Adherence of Renal Transplant Recipients to Once-daily, Prolonged-Release and Twice-daily, Immediate-release Tacrolimus-based Regimens in a Real-life Setting in Sweden

Once- Versus Twice-Daily Tacrolimus Therapy: Does Improved Adherence Lead to Better Efficacy?-A Pharmacokinetic Perspective

Tacrolimus, a critical immunosuppressant in organ transplantation, is available in immediate-release (IR-T) and extended-release (ER-T) formulations. While ER-T improves patient adherence, clinical studies have not demonstrated superior outcomes compared to IR-T. However, the underlying reasons for this discrepancy remain unclear. This study aimed to evaluate tacrolimus exposure under non-adherent dosing behaviors with IR-T and ER-T and to provide insights for selecting the optimal tacrolimus formulation. Monte Carlo simulations were conducted to assess the proportion of target attainment (%PTA) and deviation time (DT) from the therapeutic range in scenarios involving delayed or missed doses, based on published population pharmacokinetic models. The influence of renal function, the post-transplantation period, and hematocrit levels on %PTA and DT were also analyzed. Our findings revealed that patients on ER-T exhibited lower %PTA and longer DT than those on IR-T when doses were delayed or missed, reflecting poorer "forgiveness." This observation elucidates the lack of clinical superiority observed for ER-T in previous studies. Furthermore, fast metabolizers experienced worse forgiveness with ER-T, exacerbating the challenge of maintaining therapeutic levels. Additionally, a web-based dashboard was developed to calculate the %PTA and DT for individual patients and to provide formulation recommendations tailored to their dosing behaviors and clinical characteristics. In conclusion, adherence and forgiveness play a crucial role in the success of pharmacotherapy. This study highlights the significance of pharmacokinetic modeling and simulation in providing evidence-based recommendations for selecting the optimal tacrolimus formulation.

Tacrolimus Formulation, Exposure Variability, and Outcomes in Kidney Transplant Recipients

INTRODUCTION

Few studies have compared within-patient variability measures of tacrolimus trough levels by formulation and assessed within-patient variability on outcomes of kidney transplant recipients.

RESEARCH QUESTIONS

(1) To compare within-patient variability of trough levels when converting from twice-daily to once-daily tacrolimus using standard deviation, coefficient of variation, and intrapatient variability percent. (2) To use the 3 measures of variability to examine the relationship between tacrolimus once-daily within-patient variability and total graft failure (i.e., return to chronic dialysis, pre-emptive retransplant, death with graft function).

DESIGN

In this observational cohort study, within-patient variability of trough levels pre- and post-conversion from twice-daily to once-daily tacrolimus were compared using Wilcoxon matched-pairs signed-rank test. Graft outcomes were analyzed using Kaplan-Meier curves and multivariable Cox proportional hazards models.

RESULTS

In 463 patients, within-patient variability differences pre- and post-conversion of median standard deviation, coefficient of variation, and intrapatient variability percent were -0.16 (P = 0.09), -0.01 (P = 0.52), and -1.41 (P = 0.32), respectively. Post-conversion, every 1 unit increase in within-patient variability standard deviation and intrapatient variability percent and every 0.1 unit increase in the coefficient of variation was associated with an increased hazard ratio [1.19 (P = 0.004), 1.02 (P = 0.030), 1.13 (P = 0.001), respectively] of total graft failure. Post-conversion, within-patient variability above cohort medians using standard deviation and coefficient of variation had a significantly higher risk of total graft failure.

DISCUSSION

Under a program-wide conversion, no significant difference was observed in within-patient variability post-conversion from twice-daily to once-daily tacrolimus using the three measures of variability. High within-patient variability was associated with adverse transplant outcomes post-conversion.

Outcomes in kidney transplant recipients treated with immediate-release tacrolimus capsules versus extended-release tacrolimus capsules: A cohort study

INTRODUCTION

Prior randomized trials and observational studies have generally reported similar outcomes in kidney transplant recipients (KTRs) treated with immediate-release tacrolimus (IR-TAC) versus extended-release tacrolimus (ER-TAC). However, many of these previous studies focused on patients with low immunological risks, had small sample sizes and brief follow-up periods, and excluded outcomes associated with graft loss, such as chronic rejection.

