Comparison of two mycophenolate mofetil dosing regimens after hematopoietic cell transplantation

Clinical Evidence on the Purported Pharmacokinetic Interactions between Corticosteroids and Mycophenolic Acid

Corticosteroids (steroids) are commonly used concurrently with mycophenolic acid (MPA) as the first-line immunosuppression therapy for the prevention of rejection in solid organ transplantations. Steroids are also commonly administered with MPA in various autoimmune disorders such as systemic lupus erythematosus and idiopathic nephrotic syndrome. Despite various review articles having suggested the presence of pharmacokinetic interactions between MPA and steroids, definitive data have not yet been demonstrated. The aim of this Current Opinion is to critically evaluate the available clinical data and propose the optimal study design for characterising the MPA-steroid pharmacokinetic interactions. The PubMed and Embase databases were searched for relevant clinical articles in English as of September 29, 2022, where a total of 8 papers have been identified as supporting and 22 as non-supporting the purported drug interaction. To objectively evaluate the data, novel assessment criteria to effectively diagnose the interaction based on known MPA pharmacology were formulated, including the availability of independent control groups, prednisolone concentrations, MPA metabolite data, unbound MPA concentrations, and the characterisations of entero-hepatic recirculation and MPA renal clearance. Overall, the majority of the identified corticosteroid data were pertaining to prednisone or prednisolone. Our assessment indicated that no conclusive mechanistic data supporting the interaction are available in the current clinical literature, and further studies are required to quantify the effects/mechanisms of steroid-tapering or withdrawal on MPA pharmacokinetics. This current opinion provides justification for further translational investigations, as this particular drug interaction has the potential to exert significant adverse outcomes in patients prescribed MPA.

Reduced Enterohepatic Recirculation of Mycophenolate and Lower Blood Concentrations are Associated with the Stool Bacterial Microbiome After Hematopoietic Cell Transplantation

BACKGROUND

Mycophenolate mofetil (MMF) is an important immunosuppressant used after allogeneic hematopoietic cell transplant (HCT). MMF has a narrow therapeutic index and blood concentrations of mycophenolic acid (MPA), the active component of MMF, are highly variable. Low MPA concentrations are associated with risk of graft vs host disease (GvHD) while high concentrations are associated with toxicity. Reasons for variability are not well known and may be due, at least in part, to the presence of β-glucuronidase producing bacteria in the gastrointestinal tract which enhance MPA enterohepatic recirculation (EHR) by transforming MPA metabolites formed in the liver back to MPA.

OBJECTIVE

To determine if individuals with high MPA EHR have a greater abundance of β-glucuronidase producing bacteria in their stool and higher MPA concentrations relative to those with low EHR.

STUDY DESIGN

We conducted a pharmacomicrobiomics study in 20 adult HCT recipients receiving a myeloablative or reduced intensity preparative regimen. Participants received MMF 1g IV every 8 hours with tacrolimus. Intensive pharmacokinetic sampling of mycophenolate was conducted before hospital discharge. Total MPA, MPA glucuronide (MPAG) and acylMPAG were measured. EHR was defined as a ratio of MPA area under the concentration-versus-time curve (AUC)_4-8 to MPA AUC_0-8. Differences in stool microbiome diversity and composition, determined by shotgun metagenomic sequencing, were compared above and below the median EHR (22%, range 5-44%).

RESULTS

Median EHR was 12% and 29% in the low and high EHR groups, respectively. MPA troughs, MPA AUC_4-8 and acylMPAG AUC_4-8/AUC_0-8, were greater in the high EHR group vs low EHR group [1.53 vs 0.28 mcg/mL, p = 0.0001], [7.33 vs 1.79 hr*mcg/mL, p = 0.0003] and [0.33 vs 0.24 hr*mcg/mL, p = 0.0007], respectively. MPA AUC_0-8 was greater in the high EHR than the low EHR group and trended towards significance [22.8 vs. 15.3 hr*mcg/mL, p=0.06]. Bacteroides vulgatus, stercoris and thetaiotaomicron were 1.2-2.4 times more abundant (p=0.039, 0.024, 0.046, respectively) in the high EHR group. MPA EHR was positively correlated with B. vulgatus (⍴=0.58, p≤0.01) and B. thetaiotaomicron (⍴=0.46, p<0.05) and negatively correlated with Blautia hydrogenotrophica (⍴=-0.53, p<0.05). Therapeutic MPA troughs were achieved in 80% of patients in the high EHR group and 0% in the low EHR. There was a trend towards differences in MPA AUC_0-8 and MPA C_ss mcg/mL in high vs. low EHR groups (p=0.06).

