Real-World Safety and Efficacy of Ombitasvir/Paritaprevir/Ritonavir/+Dasabuvir±Ribavirin (OBV/PTV/r/+DSV±RBV) Therapy in Recurrent Hepatitis C Virus (HCV) Genotype 1 Infection Post-Liver Transplant: AMBER-CEE Study

Abstract

Background

The introduction of direct-acting antivirals (DAAs) has considerably improved therapeutic outcomes for patients with chronic hepatitis C virus (HCV) infections. The AMBER-CEE study aimed to assess real-world efficacy and safety of ombitasvir/paritaprevir/ritonavir/+dasabuvir±ribavirin (OBV/PTV/r/+DSV±RBV) in the treatment of post-transplant recurrence of HCV infection.

Material/Methods

Liver transplant recipients with recurrent HCV genotype 1 infection, scheduled for OBV/PTV/r/+DSV±RBV according to therapeutic guidelines, were eligible. The primary efficacy endpoint was sustained virologic response (SVR) 12 weeks after the end of treatment (FU12). Clinical and laboratory adverse events (AEs) were recorded from baseline to FU12.

Results

A total of 35 patients were included: 91.4% genotype 1b-infected, 94.3% treatment-experienced, and 77.1% at fibrosis stage ≥F2. SVR12 was achieved by all patients (35/35, 100%) including one patient with genotype 1a, one patient with detectable HCV RNA at the end of treatment, two patients with a history of first-generation DAA therapy, and two patients who prematurely discontinued the regimen. AEs were experienced by 22 patients (62.9%) and were mostly mild. No death, graft loss, or acute graft rejections were reported during the therapy. On-treatment hepatic decompensation occurred in three patients (8.6%). Anemia was observed in 29 patients (83.9%), with 21 (60%) requiring RBV dose reduction or discontinuation.

Conclusions

OBV/PTV/r/+DSV±RBV has excellent efficacy in post-transplant recurrence of HCV genotype 1-infection treated under real-world conditions. Excellent virologic outcomes were observed irrespective of prior treatment history or the degree of fibrosis, and AEs were mostly mild and transient.

Background

Chronic hepatitis C virus (HCV) infection affects 130–150 million people worldwide and contributes to approximately 700,000 deaths each year (World Health Organization) [1]. If untreated, HCV infection leads to liver cirrhosis in up to 20% of patients and the development of hepatocellular carcinoma in 5–10% of patients [2]. HCV-related liver disease remains the leading indication for liver transplantation in the United States and Europe [3,4]. However, long-term survival in this population remains poor, with approximately 60% of patients dying or requiring re-transplantation within ten years of surgery [2].

Epidemiological data demonstrate almost universal recurrence of HCV infection in liver transplant recipients with detectable HCV RNA prior to surgery. The disease progression is significantly faster in this group of patients, with most developing chronic allograft hepatitis, and over 40% progressing to cirrhosis within ten years [5]. Liver transplant recipients with HCV-induced graft cirrhosis show more aggressive disease progression and are at considerably greater risk of hepatic decompensation compared to immunocompetent HCV-infected cirrhotics [5,6]. HCV-related complications markedly reduce patient survival and are the dominant cause of death in the post-liver transplant population [7].

Patients with recurrent HCV infection following liver transplantation have historically been difficult to treat. Therapy with pegylated interferon (PEG-IFN) and ribavirin (RBV) only provided sustained virologic response (SVR) in 18–43% of patients, and was limited by numerous side effects [8]. The addition of a first-generation direct-acting antiviral (DAA), boceprevir or telaprevir, improved efficacy and allowed virologic cure in little over half of the liver transplant recipients [9,10]. These regimens were, however, characterized by less favorable safety profiles and an increased risk of drug interactions, particularly in the setting of a concomitant immunosuppressive therapy.