METHODS

To address these limitations, we conducted a cohort study of 848 KTRs at a single transplantation center who had generally high immunological risks and were treated with either IR-TAC capsules (589 patients, 65.9%) or ER-TAC capsules (289 patients, 34.1%). All patients received their designated maintenance immunosuppressive regimen for at least 3 months post-transplantation. Afterwards, tacrolimus formulation was at the discretion of each patient's transplant nephrologist. For the two treatment groups, we compared the hazards of experiencing a composite outcome of acute or chronic antibody-mediated rejection (AMR), acute or chronic T-cell-mediated rejection, de novo DSA, and/or graft loss over a 3-year period starting at 3 months post-transplantation.

RESULTS

In a multivariable Cox proportional hazards regression model, KTRs treated with IR-TAC capsules had an increased hazard of experiencing the composite outcome when compared to patients treated with ER-TAC capsules; however, this result was not significant (adj HR 1.24, 95% CI .92-1.68, p = .163). Similar results were obtained with inverse probability of treatment weighting (IPTW) using a propensity score (adj HR 1.25, 95% CI .93-1.68, p = .146).

CONCLUSION

These findings suggest that when compared to IR-TAC capsules, ER-TAC capsules do not reduce the hazard of poor outcomes in KTRs with generally high immunological risks.

Graft Failure Due to Nonadherence among 150 Prospectively-Followed Kidney Transplant Recipients at 18 Years Post-transplant: Our Results and Review of the Literature

Background: We previously reported that graft failure due to nonadherence (GFNA) was a major cause of graft loss in kidney transplantation. Here, among 150 prospectively-followed kidney transplant recipients at 18 years post-transplant, we provide: updated (longer-term) estimates of cause-specific graft loss probabilities, risk factors for developing GFNA, and detailed characterizations of patients’ overt nonadherent (NA) behavior, including timing, extent, and clinical consequences. Methods: Determination of the patient becoming NA in taking his/her immunosuppressive medications, and the underlying cause of graft loss, were determined prospectively by the attending physicians. For never-functioning-graft, GFNA, GF due to causes other than NA (Other GF), and death with a functioning graft (DWFG), cumulative incidence functions were used to estimate the cumulative probabilities of cause-specific graft loss. Cox stepwise regression was used to determine significant multivariable predictors for the hazard rate of developing GFNA. Results: GFNA was a major cause of graft loss (22/150 patients), particularly among African-American and Hispanic recipients <50 years of age-at-transplant (20/56 experienced GFNA), with estimated percentages of such patients ever developing GFNA ranging between 36.9 and 41.5%. These patients were also at a higher risk of developing Other GF. For the remaining patients (2/94 experienced GFNA), estimated percentages of ever-developing GFNA were much lower (range: 0.0−6.7%). The major cause of graft loss among recipients ≥50 years of age was DWFG; GFNA rarely occurred among older recipients. In 21/22 GFNA patients, NA behavior lasted continuously from the time of developing NA until GFNA. In total, 28/150 patients became NA, and 67.9% (19/28) occurred beyond 36 months post-transplant. A total of 25 of 28 NA patients (89.3%) developed biopsy-proven acute rejection and/or chronic rejection that was directly attributed to the NA behavior. Lastly, 25/28 admitted to NA behavior, with financial and psychological components documented in 71.4% (20/28) and 96.4% (27/28) of NA cases, respectively. Conclusions: These results highlight the importance of performing serial monitoring of patients for overt NA behavior throughout their post-transplant follow-up. Financial and psychological components to NA behavior need to be simultaneously addressed with the goal of achieving complete avoidance/elimination of NA behavior among higher risk patients.

Is simplification of immunosuppressive medication a way to promote medication adherence of kidney transplant recipients? Findings from a randomized controlled trial

After kidney transplantation, a strict immunosuppressive medication regimen is necessary for graft survival. However, nonadherence to medication has been shown to occur early after transplantation and to increase over time. Weaning the recipient off dual therapy onto monotherapy in order to reduce immunosuppressive burden may also be a way to promote adherence, although little is known about the impact of such a regimen on fear of rejection. We performed a cohort study on medication adherence and fear of rejection in a randomized, investigator‐driven, open‐label, single‐centre pilot study. Recipients were randomized at 6‐months post‐transplant to either continue Tacrolimus and Mycophenolate mofetil (TAC/MMF) or to taper MMF at 6 months and discontinue MMF at 9 months (TAC monotherapy). Recipients completed questionnaires about medication adherence and fear of rejection at 6 and 12‐months post‐transplantation. Medication adherence was significantly higher in the TAC monotherapy group compared to dual TAC/MMF therapy group (χ² (1) = 4.582; P = 0.032). We found no difference in fear of rejection between the two groups of recipients (P = 0.887). Simplification of the medication regimen is a potential tool for increasing adherence in clinical practice (Netherlands Trial Register – NL4672).