Methoxsalen and Extracorporeal Photopheresis (ECP) for the Treatment of Pediatric Participants With Steroid Refractory Acute Graft Versus Host Disease

This is a single-arm, open-label, multicenter study of the efficacy of UVADEX® (methoxsalen) Sterile Solution in conjunction with THERAKOS® CELLEX® Photopheresis Systems (ECP) in pediatric participants with steroid-refractory aGvHD. The study is composed of Screening, Treatment, and Follow-up Periods.

Screening:

After the informed consent/assent form (ICF) is signed, the screening assessments will be performed in a single visit to establish the eligibility of the participant, based on inclusion and exclusion criteria, as well as aGvHD grading. Scheduling of the first week of ECP treatments and the arrangements for availability of typed and cross-matched donor packed red blood cells (PRBCs) for transfusion, if required, will be made in advance of participants entering the Treatment Period.

Treatment Period:

Once eligibility is established, participants will enter the 12-week ECP Treatment Period. The availability of typed and cross-matched donor PRBCs for transfusion during treatment, if needed, should be established prior to the scheduling of ECP treatments.

Participants will be allowed to continue standard aGvHD prophylaxis regimens (e.g., cyclosporine, tacrolimus, methotrexate, mycophenolate mofetil) without the addition of new therapies. Participants will be allowed to discontinue prophylaxis regimens for reasons of toxicity, and will also be allowed to switch to another prophylaxis medication within the same class (e.g., the calcineurin inhibitors cyclosporine and tacrolimus) for reasons of toxicity.

All participants enrolled in this trial will have received corticosteroids for the treatment of aGvHD. After entering the treatment period on study, tapering of steroids by total weekly decrements of 12.5% to 25% of the steroid dose at initiation of ECP therapy is permitted after a sustained response of aGvHD has been observed for at least 3 consecutive days, with the suggested goal to decrease the starting steroid dose by at least 50% 4 weeks after initiation of ECP.

Follow-Up Period:

After completion of the 12-week Treatment Period, participants may continue ECP treatment on commercial product at the Principal Investigator's discretion. Acute GvHD status will be assessed 4 weeks after completion of the Treatment Period. Participant survival will be assessed by passive follow-up (chart review) 26 weeks after initiation of ECP treatment.

Eligibility Criteria:
Inclusion:

1. Male or female 1 to 21 years of age at the time of consent
2. Steroid-refractory grade B-D aGvHD.

   * Steroid-refractory is defined as a failure to respond to steroid treatment, with failure to respond defined as any grade B-D (IBMTR grading) aGvHD that shows progression ≥ 3 days, or no improvement by 5 days of treatment with 2 mg/kg/day methylprednisolone or equivalent in participants with lower gastrointestinal (GI) or liver disease, or skin disease associated with bullae. Grade D organ involvement will be limited to skin and liver.
   * Steroid refractory may also be defined as a failure to respond to 1 mg/kg/day of methylprednisolone or equivalent in participants with disease confined to upper GI disease or lesser degrees of skin GvHD
   * Participants with lack of complete response after 2 weeks of steroid treatment
3. A Lansky scale Performance Status score ≥ 30
4. Laboratory values are within the following limits, assessed within 3 days of the first study treatment:

   * Absolute neutrophil count \> 0.5 × 10\^9/liter (L)
   * Creatinine level \< 2 times the upper limit of normal
5. For participants with isolated upper GI symptoms, pre-Screening biopsy results to confirm diagnosis of aGvHD
6. Female participants of childbearing potential and nonsterilized males who are sexually active with a female partner must be practicing highly effective, reliable, and medically approved contraceptive regimen throughout their participation in the study and for 3 months following the last ECP treatment. Or, for the US only, abstinence may be used in place of an approved contraceptive regimen. Females of childbearing potential are those who have reached the onset of menarche, or 8 years of age, whichever comes first. Approved contraceptive methods for female participants of childbearing potential or nonsterilized males who are sexually active with a female partner are as follows:

   * Barrier methods of contraception: condom or occlusive cap (diaphragm or cervical/vault caps) with spermicidal foam/gel/film/cream/suppository
   * Established use of oral, injectable, or implanted hormonal methods of contraception.
   * Placement of an intrauterine device or intrauterine system
7. Signed informed consent/assent is obtained before conducting any study procedures; the parent, legal guardian, or legally authorized representative of a minor must also provide written informed consent

Exclusion:

1. Currently enrolled in another clinical trial for the treatment of aGvHD
2. Use of any experimental regimens or medication(s) for aGvHD treatment
3. Treatment with \> 2.0 mg/kg/day of methylprednisolone equivalents for aGvHD within 30 days prior to the first study treatment
4. Overt signs of relapse of the underlying condition
5. Uncontrolled viral, fungal, or bacterial infection
6. Platelet count \< 20.0 × 10\^9/L, despite platelet transfusion
7. Inability to tolerate the extracorporeal volume shifts associated with ECP treatment
8. Uncontrolled GI bleeding
9. Veno-occlusive liver disease
10. Life expectancy \< 4 weeks
11. Participant requires invasive ventilation or vasopressor support
12. Known human immunodeficiency virus (HIV) or hepatitis B or C virus infection (proof of seronegativity within 6 months of screening is required)
13. Known allergy or hypersensitivity to methoxsalen, Uvadex, or its excipients
14. Known hypersensitivity and allergy to heparin and Anticoagulant Citrate Dextrose Formula-A (ACD-A)
15. Co-existing photosensitive disease (e.g., porphyria, systemic lupus erythematosus, albinism) or aphakia
16. Coagulation disorders that cannot be corrected with simple transfusion
17. Co-existing melanoma, basal cell, or squamous cell skin carcinoma
18. Previous splenectomy
19. White blood cell count greater than 25,000 cubic millimeter (mm\^3)
20. Currently being treated with any systemic immunosuppressive or biologic therapy for the treatment of a medical condition other than aGvHD
21. Female participant is breastfeeding or pregnant
22. Any medical concerns that may pose risk to the participant
23. Any psychological, familial, sociological, and/or geographical condition that may potentially hamper compliance with the study protocol and follow-up schedule