Randomized trial of tacrolimus plus mycophenolate mofetil or azathioprine versus cyclosporine oral solution (modified) plus mycophenolate mofetil after cadaveric kidney transplantation: results at 2 years.

BACKGROUND: A previous report described the 1-year results of a prospective, randomized trial designed to investigate the optimal combination of immunosuppressants in kidney transplantation. Recipients of first cadaveric kidney allografts were treated with tacrolimus+mycophenolate mofetil (MMF), cyclosporine oral solution (modified) (CsA)+MMF, or tacrolimus+azathioprine (AZA). Results at 1 year revealed that optimal efficacy and safety were achieved with a regimen containing tacrolimus+MMF. The present report describes results at 2 years. METHODS: Two hundred twenty-three recipients of first cadaveric kidney allografts were randomized to receive tacrolimus+MMF, CsA+MMF, or tacrolimus+AZA. All regimens contained corticosteroids, and antibody induction was used only in patients who experienced delayed graft function. Patients were followed up for 2 years. RESULTS: The results at 2 years corroborate and extend the findings of the previous report. Patients randomized to either treatment arm containing tacrolimus experienced improved kidney function. New-onset insulin dependence remained in four, three, and four patients in the tacrolimus+MMF, CsA+MMF, and tacrolimus+AZA treatment arms, respectively. Furthermore, patients with delayed graft function/acute tubular necrosis who were treated with tacrolimus+MMF experienced a 23% increase in allograft survival compared with patients receiving CsA+MMF (P=0.06). Patients randomized to tacrolimus+MMF received significantly lower doses of MMF compared with those administered CsA+MMF. CONCLUSIONS: All three immunosuppressive regi-mens provided excellent safety and efficacy. How-ever, the best results overall were achieved with tacrolimus+MMF. The combination may provide particular benefit to kidney allograft recipients who develop delayed graft function/acute tubular necrosis. Renal function at 2 years was better in the tacrolimus treatment groups compared with the CsA group.

Therapeutic drug monitoring of tacrolimus in pediatric liver transplant patients.

The clinical utility of tacrolimus monitoring in adults has been well documented. The present study compared tacrolimus monitoring in a pediatric population of 34 liver transplant patients in four US centers with an adult population of 111 patients in six US centers. Subjects (adult and pediatric) were evaluated, at defined intervals over 12 weeks post-transplantation (Tx), for tacrolimus trough concentrations and 12 additional laboratory chemistries. Pediatric patient and graft survival for the 12 weeks were 91% and 88%, respectively, as compared to 97% and 93%, respectively, for the adult population. The mean oral dosage of tacrolimus for pediatric patients was 0.13 +/- 0.1 mg/kg/day at week 1, increased to 0.30 +/- 0.3 mg/kg/day by week 3 and remained constant for the remainder of the study. These dosages were two- to three-fold higher than the dosage used in the adult population. In contrast, the mean whole-blood trough concentration, as determined by PRO-Tractrade mark II enzyme-linked immunosorbent assay (ELISA), decreased from 11.3 +/- 5.1 ng/mL at week 1 to 6.3 +/- 3.7 ng/mL by week 12 and was not significantly different from the trough concentration in adults. The incidence and distribution of the clinical end-points for the pediatric subjects (rejection, nephrotoxicity, death, re-Tx) were different from those observed in adults. The total percentage of pediatric subjects reaching any end-point was 74%, as compared to 54% in the adult population. These data indicate several differences between the adult and pediatric populations in their response to tacrolimus.

Clinical utility of monitoring tacrolimus blood concentrations in liver transplant patients.

