Bhaskara Rao Nallaganchu

Preclinical evaluation of the imipridone family, analogues of clinical stage anti-cancer small molecule ONC201, reveals potent anti-cancer effects of ONC212

ABSTRACT Anti-cancer small molecule ONC201 upregulates the integrated stress response (ISR) and acts as a dual inactivator of Akt/ERK, leading to TRAIL gene activation. ONC201 is under investigation in multiple clinical trials to treat patients with cancer. Given the unique imipridone core chemical structure of ONC201, we synthesized a series of analogs to identify additional compounds with distinct therapeutic properties. Several imipridones with a broad range of in vitro potencies were identified in an exploration of chemical derivatives. Based on in vitro potency in human cancer cell lines and lack of toxicity to normal human fibroblasts, imipridones ONC206 and ONC212 were prioritized for further study. Both analogs inhibited colony formation, and induced apoptosis and downstream signaling that involves the integrated stress response and Akt/ERK, similar to ONC201. Compared to ONC201, ONC206 demonstrated improved inhibition of cell migration while ONC212 exhibited rapid kinetics of activity. ONC212 was further tested in >1000 human cancer cell lines in vitro and evaluated for safety and anti-tumor efficacy in vivo. ONC212 exhibited broad-spectrum efficacy at nanomolar concentrations across solid tumors and hematological malignancies. Skin cancer emerged as a tumor type with improved efficacy relative to ONC201. Orally administered ONC212 displayed potent anti-tumor effects in vivo, a broad therapeutic window and a favorable PK profile. ONC212 was efficacious in vivo in BRAF V600E melanoma models that are less sensitive to ONC201. Based on these findings, ONC212 warrants further development as a drug candidate. It is clear that therapeutic utility extends beyond ONC201 to include additional imipridones.

Abstract 3245: Preclinical evaluation of the imipridone family of small molecules, including analogues of clinical-stage anti-cancer small molecule ONC201, reveals potent anti-cancer effects of ONC212

We previously identified a novel, potent anti-cancer small molecule ONC201, which upregulates the integrated stress response (ISR) through ATF4/CHOP/DR5 and acts as a dual inactivator of Akt and ERK, leading to TRAIL gene activation. After completing a first-in-human phase I clinical trial that revealed exceptional safety, therapeutic pharmacokinetic (PK) profile and tumor engagement, ONC201 is under investigation in several advanced cancer Phase I/II trials. Given the unique imipridone core chemical structure of ONC201, we synthesized a family of analogues in an effort to identify additional chemical family members with distinct therapeutic properties. Based on in vitro potency improvements in human cancer cell lines and therapeutic window approximations with normal human fibroblasts, select analogues were investigated in animals for toxicity, maximum tolerated dose (MTD), and antitumor efficacy. ONC212 is one of the most promising new imipridones that was further evaluated to establish the PK profile, oral bioavailability, and efficacy in tumor types that are less sensitive to ONC201. Compared to ONC201, we noted distinct and more rapid kinetics of activity as well as improved potency in multiple human cancer cell lines in vitro. ONC212 has a broad therapeutic window, an acceptable PK profile, and is orally well-tolerated in mice. With no evidence of toxicity at efficacious doses in both colon and triple negative breast cancer, we have begun further evaluation of antitumor efficacy studies in ONC201-resistant tumor types. Efficacy studies with ONC212 are ongoing in melanoma models that are sensitive to ONC212 but less sensitive to ONC201 in vitro. Preliminary data indicates potent tumor growth reduction by ONC212 in vivo in ONC201-resistant melanoma xenografts. With a wide safety margin, potent antitumor activity in ONC201-insenstive tumors, and drug-like characteristics, ONC212 is being further developed as a drug candidate from the new imipridone class of compounds that complements the spectrum of activity of ONC201. Citation Format: Jessica Wagner, C. Leah Kline, Gary Olson, Bhaskara Nallaganchu, Richard Pottorf, Varun Prabhu, Martin Stogniew, Joshua Allen, Wafik El-Deiry. Preclinical evaluation of the imipridone family of small molecules, including analogues of clinical-stage anti-cancer small molecule ONC201, reveals potent anti-cancer effects of ONC212 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3245. doi:10.1158/1538-7445.AM2017-3245

Abstract 4499: Cytotoxicity, biochemical activity, and structural analysis of ONC201 and comparisons to a biologically inactive isomer

We previously identified TRAIL-inducing compound 10 (TIC10), also known as NSC-350625, as a small molecule being developed under the name ONC201 that has potent anti-tumor efficacy and a benign safety profile in preclinical cancer models. Further investigation of the preclinical profile of this drug candidate led in early 2014 to the FDA acceptance of the investigational drug application (IND) for oral ONC201 to treat patients with advanced cancer. The initially disclosed chemical structure of ONC201 provided by Stahle et. al in an expired patent was described as an imidazo[1,2-a]pyrido[4,3-d]pyrimidine derivative. Our first report of its anticancer activity by Allen et. al. included mass spectrometry and 1H NMR that indicated both were consistent with the structure depicted by Stahle et. al and the National Cancer Institute. A recent publication reported that the structure of ONC201 differs from the initial description and is in fact an angular [3,4-e] isomer of the previously depicted structure. Here, we report X-ray crystallography and other structural studies of ONC201 produced by Oncoceutics in a dihydrochloride salt form for clinical use that confirm the angular [3,4-e] structure and indicate that the material is not a mixture of the two isomers. Furthermore, we confirm that although fragmentation by mass spectrometry for the isomers is identical, the angular [3,4-e] isomer can be definitively identified as ONC201 by implementing specific various spectroscopy techniques to identify differences between ONC201 and the linear isomer. In accordance with our structural analysis, in vitro activity assays in cancer cells indicate that the previously disclosed anti-cancer activity and mechanism of action are indeed associated exclusively with the [3,4-e] structure and not the [4,3-d] linear isomer. Together these studies confirm the angular [3,4-e] structure of ONC201 as the highly active and pure anti-cancer drug candidate that was utilized in prior preclinical pharmacology studies and is now entering clinical trials in several oncology indications. Citation Format: Jessica Wagner, Christina Leah Kline, Richard S. Pottorf, Bhaskara Rao Nallaganchu, Gary L. Olson, David T. Dicker, Joshua E. Allen, Wafik S. El-Deiry. Cytotoxicity, biochemical activity, and structural analysis of ONC201 and comparisons to a biologically inactive isomer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4499. doi:10.1158/1538-7445.AM2015-4499