Recently, novel, all-oral, interferon-free, anti-HCV regimens were introduced, containing two or more DAAs with different mechanisms of action and showing excellent virologic and safety outcomes across all HCV patient populations [11]. Phase 3 clinical trials and real-world experience of ombitasvir/paritaprevir/ritonavir/dasabuvir (OBV/PTV/r/+DSV) therapy with or without RBV demonstrated SVR rates of 90–100% in HCV genotype 1-infected non-transplant patients, irrespective of previous treatment history or cirrhosis status. Adverse events (AEs) reported by the investigators were mild and rarely led to treatment discontinuation or failure [12–14]. Similar results were observed in clinical trials carried out in liver transplant recipients, with SVR rates of as much as 96–100% and few treatment-limiting side effects [15]. However, real-world data in liver transplant recipients are scarce, and more research is needed to confirm these preliminary findings in clinical practice. To address this demand, the AMBER-CEE study was designed to evaluate the efficacy and safety of OBV/PTV/r/+DSV±RBV in patients with recurrent HCV infection following liver transplantation under real-world conditions.

Material and Methods

Study design

AMBER-CEE was an observational, open-label study initiated by the investigators and conducted in 11 hepatology and transplant centers in Central and Eastern Europe as part of a research project involving a cohort of pre- and post-liver transplantation patients. Data were collected between November 2014 and June 2015. At the time of enrollment, the regimen was awaiting regulatory approval for treatment of chronic HCV infection in the European Union and consent for experimental therapy was obtained from local ethics committees. Antiviral medication was provided by the manufacturer under a named patient program established to meet the therapeutic needs of individuals with advanced or rapidly progressing HCV-related liver disease. The study was conducted according to the Declaration of Helsinki (2000) as well as Declaration of Istanbul (2008), and followed the guidelines of Good Clinical Practice. Ethics committee approval was obtained from all participating centers. All patients were fully informed about the rationale for the study and provided written informed consent prior to enrolment.

Study population

Patients aged over 18 years, male or female, with chronic HCV genotype 1 infection, irrespective of antiviral treatment history or cirrhosis status, who experienced HCV recurrence following liver transplantation, were eligible for the study. Exclusion criteria were genotype other than 1, ongoing treatment with mTOR inhibitors, presence of cholestatic fibrosing hepatitis or post-transplant vascular complications (hepatic artery or portal vein thrombosis), history of unsuccessful treatment of biliary stricture, diagnosis of new or recurrent hepatocellular carcinoma (HCC) in the past 12 months, presence of neoplasm other than HCC that would require chemotherapy during antiviral treatment, advanced renal failure or hemodialysis, life expectancy of less than one year, pregnancy of the patient or partner (in case of male patients), and hepatitis B virus (HBV) or human immunodeficiency virus (HIV) coinfection. All patients were enrolled for OBV/PTV/r/+DSV±RBV treatment according to the manufacturer’s recommendations. To reflect real-world clinical practice, the decision to initiate antiviral therapy was left to the discretion of the physician.

Medication and follow-up

The patients received co-formulated OBV/PTV/r at (25 mg/150 mg/100 mg once daily) and DSV (500 mg daily, divided in two doses). The addition of RBV (600–1200 mg) was left to the discretion of the treating physician. Initial daily dose of RBV was weight-based, however, individuals with significant laboratory abnormalities at baseline required additional dose adjustments. In patients who developed severe on-treatment RBV-related AEs, the dose was modified accordingly or discontinued. Dosing of calcineurin inhibitors (either tacrolimus or cyclosporine) was based on manufacturer’s recommendations and subsequently adjusted according to plasma concentrations, as described by Badri et al. [16]. Decisions regarding adjustment or discontinuation of other pharmaceuticals were made in line with guidelines provided by AbbVie in a drug-to-drug interaction tool for OBV/PTV/r/DSV. The expected duration of treatment was 24 weeks; however, therapy was shortened to 12 weeks in two patients at the investigator’s discretion. Assessments were performed at baseline, one and four weeks after the initiation of treatment, at the end of treatment (EOT), and 12 weeks after EOT (FU12). Additional visits were scheduled when necessary. Baseline data included gender, age, body mass index (BMI), degree of fibrosis, antiviral treatment history, time from liver transplantation, and current medication, including immunosuppressive therapy. Liver fibrosis was assessed not more than six months before enrollment using liver biopsy or non-invasive methods (transient elastography). Laboratory data included viral load, liver function tests (bilirubin, alanine transaminase (AL), alkaline phosphatase (ALP), and albumin), hemoglobin (Hgb) concentration, and serum creatinine. Glomerular filtration rate (GFR) was calculated using the Modification of Diet in Renal Disease (MDRD) or the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation. IL28B genotype was not determined. Testing for resistance-associated variants (RAVs) was not performed pre-treatment.

