Richard S. Pottorf

Parallel synthesis of benzoxazoles via microwave-assisted dielectric heating

A facile route to benzoxazoles has been developed using microwave-assisted dielectric heating. The ease of synthesis and workup allowed the parallel synthesis of a 48-membered library of benzoxazoles quickly and efficiently.

Discovery and clinical introduction of first-in-class imipridone ONC201

ONC201 is the founding member of a novel class of anti-cancer compounds called imipridones that is currently in Phase II clinical trials in multiple advanced cancers. Since the discovery of ONC201 as a p53-independent inducer of TRAIL gene transcription, preclinical studies have determined that ONC201 has anti-proliferative and pro-apoptotic effects against a broad range of tumor cells but not normal cells. The mechanism of action of ONC201 involves engagement of PERK-independent activation of the integrated stress response, leading to tumor upregulation of DR5 and dual Akt/ERK inactivation, and consequent Foxo3a activation leading to upregulation of the death ligand TRAIL. ONC201 is orally active with infrequent dosing in animals models, causes sustained pharmacodynamic effects, and is not genotoxic. The first-in-human clinical trial of ONC201 in advanced aggressive refractory solid tumors confirmed that ONC201 is exceptionally well-tolerated and established the recommended phase II dose of 625 mg administered orally every three weeks defined by drug exposure comparable to efficacious levels in preclinical models. Clinical trials are evaluating the single agent efficacy of ONC201 in multiple solid tumors and hematological malignancies and exploring alternative dosing regimens. In addition, chemical analogs that have shown promise in other oncology indications are in pre-clinical development. In summary, the imipridone family that comprises ONC201 and its chemical analogs represent a new class of anti-cancer therapy with a unique mechanism of action being translated in ongoing clinical trials.

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 349: Structure-activity relationships and mechanistic analysis of analogues of the clinical-stage anti-cancer small molecule ONC201

TRAIL is an endogenous protein that initiates apoptosis selectively in cancer without toxic side effects, prompting interest in therapeutic modulation. We previously screened for small molecules that could upregulate the endogenous TRAIL gene to trigger apoptosis and restore anti-tumor immunity within tumor cells in a p53-independent manner. We showed that ONC201 (previously referred to as TIC10) is a dual inactivator of Akt and ERK, leading to nuclear translocation of Foxo3a and TRAIL gene activation (Allen et al., Science Translational Medicine, 2013). We recently found that ONC201 causes an early-stage upregulation of the integrated stress response through ATF4/CHOP/DR5 (Kline et al., Science Signaling, in press) and can inhibit cancer stem cell self-renewal (Prabhu et al., Cancer Research, 2015). ONC201 recently completed its first-in-man phase I clinical trial and several other trials in select advanced cancers are ongoing (NCT02250781, NCT02324621, NCT02420795, NCT02392572, NCT02609230, NCT02525692, NCT02038699). Leveraging the unique pharmacophore of ONC201, we synthesized ONC201 analogues in search for compounds with distinct therapeutic properties. After establishing the importance of the pyrido[3,4-e]pyrimidinone core structure of ONC201 in its anti-tumor activity (Wagner et al., Oncotarget, 2014), we performed detailed structure activity relationship (SAR) studies. We evaluated several ONC201 analogues with differing N-substituents around the core structure. Certain ONC201 analogues exhibit more rapid kinetics of activity and lowered IC50 values in some human cancer cell lines in vitro. Interim results of ONC212 sensitivity profiling in >100 genetically annotated cell lines from the Genomic of Drug Sensitivity in Cancer collection have corroborated this improvement in potency. One analogue, ONC212, has demonstrated compelling efficacy against several tumor types in vivo with no evidence of toxicity at therapeutic doses. Furthermore, in vitro mechanism studies have demonstrated overlap between ONC201- and ONC212-mediated signaling in tumor cells that includes activation of the integrated stress response. With a wide safety margin, distinct pharmacokinetics (PK), and robust potency, ONC212 is being developed as the next drug candidate from the new class of compounds defined by the novel pharmacophore of ONC201 in indications that complement the parent compound9s use spectrum. Citation Format: Jessica Wagner, Gary Olson, Nallaganchu Rao Bhaskara, Richard S. Pottorf, Garnett J. Mathew, Cyril H. Benes, Rohinton Tarapore, Martin Stogniew, Lee Schalop, Wolfgang Oster, Josh E. Allen, Wafik S. El-Deiry. Structure-activity relationships and mechanistic analysis of analogues of the clinical-stage anti-cancer small molecule ONC201. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 349.

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