ONC201/TIC10 Is Effective As a Monoagent and Synergizes with Chemotherapy to Induce Cell Death in Non-Hodgkin Lymphoma

Outcome for Non-Hodgkin lymphoma (NHL) patients using conventional treatment standards remains unsatisfactory, particularly in advanced stage/ relapsed disease creating an imminent need for investigating novel treatment strategies. ONC201/TIC10 is a small molecule (Allen et al, 2014) that induces p53-independent cell death in tumor cells (sparing normal cells) through inactivation of prosurvival kinases Akt and ERK. ONC201 is scheduled to enter Phase I/II clinical trials as a monoagent for advanced cancers in adults in 2014. We have previously shown that ONC201 induces significant cytotoxicity in preclinical models of human lymphomas (Talekar et al, ASPHO 2014). Here, we show that ONC201 is not only effective as a monoagent across several NHL cell lines, but that it also synergizes with several chemotherapeutic agents to cooperatively induce cell death in vitro.

We found that ONC201 induces significant apoptosis in a diverse panel of seven human NHL cell lines at low micromolar concentrations (1.3 to 5.06 uM). Increased surface TRAIL and surface DR5 expression was noted in a dose-dependent manner across representative cell lines. The increase in surface TRAIL correlated with increase in subG1 DNA content, which suggests TRAIL as a potential biomarker of ONC201 response. ONC201-induced apoptosis was inhibited using a pan-caspase inhibitor and was blocked by an anti-TRAIL antibody RIK-2. Western blot analysis of ONC201-treated representative cell lines suggests ERK inhibition and Foxo3a activation as a potential mechanism of cytotoxicity via TRAIL induction. In agreement with this notion, we observed upregulation of PARP & DR5 and caspase-3 activation in response to ONC201 treatment.

We further found that ONC201 synergizes to potentiate cytotoxicity with several chemotherapeutic agents approved for NHL treatment, particularly anthracyclines (doxorubicin), nitrogen mustard (bendamustine), antimetabolite (cytarabine) and proteasome inhibitor (bortezomib) via CellTiter-Glo cell viability experiments that were corroborated by apoptosis assays.

Together these results suggest that ONC201 is a potent antitumor agent in NHL as monoagent and in combination with approved therapies. The ultimate goal of this project is to provide a preclinical rationale for a phase Ib/II trial of ONC201 as a combination therapy in pediatric lymphoma.