CASE DESCRIPTION
Our patient is an African American female diagnosed at 6-weeks of age who presented for evaluation of persistent vomiting, lethargy and an unusual skin rash after several weeks of concern for failure to thrive. Initial white blood cell (WBC) count was 834x109/L with 98% circulating lymphoblasts. Flow cytometry performed on peripheral blood revealed ALL with 98% of total cells expressing CD19. Cytogenetic analysis revealed a t(11;19)(q23.3;p13.3) translocation and flouresent in situ hybridization analysis confirmed a KMT2A-r ALL. Cerebrospinal fluid (CSF) analysis revealed central nervous system (CNS) involvement. The patient underwent leukoreduction and subsequently initiated treatment as per the Interfant-06 standard protocol (clinigaltrials.gov: NCT00550992).
End of induction assessment demonstrated clearance of the extra-medullary disease and a bone marrow morphologic remission but flow cytometric evidence of minimal residual disease of 0.36%. Three months after diagnosis she relapsed with confirmed ALL detected in the bone marrow and CSF with chloromatous skin lesions following a period of delayed blood cell count recovery from consolidation therapy. She received high-dose methotrexate (HD-MTX) (3.3gm/m2) with 6-mercaptopurine (6MP) and intrathecal methotrexate/hydrocortisone (IT MTX/HC) that resulted in clearance of peripheral blood and CSF lymphoblasts and resolution of chloromas.
She underwent autologous CD3 lymphocyte apheresis using the CMNC program in the Spectra Optia automatic apheresis system for CAR-T generation over a course of 3 collection days at the age of 5-months and weighing 6.8kg. The device was primed with whole blood which was reinfused to her at the completion of the procedures. Absolute lymphocyte count (ALC) at the start of collection was 0.88x109/L. On day 1 the product output was poor with a total nuclear cell count (TNC) of 0.14x109/L and a CD3 count of 0.02x109/L cells.
Adjustments were made for collection on days 2 and 3. On day 2, the TNC obtained was 1.4x109 and the CD3 count was 0.42x109 cells. Day 3 yielded 2.64x109 TNC and 0.31x109 CD3 lymphocytes. The procedure totaled 4.18x109 TNC and 0.76x109 CD3 cells over 3 days. Despite her small size, the cellular goals for apheresis were the same as for an adult and were appropriately met without any complications.
CNS and peripheral blood lymphoblasts re-emerged following chemotherapy with high dose cytarabine and pegaspargase but cleared following HD-MTX (3.75gm/m2), 6MP, dexamethasone, vincristine and IT MTX/HC. Lymphodepleting therapy with a 2-day course of cyclophosphamide and fludarabine was administered 7 days prior to tisagenlecleucel infusion. The total cell viability in the final CAR-T product was 85.4% with 2.7% CAR positive viable cells, below the 3% threshold required by the Food and Drug Administration (FDA) for product release. However, the overall number of chimeric antigen receptor (CAR) viable transduced T-cells was 2.3x106 cells/kg, meeting the clinical specifications required for commercial use.[23] As the final product did not meet all the required specifications, she received the manufactured cells on compassionate use exemption at 7-months of age.
Figure-1 summarizes her WBC count, lymphoblast count, C-reactive protein, ferritin, fibrinogen, maximum daily temperature and clinical course following CAR-T infusion. Her course was complicated by grade 2 cytokine release syndrome (CRS) in conjunction with the emergence of confirmed CD19 lymphoblasts detected in peripheral blood on day 7. CRS was manifested by persistent high fevers, tachycardia, tachypnea and grunting. She received two doses of tocilizumab on days 7 and 10. She developed tumor lysis syndrome (TLS) and subsequent acute kidney injury manifested by an increase in creatinine from 0.32mg/dL to 0.61mg/dL. She subsequently developed Klebsiella pneumoniae bacteremia, disseminated intravascular coagulation and unexplained hypoglycemia. Full recovery from TLS and CRS occurred following the clearance of peripheral lymphoblasts by day 13. She was discharged home on day 26 in remission confirmed by morphologic and flow cytometric assessment of bone marrow.
At 9-months old she proceeded with a planned myeloablative (busulfan/cyclophosphamide) haploidentical allogeneic HSCT from her 14-year old sister. Tacrolimus and mycophenolate mofetil were used for graft-vs-host-disease prophylaxis. She developed reversible hyperbilirubinemia, transaminitis and hepatomegaly. Complications included Klebsiella pneumoniae bacteremia, mucositis, hypertension and pericardial effusion. She was discharged on day 34 in remission confirmed by CSF evaluation and morphologic and flow cytometric analysis of her bone marrow. She is now 12-months post-HSCT and remains in a remission.