Thymoglobulin induction in heart transplantation: patient selection and implications for maintenance immunosuppression

Does the induction immunotherapy (basiliximab) influence the early acute cellular rejection index after orthotopic heart transplantation?- Preliminary assessment report

The study aimed to determine the influence of induction therapy on the acute cellular rejection (ACR) index in adult heart transplant recipients during the one-year observation. The study population consisted of 256 consecutive adult patients (pts), aged 51.5 (±11.9) years, 199 (77%) men treated with orthotopic heart transplantation (OHT) in the period between 2015 and 2020 in a single high-volume heart transplant center. The endomyocardial biopsies (EMBs) were performed according to the protocol consisting of 7 protocolary EMBs for up to 3 months and 10 EMBs for up to one year after OHT. The rejection index (ACRI) was calculated as the number of scheduled EMBs with the ACR ≥ 2 divided by the total number of protocolary EMBs. The study population was divided into two groups according to the application of basiliximab. The total number of pts. who received basiliximab was 10 (3.9%). The main indications for the usage of the induction therapy were heart retransplantation, mechanical circulatory support (MCS), severe renal insufficiency (eGFR <30 mL/min/1.73 m2), and a panel of reactive antibody (PRA) > 10%. In the group with induction, the mean age was 49 (±14) years; 3 (30%) patients had the MCS prior to OHT, and 3 (30%) patients had heart retransplantation. Four (40%) patients had diabetes mellitus, and 4 (40%) patients had severe renal insufficiency. As maintenance therapy during the observation period, tacrolimus was given to 10 (100%) patients, everolimus to 2 (20%) patients, and MPA to 9 (90%) patients. In the group with no induction, the mean age was 51.8 (±12) years, MCS was used in 56 (23%) patients, 2 (0.8%) patients were retransplanted; 10 (4%) patients had eGFR <30 mL/min/1.73 m2 and 58 (24%) patients had diabetes. Tacrolimus was administered to 243 (99%) patients, cyclosporine to 3 (1%), everolimus to 40 (16%), and mycophenolate to 245 (99.6%) heart recipients. The median one-year ACRI was 0.0, IQR:0.0-0.08 in the group with induction vs. 0.077, IQR: 0.0-0.154 with no induction; p = 0.11. ACRI up to three months was significantly higher in the entire cohort in comparison to up to one year (P < 0.01). The multivariate analysis showed that only everolimus implementation and younger age at the time of transplant influenced patients' mortality rate (P < 0.01). Significant graft rejections (≥ 2R ISHLT) are most common in the first three months after OHT. Patients who are initially at high risk of significant cellular rejection may benefit from induction therapy.

Incidence, risk factors, and clinical outcomes of HBV reactivation in non-liver solid organ transplant recipients with resolved HBV infection: A systematic review and meta-analysis

BACKGROUND

Current guidelines do not recommend routine antiviral prophylaxis to prevent hepatitis B virus (HBV) reactivation in non-liver solid organ transplant (SOT) recipients with resolved HBV infection, even in anti-hepatitis B surface antigen (anti-HBs)-negative recipients and those receiving intense immunosuppression. This systematic review and meta-analysis aimed to determine the incidence, risk factors, and clinical outcomes of HBV reactivation in non-liver SOT recipients.

METHODS AND FINDINGS

Three databases (PubMed, Embase, and Cochrane Library) were systematically searched up to December 31, 2022. Clinical studies reporting HBV reactivation in non-liver SOT recipients were included. Case reports, case series, and cohort studies with a sample size of less than 10 patients were excluded. Random-effects analysis was used for all meta-analyses. We included 2,913 non-liver SOT recipients with resolved HBV infection from 16 retrospective cohort studies in the analysis. The overall HBV reactivation rate was 2.5% (76/2,913; 95% confidence interval [95% CI 1.6%, 3.6%]; I2 = 55.0%). Higher rates of reactivation were observed in recipients with negative anti-HBs (34/421; 7.8%; 95% CI [5.2%, 10.9%]; I2 = 36.0%) by pooling 6 studies, experiencing acute rejection (13/266; 5.8%; 95% CI [2.3%, 14.5%]; I2 = 63.2%) by pooling 3 studies, receiving ABO blood type-incompatible transplantation (8/111; 7.0%; 95% CI [2.9%, 12.7%]; I2 = 0%) by pooling 3 studies, receiving rituximab (10/133; 7.3%; 95% CI [3.4%, 12.6%]; I2 = 0%) by pooling 3 studies, and receiving anti-thymocyte immunoglobulin (ATG, 25/504; 4.9%; 95% CI [2.5%, 8.1%]; I2 = 49.0%) by pooling 4 studies. Among recipients with post-transplant HBV reactivation, 11.0% (7/52; 95% CI [4.0%, 20.8%]; I2 = 0.3%) developed HBV-related hepatic failure, and 11.0% (7/52; 95% CI [4.0%, 20.8%]; I2 = 0.3%) had HBV-related death. Negative anti-HBs (crude odds ratio [OR] 5.05; 95% CI [2.83, 9.00]; p < 0.001; I2 = 0%), ABO blood type-incompatible transplantation (crude OR 2.62; 95% CI [1.05, 6.04]; p = 0.040; I2 = 0%), history of acute rejection (crude OR 2.37; 95% CI [1.13, 4.97]; p = 0.022; I2 = 0%), ATG use (crude OR 3.19; 95% CI [1.48, 6.87]; p = 0.003; I2 = 0%), and rituximab use (crude OR 3.16; 95% CI [1.24, 8.06]; p = 0.016; I2 = 0%) increased the risk of reactivation. Adjusted analyses reported similar results. Limitations include moderate heterogeneity in the meta-analyses and that most studies were conducted in kidney transplant recipients.

