Phase I and Pharmacology Study of Ropidoxuridine (IPdR) as Prodrug for Iododeoxyuridine-Mediated Tumor Radiosensitization in Advanced GI Cancer Undergoing Radiation.

PURPOSE: Iododeoxyuridine (IUdR) is a potent radiosensitizer; however, its clinical utility is limited by dose-limiting systemic toxicities and the need for prolonged continuous infusion. 5-Iodo-2-pyrimidinone-2'-deoxyribose (IPdR) is an oral prodrug of IUdR that, compared with IUdR, is easier to administer and less toxic, with a more favorable therapeutic index in preclinical studies. Here, we report the clinical and pharmacologic results of a first-in-human phase I dose escalation study of IPdR + concurrent radiation therapy (RT) in patients with advanced metastatic gastrointestinal (GI) cancers. PATIENTS AND METHODS: Adult patients with metastatic GI cancers referred for palliative RT to the chest, abdomen, or pelvis were eligible for study. Patients received IPdR orally once every day × 28 days beginning 7 days before the initiation of RT (37.5 Gy in 2.5 Gy × 15 fractions). A 2-part dose escalation scheme was used, pharmacokinetic studies were performed at multiple time points, and all patients were assessed for toxicity and response to Day 56. RESULTS: Nineteen patients were entered on study. Dose-limiting toxicity was encountered at 1,800 mg every day, and the recommended phase II dose is 1,200 mg every day. Pharmacokinetic analyses demonstrated achievable and sustainable levels of plasma IUdR ≥1 µmol/L (levels previously shown to mediate radiosensitization). Two complete, 3 partial, and 9 stable responses were achieved in target lesions. CONCLUSIONS: Administration of IPdR orally every day × 28 days with RT is feasible and tolerable at doses that produce plasma IUdR levels ≥1 µmol/L. These results support the investigation of IPdR + RT in phase II studies.

The National Cancer Institute ALMANAC: A Comprehensive Screening Resource for the Detection of Anticancer Drug Pairs with Enhanced Therapeutic Activity.

To date, over 100 small-molecule oncology drugs have been approved by the FDA. Because of the inherent heterogeneity of tumors, these small molecules are often administered in combination to prevent emergence of resistant cell subpopulations. Therefore, new combination strategies to overcome drug resistance in patients with advanced cancer are needed. In this study, we performed a systematic evaluation of the therapeutic activity of over 5,000 pairs of FDA-approved cancer drugs against a panel of 60 well-characterized human tumor cell lines (NCI-60) to uncover combinations with greater than additive growth-inhibitory activity. Screening results were compiled into a database, termed the NCI-ALMANAC (A Large Matrix of Anti-Neoplastic Agent Combinations), publicly available at https://dtp.cancer.gov/ncialmanac Subsequent in vivo experiments in mouse xenograft models of human cancer confirmed combinations with greater than single-agent efficacy. Concomitant detection of mechanistic biomarkers for these combinations in vivo supported the initiation of two phase I clinical trials at the NCI to evaluate clofarabine with bortezomib and nilotinib with paclitaxel in patients with advanced cancer. Consequently, the hypothesis-generating NCI-ALMANAC web-based resource has demonstrated value in identifying promising combinations of approved drugs with potent anticancer activity for further mechanistic study and translation to clinical trials. Cancer Res; 77(13); 3564-76. ©2017 AACR.

Pharmacogenetically driven patient selection for a first-in-human phase I trial of batracylin in patients with advanced solid tumors and lymphomas.

