Pharmacokinetics and Clinical Outcomes of Generic Tacrolimus (Hexal) Versus Branded Tacrolimus in De Novo Kidney Transplant Patients: A Multicenter, Randomized Trial

Bioequivalence evaluation and blood concentration estimation of generic and branded tacrolimus in healthy subjects under fasting: A randomized, four-periods, two-sequences, complete repeated, crossover study

OBJECTIVE

The demand for generic tacrolimus is enormous. Our randomized trial was an open-label single-dose testing with four-periods and two-sequences; we aimed to evaluate the bioequivalence between a generic and branded tacrolimus by establishing their area under concentration-time curve (AUC) predictive equations. For better comparison, each tacrolimus served either as test vs. reference in sequence 1 or vice versa as reference vs. test in sequence 2.

METHODS

Forty healthy subjects were randomized into two groups, namely a sequence 1 group (N = 20 in test-reference-test-reference) or sequence 2 (N = 20, reference-test-reference-test) received a test tacrolimus (Ruibeirong®; Chengdu Shengdi Medicine Co., Ltd.) and a reference tacrolimus (Astagraf XL®, Astellas Ireland Co., Ltd.) under the fasting condition with a wash-out period of ≥14 days between every two phases. Blood samples were collected sequentially until 120 h after oral administration of tacrolimus.

RESULTS

A 95% upper confidence bound was -0.05% for the peak concentration (Cmax), -0.02% for the AUC from 0 to the last time point (AUC0-t), and - 0.02% for the AUC from 0 to infinity (AUC0-∞). The geometric least square means ratio (test/reference) with 90% of confidence interval (CI)) was 96.10% (90.58%-101.95%) for Cmax, 93.80% (88.52%-99.39%) for AUC0-t, and 94.34% (89.20%-99.77%) for AUC0-∞. Meanwhile, the ratio of within-subject standard deviation of test/reference (σWT/WR) with 90% CI was 0.66 (0.50-0.86) for Cmax, 0.73 (0.55-0.96) for AUC0-t, and 0.75 (0.57-0.98) for AUC0-∞. These results fulfilled the bioequivalence criteria by the Food and Drug Administration. Both products showed acceptable safety. Moreover, the AUC predictive equations (by linear regression plus limited sampling strategy) with 2-5 sampling time point showed the high performance (all R > 0.970, predictive error (PE) >0.5%, absolute PE <5.1%, which were interchangeable between test and reference products.

CONCLUSION

Generic tacrolimus (Ruibeirong®) is bioequivalent to branded tacrolimus (Astagraf XL®) with tolerable safety, which AUC predictive equations work well and are interchangeable between the two products.

Investigating Tacrolimus Disposition in Paediatric Patients with a Physiologically Based Pharmacokinetic Model Incorporating CYP3A4 Ontogeny, Mechanistic Absorption and Red Blood Cell Binding

Tacrolimus is a crucial immunosuppressant for organ transplant patients, requiring therapeutic drug monitoring due to its variable exposure after oral intake. Physiologically based pharmacokinetic (PBPK) modelling has provided insights into tacrolimus disposition in adults but has limited application in paediatrics. This study investigated age dependency in tacrolimus exposure at the levels of absorption, metabolism, and distribution. Based on the literature data, a PBPK model was developed to predict tacrolimus exposure in adults after intravenous and oral administration. This model was then extrapolated to the paediatric population, using a unique reference dataset of kidney transplant patients. Selecting adequate ontogeny profiles for hepatic and intestinal CYP3A4 appeared critical to using the model in children. The best model performance was achieved by using the Upreti ontogeny in both the liver and intestines. To mechanistically evaluate the impact of absorption on tacrolimus exposure, biorelevant in vitro solubility and dissolution data were obtained. A relatively fast and complete release of tacrolimus from its amorphous formulation was observed when mimicking adult or paediatric dissolution conditions (dose, fluid volume). In both the adult and paediatric PBPK models, the in vitro dissolution profiles could be adequately substituted by diffusion-layer-based dissolution modelling. At the level of distribution, sensitivity analysis suggested that differences in blood plasma partitioning of tacrolimus may contribute to the variability in exposure in paediatric patients.

