Trial in Progress: A Phase II Trial of Belinostat As Consolidation Therapy with Zidovudine for Adult T-Cell Leukemia-Lymphoma (ATLL)

Background: Adult T-cell leukemia-lymphoma (ATLL), a lymphoid malignancy associated with human T-cell leukemia virus type 1 (HTLV-1), is endemic in regions such as southwestern Japan, the Caribbean basin, and parts of South America, and central Africa where HTLV-1 is prevalent. Generally, ATLL cannot be cured with chemotherapy alone, and has dismal long-term outcomes. Previous clinical trials have only yielded modest results. Zidovudine (ZDV) is a synthetic nucleoside analog that inhibits reverse transcriptase and DNA polymerase resulting in inhibition of DNA replication and cell proliferation. Studies have demonstrated ZDV plus interferon (IFNα) therapy, as induction, followed by maintenance therapy, can be an efficacious first line treatment in leukemic forms of ATLL. A meta-analysis showed ZDV/IFNα therapy compared better to conventional chemotherapy for acute and chronic leukemic type ATLL in terms of overall survival. NCCN guidelines include ZDV/IFNα as a first-line therapy option for ATLL. While ZDV-IFNα can be effective in some ATLL patients, as with chemotherapy, molecular response rates are suboptimal, and patients usually relapse and succumb to their disease. Therefore, new therapeutic approaches and strategies are urgently needed to treat ATLL. Belinostat, a pan-HDAC inhibitor, obtained accelerated approval in 2015 for treatment of relapsed/refractory PTCL based on efficacy and duration of response. We hypothesize that belinostat will exert anti-neoplastic effects in ATLL cells through a variety of molecular mechanisms including activation of silenced key cellular genes and suppression of HBZ (only HTLV-1 protein consistently expressed in all ATLL tumors) and through HDAC inhibition, belinostat will reactivate HTLV-1 provirus in ATLL cells and infected T-cell reservoirs, thus eliciting an immune response against virus infected cells. Here, we describe a trial designed to evaluate safety and response of belinostat in combination with ZDV as consolidation therapy for treatment of ATLL. Correlative studies include measuring HTLV-1 reactivation in peripheral blood T-cells, assessing cytotoxic T-cell response in vivo, and investigating molecular effects of belinostat in ATLL cells in vivo. Study Design: This phase 2, single arm, open-label trial will evaluate the combination of belinostat and ZDV as consolidation therapy followed by standard ZDV-based maintenance therapy with optional IFNα-2b or pegylated interferon-alfa-2b (PEG-IFN-α-2b). The study will include up to 20 adult participants with histologically or cytologically documented ATLL, HTLV-1 infection, who have achieved and maintained at least a partial hematologic response to prior ZDV/IFNα therapy or chemotherapy. Residual ATLL in peripheral blood is required prior to enrollment. Patients must have measurable, clinically evaluable or molecular disease, with adequate end organ and bone marrow function (unless due to lymphomatous infiltration) and KPS ≥50% or ECOG performance status ≤3. The active study period includes a treatment period of up to 8 cycles (21 days each = ~6-months). Additional assessments will occur at the end of Cycle 8, Month 9, Month 12 and an end-of-treatment visit (≤ 30-days after the last dose of study treatment). Patients who achieve/maintain CR and complete 1 year of therapy will undergo follow-up assessments every 3 months for 1 year, and survival assessment every 6 months up to Year 5. ZDV will be administered in the outpatient setting as 300mg tablets orally, three times daily, starting at least 24-hours prior to the first dose of belinostat. Belinostat will be administered as 1,000 mg/m 2 IV infusion over 30 minutes on Days 1-5, every 21 days, on cycles 1- 8, followed by continuation of ZDV (+/- IFN-α) as maintenance therapy up to the end of Month 12. ZDV may be administered for a minimum 12 months from the beginning of the study. Primary objectives are to evaluate safety and determine complete molecular response rate after addition of belinostat as consolidation therapy for ATLL during ZDV-based maintenance treatment. Secondary outcomes will include evaluation of clinical response rates, investigation of whether belinostat disrupts HTLV-1 latency load in vivo, investigation of whether belinostat provokes immune or cytotoxic T-cell response in vivo and determine the impact of belinostat/ZDV (+/- IFNα) on HTLV-1 proviral load (measure of HTLV-1 infected reservoirs), in vivo. Figure 1 Figure 1. Disclosures No relevant conflicts of interest to declare.