CONCLUSION

MPA EHR was variable. Patients with high MPA EHR had greater abundance of Bacteroides species in stool and higher MPA exposure than patients with low MPA EHR. Bacteroides may therefore be protective from poor outcomes such as graft vs host disease but in others it may increase the risk of MPA adverse effects. These data need to be confirmed and studied after oral MMF.

Pharmacokinetics of mycophenolic acid after haplo-hematopoietic stem cell transplantation in Japanese recipients

PURPOSE

Mycophenolate mofetil (MMF), a mycophenolic acid (MPA) prodrug, is used to prevent graft-versus-host disease (GVHD) in hematopoietic stem cell transplantation (HSCT). Although previous studies have reported that enterohepatic circulation (EHC) of MPA, which is usually observed in MMF-treated patients, does not occur in HSCT patients, it is unclear what happens in haploidentical-HSCT (haplo-HSCT) patients, who are using post-transplant cyclophosphamide. This study was conducted to investigate MPA pharmacokinetics in haplo-HSCT patients.

METHODS

Seventeen haplo-HSCT patients, who received MMF for GVHD prophylaxis, were enrolled in this study. We collected blood samples on days 14 and 28, and plasma MPA concentrations were measured by high-performance liquid chromatography; pharmacokinetic parameters such as area under the curve (AUC), mean residence time (MRT), and apparent oral clearance (CL/F) were measured with moment analysis. We also evaluated EHC as AUC_6-12h/AUC_0-12h.

RESULTS

There was no significant difference in MPA pharmacokinetic parameters between days 14 and 28. There was also no difference between the pharmacokinetic parameter changes and diarrhea. Additionally, varying plasma MPA concentrations suggested that MPA EHC did not occur.

CONCLUSION

In this study, we revealed the pharmacokinetics of MMF in Japanese haplo-HSCT recipients. Additionally, our study demonstrated that MPA EHC might not occur in Japanese haplo-HSCT recipients.

Weight-based mycophenolate mofetil dosing predicts acute GVHD and relapse after allogeneic hematopoietic cell transplantation

OBJECTIVES

Higher MMF dose can reduce acute GVHD risk after allogeneic hematopoietic cell transplantation (HCT). We examined the effect of MMF dose, relative to patient actual body weight (mg/kg/day), on outcomes of 680 adults after HCT.

METHODS

MMF was combined with cyclosporine (n = 599) or sirolimus (n = 81). We divided MMF dose/kg/day in quartiles.

RESULTS

The median time to grade II-IV acute GVHD was 32 days. The incidence of grade II-IV acute GVHD at day 30 was 30% in 1st (<29), 20% in 2nd (29-34), 16% in 3rd (35-41), and 19% in 4th (≥42) quartile (P < .01). Corresponding relapse incidence at 1 year was 16%, 25%, 27%, and 31%, respectively (P = .01). In multivariate analysis, as compared to 1st quartile, higher dose of weight-based MMF reduced grade II-IV acute GVHD (HR = 0.64 for 2nd, HR = 0.48 for 3rd, and HR = 0.55 for 4th quartile), but increased the risk of relapse (HR = 1.63 for 2nd, HR = 1.75 for 3rd, and HR = 2.31 for 4th quartile).

CONCLUSIONS

Weight-based MMF dose had no significant impact on engraftment, chronic GVHD, or survival. These data suggest that higher weight-based MMF dose reduces the risk of acute GVHD at the expense of increased relapse and supports conducting prospective studies to optimize MMF dosing after HCT.

Drug monitoring for mycophenolic acid in graft-vs-host disease prophylaxis in cord blood transplantation

AIMS

We performed the retrospective analysis to clarify the significance of drug monitoring for mycophenolic acid (MPA), the active form of mycophenolate mofetil (MMF), in prophylaxis for graft-vs-host disease (GVHD) in cord blood transplantation.

METHODS

We retrospectively analysed the data of 46 patients who underwent first cord blood transplantation and received GVHD prophylaxis with tacrolimus plus MMF. MPA levels were measured on days 7 and 21, and 24-hour areas under the curve (AUC0-24 ) were estimated.