CONCLUSIONS

Non-liver SOT recipients with resolved HBV infection have a high risk of HBV-related hepatic failure and HBV-related death if HBV reactivation occurs. Potential risk factors for HBV reactivation include rituximab use, anti-thymocyte immunoglobulin use, anti-HBs negative status, acute rejection history, and ABO blood type-incompatible transplantation. Further research on monitoring and routine antiviral prophylaxis of non-liver SOT recipients at higher risk of HBV reactivation is required.

Antithymocyte Globulin Inhibits CD8+ T Cell Effector Functions via the Paracrine Induction of PDL-1 on Monocytes

BACKGROUND

Antithymocyte globulins (ATG) are T cell-depleting antibodies used in solid organ transplantation for induction therapy in sensitized patients with a high risk of graft rejection. Previously described effects besides the depletion of T cells have suggested additional modes of action and identified further cellular targets.

METHODS

We examined the transcriptional changes arising in immune cells from human blood after ex vivo stimulation with ATG at the single-cell level to uncover additional mechanisms by which ATG regulates T cell activity and effector functions.

FINDINGS

Analysis of the paracrine factors present in the plasma of ATG-treated whole blood revealed high levels of chemokines and cytokines, including interferon-γ (IFN-γ). Furthermore, we identified an increase in the surface expression of the programmed death ligand 1 (PDL-1) on monocytes mediated by the released paracrine factors. In addition, we showed that this induction is dependent on the activation of JAK/STAT signaling via the binding of IFN-γ to interferon-γ receptor 1 (IFN-γR1). Lastly, we demonstrated that the modulation of the immune regulatory axis of programmed cell death protein 1 (PD1) on activated CD8⁺ T cells with PDL-1 found on monocytes mediated by ATG potently inhibits effector functions including the proliferation and granzyme B release of activated T cells.

INTERPRETATION

Together, our findings represent a novel mode of action by which ATG exerts its immunosuppressive effects.

Racial and socioeconomic disparities in pediatric heart transplant outcomes in the era of anti-thymocyte globulin induction

BACKGROUND

Black race is associated with worse outcomes across solid organ transplantation. Augmenting immunosuppression through antithymocyte globulin (ATG) induction may mitigate organ rejection and graft loss. We investigated whether racial and socioeconomic outcome disparities persist in children receiving ATG induction.

METHODS

Using the Pediatric Heart Transplant Society registry, we compared outcomes in Black and White children who underwent heart transplant with ATG induction between 2000 and 2020. The primary outcomes of treated rejection, rejection with hemodynamic compromise (HC), and graft loss (death or re-transplant). We explored the association of these outcomes with race and socioeconomic disparity, assessed using a neighborhood deprivation index [NDI] score at 1-year post-transplant (high NDI score implies more socioeconomic disadvantage).

RESULTS

The study cohort included 1,719 ATG-induced pediatric heart transplant recipients (22% Black, 78% White). There was no difference in first year treated rejection (Black 24.5%, White 28.1%, p = 0.2). During 10 year follow up, the risk of treated rejection was similar; however, Black recipients were at higher risk of HC rejection (p = 0.009) and graft loss (p = 0.02). Black recipients had a higher mean NDI score (p < 0.001). Graft loss conditional on 1-year survival was associated with high NDI score in both White and Black recipients (p < 0.0001). In a multivariable Cox model, both high NDI score (HR 1.97, 95% CI 1.23-3.17) and Black race (HR 2.22, 95% CI 1.40-3.53) were associated with graft loss.

CONCLUSION

Black race and socioeconomic disadvantage remain associated with late HC rejection and graft loss in children with ATG induction. These disparities represent important opportunities to improve long term transplant outcomes.

Kidney disease in non-kidney solid organ transplantation

Kidney disease after non-kidney solid organ transplantation (NKSOT) is a common post-transplant complication associated with deleterious outcomes. Kidney disease, both acute kidney injury and chronic kidney disease (CKD) alike, emanates from multifactorial, summative pre-, peri- and post-transplant events. Several factors leading to kidney disease are shared amongst solid organ transplantation in addition to distinct mechanisms unique to individual transplant types. The aim of this review is to summarize the current literature describing kidney disease in NKSOT. We conducted a narrative review of pertinent studies on the subject, limiting our search to full text studies in the English language. Kidney disease after NKSOT is prevalent, particularly in intestinal and lung transplantation. Management strategies in the peri-operative and post-transplant periods including proteinuria management, calcineurin-inhibitor minimization/ sparing approaches, and nephrology referral can counteract CKD progression and/or aid in subsequent kidney after solid organ transplantation. Kidney disease after NKSOT is an important consideration in organ allocation practices, ethics of transplantation. Kidney disease after SOT is an incipient condition demanding further inquiry. While some truths have been revealed about this chronic disease, as we have aimed to describe in this review, continued multidisciplinary efforts are needed more than ever to combat this threat to patient and allograft survival.

