Use of graft-derived cell-free DNA as an organ integrity biomarker to reexamine effective tacrolimus trough concentrations after liver transplantation.
BACKGROUND
Immunosuppressant therapeutic ranges for transplant patients have traditionally been established by indirect clinical means. However, "liquid biopsy" methods measuring graft-derived cell-free DNA (GcfDNA) in blood directly interrogate donor organ integrity. This study was performed to determine whether GcfDNA quantification could be used to reexamine minimally effective trough tacrolimus (Tacro) concentrations in liver transplantation (LTx) patients.


METHODS
As part of a large prospective study to demonstrate the ability of GcfDNA to identify early graft rejection, 10 adult white LTx patients [8 men, 2 women, 3 hepatitis C virus (HCV) positive; mean ± SD age (years) = 56 ± 9.4] had simultaneous GcfDNA and whole-blood trough Tacro concentrations measured between days 5 and 30 after LTx. Samples were analyzed using droplet digital polymerase chain reaction for GcfDNA and liquid chromatography tandem mass spectrometry for Tacro. GcfDNA and trough Tacro concentrations were then compared to identify Tacro concentrations associated with intact graft integrity.


RESULTS
Although there were large individual differences, there was a highly significant (Fisher P = 0.00002) segregation between whole-blood Tacro concentrations of ≥8 μg/L and normal (≤10%) GcfDNA percentages. The best discrimination in this population between effective and ineffective trough Tacro concentrations was estimated to be at 6.8 μg/L (P < 10(-7)). Compared with HCV- patients (n = 7), the 3 HCV+ patients had more variable associations between GcfDNA percentages and Tacro concentrations.


CONCLUSIONS
Direct measurement of graft integrity using GcfDNA was useful to confirm the lower limit of the therapeutic ranges for trough Tacro concentrations after LTx. It would probably be useful to do so also for other immunosuppressant drugs and after other solid organ transplants. The method might be especially useful to detect graft injury during immunosuppressant dose minimization strategies.
*Department of Clinical Chemistry, University Medical Center Göttingen; †Chronix Biomedical, Göttingen; and ‡Department of General, Visceral, and Pediatric Surgery, University Medical Center Göttingen, Germany.
Michael
M
Oellerich
Ekkehard
E
Schütz
Philipp
P
Kanzow
Jessica
J
Schmitz
Julia
J
Beck
Otto
O
Kollmar
Frank
F
Streit
Philip D
PD
Walson
D000328:Adult; D000368:Aged; D015415:Biomarkers / Q000097:blood; D004247:DNA / Q000097:blood*; D005260:Female; D006084:Graft Rejection / Q000517:prevention & control; D006801:Humans; D007166:Immunosuppressive Agents / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics* / Q000494:pharmacology; D016031:Liver Transplantation / Q000379:methods*; D008297:Male; D008875:Middle Aged; D010361:Patients; D011446:Prospective Studies; D016559:Tacrolimus / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics* / Q000494:pharmacology
D015415:Biomarkers; D007166:Immunosuppressive Agents; D004247:DNA; D016559:Tacrolimus