Browsing by Author "Masters, Andi"

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    Erythrocytic Metabolism of ATLX-0199: An Agent that Increases Minute Ventilation
    (Elsevier, 2023) Krasinkiewicz, Jonathan M.; Hubbard, Dallin; de Guzman, Nicholas Perez; Masters, Andi; Zhao, Yi; Gaston, Herbert; Gaston, Benjamin; Pediatrics, School of Medicine
    Both L- and D-isomers of S-nitrosocysteine (CSNO) can bind to the intracellular domain of voltage-gated potassium channels in vitro. CSNO binding inhibits these channels in the carotid body, leading to increased minute ventilation in vivo. However, only the l-isomer is active in vivo because it requires the l-amino acid transporter (LAT) for transmembrane transport. In rodents and dogs, the esterified D-CSNO precursor-d-cystine dimethyl ester (ATLX-0199)-overcomes opioid- and benzodiazepine-induced respiratory depression while maintaining analgesia. Although ATLX-0199 can enter cells independently of LAT because it is an ester, its stability in plasma is limited by the presence of esterases. Here, we hypothesized that the drug could be sequestered in erythrocytes to avoid de-esterification in circulation. We developed a liquid chromatography-mass spectrometry method for detecting ATLX-0199 and characterized a new metabolite, S-nitroso-d-cysteine monomethyl ester (DNOCE), which is also a D-CSNO precursor. We found that both ATLX-0199 and DNOCE readily enter erythrocytes and neurons and remain stable over 20 min; thus ATLX-0199 can enter cells where the ester is stable, but the thiol is reduced. Depending on hemoglobin conformation, the reduced ester can be S-nitrosylated and enter carotid body neurons, where it then increases minute ventilation. These data may help explain the paradox that ATLX-0199, a dimethyl ester, can avoid de-esterification in plasma and exert its effects at the level of the carotid body.
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    In Vivo Targeting Replication Protein A for Cancer Therapy
    (Frontiers Media, 2022-02-18) VanderVere-Carozza, Pamela S.; Gavande, Navnath S.; Jalal, Shadia I.; Pollok, Karen E.; Ekinci, Elmira; Heyza, Joshua; Patrick, Steve M.; Masters, Andi; Turchi, John J.; Pawelczak, Katherine S.; Medicine, School of Medicine
    Replication protein A (RPA) plays essential roles in DNA replication, repair, recombination, and the DNA damage response (DDR). Retrospective analysis of lung cancer patient data demonstrates high RPA expression as a negative prognostic biomarker for overall survival in smoking-related lung cancers. Similarly, relative expression of RPA is a predictive marker for response to chemotherapy. These observations are consistent with the increase in RPA expression serving as an adaptive mechanism that allows tolerance of the genotoxic stress resulting from carcinogen exposure. We have developed second-generation RPA inhibitors (RPAis) that block the RPA-DNA interaction and optimized formulation for in vivo analyses. Data demonstrate that unlike first-generation RPAis, second-generation molecules show increased cellular permeability and induce cell death via apoptosis. Second-generation RPAis elicit single-agent in vitro anticancer activity across a broad spectrum of cancers, and the cellular response suggests existence of a threshold before chemical RPA exhaustion induces cell death. Chemical RPA inhibition potentiates the anticancer activity of a series of DDR inhibitors and traditional DNA-damaging cancer therapeutics. Consistent with chemical RPA exhaustion, we demonstrate that the effects of RPAi on replication fork dynamics are similar to other known DDR inhibitors. An optimized formulation of RPAi NERx 329 was developed that resulted in single-agent anticancer activity in two non-small cell lung cancer models. These data demonstrate a unique mechanism of action of RPAis eliciting a state of chemical RPA exhaustion and suggest they will provide an effective therapeutic option for difficult-to-treat lung cancers.
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    New Ref-1/APE1 targeted inhibitors demonstrating improved potency for clinical applications in multiple cancer types
    (Elsevier, 2024) Gampala, Silpa; Moon, Hye-ran; Wireman, Randall; Peil, Jacqueline; Kiran, Sonia; Mitchell, Dana K.; Brewster, Kylee; Mang, Henry; Masters, Andi; Bach, Christine; Smith-Kinnamen, Whitney; Doud, Emma H.; Rai, Ratan; Mosley, Amber L.; Quinney, Sara K.; Clapp, D. Wade; Hamdouchi, Chafiq; Wikel, James; Zhang, Chi; Han, Bumsoo; Georgiadis, Millie M.; Kelley, Mark R.; Fishel, Melissa L.; Pediatrics, School of Medicine
    AP endonuclease-1/Redox factor-1 (APE1/Ref-1 or Ref-1) is a multifunctional protein that is overexpressed in most aggressive cancers and impacts various cancer cell signaling pathways. Ref-1's redox activity plays a significant role in activating transcription factors (TFs) such as NFκB, HIF1α, STAT3 and AP-1, which are crucial contributors to the development of tumors and metastatic growth. Therefore, development of potent, selective inhibitors to target Ref-1 redox function is an appealing approach for therapeutic intervention. A first-generation compound, APX3330 successfully completed phase I clinical trial in adults with progressing solid tumors with favorable response rate, pharmacokinetics (PK), and minimal toxicity. These positive results prompted us to develop more potent analogs of APX3330 to effectively target Ref-1 in solid tumors. In this study, we present structure-activity relationship (SAR) identification and validation of lead compounds that exhibit a greater potency and a similar or better safety profile to APX3330. In order to triage and characterize the most potent and on-target second-generation Ref-1 redox inhibitors, we assayed for PK, mouse and human S9 fraction metabolic stability, in silico ADMET properties, ligand-based WaterLOGSY NMR measurements, pharmacodynamic markers, cell viability in multiple cancer cell types, and two distinct 3-dimensional (3D) cell killing assays (Tumor-Microenvironment on a Chip and 3D spheroid). To characterize the effects of Ref-1 inhibition in vivo, global proteomics was used following treatment with the top four analogs. This study identified and characterized more potent inhibitors of Ref-1 redox function (that outperformed APX3330 by 5-10-fold) with PK studies demonstrating efficacious doses for translation to clinic.
