Cohort study: "Outcomes of kidney transplantation in patients with prosthetic heart valves"

The number of kidney transplant candidates with prosthetic heart valves (PHVs) is increasing. Yet, outcomes of kidney transplantation in these patients are still unclear. This is the first report of post-transplant outcomes in patients with PHVs at time of kidney transplantation. We conducted a matched cohort study among recipients from the multicentric and prospective DIVAT cohort to compare the outcomes in patients with left-sided PHVs at time of transplantation and a group of recipients without PHV matched according to age, dialysis time, initial disease, pretransplant DSA, diabetes, and cardiovascular events. Of 23 018 patients, 92 patients with PHVs were included and compared to 276 patients without PHV. Delayed graft function and postoperative bleeding occurred more frequently in patients with PHVs. Kidney graft survival was similar between groups. 5-year overall survival was 68.5% in patients with PHV vs. 87.9% in patients without PHV [HR, 2.72 (1.57-4.70), P = 0.0004]. Deaths from infection, endocarditis, and bleeding were more frequent in patients with PHV. Mechanical valves, but not bioprosthetic valves, were independent risk factors for mortality [HR, 2.89 (1.68-4.97), P = 0.0001]. Patients with PHV have high mortality rates after kidney transplantation. These data suggest that mechanical valves, but not biological valves, increase risks of post-transplant mortality.

Complement inhibition for prevention of antibody-mediated rejection in immunologically high-risk heart allograft recipients

Allosensitization represents a major barrier to heart transplantation (HTx). We assessed the efficacy and safety of complement inhibition at transplant in highly sensitized heart transplant recipients. We performed a single-center, single-arm, open-label trial (NCT02013037). Patients with panel reactive antibodies (PRA) ≥70% and pre-formed donor-specific antibodies (DSA) were eligible. In addition to standard of care, patients received nine infusions of eculizumab during the first 2 months posttransplant. The primary composite endpoint was antibody-mediated rejection (AMR) ≥pAMR2 and/or left ventricular dysfunction during the first year. Secondary endpoints included hemodynamic compromise, allograft rejection, and patient survival. Twenty patients were included. Median cPRA and mean fluorescence intensity of immunodominant DSA were 95% (90%-97%) and 6250 (5000-10 000), respectively. Retrospective B cell and T cell flow crossmatches were positive in 14 and 11 patients, respectively. The primary endpoint occurred in four patients (20%). Survival at 1 year was 90% with no deaths resulting from AMR. In a prespecified analysis comparing treated patients to matched control patients, we observed a dramatic reduction in the risk of biopsy-proven AMR in patients treated with eculizumab (HR = 0.36, 95% CI = 0.14-0.95, p = .032). Our findings support the prophylactic use of complement inhibition for heart transplantation at high immunological risk. ClinincalTrials.gov, NCT02013037.

The emerging field of non-human leukocyte antigen antibodies in transplant medicine and beyond

The major medical advances in our knowledge of the human leukocyte antigen (HLA) system have allowed us to uncover several gaps in our understanding of alloimmunity. Although the non-HLA system has long sparked the interest of the transplant community, recognition of the role of immunity to non-HLA antigenic targets has only emerged recently. In this review, we will provide a comprehensive summary of the paradigm-changing concept of immunity to the non-HLA angiotensin II type 1 receptor (AT1R), discovered by Duška Dragun et al., that began from careful bedside clinical observations, to validated detection of anti-AT1R antibodies and lead to clinical intervention. This scientific approach has also allowed the recognition of broader pathogenicity of anti-AT1R antibodies across multiple organ transplants and in other human diseases, the integration of both non-HLA and HLA systems to understand their immunologic effects on organ allografts, and the identification of future directions for therapeutic intervention to modulate immunity to AT1R. Rationally designed successful interventions to target AT1R system provide an exemplar for other non-HLA antibodies to cross borders between medical specialties, will generate new avenues in translational research beyond transplantation, and will foster the development of new and reliable tools to improve our understanding of non-HLA immunity and ultimately allow us to improve patient care.

