correction when enzymatic methods are used.

*For appropriate sub-populations a lowering of k value may also be necessary (e.g. in paediatric patients with low birth weight).

For paediatric kidney transplant patients, the recommended once daily mg dose (7 x BSA x CrCLS) should start within 10 days post-transplantation and continue until 200 days post-transplantation.

For paediatric patients who have received a solid organ transplant other than kidney, the recommended once daily mg dose (7x BSA x CrCLS) should start within 10 days post-transplantation and continue until 100 days post-transplantation.

All calculated doses should be rounded to the nearest 25 mg increment for the actual deliverable dose. If the calculated dose exceeds 900 mg, a maximum dose of 900 mg should be administered. An oral solution is the preferred formulation since it provides the ability to administer a dose calculated according to the formula above; however, Valganciclovir hydrochloride tablets may be used if the calculated doses are within 10% of available tablet doses, and the patient is able to swallow tablets. For example, if the calculated dose is between 405 mg and 495, one 450 mg tablet may be taken.

It is recommended to monitor serum creatinine levels regularly and consider changes in height and body weight and adapt the dose as appropriate during the prophylaxis period.

Special dosage instructions

Renal impairment

Serum creatinine levels or creatinine clearance should be monitored carefully. Dosage adjustment is required according to creatinine clearance, as shown in the table below.

An estimated creatinine clearance (ml/min) can be related to serum creatinine by the following formulae:

For females = 0.85 x male value

Patients undergoing haemodialysis:

For patients on haemodialysis (CrCl < 10 ml/min) a dose recommendation cannot be given. Thus Valganciclovir hydrochloride should not be used in these patients.

Hepatic impairment:

The safety and efficacy of Valganciclovir hydrochloride has not been studied in patients with hepatic impairment.

Paediatric population:

Dosing of paediatric SOT patients is individualised based on a patient's renal function, together with body length and weight.

Elderly patients:

Safety and efficacy of Valganciclovir hydrochloride has not been established in this patient population.

Patients with severe leucopenia, neutropenia, anaemia, thrombocytopenia and pancytopenia:

If there is a significant deterioration of blood cell counts during therapy with Valganciclovir hydrochloride, treatment with haematopoietic growth factors and/or dose interruption should be considered.

Method of administration

Valganciclovir hydrochloride tablets are administered orally, and whenever possible, should be taken with food.

For paediatric patients who are unable to swallow Valganciclovir hydrochloride tablets, other formulations, which may be available, should be used.

Precautions to be taken before handling or administering the medicinal product

The tablets should not be broken or crushed. Since Valganciclovir hydrochloride is considered a potential teratogen and carcinogen in humans, caution should be observed in handling broken tablets. Avoid direct contact of broken or crushed tablets with skin or mucous membranes. If such contact occurs, wash thoroughly with soap and water, rinse eyes thoroughly with sterile water, or plain water if sterile water is unavailable.

Due to the similarity of the chemical structure of Valganciclovir hydrochloride and that of aciclovir and valaciclovir, a cross-hypersensitivity reaction between these medicinal products is possible. Therefore, Valganciclovir hydrochloride is contraindicated in patients with hypersensitivity to aciclovir and valaciclovir.

Valganciclovir hydrochloride is contraindicated during breast-feeding.

Prior to the initiation of Valganciclovir hydrochloride treatment, patients should be advised of the potential risks to the foetus. In animal studies, ganciclovir was found to be mutagenic, teratogenic, aspermatogenic and carcinogenic, and a suppressor of female fertility. Valganciclovir hydrochloride should, therefore, be considered a potential teratogen and carcinogen in humans with the potential to cause birth defects and cancers. It is also considered likely that Valganciclovir hydrochloride causes temporary or permanent inhibition of spermatogenesis. Women of childbearing potential must be advised to use effective contraception during treatment. Men must be advised to practise barrier contraception during treatment, and for at least 90 days thereafter, unless it is certain that the female partner is not at risk of pregnancy.

Valganciclovir hydrochloride has the potential to cause carcinogenicity and reproductive toxicity in the long term.