Comparative Safety and Efficacy of Immunosuppressive Regimens Post-kidney Transplant: A Systematic Review

Immunosuppressive agents are used post-organ transplant to prevent acute rejection and graft losses. Tacrolimus, the most widely used immunosuppressive agent for kidney transplant recipients, has unfavorable side effects such as new-onset diabetes after transplant, nephrotoxicity, and electrolyte imbalances. Other drug groups such as the mammalian target of rapamycin (mTOR) inhibitors, belatacept, and bleselumab have been used to either substitute calcineurin inhibitors or reduce their exposure. This systematic analysis reviews evidence from randomized controlled trials to compare the safety and efficacy of various immunosuppressive regimens for kidney transplant recipients. An in-depth methodical search was conducted across PubMed, Cochrane Library, and Mendeley. PRISMA 2020 guidelines were followed for this study. Randomized controlled trials comparing varying regimens were included in this study. While there was no difference in safety and efficacy between once-daily and twice-daily tacrolimus, mTOR inhibitors showed to be a viable option for a reduced tacrolimus exposure regimen. Calcineurin inhibitor avoidance and early steroid withdrawal regimens both showed increased rates of rejection. Based on these findings, a regimen containing once-daily tacrolimus and an mTOR inhibitor with or without corticosteroid is a viable immunosuppressive regimen post-kidney transplant. Further trials, especially ones with longer follow-up periods, are needed to explore these regimens' long-term safety and efficacy.

Comparative safety of generic versus brand calcineurin inhibitors in solid organ transplant patients: a systematic review and meta-analysis

BACKGROUND

Although generic ciclosporin-A (CsA) and tacrolimus (TAC) have been used for the prophylaxis of organ rejection in transplant patients for decades, evidence in their safety profile compared to reference listed drugs (RLDs) in real-world transplant patients remains limited.

OBJECTIVES

To compare safety outcomes of generic CsA and TAC with the reference-listed drugs in solid organ transplant patients.

METHODS

We systematically searched MEDLINE, International Pharmaceutical Abstracts, PsycINFO, and Cumulative Index of Nursing and Allied Health Literature from inception until March 15, 2022, to select randomized and observational studies comparing safety profiles of generic versus brand CsA and TAC in de novo and/or stable solid organ transplant patients. Primary safety outcomes were changes in serum creatinine (Scr) and glomerular filtration rate (GFR). Secondary outcomes included incidences of infection, hypertension, diabetes, other serious adverse events (AEs), hospitalization, and death. Mean difference (MD) and relative risk (RR) with 95% confidence intervals (CIs) were calculated using random-effects meta-analyses.

RESULTS

Of 2612 publications identified, 32 studies met inclusion criteria. Seventeen studies had a moderate risk of bias. Scr was statistically significantly lower in patients using generic CsA compared to brand at 1 month (MD = -0.07; 95% CI: -0.11, -0.04), while there were no statistically significant differences at 4 months, 6 months, and 12 months. No differences were detected in Scr (MD = -0.04; 95% CI: -0.13, 0.04) and estimated GFR (MD = -2.06; 95% CI: -8.89, 4.77) between patients using generic and brand TAC at 6 months. No statistically significant differences between generic CsA and TAC with their RLDs were observed for secondary outcomes.

CONCLUSION

Findings support similarity in safety outcomes between generic and brand CsA and TAC in real-world solid organ transplant patients.

Proposed Definitions of T Cell-Mediated Rejection and Tubulointerstitial Inflammation as Clinical Trial Endpoints in Kidney Transplantation

