## Factors associated with the C₀:D ratio for tacrolimus and/or cyclosporine

**Tacrolimus.** When we dichotomized the 248 tacrolimus-treated patients according to the median C₀:D ratio, patients with an above-median ratio were significantly older, more likely to be male and had a higher BMI, higher glycaemia values, higher creatininaemia values and lower eGFR relative to patients with a below-median ratio. There were no differences in the use of drugs that interact with CYP3A4/5 or P-gp or that bind strongly to plasma proteins. Patients with an above-median tacrolimus C₀:D ratio presented significantly higher plasma levels of urea, PCS and IxS (but not of TMAO or IAA) (Supplementary data, Table S3). Univariate logistic analyses gave the same results and thus highlighted the association between a high tacrolimus C₀:D ratio and three uraemic toxins (namely urea, PCS and IxS) (Supplementary data, Table S4).

In a multivariate analysis, age, sex and BMI were independently associated with the tacrolimus C₀:D ratio. The significant association between the tacrolimus C₀:D ratio and plasma IxS levels [OR 1.36 (95% CI 1.00–1.85)] was independent of sex, BMI and age (Table 3, plasma IxS levels). The association between the tacrolimus C₀:D ratio and plasma urea levels was still significant after adjustment for sex and BMI [OR 2.29 (95% CI 1.28–4.09)], whereas the association was no longer significant after full adjustment for sex, BMI and age [OR 1.71 (95% CI 0.93–3.16)] (Table 3, plasma urea levels). The association between the tacrolimus C₀:D ratio and plasma PCS levels was still significant after adjustment for sex and BMI [OR 1.31 (95% CI 1.06–1.62)] but not after adjustment for sex, BMI and age [OR 1.22 (95% CI 0.99–1.51)] (Table 3, plasma PCS levels).

**Cyclosporine.** When we dichotomized the 155 patients treated with cyclosporine according to the median cyclosporine C₀:D ratio, patients with an above-median ratio were significantly older, more likely to be female and had a higher BMI and higher glycaemia values. There were no differences with regard to the use of drugs that interacted with CYP3A4/5, P-gp or plasma proteins. Patients with an above-median cyclosporine C₀:D ratio presented significantly higher plasma levels of TMAO but not of urea, PCS, IxS or IAA (Supplementary data, Table S5). A univariate logistic analysis gave the same results and again highlighted the association between a high cyclosporine C₀:D ratio and the plasma TMAO level (Supplementary data, Table S6).

In a multivariate analysis, age, sex and BMI were independently associated with the cyclosporine C₀:D ratio. However, the association between the cyclosporine C₀:D ratio and the plasma TMAO level was no longer significant [OR 1.12 (95% CI 0.78–1.61)] after adjustment for sex, BMI and age (Table 4).

## DISCUSSION

In the present cross-sectional study of a cohort of kidney transplant recipients, we found that elevated plasma concentrations of certain uraemic toxins were associated with elevated blood concentrations of the calcineurin inhibitors tacrolimus and cyclosporine. However, the nature of the associations differed

between tacrolimus and cyclosporine; indeed, both drugs have the same pharmacological target but bind strongly to different plasma proteins.

We first studied plasma levels of five notable uraemic toxins (IAA, IxS, PCS, TMAO and urea) in a cohort of patients in whom the time since transplantation ranged from 1 to 40 years. In fact, most studies of uraemic toxins

