Effect of AVM0703 treatment on the limitations of R-CHOP and survival in a model applicable to ABC subtype DLBCL.

Abstract

e19060 Background: The current treatment regimen for DLBCL consisting of rituximab-cyclophosphamide-doxorubicin-vincristine-prednisone (RCHOP), is challenged by molecular and prognostic characterization of DLBCL. Activated B-cell (ABC) lymphoma has a significantly worse prognosis (5 yr OS rate: 45% - 56%) than germinal center B-cell (GCB) lymphoma (78% - 80%) after RCHOP treatment. Around 40% of patients ultimately relapse and/or develop primary refractory disease, cardiotoxicity and long-term secondary malignancies. Efforts are being made to improve the RCHOP backbone by including dose intensification and by the addition of new agents to increase the efficacy and reduced toxicity of RCHOP (McKelvey EM Cancer 1976; Wilson WH Blood 2002; Molina TJ JCO 2014; Coiffier B Hematology 2016). AVM0703, an immunomodulatory drug, mobilizes bispecific γδ and inv-TCR double-positive novel T and NKT cells. In a previous study employing an aggressive, immune resistant A20 mouse lymphoma model (Bascuas T J Transl Med. 2016), neoadjuvant AVM0703 was additive/synergistic, when cyclophosphamide/fludarabine (CyFlu) was dosed 3 and 24 hr later, with no additional toxicities. In the present study we combined AVM0703 with RCHOP to evaluate the efficacy in A20 mice model. Methods: 10 week old Balb/c mice were injected with 2x106 murine A20 B-cells in the flank and were randomized (1:1 male: female) into 1) Placebo 2) 3 cycles RCHOP 3) 3 cycles AVM0703 (18mg/kg HED) 4) 3 cycles AVM0703+RCHOP, when tumor size reached ~100 mm3. Mice who achieved complete remission (CR) were re-challenged at 21-25 wks later. Pre and post re-challenge, presence of memory cells was analyzed using flow cytometer. All mice were monitored continuously as per the IACUC protocol. Results: Mice treated with the combination of AVM0703+RCHOP achieved superior CR compared to RCHOP alone, which was not curative in any mice. In first phase of the study, 3 out of 11 AVM0703 +RCHOP treated mice showed CR after only 1-cycle. In second phase, 2 of 12 mice survived in CR for >150 days after 3 cycles, whereas no RCHOP mice survived beyond 2 cycles. AVM0703+RCHOP treated mice in long-term CR, had memory cells (CD44hi-Cd62low) pre- and post re-challenge, and no A20 engraftment, suggesting strong immunological memory induced by AVM0703+RCHOP. Conclusions: AVM+RCHOP demonstrated anti-tumor activity in A20 lymphoma mice, with reduced toxicity, compared to RCHOP. Larger preclinical studies are underway to confirm the activity of AVM0703+RCHOP against RCHOP resistant ABC DLBCL, and the potential to reduce total RCHOP exposure to only 3 cycles while maintaining or improving efficacy. [Table: see text]