The diagnosis of acute T cell-mediated rejection (aTCMR) after kidney transplantation has considerable relevance for research purposes. Its definition is primarily based on tubulointerstitial inflammation and has changed little over time; aTCMR is therefore a suitable parameter for longitudinal data comparisons. In addition, because aTCMR is managed with antirejection therapies that carry additional risks, anxieties, and costs, it is a clinically meaningful endpoint for studies. This paper reviews the history and classifications of TCMR and characterizes its potential role in clinical trials: a role that largely depends on the nature of the biopsy taken (indication vs protocol), the level of inflammation observed (e.g., borderline changes vs full TCMR), concomitant chronic lesions (chronic active TCMR), and the therapeutic intervention planned. There is ongoing variability-and ambiguity-in clinical monitoring and management of TCMR. More research, to investigate the clinical relevance of borderline changes (especially in protocol biopsies) and effective therapeutic strategies that improve graft survival rates with minimal patient morbidity, is urgently required. The present paper was developed from documentation produced by the European Society for Organ Transplantation (ESOT) as part of a Broad Scientific Advice request that ESOT submitted to the European Medicines Agency for discussion in 2020. This paper proposes to move toward refined definitions of aTCMR and borderline changes to be included as primary endpoints in clinical trials of kidney transplantation.

Thirty Years of Tacrolimus in Clinical Practice

Tacrolimus was discovered in 1984 and entered clinical use shortly thereafter, contributing to successful solid organ transplantation across the globe. In this review, we cover development of tacrolimus, its evolving clinical utility, and issues affecting its current usage. Since earliest use of this class of immunosuppressant, concerns for calcineurin-inhibitor toxicity have led to efforts to minimize or eliminate these agents in clinical regimens but with limited success. Current understanding of the role of tacrolimus focuses more on its efficacy in preventing graft rejection and graft loss. As we enter the fourth decade of tacrolimus use, newer studies utilizing novel combinations (as with the mammalian target of rapamycin inhibitor, everolimus, and T-cell costimulation blockade with belatacept) offer potential for enhanced benefits.

Immunosuppression with generic tacrolimus in liver and kidney transplantation-systematic review and meta-analysis on biopsy-proven acute rejection and bioequivalence

While rejection prevention with innovator tacrolimus (Tac) is one of the key factors for long-lasting graft function, the use of generic Tac is still under debate. Thus, we performed a systematic review and meta-analysis to provide an overview on the current body of evidence for the effect of generic Tac in adult liver (LT) and kidney transplantation (KT) with focus on both biopsy-proven acute rejection (BPAR) and bioequivalence. A systematic literature search for trials comparing generic versus innovator Tac was conducted accordingly. Seventeen studies (5 LT, 11 KT, 1 LT/KT) including 1412 patients were identified. About 92.9% (13/14; 5/5 LT, 8/9 KT) of studies reported the same or lower BPAR with generics (pooled RR: 0.84, 95% CI: 0.65-1.09); however, de novo studies showed a significantly lower risk with generic Tac (RR: 0.75, 95% CI: 0.63-0.90), whereas conversion studies showed increased risk (RR: 1.93, 95% CI: 1.00-3.70). Bioequivalence was demonstrated primarily in studies on conversion. The current evidence is mostly based on observational data and studies showing some risk of bias. In conclusion, whereas overall there was no significant difference in terms of BPAR, there is some evidence suggesting lower BPAR risk with generic Tac for de novo use.

Association of Genetic Variants in CYP3A4, CYP3A5, CYP2C8, and CYP2C19 with Tacrolimus Pharmacokinetics in Renal Transplant Recipients

BACKGROUND

Our study aimed to investigate the pharmacogenetics of cytochrome P3A4 (CYP3A4), CYP3A5, CYP2C8, and CYP2C19 and their influence on TAC Pharmacokinetics (PKs) in short-term renal transplant recipients.

METHODS

A total of 105 renal transplant recipients were enrolled. Target Sequencing (TS) based on next-generation sequencing technology was used to detect all exons, exon/intron boundaries, and flanking regions of CYP3A4, CYP3A5, CYP2C8, and CYP2C19. After adjustment of Minor Allele Frequencies (MAF) and Hardy-Weinberg Equilibrium (HWE) analysis, tagger Single-nucleotide Polymorphisms (SNPs) and haplotypes were identified. Influence of tagger SNPs on TAC concentrations was analyzed.

RESULTS

A total of 94 SNPs were identified in TS analysis. Nine tagger SNPs were selected, and two SNPs (rs15524 and rs4646453) were noted to be significantly associated with TAC PKs in short-term post-transplant follow-up. Measurement time points of TAC, body mass index (BMI), usage of sirolimus, and incidence of Delayed Graft Function (DGF) were observed to be significantly associated with TAC PKs. Three haplotypes were identified, and rs15524-rs4646453 was found to remarkably contribute to TAC PKs. Recipients carrying H2/H2 (GG-AA) haplotype also showed significantly high weight- and dose-adjusted TAC concentrations in posttransplant periods of 7, 14, and 30 days and 3 and 6 months.