Efficacy and safety assessment

The primary efficacy endpoint was the achievement of SVR (HCV RNA undetectable or below detection threshold) at FU12. Quantitative PCR assays were used to determine HCV RNA levels (COBAS TaqMan HCV v.2.0, Roche; COBAS AmpliPrep HCV, Roche; m2000 RealTime System, Abbott). The detection threshold was 25 IU/mL or below and varied across study centers (15 IU/mL in 80% of patients). Secondary endpoints were to evaluate virologic response at four weeks and EOT. Quantitative PCR assays were used to measure HCV replication. Safety endpoints were clinical and laboratory AEs recorded from baseline to FU12. All analyses were performed on an intention to treat basis.

Statistical analysis

All data were presented as mean (range), unless indicated otherwise. Lilliefors and Kolomogorov-Smirnov tests were applied to assess for normality. Repeated measures analysis of variance (ANOVA) and ANOVA for dependent variables were used to examine differences between groups. Correlations between variables were tested with the Pearson or Spearman coefficient, depending on the distribution type. A p-value of 0.05 was considered statistically significant. All computations were performed using the MySQL relational database and Eclipse IDE for Java Developers (The Eclipse Foundation).

Results

Study population

A total of 35 patients were included in the study; all were HCV genotype 1-infected (91.4% genotype 1b), with the recurrence of HCV following liver transplantation. Mean time from surgery was 35.5 months, and one patient (2.9%) had a history of re-transplantation. RBV was administered in all but one patient and the dose ranged from 600 to 1200 mg daily. All study participants received either tacrolimus (71.4%) or cyclosporine (22.9%) as a primary immunosuppressant. Other immunosuppressive medications were prednisone (40.0%), mycophenolate mofetil (48.6%), and azathioprine (2.9%). In two patients, data regarding immunosuppressive therapy were missing. Liver biopsy was performed in 26 patients (75.8%) to assess the degree of fibrosis; the remaining proportion had transient elastography. Cirrhosis was present in seven patients (20.0%); all cases were Child-Pugh class A. One patient with METAVIR score F3 was Child-Pugh class B at the time of enrolment. Three patients (8.6%) had a history of HCC prior to liver transplantation. Thirty-three patients (94.3%) were treatment-experienced and failed previous PEG-IFN-based regimens; 18 of them (51.4%) were null-responders. Two patients (5.7%) had previously been treated with a combination of telaprevir, PEG-IFN, and RBV (triple therapy). Baseline clinical and laboratory characteristics of the study population are presented in Table 1.

Table 1.

Baseline characteristics of the study population.

	N=35
Age, years	56 (34–73)
Gender, n (%)
Male	18 (51.4)
BMI, kg/m2	26.2 (19.5–33)
HCV genotype, n (%)
1a	1 (2.9)
1b	32 (91.4)
1, unknown subtype	2 (5.7)
Treatment history, n (%)
Naïve	1 (2.9)
Partial responder	2 (5.7)
Non-responder	31 (88.6)
Null-responder	18 (51.4)
Unknown	1 (2.9)
Fibrosis stage, n (%)
F0	0 (0.0)
F1	8 (22.9)
F2	13 (37.1)
F3	7 (20.0)
F4 (cirrhosis)	7 (20.0)
Unknown	4 (1.9)
Child-Pugh class in patients with liver cirrhosis
A5	2 (5.7)
A6	5 (14.3)
Time from liver transplantation, months	35.5 (1–102)
Primary immunosuppressive medication, n (%)
Tacrolimus	25 (71.4)
Cyclosporine	8 (22.9)
Other immunosuppressive medication, n (%)
Prednisone	14 (40.0)
Mycophenolate mofetil	17 (48.6)
Azathioprine	1 (2.9)
History of HCC prior to liver transplantation, n (%)	3 (8.6)
HCV RNA level, ×106 IU/mL	3.63 (0.0016–5.5)
Bilirubin, mg/dL	1.41 (0.36–8.22)
ALT, IU/L	104.7 (9–687)
Hgb, g/dL	13.4 (9.3–17.5)
Albumin, g/dL	3.94 (2.79–5.20)
Creatinine, mg/dL	1.13 (0.67–2.00)
GFR, mL/min	84.0 (29.2–164.0)