Severe leucopenia, neutropenia, anaemia, thrombocytopenia, pancytopenia, bone marrow depression and aplastic anaemia have been observed in patients treated with Valganciclovir hydrochloride (and ganciclovir). Therapy should not be initiated if the absolute neutrophil count is less than 500 cells/μl, or the platelet count is less than 25000/μl, or the haemoglobin level is less than 8 g/dl.

When extending prophylaxis beyond 100 days the possible risk of developing leucopenia and neutropenia should be taken into account.

Valganciclovir hydrochloride should be used with caution in patients with pre-existing haematological cytopenia or a history of drug-related haematological cytopenia and in patients receiving radiotherapy.

It is recommended that complete blood counts and platelet counts should be monitored regularly during therapy. Increased haematological monitoring may be warranted in patients with renal impairment and paediatrics, at a minimum each time the patient attends the transplant clinic. In patients developing severe leucopenia, neutropenia, anaemia and/or thrombocytopenia, it is recommended that treatment with haematopoietic growth factors and/or dose interruption be considered.

The bioavailability of ganciclovir after a single dose of 900 mg Valganciclovir hydrochloride is approximately 60 %, compared with approximately 6 % after administration of 1000 mg oral ganciclovir (as capsules). Excessive exposure to ganciclovir may be associated with life-threatening adverse reactions. Therefore, careful adherence to the dose recommendations is advised when instituting therapy, when switching from induction to maintenance therapy and in patients who may switch from oral ganciclovir to Valganciclovir hydrochloride as Valganciclovir hydrochloride cannot be substituted for ganciclovir capsules on a one-to-one basis. Patients switching from ganciclovir capsules should be advised of the risk of overdosage if they take more than the prescribed number of Valganciclovir hydrochloride tablets.

In patients with impaired renal function, dosage adjustments based on creatinine clearance are required.

Valganciclovir hydrochloride should not be used in patients on haemodialysis.

Convulsions have been reported in patients taking imipenem-cilastatin and ganciclovir. Valganciclovir hydrochloride should not be used concomitantly with imipenem-cilastatin unless the potential benefits outweigh the potential risks.

Patients treated with Valganciclovir hydrochloride and (a) didanosine, (b) medicinal products that are known to be myelosuppressive (e.g. zidovudine), or (c) substances affecting renal function, should be closely monitored for signs of added toxicity.

No studies on the effects on ability to drive and use machines have been performed.

Convulsions, sedation, dizziness, ataxia, and/or confusion have been reported with the use of Valganciclovir hydrochloride and/or ganciclovir. If they occur, such effects may affect tasks requiring alertness, including the patient's ability to drive and operate machinery.

a. Summary of the safety profile

Valganciclovir hydrochloride is a prodrug of ganciclovir, which is rapidly and extensively metabolised to ganciclovir after oral administration. The undesirable effects known to be associated with ganciclovir use can be expected to occur with Valganciclovir hydrochloride. All of the undesirable effects observed with Valganciclovir hydrochloride clinical studies have been previously observed with ganciclovir.

The most commonly reported adverse drug reactions following administration of Valganciclovir hydrochloride in adults are neutropenia, anaemia and diarrhoea.

Valganciclovir hydrochloride is associated with a higher risk of diarrhoea compared to intravenous ganciclovir. In addition, Valganciclovir hydrochloride is associated with a higher risk of neutropenia and leucopenia compared to oral ganciclovir.

Severe neutropenia (ANC < 500 cells/μl) is seen more frequently in AIDS patients with CMV retinitis undergoing treatment with Valganciclovir hydrochloride than in solid organ transplant patients receiving Valganciclovir hydrochloride.

The frequency of adverse reactions reported in clinical trials with either Valganciclovir hydrochloride, oral ganciclovir, or intravenous ganciclovir is presented in the table below.

Frequencies are defined as very common (> 1/10), common (> 1/100 to < 1/10), uncommon (> 1/1,000 to < 1/100) and rare (> 1/10,000 to < 1/1,000).

The adverse reactions listed were reported in clinical trials in patients with AIDS for the induction or maintenance treatment of CMV retinitis, or in liver, kidney or heart transplant patients for the prophylaxis of CMV disease. The term (severe) in parenthesis in the table indicates that the adverse reaction has been reported in patients at both mild/moderate intensity and severe/life-threatening intensity at that specific frequency.