Data-driven Derivation and Validation of Novel Phenotypes for Acute Kidney Transplant Rejection using Semi-supervised Clustering

BACKGROUND

Over the past decades, an international group of experts iteratively developed a consensus classification of kidney transplant rejection phenotypes, known as the Banff classification. Data-driven clustering of kidney transplant histologic data could simplify the complex and discretionary rules of the Banff classification, while improving the association with graft failure.

METHODS

The data consisted of a training set of 3510 kidney-transplant biopsies from an observational cohort of 936 recipients. Independent validation of the results was performed on an external set of 3835 biopsies from 1989 patients. On the basis of acute histologic lesion scores and the presence of donor-specific HLA antibodies, stable clustering was achieved on the basis of a consensus of 400 different clustering partitions. Additional information on kidney-transplant failure was introduced with a weighted Euclidean distance.

RESULTS

Based on the proportion of ambiguous clustering, six clinically meaningful cluster phenotypes were identified. There was significant overlap with the existing Banff classification (adjusted rand index, 0.48). However, the data-driven approach eliminated intermediate and mixed phenotypes and created acute rejection clusters that are each significantly associated with graft failure. Finally, a novel visualization tool presents disease phenotypes and severity in a continuous manner, as a complement to the discrete clusters.

CONCLUSIONS

A semisupervised clustering approach for the identification of clinically meaningful novel phenotypes of kidney transplant rejection has been developed and validated. The approach has the potential to offer a more quantitative evaluation of rejection subtypes and severity, especially in situations in which the current histologic categorization is ambiguous.

Statistical performance of 16 posttransplant risk scores in a contemporary cohort of heart transplant recipients

Accurate risk stratification of early heart transplant failure is required to avoid futile transplants and rationalize donor selection. We aimed to evaluate the statistical performance of existing risk scores on a contemporary cohort of heart transplant recipients. After an exhaustive search, we identified 16 relevant risk scores. From the UNOS database, we selected all first noncombined adult heart transplants performed between 2014 and 2017 for validation. The primary endpoint was death or retransplant during the first year posttransplant. For all scores, we analyzed their association with outcomes, sensitivity, specificity, likelihood ratios, and discrimination (concordance index and overlap of individual scores). The cohort included 9396 patients. All scores were significantly associated with the primary outcome (P < .001 for all scores). Their likelihood ratios, both negative and positive, were poor. The discriminative performance of all scores was limited, with concordance index ranging from 0.544 to 0.646 (median 0.594) and an important overlap of individual scores between patients with or without the primary endpoint. Subgroup analyses revealed important variation in discrimination according to donor age, recipient age, and the type of assist device used at transplant. Our findings raise concerns about the use of currently available scores in the clinical field.

Assessment of the Utility of Kidney Histology as a Basis for Discarding Organs in the United States: A Comparison of International Transplant Practices and Outcomes

BACKGROUND

Many kidneys donated for transplant in the United States are discarded because of abnormal histology. Whether histology adds incremental value beyond usual donor attributes in assessing allograft quality is unknown.

METHODS

This population-based study included patients who received a deceased donor kidney that had been biopsied before implantation according to a prespecified protocol in France and Belgium, where preimplantation biopsy findings are generally not used for decision making in the allocation process. We also studied kidneys that had been acquired from deceased United States donors for transplantation that were biopsied during allocation and discarded because of low organ quality. Using donor and recipient characteristics, we fit multivariable Cox models for death-censored graft failure and examined whether predictive accuracy (C index) improved after adding donor histology. We matched the discarded United States kidneys to similar kidneys transplanted in Europe and calculated predicted allograft survival.

RESULTS

In the development cohort of 1629 kidney recipients at two French centers, adding donor histology to the model did not significantly improve prediction of long-term allograft failure. Analyses using an external validation cohort from two Belgian centers confirmed the lack of improved accuracy from adding histology. About 45% of 1103 United States kidneys discarded because of histologic findings could be accurately matched to very similar kidneys that had been transplanted in France; these discarded kidneys would be expected to have allograft survival of 93.1% at 1 year, 80.7% at 5 years, and 68.9% at 10 years.

