Safety and Efficacy of Once-Daily Prolonged-Release Tacrolimus in Living Donor Liver Transplantation: An Open-Label, Prospective, Single-Arm, Phase 4 Study

Background

The liver is an essential organ for maintaining life, and due to its complex and diverse functions, no machine developed thus far can fully replace it. Thus, the only possible treatment for end-stage liver disease, including liver cirrhosis and hepatocellular carcinoma, or acute liver failure caused by fulminant hepatitis or acetaminophen overdose is liver transplantation (LT) from healthy living donors or (unhealthy) deceased donors.

Although the liver is not as antigenic as other organs, such as the kidney, lung, heart, and bowel, assessment and response to the rejection of transplanted liver grafts are important aspects of patient care. Immunosuppressive regimens based on steroids and tacrolimus (Tac) or combination therapy with cyclosporine are generally used in the early phase of LT, and secondary immunosuppressants (e.g., mycophenolate mofetil) may be added.

Meanwhile, Tac – also known as FK-506 or fujimycin – is a 23-membered macrolide lactone that inhibits the development and proliferation of T cells; it was first discovered in 1987 from Japanese soil specimens containing Streptomyces tsukubaensis [1,2]. Twice-daily Tac (Bid-Tac), which is commonly used in modern LT, may lead to nonadherence among patients, which in turn serves as a risk factor for rejection and graft loss [3–5]. In an effort to increase adherence to immunosuppressive therapy in LT patients, once-daily prolonged-release Tac (OD-Tac) was first introduced in Europe in 2007. OD-Tac has been reported to improve adherence [6–8], and the low inter- and intra-individual variability in exposure to OD-Tac has been associated with an increase of graft and patient survival [8–10].

Based on these superior benefits of adherence and low variability compared to Bid-Tac, late conversion from Bid-Tac to OD-Tac has been reported multiple times to be safe and feasible generally after 6 months of LT in patients with stabilized liver functions [11–18]. However, there is little data on the efficacy and safety of early conversion from Bid-Tac to OD-Tac in living donor liver transplantation patients within 6 months of LT. In this context, the present study aimed to thoroughly assess the safety and efficacy of conversion from Bid-Tac to OD-Tac at 10–14 weeks after LDLT.

Material and Methods

PATIENTS AND STUDY DESIGN:

This clinical trial was an open-label, prospective, single-arm, phase 4 study. Adult patients aged 20 years or older who underwent LDLT in our institute between November 2015 and October 2016 and provided informed consents were screened. Of these patients, those in a good general condition with stable liver functions were enrolled in this clinical trial. The details of the inclusion and exclusion criteria are described in Supplementary Table 1.

The participants of this study underwent a conversion from reference Bid-Tac (Prograf®, Astellas Pharma, Inc., Seoul, Korea) to OD-Tac (Advagraf®, Astellas Pharma Inc., Seoul, Korea) with a daily dosage ratio of 1: 1 at 10–14 weeks after LDLT. Tac was administered only once a day in the morning. The serum trough level of Tac was measured at each outpatient visit, and Tac dosage was adjusted to maintain a trough level of 5–8 ng/ml for the first 3 months (months 0–3) and below 5 ng/ml for the subsequent 3 months (months 3–6) after Tac conversion. In all cases, a right lobe of a donor liver was used [19–21]. This study was approved by our Institutional Review Board (NCC2015-0020) and was registered at ClinicalTrials.gov (NCT03423225).

IMMUNOSUPPRESSION:

For induction therapy, 20 mg of basiliximab is administered on the operation day and post-operative day 4. Immunosuppressive regimens are a combination of Tac, mycophenolate mofetil, and corticosteroids after high-dose steroid administration during the operation. After LT, initial therapeutic target levels of Tac were 8–12 ng/ml during the first and the second week and thereafter 8–10 ng/mL during the first 3 months. After that, the tacrolimus trough level is adjusted to 5–6 ng/mL for 3–6 months and <5 ng/mL thereafter. Mycophenolate mofetil was started with a dose of 1.5 g/day. Corticosteroid was reduced to interruption for 6 months after LDLT.

