Extracoporeal photopheresis treatment of acute graft-versus-host disease following allogeneic haematopoietic stem cell transplantation

Second-line therapies for steroid-refractory immune-related adverse events in patients treated with immune checkpoint inhibitors

BACKGROUND

Immune checkpoint inhibitors (ICI) induce adverse events (irAEs) that do not respond to steroids, i.e. steroid-refractory (sr) irAEs, and irAEs in which steroids cannot be tapered, i.e. steroid-dependent (sd) irAEs, in about 10% of cases. An evidence-based analysis of the effectiveness of second-line immunosuppressive agents with regard to irAE and tumor control is lacking.

METHODS

The international web-based Side Effect Registry Immuno-Oncology (SERIO; http://serio-registry.org) is a collaborative initiative with the Paul-Ehrlich-Institute to document rare, severe, complex or therapy-refractory immunotherapy-induced side effects. The registry was queried on August 1, 2023 for cases of irAEs which were treated with second-line therapies.

RESULTS

From a total of 1330 cases, 217 patients (16.3%) received 249 second-line therapies. A total of 19 different second-line therapies were employed, including TNF-alpha antagonists (46.5%), intravenous immunoglobulins (IVIG; 19.1%), mycophenolate mofetil (15.9%), and methotrexate (3.6%). Therapy choices were determined by the type of irAE. The time to onset of sr-/sd-irAEs after ICI initiation did not consistently differ from steroid-responsive irAEs. While 74.3% of sr-/sd-irAEs resolved and 13.1% had improved, 4.3% persisted, 3.9% resulted in permanent sequelae, and 4.3% in death with ongoing symptoms. Infliximab exhibited potential for earlier symptom improvement compared to mycophenolate mofetil or IVIG. Tumor response in patients with second-line treated sd-/sr-irAE was similar to patients with irAEs treated with steroids only.

CONCLUSION

Several second-line therapies are effective against sr-/sd-irAEs, the second-line therapies show no clear negative impact on tumor response, and infliximab shows potential for faster improvement of symptoms. However, prospective comparative data are needed.

Thymopoiesis, Alterations in Dendritic Cells and Tregs, and Reduced T Cell Activation in Successful Extracorporeal Photopheresis Treatment of GVHD

Acute graft-versus-host disease (aGVHD) is a significant complication of allogeneic hematopoietic stem cell transplant (HSCT) and negatively affects T cell reconstitution. Extracorporeal photopheresis (ECP) reduces aGVHD, but the mechanisms remain incompletely understood. Our objective was to examine the impact of ECP on thymopoiesis in pediatric aGVHD and the mechanisms at a cellular and transcriptional level. Sixteen pediatric HSCT patients were recruited: 6 with ECP-treated aGVHD, 5 without aGVHD, and 5 with aGVHD treated with corticosteroids only. Thymopoiesis was evaluated by measuring naive T cells, TRECs, IL-7, and T cell receptor repertoire diversity. Regulatory T cell (Treg) enumeration and function and dendritic cell (DC) enumeration and phenotype were analyzed using flow cytometry. T cell transcriptome analysis was performed on ECP patients after treatment and responders pre- and post-treatment. Four ECP responders demonstrated thymic-dependent T cell recovery, and superior median naïve T cell numbers at 8 and 12 months post-HSCT compared to the aGVHD corticosteroid group. Increased Tregs and Treg suppressive function, reduced cDC/pDC and DC co-stimulatory marker expression in ECP responders suggest upregulated peripheral tolerance; these findings were not observed in partial responders. Responder post-ECP CD3+ T cell transcriptional profile demonstrated 3333 downregulated and 364 upregulated genes, with significant downregulation of ERRα and GαS pathways, and reduced expression of pro-inflammatory and adhesion proteins.

Thymic function improves with successful ECP treatment. ECP reduces T cell activation and impacts peripheral tolerance via DCs and Tregs. Differences in thymic recovery, DC, and Treg cellular patterns and the T cell transcriptome were observed between ECP responders and partial responders and require further validation and investigation in additional patients.

A standardized methodical approach to characterize the influence of key parameters on the in vitro efficacy of extracorporeal photopheresis

Extracorporeal photopheresis (ECP) is an autologous immunomodulatory cell therapy that consists of the ex vivo collection of mononuclear cells (MNCs), which are irradiated with UVA in the presence of the photosensitizing agent 8-methoxypsoralen (8-MOP) to induce cell apoptosis. This photoactivated cell preparation is then reinfused into the patient. While the clinical benefits of ECP are well-demonstrated, no study has yet characterized the influence of variations in the composition of the cell preparation on the efficacy of ECP in vitro. Here, we describe a standardized methodology for the in vitro assessment of ECP that uses the human lymphoma T-cell line and mimics the clinical procedure. By quantifying cell apoptosis, inhibition of cell proliferation, and 8-MOP consumption, we used this approach to characterize the specific influence of key variables on the cellular response to ECP. We found that (i) increases in hematocrit and plasma concentrations attenuated the cellular response to ECP; (ii) plasma concentration was the only variable tested that influenced 8-MOP consumption; and (iii) the loss of efficacy due to variations in the concentration of certain blood components could be counteracted by modulating the UVA dose. This methodology may enable evaluation of other leukapheresis preparation protocols and better determination of the optimal working parameters for ECP.