th-302 and Neoplasms

Hypoxia, a state of low oxygen, is a common feature of solid tumors and is associated with disease progression as well as resistance to radiotherapy and certain chemotherapeutic drugs. Hypoxic regions in tumors, therefore, represent attractive targets for cancer therapy. To date, five distinct classes of bioreactive prodrugs have been developed to target hypoxic cells in solid tumors. These hypoxia-activated prodrugs, including nitro compounds, N-oxides, quinones, and metal complexes, generally share a common mechanism of activation whereby they are reduced by intracellular oxidoreductases in an oxygen-sensitive manner to form cytotoxins. Several examples including PR-104, TH-302, and EO9 are currently undergoing phase II and phase III clinical evaluation. In this review, we discuss the nature of tumor hypoxia as a therapeutic target, focusing on the development of bioreductive prodrugs. We also describe the current knowledge of how each prodrug class is activated and detail the clinical progress of leading examples.

Topics: Anthraquinones; Antineoplastic Agents; Aziridines; Cell Hypoxia; Humans; Indolequinones; Molecular Structure; NAD(P)H Dehydrogenase (Quinone); Neoplasms; Nitrogen Mustard Compounds; Nitroimidazoles; Phosphoramide Mustards; Prodrugs; Tirapazamine; Triazines

The objectives of this phase 1, first-in-human study were to determine the dose-limiting toxicities (DLT), maximum tolerated dose (MTD), safety, pharmacokinetics, and preliminary activity of the hypoxia-activated prodrug TH-302 in patients with advanced solid tumors.. TH-302 was administered intravenously over 30 to 60 minutes in two regimens: three times weekly dosing followed by 1 week off (arm A) and every 3-week dosing (arm B).. Fifty-seven patients enrolled (arm A: N = 37 and arm B: N = 20). The TH-302 dose was escalated from 7.5 to 670 mg/m(2) in arm A and from 670 to 940 mg/m(2) in arm B. The most common adverse events were nausea, skin rash, fatigue, and vomiting. Hematologic toxicity was mild and limited. Grade 3 skin and mucosal toxicities were dose limiting at 670 mg/m(2) in arm A; the MTD was 575 mg/m(2). In arm B, grade 3 fatigue and grade 3 vaginitis/proctitis were dose limiting at 940 mg/m(2); the MTD was 670 mg/m(2). Plasma concentrations of TH-302 and the active metabolite Br-IPM (brominated version of isophosphoramide mustard) increased proportionally with dose. Two partial responses were noted in patients with metastatic small cell lung cancer (SCLC) and melanoma in arm A at 480 and 670 mg/m(2). Stable disease was observed in arms A and B in 18 and 9 patients, respectively.. The MTD of TH-302 was 575 mg/m(2) weekly and 670 mg/m(2) every 3 weeks. Skin and mucosal toxicities were DLTs. On the basis of responses in metastatic melanoma and SCLC, further investigations in these indications were initiated.

Topics: Adult; Aged; Antineoplastic Agents; Cell Hypoxia; Disease Progression; Dose-Response Relationship, Drug; Female; Humans; Male; Maximum Tolerated Dose; Middle Aged; Models, Biological; Neoplasms; Nitroimidazoles; Phosphoramide Mustards; Prodrugs

Hypoxia is a common characteristic of many tumor microenvironments, and it has been shown to promote suppression of antitumor immunity. Despite strong biological rationale, longitudinal correlation of hypoxia and response to immunotherapy has not been investigated.. In this study, we probed the tumor and its surrounding microenvironment with. The results generated from this work provide an immediately translatable paradigm for measuring and targeting hypoxia to increase response to immune checkpoint therapy and using hypoxia imaging to guide combinatory therapies.

Topics: Cell Hypoxia; CTLA-4 Antigen; Humans; Hypoxia; Misonidazole; Neoplasms; Nitroimidazoles; Phosphoramide Mustards; Positron-Emission Tomography; Programmed Cell Death 1 Receptor; Tumor Microenvironment

Evofosfamide (TH-302) is a hypoxia-activated DNA-crosslinking prodrug currently in clinical development for cancer therapy. Oxygen-sensitive activation of evofosfamide depends on one-electron reduction, yet the reductases that catalyze this process in tumors are unknown. We used RNA sequencing, whole-genome CRISPR knockout, and reductase-focused short hairpin RNA screens to interrogate modifiers of evofosfamide activation in cancer cell lines. Involvement of mitochondrial electron transport in the activation of evofosfamide and the related nitroaromatic compounds EF5 and FSL-61 was investigated using 143B

Topics: Cell Line, Tumor; Cell Proliferation; Cell Survival; CRISPR-Cas Systems; Electron Transport; Gene Expression Regulation; Gene Regulatory Networks; HCT116 Cells; Humans; Mitochondria; Neoplasms; Nitroimidazoles; Phosphoramide Mustards; Prodrugs; RNA, Small Interfering; Sequence Analysis, RNA

TH-302 is a 2-nitroimidazole triggered hypoxia-activated prodrug (HAP) of bromo-isophosphoramide mustard currently undergoing clinical evaluation. Here, we describe broad-spectrum activity, hypoxia-selective activation, and mechanism of action of TH-302. The concentration and time dependence of TH-302 activation was examined as a function of oxygen concentration, with reference to the prototypic HAP tirapazamine, and showed superior oxygen inhibition of cytotoxicity and much improved dose potency relative to tirapazamine. Enhanced TH-302 cytotoxicity under hypoxia was observed across 32 human cancer cell lines. One-electron reductive enzyme dependence was confirmed using cells overexpressing human NADPH:cytochrome P450 oxidoreductase and radiolytic reduction established the single-electron stoichiometry of TH-302 fragmentation (activation). Examining downstream effects of TH-302 activity, we observed hypoxia-dependent induction of γH2AX phosphorylation, DNA cross-linking, and cell-cycle arrest. We used Chinese hamster ovary cell-based DNA repair mutant cell lines and established that lines deficient in homology-dependent repair, but not lines deficient in base excision, nucleotide excision, or nonhomologous end-joining repair, exhibited marked sensitivity to TH-302 under hypoxia. Consistent with this finding, enhanced sensitivity to TH-302 was also observed in lines deficient in BRCA1, BRCA2, and FANCA. Finally, we characterized TH-302 activity in the three-dimensional tumor spheroid and multicellular layer models. TH-302 showed much enhanced potency in H460 spheroids compared with H460 monolayer cells under normoxia. Multicellular layers composed of mixtures of parental HCT116 cells and HCT116 cells engineered to express an oxygen-insensitive bacterial nitroreductase showed that TH-302 exhibits a significant bystander effect.

Topics: Animals; Cell Hypoxia; Cell Line, Tumor; Cell Survival; CHO Cells; Comet Assay; Cricetinae; Cricetulus; DNA Damage; Dose-Response Relationship, Drug; HCT116 Cells; Histones; HT29 Cells; Humans; Inhibitory Concentration 50; Molecular Structure; Neoplasms; Nitroimidazoles; Oxidation-Reduction; Oxygen; Phosphoramide Mustards; Phosphorylation; Prodrugs; Spheroids, Cellular; Tumor Stem Cell Assay

Topics: Cell Hypoxia; Clinical Trials as Topic; Humans; Neoplasms; Nitroimidazoles; Phosphoramide Mustards