All data are presented as mean (range), unless indicated otherwise. ALT – alanine transaminase; BMI – body mass index; GFR – glomerular filtration rate; HCC – hepatocellular carcinoma; HCV – hepatitis C virus; HCV RNA – HCV ribonucleic acid; Hgb – hemoglobin.

Efficacy

At four weeks, HCV RNA was undetectable in 15 of the 28 patients (42.9%) for whom viral load data were available. All of them had baseline HCV RNA below 2×10⁶ IU/mL (mean 568.7×10³ IU/mL, range 1.60×10³–1.91×10⁶ IU/mL) and only one was cirrhotic (METAVIR score F4). Thirty-five patients (100.0%) had undetectable HCV RNA at FU12, including one patient with genotype 1a, one patient with detectable HCV RNA at EOT, two patients with a history of treatment with a first-generation DAA (telaprevir), and two patients who prematurely discontinued the study medication. All patients with on-treatment hepatic decompensation had negative HCV RNA at FU12. The only patient who achieved SVR despite detectable HCV RNA at EOT (40 IU/mL) was male, genotype 1b-infected, non-cirrhotic (METAVIR score F2), with low baseline viremia (0.36×10⁶ IU/mL), had received RBV at an initial daily dose of 800 mg (later reduced to 600 mg), and had completed 24 weeks of treatment. Virologic response rates at given time points (four weeks, EOT, and FU12) are shown in Figure 1.

Figure 1.

Virologic response expressed as a proportion of patients with undetectable HCV RNA at given time points (intention-to-treat analysis). * Efficacy data available for 28 patients. EOT – end of treatment; FU12 – 12 weeks after the end of treatment.

Safety

AEs occurred in 22 patients (62.9%) and were generally mild and transient. Most frequently, asthenia (20.0%), headaches (14.3%), and diarrhea (8.6%) were reported; other AEs included peripheral edema, insomnia, fatigue, and heart palpitations. No death, graft loss, or acute graft rejection episodes were observed during the study period. Twenty-nine patients (83.9%) experienced a decrease in Hgb, with grade 2 anemia (Hgb 8–10 g/dL) recorded in 13 patients (37.1%); the lowest Hgb levels were observed at four weeks. One patient (2.9%) required blood transfusion twice; none received erythropoietin. In 10 patients (28.6%), RBV was discontinued and 11 (31.4%) required dose reduction due to anemia. These changes in the RBV treatment were introduced after 1–12 weeks, faster and more frequently in patients with advanced fibrosis and on higher baseline RBV dosage.

There was no possible association between hyperbilirubinemia and cholestatic fibrosing hepatitis as this was one of the exclusion criteria. The only patient treated with an RBV-free regimen showed stable Hgb levels across the study. Elevated serum total bilirubin was observed in 20 patients (57.1%), including four patients with grade 3 hyperbilirubinemia (serum bilirubin levels 3–10 times greater than the upper limit of normal). One patient showed a very high serum total bilirubin level (10.99 mg/dL) at the end of the antiviral therapy; however, their levels did not reach the criteria for a grade 4 elevation (i.e., 10 times the upper limit of normal of 1.2 mg/dL). Highest levels of serum bilirubin were recorded between week one and four weeks. A decrease in bilirubin was spontaneous or followed RBV dose reduction.

