AUC‑targeted tacrolimus dosing in kidney transplant recipients

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What is this study about?

The study involves individuals who have undergone kidney transplantation and examines the medication tacrolimus, provided as PROGRAF 1 mg capsule. Tacrolimus is an immunosuppressive drug that helps the body accept the new kidney by reducing the immune response that can cause rejection.

The purpose of the study is to determine whether dosing guided by AUC leads to a higher proportion of participants reaching the desired drug level eight weeks after the transplant compared with standard dosing. AUC (area under the curve) is a measurement that reflects how much drug is present in the blood over a set time period. Participants will have blood samples taken at several points after the transplant, and the dose of tacrolimus will be adjusted based on these results. The study follows participants for a few months, with regular visits to collect samples and check safety.

1 enrollment and consent

after joining the study, a written consent form is signed to confirm understanding of the trial procedures.

personal health information and baseline laboratory tests are collected to confirm eligibility.

2 baseline evaluation

a comprehensive medical review is performed, including kidney transplant history and current medications.

initial blood samples are taken to establish baseline levels of kidney function and immune markers.

3 start of tacrolimus medication

the study drug, prograf (tacrolimus) capsules, is taken by mouth.

the prescribed amount is 30 mg per day, divided according to the dosing instructions provided by the study team.

the medication is started on day one of the trial and continues for the duration of the study, which is eight weeks after transplantation.

4 initial intensive blood sampling (rich sampling)

within the first few days of taking tacrolimus, multiple blood draws are performed over a 12‑hour period after a dose.

these samples are used to calculate the area under the curve (auc) from 0 to 12 hours, which reflects how much drug is in the body.

the auc measurement helps determine whether the current dose achieves the desired therapeutic level.

5 dose adjustment based on auc

the results of the rich sampling are reviewed, and the tacrolimus dose may be increased or decreased to reach the individualized target auc.

any change in dose is communicated in writing, and the new dosing schedule is followed from that point forward.

6 regular follow‑up visits with limited sampling

at scheduled intervals, typically weekly, three blood samples are taken at specific times after a dose to estimate the auc with fewer draws.

these limited samples allow ongoing monitoring of drug exposure without the extensive sampling of the initial phase.

7 monitoring of intra‑individual variability

the trial tracks the coefficient of variation (cv%) of the auc-to‑trough (c0) ratio for each participant.

high variability may prompt further dose adjustments to maintain stable drug levels.

8 microbiome analysis (optional secondary assessment)

stool samples may be collected at designated visits to study the gut microbiome using metagenomic sequencing.

participation in this part is optional and does not affect the primary medication regimen.

9 final assessment at eight weeks

after eight weeks post‑transplant, a comprehensive evaluation is performed to determine if the target auc has been achieved.

the final blood sampling includes both rich and limited methods to compare results over the study period.

10 completion of trial participation

once the final assessment is finished, the study procedures are concluded for the participant.

all collected data are recorded for analysis, and no further study‑specific visits are required.

Who Can Join the Study?

Be a new kidney transplant recipient (the kidney was just transplanted) and have a typical level of immune‑system risk for organ rejection.
Take an immunosuppressive medication (a drug that lowers your immune system to help prevent the new kidney from being rejected) called Prograf® (tacrolimus) that is taken twice each day.
Be older than 18 years.
Be able to follow the medication schedule and other medical instructions on your own.
Be willing and able to sign a written informed consent form, which shows you understand the study and agree to take part.

Who Cannot Join the Study?

Hypersensitivity to the study medicines or any of the inactive ingredients (called excipients) means you are allergic to them, so you cannot join the trial.
Women who are breastfeeding, pregnant, or who could become pregnant and are not using a very reliable birth‑control method (called highly effective contraception) cannot take part in the study.

Where you can join this trial?

Verified and Recommended Sites

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Verified Sites

Site Name	City	Country	Status
Oslo Universitetssykehus HF	Oslo	Norway

Other Sites

No sites found in this category

Trial status

Country	Status	Recruitment Start
Norway	Not yet recruiting	07.09.2026

Trial locations

Investigated Drugs:

Tacrolimus

PROGRAF is an oral capsule that contains tacrolimus, a medicine that suppresses the immune system to help prevent the body from rejecting a newly transplanted organ. In this study, the drug is given after transplantation and the researchers are testing a new way of adjusting the dose based on the total amount of drug in the blood over 12 hours (AUC). They want to find out if this AUC‑guided approach helps more patients reach the ideal drug level compared with the usual method that adjusts the dose based on a single blood test taken just before the next dose (C0). The trial follows patients for eight weeks after their transplant to see how well the dosing method works.

Investigated Diseases:

Renal transplant

Kidney transplantation – Kidney transplantation is the surgical replacement of a diseased kidney with a healthy donor kidney. After the operation the donor organ begins to filter blood and produce urine, taking over the function of the failed native kidneys. Over weeks to months the transplanted kidney integrates with the recipient’s blood vessels and urinary tract. The function of the new kidney can change over time, with possible fluctuations in how well it cleans the blood. Monitoring the organ’s performance helps understand its natural course after transplantation.

Trial ID:

2026-527107-22-00

Protocol code:

ACTOR

Trial Phase:

Therapeutic confirmatory (Phase III)

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AUC‑targeted tacrolimus dosing in kidney transplant recipients

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