Retrospective Evaluation of Rabbit Antithymocyte Globulin Induction in Heart Transplant Patients

The dosing intensity of antithymocyte globulin as induction therapy in heart transplantation remains controversial. We sought to evaluate the efficacy and safety of rabbit antithymocyte globulin at a total dose of 4.5 mg/kg compared with <4.5 mg/kg.

Extracorporeal Photopheresis With Low-Dose Immunosuppression in High-Risk Heart Transplant Patients-A Pilot Study

In severely ill patients undergoing urgent heart transplant (HTX), immunosuppression carries high risks of infection, malignancy, and death. Low-dose immunosuppressive protocols have higher rejection rates. We combined extracorporeal photopheresis (ECP), an established therapy for acute rejection, with reduced-intensity immunosuppression. Twenty-eight high-risk patients (13 with high risk of infection due to infection at the time of transplant, 7 bridging to transplant via extracorporeal membrane oxygenation, 8 with high risk of malignancy) were treated, without induction therapy. Prophylactic ECP for 6 months (24 procedures) was initiated immediately postoperatively. Immunosuppression consisted of low-dose tacrolimus (8–10 ng/ml, months 1–6; 5–8 ng/ml, >6 months) with delayed start; mycophenolate mofetil (MMF); and low maintenance steroid with delayed start (POD 7) and tapering in the first year. One-year survival was 88.5%. Three patients died from infection (POD 12, 51, 351), and one from recurrence of cancer (POD 400). Incidence of severe infection was 17.9% (n = 5, respiratory tract). Within the first year, antibody-mediated rejection was detected in one patient (3.6%) and acute cellular rejection in four (14.3%). ECP with reduced-intensity immunosuppression is safe and effective in avoiding allograft rejection in HTX recipients with risk of severe infection or cancer recurrence.

Antithymocyte globulin induction therapy and myocardial complement deposition in pediatric heart transplantation

BACKGROUND

Antithymocyte globulin (ATG) consists of polyclonal antibodies directed primarily against human T lymphocytes but may contain antibodies with affinity for other tissues in the transplanted organ, resulting in complement (C4d) deposition. This phenomenon has been demonstrated in endomyocardial biopsies (EMBs) of adult cardiac transplants. We examined the relationship of induction immunosuppression with ATG and C4d deposition in EMB of pediatric cardiac transplants.

METHODS

Results of C4d immunohistochemistry were available from all EMB of patients transplanted at our center between June 2012 and April 2018 (n = 48) who received induction immunosuppression with either ATG (n = 20) or basiliximab (n = 28) as the standard of care.

RESULTS

C4d deposition in the first year post-heart transplant was more commonly seen among patients who received ATG induction (20% of EMBs in ATG group vs 1% of EMBs in basiliximab group; p < .0001). C4d deposition related to ATG was observed early post-transplant (50% ATG vs 0% basiliximab on first EMB; p < .0001 and 35% ATG vs 0% basiliximab on the second EMB; p = .0012). While this difference waned by the third EMB (5% ATG vs 0% basiliximab; p = .41), positive C4d staining persisted to the sixth EMB in the ATG group only (6%).

CONCLUSION

C4d deposition is common on EMB up to 1 year post-pediatric cardiac transplant following ATG induction. This high rate of positive C4d staining in the absence of histologic AMR after ATG induction therapy must be accounted for in making clinical decisions regarding cardiac allograft rejection diagnosis and treatment.

Use of induction therapy in pediatric heart transplant recipients in Switzerland - Analysis of the Swiss national database

BACKGROUND

Data on individualized immunosuppressive protocols for the pediatric heart recipients are missing in Europe. To contribute to this very small but specialized field, we describe the use of induction therapy (IT) in pediatric heart transplant patients in Switzerland and the retrospective outcomes.

METHOD

This is a retrospective national database analysis of children <19 years of age at time of heart transplantation (HT) from 05/2008-01/2018. Use of IT or no IT, use of steroids, calculated panel reactive antibodies (cPRA) and outcomes (Mortality, post-transplant lymphoproliferative disease (PTLD), rejection rates) were studied within a mean follow-up period of 2.9 years (0.2-8.1 years).

RESULTS

All 32 patients (12♂, 20♀), median age at HT of 6.4 years (24 days - 18 years) received IT using either polyclonal antibodies (ATG; 72%) or interleukin-2 receptor antagonist (anti-IL-2R mAb; 28%). Length of treatment was median of 4 (1-63) days. At time of HT all patients received steroids, while at discharge 32% and one year after HT 19%. Kaplan-Meier analysis of survival revealed a one-year survival of 86%. Three out of 7 patients with elevated cPRA (43%) died. Median time to first treated rejection was 19.4 months (±60.5 SD) without significant difference if treated with anti-IL-2R mAb or ATG (p:0.5). No development of PTLD, chronic renal failure needing ongoing renal replacement therapy or diabetes mellitus were recorded.