Eight patients (22.9%), all of them liver cirrhotic, had transient worsening of renal function with lowest GFR values reported between one and four weeks after the initiation of treatment. After this period, GFR stabilized and returned to pre-treatment values at FU12. No significant serum transaminase elevations were observed. Changes in laboratory values during treatment are presented in Table 2. Three patients (8.6%), all with a previous history of ascites or hepatic encephalopathy, developed hepatic decompensation. Of these, two continued therapy and improved following pharmacological intervention. None required re-transplantation during the follow-up. The characteristics of this subgroup are presented in Table 3.

Table 2.

Changes in laboratory values during treatment.

	Baseline	1 week	4 weeks	EOT	FU12
Bilirubin, mg/dL	1.41 (0.36–8.22)	2.04 (0.79–7.08)	1.53 (0.41–3.93)	1.30 (0.3–10.99)	0.81 (0.35–4.37)
ALT, IU/mL	104.66 (9–687)	41.18 (9–115)	27.00 (8–114)	21.45 (6–66)	19.61 (7–43)
ALP, IU/mL	126.22 (32–370)	101.11 (19–185)	87.92 (18–183)	96.25 (18–205)	74.93 (18–149)
Albumin, g/dL	3.94 (2.79–5.20)	4.10 (2.85–5.10)	4.15 (2.61–5.10)	4.20 (3.20–5.30)	4.10 (3.50–4.80)
Hgb, g/dL	13.44 (9.3–17.5)	12.97 (9.8–17.2)	11.33 (8.1–16.4)	11.85 (9.0–16.3)	13.04 (8.2–16.5)
Creatinine, mg/dL	1.13 (0.67–2.00)	1.31 (0.70–2.10)	1.24 (0.76–2.20)	1.17 (0.60–2.02)	1.03 (0.69–1.75)
GFR, mL/min	84.0 (29.1–164.0)	70.7 (27.9–117.0)	75.5 (34.4–144.7)	78.7 (43.9–144.4)	89.8 (49.7–168.3)

All data are presented as mean (range). ALT – alanine transaminase; ALP – alkaline phosphatase; EOT – end of treatment; FU12 – follow-up 12 weeks after EOT; GFR – glomerular filtration rate; Hgb – hemoglobin.

Table 3.

Characteristics of patients who developed on-treatment hepatic decompensation (n=3).

	Patient 1	Patient 2	Patient 3
Age, years	56	60	64
Gender	Female	Female	Male
Genotype	1b	1b	1b
HE history	+	−	+
Ascites history	+	+	+
Albumin, g/dL	3.12	3.90	3.60
MELD score, points	17	12	12
Child-Pugh score, points	8	6	6
Treatment discontinued	No	No	Yes, at 23 weeks
Decompensation possibly related to therapy	+/−	+/−	+/−
Additional information	Decompensation at 4 weeks (encephalopathy)	Decompensation at 2 weeks (↑ bilirubin, ascites, hepatorenal syndrome) possibly due to tacrolimus toxicity	Decompensation at 1 week (ascites, peripheral edema)

HE – hepatic encephalopathy; MELD – Model of End-Stage Liver Disease.

Two patients (5.7%) prematurely discontinued antiviral therapy. In one case (2.9%), the treatment was terminated at 23 weeks due to hepatic decompensation; in another, the decision to stop the medication was made by the patient at 20 weeks because of side effects. A summary of AEs is shown in Table 4.

Table 4.

Summary of adverse events.