CONCLUSIONS

In this multicenter study, donor kidney histology assessment during allocation did not provide substantial incremental value in ascertaining organ quality. Many kidneys discarded on the basis of biopsy findings would likely benefit United States patients who are wait listed.

An International survey on living kidney donation and transplant practices during the COVID-19 pandemic

The scope of the impact of the Coronavirus disease 19 (COVID‐19) pandemic on living donor kidney transplantation (LDKT) practices across the world is not well‐defined. We received survey responses from 204 transplant centers internationally from May to June 2020 regarding the impact of the COVID‐19 pandemic on LDKT practices. Respondents represented 16 countries on five continents. Overall, 75% of responding centers reported that LDKT surgery was on hold (from 67% of North American centers to 91% of European centers). The majority (59%) of centers reported that new donor evaluations were stopped (from 46% of North American centers to 86% of European centers), with additional 23% of centers reporting important decrease in evaluations. Only 10% of centers reported slight variations on their evaluations. For the centers that continued donor evaluations, 40% performed in‐person visits, 68% by video, and 42% by telephone. Center concerns for donor (82%) and recipient (76%) safety were the leading barriers to LDKT during the pandemic, followed by patients concerns (48%), and government restrictions (46%). European centers reported more barriers related to staff limitations while North and Latin American centers were more concerned with testing capacity and insufficient resources including protective equipment. As LDKT resumes, 96% of the programs intend to screen donor and recipient pairs for coronavirus infection, most of them with polymerase chain reaction testing of nasopharyngeal swab samples. The COVID‐19 pandemic has had broad impact on all aspects of LDKT practice. Ongoing research and consensus‐building are needed to guide safe reopening of LDKT programs.

Intragraft gene expression in native kidney BK virus nephropathy versus T cell-mediated rejection: Prospects for molecular diagnosis and risk prediction

Novel tools are needed to improve diagnostic accuracy and risk prediction in BK virus nephropathy (BKVN). We assessed the utility of intragraft gene expression testing for these purposes. Eight hundred genes were measured in 110 archival samples, including a discovery cohort of native kidney BKVN (n = 5) vs pure T cell-mediated rejection (TCMR; n = 10). Five polyomavirus genes and seven immune-related genes (five associated with BKVN and two associated with TCMR) were significantly differentially expressed between these entities (FDR < 0.05). These three sets of genes were further evaluated in samples representing a spectrum of BK infection (n = 25), followed by a multicenter validation cohort of allograft BKVN (n = 60) vs TCMR (n = 10). Polyomavirus 5-gene set expression reliably distinguished BKVN from TCMR (validation cohort AUC = 0.992), but the immune gene sets demonstrated suboptimal diagnostic performance (AUC ≤ 0.720). Within the validation cohort, no significant differences in index biopsy gene expression were identified between BKVN patients demonstrating resolution (n = 35), persistent infection (n = 14) or de novo rejection (n = 11) 6 months following a standardized reduction in immunosuppression. These results suggest that, while intragraft polyomavirus gene expression may be useful as an ancillary diagnostic for BKVN, assessment for concurrent TCMR and prediction of clinical outcome may not be feasible with current molecular tools.