DISCUSSION

This is the first report of the national practice use of IT within Switzerland. It reveals a high use of IT, no development of PTLD and a low use of steroids at one-year post HT.

Considerations and controversies of pharmacologic management of the pediatric kidney transplant recipient

Pediatric kidney transplantation has experienced considerable growth and improvement in patient and allograft outcomes over the past 20 years, in part due to advancements in immunosuppressive regimens and management. Despite this progress, care for this unique population can be challenging due to limited pediatric transplant data and trials, intricacies related to differences in children and adolescents compared with their adult counterparts, and limitations to long-term survival facing all solid organ transplant populations. Immunosuppression and infection prevention practices vary from one pediatric transplant center to another and clinical controversies exist surrounding treatment and dosing. This review aims to summarize key aspects of pharmacologic management in this population and present pertinent data that describe the influence of practice to serve as a resource for practitioners caring for this unique specialty patient population. Additionally, this review highlights select controversies that exist within pediatric kidney transplantation.

Immunosuppression trends in solid organ transplantation: The future of individualization, monitoring, and management

Immunosuppression regimens used in solid organ transplant have evolved significantly over the past 70 years in the United States. Early immunosuppression and targets for allograft success were measured by incidence and severity of allograft rejection and 1-year patient survival. The limited number of agents, infancy of human leukocyte antigen (HLA) matching techniques and lack of understanding of immunoreactivity limited the early development of effective regimens. The 1980s and 1990s saw incredible advancements in these areas, with acute rejection rates halving in a short span of time. However, the constant struggle to achieve the optimal balance between under- and overimmunosuppression is weaved throughout the history of transplant immunosuppression. The aim of this paper is to discuss the different eras of immunosuppression and highlight the important milestones that were achieved while also discussing this in the context of rational agent selection and regimen design. This discussion sets the stage for how we can achieve optimal long-term outcomes during the next era of immunosuppression, which will move from universal protocols to patient-specific optimization.

Induction Immunosuppression and Renal Outcomes in Adult Heart Transplantation

BACKGROUND

This study explores the use of induction therapy in orthotopic heart transplantation as it relates to preoperative renal function and evaluates the impact of its utilization on post-transplant outcomes.

METHODS

We conducted a retrospective analysis using the United Network for Organ Sharing database from 2000 to 2018 evaluating the initiation of de novo dialysis after transplantation. We examined the relationship between induction immunosuppression and pre-transplant estimated glomerular filtration rate with post-transplant outcomes, accounting for inter-center variability through a mixed-effects logistic regression model.

RESULTS

In total, 16,201 patients were included with a median age of 57 y (interquartile range 47, 63); 26% were women (n = 4222) and 28% (n = 4552) had a history of diabetes mellitus. The median estimated glomerular filtration rate (eGFR) was 67.5 mL/min (interquartile range 53.1, 86.7); 51.2% (n = 3068) of the recipients with eGFR < 60 received induction therapy compared to 42.5% (n = 4336) within the eGFR ≥ 60 group (P < 0.001). Adjusted multivariable analysis found that induction therapy was associated with de novo dialysis (odds ratio 1.25, 95% confidence interval 1.10-1.43, P < 0.001), with the most significant effect on patients with eGFR ≥ 60. Although significant, there was a weak correlation between center-level induction utilization and mean eGFR (r = -0.2, P < 0.001).

CONCLUSION

In this analysis, the use of induction immunosuppression in orthotopic heart transplantation varied widely between centers and did not correlate strongly with pre-transplant eGFR. In addition, its utilization did not mitigate the risk of renal replacement therapy after transplantation and in fact was associated with increased risk even after adjusting for confounders most notably in patients with eGFR ≥ 60.

Nationwide variability in the use of induction immunosuppression for adult heart transplantation

BACKGROUND

Institutional factors have been shown to impact outcomes following orthotopic heart transplantation (OHT). This study evaluated center variability in the utilization of induction therapy for OHT and its implications on clinical outcomes.

METHODS

Adult OHT patients between 2010 and 2018 were identified from the United Network for Organ Sharing registry. Transplant centers were stratified based on their rates of induction therapy utilization. Mixed-effects logistic regression models were created with drug-treated rejection within 1 year as primary endpoint and individual centers as a random parameter. Risk-adjusted Cox regression was used to evaluate patient-level mortality outcomes.

RESULTS

In 17,524 OHTs performed at 100 centers, induction therapy was utilized in 48.6% (n = 8411) with substantial variability between centers (interquartile range, 21.4%-79.1%). There were 36, 30, and 34 centers in the low (<29%), intermediate (29%-66%), and high (>67%) induction utilization terciles groups, respectively. Induction therapy did not account for the observed variability in the treated rejection rate at 1 year among centers after adjusting for donor and recipient factors (p = .20). No differences were observed in postoperative outcomes among induction utilization centers groups (all, p > .05). Furthermore, there was a weak correlation between the percentage of induction therapy utilization at the center-level and recipients found to have moderate (r = .03) or high (r = .04) baseline risks for acute rejection at 1 year.