The relationship between the dose of tacrolimus, trough tacrolimus blood concentration, and selected clinical endpoints (acute rejection, nephrotoxicity, and other toxicities) were examined in a prospective, multicenter clinical trial to validate the use of an enzyme-linked immunosorbent assay (ELISA) for monitoring whole-blood concentrations of tacrolimus in liver transplant patients. A total of 111 subjects from six transplant centers were evaluated over 12 weeks posttransplantation. In addition to trough tacrolimus blood concentrations, hematocrit, ALT, AST, GGTP, alkaline phosphatase, total bilirubin, serum creatinine, BUN, serum potassium, serum magnesium, blood glucose, and serum albumin were also measured. The relationship between trough tacrolimus blood concentrations and clinical endpoints was analyzed using both a logistic regression model and a Cox proportional hazard model. By logistic regression analysis, a statistically significant (p = 0.0465) relationship between increasing trough tacrolimus blood concentrations and decreasing risk of acute rejection was demonstrated over a 7-day time window. Nephrotoxicity and other toxicities also demonstrated statistically significant relationships with trough tacrolimus blood concentrations. The results of the Cox analysis were consistent with the logistic regression analysis. Using receiver operator characteristic curves, trough tacrolimus concentrations as measured by the ELISA method were able to differentiate the occurrence of nephrotoxicity and toxicity from nonevents. To minimize nephrotoxicity of tacrolimus, it is necessary to maintain trough blood concentrations below 15 ng/ml. This study demonstrates that the ELISA method used to measure tacrolimus blood concentrations in this study provides information of predictive value for managing the risk of nephrotoxicity, other toxicity, and rejection in liver transplant patients.

Compromised kidney graft rejection response in Vervet monkeys after withdrawal of immunosuppressants tacrolimus and sirolimus.

BACKGROUND: In nonprimates, organ allografts are often not rejected after withdrawal of immunosuppression. In this study, we examined whether such a phenomenon also occurs in primates. METHODS: Vervet monkeys were transplanted with renal allografts and treated for 60 days with tacrolimus, or tacrolimus plus sirolimus. The drugs were totally withdrawn on day 61. The survival of the monkeys was monitored, and their response to donor- or third party-derived alloantigens was examined in vivo and in vitro. RESULTS: The majority (80-100%) of the grafts survived for at least additional 30 days with no signs of acute rejection. The compromised rejection is donor-specific, because recipient monkeys failed to reject a donor-derived skin graft, but a third-party skin graft was rejected. In vitro mixed lymphocyte reaction and interleukin-2 production in the mixed lymphocyte reaction between the recipients and their donors or between the recipients and a third party had no discernable patterns, and thus did not reflect the in vivo status of the immune system. Although the recipients could not reject the graft acutely after drug withdrawal, the kidney grafts and the donor-derived skin grafts had pathological findings of chronic rejection. CONCLUSIONS: The rejection response of the monkeys to an established graft after withdrawal of immunosuppression is compromised. The compromised rejection is specific and is not due to a permanent alteration of the immune system by the initial drug treatment. The allografts are not inert but have low levels of interaction with the recipient immune system.

Effect of tacrolimus (FK506) and sirolimus (rapamycin) mono- and combination therapy in prolongation of renal allograft survival in the monkey.

BACKGROUND: Our previous studies confirmed that tacrolimus (FK506) and sirolimus [rapamycin (RAPA)], in combination, are not antagonistic but are synergistic in the prolongation of heart and small bowel grafts in the rodent. The aim of this study was to confirm further the synergistic effect of combined FK506 and RAPA in the more clinically relevant model, kidney transplantation in monkeys. METHODS: A total of 60 male Vervet monkeys were randomly assigned to 10 groups (n> or =5). Monkeys with renal allografts were treated with different doses of FK506 and/or RAPA orally for 60 days. Graft survival, body weight, clinical biochemistry determinations, oral glucose tolerance test, trough levels of the two drugs, and histopathology were investigated. RESULTS: Low doses of FK506 (1 or 4 mg/kg) combined with RAPA (0.5 mg/kg) produced synergistic effect in the prolongation of renal graft survival [combination index (CI) = 0.292, 0.565]. There were no additive or synergistic drug-associated toxicities such as hyperglycemia, nephrotoxicity, and hyperlipidemia. There also was no pharmacological antagonism. CONCLUSION: Concomitant therapy of low-dose (drug-optimal) FK506 and RAPA produced a synergistic effect in the prolongation of kidney allograft survival in Vervet monkeys without additive drug-associated toxicities.

Randomized trial of tacrolimus (Prograf) in combination with azathioprine or mycophenolate mofetil versus cyclosporine (Neoral) with mycophenolate mofetil after cadaveric kidney transplantation.

