A Novel, Closed-Line Mini Extracorporeal Photopheresis (ECP) Technique Using the Therakos ^TM CellEx ^TM Photopheresis System, Developed for Patients with Contraindications Against Conventional ECP Therapy

Introduction: Conventional ECP has proven efficacy for treating several diseases, most significantly steroid-refractory chronic GVHD. Unfortunately, body weight and sufficient venous access limit the availability of this treatment modality. Children, in particular, usually have limited access to ECP. A simplified mini buffy coat ECP technique that allows treating small children and patients with apheresis contraindications has been tested in selected cases during the last 20 years. However, this method relies on an open-line system that requires a longer time and a cell processing laboratory, making this approach challenging.

A new -closed-line- method, using the Therakos ^TM CellEx ^TM Photopheresis System, has been developed and evaluated in our Center. This method requires no processing laboratory or other special equipment and takes only 60-120 minutes, making the procedure potentially usable in routine practice.

Design and methods: A 7-year-old girl had been treated at our Pediatric Bone Marrow Transplantation Unit with grade IV chronic steroid-refractory GVHD (skin, and less severe liver involvement). As all other options were exhausted, ECP became a desirable form of treatment. However, the patient's low body weight and serious venous access problems hindered conventional ECP treatment.

We developed a solution that requires 200-250 ml whole blood collection from the patient, takes less than 2 hours, does not need special cell processing equipment, and allows the ECP treatment to commence in the form of a regular autotransfusion.

Consent forms were obtained from the patient's caregivers as well as from the local Ethical Committe.

The patient's age at the start of treatment was seven years, and her body weight was 28 kg. A total of 17 mini-ECPs were performed weekly up until the submission of this abstract, and the number of treatments per patient was 33. The duration of mini-ECP treatment has been five months.

5 to 8 mL/kg of whole blood was drawn from the patient. Separation of the white blood cell (WBC) rich buffy coat of the patient's blood - with donor blood product supplementation as needed - was performed through an individualized use of the CellEx ^TM photopheresis kit and blood prime program. The buffy coat was ultraviolet A (UVA)-irradiated after adding 8-methoxypsoralen (8-MOP) within the Therakos ^TM CellEx ^TM Photopheresis System and divided into two fractions under a laminar air flow cabinet. The autologous residual blood with the first fraction of the UVA irradiated buffy coat was transfused immediately. The second buffy coat fraction was stored at 4 °C and transfused the following morning through a peripheral vein.

Results : The median volume of the collected whole blood was 250 mL (203-250 mL). The median volume was 72 ml (48-88 mL) for the first fraction of the irradiated buffy coat and 71 ml for the second fraction (48- 88 mL). Apoptosis and cell death were analyzed by annexin V staining; apoptosis and lymphocyte proliferation was measured by flow cytometry. UVA irradiation of the 8-MOP infused buffy coat resulted in significant induction of WBC apoptosis at 24 hours.

No clinical side effects were observed during mini ECP treatment; all microbiological control tests were negative. Partial response was observed within three months (skin), and the tapering of systemic immunosuppression (methylprednisolone and ruxolitinib) began at five months.

Conclusion: Mini whole blood ECP induces apoptosis and lymphocyte proliferation inhibition, both occurring after standard ECP. The closed-line method requires no special equipment and is not demanding for the patient, providing a viable solution to the technical difficulties children with the need for ECP treatment face.