The overall safety profile of Valganciclovir hydrochloride did not change with the extension of prophylaxis up to 200 days in adult kidney transplant patients at high risk of CMV disease (D+/R-). Leucopenia was reported with a slightly higher incidence in the 200 days arm while the incidence of neutropenia, anaemia and thrombocytopenia were similar in both arms.

b. Tabulated list of adverse reactions

Within each frequency grouping, undesirable effects are presented in order of decreasing seriousness.

Severe thrombocytopenia may be associated with potentially life-threatening bleeding.

Retinal detachment has only been reported in AIDS patients treated with Valganciclovir hydrochloride for CMV retinitis.

c. Paediatric population

Valganciclovir hydrochloride has been studied in 179 paediatric solid organ transplant patients who were at risk of developing CMV disease (aged 3 weeks to 16 years) and in 133 neonates with symptomatic congenital CMV disease (aged 2 to 31 days), with duration of ganciclovir exposure ranging from 2 to 200 days.

The most frequently reported adverse reactions on treatment in paediatric clinical trials were diarrhoea, nausea, neutropenia, leucopenia and anaemia.

In solid organ transplant patients, the overall safety profile was similar in paediatric patients as compared to adults. However, the rates of certain adverse events, such as upper respiratory tract infection, pyrexia, abdominal pain and dysuria, which may be characteristic of the paediatric population, were reported in higher incidence in paediatrics than in adults. Neutropenia was also reported with slightly higher incidence in the two studies conducted in paediatric solid organ transplant patients as compared to adults, but there was no correlation between neutropenia and infectious adverse events in the paediatric population.

In kidney transplant paediatric patients, prolongation of Valganciclovir hydrochloride exposure up to 200 days was not associated with an overall increase in the incidence of adverse events. The incidence of severe neutropenia (ANC < 500/µl) was higher in paediatric kidney patients treated until Day 200 as compared to paediatric patients treated until Day 100 and as compared to adult kidney transplant patients treated until Day 100 or Day 200.

Only limited data are available in neonates or infants with symptomatic congenital CMV infection treated with Valganciclovir hydrochloride, however the safety appears to be consistent with the known safety profile of Valganciclovir hydrochloride/ganciclovir.

Reporting of suspected adverse reactions

Reporting suspected adverse reactions after authorisation of the medicinal product is important. It allows continued monitoring of the benefit/risk balance of the medicinal product. Healthcare professionals are asked to report any suspected adverse reactions via the Yellow Card Scheme Website: www.mhra.gov.uk/yellowcard.

Symptoms

Overdose experience with Valganciclovir hydrochloride

One adult developed fatal bone marrow depression (medullary aplasia) after several days of dosing that was at least 10-fold greater than recommended for the patient's degree of renal impairment (decreased creatinine clearance).

It is expected that an overdose of Valganciclovir hydrochloride could also possibly result in increased renal toxicity.

Overdose experience with intravenous ganciclovir

Reports of overdoses with intravenous ganciclovir have been received from clinical trials and during post-marketing experience. In some of these cases no adverse events were reported. The majority of patients experienced one or more of the following adverse events:

- Haematological toxicity: pancytopenia, bone marrow depression, medullary aplasia, leucopenia, neutropenia, granulocytopenia.

- Hepatotoxicity: hepatitis, liver function disorder.

- Renal toxicity: worsening of haematuria in a patient with pre-existing renal impairment, acute renal failure, elevated creatinine.

- Gastrointestinal toxicity: abdominal pain, diarrhoea, vomiting.

- Neurotoxicity: generalised tremor, convulsion.

Management

Haemodialysis and hydration may be of benefit in reducing blood plasma levels in patients who receive an overdose of Valganciclovir hydrochloride.