CONCLUSIONS

This analysis demonstrates that there is substantial variability in the use of induction therapy among OHT centers. In addition, there was a minimal correlation with baseline recipient risk or 1-year rejection rates, suggesting a need for better-standardized practices for induction therapy use in OHT.

Impact of Induction Immunosuppression on Post-Transplant Outcomes of Patients Bridged with Contemporary Left Ventricular Assist Devices

For patients bridged to transplant (BTT) with left ventricular assist devices (LVAD), data regarding the use of induction immunosuppressive therapy remain limited. The objectives of the current study were to describe the current trends and clinical consequences of IT in patients BTT with LVAD. The United Network of Organ Sharing database was queried to identify adult, single-organ heart transplant recipients who were BTT with LVAD between 2008 and 2018. Propensity score matching was then used to balance clinical covariates between those patient who did and did not receive IT. The primary outcomes of interest were graft survival, hospitalization for rejection and infection, and freedom from transplant coronary artery disease (TCAD). In the overall cohort, 49.1% (n = 3,978) received IT, with basiliximab being the most commonly used agent followed by antithymocyte globulin. After propensity score matching, 4,388 patients (2,194 without induction and 2,194 with induction) were identified. Between those who did and did not receive IT, there was no significant difference in graft survival, freedom from hospitalization for rejection, and freedom from hospitalization for infection. Patients who received IT experienced increased freedom from TCAD (p = 0.004) with unadjusted hazard ratio of 0.81 (95% Cardiac Index: 0.70-0.93). For freedom from TCAD, antithymocyte globulin was associated with better outcomes than basiliximab (80.2% vs. 73.1% at 5 years, log rank p value = 0.004). In a sensitivity analysis, there was no significant increase in hospitalization for infection in those patients with an infected LVAD before transplant. Use of induction therapy in patients BTT with LVAD appears to be safe and feasible, without a significant increase in the risk of infection or rejection, even in those patients with pretransplant device-related infections. IT, particularly antithymocyte globulin, was associated with increased time to development of TCAD. Routine use of IT in patients BTT with LVAD may be considered, and further randomized control trials are warranted to further support these data.

Outcomes of patients with infection related to a ventricular assist device after heart transplantation

BACKGROUND

Despite significant advances in durable mechanical support survival, infectious complications remain the most common adverse event after ventricular assist device (VAD) implantation and the leading cause of early death after transplantation. In this study, we aim to describe our local infectious epidemiology and review short-term survival and infectious incidence rates in the post-transplantation period and assess risk factors for infectious episodes after transplantation.

METHODS

Retrospective single-center study of all consecutive adult heart transplant patients from 2008 to 2017. Survival data were estimated and summarized using the Kaplan-Meier method. We quantified and evaluated the difference in the incidence rate between patients with and without infection using a Fine-Gray model. The outcome of interest is the time to first infection diagnosis with post-transplant death as the competing event.

RESULTS

Among 278 heart transplant patients, 74 (26.5%) underwent LVAD implantation. Twenty-one patients (28.3%) developed an infection while supported by an LVAD. When compared to patients supported by an LVAD without a preceding infection, BMI was significantly greater (31.2 vs 27.8 kg/m² , P = .03). Median follow-up post-transplantation was 3.01 years. Significant risk factors for the competing risk regression for infection after heart transplantation include LVAD infection (HR 1.94, [95% CI] 1.11-3.39, P = .020) and recipient COPD (HR 2.14, [95% CI] 1.39-3.32, P = .001) when adjusted for recipient age, gender, hypertension, diabetes mellitus, and body mass index.

CONCLUSIONS

Patients with LVAD-related infection had a significantly increased risk of infectious complications after heart transplantation. Further research on the avoidance of induction agents and reduced maintenance immunosuppression in this patient population is warranted.

Impact of induction immunosuppression on patient survival in heart transplant recipients treated with tacrolimus and mycophenolic acid in the current allocation era

BACKGROUND

The practice of induction therapy with either rabbit anti-thymocyte globulin (r-ATG) or interleukin-2 receptor antagonists (IL-2RA) is common among heart transplant recipients. However, its benefits in the setting of contemporary maintenance immunosuppression with tacrolimus/mycophenolic acid (TAC/MPA) are unknown.

METHODS

We compared post-transplant mortality among three induction therapy strategies (r-ATG vs IL2-RA vs no induction) in a retrospective cohort analysis of heart transplant recipients maintained on TAC/MPA in the Organ Procurement Transplant Network (OPTN) database between the years 2006 and 2015. We used a multivariable model adjusting for clinically important co-morbidities, and a propensity score analysis using the inverse probability weighted (IPW) method in the final analysis.

RESULTS

In multivariable IPW analysis, r-ATG (HR = 1.23; 95% CI = 1.05-1.46, P = 0.01) remained significantly associated with a higher mortality. There was a trend toward having a higher mortality in the IL2-RA (HR = 1.11; 95% CI = 1.00-1.24, P = 0.06) group. Subgroup analyses failed to show a patient survival benefit in using either r-ATG or IL2-RA among any of the subgroups analyzed.

