Mechanisms of rejection, new pharmacologic approaches, and genomic medicine are major foci for current research in transplantation. It is hoped that these new agents and personalized ...immunosuppression will provide for less toxic regimens that are effective in preventing both acute and chronic allograft rejection. Until new agents are available, practitioners must use various combinations of currently approved agents to find the best regimens for improved long-term outcomes.
A roundtable meeting to discuss the use of therapeutic drug monitoring (TDM) to guide immunosuppression with mycophenolate mofetil was held in New York in December 2004. Existing recommendations for ...the initial months after transplantation were updated. After ensuring adequate levels of mycophenolic acid (MPA, the active metabolite of mycophenolate mofetil) immediately after transplantation, optimal efficacy may require only a few dose adjustments, because intrapatient variability in exposure seems low. Recommendations based on current knowledge were made for posttransplantation sampling time points and for target MPA concentrations. Algorithms for estimating MPA exposure using limited sampling strategies were presented, and a new assay for MPA discussed. It was agreed that because of interpatient variability and the influence of concomitant immunosuppressants, TDM might help optimize outcomes, especially in patients at higher risk of rejection. The value of TDM in the general transplant population will be assessed from large, ongoing, randomized studies.
The use of direct-acting antiviral (DAA) agents against chronic hepatitis C virus (HCV) infections can result in the successful treatment of nearly all patients. Effective antiviral treatments can ...prevent the progression to cirrhosis and hepatocellular malignancy, and decrease liver-related morbidity and mortality.
Paritaprevir-ritonavir-ombitasvir and dasabuvir (PrOD), with or without ribavirin, is an all-oral regimen approved for the treatment of HCV genotype 1 infections, including patients with compensated cirrhosis. Phase 2 and 3 clinical trials demonstrated the safety and efficacy of this regimen in HCV genotype 1-infected patients who are treatment-naïve and those who have failed peginterferon/ribavirin therapy. Additional studies evaluated the use of PrOD with or without ribavirin among special populations, including patients co-infected with human immunodeficiency virus-1 and HCV, liver transplant recipients with HCV recurrence, and patients with severe renal impairment. Additionally, the combination of paritaprevir-ritonavir-ombitasvir plus ribavirin is found to be highly efficacious, and is now approved in the US, for the treatment of HCV genotype 4 infections.
The availability and use of interferon-free DAA combination regimens has resulted in a major paradigm shift in the treatment of HCV. PrOD, with or without ribavirin, is an effective, safe and tolerable treatment option.
Hepatic transplantation is a highly effective but costly treatment for end-stage hepatic dysfunction. One approach to improve efficiency in the use of scarce organs for transplantation is to identify ...preoperative factors that are associated with poor outcome posttransplantation. This may assist both in selecting patients optimal for transplantation and in identifying strategies to improve survival.
In the present work, we retrospectively reviewed consecutive liver transplants performed at the University of California at Los Angeles during a 6-year period and determined preoperative variables that were associated with outcome in primary grafts. In addition, we used the hospital's cost accounting database to determine the impact of these variables on the degree of resource use by high-risk patients.
We found five variables to have independent prognostic value in predicting graft survival after primary liver transplantation: (1) donor age, (2) recipient age, (3) donor sodium, (4) recipient creatinine, and (5) recipient ventilator requirement pretransplant. Recipient ventilator requirement and elevated creatinine were associated with significant increases in resource use during the transplant admission.
Patients at high risk for graft failure and costly transplants can be identified preoperatively by a set of parameters that are readily available, noninvasive, and inexpensive. Selection of recipients on the basis of these data would improve the efficiency of liver transplantation and reduce its cost.
Patients undergoing liver transplantation for hepatitis B–related liver disease are prone to recurrence. The mainstay of prophylaxis has been passive immunotherapy with hepatitis B immune globulin ...(HBIG). Antiviral therapy with lamivudine has proven effective in lowering hepatitis B virus (HBV) DNA and improving histology in patients with hepatitis B infection; its role in prophylaxis against hepatitis B recurrence following liver transplantation is under investigation. Viral breakthrough and resistance, however, are a significant problem with monotherapy with either HBIG or lamivudine. The efficacy of combination lamivudine/HBIG prophylaxis has not been reported. Fourteen patients underwent transplantation for decompensated liver disease owing to hepatitis B. Lamivudine (150 mg po/d) was begun before transplantation in 10 patients, including 4 who were HBV DNA–positive. In addition, 1 patient was HBV DNA–positive when transplanted. HBIG was given perioperatively and continued thereafter; treatment with lamivudine was maintained or initiated at the time of transplantation and continued indefinitely. The median follow‐up was 387 days. Actuarial 1‐year patient and graft survival was 93% (1 patient died of unrelated causes). At a median interval of 28 days following lamivudine treatment, all 5 HBV DNA–positive patients cleared HBV DNA from the serum; 1 went on to clear hepatitis B surface antigen (HBsAg), before transplantation, at day 148 of lamivudine treatment. By the highly sensitive polymerase chain reaction (PCR), at a median of 346 days (range, 130‐525 days) following transplantation, all 13 surviving patients had no detectable serum HBV DNA. Lamivudine suppresses HBV replication in patients awaiting liver transplantation. At a median follow‐up of 1.1 years, combination prophylaxis with lamivudine and HBIG prevented hepatitis B recurrence following liver transplantation.