CONCLUSIONS

Two tagger SNPs, namely, rs15524 and rs4646453, are significantly related to the variability of TAC disposition, and TAC measurement time points, BMI, usage of sirolimus, and incidence of DGF contribute to this influence. Recipients carrying H2/H2 (GG-AA) haplotype in rs15524-rs4646453 may require a low dosage of TAC during 1-year follow-up posttransplant.

Changes in the commercial brand of tacrolimus lead to subtherapeutic trough levels and acute rejection in renal transplant recipients

BACKGROUND

The vigilance of tacrolimus (TAC) trough levels is an essential part of renal transplant follow up. Reduced TAC trough levels and high variability are related to adverse outcomes. The aim of this study was to evaluate the impact of brand changes on tacrolimus (TAC) subtherapeutic (SubT) trough levels, acute rejection (AR), and kidney function.

METHODS

This is a prospective, observational cohort study of renal transplant recipients, between January 2016 and October 2018. Tacrolimus trough levels and brand used by the patient were both registered at every consult. Tacrolimus values ≤3.5 ng/mL were considered SubT.

RESULTS

445 patients were included. The median number of TAC brand changes was 2 (IQR, 1-4). Patients were grouped according to the number of brand changes: Group 1 = 0 (n = 107), Group 2 = 1-4 (n = 236), and Group 3 = ≥5 (n = 102). Patients with the greatest number of brand changes had a greater proportion and number of SubT TAC trough levels (Group 1 = 36.4%, average 0.53; Group 2 = 39.8%, average 0.65, Group 3 = 59.8%, average 1.17, P < .001) and AR (Group 1 = 0.9%, Group 2 = 11%, Group 3 = 14.7%, P < .001). On multivariate analysis, SubT levels and the number of brand changes were related to AR.

CONCLUSIONS

In Mexico, changes in TAC brand are associated with an elevated frequency of SubT levels. Brand changes and SubT levels are independently associated with acute rejection. The supply policies on TAC brands in Mexico require revision to avoid changing brands as much as possible.

Evaluation of Clinical and Safety Outcomes Following Uncontrolled Tacrolimus Conversion in Adult Transplant Recipients

PURPOSE

To compare clinical and safety outcomes of transplant recipients converted between different tacrolimus formulations to those patients who remained on a single formulation in an outpatient environment.

METHODOLOGY

This was a single-center, retrospective cohort study at a large tertiary care medical center with an associated institutional outpatient pharmacy system. Adult transplant recipients with institutional pharmacy refill from August 1, 2009, to May 31, 2016, were assessed. Patients were allocated into four separate groups: Group (A) innovator tacrolimus (no conversion), Group (B) generic tacrolimus (no conversion), Group (C) single conversion (from innovator to single generic or from generic to innovator tacrolimus), and Group (D) multiple conversions. Index date was either the date of first tacrolimus product conversion (Groups C and D) or a pre-specified post-transplant time (Groups A and B).

RESULTS

Overall, 100 patients were included in the analysis, 63% were male, 62% were Caucasian, and 59% were renal transplant recipients. When compared between groups, linear trends in dose-normalized tacrolimus levels were similar in the pre-index date period (p=0.52) and in the post-index date period (p=0.08). When groups were compared individually, linear trends in dose-normalized tacrolimus levels were significantly different pre- versus post-index date for Group B (p=0.008). There were no differences in the linear trends of dose-normalized tacrolimus levels across the other groups (p>0.05 for all). After the index date, 43% of patients across all groups required tacrolimus dose modification with no differences by group (p=0.32). Allograft function and hospitalizations were similar across all groups.

CONCLUSIONS

Conversion between tacrolimus generic formulations has been suggested to be unsafe. This study demonstrates that switching tacrolimus products in post-transplant recipients does not alter dose-normalized tacrolimus trough concentrations, renal or hepatic function, pathology, or hospitalizations.