<table><caption>Table 3. Multivariate logistic regression analysis of factors associated with the tacrolimus C₀:D ratio and considered as a continuous [log-normalized (ln)] variable (n = 248)</caption><thead><tr><th>Variables</th><th>OR (95% CI)</th><th>P-value</th></tr></thead><tbody><tr><td><strong>Plasma IxS levels</strong></td><td></td><td></td></tr><tr><td>Unadjusted</td><td></td><td></td></tr><tr><td>In IxS</td><td>1.41 (1.06–1.86)</td><td>0.018</td></tr><tr><td>Model 1, including In IxS and sex</td><td></td><td></td></tr><tr><td>In IxS</td><td>1.43 (1.07–1.91)</td><td>0.015</td></tr><tr><td>Sex</td><td>1.83 (1.07–3.12)</td><td>0.027</td></tr><tr><td>Model 2, including In IxS, sex and BMI</td><td></td><td></td></tr><tr><td>In IxS</td><td>1.44 (1.28–4.09)</td><td>0.017</td></tr><tr><td>Sex</td><td>1.85 (1.11–3.35)</td><td>0.029</td></tr><tr><td>BMI</td><td>1.12 (1.06–1.19)</td><td>&lt;0.0001</td></tr><tr><td>Model 3, including In IxS, sex, BMI and age</td><td></td><td></td></tr><tr><td>In IxS</td><td>1.36 (1.00–1.85)</td><td>0.047</td></tr><tr><td>Sex</td><td>2.03 (1.15–3.60)</td><td>0.015</td></tr><tr><td>BMI</td><td>1.11 (1.04–1.18)</td><td>0.001</td></tr><tr><td>Age</td><td>1.04 (1.02–1.06)</td><td>&lt;0.0001</td></tr><tr><td><strong>Plasma urea levels</strong></td><td></td><td></td></tr><tr><td>Unadjusted</td><td></td><td></td></tr><tr><td>In urea</td><td>2.08 (1.21–3.6)</td><td>0.008</td></tr><tr><td>Model 1, including In urea, sex</td><td></td><td></td></tr><tr><td>In urea</td><td>2.24 (1.28–3.92)</td><td>0.005</td></tr><tr><td>Sex</td><td>1.89 (1.11–3.24)</td><td>0.019</td></tr><tr><td>Model 2, including In urea, sex and BMI</td><td></td><td></td></tr><tr><td>In urea</td><td>2.29 (1.28–4.09)</td><td>0.005</td></tr><tr><td>Sex</td><td>1.93 (1.11–3.35)</td><td>0.020</td></tr><tr><td>BMI</td><td>1.12 (1.06–1.19)</td><td>&lt;0.0001</td></tr><tr><td>Model 3, including In urea, sex, BMI and age</td><td></td><td></td></tr><tr><td>In urea</td><td>1.71 (0.93–3.16)</td><td>0.085</td></tr><tr><td>Sex</td><td>2.04 (1.16–3.60)</td><td>0.014</td></tr><tr><td>BMI</td><td>1.11 (1.05–1.18)</td><td>0.001</td></tr><tr><td>Age</td><td>1.04 (1.01–1.06)</td><td>0.001</td></tr><tr><td><strong>Plasma PCS levels</strong></td><td></td><td></td></tr><tr><td>Unadjusted</td><td></td><td></td></tr><tr><td>In PCS</td><td>1.27 (1.04–1.54)</td><td>0.018</td></tr><tr><td>Model 1 including In PCS and sex</td><td></td><td></td></tr><tr><td>In PCS</td><td>1.27 (1.04–1.56)</td><td>0.017</td></tr><tr><td>Sex</td><td>1.88 (1.10–3.20)</td><td>0.021</td></tr><tr><td>Model 2 including In PCS, sex and BMI</td><td></td><td></td></tr><tr><td>In PCS</td><td>1.31 (1.06–1.62)</td><td>0.011</td></tr><tr><td>Sex</td><td>1.93 (1.11–3.37)</td><td>0.020</td></tr><tr><td>BMI</td><td>1.13 (1.06–1.20)</td><td>&lt;0.0001</td></tr><tr><td>Model 3 including In PCS, sex, BMI and age</td><td></td><td></td></tr><tr><td>In PCS</td><td>1.22 (0.99–1.51)</td><td>0.067</td></tr><tr><td>Sex</td><td>2.07 (1.17–3.67)</td><td>0.012</td></tr><tr><td>BMI</td><td>1.11 (1.05–1.18)</td><td>0.001</td></tr><tr><td>Age</td><td>1.04 (1.02–1.06)</td><td>0.001</td></tr></tbody></table>
<table><caption>Table 4. Multivariate logistic regression analysis of factors associated with the cyclosporine C₀:D ratio, with plasma TMAO levels entered as a continuous [log-normalized (ln)] variable (n = 155)</caption><thead><tr><th></th><th>OR (95% CI)</th><th>P-value</th></tr></thead><tbody><tr><td>Unadjusted</td><td></td><td></td></tr><tr><td>ln TMAO</td><td>1.37 (1.00-1.87)</td><td>0.046</td></tr><tr><td>Model 1, including</td><td></td><td></td></tr><tr><td>ln TMAO and sex</td><td></td><td></td></tr><tr><td>ln TMAO</td><td>1.39 (1.01-1.92)</td><td>0.042</td></tr><tr><td>Sex</td><td>0.42 (0.21-0.82)</td><td>0.012</td></tr><tr><td>Model 2, including ln TMAO, sex and BMI</td><td></td><td></td></tr><tr><td>ln TMAO</td><td>1.26 (0.90-1.76)</td><td>0.182</td></tr><tr><td>Sex</td><td>0.40 (0.19-0.83)</td><td>0.014</td></tr><tr><td>BMI</td><td>1.18 (1.09-1.27)</td><td>&lt;0.0001</td></tr><tr><td>Model 3, including ln TMAO, sex, BMI and age</td><td></td><td></td></tr><tr><td>ln TMAO</td><td>1.12 (0.78-1.61)</td><td>0.540</td></tr><tr><td>Sex</td><td>0.33 (0.15-0.72)</td><td>0.005</td></tr><tr><td>BMI</td><td>1.20 (1.10-1.30)</td><td>&lt;0.0001</td></tr><tr><td>Age</td><td>1.06 (1.02-1.09)</td><td>0.002</td></tr></tbody></table>