The XVth Banff Conference on Allograft Pathology the Banff Workshop Heart Report: Improving the diagnostic yield from endomyocardial biopsies and Quilty effect revisited

The XVth Banff Conference on Allograft Pathology meeting was held on September 23-27, 2019, in Pittsburgh, Pennsylvania, USA. During this meeting, two main topics in cardiac transplant pathology were addressed: (a) Improvement of endomyocardial biopsy (EMB) accuracy for the diagnosis of rejection and other significant injury patterns, and (b) the orphaned lesion known as Quilty effect or nodular endocardial infiltrates. Molecular technologies have evolved in recent years, deciphering pathophysiology of cardiac rejection. Diagnostically, it is time to integrate the histopathology of EMBs and molecular data. The goal is to incorporate molecular pathology, performed on the same paraffin block as a companion test for histopathology, to yield more accurate and objective EMB interpretation. Application of digital image analysis from hematoxylin and eosin (H&E) stain to multiplex labeling is another means of extracting additional information from EMBs. New concepts have emerged exploring the multifaceted significance of myocardial injury, minimal rejection patterns supported by molecular profiles, and lesions of arteriolitis/vasculitis in the setting of T cell-mediated rejection (TCMR) and antibody-mediated rejection (AMR). The orphaned lesion known as Quilty effect or nodular endocardial infiltrates. A state-of-the-art session with historical aspects and current dilemmas was reviewed, and possible pathogenesis proposed, based on advances in immunology to explain conflicting data. The Quilty effect will be the subject of a multicenter project to explore whether it functions as a tertiary lymphoid organ.

Identification of trajectories of cardiac allograft vasculopathy after heart transplantation: a nationwide comparison

Background

Cardiac allograft vasculopathy (CAV) is a major contributor of heart transplant recipient's mortality. However, little is known about CAV trajectories at a population level.

Purpose

We aimed to identify the different profiles of CAV trajectories.

Methods

Heart transplant recipients receiving care at 4 academic centers (2004 to 2016) were included. Patients underwent prospective, protocol-based monitoring consisting of repeated coronary angiographies together with systematic assessment of clinical, functional, histological and immunological parameters. The mainoutcome was the CAV trajectories, identified with unsupervised latent class mixed models.

Results

Overall, 1,301 patients were included (609 in France, 206 in Belgium and 486 in the US). The median follow-up post-transplant was 6.6 years (IQR=4.7) with 4,710 coronary angiographies analyzed (3.6±1.6 CAV assessments per patient). In the French development cohort, we identified 4 distinct profiles of CAV trajectories over 10 years that were characterized by i) Patients without CAV at baseline and non-progression (n=317, 52.1%), ii) patients without CAV at baseline and late onset CAV progression (n=52, 8.5%), iii) patients with mild baseline CAV and mild progression (n=151, 24.8%), iv) patients with mild baseline CAV and accelerated CAV progression (n=89, 14.6%, discrimination 0.92). The 4 CAV trajectories were independently validated in the external validation cohorts from Belgium (discrimination=0.92) and the US (discrimination=0.97).

Conclusion

In a large multicentric and highly phenotyped prospective cohort of heart transplant recipients, we identified and validated 4 distinct CAV trajectories corresponding to specific initial CAV grades and subsequent evolutions. Our results provide the basis for a trajectory-based assessment for risk stratification at early-stage post heart transplantation.

Figure 1. Cardiac allograft vasculopathy trajectories in France (n=609), in Belgium (n=206), in USA (n=486). Thick lines represent latent class trajectory; thin lines represent CAV individual patient trajectory.

Funding Acknowledgement

Type of funding source: None

Trajectories of Cardiac Allograft Vasculopathy After Heart Transplantation and association with mortality: a population-based study

Background

Cardiac allograft vasculopathy (CAV) is a major contributor of heart transplant recipient's mortality. However, the associations between CAV trajectories and mortality remains poorly described.

Purpose

We aimed to identify the different evolutive profiles of CAV and to determine the respective association with all-cause mortality.

Methods

Heart transplant recipients receiving care at 4 academic centers were included. Patients underwent prospective, protocol-based monitoring consisting of repeated coronary angiographies together with systematic assessment of clinical, functional, histological and immunological parameters. The mainoutcome was a prediction for CAV trajectories using unsupervised latent class mixed models. We then identified their association with all-cause mortality (NCT04117152).