	N=35 (%)
Any AEs, n (%)	22 (62.9)
Serious AEs	6 (17.1)
Hepatic decompensation	3 (8.6)
Anemia	1 (2.9)
Diarrhea	1 (2.9)
Renal failure	1 (2.9)
AEs leading to treatment discontinuation	2 (5.7)
Most common AEs*
Asthenia	7 (20.0)
Headache	5 (14.3)
Diarrhea	3 (8.6)
Peripheral edema	2 (5.7)
Insomnia	2 (5.7)
Fatigue	2 (5.7)
Heart palpitations	2 (5.7)
Laboratory abnormalities
Hyperbilirubinemia	20 (57.1)
Grade 3 (3–10× ULN)	4 (11.4)
Grade 4 (>10× ULN)	0 (0.0)
Anemia	29 (83.9)
Grade 2 (8–10 g/dL)	13 (37.1)
Grade 3 or 4 (<8 g/dL)	0 (0.0)
Transient worsening of renal function	8 (22.9)

^*Reported in more than 5% of patients.

AEs – adverse events; ULN – upper limit of normal.

Calcineurin inhibitor concentrations and dosing

Mean serum concentrations of calcineurin inhibitors increased from baseline and were markedly elevated at four weeks, especially in tacrolimus-treated patients (drug levels almost doubled in this group). At EOT, tacrolimus and cyclosporine concentrations were comparable with baseline values. Changes in the mean calcineurin inhibitor serum concentrations are shown in Table 5. Dosing was modified accordingly and patients received an average of 0.5 mg tacrolimus every 7–10 days, or 25 mg of cyclosporine (range 20–100 mg) daily.

Table 5.

Changes in the mean serum concentrations of calcineurin inhibitors (ng/mL).

	Baseline	4 weeks	EOT
Cyclosporine	80.93 (51.9–130.6)	117.31 (25.0–186.8)	106.78 (25.0–190.7)
Tacrolimus	5.34 (2.9–14.5)	11.49 (3.8–21.9)	5.45 (2.4–7.7)

All data are presented as mean (range). EOT – end of treatment.

Discussion

The results of our study demonstrate excellent efficacy and safety of OBV/PTV/r/+DSV±RBV in patients with recurrent HCV infection following liver transplantation treated under real-world conditions. SVR was achieved by all patients, irrespective of cirrhosis status or previous treatment history. Our results are consistent with previous clinical trial outcomes showing excellent virologic response of DAAs in these patients. In particular, positive results were observed in the Phase 2 SOLAR-I study involving 118 liver transplant recipients with cirrhosis resulting from recurrent HCV infection (most were genotype 1a with a history of virologic failure) who received ledipasvir/sofosbuvir (SOF/LDV)+RBV for 12 or 24 weeks: SVR was achieved by 96% of individuals with Child-Pugh class A in this study, irrespective of the treatment duration, and by 85% and 88% of individuals with Child-Pugh class B treated for 12 or 24 weeks, respectively [17]. While poorer results were observed in Child-Pugh C patients (SVR was achieved by only 60% in the 12-week arm versus 75% in the 24-week arm), the relatively small sample size may have influenced the results [17]. Despite the positive clinical trial outcomes, few studies have provided real-world data regarding patients after liver transplantation, especially those with advanced graft failure. Therefore, to the best of our knowledge, the current study represents one of the first real-world studies performed in this population to date. The results of our study were presented at International Liver Transplantation Society Conference held in Seoul in May 2016 [18].

Recently, Ciesek et al. [19] examined 30 patients with recurrent HCV infection after liver transplantation treated with SOF/LDV +/− RBV in a real-world setting. Patients had a mean baseline liver tissue stiffness assessed by Fibroscan of 9.9 kPa. Most patients (25/30) were treated with RBV. Although RBV was discontinued in 15 cases due to anemia, this did not affect the positive virologic response and SVR was achieved in 29/30 (96.67%) patients treated with RBV for 12 (n=4) or 24 (n=25) weeks [19]. Moreover, in a previous phase 2, single-arm study evaluating efficacy and safety of OBV/PTV/r/+DSV±RBV in a cohort of 34 post-liver transplant patients with recurrent HCV infection, all except one achieved SVR12 and SVR24. However, only individuals with no or mild fibrosis were included in the observation (METAVIR score <F2), which is the population known to be easier to treat [15]. Similarly, a high rate of virologic response (SVR of 96% irrespective of the duration of treatment, or previous treatment history) was observed in a cohort of 204 liver transplant recipients (most with a METAVIR score <F2) receiving SOF/LDV [20]. In our study, almost 80% of patients had a METAVIR fibrosis score of F2 or greater and 20% were cirrhotic (METAVIR score F4). The majority of our patients failed PEG-IFN-based double or triple therapies, and more than half were null-responders. Despite these unfavorable factors, the regimen proved efficacious and provided virologic cure in all subjects.