have focused on pre-dialysis and dialysis patients rather than kidney transplant recipients [27, 28]. Hence the present report extends the data on a panel of important uraemic toxins in a large number of patients at variable times since transplantation. We confirmed that uraemic toxin levels were significantly higher in patients with lower eGFRs than in patients with higher eGFRs [28]. However, the uraemic toxin levels were lower than those described in dialysis patients, reflecting the kidney's functional activity after transplantation. The broad range of uraemic toxin levels enabled us to evaluate the latter's association with the blood concentration of calcineurin inhibitors.

Many studies have demonstrated that CKD not only decreases renal drug clearance, but also modifies drug absorption, distribution and non-renal clearance [6]. Uraemic toxins accumulate as renal function deteriorates and have been linked to adverse outcomes [13, 29, 30]. These toxins might also affect drug pharmacokinetics [6]. As immunosuppressive drugs require TDM, kidney transplant recipients constitute a good model for studying the potential impact of uraemic toxins on blood levels of calcineurin inhibitors, especially since these drugs are also cleared through non-renal pathways.

In this study we found that elevated plasma levels of IxS and PCS (both of these toxins bind strongly to albumin) were associated with a higher tacrolimus C₀:D ratio (98.8% of which is bound to albumin and alpha-1-acid glycoprotein in vivo [20]). These associations were independent of other factors that can modify immunosuppressant concentrations, such as the co-prescription of CYP3A4/5 or P-gp inducers or inhibitors, albuminaemia, liver disorders, sex, BMI and age for IxS. However, adjustment for age weakened the association with PCS. Indeed, IxS and PCS bind with high affinity to albumin, specifically with Sudlow site II [31], and might compete directly with other substrates for binding to albumin [31, 32]. Hence we hypothesize that IxS and PCS compete with tacrolimus and

lead to an increase in the C₀:D ratio. However, it is hard to say whether the putative effect of IxS and PCS on the C₀:D ratio is a specific effect or, in contrast, is indirectly linked to the deterioration in renal function. The mechanisms underlying uraemic toxin accumulation and the extent to which uraemic toxin accumulation may or not enhance the renal toxicity of tacrolimus require further study.