RESULTS

The engraftment and 3-year overall survival rates of all patients were 94% and 78%, respectively. The cumulative incidence of sepsis before engraftment was higher in patients with AUC0-24 on day 7 of >60 μg h/mL than in other patients (33 vs 6%, P = .02). The cumulative incidence of grade II-IV acute GVHD was higher in patients with AUC0-24 on day 21 of ≤30 μg h/mL than in other patients (80 vs 50%, P = .04). The cumulative incidence of human herpesvirus 6 reactivation was higher in patients with AUC0-24 on day 21 of ≤48 μg h/mL (median) than in other patients (50 vs 19%, P = .03).

CONCLUSION

Blood level of MPA was associated with risk of acute GVHD and infection. A prospective trial evaluating the benefit of personalized MMF dosing using MPA levels is needed.

Reduced-Intensity Conditioning Followed by Related and Unrelated Allografts for Hematologic Malignancies: Expanded Analysis and Long-Term Follow-Up

Reduced-intensity conditioning (RIC) extends the curative potential of allogeneic hematopoietic cell transplantation (HCT) to patients with hematologic malignancies unable to withstand myeloablative conditioning. We prospectively analyzed the outcomes of 292 consecutive patients, median age 58 years (range, 19 to 75) with hematologic malignancies treated with a uniform RIC regimen of cyclophosphamide, fludarabine, and total body irradiation (200 cGy) with or without antithymocyte globulin and cyclosporine and mycophenolate mofetil graft-versus-host disease (GVHD) prophylaxis followed by allogeneic HCT at the University of Minnesota from 2002 to 6. Probability of 5-year overall survival was 78% for patients with indolent non-Hodgkin lymphoma, 53% for chronic myelogenous leukemia, 55% for Hodgkin lymphoma, 40% for acute myelogenous leukemia, 37% for myelodysplastic syndrome, 29% for myeloma, and 14% for myeloproliferative neoplasms. Corresponding outcomes for relapse were 0%, 13%, 53%, 37%, 39%, 75%, and 29%, respectively. Disease risk index (DRI) predicted both survival and relapse with superior survival (64%) and lowest relapse (16%) in those with low risk score compared with 24% survival and 57% relapse in those with high/very-high risk scores. Recipient cytomegalovirus (CMV)-positive serostatus was protective from relapse with the lowest rates in those also receiving a CMV-positive donor graft (29%). The cumulative incidence of 2-year nonrelapse mortality was 26% and was lowest in those receiving a matched sibling graft at 21%, with low (21%) or intermediate (18%) HCT-specific comorbidity index, and was similar across age groups. The incidence of grades II to IV acute GVHD was 43% and grades III to IV 27%; the highest rates were found in those receiving an unrelated donor (URD) peripheral blood stem cell (PBSC) graft, at 50%. Chronic GVHD at 1 year was 36%. Future approaches incorporating alternative GVHD prophylaxis, particularly for URD PBSC grafts, and targeted post-transplant antineoplastic therapies for those with high DRI are indicated to improve these outcomes.

Pharmacokinetics of intravenous mycophenolate mofetil in allogeneic hematopoietic stem cell-transplanted Japanese patients

PURPOSE

Mycophenolate mofetil (MMF) is increasingly used among Japanese patients undergoing allogeneic hematopoietic stem cell transplantation (allo-SCT). Because pharmacokinetic data for MMF in the Asian population are limited, we conducted this investigation.

METHODS

Intravenous MMF (1000 mg/dose) was administered to 10 patients along with cyclosporine or tacrolimus for 10 days after allo-SCT; it was administered every 8 h in peripheral blood stem cell- and bone marrow-transplanted patients, and every 12 h in cord blood-transplanted patients. MMF was administered orally at the same dose from day 11. Plasma concentrations of mycophenolic acid (MPA) were measured by high-performance liquid chromatography.

RESULTS

The MPA AUC_0 - tau was 31.9 ± 3.4, 26.2 ± 2.4, and 21.0 ± 2.2 µg*h/mL, the mean C_trough was 0.25, 0.35, and 0.37 µg/mL, and the C_max was 10.8, 9.2, and 5.5 µg/mL on days 2, 9, and 16, respectively. The AUC_0 - tau and C_max were significantly higher after intravenous MMF dosing than after oral MMF dosing. All patients exhibited successful neutrophil engraftments in a median time of 18 days. Grade II acute graft-versus-host disease (GvHD) of the skin was observed in two patients, and one patient developed limited chronic GvHD. Individual cases of transient and curable grade III oral mucositis and diarrhea were observed; however, MMF was not discontinued. No other severe complications or infections were observed.