BACKGROUND: Our clinical trial was designed to investigate the optimal combination of immunosuppressants for renal transplantation. METHODS: A randomized three-arm, parallel group, open label, prospective study was performed at 15 North American centers to compare three immunosuppressive regimens: tacrolimus + azathioprine (AZA) versus cyclosporine (Neoral) + mycophenolate mofetil (MMF) versus tacrolimus + MMF. All patients were first cadaveric kidney transplants receiving the same maintenance corticosteroid regimen. Only patients with delayed graft function (32%) received antilymphocyte induction. A total of 223 patients were randomized, transplanted, and followed for 1 year. RESULTS: There were no significant differences in baseline demography between the three treatment groups. At 1 year the results are as follows: acute rejection 17% (95% confidence interval 9%, 26%) in tacrolimus + AZA; 20% (confidence interval 11%, 29%) in cyclosporine + MMF; and 15% (confidence interval 7%, 24%) in tacrolimus + MMF. The incidence of steroid resistant rejection requiring antilymphocyte therapy was 12% in the tacrolimus + AZA group, 11% in the cyclosporine + MMF group, and 4% in the tacrolimus + MMF group. There were no significant differences in overall patient or graft survival. Tacrolimus-treated patients had a lower incidence of hyperlipidemia through 6 months posttransplant. The incidence of posttransplant diabetes mellitus requiring insulin was 14% in the tacrolimus + AZA group, 7% in the cyclosporine + MMF and 7% in the tacrolimus + MMF groups. CONCLUSIONS: All regimens yielded similar acute rejection rates and graft survival, but the tacrolimus + MMF regimen was associated with the lowest rate of steroid resistant rejection requiring antilymphocyte therapy.

Tacrolimus vs. cyclosporine immunosuppression: results in advanced-stage disease compared with historical controls treated exclusively with cyclosporine.

A phase HI comparative trial of tacrolimus- vs. cyclosporine-based graft-vs.-host disease (GVHD) prophylaxis for human leukocyte antigen (HLA)-identical sibling bone marrow transplantation showed less GVHD but poorer survival in the tacrolimus arm. To test the comparability of the two treatment arms with respect to baseline survival prognosis, a matched control study using exclusively cyclosporine-treated patients from the International Bone Marrow Transplant Registry (IBMTR) database was performed. Controls were matched (2:1) based on age (within 5 years), disease, and pretransplant disease status. Two-year survival for tacrolimus-treated clinical trial patients was similar to that of their cyclosporine-treated matched controls (27 and 24%, respectively), and 2-year survival of the cyclosporine-treated clinical trial patients was similar to that of their cyclosporine-treated matched IBMTR controls (42 and 45%, respectively). Consistent with the clinical trial results, the cyclosporine-treated IBMTR controls matched to the tacrolimus group had significantly poorer 2-year survival than the cyclosporine-treated IBMTR controls matched to the cyclosporine group (24 and 45%, respectively; p < 0.01). No significant difference was seen in GVHD between the cyclosporine-treated clinical trial patients and their matched controls; however, the tacrolimus-treated clinical trial patients had significantly less GVHD than their cyclosporine-treated IBMTR controls (p < 0.01). These results support the hypothesis that the survival difference in the phase III trial resulted from an imbalance in the underlying risk factors for death in the two groups rather than from the randomized immunosuppressive regimen.

Relationship of tacrolimus whole blood levels to efficacy and safety outcomes after unrelated donor marrow transplantation.