On the same lines, elevated plasma urea levels were independently associated with a higher tacrolimus C₀:D ratio; however, adjustment for age weakened this association. Indeed, it is well known that age-related physiological changes induce changes in drug distribution, metabolism and elimination [33]. Furthermore, a chronic increase in the urea level is significantly associated with a higher mean protein carbamylation in animals [15] and humans [14]. Although carbamylation is a post-translational modification of some proteins, urea-derived isocyanic acid can react non-enzymatically with proteins and this induces structural and functional modifications. A high degree of albumin carbamylation might decrease the protein's binding of some drugs [34].

In contrast to results obtained in patients treated with tacrolimus, we failed to find an association between IxS, PCS and urea levels and the cyclosporine C₀:D ratio. This lack of an association might be due to lower accumulation of uraemic toxins in patients treated with cyclosporine or to the fact that, unlike tacrolimus (which binds to albumin), cyclosporine binds strongly to high-density lipoprotein (HDL) and low-density lipoprotein [20]. We also found that elevated TMAO levels were associated with an elevated cyclosporine C₀:D ratio. This association was no longer significant after adjustment for age, sex and BMI. TMAO is a small, water-soluble, gut-derived uraemic toxin produced by the oxidation of trimethylamine. Over the last decade, a growing body of pre-clinical and clinical evidence has identified TMAO as an important contributor to the pathogenesis of cardiovascular disease [35]. Indeed, elevated TMAO levels are associated with a greater incident risk of major cardiovascular adverse events [10, 36]. We are not aware of data linking TMAO to changes in drug pharmacokinetics/pharmacodynamics. However, pre-clinical data have shown an inverse association between TMAO and HDL, with a reduction in HDL-mediated reverse cholesterol transport as TMAO levels rise [37].

Maintaining levels of immunosuppressant within the therapeutic range is essential for preventing acute graft rejections while minimizing drug-related toxicity. In the present analysis, patients with a higher tacrolimus C₀:D ratio presented higher glycaemia, blood pressure (BP) and creatininaemia values, all of which are well-known adverse drug reactions associated with calcineurin inhibitors. Even though TDM and dose adjustment can maintain tacrolimus levels within the therapeutic window, it appears that the accumulation of uraemic toxins (PCS, IxS and urea) can increase exposure to tacrolimus. This finding has potential implications for other drugs that bind strongly to albumin, since a larger free fraction might lead to unexpected exposures, which can alter their efficacy and/or tolerance. This finding emphasizes the need for more research on how to decrease uraemic toxin levels.
In the present report we focused on two drugs with similar pharmacokinetic and pharmacodynamic properties. Both drugs have low bioavailability, bind strongly to plasma proteins, are mainly metabolized by cytochrome P450 3A4/5 and are mainly excreted in the bile [20]. The main difference relates to the type of plasma protein to which they bind: albumin for tacrolimus and lipoproteins for cyclosporine. We hypothesize that our present results can be explained (at least in part) by this difference in binding. Furthermore, we suggest that some uraemic toxins might modify the tacrolimus C₀:D ratio by affecting its binding to albumin. Although protein binding is a major determinant of drug activity, the latter is influenced by many other factors. For example, uraemic toxins such as parathyroid hormone can induce the downregulation of cytochrome P450 or modify the activity of certain drug transporters [38, 39]. Machado *et al.* [21] recently suggested that IxS increases the expression and activity of the efflux transporter P-gp and that this effect depends on the aryl hydrocarbon receptor pathway. In addition, IxS and PCS are substrates of the membrane transporters OATs, which are expressed in the kidneys but also in other tissues, such as the liver and the small intestine. These transporters play a central role in the cell uptake and clearance of gut microbiota metabolites, including IxS and PCS [40]. Although tacrolimus does not appear to have an impact on the *in vitro* activity of OAT1 and OAT3 [41], an interaction between tacrolimus and the transporters involving uraemic toxins is not excluded and deserves further investigation. All of these factors may influence drug pharmacokinetics and blood concentration. Consequently it is very difficult to identify specific molecular mechanisms in patients.