CONCLUSION

In this contemporary cohort of heart transplant recipients receiving TAC/MPA, neither r-ATG nor IL2-RA were associated with a survival benefit. On the contrary, adjusted analyses showed a significantly higher mortality in the r-ATG group and a trend toward higher mortality in the IL2-RA group. While caution is needed in interpreting treatment effects in an observational cohort, these data call into question the benefit of induction therapy as a common practice and highlight the need for more studies.

The change of immunosuppressive regimen from calcineurin inhibitors to mammalian target of rapamycin (mTOR) inhibitors and its effect on malignancy following heart transplantation

Malignancy is a significant cause of mortality after organ transplantation. There is an increased rate of malignancy following heart transplantation (HTx) compared to the general population and other organ transplant recipients. Post-HTx patients with a history of malignancy are also at a higher risk of developing new malignancies or exacerbation of their existing malignancies. Mammalian target of Rapamycin inhibitors (mTORIs) are newly introduced immunosuppressive drugs with a unique mechanism of action. By changing the immunosuppressive regimen from classic drugs, especially calcineurin inhibitors (CNIs) to mTORIs, the rate of developing de novo malignancies and the relapse of former malignancies is significantly reduced. However, issues like allograft function, total surveillance of patients, and post-transplantation complications should be considered during the conversion of drug regimens utilizing CNIs to drug regimens employing mTORIs. We reviewed different post-heart transplant maintenance immunosuppressive regimens and their effect on post-HTx malignancies with a focus on mTORIs, compared safety against effectiveness, and gathered conclusions based on our review of the literature, which may lead clinicians to make a better evidence-based decision regarding post-HTx maintenance immunosuppressive drug regimens. Overall, CNI to mTORI conversion in post-HTx maintenance immunosuppressive drug regimens was associated with a reduced rate of developing malignancy in post-HTx patients. Furthermore, nephrotoxicity decreased significantly while using mTORIs in combination with lower doses of CNIs and the rejection rate was equivalent to CNI-only regimens. In conclusion, mTORI-based maintenance immunosuppressive drug regimens seem to be safe and beneficial when considering efficacy vs. adverse effects, and all-cause mortality rates are significantly lower in patients switched to mTORIs when compared to CNI recipients.

Clinical phenomapping and outcomes after heart transplantation

BACKGROUND

Survival after heart transplantation (HTx) is limited by complications related to alloreactivity, immune suppression, and adverse effects of pharmacologic therapies. We hypothesize that time-dependent phenomapping of clinical and molecular data sets is a valuable approach to clinical assessments and guiding medical management to improve outcomes.

METHODS

We analyzed clinical, therapeutic, biomarker, and outcome data from 94 adult HTx patients and 1,557 clinical encounters performed between January 2010 and April 2013. Multivariate analyses were used to evaluate the association between immunosuppression therapy, biomarkers, and the combined clinical end point of death, allograft loss, retransplantation, and rejection. Data were analyzed by K-means clustering (K = 2) to identify patterns of similar combined immunosuppression management, and percentile slopes were computed to examine the changes in dosages over time. Findings were correlated with clinical parameters, human leucocyte antigen antibody titers, and peripheral blood mononuclear cell gene expression of the AlloMap (CareDx, Inc., Brisbane, CA) test genes. An intragraft, heart tissue gene coexpression network analysis was performed.

RESULTS

Unsupervised cluster analysis of immunosuppressive therapies identified 2 groups, 1 characterized by a steeper immunosuppression minimization, associated with a higher likelihood for the combined end point, and the other by a less pronounced change. A time-dependent phenomap suggested that patients in the group with higher event rates had increased human leukocyte antigen class I and II antibody titers, higher expression of the FLT3 AlloMap gene, and lower expression of the MARCH8 and WDR40A AlloMap genes. Intramyocardial biomarker-related coexpression network analysis of the FLT3 gene showed an immune system-related network underlying this biomarker.

CONCLUSIONS

Time-dependent precision phenotyping is a mechanistically insightful, data-driven approach to characterize patterns of clinical care and identify ways to improve clinical management and outcomes.

Outcomes of Induction Therapy with Rabbit Anti-Thymocyte Globulin in Heart Transplant Recipients: A Single Center Retrospective Cohort Study

Background

Induction immunosuppression is used in transplantation to prevent early acute rejection. The survival benefit of rabbit anti-thymocyte globulin (rATG) induction has not been established yet. We sought to determine the role of rATG in preventing rejection and improving overall survival.

Material/Methods

A retrospective cohort study was conducted from 2005 to 2009 and data of consecutive 268 heart transplant recipients were reviewed.

Results

The data of 144 patients who received induction with rATG were compared to 124 patients who did not. Although overall survival was not different between the 2 groups (P=0.12), there was a significant difference in restricted mean survival time (RMST) at 5 years (RMST=4.8 months; 95% CI: 1.0–8.6, P=0.01) and 10 years (RMST=10.4 months; 95% CI: 1.6–19.3, P=0.02) in favor of the non-induced patients. No difference was observed between induced and non-induced patients who developed de novo donor specific antibodies. There was a significant difference in median days to first rejection in favor of the induced group (P<0.001).