CONCLUSIONS

Intravenously administered MMF was safe and possibly effective in achieving higher MPA plasma concentrations for GvHD prophylaxis after allo-SCT in Japanese patients.

Pharmacokinetic Variability of Mycophenolic Acid in Pediatric and Adult Patients With Hematopoietic Stem Cell Transplantation

The aim of this study was to evaluate the pharmacokinetic variations of mycophenolic acid (MPA), the active metabolite of mycophenolate mofetil (MMF), in both pediatric and adult patients following hematopoietic stem cell transplantation (HSCT). Twenty pediatric patients with a median age of 3 years (range 0.2-12 years) and 13 adult patients with a median age of 54 years (range 18-63 years) were enrolled. Blood samples were collected on days 0, 7, 14, 21, and 30 after allogeneic HSCT. Total and free (unbound) MPA as well as MPA 7-O-glucuronide (MPAG) were quantified using a validated LC-MS/MS assay. The plasma protein binding of MPA and MPAG did not change significantly in pediatric patients over the 1-month sampling period post-HSCT. However, it increased in adult patients from day 7 to day 30 post-HSCT, from 97.3 ± 0.8% to 98.3 ± 0.6% for MPA (P < .05), and 74.6 ± 9.4% to 82.9 ± 8.1% for MPAG (P < .05). The plasma protein binding of MPA was significantly higher in males compared to females in both pediatric (98.3 ± 1.1% vs 97.4 ± 1.1%) and adult (98.1 ± 0.7% vs 97.4 ± 1.2%) patients (P < .05). The MPAG/MPA ratios on a milligram-per-kilogram dose basis in adult patients were significantly higher than those in pediatric patients (4.3 ± 3.4 vs 2.4 ± 2.6; P < .05). Time-dependent plasma protein binding and age-related differences in MPA metabolism at least in part impact the reported large intra- and interindividual variability in MPA pharmacokinetics. These patient and pharmacologic factors, if incorporated into MMF regimen design and modification, may contribute to the rational dose selection of MMF in HSCT patients.

Clinical Pharmacokinetics of Mycophenolic Acid in Hematopoietic Stem Cell Transplantation Recipients

Mycophenolate mofetil (MMF), an ester prodrug of mycophenolic acid (MPA), is widely used as a maintenance immunosuppressive regimen in solid organ transplant patients. It is increasingly used for the prophylaxis and treatment of graft-versus-host disease (GVHD) in hematopoietic stem cell transplantation (HSCT) patients. MPA displays extensive binding to serum albumin and glucuronidation to the inactive MPA-7-O-glucuronide (MPAG). Here, we review and discuss the pertinent information regarding the clinical pharmacokinetics of MPA in HSCT patients. The pharmacokinetics of MPA are altered in HSCT patients with lower oral bioavailability, shorter half-life and higher clearance than those in healthy volunteers and renal transplant recipients. Moreover, clearance may be increased in young pediatric patients. The optimal MMF dosing and preferred targets are still under investigation in HSCT patients due to the substantial intra- and inter-individual pharmacokinetic variability of MPA and broad range of transplants (malignant vs. nonmalignant, related vs. unrelated donor, and human leukocyte antigen mismatch). The complex pharmacokinetics of MPA have partly hampered the efficient use of MMF, and pharmacokinetic studies in HSCT patients have been limited in size and mostly inconclusive. Future research should be multi-institutional and focus on developing clinical decisions with adequate statistical power to improve clinical care of HSCT recipients.