To evaluate the variables affecting orthotopic liver transplantation (OLT) outcome for hepatitis B virus (HBV) in a large patient cohort over a 17-year period.
Historically, OLT for chronic HBV ...infection has been associated with aggressive reinfection and poor survival results. More recently, OLT outcome has been improved with the routine use of antiviral therapy with either hepatitis B immune globulin (HBIg) or lamivudine; however, HBV recurrence remains common. The authors studied the factors affecting HBV recurrence and outcome of transplantation, including the effects of combination viral prophylaxis with HBIg and lamivudine.
A retrospective review of 166 OLT recipients for chronic HBV over a 17-year period at a single center was performed. Median follow-up was 29 months. HBV recurrence was defined by HBsAg seropositivity after OLT. HBIg monotherapy was used in 28 (17%) patients, lamivudine monotherapy in 20 (12%), and HBIg and lamivudine combination in 89 (54%); 29 (17%) did not receive any HBV prophylaxis. Hepatocellular carcinoma (HCC) was present in 43 patients (26%) and urgent United Network for Organ Sharing (UNOS) status was assigned to 27 patients (16%). Univariate and multivariate analyses were performed to identify factors that affected OLT outcome.
Overall 1-, 3-, and 5-year patient survival rates were 85.8%, 73.6%, and 71.8%, respectively. As expected, HBV recurrence-free survival rates were significantly lower than overall survival rates (76.4%, 58.7%, and 48.3%). When compared with a nontreated cohort, OLT recipients receiving combination viral prophylaxis with HBIg and lamivudine showed markedly reduced HBV recurrence rates and significantly improved 1- and 3-year recurrence-free survival rates. By univariate estimates, patient survival was reduced in the presence of HCC, in the Asian population, and urgent candidates by UNOS classification. Graft loss rates were significantly increased in urgent OLT candidates, Asians, patients with pretransplant positive DNA, and in the presence of HCC. Factors that were significant by univariate analysis or thought to be clinically relevant were subjected to multivariate analysis. By multivariate estimates, urgent UNOS or presence of HCC adversely affected patient and graft survival rates, whereas combination prophylactic therapy strongly predicted improved patient and graft survival rates as well as recurrence-free survival rates.
Orthotopic liver transplantation for HBV under combination viral prophylaxis results in survival rates equivalent to other indications. Pretransplant viral replication, UNOS status, and the presence of HCC are all sensitive markers for posttransplantation outcome. Viral prophylactic therapy has effectively reduced HBV recurrence and prolonged survival outcomes. The combination of HBIg and lamivudine is the prophylactic regimen of choice.
To determine the factors affecting the outcome of orthotopic liver transplantation (OLT) for end-stage liver disease caused by hepatitis C virus (HCV) and to identify models that predict patient and ...graft survival.
The national epidemic of HCV infection has become the leading cause of hepatic failure that requires OLT. Rapidly increasing demands for OLT and depleted donor organ pools mandate appropriate selection of patients and donors. Such selection should be guided by a better understanding of the factors that influence the outcome of OLT.
The authors conducted a retrospective review of 510 patients who underwent OLT for HCV during the past decade. Seven donor, 10 recipient, and 2 operative variables that may affect outcome were dichotomized at the median for univariate screening. Factors that achieved a probability value less than 0.2 or that were thought to be relevant were entered into a stepdown Cox proportional hazard regression model.
Overall patient and graft survival rates at 1, 5, and 10 years were 84%, 68%, and 60% and 73%, 56%, and 49%, respectively. Overall median time to HCV recurrence was 34 months after transplantation. Neither HCV recurrence nor HCV-positive donor status significantly decreased patient and graft survival rates by Kaplan-Meier analysis. However, use of HCV-positive donors reduced the median time of recurrence to 22.9 months compared with 35.7 months after transplantation of HCV-negative livers. Stratification of patients into five subgroups, based on time of recurrence, revealed that early HCV recurrence was associated with significantly increased rates of patient death and graft loss. Donor, recipient, and operative variables that may affect OLT outcome were analyzed. On univariate analysis, recipient age, serum creatinine, donor length of hospital stay, donor female gender, United Network for Organ Sharing (UNOS) status of recipient, and presence of hepatocellular cancer affected the outcome of OLT. Elevation of pretransplant HCV RNA was associated with an increased risk of graft loss. Of 15 variables considered by multivariate Cox regression analysis, recipient age, UNOS status, donor gender, and log creatinine were simultaneous significant predictors for patient survival. Simultaneously significant factors for graft failure included log creatinine, log alanine transaminase, log aspartate transaminase, UNOS status, donor gender, and warm ischemia time. These variables were therefore entered into prognostic models for patient and graft survival.