Pharmacotherapeutic group: Antivirals for systemic use, nucleosides and nucleotides excl. reverse transcriptase inhibitors, ATC code: J05A B14

Mechanism of action

Valganciclovir hydrochloride is an L-valyl ester (prodrug) of ganciclovir. After oral administration, Valganciclovir hydrochloride is rapidly and extensively metabolised to ganciclovir by intestinal and hepatic esterases. Ganciclovir is a synthetic analogue of 2'-deoxyguanosine and inhibits replication of herpes viruses in vitro and in vivo. Sensitive human viruses include human cytomegalovirus (HCMV), herpes simplex virus-1 and -2 (HSV-1 and HSV-2), human herpes virus -6, -7 and -8 (HHV-6, HHV-7, HHV8), Epstein-Barr virus (EBV), varicella-zoster virus (VZV) and hepatitis B virus (HBV).

In CMV-infected cells, ganciclovir is initially phosphorylated to ganciclovir monophosphate by the viral protein kinase, pUL97. Further phosphorylation occurs by cellular kinases to produce ganciclovir triphosphate, which is then slowly metabolised intracellularly. Triphosphate metabolism has been shown to occur in HSV- and HCMV- infected cells with half-lives of 18 and between 6 and 24 hours respectively, after the removal of extracellular ganciclovir. As the phosphorylation is largely dependent on the viral kinase, phosphorylation of ganciclovir occurs preferentially in virus-infected cells.

The virustatic activity of ganciclovir is due to inhibition of viral DNA synthesis by: (a) competitive inhibition of incorporation of deoxyguanosine-triphosphate into DNA by viral DNA polymerase, and (b) incorporation of ganciclovir triphosphate into viral DNA causing termination of, or very limited, further viral DNA elongation.

Antiviral activity

The in-vitro anti-viral activity, measured as IC₅₀ of ganciclovir against CMV, is in the range of 0.08 μM (0.02 μg/ml) to 14 μM (3.5 μg/ml).

The clinical antiviral effect of Valganciclovir hydrochloride has been demonstrated in the treatment of AIDS patients with newly diagnosed CMV retinitis. CMV shedding was decreased in urine from 46 % (32/69) of patients at study entry to 7 % (4/55) of patients following four weeks of Valganciclovir hydrochloride treatment.

Clinical efficacy and safety

Adult patients

Treatment of CMV retinitis:

Patients with newly diagnosed CMV retinitis were randomised in one study to induction therapy with either Valganciclovir hydrochloride 900 mg (twice daily) or intravenous ganciclovir 5 mg/kg (twice daily). The proportion of patients with photographic progression of CMV retinitis at week 4 was comparable in both treatment groups, 7/70 and 7/71 patients progressing in the intravenous ganciclovir and Valganciclovir hydrochloride arms respectively.

Following induction treatment dosing, all patients in this study received maintenance treatment with Valganciclovir hydrochloride given at the dose of 900 mg once daily. The mean (median) time from randomisation to progression of CMV retinitis in the group receiving induction and maintenance treatment with Valganciclovir hydrochloride was 226 (160) days and in the group receiving induction treatment with intravenous ganciclovir and maintenance treatment with Valganciclovir hydrochloride was 219 (125) days.

Prevention of CMV disease in transplantation:

A double-blind, double-dummy clinical active comparator study has been conducted in heart, liver and kidney transplant patients (lung and gastrointestinal transplant patients were not included in the study) at high-risk of CMV disease (D+/R-) who received either Valganciclovir hydrochloride (900 mg once daily) or oral ganciclovir (1000 mg three times daily) starting within 10 days of transplantation until Day 100 post-transplant. The incidence of CMV disease (CMV syndrome + tissue invasive disease) during the first 6 months post-transplant was 12.1 % in the Valganciclovir hydrochloride arm (n=239) compared with 15.2 % in the oral ganciclovir arm (n=125). The large majority of cases occurred following cessation of prophylaxis (post-Day 100) with cases in the Valganciclovir hydrochloride arm occurring on average later than those in the oral ganciclovir arm. The incidence of acute rejection in the first 6 months was 29.7 % in patients randomised to Valganciclovir hydrochloride compared with 36.0 % in the oral ganciclovir arm, with the incidence of graft loss being equivalent, occurring in 0.8 % of patients, in each arm.