Conclusions

Induction with rATG adds no survival benefit in heart transplant recipients. Patients who did not receive induction therapy had higher life expectancy at 5 years and 10 years. Although there was significant delay in the first rejection episode in favor of the rATG induced group, no difference was observed in donor specific antibodies. This study indicates a need for separate analysis of peri-transplantation co-morbidities and mainly the incidence of acute kidney injury, which could affect long-term survival.

Comparison of basiliximab vs antithymocyte globulin for induction in pediatric heart transplant recipients: An analysis of the International Society for Heart and Lung Transplantation database

This study aims to compare 2 common induction strategies, basiliximab and ATG. Analysis of the ISHLT transplant registry was performed. The database was queried for pediatric heart transplants from January 1, 2000, to June 30, 2015, who had received induction with basiliximab or ATG. Primary end-point was graft survival. Secondary end-points included 1-year survival and 1-year conditional survival. There were 3158 heart transplants who received induction with basiliximab or ATG. The ATG cohort was younger, more likely to have congenital heart disease or be a retransplant, have a higher PRA, longer ischemic time, and been transplanted earlier in the study period (all P<.01). There was no difference in graft loss in the basiliximab cohort compared to the ATG cohort (HR 1.18 P=.06). On conditional 1-year survival analysis, basiliximab induction was associated with graft loss (HR=1.35 95% CI 1.1-1.7, P<.01), and in the propensity-matched cohort, the basiliximab cohort was more likely to experience rejection prior to discharge (P=.04). Infection prior to discharge was more common in the antithymocyte cohort. Induction with ATG is associated with improved late graft survival compared to basiliximab.

A Review of Induction with Rabbit Antithymocyte Globulin in Pediatric Heart Transplant Recipients

Pediatric heart transplantation (pHTx) represents only a small proportion of cardiac transplants. Due to these low numbers, clinical data relating to induction therapy in this special population are far less extensive than for adults. Induction is used more widely in pHTx than in adults, mainly because of early steroid withdrawal or complete steroid avoidance. Antithymocyte globulin (ATG) is the most frequent choice for induction in pHTx, and rabbit antithymocyte globulin (rATG, Thymoglobulin^®) (Sanofi Genzyme) is the most widely-used ATG preparation. In the absence of large, prospective, blinded trials, we aimed to review the current literature and databases for evidence regarding the use, complications, and dosages of rATG. Analyses from registry databases suggest that, overall, ATG preparations are associated with improved graft survival compared to interleukin-2 receptor antagonists. Advantages for the use of rATG have been shown in low-risk patients given tacrolimus and mycophenolate mofetil in a steroid-free regimen, in sensitized patients with pre-formed alloantibodies and/or a positive donor-specific crossmatch, and in ABO-incompatible pHTx. Registry and clinical data have indicated no increased risk of infection or post-transplant lymphoproliferative disorder in children given rATG after pHTx. A total rATG dose in the range 3.5–7.5 mg/kg is advisable.

Induction regimen and survival in simultaneous heart-kidney transplant recipients

BACKGROUND

Induction therapy in simultaneous heart-kidney transplantation (SHKT) is not well studied in the setting of contemporary maintenance immunosuppression consisting of tacrolimus (TAC), mycophenolic acid (MPA), and prednisone (PRED).

METHODS

We analyzed the Organ Procurement and Transplant Network registry from January 1, 2000, to March 3, 2015, for recipients of SHKT (N = 623) maintained on TAC/MPA/PRED at hospital discharge. The study cohort was further stratified into 3 groups by induction choice: induction (n = 232), rabbit anti-thymoglobulin (r-ATG; n = 204), and interleukin-2 receptor-α (n = 187) antagonists. Survival rates were estimated using the Kaplan-Meier estimator. Multivariable inverse probability weighted Cox proportional hazard regression models were used to assess hazard ratios associated with post-transplant mortality as the primary outcome. The study cohort was censored on March 4, 2016, to allow at least 1-year of follow-up.

RESULTS

During the study period, the number of SHKTs increased nearly 5-fold. The Kaplan-Meier survival curve showed superior outcomes with r-ATG compared with no induction or interleukin-2 receptor-α induction. Compared with the no-induction group, an inverse probability weighted Cox proportional hazard model showed no independent association of induction therapy with the primary outcome. In sub-group analysis, r-ATG appeared to lower mortality in sensitized patients with panel reactive antibody of 10% or higher (hazard ratio, 0.19; 95% confidence interval, 0.05-0.71).

CONCLUSION

r-ATG may provide a survival benefit in SHKT, especially in sensitized patients maintained on TAC/MPA/PRED at hospital discharge.

Impact of Rabbit Antithymocyte Globulin Dose on Long-term Outcomes in Heart Transplant Patients

BACKGROUND

Optimal dosing strategies have not been established for rabbit antithymocyte globulin (rATG) after heart transplantation, and there is currently wide variability in rATG regimens with respect to both dose and duration.

METHODS

In a retrospective, single-center analysis, 523 patients undergoing heart transplantation during 1996 to 2009 were stratified by cumulative rATG dose: less than 4.5 mg/kg (group A), 4.5 to 7.5 mg/kg (group B) or greater than 7.5 mg/kg (group C).

