Ph1/2 Study of the Imipridone ONC201 for Treatment of AML IND125,203 (12/23/2014)

Project Summary/Abstract
Survival rates (app. 30 %) of acute myeloid leukemia (AML) have not been improved over 4 decades, except in
some specialized instances. The long term aim of this study is to increase the cure rates of AML through
clinical implementation of targeting a new cellular survival mechanism, i.e. mitochondrial (mt) unfolded protein
response (mtUPR). We are proposing to conduct a clinical Phase 1/2 trial of ONC201, a first-in-class
imipridone and to confirm and further investigate the underlying novel mechanism of action (MOA). We
discovered in extensive preclinical studies that ONC201 induces apoptosis in AML but not in normal cells.
Importantly, ONC201 has great efficacy in p53-mutated AML, the most chemotherapy-resistant subset, as well
as in p53 wild-type AML. Our preclinical studies further demonstrate that ONC201 eliminates functionally-
defined leukemia stem cells in patient-derived xenografts. Early trials initiated at MD Anderson show excellent
tolerability of ONC201, micromolar plasma concentrations, and early clinical responses. We previously
reported that ONC201 induces apoptosis mediated by the transcription factor ATF4, a hallmark of integrated
stress response (ISR). However, ONC201 did not induce all characteristic molecular changes associated with
classical ISRs (e.g., ER stress), suggesting an atypical MOA to induce ATF4. As break through progress
reported in this re-submission, we have discovered that ONC201 directly binds and activates the mitochondrial
protease, ClpP, resulting in selective mitochondrial proteolysis. The resultant reduction of mt protein pools
induces so-called mt protein folding stress (mtPFS) and the protective transcriptional response against mtPFS
termed mt unfolded protein response (mtUPR). Importantly, ATF4 is known to be induced through mtUPR,
connecting our previous findings on ATF4 in a way different from classical ISRs. We here hypothesize that
AML progenitor and stem cells are more susceptible to mtPFS than normal cells, and that ONC201 is targeting
a novel point of vulnerability in AML pathobiology. The proposed clinical trial in leukemia provides a unique
opportunity to thoroughly investigate this hypothesis. We will conduct a Phase 1/2 study of ONC201 in AML
(Aim 1), and evaluate the underlying MOA (Aim 2). The Phase 1 trial will determine the safety and preliminary
efficacy of ONC201 and Phase 2 the overall response rate. Changes in ATF4, mtUPR effector proteins, mt
function and biogenesis in AML cells will be investigated using standard immunoblot and PCR methods as well
as novel tools including CyTOF (single cell proteomics). We will also determine if ClpP, ATF4 and mtUPR
effector proteins are potential biomarkers of clinical response to ONC201. Changes in clonal architecture will
be monitored by flow cytometry and single-cell DNA sequencing. Genome-wide RNAseq will also be performed
to further elucidate MOA and potential resistance. We expect these studies, which are at the cutting edge of
our evolving knowledge of mitochondrial pathophysiology, to be developed into a highly effective and novel
concept for the treatment of AML.

Grant Number: 5R01FD006118-04
NIH Institute/Center: FDA
Principal Investigator: MICHAEL ANDREEFF