A double-blind, placebo controlled study has been conducted in 326 kidney transplant patients at high risk of CMV disease (D+/R-) to assess the efficacy and safety of extending Valganciclovir hydrochloride CMV prophylaxis from 100 to 200 days post-transplant. Patients were randomised (1:1) to receive Valganciclovir hydrochloride tablets (900 mg once daily) within 10 days of transplantation either until Day 200 post-transplant or until Day 100 post-transplant followed by 100 days of placebo.

The proportion of patients who developed CMV disease during the first 12 months post-transplant is shown in the table below.

Percentage of Kidney Transplant Patients with CMV Disease¹, 12 Month ITT Population^A

¹ CMV Disease is defined as either CMV syndrome or tissue invasive CMV.

² Confirmed CMV is a clinically confirmed case of CMV disease. Patients were assumed to have CMV disease if there was no week 52 assessment and no confirmation of CMV disease before this time point.

^A The results found up to 24 months were in line with the up to 12 month results: Confirmed or assumed CMV disease was 48.5% in the 100 days treatment arm versus 34.2% in the 200 days treatment arm; difference between the treatment groups was 14.3% [3.2 %; 25.3%].

Significantly less high risk kidney transplant patients developed CMV disease following CMV prophylaxis with Valganciclovir hydrochloride until Day 200 post-transplant compared to patients who received CMV prophylaxis with Valganciclovir hydrochloride until Day 100 post-transplant.

The graft survival rate as well as the incidence of biopsy proven acute rejection was similar in both treatment groups. The graft survival rate at 12 months post-transplant was 98.2 % (160/163) for the 100 day dosing regimen and 98.1 % (152/155) for the 200 day dosing regimen. Up to 24 month post-transplant, four additional cases of graft loss were reported, all in the 100 days dosing group. The incidence of biopsy proven acute rejection at 12 months post-transplant was 17.2% (28/163) for the 100 day dosing regimen and 11.0% (17/155) for the 200 day dosing regimen. Up to 24 month post-transplant, one additional case has been reported in the 200 days dosing group.

Viral resistance

Virus resistant to ganciclovir can arise after chronic dosing with Valganciclovir hydrochloride by selection of mutations in the viral kinase gene (UL97) responsible for ganciclovir monophosphorylation and/or the viral polymerase gene (UL54). In clinical isolates, seven canonical UL97 substitutions, M460V/I, H520Q, C592G, A594V, L595S, C603W are the most frequently reported ganciclovir resistance-associated substitutions. Viruses containing mutations in the UL97 gene are resistant to ganciclovir alone, whereas viruses with mutations in the UL54 gene are resistant to ganciclovir but may show cross-resistance to other antivirals that also target the viral polymerase.

Treatment of CMV retinitis:

Genotypic analysis of CMV in polymorphonuclear leucocytes (PMNL) isolates from 148 patients with CMV retinitis enrolled in one clinical study has shown that 2.2 %, 6.5 %, 12.8 %, and 15.3 % contain UL97 mutations after 3, 6, 12 and 18 months, respectively, of Valganciclovir hydrochloride treatment.

Prevention of CMV disease in transplantation:

Active comparator study

Resistance was studied by genotypic analysis of CMV in PMNL samples collected i) on Day 100 (end of study drug prophylaxis) and ii) in cases of suspected CMV disease up to 6 months after transplantation. From the 245 patients randomised to receive Valganciclovir hydrochloride, 198 Day 100 samples were available for testing and no ganciclovir resistance mutations were observed. This compares with 2 ganciclovir resistance mutations detected in the 103 samples tested (1.9 %) for patients in the oral ganciclovir comparator arm.

Of the 245 patients randomised to receive Valganciclovir hydrochloride, samples from 50 patients with suspected CMV disease were tested and no resistance mutations were observed. Of the 127 patients randomised on the ganciclovir comparator arm, samples from 29 patients with suspected CMV disease were tested, from which two resistance mutations were observed, giving an incidence of resistance of 6.9 %.

