Design and Development of Immunotolerant S. aureus Biotherapies

金黄色葡萄球菌和其他细菌中多重耐药的发生率不断上升 一场公共卫生危机。三分之二的医院相关金黄色葡萄球菌感染和约50%的获得者是在 社区现在对甲氧西林耐药(MRSA)。耐甲氧西林金黄色葡萄球菌每年在美国造成45万人感染， 在美国所有由耐药细菌造成的死亡中，有一半是由它造成的。这种对公共健康的威胁是 创造了对新治疗剂的需求，但传统的抗生素开发管道并不能保持 与不断升级的问题保持同步。此外，抗菌化疗已被证明对 细菌耐药性的快速演变。溶菌酶，如模拟葡萄球菌溶葡萄球菌酶， 是一种创新的新型抗生素，可以催化分解细胞壁肽聚糖，导致细菌 解体和死亡。由于肽聚糖的保守性和复杂的生物合成，此类酶具有 事实证明，它不太容易受到紧急阻力的影响。不幸的是，溶葡萄球菌酶在体内会引起抗药抗体， 而这种免疫原性和相关的毒性是临床翻译的障碍。 在第一阶段成功拨款的支持下，隐形生物公司重新设计了溶葡萄球菌酶，用于 降低了人类的免疫原性。一期工程的关键成果是：1)设计和 溶葡萄球菌酶全球灭活变异体F12的构建；2)F12‘S抗MRSA的体外验证 效力；3)初步量化F12与FDA批准的抗生素的协同作用；4)论证 人体细胞免疫分析中免疫原性降低；以及5)体内免疫原性降低的确认 人源化的人类白细胞抗原转基因小鼠的免疫原性和随后增强的治疗效果。 总而言之，这些数据表明，F12是一种有希望的治疗耐药金黄色葡萄球菌感染的药物。 在拟议的第二期沙田公路，我们设计了一套有系统和有重点的策略，以建造一个 F12目标产品简介(TPP)。在目标1中，F12的制造和提纯将进行优化和放大。 在目标2中，将根据F12的S在体内的疗效来选择初步的临床适应症 模型：兔菌血症/心内膜炎和小鼠皮肤感染。疗效研究将得到严谨的支持 体外效力、体外耐药敏感性、体内最大耐受量、 体内药代动力学研究。AIM 3将产生对兔的初步毒性和免疫原性 接受单次或多次F12剂量递增的人源化小鼠。生成的数据包 将能够构建一个TPP，该TPP将指导全面的IND支持研究的设计和执行。 我们预计，基于F12的抗菌疗法将被证明是有效的、安全的、可重复使用的 给药。因此，F12将受益于相对于更具免疫原性的噬菌体内毒素的竞争优势， 最终，它可能代表着治疗危及生命的MRSA感染的一种突破性药物。

The increasing incidence of multi-drug resistance in Staphylococcus aureus and other bacteria represents a public health crisis. Two thirds of hospital-associated S. aureus infections and ~50% of those acquired in the community are now methicillin-resistant (MRSA). MRSA causes >450,000 infections in the US each year, and it is responsible for half of all US deaths caused by drug-resistant bacteria. This threat to public health is creating demand for new therapeutic agents, but traditional antibiotic development pipelines are not keeping pace with the escalating problem. Moreover, antibacterial chemotherapies have proven widely susceptible to rapid evolution of bacterial resistance. Bacteriolytic enzymes, such as Staphylococcus simulans lysostaphin, are an innovative new class of antibiotics that catalytically dismantle cell wall peptidoglycan causing bacterial lysis and death. Due to peptidoglycan’s conserved nature and complex biosynthesis, such enzymes have proven less susceptible to emergent resistance. Unfortunately, lysostaphin elicits anti-drug antibodies in vivo, and this immunogenicity and associated toxicity are barriers to clinical translation. Supported by a successful Phase I STTR grant, Stealth Biologics has re-engineered lysostaphin for reduced immunogenicity in humans. The pivotal outcomes of the Phase I STTR project were: 1) design and construction of F12, a globally deimmunized variant of lysostaphin; 2) in vitro validation of F12’s anti-MRSA potency; 3) preliminary quantification of F12 synergy with FDA approved antibiotics; 4) demonstration of reduced immunogenicity in human cellular immunoassays; and 5) confirmation of reduced in vivo immunogenicity and consequent enhanced therapeutic efficacy in humanized HLA transgenic mice. Collectively, these data suggest that F12 is a promising therapeutic for drug-resistant S. aureus infections. In the proposed Phase II STTR, we have designed a systematic and focused strategy for constructing an F12 target product profile (TPP). In Aim 1, F12 manufacturing and purification will be optimized and scaled up. In Aim 2, an initial clinical indication will be selected based on F12’s in vivo efficacy in two well-established models: rabbit bacteremia/endocarditis and murine skin infection. Efficacy studies will be supported by rigorous experimental analyses of in vitro potency, in vitro resistance susceptibility, in vivo maximum tolerated dose, and in vivo pharmacokinetics. Aim 3 will yield a preliminary toxicity and immunogenicity profile in rabbits and humanized mice that have received escalating single or repeated doses of F12. The resulting data package will enable construction of a TPP that will guide design and execution of comprehensive IND-enabling studies. We anticipate that F12-based antibacterial therapies will prove to be potent, safe, and amenable to repeated dosing. As such, F12 will benefit from competitive advantages relative to more immunogenic phage endolysins, and ultimately it may represent a breakthrough drug for life-threatening MRSA infections.