Tacrolimus has proved effective for preventing acute graft-vs.-host disease (GVHD) after unrelated donor marrow transplantation, but the therapeutic window is apparently narrow. Therapeutic drug monitoring could potentially be used to guide dose modifications, but the optimal target range of tacrolimus blood concentrations is unknown. We determined whether acute GVHD and renal dysfunction correlated with tacrolimus whole blood levels as measured by the IMx assay. Data were analyzed for 97 adults treated in a multicenter trial of tacrolimus and methotrexate or methylprednisolone as GVHD prophylaxis after unrelated donor marrow transplantation. The rate of grades II-IV GVHD was 49%; 81% of patients had a doubling of the serum creatinine; and 61% had a serum creatinine <2 mg/dL. The initial tacrolimus target range for the clinical trial was 10-60 ng/mL. Tacrolimus blood levels were averaged over a 14-day period, and Cox models were used with averaged blood levels as a time-dependent covariate. No significant change was observed in the risks of acute GVHD, doubling of creatinine, need for dialysis, or death over a tacrolimus blood level range of 5-40 ng/mL, but there was a direct correlation between risk of developing a creatinine <2 mg/dL and increasing tacrolimus blood levels (4.7% increased risk for each 1 ng/mL increase in blood concentration, p < 0.001). When the tacrolimus level exceeded 20 ng/mL, there was a 2.2-fold increase in the rate of renal toxicity (p < 0.001), a trend for an increase in mortality (relative risk 3.9, p=0.08), and no impact on the risk of GVHD. This analysis supports 10-20 ng/mL as the therapeutic range of tacrolimus whole blood steady state or trough levels for unrelated donor marrow transplantation.

Phase III study comparing methotrexate and tacrolimus (prograf, FK506) with methotrexate and cyclosporine for graft-versus-host disease prophylaxis after HLA-identical sibling bone marrow transplantation.

We report the results of a phase III open-label, randomized, multicenter trial comparing tacrolimus/methotrexate to cyclosporine/methotrexate for graft-versus-host disease (GVHD) prophylaxis after HLA-identical sibling marrow transplantation in patients with hematologic malignancy. The primary objective of this study was to compare the incidence of moderate to severe (grade II-IV) acute GVHD. Secondary objectives were to compare the relapse rate, disease-free survival, overall survival, and the incidence of chronic GVHD. Patients were stratified according to age (<40 v >/=40) and for male recipients of a marrow graft from an alloimmunized female. There was a significantly greater proportion of patients with advanced disease randomized to tacrolimus arm (P = . 02). The incidence of grade II-IV acute GVHD was significantly lower in patients who received tacrolimus than patients in the cyclosporine group (31.9% and 44.4%, respectively; P = .01). The incidence of grade III-IV acute GVHD was similar, 17.1% in cyclosporine group and 13.3% in the tacrolimus group. There was no difference in the incidence of chronic GVHD between the tacrolimus and the cyclosporine group (55.9% and 49.4%, respectively; P = .8). However, there was a significantly higher proportion of patients in the cyclosporine group who had clinical extensive chronic GVHD (P = . 03). The relapse rates of the two groups were similar. The patients in the cyclosporine arm had a significantly better 2-year disease-free survival and overall survival than patients in the tacrolimus arm, 50.4% versus 40.5% (P = .01) and 57.2% versus 46.9% (P = .02), respectively. The significant difference in the overall and disease-free survival was largely the result of the patients with advanced disease, 24.8% with tacrolimus versus 41.7% with cyclosporine (P = .006) and 20.4% with tacrolimus versus 28% with cyclosporine (P = .007), respectively. There was a higher frequency of deaths from regimen-related toxicity in patients with advanced disease who received tacrolimus. There was no difference in the disease-free and overall survival in patients with nonadvanced disease. These results show the superiority of tacrolimus/methotrexate over cyclosporine/methotrexate in the prevention of grade II-IV acute GVHD with no difference in disease-free or overall survival in patients with nonadvanced disease. The survival disadvantage in advanced disease patients receiving tacrolimus warrants further investigation.

Relationship of tacrolimus (FK506) whole blood concentrations and efficacy and safety after HLA-identical sibling bone marrow transplantation.