Pharmacokinetics, Pharmacodynamics, and Pharmacogenomics of Immunosuppressants in Allogeneic Hematopoietic Cell Transplantation: Part II

Part I of this article included a pertinent review of allogeneic hematopoietic cell transplantation (alloHCT), the role of postgraft immunosuppression in alloHCT, and the pharmacokinetics, pharmacodynamics, and pharmacogenomics of the calcineurin inhibitors and methotrexate. In this article (Part II), we review the pharmacokinetics, pharmacodynamics, and pharmacogenomics of mycophenolic acid (MPA), sirolimus, and the antithymocyte globulins (ATG). We then discuss target concentration intervention (TCI) of these postgraft immunosuppressants in alloHCT patients, with a focus on current evidence for TCI and on how TCI may improve clinical management in these patients. Currently, TCI using trough concentrations is conducted for sirolimus in alloHCT patients. Several studies demonstrate that MPA plasma exposure is associated with clinical outcomes, with an increasing number of alloHCT patients needing TCI of MPA. Compared with MPA, there are fewer pharmacokinetic/dynamic studies of rabbit ATG and horse ATG in alloHCT patients. Future pharmacokinetic/dynamic research of postgraft immunosuppressants should include '-omics'-based tools: pharmacogenomics may be used to gain an improved understanding of the covariates influencing pharmacokinetics as well as proteomics and metabolomics as novel methods to elucidate pharmacodynamic responses.

Combination Therapy for Graft-versus-Host Disease Prophylaxis with Etanercept and Extracorporeal Photopheresis: Results of a Phase II Clinical Trial

Reduced-intensity conditioning (RIC) regimens minimize early toxicity after allogeneic hematopoietic cell transplantation (HCT) by placing greater reliance on establishing a graft-versus-leukemia effect (GVL). Because graft-versus-host disease (GVHD) and GVL are tightly linked, inhibition of T cell populations that cause GVHD may lead to an unintended increased risk of relapse in the RIC setting. Although not completely understood, etanercept and extracorporeal photopheresis (ECP) are thought to ameliorate GVHD without direct T cell inhibition. We hypothesized that adding these 2 agents to a standard GVHD prophylaxis regimen of tacrolimus and mycophenolate mofetil (MMF) would improve survival by reducing GVHD-related mortality without increasing relapse rates. Therefore, we conducted a prospective phase II clinical trial that incorporated tacrolimus, MMF, etanercept, and ECP as GVHD prophylaxis in 48 patients undergoing RIC unrelated donor transplantation. The preferred RIC was fludarabine 160 mg/m(2) + busulfan 6.4 mg/kg to 12.8 mg/kg ± total body irradiation 200 cGy. Etanercept .4 mg/kg (maximum dose, 25 mg) was given subcutaneously twice weekly for 8 weeks after HCT and ECP was given for 12 treatments, starting weekly on day 28 weekly and tapering off by day 180. The median age of the study patients was 60 (range, 18 to 71) years. Donors were 7/8 (n = 14, 29%) or 8/8 (n = 34, 71%) HLA matched. All patients engrafted neutrophils at a median of 12 days. The cumulative incidence of grades II to IV acute GVHD at day 100 was 46%, but it was typically sensitive to initial steroid treatment (84% day 56 complete response/partial response rate). Overall survival at 1 year in this older, frequently mismatched unrelated donor setting was excellent (73%) because of low rates of nonrelapse mortality (21%) and relapse (19%). However, this strategy was not effective at preventing a high incidence of chronic GVHD and late deaths led to a drop in 2-year survival, declining to 56%, reflecting a high incidence of chronic GVHD.

Intensified Mycophenolate Mofetil Dosing and Higher Mycophenolic Acid Trough Levels Reduce Severe Acute Graft-versus-Host Disease after Double-Unit Cord Blood Transplantation

Although mycophenolate mofetil (MMF) has replaced corticosteroids as immunosuppression in cord blood transplantation (CBT), optimal MMF dosing has yet to be established. We intensified MMF dosing from every 12 to every 8 hours to augment graft-versus-host disease (GVHD) prophylaxis in double-unit cord blood transplantation (dCBT) and evaluated outcomes according to the total daily MMF dose/kg in 174 dCBT recipients (median age, 39 years; range, 1 to 71) who underwent transplantation for hematologic malignancies. Recipients of an MMF dose ≤ the median (36 mg/kg/day) had an increased day 100 grade III and IV acute GVHD (aGVHD) incidence compared with patients who received >36 mg/kg/day (24% versus 8%, P = .008). Recipients of ≤ the median dose who had highly HLA allele (1 to 3 of 6) mismatched dominant units had the highest day 100 grade III and IV aGVHD incidence of 37% (P = .009). This finding was confirmed in multivariate analysis (P = .053). In 83 patients evaluated for mycophenolic acid (MPA) troughs, those with a mean week 1 and 2 trough < .5 μg/mL had an increased day 100 grade III and IV aGVHD of 26% versus 9% (P = .063), and those who received a low total daily MMF dose and had a low mean week 1 and 2 MPA trough had a 40% incidence (P = .008). Higher MMF dosing or MPA troughs had no impact on engraftment after myeloablation. This analysis supports intensified MMF dosing in milligram per kilogram per day and MPA trough level monitoring early after transplantation in dCBT recipients.