PURPOSE: Batracylin (daniquidone), an ATP-insensitive topoisomerase I/II inhibitor, demonstrated wide interspecies variation in preclinical models consistent with formation of a toxic metabolite, N-acetyl-batracylin, following metabolism by N-acetyl-transferase 2 (NAT2). To minimize exposure to this toxic metabolite, this first-in-human study was conducted in patients with advanced refractory solid tumors or lymphomas demonstrated to have a slow NAT2 acetylator genotype. The objectives were to determine the safety, maximum tolerated dose (MTD), and pharmacokinetics of batracylin and its metabolites. METHODS: Based on the MTD for rats, the most sensitive species, the starting dose was 5 mg/day for 7 days in 28-day cycles. Dose escalation followed accelerated titration design 4B, with restaging performed every 2 cycles. RESULTS: Thirty-one patients were enrolled. Treatment was well tolerated; one patient experienced grade 3 toxicity (lymphopenia). Dose escalation was stopped at 400 mg/day due to grade 1 and 2 hemorrhagic cystitis. No objective responses were observed, but prolonged disease stabilization was observed in 2 patients, one with peritoneal mesothelioma (8 cycles) and another with adrenocortical cancer (18 cycles). Across an 80-fold range of doses, the ratios of systemic exposures for batracylin and N-acetyl batracylin were near 1. CONCLUSIONS: Pharmacogenetically selected patients reached a dose that was 20-fold higher than the MTD in rats and 70 % of the MTD in mice. This genotype-guided strategy was successful in safely delivering batracylin to patients. However, due to unexpected cystitis, not preventable by hydration, and in the absence of a stronger signal for antitumor activity, further development of batracylin has been stopped.

Validation and application of a stability-indicating HPLC method for the in vitro determination of gastric and intestinal stability of venlafaxine.

Gastrointestinal stability of venlafaxine was evaluated in vitro in simulated gastric (SGF) and intestinal (SIF) fluids using a stability indicating HPLC method. The method was validated using a 5 microm Ascentis C18 column (150 mm x 4.6 mm) and mobile phase consisting of 30% acetonitrile in 20 mM potassium phosphate buffer (pH 6.5) delivered isocratically at a flow rate of 1 mL/min with UV detection at 228 nm. Venlafaxine in USP simulated gastric and intestinal fluids (0.4 mg/mL) was incubated at 37 degrees C in a shaking water bath. The gastric stability study samples were assayed at 0, 15, 30 and 60 min intervals while sampling for the intestinal stability study was at 0, 1, 2 and 3 h. System suitability determinations gave R.S.D.s of 0.68, 0.5 and 3.9% for retention factor (k'), peak area and tailing factor, respectively. The method was shown to be accurate, precise, specific, and linear over the analytical range. Intra- and inter-day precision was <5.3%. Forced degradation studies of drug substance in basic media at 70 degrees C as well as in H2O2 for 1 h and ultra-violet photostability studies at 255 and 365 nm for 24 h did not produce any detectable degradation products. Forced degradation studies of drug substance in acidic media at 70 degrees C for 1 h produced the dehydro-venlafaxine degradant. Venlafaxine was stable in SGF (pH approximately 1.2) for the 1-h incubation period and in SIF (pH 6.8) up to 3 h with <1.5% relative difference (RD) between the amount of drug added and that found for all time points. This stability experiment in simulated gastric and intestinal fluids suggests that drug loss in the gastrointestinal tract takes place by membrane permeation rather than a degradation process.

Metabolic profile of XK469 (2(R)-[4-(7-chloro-2-quinoxalinyl)oxyphenoxy]-propionic acid; NSC698215) in patients and in vitro: low potential for active or toxic metabolites or for drug-drug interactions.

As part of an ongoing phase 1 study, we studied the excretion of XK469 and its metabolism in patients and in vitro. Five primary metabolites were identified by HPLC/MS/MS. An oxidized product formed by cytosolic aldehyde oxidase was the predominant species both in urine and human hepatocytes in vitro. Conjugates of XK469 with glycine, taurine, and glucuronic acid, as well as the microsomal product, 4-oxo-XK469, were also found in urine and in vitro, but none were major contributors to the mass balance for XK469 elimination. Based upon the relative concentrations circulating in plasma, systemic exposure to parent drug was 100-fold higher than for the metabolites. Thus, both toxicity and efficacy of XK469 are most likely to be produced by the parent molecule, rather than the metabolites. Urinary recovery of parent drug was low (2% of dose in 24 h), partly because of the long half-life of XK469 (approximately 3 days). In addition, the metabolite profile in urine indicates that only 25% of the XK469-derived material was unchanged drug. Thus, urinary excretion was not a major factor in XK469 elimination. Variations in systemic exposure to XK469 will be strongly influenced by factors that alter the activity of aldehyde oxidase, including pharmacogenetics, enzyme inhibition, and enzyme induction, but no specific modifiers have been reported. The multiday half-life of XK469 hampered our ability to obtain a complete mass balance, and the possibility exists that other routes, such as biliary excretion, may also play a substantial role in XK469 disposition.

