Evolution to Plasmablastic Lymphoma (PBL) after CAR-T Cell Therapy in a Case of SLL/CLL with Richter’s Transformation
Authors: Evans Andrew , Burack Richard , Rothberg Paul G. , Porter David , Liesveld Jane L. 
Published: October 2019

Abstract
Chimeric antigen receptor (CAR)-modified T cells specific for CD19 have resulted in complete responses in B lymphoblastic leukemia (B-ALL) and in chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL). In B-ALL cases, clinical relapse with CD19-negative cells has been reported (Grupp et al NEJM 368; 1509-18). Here we report relapse in a CLL case treated with CAR-T cells specific for CD19 (CTL019) which demonstrated clonal evolution into plasmablastic lymphoma (PBL) lacking residual markers of B lymphoid differentiation.
The patient was a 62 year old man diagnosed with CLL 4.5 years prior to the CTL019 therapy. At diagnosis his absolute lymphocyte count was 253K/uL, with 98% of lymphocytes being positive for CD19, CD20, CD5(dim), CD23, and lambda-restricted, but negative for CD10, CD38, and Zap-70. CT scans revealed splenomegaly (16 cm) and extensive lymphadenopathy (up to 6.9 cm). Standard CLL FISH panel was negative. Brief therapeutic responses were achieved but progression occurred on each of the following regimens: fludarabine, cyclophosphamide and rituximab for 6 cycles, bendamustine/rituximab for 2 cycles, ofatumumab for 5 infusions, and CHOP for 3 cycles. He was then enrolled on a series of clinical trials including flavopiridol and PCI 32765 (ibrutinib). Six months prior to CTL019 infusion, further node progression was demonstrated with trisomy 12, del 12p14, del 11q, and del 17p by FISH. Node and marrow biopsies were consistent with large B cell/Richter’s transformation. He received OFAR X 1 and was referred for the CTL019 CLL trial at the University of Pennsylvania where he had successful apheresis and expansion of T cells. Nodes were debulked with the XP01 inhibitor (KPT-330). He received radiation to a 9 cm right axillary mass without response. He received one cycle of fludarabine and cyclophosphamide followed by CTL019 cell infusion. There was marked expansion of CTL019 cells and he experienced cytokine release syndrome. He had a significant tumor response with 50% or more reduction in most nodal areas on CT scan and 80% reduction in tumor involvement of the marrow 1 month after infusion. He was lymphopenic and received monthly IVIG replacement.
Approximately 6 months after the CTL019 infusion, he developed right jaw pain. A gingival biopsy revealed plasmablastic lymphoma (PBL). The cells were lambda-restricted by in-situ hybridization, and positive for CD45, CD138, MUM-1, CD56 (subset), and EMA, but negative for CD19, CD20, Pax-5, CD5, CD23, BCL-2, cyclin D1, CD30, ALK-1, HHV-8, and EBV (by EBER in situ hybridization). The Ki67 expression was >90%. At the time WBC was 3.7K/uL, HCT 44%, and platelets 78K/uL with ANC 2.2K/uL. About one month after relapse, neutropenia occurred, and atypical cells emerged which typed by flow cytometry as positive for CD45(dim), CD5, CD23, CD81, lambda-restricted, and negative for CD19. The patient developed sepsis with pancytopenia and died 7 months after his CTL019 cell infusion.
Molecular analysis revealed the same size monoclonal gene rearrangements of the immunoglobulin heavy chain (IGH) and kappa light chain (IGK) genes in both the PBL, subsequent peripheral blood, and a prior SLL (2010) lymph node biopsy. Sequencing revealed identical productive and nonproductive IGH gene rearrangements in all three specimens, with the exception of a 2bp insertion in the CDR1 region which destroyed the IGH reading frame in the PBL. P53 sequencing revealed multiple mutations [p.Gly245Ser(heterozygous) and p.Val197Glu(heterozygous)] from the prior SLL lymph node and recent peripheral blood, but only a single mutation [p.Gly245Ser(homozygous)] present in the PBL, consistent with previously documented loss of 17p prior to CTL019 therapy.
CAR-T cell therapy is an effective treatment modality for CLL and ALL. In this case, a plasmablastic lymphoma lacking well-differentiated B cell features, including CD19, emerged 6 months after CTL019 therapy, along with residual circulating CD19-negative/CD5-positive lambda-restricted B cells. This finding suggests that anti-CD19 selective pressure may divert lymphoid differentiation into other pathways or may foster proliferation of an alternatively differentiated stage of the original clonal tumor. This case demonstrates the ability of CD19-negative tumors to emerge after CD19 directed therapy in CLL, which also attests to the efficiency and continued activity of these directed T cells over time.

Disclosures
Porter: Novartis: Patents & Royalties, Research Funding. Liesveld:Glycomimetics: Honoraria, Membership on an entity's Board of Directors or advisory committees; GSK: Honoraria, Membership on an entity's Board of Directors or advisory committees.