FOLLOW-UP AND SURVEILLANCE:

The participants enrolled in this study underwent a total of 7 rounds of tests, 1 at each of the following time points: screening, baseline, weeks 2, 4, 8, 16, and 24. Test categories included serum Tac trough level, creatinine, estimated glomerular filtration rate (eGFR), bilirubin, aspartate transaminase (AST), alanine transaminase (ALT), glucose, cholesterol, high-density lipoproteins (HDL), low-density lipoproteins (LDL), and triglycerides (TG). Adherence and adverse events were checked at every outpatient visit.

STATISTICAL ANALYSIS:

The results are presented as mean ± standard deviation or median (interquartile range) for continuous variables and percentage for categorical variables. Paired continuous data were analyzed with a Wilcoxon signed rank test. McNemar’s test was used to compare paired proportions. A P value <0.05 was considered statistically significant. All calculations were made using the SPSS 24.0 statistical software package (IBM Corporation, Armonk, NY, USA).

Results

STUDY POPULATION AND BASELINE CHARACTERISTICS:

A total of 32 patients were screened. One patient was excluded for having a history of acute rejection, resulting in a total of 31 patients in the final sample. Twenty-four of these patients completed the clinical trial, with 7 dropouts. Reasons for study withdrawal were an adverse event (n=1, moderate melena) and consent withdrawals (n=6) (Figure 1).

The mean age was 53.7±8.0 years. A total of 77.4% (n=24) of the patients were male, while 22.6% (n=7) were female. Hepatocellular carcinoma was the most frequent primary reason for LT (71.0%, n=22). The mean body weight was 62.0±14.6 kg, while mean height was 166.5±8.9 cm. There were 18 patients with hepatitis B virus infection (58.1%), 1 patient with hepatitis C virus infection (3.2%), and 2 patients with cytomegalovirus infection (6.5%). Six patients had diabetes mellitus (19.4%), while 5 patients had hypertension (16.1%). The mean OD-Tac exposure period was 152.4±50.6 days. The median number of weeks from LT to Tac conversion was 12.3 weeks (range, 10.3–13.8). Table 1 shows the baseline characteristics of the 31 patients enrolled in this clinical trial.

ADHERENCE AND TAC TROUGH LEVEL:

Adherence was 100% at all time points: at weeks 2, 4, 8, 16, and 24 after Tac conversion from Bid-Tac to OD-Tac. The mean period for OD-Tac exposure was 152.4±50.6 days. The daily dosage for OD-Tac was 4.9±1.9 mg. Tac trough level significantly differed at weeks 2, 4, 8, 16, and 24 from that prior to conversion (Figure 2A, all P<0.001). Tac dosage significantly differed at week 2 after conversion from that prior to conversion (Figure 2B, P=0.011).

EFFICACY AND SAFETY:

There were no cases of acute rejection until study completion at week 24 after Tac conversion from Bid-Tac to OD-Tac. Furthermore, there were no cases of graft loss or patient death during the entire study period.

Nineteen cases of adverse events occurred in 11 out of 31 patients (35.5%). Of them, 18 were mild adverse events and 1 was a moderate adverse event, with no severe adverse events. The most common adverse event was alopecia, which affected 3 patients (9.7%), followed by pruritus (n=2, 6.5%). Melena, a moderate adverse event, affected 1 patient (3.2%), and this patient was withdrawn from the study. One patient had jaundice and LFT abnormality due to biliary stricture (Table 2).

After conversion from Bid-Tac to OD-Tac, there were no changes in renal functions, such as creatinine and eGFR (Figure 3A, 3B). Furthermore, serum bilirubin, AST, ALT, and glucose changes were also not observed during the follow-up period (Figure 3C–3F). Tac conversion lipid profile, such as serum cholesterol, HDL, LDL, and TG, also did not significantly differ from pre-conversion parameters in most cases (Figure 4A–4D).

