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The investigation of extracorporeal photopheresis (ECP) plus standard of care (SoC) (SoC+ECP) in chronic graft-versus-host disease (cGVHD) within prospective, randomized clinical studies is limited, despite its frequent clinical use. This phase 1/pilot study was the first randomized, prospective study to investigate ECP use as first-line therapy in cGVHD, based on the 2015 National Institutes of Health (NIH) consensus criteria for diagnosis and response assessment. Adult patients with new-onset (≤3 years of hematopoietic stem cell transplantation) moderate or severe cGVHD were randomized 1:1 to 26 weeks of SoC+ECP vs SoC (corticosteroids and cyclosporine A/tacrolimus) between 2011 and 2015. The primary endpoint was overall response rate (ORR), defined as complete or partial response, at week 28 in the intention-to-treat population (ITT). Other outcomes included quality of life (QoL) measures and safety. Sixty patients were randomized; ITT included 53 patients (SoC+ECP: 29; SoC: 24). Week 28 ORR was 74.1% (SoC+ECP) and 60.9% (SoC). Investigator-assessed ORR was 56.0% (SoC+ECP) and 66.7% (SoC). Patients treated with SoC experienced a decline in QoL over the 28-week study period; QoL remained unchanged in SoC+ECP patients. Most frequent treatment-emergent adverse events (TEAEs) in SoC+ECP patients were hypertension (31.0%), cough (20.7%), dyspnea (17.2%), and fatigue (17.2%). Seventeen patients (SoC+ECP: 8; SoC: 9) experienced 35 serious adverse events (SAEs). No TEAEs or SAEs were considered related to the ECP instrument or methoxsalen. The encouraging short-term results of this study could inform the design of subsequent studies. This trial was registered at www.clinicaltrials.gov as #NCT01380535.

Background: Steroid-refractory acute graft-versus-host disease (SR-aGvHD) is a major cause of morbidity and mortality after allogeneic hematopoietic stem cell transplant in pediatric patients. Second-line therapies cause further immunosuppression, leaving patients vulnerable to life-threatening infections. Extracorporeal photopheresis (ECP) with methoxsalen (Uvadex®) sterile solution, in which apheresed leukocytes are photosensitized, exposed to ultraviolet A radiation ex vivo, and reinfused, is used to treat aGvHD because it has a low risk of infection, unlike systemic immunosuppressants. Safe use of ECP in children is not yet established. Aims: To report interim 4-week data from a 12-week phase 3 study evaluating the efficacy and safety of ECP using the photosensitizing agent methoxsalen with the Therakos® Cellex® Photopheresis System (Cellex; Mallinckrodt Pharmaceuticals, Bedminster, NJ) in pediatric/young adult patients with SR-aGvHD (NCT02524847). Methods: In this single-arm, open-label study, patients (aged 1-21 years; SR-aGvHD International Bone Marrow Transplant Registry [IBMTR] grade B-D) received ECP 3 times/wk for 4 weeks, followed by 2 times/wk for 8 weeks. Steroids were tapered according to physician discretion if SR-aGvHD responded to ECP. The primary endpoint was proportion of patients with an overall response (OR), defined using the Modified IBMTR Severity Index as complete response (CR; complete resolution of aGvHD in all evaluable organs, without next-line systemic treatment) or partial response (PR; improvement of 1 stage in ≥1 aGvHD target organ without progression in others or addition of next-line systemic treatment), after 4 weeks. The primary endpoint was considered significant if P48%. Secondary outcome measures included safety, duration of response, steroid-sparing effect, and organ-specific response. Results: Of 25 patients enrolled, 25 were evaluable for safety (patients who received ≥1 ECP treatment) and 23 were evaluable for efficacy. Patients' mean age was 9.2 years, 44% were female, mean body mass index was 18.3 kg/m2, and the majority (n=18) had Grade 3 aGvHD. Twelve patients (48%) completed all study visits; 5 withdrew early (2 deaths, 1 CR; 3 withdrew due to inadequate efficacy, 2 of whom started second-line therapy, and 3 no longer required treatment) A median of 27 ECP treatments were administered (range 3-28). OR was 61% (14/23 evaluable patients); there were 3 CRs (13%) and 11 PRs (48%; P Disclosures Kitko: Mallinckrodt: Honoraria; Novartis: Consultancy, Honoraria. Boodée:Mallinckrodt Pharmaceuticals: Employment. OffLabel Disclosure: UVADEXÃ'® (methoxsalen) Sterile Solution is indicated for extracorporeal administration with the THERAKOSÃ'® UVAR XTSÃ'® or THERAKOSÃ'® CELLEXÃ'® Photopheresis System in the palliative treatment of the skin manifestations of Cutaneous T-Cell Lymphoma (CTCL) that is unresponsive to other forms of treatment. Extracorporeal photopheresis (ECP) with methoxsalen (UvadexÃ'®) sterile solution is used to treat acute graft-versus-host disease (aGvHD), but there are few clinical trials in pediatric patients. This abstract reports on the interim results of a phase 3 clinical trial of ECP with methoxsalen used with the TherakosÃ'® CellexÃ'® Photopheresis System in pediatric/young adult patients with steroid refractory aGvHD.