Higher Dose of Mycophenolate Mofetil Reduces Acute Graft-versus-Host Disease in Reduced-Intensity Conditioning Double Umbilical Cord Blood Transplantation

Mycophenolate mofetil (MMF) is frequently used in hematopoietic cell transplantation (HCT) for graft-versus-host disease (GVHD) prophylaxis and to facilitate engraftment. We previously reported that a higher level of mycophenolic acid can be achieved with an MMF dose of 3 g/day than with 2 g/day. Here, we retrospectively compared clinical outcomes of reduced-intensity conditioning (RIC) double umbilical cord blood (dUCB) HCT recipients receiving cyclosporine A with MMF 2 g (n = 93) versus 3 g (n = 175) daily. Multiple regression analysis adjusted for antithymocyte globulin in the conditioning revealed that MMF 3 g/day led to a 49% relative risk (RR) reduction in grade II to IV acute GVHD rate (RR, .51; 95% confidence interval, .36 to .72; P < .01). However, the higher MMF dose was not protective for chronic GVHD. Additionally, MMF dose was not an independent predictor of neutrophil engraftment or treatment-related mortality at 6 months or 2-year post-transplantation disease relapse, disease-free survival, or overall survival. Higher MMF dose did not increase risk of infectious complications, and infection-related mortality was similar for both MMF doses. Our data indicate that MMF 3 g/day reduces the risk of acute GVHD without affecting other clinical outcomes and should be used for GVHD prophylaxis after RIC dUCB transplantation.

Optimizing drug therapy in pediatric SCT: focus on pharmacokinetics

Given age-related differences in drug metabolism and indications for hematopoietic SCT (HSCT), personalized drug dosing of the conditioning regimen and post-transplant immunosuppression may reduce graft rejection, relapse rates and toxicity in pediatric HSCT recipients. This manuscript summarizes the pharmacokinetic/dynamic data of HSCT conditioning and post-grafting immunosuppression, presented at the First Annual Pediatric Bone Marrow Transplant Consortium (PBMTC) meeting in April 2013. Personalized dosing of BU to a target plasma exposure reduces graft rejection in children and improves relapse/toxicity rates in adults. Current weight-based dosing achieves the target BU exposure in only a minority (24.3%) of children. The initial BU dose should be based on the European Medicines Agency nomogram or population pharmacokinetic models to improve the numbers of children achieving the target exposure. There are limited pharmacokinetic data for treosulfan, CY, fludarabine and alemtuzumab as HSCT conditioning in children. For post-grafting immunosuppression, mycophenolic acid (MPA) clearance may be increased in younger children (<12 years). The preferred MPA pharmacokinetic monitoring parameters and target range are still evolving in HSCT recipients. Multi-institutional trials incorporating properly powered pharmacokinetic/dynamic studies are needed to assess the effect of variability in the plasma exposure of drugs/metabolites on clinical outcomes in pediatric HSCT recipients.

Population pharmacokinetics of unbound mycophenolic acid in adult allogeneic haematopoietic cell transplantation: effect of pharmacogenetic factors

AIM

To evaluate pharmacogenetic factors as contributors to the variability of unbound mycophenolic acid (MPA) exposure in adult allogeneic haematopoietic cell transplantation (alloHCT) recipients.

METHODS

A population-based pharmacokinetic (PK) model of unbound MPA was developed using non-linear mixed-effects modelling (nonmem). Previously collected intensive unbound MPA PK data from 132 adult alloHCT recipients after oral and intravenous dosing of the prodrug mycophenolate mofetil (MMF) were used. In addition to clinical covariates, genetic polymorphisms in UGT1A8, UGT1A9, UGT2B7 and MRP2 were evaluated for their impact on unbound MPA PK.