So far, the available real-world data seems to remain limited to similar reports for OBV/PTV/r+DSV±RBV. In a multicenter Israeli study, an SVR12 rate of 86% (19/22) was achieved in post-liver transplant (mostly cirrhotic), HCV genotype 1-infected patients with advanced fibrosis treated with OBV/PTV/r/+DSV±RBV [21]. In all cases of therapeutic failure, treatment was discontinued prematurely due to side effects (two patients developed ascites, and in one patient significant elevation of the liver enzymes was recorded). Interestingly, the fourth patient who failed to complete the regimen, owing to severe weakness at 21 weeks, cleared HCV RNA at FU12 [21]. Only one patient (2.9%) in our study was HCV RNA-positive at EOT but had undetectable viremia at FU12. Similar observations were made in the real-world AMBER study conducted in a group of HCV genotype 1- and 4-infected individuals. Of the 202 patients who completed therapy with OBV/PTV/r/±DSV±RBV, all but one achieved SVR12, including two patients with detectable HCV RNA at EOT. Interestingly, six out of seven patients who prematurely discontinued the regimen owing to side effects cleared HCV RNA during the follow-up [13]. Likewise, the only AMBER-CEE participant in our study who failed to complete the treatment also cleared HCV RNA.

The safety profile of OBV/PTV/r/+DSV±RBV therapy was good and consistent with that described in clinical trials [13]. AEs experienced by our patients were generally mild and manageable, with asthenia, headache, and diarrhea being the most commonly reported. Hepatic decompensation was observed in three patients, all with a previous history of hepatic encephalopathy or ascites. At the time of enrollment, no clear-cut data regarding the risk of OBV/PTV/r/+DSV±RBV use in patients with decompensated liver cirrhosis were available. Although the impact of the antiviral therapy on the development of encephalopathy or ascites is hard to determine, the role of medication cannot be ruled out, especially given the relatively short time from the initiation of treatment to the onset of hepatic decompensation.

A decrease in Hgb levels was observed in 82.9% of patients, but grade 3 or 4 anemia was not reported. The only patient who received RBV-free therapy had stable Hgb concentrations throughout the study. In the remaining individuals, anemia was effectively managed with RBV dose reduction or discontinuation. The effect of RBV on red blood cell survival and Hgb levels has been extensively described in the literature [22]. In the pre-DAAs era, RBV dose reduction affected therapeutic outcomes and increased the risk of virologic failure. In light of the existing evidence, however, this seems not to be the case with all-oral, interferon-free therapies. Indeed, as described by Globke et al. [23], all 29 liver transplant patients with HCV recurrence treated with SOF/LDV but without RBV for 12 weeks achieved SVR. Although 10 of the 35 patients included in AMBER-CEE study discontinued RBV due to anemia, and 11 required dose reductions, the SVR12 rate was 100%. In the study by Globke et al. [23], liver transplant patients with fibrosis stages 0–2 treated with SOF/LDV for 12 weeks and without RBV experienced fewer AEs than those with advanced fibrosis (≥F3) or than those treated with additional RBV or with prolonged SOF/LDV therapy for 24 weeks (p<0.001). In most cases, patients with fibrosis stages ≥F3 that were additionally treated with RBV had to have their RBV dose reduced (n=11, 55%) and then stopped (n=8, 40%) due to AEs; however, these patients still achieved SVR. Unfortunately, the small number of patients included in the study by Globke et al. [23] did not allow for a comprehensive final summary. Given the high potential for AEs, more research is needed to evaluate the necessity of RBV use in special patient populations treated with new anti-HCV regimens.

