Mordenti J, Cuthbertson R A, Ferrara N, Thomsen K, Berleau L, Licko V, Allen P C, Valverde C R, Meng Y G, Fei D T, Fourre K M, Ryan A M
Department of Experimental Therapeutics, Genentech, Inc., Souty San Francisco, California 94080, USA.
Toxicol Pathol. 1999 Sep-Oct;27(5):536-44. doi: 10.1177/019262339902700507.
Access of recombinant proteins to the retina following intravitreal administration is poorly understood. A study was conducted in male Rhesus monkeys (15 to 28 mo of age; 2.8-3.3 kg) in order to compare the intraocular tissue distribution, pharmacokinetics, and safety of 125Iodine (I)-labeled full-length humanized rhuMAb HER2 antibody (148 kD) and of 125I-labeled humanized rhuMAb vascular endothelial growth factor Fab antibody (48.3 kD) following bilateral bolus intravitreal injection on day 0 (5 animals/group). The dose administered to each eye was 25 microg (9-10 microCi) in 50 microl. Animals were euthanatized on day 0 (1 hr postdose) and on days 1, 4, 7, and 14. Safety assessment included direct ophthalmoscopy, intraocular pressure measurements, clinical observations, body weight, and hematology and clinical chemistry panels. Blood and vitreous samples were collected daily (blood only) and at necropsy for pharmacokinetics and analysis for antibodies to the test materials; the ocular tissue distribution of the test material was evaluated by microautoradiography. All animals completed the study. Microautoradiography demonstrated that the full-length antibody did not penetrate the inner limiting membrane of the retina at any of the time points examined. In contrast, the Fab antibody fragment diffused through the neural retina to the retinal pigment epithelial layer at the 1-hr time point and persisted in this location for up to 7 days. Systemic exposure to test material was low but variable: the highest plasma concentration of the full-length antibody was 20.3 ng/ml, whereas plasma concentrations for the Fab antibody remained below the limit of quantitation (i.e., <7.8 ng/ml). An immune response to the test material was not evident in either treatment group. The half-life in vitreous was 5.6 days for the full-length antibody and 3.2 days for the Fab antibody. The shorter intravitreal half-life of the Fab antibody is related to its smaller size and its significant diffusion through the retinal layers. The differences in pharmacokinetics and tissue distribution that are noted between the full-length and Fab antibodies in this study identify potential therapeutic approaches that may be exploited in specific disease conditions.
玻璃体内注射后重组蛋白进入视网膜的情况目前了解甚少。为比较¹²⁵碘（I）标记的全长人源化抗人表皮生长因子受体2单克隆抗体（rhuMAb HER2，148 kD）和¹²⁵碘标记的人源化抗血管内皮生长因子Fab抗体（48.3 kD）在双侧推注玻璃体内注射后第0天（每组5只动物）的眼内组织分布、药代动力学及安全性，对雄性恒河猴（15至28月龄；2.8 - 3.3 kg）进行了一项研究。每只眼给药剂量为25微克（9 - 10微居里），溶于50微升溶液中。动物分别在第0天（给药后1小时）、第1天、第4天、第7天和第14天安乐死。安全性评估包括直接检眼镜检查、眼压测量、临床观察、体重以及血液学和临床化学指标检测。每天（仅血液）和尸检时采集血液和玻璃体样本用于药代动力学研究及检测针对受试物的抗体；通过微量放射自显影评估受试物在眼组织中的分布。所有动物均完成了研究。微量放射自显影显示，在任何检测时间点，全长抗体均未穿透视网膜内界膜。相比之下，Fab抗体片段在1小时时间点扩散穿过神经视网膜到达视网膜色素上皮层，并在该位置持续存在长达7天。全身对受试物的暴露量较低但存在差异：全长抗体的最高血浆浓度为20.3纳克/毫升，而Fab抗体的血浆浓度始终低于定量下限（即<7.8纳克/毫升）。两个治疗组均未出现对受试物的免疫反应。全长抗体在玻璃体内的半衰期为5.6天，Fab抗体为3.2天。Fab抗体较短的玻璃体内半衰期与其较小的尺寸以及通过视网膜各层的显著扩散有关。本研究中全长抗体和Fab抗体在药代动力学和组织分布上的差异确定了在特定疾病状态下可能采用的潜在治疗方法。