RESULTS

Unbound MPA concentration-time data were well described by a two compartment model with first order absorption and linear elimination. For the typical patient (52 years of age, creatinine clearance 86 ml min(-1)), the median estimated values [coefficient of variation, %, (CV)] of systemic clearance, intercompartmental clearance, central and peripheral volumes of MPA were 1610 l h(-1) (37.4%), 541 l h(-1) (75.6%), 1230 l (37.5%), and 6140 l (120%), respectively. After oral dosing, bioavailability was low (0.56) and highly variable (CV 46%). No genetic polymorphisms tested significantly explained the variability among individuals. Creatinine clearance was a small but significant predictor of unbound MPA CL. No other clinical covariates impacted unbound MPA PK.

CONCLUSIONS

In adult alloHCT recipients, variability in unbound MPA AUC was large and remained largely unexplained even with the inclusion of pharmacogenetic information. Targeting unbound MPA AUC in a patient will require therapeutic drug monitoring.

A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for monitoring drug exposure in hematopoietic stem cell transplant recipients

A liquid chromatography-tandem mass spectrometry method was developed for the quantification of circulating levels of multiple immunosuppressant drugs including cyclosporine (CsA), tacrolimus, methotrexate (Mtx), prednisone, prednisolone, methylprednisone, total and free mycophenolic acid (MPA), as well as MPA phenolic (MPAG) and acyl (AcMPAG) glucuronide metabolites. Linearity, precision and accuracy were validated within the typical therapeutic range of concentrations for each compound. The assay was linear over 0.125-25ng/mL for tacrolimus, 1-500ng/mL for prednisone/methylprednisone, 2-400ng/mL for Mtx, 2-1000ng/mL for prednisolone and from 7.5 to 1500ng/mL for CsA with the lowest limit of quantification (LLOQ) being 0.125, 1.00, 2.00, 2.00 and 7.5ng/mL, respectively. The calibration curve concentrations for MPA and MPAG ranged from 50 to 50,000ng/mL (LLOQ: 50ng/mL) and 10 to 10,000ng/mL (LLOQ: 10ng/mL) for AcMPAG. Mean recoveries in blood and plasma were 84%±5.7%. The method could measure individual drugs with high sensitivity, accuracy (bias≤14%), and reproducibility (CV≤12.8%). Its clinical application was validated by measuring levels of these drugs in samples obtained from hematopoietic stem cell transplant recipients treated with combined immunosuppressive drug therapy. Our results indicate that this approach is suitable for simultaneous determination of in vivo levels of immunosuppressive drugs commonly used in combined therapies.

A limited sampling strategy for estimation of the area under the curve (0 to 8 hours) of mycophenolic acid administered three times daily to liver transplant recipients

OBJECTIVES

Gastrointestinal side-effects caused by mycophenolic acid (MPA) are frequent in liver transplant recipients, and in these cases a switch from two to three daily doses is usually recommended. However, a limited sampling strategy for the estimation of MPA area under the curve from 0 to 8 hours (AUC(0-8h)) has not been made.

DESIGN AND METHODS

In 22 liver transplant patients who were administered MPA three times daily, the trapezoidal extrapolated MPA AUC(0-8h) values using a sampling time from 0 to 2 hours were calculated.

RESULTS

A tentative therapeutic range for MPA AUC(0-8h) of about 20-40 μg.h/mL is proposed, and in the 13 patients with supratherapeutic values the total leukocyte blood count was significantly lower than in the 9 patients with AUC(0-8h) ≤ 40 μg.h/mL (P < 0.001). Significant negative correlations were found between the total leukocyte blood count and the MPA trough levels (r = -0.458; P < 0.05), AUC(0-8h) (r = -0.479; P < 0.05), and AUC(0-2h) (r = -0.437; P < 0.05). A significant correlation was found between the trapezoidal extrapolated AUC(0-8h) and trapezoidal AUC(0-2h) results (r = 0.850; P < 0.001).

CONCLUSIONS

The trapezoidal extrapolated AUC(0-8h), and possibly trapezoidal AUC(0-2h), may be useful for routine therapeutic MPA monitoring in liver transplant recipients in which the dosing frequency is increased from twice to three times a day.