A randomized clinical trial comparing tacrolimus with cyclosporine, both with short-course methotrexate, as prophylaxis against graft-vs.-host disease (GVHD) in allogeneic HLA-matched sibling bone marrow transplant patients was conducted. Cyclosporine was dosed to achieve a target concentration range between 150 and 450 ng/mL during the first 8 weeks after transplant. For tacrolimus, the target concentration range was 10-30 ng/mL during the first 8 weeks after transplant. A gradual tapering schedule of 20% per month during months 3-6 was then conducted for patients in both treatment arms. The efficacy of the immunosuppressive regimen was determined by the rate of acute GVHD grades II-IV The toxicity of the immunosuppressive regimen was determined by the occurrence of the creatinine exceeding 2 mg/dL, the creatinine doubling the baseline value, or the necessity for hemodialysis. Correlations between blood concentrations and efficacy and toxicity parameters were assessed. For both tacrolimus and cyclosporine, increasing blood concentrations were associated with greater renal dysfunction. For cyclosporine, there was a nonsignificant trend to an increased incidence of grades II-IV acute GVHD with lower cyclosporine blood concentrations (<300 ng/mL). In contrast, there did not appear to be a relationship between the blood concentrations of tacrolimus and the occurrence of acute GVHD. This suggests that optimization of efficacy while minimizing the risk for nephrotoxicity could be achieved by dosing tacrolimus to a targeted range between 10 and 20 ng/mL.

Glucocorticoids fail to enhance the effect of FK506 and methotrexate in prevention of graft-versus-host disease after DLA-nonidentical, unrelated marrow transplantation.

Several steroid receptor-associated heat shock proteins can bind to FK506 as immunophilins. This has led to speculation that the steroid receptor and immunophilin signal transduction pathways are functionally interrelated. Indeed, in vitro work showed that FK506 treatment of intact L929 cells which were stably transfected with various reporter plasmids resulted in a potentiation of glucocorticoid hormone-induced glucocorticoid receptor-mediated gene transcription. These findings have raised the possibility of additive or synergistic immunosuppressive effects of FK506 and glucocorticoids. We tested this hypothesis in a canine model of GVHD prevention. Two groups of dogs were given 9.2 Gy total body irradiation followed by hematopoietic grafts from unrelated DLA-nonidentical donors. Among the first group of four recipients which were given FK506 and glucocorticoids, one rejected the graft, while three developed acute GVHD and died from associated complications between days 14 and 34. In the second group of nine recipients which were given FK506, glucocorticoids and methotrexate (MTX), only one dog became a long-term survivor while eight dogs died between days 21-114 with GVHD (n = 5) or FK506-associated toxicities (n = 3). Thus, addition of glucocorticoids to FK506 or FK506/MTX showed neither synergistic nor additive effects with respect to GVHD prevention in this model, and no survival advantages were seen compared to previously reported results with FK506 alone or FK506 and MTX in combination, respectively.

The outcome of unrelated donor bone marrow transplantation in patients with hematologic malignancies using tacrolimus (FK506) and low dose methotrexate for graft-versus-host disease prophylaxis.

Initial studies of FK506 combined with methotrexate (MTX) in patients receiving unrelated donor BMT have demonstrated a possible-decrease in the incidence of severe GVHD but high rates of severe stomatitis and nephrotoxicity. With this background, we undertook a pilot study evaluating FK506 in combination with a lower than usual dose of MTX in an attempt to improve the tolerability of this immunoprophylaxis regimen. Between July 1993 and October 1994, 26 consecutive adults receiving unrelated donor BMT at Emory University Hospital were enrolled on this study. All patients received FK506 intravenously at an initial dose of 0.03 mg/kg/day beginning day -1 and continuing until oral FK506 was tolerated. Patients also received MTX intravenously at 5 mg/m2 on days 1, 3, 6, and 11. The preparative regimen administered to all but one patient included cyclophosphamide at 200 mg/kg over 4 days followed by total body irradiation (TBI) at 1400 cGy in twice daily fractions over 4 days. The median age of patients was 31 years (range: 19 to 52). Sixteen donor/recipient pairs were matched for HLA-A, -B, and -DR by serology and molecular typing. Ten paris were minor mismatches at either class I or class II. Twenty-two of 26 patients (85%) completed four doses of MTX on schedule. Nephrotoxicity was the most common adverse event associated with the administration of FK506: 88% of patients experienced a doubling of their serum creatinine. One patient died of central nervous system hemorrhage prior to engraftment. Twenty-four of the remaining 25 patients (96%) engrafted. Fourteen of 24 patients (50%) evaluable developed grades 2-4 acute GVHD. The rate of severe (grades 3-4) acute GVHD was 25%. Chronic GVHD developed in 11 of 20 (55%) evaluable patients. At a median follow-up of 461 days, 14 patients (54%) are alive. All are relapse-free with a median Karnofsky performance status of 90% (range: 70-100%). The cumulative probability of 2-year disease-free survival is 50% (95% confidence interval [CI]: 0.33 to 0.77); for low risk patients 67% (95% CI: 0.47 to 0.95) and for high risk patients 23% (95% CI: 0.049 to 1.00). These preliminary data indicate that FK506-based immunosuppression following unrelated donor BMT is effective in preventing severe acute GVHD and warrants comparison to CSA-based regimens.

