A P2X7R Single Nucleotide Mutation Promotes Chronic Allograft Vasculopathy
This trial is active, not recruiting.
|Condition||cardiac allograft vasculopathy|
|Sponsor||Children's Hospital Boston|
|Start date||January 2014|
|End date||January 2016|
|Trial size||200 participants|
|Trial identifier||NCT02082821, 14GRNT1873002, Pure-Heart-1|
Heart transplantation is a lifesaving procedure for patients with end-stage heart failure and provides a better survival and quality of life as compared to conventional medical or pharmacological treatment. Transplanted hearts are subject to the effects of the alloimmune response, which if left uncontrolled is capable of jeopardizing long-term cardiac function. Recently, advances in immunosuppression have enhanced the survival of transplanted patients. Nearly 2500 cardiac transplants per year have been performed in the US during the last 10 years and despite significant improvements, long-term cardiac allograft survival rates remain poor. More than 20% of patients do not survive beyond 3 years, and those who do survive are afflicted with the long-term complications associated with chronic immunosuppression. Life expectancy of patients who lose cardiac allografts is dramatically poor due to the absence of any therapeutic tool apart from re-transplantation, which is plagued by poor outcomes. The identification of novel therapeutic targets is thus mandatory. ATP/P2X7R signaling in T cells is highly relevant for cardiac allograft survival. ATP is a small molecule present at high concentrations inside cells and released as extracellular ATP (eATP) following cell damage or death, which is abundant at inflammation sites and acts as a danger signal constituting an "alerting system". ATP is sensed by the ionotropic purinergic P2X receptors (seven receptors named P2X1-7) expressed mainly, but not exclusively, by T lymphocytes, thereby regulating T cell activation. We have recently demonstrated that the ATP/P2X7R axis has a key role in cardiac allograft survival in humans and mice. Cardiac allograft vasculopathy (CAV) is a major limiting factor for cardiac allograft survival. One of the major limiting factors for cardiac transplantation is CAV, which develops frequently in heart transplant recipients. CAV results in allograft failure, and it occurs in 50% of cardiac transplant recipients by 5 years after transplantation, as shown by angiography or intravascular ultrasound examination. CAV is clearly of immunological origin, as syngeneic murine grafts do not develop CAV. Once CAV occurs, the most definitive treatment is re-transplantation, but survival is limited due to the fact that pharmacological management only somewhat attenuates the process. We hypothesize that a single nucleotide polymorphysm (SNP) loss-of-function P2X7R mutation (p.Glu496Ala / c.1513A>C, rs3751143) generates a compensatory upregulation of the other purinergic receptors (P2XsR), thus creating a state of hypersensitivity to eATP. This eATP hypersensitivity results in an abnormal generation of Th1/Th17 cells, that leads to CAV and early cardiac allograft loss. Our study will answer a fundamental question: What is the effect of the P2X7R loss-of-function mutation on the immune system? Our expertise in studying the ATP/P2X7R axis has been recently recognized in two publications and we are now ready to test our novel hypothesis on the P2X7R loss-of-function mutation. Our goal is to generate the first targeted-therapy for a selected group of cardiac transplant recipients.
|Observational model||case control|
Cardiac Allograft Vasculopathy
time frame: 1 year
Heart Rejection or Patient Death
time frame: 6 months; 12 months
Male or female participants from 18 years up to 65 years old.
- Male or female cardiac recipients
- 18-65 years of age
- undergoing primary heart transplantation
- the graft must be functional at the time of randomization.
- patient willing and capable of giving written informed consent for study participation and anticipated to be able to participate in the study for 12 months
- Recipient of multi-organ transplants or previously transplanted organs
- Patients with donor greater than 65 years
- Donor heart cold ischemic time > 6 hours.
- Patients who are recipients of ABO incompatible transplants
- Patients with platelet count < 50,000/mm3 at the evaluation before transplantation
- Patient who have received an unlicensed drug or therapy within one month prior to study entry or if such therapy is to be instituted post-transplantation
- Patient with a current severe systemic infection
- Patient unable to participate in the study for the full 12-month period
- Presence of severe hypercholesterolemia (≥ 350 mg/dL; ≥ 9 mmol/L) or hypertriglyceridemia (≥ 750 mg/dL; ≥ 8.5 mmol/L)
- Patients with any past (within the past 5 years) or present malignancy (other than excised basal cell carcinoma)
- Females capable of becoming pregnant must have a negative pregnancy test prior to randomization and are required to practice a medically approved method of birth control for the duration of the study and a period of 8 weeks following discontinuation of study medication, even where there has been a history of infertility.
- Patients with HIV, hepatitis B or C.
|Official title||Pure-Heart-1: A P2X7R Single Nucleotide Mutation Promotes Chronic Allograft Vasculopathy|
|Principal investigator||Paolo Fiorina, MD PhD|
|Description||Heart transplantation is a lifesaving procedure however, more then 20% of patients do not survive beyond 3 years, being the cardiac allograft afflicted by cardiac allograft vasculopathy (CAV), which results in allograft loss. The purine adenosine 5'-triphosphate (ATP), released during cell damage/inflammation, is sensed by the ionotropic purinergic P2X7 receptor (P2X7R), which is expressed primarily, though not exclusively, on lymphocytes, thus regulating T cell activation. Loss-of-function single nucleotide mutations (SNPs) have been detected for P2X7R gene; particularly the Glu496 to Ala 1513A>C (rs3751143) P2X7R loss-of-function mutation is relatively common (1-3% of individuals are mutated omozygous and 25% are heterozygous). Our central hypothesis is that a loss-of-function P2X7R mutation identifies a group of cardiac transplanted patients at high risk for CAV and cardiac allograft loss because of a compensatory overexpression of P2X1R/P2X4R, which induces a disregulation of T-bet/ROR-g, ultimately leading to the abnormal generation of Th1/Th17 cells. Our primary goal is to define the effect of the P2X7R loss-of-function mutation on clinical end points in the CTOT-05 cohort of cardiac transplant recipients (200 patients) and to explore the effects of the mutation on the immune system. Our preliminary data demonstrated that P2X7R increases during cardiac transplant rejection in vivo in mice and in humans and it is activated by ATP released by cardiac cells, thus triggering activation of Th1/Th17 cells. However, while short-term disruption of the P2X7R pathway prolongs cardiac allograft survival, the genetic deletion of P2X7R accelerates CAV and shortens cardiac allograft survival. This was evident in P2X7R KO-B6 mice and in a group of cardiac transplant recipients bearing the P2X7R loss-of-function mutation. Based on our published results and our novel observations, we have developed the following working hypothesis: P2X7R loss-of-function mutation generates a compensatory overexpression of the other ionotropic purinergic receptors (P2X1/P2X4) with chronic delivery of ATP immunity, hyperactivation T-bet/ROR-g, abnormal generation of Th1/Th17 cells and ultimately leading to accelerated CAV and to cardiac allograft loss. To test this hypothesis, we will follow two main paths: i) we will evaluate in the CTOT-05 cohort of cardiac transplant recipients the effect of the Glu496 to Ala 1513A>C (rs3751143) P2X7R loss-of-function mutation on clinical end points (development of coronary artery vasculopathy, death, re-transplantation or re-listed for transplantation, any rejection) in the first year post transplant; ii) we will explore in vivo and ex vivo in the CTOT-05 cohort of cardiac transplant recipients the effects of P2X7R loss-of-function mutation on the immune system.|
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