Our study had some limitations. The cross-sectional design prevented us from evaluating possible changes over time in adverse drug reactions and outcomes related to concentrations of uraemic toxins and immunosuppressants. Even though we adjusted our multivariate analyses, it is possible that the association between uraemic toxins and the immunosuppressant concentration was due to other confounders. Likewise, we adjusted for potential drug interactions but cannot rule out potential interactions related to the patients' polypharmacy. Lastly, and as mentioned above, the large number of factors influencing drug pharmacokinetics means that it is difficult to prove the presence of an interaction between certain uraemic toxins and tacrolimus. However, this study also had strengths, such as its use of sensitive, validated assays of five uraemic toxins known to have harmful effects in kidney transplant recipients [25]. It is one of the first studies to have simultaneously evaluated blood uraemic toxin levels and drug concentrations in a clinical setting.

## CONCLUSION

In a cross-sectional study of 403 kidney transplant recipients, we observed an association between plasma levels of certain uraemic toxins and the blood levels of two calcineurin inhibitors. In particular, we observed a relationship between elevated plasma PCS, IxS and urea levels and elevated blood tacrolimus C₀:D ratios, suggesting a potential interaction through binding sites on albumin. The potential clinical impact of this

relationship must now be evaluated prospectively for tacrolimus and other drugs that bind strongly to albumin.

## SUPPLEMENTARY DATA

Supplementary data are available at ndt online.

## ACKNOWLEDGEMENTS

We thank Dr David Fraser (Biotech Communication SARL, Ploudalmézeau, France) for copy-editing assistance.

## FUNDING

The uraemic toxin assays were funded by a grant from Santhélys (Loos, France).

## CONFLICT OF INTEREST STATEMENT

C.A., Y.B., S.K., A.L.H., K.M. S.B. and S.L. have nothing to declare. G.C. received fees for advisory board participation from Amgen, Vifor, Astellas and Takeda and grants for clinical research, none related to this work. Results presented in this article have not been published previously in whole or part, except in abstract format.

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Received: 22.2.2021; Editorial decision: 27.3.2021
**Potential interactions between uremic toxins and drugs: an application in kidney transplant recipients treated with calcineurin inhibitors**

**Authors:** Camille André <fnref n="1" />,<fnref n="2" />, Gabriel Choukroun<fnref n="1" />,<fnref n="3" />, Youssef Bennis<fnref n="1" />,<fnref n="2" />, Said Kamel<fnref n="1" />,<fnref n="4" />, Sandra Bodeau<fnref n="1" />,<fnref n="2" />, Sophie Liabeuf<fnref n="1" />,<fnref n="2" />

**Authors' institutions:**

**Running title:** Uremic toxins and immunosuppressant therapy

**Corresponding author:**

Sophie Liabeuf, PharmD, PhD
Pharmacology Department
Amiens University Medical Center
F-80054 Amiens
France
Phone: + 33-322-087-995
E-mail: liabeuf.sophie@chu-amiens.fr

**Keywords:** uremic toxins, tacrolimus, cyclosporine, kidney transplantation

<footnote n="1">¹ MP3CV Laboratory, EA7517, Jules Verne University of Picardie, Amiens, F-80000 Amiens, France</footnote>

<footnote n="2">² Department of Clinical Pharmacology, Amiens University Medical Center, F-80000 Amiens, France</footnote>

<footnote n="3">³ Department of Nephrology Dialysis and Transplantation, Amiens University Medical Center, F-80000 Amiens, France</footnote>

<footnote n="4">⁴ Department of Biochemistry, Amiens University Medical Center, F-80000 Amiens, France</footnote>
ABSTRACT

**Background:** In addition to affecting glomerular filtration rate, chronic kidney disease (CKD) changes the absorption, distribution and nonrenal clearance of a number of drugs. The uremic toxins that accumulate with as renal function deteriorates can potentially affect drug pharmacokinetics. Given the requirement for therapeutic drug monitoring (TDM) with most immunosuppressants, the latter are good models for understanding the potential impact of uremic toxins on blood concentrations of drugs. We focused on two calcineurin inhibitors (tacrolimus and cyclosporine) with similar pharmacological properties: low but variable oral bioavailability, strong binding to plasma proteins (albumin for tacrolimus and lipoproteins for cyclosporine), metabolism by cytochrome P450 3A4/5, and excretion in the bile. Our starting hypothesis was that uremic toxins influence the exposure of immunosuppressants. The study's objective was to determine whether plasma concentrations of certain uremic toxins were correlated with blood concentrations of the two immunosuppressants.