Extending prophylaxis study from 100 to 200 days post-transplant

Genotypic analysis was performed on the UL54 and UL97 genes derived from virus extracted from 72 patients who met the resistance analysis criteria: patients who experienced a positive viral load (>600 copies/ml) at the end of prophylaxis and/or patients who had confirmed CMV disease up to 12 months (52 weeks) post-transplant. Three patients in each treatment group had a known ganciclovir resistance mutation.

Paediatric population

Treatment of CMV retinitis:

Prevention of CMV disease in transplantation

A phase II pharmacokinetic and safety study in paediatric solid organ transplant recipients (aged 4 months to 16 years, n = 63) receiving Valganciclovir hydrochloride once daily for up to 100 days according to the paediatric dosing algorithm produced exposures similar to that in adults. Follow up after treatment was 12 weeks. CMV D/R serology status at baseline was D+/R- in 40%, D+/R+ in 38%, D-/R+ in 19% and D-/R- in 3% of the cases. Presence of CMV virus was reported in 7 patients. The observed adverse drug reactions were of similar nature as those in adults.

A phase IV tolerability study in paediatric kidney transplant recipients (aged 1 to 16 years, n=57) receiving Valganciclovir hydrochloride once daily for up to 200 days according to the dosing algorithm resulted in a low incidence of CMV. Follow up after treatment was 24 weeks. CMV D/R serology status at baseline was D+/R+ in 45%, D+/R- in 39%, D-/R+ in 7%, D-/R- in 7% and ND/R+ in 2% of the cases. CMV viremia was reported in 3 patients and a case of CMV syndrome was suspected in one patient but not confirmed by CMV PCR by the central laboratory. The observed adverse drug reactions were of similar nature to those in adults.

These data support the extrapolation of efficacy data from adults to children and provide posology recommendations for paediatric patients.

A phase I pharmacokinetic and safety study in heart transplant patients (aged 3 weeks to 125 days, n=14) who received a single daily dose of Valganciclovir hydrochloride according to the paediatric dosing algorithm on 2 consecutive days produced exposures similar to those in adults. Follow up after treatment was 7 days. The safety profile was consistent with other paediatric and adult studies, although patient numbers and Valganciclovir hydrochloride exposure were limited in this study.

Congenital CMV

The efficacy and safety of ganciclovir and/or Valganciclovir hydrochloride was studied in neonates and infants with congenital symptomatic CMV infection in two studies.

In the first study, the pharmacokinetics and safety of a single dose of Valganciclovir hydrochloride (dose range 14-16-20 mg/kg/dose) was studied in 24 neonates (aged 8 to 34 days) with symptomatic congenital CMV disease. The neonates received 6 weeks of antiviral treatment, whereas 19 of the 24 patients received up to 4 weeks of treatment with oral Valganciclovir hydrochloride, in the remaining 2 weeks they received i.v. ganciclovir. The 5 remaining patients received i.v. ganciclovir for the most time of the study period. In the second study the efficacy and safety of six weeks versus six months of Valganciclovir hydrochloride treatment was studied in 109 infants aged 2 to 30 days with symptomatic congenital CMV disease. All infants received oral Valganciclovir hydrochloride at a dose of 16 mg/kg twice daily for 6 weeks. After 6 weeks of treatment the infants were randomised 1:1 to continue treatment with Valganciclovir hydrochloride at the same dose or receive a matched placebo to complete 6 months of treatment.

This treatment indication is not currently recommended for Valganciclovir hydrochloride. The design of the studies and results obtained are too limited to allow appropriate efficacy and safety conclusions on Valganciclovir hydrochloride.

The pharmacokinetic properties of Valganciclovir hydrochloride have been evaluated in HIV- and CMV-seropositive patients, patients with AIDS and CMV retinitis and in solid organ transplant patients.

Absorption

Valganciclovir hydrochloride is a prodrug of ganciclovir. It is well absorbed from the gastrointestinal tract and rapidly and extensively metabolised in the intestinal wall and liver to ganciclovir. Systemic exposure to Valganciclovir hydrochloride is transient and low. The bioavailability of ganciclovir from oral dosing of Valganciclovir hydrochloride is approximately 60 % across all the patient populations studied and the resultant exposure to ganciclovir is similar to that after its intravenous administration (please see below). For comparison, the bioavailability of ganciclovir after administration of 1000 mg oral ganciclovir (as capsule) is 6-8%.