Results

Overall, 1,301 patients were included (815 and 486 in the development and validation cohorts, respectively). The median follow-up post-transplant was 6.6 years (IQR=4.7) with 4,710 coronary angiographies analyzed (3.6±1.6 CAV assessments per patient). We identified 4 distinct profiles of CAV trajectories over 10 years that were characterized by i)Patients without CAV at baseline and non-progression (n=823, 63.3%), ii) patients without CAV at baseline and late onset CAV progression (n=79, 6.1%), iii) patients with mild baseline CAV and mild progression (n=261, 20.1), iv) patients with mild baseline CAV and accelerated CAV progression (n=138, 10.6%, discrimination 0.95). The 4 CAV trajectories showed gradient for all-cause mortality (p&lt;0.001). Trajectories #3 and #4 were associated with higher mortality rates (10-year patient survival of 73.43% [95% CI 65.18–80.02] and 51.89% [95% CI 38.76–63.51], respectively) as compared with trajectories #1, and #2 that were characterized by 10-year patient survival of 80.01 [95% CI 76.38–84.82] and 83.49% [95% CI 71.34–90.80], respectively (p&lt;0.001).

Conclusion

In a large multicentric and highly phenotyped prospective cohort of heart transplant recipients, we identified 4 robust CAV trajectories. These different profiles were associated with distinct prognosis. Our results provide the basis for a trajectory-based assessment of heart transplant patients for early patient risk stratification and patient monitoring.

Figure 1. Overall 10-year survival probability according to the CAV trajectory in the overall cohort (n=1,301). The left part represents the main profiles CAV grades identified with latent class mixed models. Thick lines represent latent class trajectory; thin lines represent CAV individual patient trajectory. The right part represent the Kaplan Meier curves of the different trajectories.

Funding Acknowledgement

Type of funding source: None

Determinants of trajectories of cardiac allograft vasculopathy after heart transplantation: a population based study

Background

Cardiac allograft vasculopathy (CAV) is a major contributor of heart transplant recipient's mortality. Little is known about determinants of CAV trajectories at a population level.

Purpose

We aimed to identify the respective contribution of immune and non-immune factors in the different evolutive profiles of CAV.

Methods

Heart transplant recipients receiving care at 2 academic centers (2004 to 2016) were included. Patients underwent prospective, protocol-based monitoring consisting of repeated coronary angiographies together with systematic assessment of clinical, functional, histological and immunological parameters. The outcome was CAV trajectories, identified with unsupervised latent class mixed models. The independent, predictive factors of CAV trajectories were investigated with multinomial regressions (NCT04117152).

Results

Overall, 815 patients were included. The median follow-up post-transplant was 7.7 years (IQR=5.14) with 2,742 coronary angiographies analyzed. We identified 4 distinct profiles of CAV trajectories over 10 years that were characterized by i) Patients without CAV at baseline and non-progression (n=459, 56.3%), ii) patients without CAV at baseline and late onset CAV progression (n=62, 7.6%), iii) patients with mild baseline CAV and mild progression (n=188 23.1%), iv) patients with mild baseline CAV and accelerated CAV progression (n=106, 13.0%, discrimination 0.92). Six early independent predictors of CAV trajectories were identified: donor age (p&lt;0.001), donor male gender (p&lt;0.001), donor tobacco consumption (p=0.001), recipient post-transplant dyslipidemia (p=0.009), preexisting or de novo class II anti-HLA donor-specific antibodies (p=0.004) and episode of acute cellular rejection ≥2R during the first year post transplantation (p=0.028).

Conclusion

In a large multicentric and highly phenotyped prospective cohort of heart transplant recipients, we identified 4 robust CAV trajectories and their respective immune and non-immune determinants. Our results provide the basis for a trajectory-based assessment of heart transplant patients for early patient risk stratification and patient monitoring.

Factors associated CAV trajectories in multivariate analyses in the derivation cohort. This table shows the association of clinical, immunological, functional and structural parameters associated with CAV trajectories in multivariate multinomial regression analysis. The trajectory of reference was trajectory #1, including patients with no CAV at baseline and stable CAV grade over time.