**Methods:** DRUGTOX was a cross-sectional study of 403 adult patients followed up after kidney transplantation at Amiens University Medical Center (Amiens, France) and who had undergone TDM of calcineurin inhibitors between August 4th, 2019, and March 11th, 2020. The patients had been treated daily with oral tacrolimus or cyclosporine. Two groups were constituted: 203 patients with low uremic toxin levels (estimated glomerular filtration rate (eGFR) according to the Modification of Diet in Renal Disease equation >40 mL/min/1.73m²) and 200 patients with high uremic toxin levels (eGFR <40 mL/min/1.73m²). For each patient, immunosuppressant trough concentrations (C₀) were measured in whole-blood samples and then normalized against the total daily dose: C₀/D ratio. After centrifugation, the sample was assayed for five uremic toxins (urea, trimethylamine N-oxide (TMAO), indole acetic acid (IAA), para-cresylsulfate (PCS), and indoxylsulfate (IxS)) using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Univariate and multivariate logistic regressions were used to evaluate the associations between plasma uremic toxin levels and the blood tacrolimus or cyclosporine C₀/D ratio.

**Results:** The median [interquartile range] age was 56 [48-66] and the median eGFR was 41 [30-57] ml/min/1.73 m². The majority of the patients (56.5%) were at CKD stage 3. A total of 248 (61.5%) patients were being treated with tacrolimus and 155 (38.5%) were being treated with cyclosporine. The median time between transplantation and study inclusion was 6.5 years. Plasma urea, TMAO, IAA, PCS and IxS levels rose progressively with the CKD stage. In a univariate logistic analysis, age, sex, BMI, urea, IxS and PCS were significantly associated with an increment in the tacrolimus C₀/D ratio. A multivariate analysis revealed an independent association with IxS (odds ratio [95% confidence interval]: 1.36 [1.00; 1.85], after adjustment for sex, age and BMI, whereas adjustment for age weakened the association for PCS (OR: 1.22 (0.99; 1.55)) and urea (OR: 1.71 (0.93; 3.16)). In a univariate logistic analysis, age, sex, BMI, and the TMAO level (but neither PCS, IxS, IAA nor urea) were significantly associated with an increment in the cyclosporine C₀/D ratio.

**Conclusion:** Even though TDM and dose adaptation of immunosuppressants keeps levels within the therapeutic window, elevated exposure to tacrolimus (but not cyclosporine) is associated with an accumulation of PCS, IxS and urea. This might be explained by an interaction between tacrolimus and highly albumin-bound uremic toxins. Our findings may have implications for other drugs that bind with high affinity to albumin (since an elevated free fraction might lead to unexpected exposures, which can alter their efficacy and/or tolerance).
Annexe III : traitements pris de manière concomitante au tacrolimus et susceptibles d'interagir avec ses paramètres pharmacocinétiques (n = 248)

