Low-dose IL-2-based Immunomodulatory Therapy for PAH

 描述(由申请人提供)：尽管有证据表明炎症机制在肺动脉高压(PAH)中启动并使病理生理学复杂化，但还没有开发出针对所涉及的炎症细胞的策略。此外，众所周知，自身免疫性疾病与某些形式的PAH有关。因此，迫切需要新的治疗方法来减轻慢性炎症，恢复免疫平衡，逆转不利的血管重构，以实现肺和右室功能的持续改善。自然产生的胸腺来源的CD4+CD25+Foxp3+调节性T细胞(NTreg)在控制过度的炎症反应和预防自身免疫性疾病方面发挥着至关重要的作用。白介素2(IL-2)是nTreg产生、存活和功能的关键细胞因子，通过与其高亲和力受体直接结合， IL 2Rα(CD2 5)、IL 2Rβ(CD12 2)和ɣc(CD132)。最近的临床试验表明，在接受异基因造血干细胞移植的患者中，小剂量IL2的治疗增加了nTreg细胞的数量，并与糖皮质激素难治性慢性移植物抗宿主病的逆转有关。我们设计了一种在哺乳动物细胞中产生的人血清白蛋白(HSA)和IL-2的融合蛋白APT602。非糖化融合蛋白(85kD)将溶解度和体外效价提高了5倍，血浆半衰期延长了25倍(5小时)。引入单一突变以消除与内皮细胞的相互作用，降低血管渗漏综合征的风险。因此，低剂量的APT602将能够安全、选择性和方便地刺激与IL2Rαβɣ受体具有高亲和力的nTreg细胞，同时将与IL2Rβɣ受体具有中等亲和力的效应性免疫细胞的激活降至最低。在SU5416/低氧诱导的以全身炎症和氧化应激为特征的、类似于人类PAH病理生理的严重的、不可逆转的PAH大鼠模型中，APT602每周两次治疗3周，有效地恢复了免疫平衡，减轻了导致肺和RV功能逆转的纤维化。相比之下，波生坦(FDA批准的一线血管扩张疗法)和格列卫(在第三阶段试验中有效但有毒)都不安全或有效。在第一阶段的SBIR补助金申请中，我们将确定APT602的短暂治疗是否会实现肺和RV功能的长期改善。明确目标。确定APT602每周两次，连续3周，在PAH诱导后21天开始治疗，是否能安全逆转SU5416/低氧诱导的重度PAH大鼠模型治疗12周后的肺和RV重构和功能。

 DESCRIPTION (provided by applicant): Despite evidence that inflammatory mechanisms initiate and complicate pathophysiology in pulmonary arterial hypertension (PAH), no strategies have been developed to target the inflammatory cells involved. Moreover, it has been known for years that autoimmune diseases are associated with certain forms of PAH. Hence, novel therapy is urgently needed to attenuate chronic inflammation, restore immune homeostasis and reverse adverse vascular remodeling in order to achieve a persistent improvement of pulmonary and right ventricular functions. Naturally occurring thymus-derived CD4+CD25+Foxp3+ regulatory T cells (nTreg) play vital roles in controlling excessive inflammatory responses and prevent autoimmune disease. Interleukin-2 (IL-2) is the key cytokine for the generation, survival, and function of nTreg by direct binding to its high affinity receptor consisting of three subunits, IL2Rα (CD25), IL2Rβ (CD122) and ɣc (CD132). Recent clinical trial shows that treatment with low-dose IL2 increased nTreg cells population and was associated with reversal of glucocorticoid-refractory chronic graft-versus host disease in patients who had undergone allogeneic hematopoietic stem cell transplantation. We have designed APT602, a fusion protein of human serum albumin (HSA) and IL-2 produced in mammalian cells. The unglycosylated fusion protein (85kD) improves solubility and the in vitro potency by 5 fold and extends plasma half-life by 25 fold (5h). A single mutation was introduced to eliminate the interaction with endothelial cell and lower the risk of vascular leak syndrome. Hence, low-dose APT602 will enable safe, selective, and convenient stimulation of nTreg cells with high-affinity to IL2Rαβɣ receptors while minimizing activation of effector immune cells with intermediate affinity IL2Rβɣ receptors. In the severe and "irreversible" PAH model induced by SU5416/hypoxia in rats, which resembles human PAH pathophysiology, characterized by systemic inflammation and oxidative stress, treatment with APT602 twice a week for 3 weeks effectively restored immune homeostasis and attenuated fibrosis which lead to reversal of lung and RV function. In contrast, neither bosentan (FDA-approved first line vasodilative therapy) nor Gleevec (effective but toxic in Phase III trial) were safe or effective. In this Phase I SBIR grant application, we will determie whether transient treatment with APT602 will achieve long-term improvement of pulmonary and RV function. Specific Aim. Determine whether treatment of APT602 twice a week for 3 weeks, initiated 21 days after PAH induction, will safely reverse pulmonary and RV remodeling and function 12 weeks of follow up post the treatment in the rat model of SU5416/hypoxia-induced severe PAH.