RESULTS

Survival at 1 year after transplantation was 80% in group A, 90% in group B, and 88% in group C (P = 0.062). Incidence of acute rejection per 1000 patient-years was significantly higher in group A (hazards ratio [HR], 54.8; 95% confidence interval [95% CI], 33.9-83.8) compared to groups B (19.6; 95% CI, 11.4-31.4) and C (23.6; 95% CI, 17.5-31.3). Incidence of severe infection 10 years after transplantation was higher in group C (45%) than groups A (37%) or B (23%) (P < 0.001); cytomegalovirus infection rates were 35%, 20% and 23%, respectively (P = 0.009). Multivariable Cox regression showed an HR of 0.51 (95% CI, 0.25-1.02) for acute rejection with group B versus group A, and 0.54 (95% CI, 0.33-0.88; P = 0.013) for severe infection. The rate of malignancy per 1000 patient-years was higher in groups B (13.85) and C (14.95) than group A (7.83).

CONCLUSIONS

These retrospective data suggest that a cumulative rATG dose of 4.5 to 7.5 mg/kg may offer a better risk-benefit ratio than lower or higher doses, with acceptable rates of infection and posttransplant malignancy. Prospective trials are needed.

A Proposal for Early Dosing Regimens in Heart Transplant Patients Receiving Thymoglobulin and Calcineurin Inhibition

There is currently no consensus regarding the dose or duration of rabbit antithymocyte globulin (rATG) induction in different types of heart transplant patients, or the timing and intensity of initial calcineurin inhibitor (CNI) therapy in rATG-treated individuals. Based on limited data and personal experience, the authors propose an approach to rATG dosing and initial CNI administration. Usually rATG is initiated immediately after exclusion of primary graft failure, although intraoperative initiation may be appropriate in specific cases. A total rATG dose of 4.5 to 7.5 mg/kg is advisable, tailored within that range according to immunologic risk and adjusted according to immune monitoring. Lower doses (eg, 3.0 mg/kg) of rATG can be used in patients at low immunological risk, or 1.5 to 2.5 mg/kg for patients with infection on mechanical circulatory support. The timing of CNI introduction is dictated by renal recovery, varying between day 3 and day 0 after heart transplantation, and the initial target exposure is influenced by immunological risk and presence of infection. Rabbit antithymocyte globulin and CNI dosing should not overlap except in high-risk cases. There is a clear need for more studies to define the optimal dosing regimens for rATG and early CNI exposure according to risk profile in heart transplantation.

Desensitization Strategies Pre- and Post-Cardiac Transplantation

OPINION STATEMENT

Panel reactive antibody (PRA) testing has become standard in the evaluation of patients prior to cardiac transplant. Sensitizing events such as blood transfusions, which result in the accumulation of pre-transplant antibodies, should be avoided as clinically feasible. Desensitization therapy might be considered in sensitized patients with cPRA > 50 % although distinct cutoff PRA values for initiating therapy pre-transplant are patient and transplant program dependent. Post-cardiac transplant, quantitative antibodies should also be periodically analyzed, at intervals individualized to the patient. Donor-specific antibodies (DSA) after cardiac transplantation have been shown to be associated with worsened survival. It appears that complement fixing DSA confer the greatest risk for antibody-mediated rejection post-transplant. Desensitization strategies aim to reduce the number of clinically important antibodies prior to and after transplant, both by removal of antibodies and cessation of further production. Current desensitization regimens include pharmacologic, procedural, and surgical modalities, and must be individualized to the patient. Currently, most cardiac transplant programs tailor the post-transplant immunosuppressive regimen based on clinical factors and immunologic assays and may include the use of cytolytic induction and/or intravenous immune gammaglobulin in higher risk patients.

Rabbit antithymocyte globulin induction and risk of post-transplant lymphoproliferative disease in adult and pediatric solid organ transplantation: An update

The most modifiable risk factor for post-transplant lymphoproliferative disease (PTLD) is the type and dose of induction and maintenance immunosuppressive therapy. It is challenging to identify the contribution of a single agent such as rabbit antithymocyte globulin (rATG) in the setting of multidrug therapy. Registry analyses can be helpful but are limited by methodological restrictions and inclusion of historical patient cohorts. These are typically from eras when rATG dosing was markedly higher than current dosing (e.g. total dose 14 mg/kg versus 6 mg/kg now), accompanied by higher exposure to maintenance therapies, and often an absence of antiviral prophylaxis. The largest registry analysis to assess rATG specifically found no risk of PTLD after kidney transplantation, but conflicting results have been reported, highlighting the difficulty of interpreting this type of analysis. The relative rarity of PTLD means that individually controlled trials are underpowered to assess its occurrence, but the available data do not suggest an effect of rATG. A pooled analysis of data from studies of rATG induction in kidney and heart transplantation found the incidence of PTLD to be comparable to published reports in the overall transplant population. Data on the effect of rATG dose are inconclusive, but in patients receiving antiviral prophylaxis it does not appear to be influential. Nevertheless, it would seem reasonable to employ the lowest dose of rATG compatible with effective induction, particularly in EBV-seronegative recipients and other high-risk groups such as heart-lung transplant recipients. Overall, the risk of PTLD following rATG induction therapy with modern dosing regimens and under current management conditions appears unlikely to make an important contribution to the risk:benefit balance.