Valganciclovir hydrochloride in HIV positive, CMV positive patients:

Systemic exposure of HIV positive, CMV positive patients after twice daily administration of ganciclovir and Valganciclovir hydrochloride for one week is:

The efficacy of ganciclovir in increasing the time-to-progression of CMV retinitis has been shown to correlate with systemic exposure (AUC).

Valganciclovir hydrochloride in solid organ transplant patients:

Steady state systemic exposure of solid organ transplant patients to ganciclovir after daily oral administration of ganciclovir and Valganciclovir hydrochloride is:

The systemic exposure of ganciclovir to heart, kidney and liver transplant recipients was similar after oral administration of Valganciclovir hydrochloride according to the renal function dosing algorithm.

Food effect:

Dose proportionality with respect to ganciclovir AUC following administration of Valganciclovir hydrochloride in the dose range 450 to 2625 mg was demonstrated only under fed conditions. When Valganciclovir hydrochloride was given with food at the recommended dose of 900 mg, higher values were seen in both mean ganciclovir AUC (approximately 30 %) and mean ganciclovir C_max values (approximately 14 %) than in the fasting state. Also, the inter-individual variation in exposure of ganciclovir decreases when taking Valganciclovir hydrochloride with food. Valganciclovir hydrochloride has only been administered with food in clinical studies. Therefore, it is recommended that Valganciclovir hydrochloride be administered with food.

Distribution

Because of rapid conversion of Valganciclovir hydrochloride to ganciclovir, protein binding of Valganciclovir hydrochloride was not determined. Plasma protein binding of ganciclovir was 1 - 2 % over concentrations of 0.5 and 51 μg/ml. The steady state volume of distribution (V_d) of ganciclovir after intravenous administration was 0.680 ± 0.161 l/kg (n=114).

Biotransformation

Valganciclovir hydrochloride is rapidly and extensively metabolised to ganciclovir; no other metabolites have been detected. No metabolite of orally administered radiolabelled ganciclovir (1000 mg single dose) accounted for more than 1 - 2 % of the radioactivity recovered in the faeces or urine.

Elimination

Following dosing with Valganciclovir hydrochloride, renal excretion, as ganciclovir, by glomerular filtration and active tubular secretion is the major route of elimination of Valganciclovir hydrochloride. Renal clearance accounts for 81.5 % ± 22 % (n=70) of the systemic clearance of ganciclovir. Post-hoc Bayesian estimates for population mean apparent clearance of ganciclovir in patients with CrCl > 60 ml/min is 14.05 ± 4.13 l/h. In patients with renal impairment, the mean apparent clearance of ganciclovir is 8.46 ± 1.67 l/h (CrCl between 40 and 60 ml/min) and 7.00 ± 1.08 l/h (CrCl between 25 and 40 ml/min).The half-life of ganciclovir from Valganciclovir hydrochloride is 4.1 ± 0.9 hours in HIV- and CMV-seropositive patients.

Pharmacokinetics in special clinical situations

Patients with renal impairment

Decreasing renal function resulted in decreased clearance of ganciclovir from Valganciclovir hydrochloride with a corresponding increase in terminal half-life. Therefore, dosage adjustment is required for renally impaired patients.

Patients undergoing haemodialysis

For patients receiving haemodialysis dose recommendations for Valganciclovir hydrochloride tablets cannot be given. This is because an individual dose of Valganciclovir hydrochloride required for these patients is less than the 450 mg tablet strength. Thus, Valganciclovir hydrochloride film-coated tablets should not be used in these patients.

Patients with hepatic impairment

The safety and efficacy of Valganciclovir hydrochloride have not been studied in patients with hepatic impairment. Hepatic impairment should not affect the pharmacokinetics of ganciclovir since it is excreted renally and, therefore, no specific dose recommendation is made.

Patients with cystic fibrosis

In a phase I pharmacokinetic study in lung transplant recipients with or without cystic fibrosis (CF), 31 patients (16 CF/15 non-CF) received post-transplant prophylaxis with 900 mg/day Valganciclovir hydrochloride. The study indicated that cystic fibrosis had no statistically significant influence on the overall average systemic exposure to ganciclovir in lung transplant recipients. Ganciclovir exposure in lung transplant recipients was comparable to that shown to be efficacious in the prevention of CMV disease in other solid organ transplant recipients.

