Ribavirin depletes endogenous nucleotide pools

描述（由申请人提供）：利巴韦林是一种核苷类似物，是世界上仅有的广谱抗病毒药物之一，是治疗慢性丙型肝炎病毒（HCV）的基本成分。尽管临床使用了几十年，但利巴韦林抑制HCV复制并导致其主要剂量限制性毒性贫血的确切机制尚不清楚。我们缺乏对利巴韦林如何起作用和引起贫血的了解，这代表了我们对HCV治疗知识的根本空白。为了优化HCV治愈率并最大限度地减少基于利巴韦林的治疗引起的贫血，我们需要了解这种药物的药理学。在体外，利巴韦林消耗内源性嘌呤，这可能解释了其毒性和治疗作用，但这尚未在人体中进行研究。通过这项应用，Kiser博士将在她的K23上继续努力，并探索利巴韦林对内源性嘌呤的影响。本研究的具体目的是（1）比较ITPA活性表型组间接受利巴韦林治疗的HCV感染患者的红细胞和外周血单核细胞中内源性嘌呤浓度的变化，（2）确定内源性嘌呤耗竭与病毒学应答和贫血之间的相关性，以及ITPA活性表型对这些效应的调节程度。为了实现这些目标，我们将在Kiser博士的K23研究中的40名受试者和前瞻性入选的170名受试者的外周血单核细胞和红细胞中，测量开始基于利巴韦林的HCV治疗前和开始治疗后4周和12周的内源性嘌呤浓度以及开始治疗后4周和12周的三磷酸利巴韦林浓度（并按ITPA活性表型分层）通过我们的肝病诊所。本研究将 增加我们对利巴韦林如何抑制HCV复制和导致贫血的理解，并确定是否存在基于ITPA遗传学的效应差异。此外，虽然通过该授权开发的LC/MS/MS检测将立即用于解决本申请的目的，但该技术也可应用于研究用于治疗HIV、B型肝炎和癌症的HCV核苷聚合酶抑制剂和核苷（酸）类似物对内源性核苷酸库的影响。

DESCRIPTION (provided by applicant): Ribavirin, a nucleoside analog, is one of the only broad-spectrum antiviral drugs available in the world, and it is a fundamental component of treatment for chronic Hepatitis C virus (HCV). Despite decades of clinical use, the exact mechanisms by which ribavirin inhibits HCV replication and causes its major dose limiting toxicity, anemia are unclear. Our lack of understanding of how ribavirin works and causes anemia represent fundamental gaps in our knowledge of the treatment of HCV. To optimize HCV cure rates and minimize anemia from ribavirin-based treatment, we need to understand this drug's pharmacology. In vitro, ribavirin depletes endogenous purines which likely explains its toxic and therapeutic effects, but this has not been investigated in humans. Through this application, Dr. Kiser will extend efforts on her K23 and explore the effects of ribavirin on endogenous purines. The specific aims for the study are to (1) compare the change in endogenous purine concentrations in the red blood and peripheral blood mononuclear cells of HCV-infected patients on ribavirin-based treatment across ITPA activity phenotype groups and (2) to determine associations between endogenous purine depletion and virologic response and anemia and the degree to which ITPA activity phenotype moderates these effects. To address these aims, we will measure endogenous purine concentrations before starting ribavirin-based HCV treatment and 4- and 12-weeks after initiating treatment and ribavirin triphosphate concentrations 4- and 12-weeks after initiating treatment in the peripheral blood mononuclear and red blood cells of 40 subjects in Dr. Kiser's K23 study and 170 subjects prospectively enrolled (and stratified by ITPA activity phenotype) through our Hepatology clinic. This study will increase our understanding of how ribavirin inhibits HCV replication and causes anemia and determine if there are differences in effect based on ITPA genetics. Additionally, while the LC/MS/MS assay developed through this grant will be immediately used to address the aims of this application, the technology can also be applied to investigations of the effects of HCV nucleoside polymerase inhibitors and nucleos(t)ide analogs used in the treatment of HIV, Hepatitis B, and cancer on endogenous nucleotide pools.