The earlier the recurrence of HCV, the greater the impact on patient and graft survival. The use of HCV-positive donors may accelerate HCV recurrence, and they should be used judiciously. Patient survival at the time of transplantation is predicted by donor gender, UNOS status, serum creatinine, and recipient age. Graft survival is affected by donor gender, warm ischemia time, and pretransplant patient condition. The authors' current survival prognostic models require further multicenter validation.
Liver transplant: a primer Movahedi, Zohreh; Holt, Curtis D; Saab, Sammy
Experimental and clinical transplantation : official journal of the Middle East Society for Organ Transplantation,
06/2010, Volume:
8, Issue:
2
Journal Article
Peer reviewed
Liver transplant has been accepted as a successful therapeutic option for patients with end-stage liver disease. Patient and graft survival has incrementally increased over the past 2 decades, mainly ...because of immunosuppressive regimens. However, the nonspecific nature of immunosuppressive agents is associated with an increased risk of development of opportunistic infections, renal impairment, metabolic derangements, neurotoxicity, de novo malignancies, and recurrence of the primary disease. Immunosuppressive regimen pharmacologic classes include calcineurin inhibitors, antimetabolites, mTOR inhibitors, steroids, and antibody-based therapies. These agents affect T-cell-dependent B-cell activation, and target different sites in the T-cell activation cascade by inhibiting T-cell activation or causing T-cell depletion. The goals of immunosuppression in solid-organ transplant are to prevent allograft rejection as well as optimize allograft function, prolong patient survival, and improve patient quality of life. Therefore, it is essential to carefully select the immunosuppressive regimen that will result in significant improvements in long-term liver transplant patients' survival and quality of life.
SUMMARY
The experimental host range of Odontoglossum ringspot virus (ORSV), a member of the tobamoviruses, includes several species of Nicotiana, but not N. sylvestris. However, ORSV was able to ...replicate in protoplasts from N. sylvestris leaves. By using the green fluorescent protein (GFP) as a marker inserted into ORSV, it was found that a small number of single epidermal cells became infected in mechanically inoculated leaves, but the virus did not move cell to cell. The ORSV movement protein (MP) and coat protein (CP) were examined for their ability to effect movement by substitution into Tobacco mosaic virus (TMV) hybrids. Both proteins and the 3′ non‐translated region (NTR) of ORSV allowed movement of TMV hybrids in N. sylvestris. These results suggested that the inability of ORSV to move in N. sylvestris was due to the replicase gene or the 5′NTR. One possibility was that the replicase gene could indirectly affect movement by failing to produce subgenomic (sg) RNAs for expression of MP or CP, but this appeared not to be the case as ORSV replicated and produced MP and CP sgRNAs, both of which were translated in N. sylvestris protoplasts. Additionally, genomic RNA was encapsidated into virions in N. sylvestris protoplasts. Because the 5′NTR permitted efficient replication and production of replicase proteins, these findings suggest that the replicase of ORSV is responsible for the defect in cell‐to‐cell movement of ORSV in N. sylvestris.
OBJECTIVE:
To review the pharmacology, pharmacokinetics, clinical efficacy, adverse effects, and economic issues associated with sirolimus, the most recent immunosuppressive agent approved for kidney ...transplantation.
DATA SOURCES:
A MEDLINE search (1966–June 2000) was completed to identify primary and review articles. In addition, abstracts from recent meetings on transplantation were reviewed for information and research on sirolimus.
STUDY SELECTION AND DATA EXTRACTION:
Blinded, randomized, controlled studies were the goal, but, as with most newly approved immunosuppressive agents, a significant amount of information on sirolimus is not available in this optimal form. All articles were assessed and all pertinent information was incorporated in this review.
DATA SYNTHESIS:
Sirolimus is structurally related to the immunosuppressive agent tacrolimus, and retains a pharmacokinetic and drug interaction profile similar to that of the calcineurin inhibitors, cyclosporine and tacrolimus. However, the novel mechanism of action of sirolimus differs significantly from these agents, as does its adverse effect profile. The most significant adverse reaction is hyperlipidemia. Clinical experience with sirolimus has allowed transplant centers to expand its use into other areas of transplantation as well as certain autoimmune disorders.
CONCLUSIONS:
The definitive role of sirolimus will continue to be determined; however, sirolimus offers an excellent addition to the transplant immunosuppression armamentarium.
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