Mycophenolate pharmacokinetics and association with response to acute graft-versus-host disease treatment from the Blood and Marrow Transplant Clinical Trials Network

There are limited data as to the effectiveness of mycophenolate mofetil (MMF) plus high-dose corticosteroids for the treatment of acute graft-versus-host disease (aGVHD), and even less data regarding the pharmacokinetic disposition and exposure-response relationship of MMF in individuals with GVHD. MMF pharmacokinetics were studied in a multicenter Blood and Marrow Transplant Clinical Trials Network randomized phase II trial evaluating the effectiveness of MMF as one of 4 agents added to corticosteroids as treatment of aGVHD. Thirty-two of the patients randomized to receive MMF underwent pharmacokinetic sampling in weeks 1 and 2 were studied. Mean age was 41 +/- 13.6 years. Twenty one (65.6%), 5 (15.6%), 6 (18.8%) patients had a complete response (CR), partial response (PR) or lesser response by day 28, respectively. Twenty-five (78.1%), 2 (6.3%), 5 (15.6%) patients had a CR, PR, or other response by day 56 to treatment, respectively. Mycophenolic acid (MPA) pharmacokinetic measurements from weeks 1 and 2 did not correlate with CR at either day 28 or day 56 (P > .07); however, if the mean of weeks 1 and 2 total MPA troughs was >0.5 microg/mL or that of an unbound trough was >0.015 microg/mL, then a significantly greater proportion achieved CR + PR at days 28 and 56. CR + PR at day 28 was observed in 19 of 19 patients (100%) with a mean total trough >0.5 mg/mL, but in only 7 of 13 (54%) with a mean total trough < or =0.5 microg/mL (P = .002). Similarly, CR + PR at day 28 was seen in 15 of 15 patients (100%) with an unbound trough concentration >0.015 microg/mL, but in only 11 of 17 (65%) with an unbound trough concentration < or =0.015 microg/mL (P = .02). There was no association between the pharmacokinetic measures and risk of infection by day 90 or overall survival (OS) at day 180 postrandomization. About one-half of subjects did not achieve the favorable MPA total and unbound trough concentrations. The current practice of MMF 1 gm twice daily dosing provides low plasma concentrations in many patients. Higher doses may improve the efficacy of MMF as aGVHD therapy.

Pharmacokinetics of mycophenolic acid administered 3 times daily after hematopoietic stem cell transplantation with reduced-intensity regimen

Mycophenolate mofetil (MMF) is an immunosuppressive drug used as a prophylactic agent to prevent acute graft-versus-host disease (aGVHD) after hematopoietic stem cell transplantation (HSCT). After reduced-intensity conditioning (RIC) regimen, administration of MMF orally 3 times a day (tid) seems to be more beneficial than twice a day (bid). However, information regarding the pharmacokinetic (PK) parameters of mycophenolic acid (MPA), the active metabolite of MMF, administered in this regimen are very limited. We performed a prospective study in 15 patients for whom 3 sets of sampling were performed: at the beginning of the treatment, after 1 week, and after 1 month. Two consecutive 8-hour sets of sampling were performed at day 0 (D0) and D7. Plasma concentrations of MPA were quantified and areas under the curve for 8hours (AUC(0-8)), and maximal and through concentrations were calculated. The results show that AUC(0-8) increases between the beginning of treatment and the end of the first week, but remains stable thereafter. Moreover, a trend to lower AUC(0-8) was observed for the patients who experienced GVHD > or =2 compared to those patients who did not. The other PK parameters are not associated with pharmacodynamic events. A limited sampling strategy with Bayesian estimators is currently under investigation to confirm these data and the role of D7 AUC(0-8) as a potential target of therapeutic drug monitoring (TDM).

Evaluation of mycophenolate mofetil for initial treatment of chronic graft-versus-host disease

We conducted a double-blind, randomized multicenter trial to determine whether the addition of mycophenolate mofetil (MMF) improves the efficacy of initial systemic treatment of chronic graft-versus-host disease (GVHD). The primary endpoint was resolution of chronic GVHD and withdrawal of all systemic treatment within 2 years, without secondary treatment. Enrollment of 230 patients was planned, providing 90% power to observe a 20% difference in success rates between the 2 arms. The study was closed after 4 years because the interim estimated cumulative incidence of success for the primary endpoint was 23% among 74 patients in the MMF arm and 18% among 77 patients in the control arm, indicating a low probability of positive results for the primary endpoint after completing the study as originally planned. Analysis of secondary endpoints showed no evidence of benefit from adding MMF to the systemic regimen first used for treatment of chronic GVHD. The estimated hazard ratio of death was 1.99 (95% confidence interval, 0.9-4.3) among patients in the MMF arm compared with the control arm. MMF should not be added to the initial systemic treatment regimen for chronic GVHD. This trial was registered at www.clinicaltrials.gov as #NCT00089141 on August 4, 2004.