Funding Acknowledgement

Type of funding source: None

Determinants of sudden cardiac death after heart transplantation

Background

Heart transplant recipients are at high-risk of sudden cardiac death (SCD). However, risk factors of SCD in heart recipients remained poorly described.

Objective

To assess the predictors of SCD beyond the first-year post-transplant.

Methods

We enrolled consecutive patients transplanted between 2004 and 2017 in two French referral centers. We excluded patients deceased during the first year. Patients underwent an evaluation at the day of transplantation and during the first year, comprising clinical, biological, histological, immunological (circulating anti-HLA DSA) and interventional (cardiac allograft vasculopathy assessment) parameters. Echocardiographies were routinely performed in all included patients according to a prespecified protocol. According to the last consensus, SCD was defined as an unexpected out-of-hospital cardiac arrest without obvious non-cardiac cause, in the first hour after initiation of symptoms. Cox model analysis was used to determine the parameters associated with sudden death risk.

Results

A total of 913 patients were included. The median follow-up post-HT was 5.9 years (IQR=2.9–8.5). Among the 213 deaths after one year, 44 patients (21%) died from SCD. In this population, the incidence rate of SCD was 0,82 per 100 person-year (95% CI: 0,51–2,05). Among the 60 parameters tested in univariate analysis, we identified 2 independent factors of sudden death after 1 year post-HT: left ventricular ejection fraction (LVEF) ≤55% any time after transplantation ( HR 4.07, 95% CI 1.94–8.53, p&lt;0.001) and the presence of circulating anti-HLA DSA at the time of transplantation (HR 2.79, 95% CI 1.37–5.68, p=0.005). The incidence rate of SCD was 2.17 per 100 person-year (95% CI: 1.42; 4.60) and 1.21 per 100 person-year (95% CI: 0.80; 2.58) in patients with FEVG&lt;55% (n=73) and in patients with pre-formed DSA (n=260), respectively.

Conclusion

In a large multicentric and highly phenotyped cohort of heart transplant recipients, we identified two independent factors associated with SCD beyond the first year. This study provides fresh evidence of SCD assessment for improving risk stratification of HT recipients.

Funding Acknowledgement

Type of funding source: None

Incidence of sudden cardiac death after heart transplantation

Background

Sudden cardiac death (SCD) is a major contributor to the rate of mortality after heart transplantation. However, little is known about the incidence of SCD in heart recipients.

Objective

To assess the incidence of SCD after heart transplantation.

Methods

We enrolled consecutive patients transplanted between 2004 and 2017 in two French referral centers. We defined 7 main groups of causes of deaths: SCD, cardiovascular (including Cardiac allograft vasculopathy), infection, primary graft dysfunction, graft failure (including late graft dysfunction, rejection), malignancy and others. Causes of deaths were independently adjudicated by two senior cardiologists based on the analysis of death certificates and medical records. Discrepancies were resolved by discussion until a consensus was made. SCD was defined as an unexpected out-of-hospital cardiac arrest without obvious non-cardiac cause, in the first hour after initiation of symptoms.

Results

A total of 1,363 patients were included. The median follow-up post-transplant was 3.99 years (IQR=0.49–7.49). 450 patients (33%) deceased during the first year. The leading cumulative causes of death in the first year after transplantation were infection, primary graft failure, multiple organ failure during the period in intensiv car unit. Beyond the post-operativ high-risk period of the first year, the leading cumulative cause of death was SCD: among the 213 deaths that occurred beyond the first year, 44 patients (21%) died from SCD. In this period, the incidence rate of SCD reached 0,82 per 100 person-year (95% CI: 0.51–2.05).

Conclusion

In a large multicentric and highly phenotyped cohort of heart transplant recipients, the leading cumulative cause of death beyond the first-year post transplant was sudden cardiac death. Our results open discussion on management of heart recipient, such as the implementation of cardioverter-defibrillators.