Discussion

Adherence to immunosuppressants after LT is a decisive factor in preventing the risk of rejection and graft loss. It was reported that about 15–40% of adult patients showed nonadherence with immunosuppressant regimens [5]. Nonadherence to immunosuppressant after LT may induce rejection and graft loss, ultimately having adverse effects on long-term patient survival [3–5]. In our study, adherence was 100% at all outpatient visits at weeks 2, 4, 8, 16, and 24 after the conversion from Bid-Tac to OD-Tac. These results are in line with previous findings [7,15], again confirming the superiority of OD-Tac in terms of promoting adherence.

In addition to the benefits of adherence to immunosuppressants, OD-Tac has been reported to be superior to Bid-Tac in terms of inter-individual variability and intra-individual variability [9,10]. Moreover, a recent study suggested that OD-Tac is intimately related to the improvement of graft and patient survival [8]. Based on this superiority, there were some successful cases of de novo initiation of OD-Tac after LT [22–24], but it is yet to be popularized in Asian countries, including Korea. Fundamentally, Bid-Tac and OD-Tac formulations do not have different metabolism or excretion within the human body. One difference between the 2 Tac formulations is the absorption in the digestive tract; absorption occurs in the stomach and upper small bowel with Bid-Tac, while absorption occurs throughout the stomach and whole small bowel with OD-Tac. Hence, with unstable gastrointestinal motility, Tac trough level may also be unstable, which in turn is highly unfavorable for Tac, with its low therapeutic index [25,26]. Thus, considering that de novo initiation of OD-Tac after LDLT is performed immediately postoperatively, when there are significant motility changes in the digestive tract, and considering that LDLT using small partial liver grafts, which probably induces poor gastrointestinal absorption resulting from elevated portal pressure, is prevalent in Asian countries, including Korea, additional evidence must be obtained before performing de novo initiation of OD-Tac after LDLT as standard practice [27].

The efficacy and safety of late conversion from Bid-Tac to OD-Tac at least 6 months after LT in patients with stable liver functions have been documented by multiple studies [11–18]. However, few studies have documented the efficacy and safety of early conversion from Bid-Tac to OD-Tac within 6 months after LT. In a few previous studies, early conversion from Bid-Tac to OD-Tac was mostly performed within 1–2 months after LT [10,27], primarily because patients show better adherence to treatment in the earlier days after LT and adjusting Tac dose and performing therapeutic drug monitoring are easier for patients staying at the hospital after the operation [15,28]. However, as previously mentioned, OD-Tac agents are more profoundly affected by gastrointestinal absorptive functions than do Bid-Tac agents [25,26]. Therefore, this study attempted the conversion from Bid-Tac to OD-Tac in patients showing normal liver graft function at 10–14 weeks after LDLT, which is thought to be a period of relatively stable and consistent absorption capacity of the digestive tract.

In the present study, the Tac trough level decreased by 25.7% at week 2 after the conversion from BID-Tac to OD-Tac with a 1: 1 dosage ratio (Figure 2A, P<0.001). As a result, the dose of OD-Tac had to be increased by 18.8% (Figure 2B, P=0.011). This phenomenon has been reported in previous studies [10,19], and considering that Tac has a narrow therapeutic range, additional studies should be conducted to substantiate the optimal dosage ratio for the conversion from Bid-Tac to OD-Tac.

None of the patients in our study developed an acute rejection from the time of Tac conversion until completion of the study at week 24. Further, there were no cases of graft loss or patient death during the entire study period. With regard to efficacy, the rejection, graft, and patient survival results in the present study were similar to previous findings [9,10,15,30].

Further, there were no serious adverse events during the follow-up period after Tac conversion (Table 2). There were also no changes in the indicators of renal function, such as serum creatinine level and eGFR, in relation to Tac conversion (Figure 3A, 3B), as well as no changes in serum bilirubin, AST, ALT, and glucose level (Figure 3C–3F). Lipid profile, such as cholesterol, HDL, LDL, and TG level, also did not differ after Tac conversion. These results are in line with previous findings that OD-Tac and BID-Tac do not differ in terms of safety [9,10,15,27,29,31–34].

Conclusions

The findings from this study suggest that early conversion from BID-Tac to OD-Tac at 10–14 weeks after LDLT is safe and feasible. However, this study could not observe long-term effects due to having a short follow-up period, so additional studies are needed to shed more light on this matter.