Cell-cycle regulatory kinases as targets for male contraceptive drug development

描述(由申请人提供)：项目摘要一种可靠、安全、易用的可逆非荷尔蒙男性避孕药将为以下男性提供重要的选择 想要在计划生育中发挥积极作用。目前男性的主要选择是输精管结扎术和避孕套，但每一种都存在可逆性和手术风险或依从性方面的问题。目前，在可逆非激素性男性收缩的药物开发中，缺乏可用药的靶点。在精子发生过程中对细胞周期进程至关重要的蛋白激酶是可药物的，有望成为避孕开发的靶点。在这方面，细胞周期蛋白依赖性蛋白激酶2(CDK2)就是这样一个靶点。CDK2/-基因敲除小鼠可以存活，但不育。CDK2通过与细胞周期蛋白A和A1相互作用，靶向视网膜母细胞瘤蛋白(PRB)和P53的磷酸化。这两种蛋白都存在于人和小鼠的睾丸中，并在睾丸发育和生精细胞周期的过渡调节中发挥关键作用。因此，一种有效抑制CDK2的药物应该阻止精子发生，从而导致精子缺乏导致不育。由于CDK2是一种影响减数分裂的酶，一旦不再服用这种药物，减数分裂应该会恢复，精子产生也会恢复。这项研究的主要假设是，新型小分子特异性CDK2抑制剂可以开发为新型非激素可逆男性避孕药。为了证明这一假设，将实现以下特定目标：特定目标1.鉴定和排序已知的CDK2可逆性抑制大鼠生精发生的抑制剂。具体目的2.开发新型的CDK2变构和I型和II型激酶抑制剂，以提高CDK2的特异性，体内抗精子生成的效果，并将副作用降至最低。具体目的3.论证CDK2抑制剂的概念可逆避孕效果为了达到特定目的，我们将开展两条线的研究，开发新型CDK2抑制剂作为男性避孕药。首先，我们将提高我们最近开发的有效的纳摩尔I型和II型激酶抑制剂的CDK2特异性。这种具体构建的方法以前对我们很管用。其次，我们将通过我们最近发现的变构位点来开发新型的CDK2调节剂，因为这可能提供更多的机会来具有CDK2特异性的选择性，并最大限度地减少与激酶家族其他成员的交叉反应。为了成为一种成功和可行的男性避孕药，其有效性、安全性和生育力的恢复需要与口服女性避孕药相媲美。根据我们在正在进行的避孕开发项目中的经验和成功，其中一个项目目前正在FDA的指导下进行临床前开发，我们预计该项目将生产出具有很高前景的新型CDK2抑制剂，以实现安全、有效和易于使用的可逆男性避孕药的目标。

DESCRIPTION (provided by applicant): Project Abstract A reversible non-hormonal male contraceptive that is reliable, safe, and easy to use will provide a significant option for men who want to take an active role in family planning. The current primary choices for men are vasectomy and condoms, but each has problems with reversibility and surgical risk, or compliance, respective- ly. There is currently a paucity of druggable targets in drug development for reversible non-hormonal male con- traception. Protein kinases that are critical for cell cycle progression during spermatogenesis that are drugga- ble offer promise as targets for contraceptive development. In this regard, cyclin-dependent protein kinase 2 (CDK2) is such a target. CDK2-/- knockout mice are viable but sterile. CDK2 through its interaction with cyclins A and A1 targets retinoblastoma protein (pRB) and p53 for phosphorylation. Both of these proteins are present in human and murine testis, and play critical roles in testis development, and in regulation of transition through the spermatogenic cell cycle. Therefore, a drug that effectively inhibits CDK2 should block spermatogenesis, thereby causing infertility due to lack of sperm. Since CDK2 is an enzyme that effects meiotic division, once the drug is no longer taken, meiosis should resume and sperm production recovers. The primary hypothesis for this research is that novel small molecule specific inhibitors of CDK2 can be developed as novel non-hormonal reversible male contraceptive agents. To prove this hypothe- sis, the following specific aims will be achieved: Specific Aim 1. Identify and rank known inhibitors of CDK2 that reversibly inhibit spermatogenesis in rats. Specific Aim 2. Develop novel CDK2 allosteric and type I and II kinase inhibitors as leads to improve CDK2 specificity, in vivo anti-spermatogenic efficacy, and minimize side effects. Specific Aim 3. Demonstrate proof-of-concept reversible contraceptive efficacy of CDK2 inhibitors To achieve specific aims, we will undertake two lines of research to develop novel CDK2 inhibitors as male contraceptives. First, we will improve the CDK2 specificity for potent nanomolar type I and type II kinase inhibitors that we recently developed. This approach of building in specificity has worked for us before. Second, we will pursue the development of novel CDK2 modulators via an allosteric site that we recently discovered, as these may provide greater opportunities to have CDK2-specific selectivity and minimize cross reactivity with other members of the kinase family. In order to be a successful and viable male contraceptive agent, efficacy, safety, and recovery of fertility will need to be comparable to the oral female contraceptive pill. Based on our experience and success in ongoing contraceptive development projects, one of which is currently in pre-clinical development under FDA guidance, we expect this project to produce novel CDK2 inhibitors with high promise to meet the goal of a safe, effective, and easy to use reversible male contraceptive agent.