The Use of Extracorporeal Photopheresis as Immunomodulatory Therapy of Subclinical Antibody-mediated Rejection After Lung Transplantation: a Prospective RCT

Donor-specific antibodies (DSA) and antibody-mediated rejection have gained significant attention recently due to their serious consequences, but there are limited effective treatments for persistent DSAs in patients without graft dysfunction due to their associated severe side effects. Our center demonstrated that extracorporeal photopheresis (ECP) can potentially reduce the mean fluorescence intensity of dnDSAs in recipients with antibody-mediated rejection (AMR), suggesting it as a safe option for treating subclinical AMR with dnDSAs and inducing tolerogenic immunomodulation in this complex population.

The hypothesis underlying the proposed randomized controlled trial is that ECP might have the potential to reduce the burden of de novo donor-specific antibodies after lung transplantation, by modulating host humoral alloresponse and promoting tolerance, without provoking side effects.

Our primary objective is to evaluate the therapeutic effect of ECP in terms of reduction of dnDSAs titer in clinically stable patients with persistent (>6 months) dnDSAs (MFI>1000). As secondary objective, we intend to assess the therapeutic effect of ECP on incidence of clinical AMR, ACR, CLAD, survival and occurrence of infectious complications as well as the rate of adverse effects. Our experimental objectives are to provide an in-depth analysis of the immunological effects of ECP.

80 patients with persistent dnDSAs (> 3 months) with a MFI > 1000 will be randomized into two groups. Each group will include 40 patients. Patients will be stratified according to the presence of HLA-DQ. The control group will be observed and no active treatment will be administered. This is our standard of care in the studied clinical situation. Treatment group will receive extracorporeal photopheresis. First, a two-day treatment cycle will be performed once every second week for the first two months. Then, a two-day treatment cycle will be performed once a month for 6 months. To elucidate the specific mechanisms of ECP in modulating humoral alloresponse, a series of studies are planned: 1) flow cytometric immunophenotyping, 2) miRNA expression profiling, 3) cytokine expression, 4) gene expression signature of PBMCs, 5) proteomic characterization.

The proposed study aims to address this clinical need by investigating the effects of a safe therapeutic modality such as ECP. This study may have a dual benefit: first, it may reduce the burden of dnDSAs in lung transplant recipients, thereby reducing the incidence of antibody-mediated rejection, and second, it may promote host tolerance to the graft. In addition, we will investigate the immunomodulatory mechanisms of ECP in the context of humoral allogeneic response, which has not been previously investigated.