Durable Remission after Salvage Chemotherapy with Combining Bortezomib and Vorinostat Followed By CD19 CAR-T Therapy in a Patient with MLL-Rearranged ALL after Early Relapse Post Allogeneic Hematopoietic Stem Cell Transplantation

[Introduction] In infant leukemia, the incidence of mixed-lineage leukemia (MLL) gene rearrangements (now renamed KMT2A) on chromosome 11q23 is 70-80%. Most patients are treated with allogeneic stem cell transplantation (SCT) after several courses of chemotherapy because the prognosis of MLL -rearranged leukemia (MLL -r leukemia) is poor. Unfortunately, despite consolidation with SCT, half of the patients eventually relapse, with a dismal prognosis. Therefore, there is a clinical need for effective salvage therapy in patients with relapse following SCT.

Accumulating data indicate that proteasome inhibitors may represent promising agents to supplement the treatment of MLL -rleukemia. Bortezomib was identified by high-throughput drug screening as an active agent against models of infant MLL -rleukemia. HDAC inhibitors (HDACi) have also been reported to be active in MLL -rleukemia. Recently, a report of six patients with relapsed/refractory MLL -rleukemia treated with chemotherapy, combining a proteasome inhibitor (bortezomib) and HDACi (vorinostat) in combination with cytotoxic chemotherapy, was presented in 2014. The overall response was 83%, including complete response in four patients, partial response in one patient.

Another promising salvage therapy is chimeric antigen receptor gene modified T cell (CAR-T) therapy against CD19. Although several reports have demonstrated 70-90% response rates with CD19 CAR-T therapy, the relapse rate has recently been shown to be associated with disease status prior to CAR-T infusion.

Herein, we report a case of relapsed MLL -r ALL 6 months after SCT. The patient received salvage chemotherapy, combining bortezomib and vorinostat, followed by CD19 CAR-T therapy and remains in complete remission longer than 12 months without the use of other maintenance therapies.

[Case] A 5-month-old girl was referred to our hospital because of pallor that had been noticed 2 weeks prior to admission. A physical examination revealed obvious pallor but no other abnormal findings, such as congenital anomalies. The white blood cell count was 350,000/μl including 94% blasts. A bone marrow examination revealed hypercellular marrow with leukemic blasts. An immunological marker study revealed that the leukemic blasts were CD10⁻CD19⁺HLA-DR⁺ immature B cells. Conventional cytogenetic analysis of the bone marrow demonstrated 46,XX,t(4;11;12)(q21;q23;q13), which resulted in MLL-AF4 fusion. The patient achieved molecular remission after induction therapy and underwent bone marrow transplantation from her HLA-matched father after four additional courses of consolidation chemotherapy. The conditioning regimen comprised intravenous busulphan (4 mg/kg), VP-16 (60 mg/kg), and cyclophosphamide (120 mg/kg). GVHD prophylaxis comprised tacrolimus and methotrexate. Engraftment was achieved prior to the development of grade I acute GVHD. Chronic GVHD was not observed.

The patient developed bone marrow relapse with the detection of a MLL-AF4 transcript and extramedullary relapse with left ethmoid sinus infiltration 6 months after SCT. Tumor biopsy confirmed a relapse of ALL, with the same surface marker of CD10-CD19+ as the initial diagnosis. The MLL-AF4 became negative, and the tumor in the ethmoid sinus shrank after the first course of salvage chemotherapy, including bortezomib and vorinostat. The patient achieved remission after four additional courses of the same chemotherapy. The chemotherapy was well tolerated. The parent refused a second allogeneic SCT as consolidation therapy and elected to enroll in the multi-center 4SCAR19 trial (NCT03050190). Autologous 4SCAR19-T cells were infused after preconditioning with cyclophosphamide (250 mg/m² × 3 days) and fludarabine (25 mg/m² × 3 days). The transduction efficiency of CAR was 13%, and the infused CAR transduced cells was 1.1 × 10⁶/kg. Complete B cell aplasia was maintained up to 6 weeks. Cytokine release syndrome was not observed; however, serum IL-6 level was elevated to 281 pg/ml on day 14. The patient remained in complete remission for more than 12 months after CAR-T infusion without additional therapy.

