Engineering bispecific antibodies for non-hormonal contraception

总结 精子必须游过粘液才能上升到上生殖道并使卵子受精。此外，精子 必须过度激活才能穿透卵母细胞的透明带。聚合抗体 (Ab)，例如 IgM 结合精子表面抗原的物质可以将精子凝集成太大而无法穿过毛孔的簇 的粘液。此外，IgG 还可以被设计为将单个精子与粘蛋白交联，并抑制 过度激活，从而阻止精子到达卵子并使卵子受精。主题被动 基于阴道递送抗精子抗体（ASA）的免疫接种在动物模型中得到了验证 80年代-90年代，直接克服了避孕强度可变、可逆性不确定的问题 疫苗。然而，由于单克隆抗体生产的高成本和挑战，这一策略并不实用 与 IgM 制剂。鉴于生物加工的显着进步大大降低了成本 单克隆抗体的制造，以及通过阴道内持续递送抗体的可能性 环，我们相信现在时机已经成熟，开发用于非激素避孕的新型、超强效 ASA 基于阴道针对人类精子的局部被动免疫。在试点研究中，我们已经表明 我们可以通过工程将 ASA 的精子凝集效力大大提高 >15-50 倍 多价、基于 IgG 的构建体由 6 至 10 个 Fab 结构域组成（即 4 至 8 个附加 Fab 与 亲本 IgG 分子）。这些新型构建体在加速热中具有与 IgG 相当的稳定性 稳定性研究，以及与 IgG 类似的生产和纯化产量。其中一个结构代表 波士顿大学避孕研究中心正在开发先导分子，有两个第一阶段 临床试验预计于 2020 年开始。在这个项目中，我们寻求通过采用 通过酵母和哺乳动物细胞展示的尖端双特异性抗体工程技术和亲和力成熟 设计超强双特异性多价 ASA 构建体库。我们将同时瞄准 CD52g， 特征和验证的抗原靶标仅存在于人类精子上，而 EPPIN 是一种成熟的 通过抑制精子过度活跃发挥作用的避孕目标。在目标 1 中，我们将利用酵母展示来 提高 Fab 对 CD52g 和 EPPIN 的亲和力，设计多价双特异性构建体库 结合两个目标，并严格表征这些分子。在目标 2 中，我们将执行一组 研究评估其潜在的避孕功效，包括精子凝集、捕获单个精子 粘液中，并抑制精子过度活跃。确定哪种构造将最有效地减少 为了提高人类阴道中的精子活力，我们将在目标 3 中与两个人一起进行体内剂量探索研究 在适应绵羊阴道的性交后生育力测试中，目标 1 和 2 中最有效的构建体。成功 完成这些研究可能会让我们能够推进一种新型 ASA 候选药物，其性能要大得多。 避孕效力高于目前正在开发的用于非激素避孕的 ASA 分子。

Summary Sperm must swim through mucus before ascending to the upper tract and fertilizing the egg. In addition, sperm must be hyperactivated to penetrate the zona pellucida of the oocyte. Polymeric antibodies (Ab) such as IgM that bind sperm surface antigens can agglutinate sperm into clusters too large to penetrate through the pores of mucus. In addition, IgG can also be engineered to crosslink individual sperm to mucins, as well as inhibit hyperactivation, consequently preventing sperm from reaching and fertilizing the egg. Topical passive immunization based on vaginal delivery of anti-sperm Ab (ASA) was validated in animal models in the 1980s-1990s, and directly overcomes the variable intensity and uncertain reversibility of contraceptive vaccines. However, this strategy was not practical due to the high costs of mAb production and challenges with IgM formulation. Given the remarkable advances in bioprocessing that have greatly reduced the costs of mAb manufacturing, and the possibility of sustained delivery of antibodies in the vagina via intravaginal rings, we believe the time is now ripe to develop novel, ultra-potent ASA for non-hormonal contraception based on topical passive immunization of the vagina against human sperm. In pilot studies, we have shown that we can greatly increase the sperm-agglutination potency of ASA by >15-50-fold by engineering multivalent, IgG-based construct comprised of six to ten Fab domains (i.e. 4 to 8 additional Fabs linked to the parent IgG molecule). These novel constructs possess comparable stability to IgG in accelerated thermal stability studies, and also similar production and purification yield as IgG. One of the constructs represent the lead molecule under development in the Boston University Contraceptive Research Center, with two Phase I clinical trials slated to begin in 2020. In this project, we seek to further improve the potencies by employing cutting edge bispecific Ab engineering technology and affinity maturation via yeast and mamallian cell display to engineer a library of ultra-potent bispecific multivalent ASA constructs. We will target both CD52g, a well characterized and validated antigen target present on human sperm only, and EPPIN, a well established contraceptive target that functions by inhibiting sperm hyperactivation. In Aim 1, we will utilize yeast display to improve the affinity of Fab against CD52g and EPPIN, engineer a library of multivalent bispecific constructs that bind both targets, and rigorously characterize these molecules. In Aim 2, we will perform a panel of studies to assess their potential contraceptive efficacy, including sperm agglutination, trapping individual sperm in mucus, and inhibition of sperm hyperactivation. To determine which construct will most effectively reduce progressive sperm motility in human vagina, we will perform in vivo dose finding studies in Aim 3 with the two most potent constructs from Aims 1 and 2 in a post-coital fertility test adapted to the sheep vagina. Successful completion of these studies will likely allow us to advance a novel ASA candidate with substantially greater contraceptive potency than the current ASA molecules under development for non-hormonal contraception.