Tacrolimus (FK506) and sirolimus (rapamycin) in combination are not antagonistic but produce extended graft survival in cardiac transplantation in the rat.

Combined use of tacrolimus (FK506) with sirolimus (rapamycin [RAPA]) was examined in a model of vascularized heart allograft in the rat. For prevention of acute rejection, three different combinations of low doses of FK506 and RAPA from day 1 up to day 14 after transplantation produced significantly longer cardiac allograft survival than each agent alone (P<0.05). Identical results were observed in a model of reversal of ongoing acute rejection, where two combinations of low doses of FK506 and RAPA from day 4 up to day 18 after surgery also demonstrated significantly longer graft survival than each immunosuppressant alone (P<0.05). All the low-dose-treated groups in these two models presented significantly longer heart graft survival than naive controls (P<0.05), confirming that both agents are potent immunosuppressants in the models chosen. These results also indicate that, in contrast with in vitro studies, the combined use of FK506 and RAPA in vivo did not produce antagonism, but rather had synergistic effect in prolonging the allograft survival as compared with each agent alone. It appears likely that the abundance of FKBP-12 available for binding in vivo prevents inhibitive competition of the two agents for their receptor.

FK506 in combination with methotrexate for the prevention of graft-versus-host disease after marrow transplantation from matched unrelated donors.

The safety and potential efficacy of FK506 in combination with a short course of methotrexate (MTX) for the prevention of acute graft-versus-host disease (GVHD) after marrow transplantation from HLA-matched unrelated donors was evaluated in a single-arm Phase II study conducted at two centers. Forty-three patients, 15 to 54 (median 41) years of age, were transplanted for hematologic malignancies. Thirty-seven of 43 evaluable patients had evidence of sustained marrow engraftment. Five patients died before day 17 after transplantation. The median time to an absolute neutrophil count of > 0.5 x 10(5)/L was 21 (range, 14 to 30) days. Nephrotoxicity (serum creatinine concentration > 2 mg/dL or doubling of baseline) occurred in 32 patients (74% cumulative incidence during the first 100 days after transplant). Other adverse effects included hypertension (n = 27), hyperglycemia (n = 27), neurotoxicity (n = 9) and thrombotic thrombocytopenic purpura (n = 2). Severe veno-occlusive disease of the liver occurred in 9 (21%) of the 43 patients. Eighteen patients (42%) developed grades II to IV acute GVHD and five (12%) developed grades III to IV acute GVHD. Twelve of 25 evaluable patients developed extensive chronic GVHD within 1 year of marrow transplantation resulting in an estimate of the probability of developing this complication of 48%. The cumulative incidence of transplant-related mortality during the first 100 days was 37%. Kaplan-Meier estimates of disease-free survival at 2 years for good-risk, poor-risk, and all patients were 65%, 4%, and 32%, respectively. FK506 in combination with a short course of MTX appears active in preventing acute GVHD after marrow transplantation from unrelated donors. Further studies comparing the combination of FK506 and MTX with cyclosporine and MTX for the prevention of acute GVHD are warranted.

Relationship of FK506 whole blood concentrations and efficacy and toxicity after liver and kidney transplantation.