[Conclusion] Salvage chemotherapy, combining bortezomib and vorinostat, followed by CD19 CAR-T therapy could provide a new treatment option in patients with MLL-r ALL, even after early relapse following allogeneic SCT. [Introduction] In infant leukemia, the incidence of mixed-lineage leukemia (MLL) gene (now renamed KMT2A) on chromosome 11q23 rearrangements is 70-80%. The majority of the patients have undergone allogeneic stem cell transplantation (SCT) after several courses of chemotherapy since the prognosis of MLL -rearranged leukemia (MLL -r leukemia) is poor. Unfortunately, despite the consolidation with SCT half of the patients eventually relapse and the prognosis of relapsed cases is dismal. Therefore the effective salvage therapy for those patients is warranted.

Accumulating data now suggest that proteasome inhibitors may be promising agents to supplement the treatment of MLL-r leukemia. Bortezomib was identified through high-throughput drug screens as an active agent against models of infant MLL-r leukemia. HDAC inhibitors (HDACi) have also been reported by multiple groups to be active in MLL-r leukemia. Recently a report of six patients with relapsed/refractory MLL-r leukemia treated with chemotherapy combining a proteasome inhibitor (bortezomib) and an HDACi (vorinostat) in combination with cytotoxic chemotherapy was presented in 2014. The overall response was 83% including complete response in four patients, partial response in one patient.

Another promising salvage therapy is chimeric antigen receptor gene modified T cell (CAR-T) therapy against CD19 antigen on the leukemic cells. Although several reports demonstrated 70-90% response rate of CD19 CAR-T therapy, it has been noticed recently that relapse rate is associated with disease status before CAR-T infusion.

We here report a patient with relapsed MLL -r ALL 6 month after allogeneic SCT received salvage chemotherapy combining bortezomib and vorinostat followed by CD19 CAR-T therapy and remains complete remission longer than 12 months without any other maintenance therapies.

[Case] A 5-month-old girl was referred to our hospital because of pallor that had been noticed 2 weeks before admission. A physical examination revealed obvious pallor but no other abnormal findings including congenital anomalies. The white blood cell count was 350,000/μl including 94% blast. A bone marrow examination revealed hypercellular marrow with leukemic blast. An immunological marker study revealed that the leukemic blasts were CD10^-CD19⁺HLA-DR⁺ immature B cells. Conventional cytogenetic analysis of the bone marrow showed a 46,XX,t(4;11;12)(q21;q23;q13) which resulted in MLL-AF4 fusion. The patient achieved molecular remission after induction therapy and underwent bone marrow transplantation from her HLA-matched father after additional four courses of consolidation chemotherapies. The conditioning regimen comprised intravenous busulphan (4mg/kg), VP-16 (60 mg/kg), and cyclophosphamide (120 mg/kg) and the GVHD prophylaxis was tacrolimus and methotrexate. Engraftment was achieved and grade I acute GVHD developed. Chronic GVHD has not been observed.

The patient developed bone marrow relapse with the detection of MLL-AF4 transcript and extramedullary relapse with left ethmoid sinus infiltration 6 month after SCT. The tumor biopsy confirmed the relapse of ALL and the surface marker revealed CD10-CD19+ the same as the initial diagnosis. The MLL-AF4 became negative and tumor in ethmoid sinus shrank after the first course of salvage chemotherapy including bortezomib and vorinostat. She achieved remission after additional four courses of same chemotherapies. These chemotherapies were well tolerated. The parent refused second allogeneic SCT as a consolidation and elected to enroll in the multi-center 4SCAR19 trial (NCT03050190). Autologous 4SCAR19-T cells were infused after preconditioning with cyclophosphamide (250mg/m2 x 3 days) and fludarabine (25mg/m2 x 3 days). The transduction efficiency of CAR was 13% and the infused CAR transduced cell was 1.1x10e6/kg. Complete B cell aplasia continued up to 6 weeks. No cytokine release syndrome was observed while serum IL-6 was elevated to 281 pg/ml at day 14. The patients remained complete remission longer than 12 months after CAR-T infusion without additional therapy.

[Conclusion] The salvage chemotherapy combining bortezomib and vorinostat followed by CD19 CAR-T therapy could provide a new treatment option in the patient with MLL-r ALL even after early relapse post allogeneic SCT.