<table><thead><tr><th></th><th>Tous les patients<br>(n=248)</th><th>R &lt; 123,70<br>(n=124)</th><th>R &gt; 123,70<br>(n=124)</th><th>valeur<br>de p</th></tr></thead><tbody><tr><td><strong>Traitements concomitants à la prise de tacrolimus</strong></td><td></td><td></td><td></td><td></td></tr><tr><td>Au moins un inhibiteur fort du CYP3A4/5</td><td>6 (2,42%)</td><td>3 (2,42%)</td><td>3 (2,42%)</td><td>1,0000</td></tr><tr><td>Au moins un inhibiteur faible CYP3A4/5</td><td>3 (1,21%)</td><td>2 (1,61%)</td><td>1 (0,81%)</td><td>1,0000</td></tr><tr><td>Au moins un inducteur fort CYP3A4/5</td><td>5 (2,02%)</td><td>3 (2,42%)</td><td>2 (1,61%)</td><td>1,0000</td></tr><tr><td>Au moins un inducteur faible CYP3A4/5</td><td>2 (0,81%)</td><td>2 (1,61%)</td><td>0 (0,00%)</td><td>0,4980</td></tr><tr><td>Au moins un inhibiteur de la P-gp</td><td>49 (19,76%)</td><td>20 (16,13%)</td><td>29 (23,39%)</td><td>0,2020</td></tr><tr><td>Au moins un inducteur de la P-gp</td><td>4 (1,61%)</td><td>3 (2,42%)</td><td>1 (0,81%)</td><td>0,6219</td></tr><tr><td>Au moins un médicament se lie fortement aux protéines plasmatiques</td><td>243 (97,98%)</td><td>121 (97,58%)</td><td>122 (98,39%)</td><td>1,0000</td></tr></tbody></table>

CYP3A4/5 : cytochrome P450 3A4/5 ; P-gp : glycoprotéine-P
Annexe IV : traitements pris de manière concomitante avec la ciclosporine et susceptibles d'interagir avec ses paramètres pharmacocinétique (n = 155)

<table><thead><tr><th></th><th>Tous les patients<br>(n=155)</th><th>R < 52,89<br>(n=78)</th><th>R > 52,89 (n=77)</th><th>valeur<br>de p</th></tr></thead><tbody><tr><td><strong>Traitements concomitants à la prise de ciclosporine</strong></td><td></td><td></td><td></td><td></td></tr><tr><td>Au moins un inhibiteur fort du CYP3A4/5</td><td>7 (4,52)</td><td>2 (2,56)</td><td>5 (6,49)</td><td>0,2762</td></tr><tr><td>Au moins un inhibiteur faible CYP3A4/5</td><td>2 (1,29)</td><td>1 (1,28)</td><td>1 (1,30)</td><td>1,0000</td></tr><tr><td>Au moins un inducteur fort CYP3A4/5</td><td>1 (0,65)</td><td>1 (1,28)</td><td>0 (0,00)</td><td>1,0000</td></tr><tr><td>Au moins un inducteur faible CYP3A4/5</td><td>1 (0,65)</td><td>0 (0,00)</td><td>1 (1,30)</td><td>0,4968</td></tr><tr><td>Au moins un inhibiteur de la P-gp</td><td>37 (23,87)</td><td>17 (21,79)</td><td>20 (25,97)</td><td>0,6732</td></tr><tr><td>Au moins un inducteur de la P-gp</td><td>1 (0,65)</td><td>1 (1,28)</td><td>0 (0,00)</td><td>1,0000</td></tr><tr><td>Au moins un médicament se lie fortement aux protéines plasmatiques</td><td>155 (100,00)</td><td>78 (100,00)</td><td>77 (100,00)</td><td>NA</td></tr></tbody></table>

CYP3A4/5 : cytochrome P450 3A4/5 ; P-gp : glycoprotéine-P
# SERMENT DE GALIEN

En présence des Maîtres de la Faculté,
je fais le serment :

D'honorer ceux qui m'ont instruit dans les préceptes de mon art et de leur témoigner ma reconnaissance en restant fidèle aux principes qui m'ont été enseignés et d'actualiser mes connaissances.

D'exercer, dans l'intérêt de la santé publique, ma profession avec conscience et de respecter non seulement la législation en vigueur, mais aussi les règles de déontologie, de l'honneur, de la probité et du désintéressement.

De ne jamais oublier ma responsabilité et mes devoirs envers la personne humaine et sa dignité.

En aucun cas, je ne consentirai à utiliser mes connaissances et mon état pour corrompre les mœurs et favoriser des actes criminels.

De ne dévoiler à personne les secrets qui m'auraient été confiés ou dont j'aurais eu connaissance dans l'exercice de ma profession.

De faire preuve de loyauté et de solidarité envers mes collègues pharmaciens.