Paediatric population

In a phase II pharmacokinetic and safety study in paediatric solid organ transplant recipients (aged 4 months to 16 years, n = 63) Valganciclovir hydrochloride was given once daily for up to 100 days. Pharmacokinetic parameters were similar across organ type and age range and comparable with adults. Population pharmacokinetic modelling suggested that bioavailability was approximately 60%. Clearance was positively influenced by both body surface area and renal function.

In a phase I pharmacokinetic and safety study in paediatric heart transplant recipients (aged 3 weeks to 125 days, n = 14), Valganciclovir hydrochloride was given once daily for two study days. Population pharmacokinetics estimated that mean bioavailability was 64%.

A comparison of the results from these two studies and the pharmacokinetic results from the adult population shows that ranges of AUC_0-24h were very similar across all age groups, including adults. Mean values for AUC_0-24h and C_max were also similar across the paediatric age groups < 12 years old, although there was a trend of decreasing mean values for AUC_0-24h and C_max across the entire paediatric age range, which appeared to correlate with increasing age. This trend was more apparent for mean values of clearance and half-life (t_1/2); however this is to be expected as clearance is influenced by changes in weight, height and renal function associated with patient growth, as indicated by population pharmacokinetic modelling.

The following table summarises the model-estimated AUC_0-24h ranges for ganciclovir from these two studies, as well as mean and standard deviation values for C_max, t ½, CL and AUC_0-24h for the relevant paediatric age groups compared to adult data:

* Extracted from study report PV 16000

Ganciclovir pharmacokinetics following Valganciclovir hydrochloride administration were also evaluated in two studies in neonates and infants with symptomatic congenital CMV disease. In the first study 24 neonates aged 8 to 34 days received 6 mg/kg intravenous ganciclovir twice daily. Patients were then treated with oral Valganciclovir hydrochloride, where the dose of Valganciclovir hydrochloride powder for oral solution ranged from 14 mg/kg to 20 mg/kg twice daily; total treatment duration was 6 weeks. A dose of 16 mg/kg twice daily of Valganciclovir hydrochloride powder for oral solution provided comparable ganciclovir exposure as 6 mg/kg intravenous ganciclovir twice daily in neonates, and also achieved ganciclovir exposure similar to the effective adult 5 mg/kg intravenous dose.

In the second study, 109 neonates aged 2 to 30 days received 16 mg/kg Valganciclovir hydrochloride powder for oral solution twice daily for 6 weeks and subsequently 96 out of 109 enrolled patients were randomised to continue receiving Valganciclovir hydrochloride or placebo for 6 months. However, the mean AUC_0-12h was lower compared to the mean AUC_0-12h values from the first study. The following table shows the mean values of AUC, C_max, and t_½ including standard deviations compared with adult data:

GAN = Ganciclovir, i.v.

VAL = Valganciclovir hydrochloride, oral

These data are too limited to allow conclusions regarding efficacy or posology recommendations for paediatric patients with congenital CMV infection.

Valganciclovir hydrochloride is a pro-drug of ganciclovir and therefore effects observed with ganciclovir apply equally to Valganciclovir hydrochloride. Toxicity of Valganciclovir hydrochloride in pre-clinical safety studies was the same as that seen with ganciclovir and was induced at ganciclovir exposure levels comparable to, or lower than, those in humans given the induction dose.

These findings were gonadotoxicity (testicular cell loss) and nephrotoxicity (uraemia, cell degeneration), which were irreversible; myelotoxicity (anaemia, neutropenia, lymphocytopenia) and gastrointestinal toxicity (mucosal cell necrosis), which were reversible.

Further studies have shown ganciclovir to be mutagenic, carcinogenic, teratogenic, embryotoxic, aspermatogenic (i.e. impairs male fertility) and to suppress female fertility.

Not applicable.

Any unused medicinal product or waste material should be disposed of in accordance with local requirements.