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    Pharmacokinetics and Biodistribution of 16,16 dimethyl Prostaglandin E2 in Non-Irradiated and Irradiated Mice and Non-Irradiated Non-Human Primates
    (BioOne, 2024) Langevin, Brooke; Singh, Pratibha; Plett, P. Artur; Sampson, Carol H.; Masters, Andi; Gibbs, Allison; De Faria, Eduardo; Triesler, Sarah; Zodda, Andrew; Jackson, Isabel L.; Orschell, Christie M.; Gopalakrishnan, Mathangi; Pelus, Louis M.; Medicine, School of Medicine
    Exposure to high-dose ionizing radiation can lead to life-threatening injuries and mortality. Bone marrow is the most sensitive organ to radiation damage, resulting in the hematopoietic acute radiation syndrome (H-ARS) with the potential sequelae of infection, hemorrhage, anemia, and death if untreated. The development of medical countermeasures (MCMs) to protect or mitigate radiation injury is a medical necessity. In our well-established murine model of H-ARS we have demonstrated that the prostaglandin E2 (PGE2) analog 16,16 dimethyl-PGE2 (dmPGE2) has survival efficacy as both a radioprotectant and radiomitigator. The purpose of this study was to investigate the pharmacokinetics (PK) and biodistribution of dmPGE2 when used as a radioprotector in irradiated and non-irradiated inbred C57BL/6J mice, PK in irradiated and non-irradiated Jackson Diversity Outbred (JDO) mice, and the PK profile of dmPGE2 in non-irradiated non-human primates (NHPs). The C57BL/6J and JDO mice each received a single subcutaneous (SC) dose of 35 ug of dmPGE2 and were randomized to either receive radiation 30 min later or remain non-irradiated. Plasma and tissue PK profiles were established. The NHP were dosed with 0.1 mg/kg by SC administration and the PK profile in plasma was established. The concentration time profiles were analyzed by standard non-compartmental analysis and the metrics of AUC0-Inf, AUC60-480 (AUC from 60-480 min), Cmax, and t1/2 were evaluated. AUC60-480 represents the postirradiation time frame and was used to assess radiation effect. Overall, AUC0-Inf, Cmax, and t1/2 were numerically similar between strains (C57BL/6J and JDO) when combined, regardless of exposure status (AUC0-Inf: 112.50 ng·h/ml and 114.48 ng·h/ml, Cmax: 44.53 ng/ml and 63.96 ng/ml; t1/2: 1.8 h and 1.1 h, respectively). PK metrics were numerically lower in irradiated C57BL/6J mice than in non-irradiated mice [irradiation ratio: irradiated values/non-irradiated values = 0.71 for AUC60-480 (i.e., 29% lower), and 0.6 for t1/2]. In JDO mice, the radiation ratio was 0.53 for AUC60-480 (i.e., 47% lower), and 1.7 h for t1/2. The AUC0-Inf, Cmax, and t1/2 of the NHPs were 29.20 ng·h/ml, 7.68 ng/ml, and 3.26 h, respectively. Despite the numerical differences seen between irradiated and non-irradiated groups in PK parameters, the effect of radiation on PK can be considered minimal based on current data. The biodistribution in C57BL/6J mice showed that dmPGE2 per gram of tissue was highest in the lungs, regardless of exposure status. The radiation ratio for the different tissue AUC60-480 in C57BL/6J mice ranged between 0.5-1.1 (50% lower to 10% higher). Spleen, liver and bone marrow showed close to twice lower exposures after irradiation, whereas heart had a 10% higher exposure. Based on the clearance values from mice and NHP, the estimated allometric scaling coefficient was 0.81 (95% CI: 0.75, 0.86). While slightly higher than the current literature estimates of 0.75, this scaling coefficient can be considered a reasonable estimate and can be used to scale dmPGE2 dosing from animals to humans for future trials.