Figure 1. Cumulative incidence of causes of death in heart transplant recipients beyond the first year (n=913).

Funding Acknowledgement

Type of funding source: None

The Banff 2019 Kidney Meeting Report (I): Updates on and clarification of criteria for T cell- and antibody-mediated rejection

The XV. Banff conference for allograft pathology was held in conjunction with the annual meeting of the American Society for Histocompatibility and Immunogenetics in Pittsburgh, PA (USA) and focused on refining recent updates to the classification, advances from the Banff working groups, and standardization of molecular diagnostics. This report on kidney transplant pathology details clarifications and refinements to the criteria for chronic active (CA) T cell-mediated rejection (TCMR), borderline, and antibody-mediated rejection (ABMR). The main focus of kidney sessions was on how to address biopsies meeting criteria for CA TCMR plus borderline or acute TCMR. Recent studies on the clinical impact of borderline infiltrates were also presented to clarify whether the threshold for interstitial inflammation in diagnosis of borderline should be i0 or i1. Sessions on ABMR focused on biopsies showing microvascular inflammation in the absence of C4d staining or detectable donor-specific antibodies; the potential value of molecular diagnostics in such cases and recommendations for use of the latter in the setting of solid organ transplantation are presented in the accompanying meeting report. Finally, several speakers discussed the capabilities of artificial intelligence and the potential for use of machine learning algorithms in diagnosis and personalized therapeutics in solid organ transplantation.

Banff 2019 Meeting Report: Molecular diagnostics in solid organ transplantation-Consensus for the Banff Human Organ Transplant (B-HOT) gene panel and open source multicenter validation

This meeting report from the XV Banff conference describes the creation of a multiorgan transplant gene panel by the Banff Molecular Diagnostics Working Group (MDWG). This Banff Human Organ Transplant (B-HOT) panel is the culmination of previous work by the MDWG to identify a broadly useful gene panel based on whole transcriptome technology. A data-driven process distilled a gene list from peer-reviewed comprehensive microarray studies that discovered and validated their use in kidney, liver, heart, and lung transplant biopsies. These were supplemented by genes that define relevant cellular pathways and cell types plus 12 reference genes used for normalization. The 770 gene B-HOT panel includes the most pertinent genes related to rejection, tolerance, viral infections, and innate and adaptive immune responses. This commercially available panel uses the NanoString platform, which can quantitate transcripts from formalin-fixed paraffin-embedded samples. The B-HOT panel will facilitate multicenter collaborative clinical research using archival samples and permit the development of an open source large database of standardized analyses, thereby expediting clinical validation studies. The MDWG believes that a pathogenesis and pathway based molecular approach will be valuable for investigators and promote therapeutic decision-making and clinical trials.

Use of biomarkers to improve immunosuppressive drug development and outcomes in renal organ transplantation: A meeting report

On September 27-28, 2018 the Food and Drug Administration (FDA) and the Critical Path Institute's Transplant Therapeutics Consortium convened a public workshop titled "Evidence-Based Treatment Decisions in Transplantation: The Right Dose & Regimen for the Right Patient/Individualized Treatment." The workshop facilitated cooperative engagement of transplant community stakeholders, including pharmaceutical industry, academic researchers, clinicians, patients, and regulators to discuss methods to advance the development of novel immunosuppressive drugs for use in solid organ transplantation. Day 1 focused on the utility of biomarkers in drug development_, with considerations for seeking regulatory endorsement for use in clinical trials. Biomarkers add value to drug development by improving patient selection criteria, safety monitoring, endpoint selection, and more. Regulatory endorsement through the FDA Biomarker Qualification Program encourages the use of biomarkers in drug development by instilling confidence and consistency in biomarker interpretation across trials. Public-private partnerships or consortia allow stakeholders to share expertise, resources, and data in pursuit of biomarker qualification. Biomarkers relevant to pretransplant risk assessment, early posttransplant care, and assessment of immune response, immunosuppressive drug efficacy, and graft function as discussed on day 1 of the workshop are described.