De coopérer avec les autres professionnels de santé. Que les hommes m'accordent leur estime si je suis fidèle à mes promesses.

Que je sois couvert d'opprobre et méprisé de mes confrères si j'y manque.
# Étude des interactions entre les toxines urémiques et les médicaments inhibiteurs de la calcineurine dans une cohorte de patients transplantés rénaux

Thèse d'exercice pour le diplôme d'état de docteur en pharmacie

Université de Picardie-Jules Verne

par Camille ANDRÉ

Présentée et soutenue publiquement le 07 avril 2022

**Mots clefs :** toxines urémiques, tacrolimus, ciclosporine, transplantation rénale, interactions pharmacocinétiques

## Résumé

**Contexte** : En plus d'affecter le débit de filtration glomérulaire, la maladie rénale chronique modifie l'absorption, la distribution et la clairance non-rénale de nombreux médicaments. Les toxines urémiques (TU), qui s'accumulent avec la détérioration de la fonction rénale, peuvent potentiellement affecter les paramètres pharmacocinétiques des médicaments. Les immunosuppresseurs de la classe des inhibiteurs de la calcineurine (ICN), tacrolimus et ciclosporine, sont un bon modèle pour comprendre le potentiel impact des TU sur les concentrations sanguines en médicaments, de par leur élimination hépatique indépendante de la fonction rénale, et grâce au suivi thérapeutique et pharmacologique (STP) appliqué aux immunosuppresseurs. Notre hypothèse est la suivante : les TU influent sur la pharmacocinétique des ICN chez les patients transplantés rénaux. L'objectif de cette étude est donc de déterminer si les concentrations plasmatiques en TU sont corrélées à l'exposition sanguine en ICN.

**Matériels et méthodes** : Une étude transversale de 403 patients suivis au CHU d'Amiens-Picardie pour le STP de leur traitement par ICN, a été constituée. Pour chaque patient, la concentration résiduelle en ICN ($C_{min}$) a été mesurée dans le sang total et rapportée à la posologie journalière en mg/kg/J (D), permettant de calculer le ratio $C_{min}/D$, reflétant l'exposition sanguine en ICN. Sur le même échantillon, la concentration plasmatique de 5 TU a été dosée par méthode enzymatique ou par chromatographie liquide haute performance couplée à de la spectrométrie de masse en tandem : l'urée, le trimethylamine N-oxide (TMAO), l'acide indole-acétique (IAA), le p-crésyl sulfate (pCS) et l'indoxyl sulfate (IxS).

**Résultats** : Les concentrations plasmatiques en TU augmentent progressivement au fur et à mesure de la dégradation de la fonction rénale. L'âge, le sexe, l'indice de masse corporelle (IMC), l'urée, l'IxS et le pCS sont significativement associés à l'augmentation du ratio $C_{min}/D$ de tacrolimus. L'analyse multivariée montre une association indépendante du ratio $C_{min}/D$ avec l'IxS (odd ratio 1 ;36 [intervalle de confiance à 95% : 1,00 ; 1,85]) après ajustement sur l'âge, le sexe et l'IMC. L'association n'est plus significative pour la ciclosporine.

**Conclusion** : L'augmentation de l'exposition sanguine du tacrolimus est associée significativement à l'accumulation d'IxS, de pCS et d'urée et ce, malgré la mise en place du STP, nécessaire pour garder les concentrations de tacrolimus dans la zone thérapeutique.

**Président du Jury** : Saïd KAMEL, Professeur des Universités -Praticien Hospitalier, Centre Hospitalier Universitaire d'Amiens

**Directeur de thèse** : Sophie LIABEUF, Professeur des Université - Praticien Hospitalier, Centre Hospitalier Universitaire d'Amiens

Sandra BODEAU Maître de Conférences des Universités - Praticien Hospitalier, Centre Hospitalier Universitaire d'Amiens

**Membres du jury** : Pauline CAILLARD, Praticien Hospitalier, Centre Hospitalier Universitaire d'Amiens

Thomas DUFLOT, Assistant-Hospitalo-Universitaire, Centre Hospitalier Universitaire de Rouen