FK506 (tacrolimus) is a safe and effective immunosuppressant for the prevention of organ rejection after organ transplantation. FK506 has a relatively narrow therapeutic index and the correlation of dose to blood concentration is poor as a result of moderate variability in pharmacokinetic parameters between patients. Therapeutic monitoring of whole blood FK506 drug concentrations has been used in an effort to determine whether a relationship exists between concentrations of FK506 in the blood and the development of toxicity or the risk for organ rejection. An analysis of the relationship between FK506 blood levels and the occurrence of toxicity and rejection was carried out using data from four recent clinical trials. Trough FK506 levels within a 7-day window before the onset of rejection or toxicity were analyzed using logistic regression models. In kidney transplant patients (n=92), a significant correlation between FK506 levels and the incidence of both toxicity (P=0.01) and rejection (P=0.02) was seen. In liver transplant patients from three clinical trials, FK506 levels correlated well with the incidence of toxicity (P < or = 0.01); however, there was no significant relationship between FK506 levels and the incidence of rejection. It is concluded that therapeutic monitoring of whole blood FK506 levels may be useful for minimizing the risks of both toxicity and rejection in kidney transplant patients and for minimizing the risk of toxicity in liver transplant recipients.

FK506 (Tacrolimus) monotherapy for prevention of graft-versus-host disease after histocompatible sibling allogenic bone marrow transplantation.

FK506 (Tacrolimus) is an immunosuppressive drug that blocks the activation of antigen-specific T lymphocytes, a major component in the pathogenesis of graft-versus-host disease (GVHD). This study was designed to obtain first estimates of the safety and efficacy of FK506 monotherapy in the prevention of GVHD following HLA-identical sibling marrow transplantation. Additionally, a subset of patients was studied to define the pharmacokinetic profile of FK506. Twenty-seven adult patients with leukemia or myelodysplasia received FK506 starting the day before transplant at a dose of 0.04 mg/kg/d by continuous intravenous infusion. When clinically possible, FK506 was given orally in two divided doses starting at five times the daily intravenous dose. FK506 doses were adjusted to target a steady state or trough blood level between 10 to 30 ng/mL. These patients were followed for 6 months posttransplant. All patients had sustained marrow engraftment. Frequently noted adverse events included reversible renal dysfunction, diarrhea, fever, nausea, vomiting, and headache. Most patients required FK506 dose reductions associated with elevated serum creatinine. Two (7%) patients relapsed, one of whom died of the disease within the 6-month study period. A second patient died due to pulmonary mucor. Whole blood pharmacokinetic parameters indicated a half-life of 18.2 +/- 12.1 hours; volume of distribution of 1.67 +/- 1.02 L/kg; clearance of 71 +/- 34 mL/h/kg; and bioavailability of 32 +/- 24%. Eleven of 27 (41%) patients developed grade II to IV acute GVHD, including 10 grade II and one grade III. Six of 24 (25%) evaluable patients developed chronic GVHD. These data indicate that FK506 monotherapy has activity in preventing GVHD. Further studies of FK506 with lower doses to improve tolerability and in combination with other immunosuppressants to augment efficacy are warranted.

Tacrolimus (FK506) and methotrexate regimens to prevent graft-versus-host disease after unrelated dog leukocyte antigen (DLA) nonidentical marrow transplantation.

We previously reported an synergism between methotrexate and tacrolimus (FK506) in preventing graft-versus-host disease (GVHD) in dogs given DLA-nonidentical unrelated marrow grafts after 9.2 Gy of total body irradiation (TBI). Methotrexate was given at 0.4 mg/kg i.v. on days 1, 3, 6 and 11 and FK506 at 0.15 mg/kg/day i.m. on days 0-8 and 0.5 mg/kg/day orally on days 9-90. Half of the dogs became long-term survivors. A major toxicity was gastrointestinal, and 25% of dogs died with intussusception. The current study addresses the problem of intussusception by making changes in drug doses used. In one group of dogs, FK506 was reduced to 0.075 mg/kg i.m. on days 1-8, while methotrexate was administered per original schedule. In a second group, methotrexate was reduced to a single dose on day 7, while FK506 was either administered per the original or reduced-dose schedule. None of the 17 current dogs developed intussusception, however, all but two dogs died with GVHD (n = 12) or graft failure (n = 3). Only two dogs survived after transient GVHD. Results show that there is little room for maneuvering FK506 or methotrexate doses, and hopes of reducing gastrointestinal toxicity by dose modifications while retaining the ability to prevent GVHD were not fulfilled.