Department of Pharmacology and Pharmaceutical Sciences, School of Pharmacy , University of Southern California , Los Angeles , California 90089 , United States.
Department of Ophthalmology, USC Roski Eye Institute, Keck School of Medicine , University of Southern California , Los Angeles , California 90089 , United States.
Mol Pharm. 2019 Jul 1;16(7):3024-3039. doi: 10.1021/acs.molpharmaceut.9b00263. Epub 2019 May 30.
The USFDA-approved immunosuppressive drug rapamycin (Rapa), despite its potency, is limited by poor bioavailability and a narrow therapeutic index. In this study, we sought to improve bioavailability of Rapa with subcutaneous (SC) administration and to test its therapeutic feasibility and practicality in a murine model of Sjögren's syndrome (SS), a systemic autoimmune disease with no approved therapies. To improve its therapeutic index, we formulated Rapa with a carrier termed FAF, a fusion of the human cytosolic FK506-binding protein 12 (FKBP12) and an elastin-like polypeptide (ELP). The resulting 97 kDa FAF (i) has minimal burst release, (ii) is "humanized", (iii) is biodegradable, (iv) solubilizes two Rapa per FAF, and (v) avoids organic solvents or amphiphilic carriers. Demonstrating high stability, FAF remained soluble and monodisperse with a hydrodynamic radius of 8 nm at physiological temperature. A complete pharmacokinetic (PK) analysis of FAF revealed that the bioavailability of SC FAF was 60%, with significantly higher blood concentration during the elimination phase compared to IV FAF. The plasma concentration of Rapa delivered by FAF was 8-fold higher with a significantly increased plasma-to-whole blood ratio relative to free Rapa, 24 h after injection. To evaluate therapeutic effects, FAF-Rapa was administered SC every other day for 2 weeks to male non-obese diabetic (NOD) mice, which develop an SS-like autoimmune-mediated lacrimal gland (LG) inflammation and other characteristic features of SS. Both FAF-Rapa and free Rapa exhibited immunomodulatory effects by significantly suppressing lymphocytic infiltration, gene expression of IFN-γ, MHC II, type I collagen and IL-12a, and cathepsin S (CTSS) activity in LG compared to controls. Serum chemistry and histopathological analyses in major organs revealed no apparent toxicity of FAF-Rapa. Given its improved PK and equipotent therapeutic efficacy compared to free Rapa, FAF-Rapa is of further interest for systemic treatments for autoimmune diseases like SS.
美国食品和药物管理局批准的免疫抑制药物雷帕霉素（Rapa），尽管其效力强大，但由于生物利用度差和治疗指数狭窄而受到限制。在这项研究中，我们试图通过皮下（SC）给药来提高 Rapa 的生物利用度，并在干燥综合征（SS）的小鼠模型中测试其治疗的可行性和实用性，SS 是一种没有批准治疗方法的系统性自身免疫性疾病。为了提高其治疗指数，我们用一种称为 FAF 的载体来配方化 Rapa，FAF 是人类胞质 FK506 结合蛋白 12（FKBP12）和弹性蛋白样多肽（ELP）的融合物。所得的 97 kDa FAF（i）具有最小的爆发释放，（ii）是“人源化的”，（iii）是可生物降解的，（iv）每 FAF 可溶解两个 Rapa，（v）避免使用有机溶剂或两亲载体。FAF 表现出很高的稳定性，在生理温度下保持可溶性和单分散性，流体力学半径为 8nm。FAF 的完整药代动力学（PK）分析表明，SC FAF 的生物利用度为 60%，与 IV FAF 相比，消除阶段的血液浓度明显更高。FAF 输送的 Rapa 血浆浓度是游离 Rapa 的 8 倍，注射后 24 小时，血浆与全血的比值明显增加。为了评估治疗效果，FAF-Rapa 每隔一天皮下给药 2 周，用于非肥胖型糖尿病（NOD）雄性小鼠，这些小鼠会发展出类似于干燥综合征的自身免疫性介导的泪腺（LG）炎症和干燥综合征的其他特征。与对照组相比，FAF-Rapa 和游离 Rapa 均通过显著抑制淋巴细胞浸润、IFN-γ、MHC II、I 型胶原和 IL-12a 以及组织蛋白酶 S（CTSS）的基因表达，对 LG 产生免疫调节作用。血清化学和主要器官的组织病理学分析表明，FAF-Rapa 没有明显的毒性。鉴于其与游离 Rapa 相比具有改善的 PK 和等效的治疗功效，FAF-Rapa 对于干燥综合征等自身免疫性疾病的系统治疗具有进一步的研究意义。