Diminished GFRs were observed during treatment, especially in cirrhotic individuals. The values were lowest between one and four weeks and correlated with an increase in calcineurin inhibitor concentrations. The increase in tacrolimus exposure in the liver transplant recipients treated with OBV/PTV/r/+DSV±RBV was greater than that of cyclosporine, which is consistent with clinical data from healthy volunteers [16]. The impairment of renal function was transient and probably associated with calcineurin inhibitor toxicity. GFRs stabilized between four weeks and EOT, and all patients returned to pre-treatment values within a 12-week follow-up. Dosing of calcineurin inhibitors was modified according to serum concentrations. No episodes of graft loss or rejection were observed during treatment. One tacrolimus-treated patient did not return to normal dose following successful antiviral therapy. Due to subsequent deterioration of the liver function, acute rejection was suspected. The patient improved after the dose of immunosuppressive medication was increased, which supported the diagnosis of rejection. Graft biopsy was not performed, as there were no indications from clinical or biochemical assessments.

Fluctuations in the immunosuppressive drug levels (resulting from deliberate dose reduction or other factors) pose serious threat to both patient and graft survival. In a theoretical model, an improvement in hepatocyte function associated with HCV RNA clearance may lead to enhanced drug metabolism and decreased serum concentrations of immunosuppressive agents. In the SOF/LDV trial by Kwok et al. [20], the majority of patients required calcineurin inhibitor dose increase during or after the antiviral treatment (72% and 77%, respectively). In our study, however, the opposite effect of antiviral medication was observed. This is likely attributed to a more complex interaction profile of OBV/PTV/r/+DSV that results in an inhibited elimination and reduced clearance of immunosuppressive medication, which outweighs the restorative effect of anti-HCV treatment on hepatic function.

Last but not least, as with all new pharmaceuticals, despite extensive pre-registration testing and post-marketing surveillance, the possible delayed consequences of therapy remain unknown. This can, in part, be attributed to the underrepresentation of certain patient populations in clinical trials. Most recently, the use of DAAs in HCV patients previously treated for HCC was postulated to be associated with an increased rate of HCC recurrence, despite virologic success and HCV-RNA clearance. Abrupt resolution of the inflammatory state that accompanies chronic HCV infection has been proposed to be one of the mechanisms underlying disruption of immune surveillance and promoting cancer development [24,25]. In a study by Reig et al. [24], radiologic tumor recurrence was reported in 16/58 patients (27.6%) at a median time of 3.5 months after the initiation of antiviral therapy; however, these findings were not replicated in a larger, multi-cohort study [26]. At the time of writing, HCC recurrence had not been reported in any of the three post-liver transplant patients with a history of HCC included in our observation.

Our study was subject to limitations. It was conducted in a relatively small sample of mostly genotype 1b-infected patients, and therefore, its results should be extrapolated to other post-liver transplant populations with caution.

Conclusions

In conclusion, novel all-oral anti-HCV therapies show promising potential for providing virologic cure and increased survival in liver-transplant recipients with recurrent HCV infection. OBV/PTV/r/+DSV±RBV proved efficacious and safe in the treatment of HCV genotype 1 infection in a difficult-to-treat population of immunosuppressed patients with a history of liver transplantation, including patients with advanced fibrosis and previous therapeutic failure. The use of the regimen in post-liver transplant individuals requires careful monitoring of calcineurin inhibitor concentrations with doses adjusted accordingly, especially at the beginning of treatment. This, however, can be achieved by close cooperation and commitment of experienced physicians and self-disciplined patients, making OBV/PTV/r/+DSV±RBV a therapeutic alternative on par with other novel anti-HCV therapies, especially for patients with advanced renal failure.

Abbreviations

AEs

adverse events

DAAs

direct acting antivirals

DSV

dasabuvir

HCV

hepatitis C virus

OBV

ombitasvir

PTV

paritaprevir

PEG-IFN

pegylated interferon

r

ritonavir

RAV

resistance-associated variants

RBV

ribavirin

SVR

sustained virologic response