Distribution of 1-(2-deoxy-2-fluoro-beta-D-arabinofuranosyl) uracil in mice bearing colorectal cancer xenografts: rationale for therapeutic use and as a positron emission tomography probe for thymidylate synthase.

PURPOSE: In colorectal, breast, and head and neck cancers, response to 5-fluorouracil is associated with low expression of thymidylate synthase. In contrast, tumors with high expression of thymidylate synthase may be more sensitive to prodrugs such as 1-(2-deoxy-2-fluoro-beta-D-arabinofuranosyl) uracil (FAU) that are activated by thymidylate synthase. These studies were designed to evaluate FAU as a potential therapeutic and diagnostic probe. EXPERIMENTAL DESIGN: [18F]-FAU and [3H]-FAU were synthesized with >97% radiochemical purity. [3H]-FAU or [18F]-FAU was administered intravenously to severe combined immunodeficient mice bearing either HT29 (low thymidylate synthase) or LS174T (high thymidylate synthase) human colon cancer xenografts. Four hours after [3H]-FAU dosing, tissue distribution of total radioactivity and incorporation of 1-(2-deoxy-2-fluoro-beta-D-arabinofuranosyl) 5-methyluracil (FMAU), derived from thymidylate synthase activation of FAU, into tumor DNA was measured. Positron emission tomography (PET) images were obtained for 90 minutes after injection of [18F]-FAU. Thymidylate synthase activity was determined in vitro in tumors from untreated mice by [3H] release from [3H]dUMP. Each cell line was incubated in vitro with [3H]-FAU or [3H]-FMAU in the absence or presence of 5-fluoro-2'-deoxyuridine (FdUrd) and then was analyzed for incorporation of radiolabel into DNA. RESULTS: Thymidylate synthase enzymatic activity in LS174T xenografts was approximately 3.5-fold higher than in HT29 xenografts, and incorporation of radioactivity derived from [3H]-FAU into LS174T DNA was approximately 2-fold higher than into HT29 DNA. At 240 minutes, radioactivity derived from [3H]-FAU was approximately 2-fold higher in tumors than in skeletal muscle. At times up to 90 minutes, PET imaging detected only small differences in uptake of [18F]-FAU between the tumor types. Fluorine-18 in skeletal muscle was higher than in tumor for the first 90 minutes and plateaued earlier, whereas [18F] in tumor continued to increase during the 90-minute imaging period. For both cell lines in vitro, FdUrd decreased the rate of incorporation of [3H]-FAU into DNA, whereas the incorporation of [3H]-FMAU was increased. CONCLUSIONS: These results for FAU incorporation into DNA in vitro and in vivo further support clinical evaluation of FAU as a therapeutic agent in tumors with high concentrations of thymidylate synthase that are less likely to respond to 5-fluorouracil treatment. The high circulating concentrations of thymidine reported in mice may limit their utility in evaluating FAU as a PET probe.

Identification of genes regulating sensory neuron genesis and differentiation in the avian dorsal root ganglia.

The dorsal root ganglia (DRG) derive from a population of migrating neural crest cells that coalesce laterally to the neural tube. As the DRG matures, discrete cell types emerge from a pool of differentiating progenitor cells. To identify genes that regulate sensory genesis and differentiation, we have designed screens to identify members from families of known regulatory molecules such as receptor tyrosine kinases, and generated full-length and subtractive cDNA libraries between immature and mature DRG for identifying novel genes not previously implicated in DRG development. Several genes were identified in these analyses that belong to important regulatory gene families. Quantitative PCR confirmed differential expression of candidate cDNAs identified from the subtraction/differential screening. In situ hybridization further validated dynamic expression of several cDNAs identified in our screens. Our results demonstrate the utility of combining specific and general screening approaches for isolating key regulatory genes involved in the genesis and differentiation of discrete cell types and tissues within the classic embryonic chick model system.