Clinical Pharmacology and Safety Sciences, R&D, AstraZeneca, Cambridge, UK.
Oncology R&D, AstraZeneca, Cambridge, UK.
Arch Toxicol. 2022 Feb;96(2):613-624. doi: 10.1007/s00204-021-03197-8. Epub 2022 Jan 1.
The receptor tyrosine kinase, MERTK, plays an essential role in homeostasis of the retina via efferocytosis of shed outer nuclear segments of photoreceptors. The Royal College of Surgeons rat model of retinal degeneration has been linked to loss-of-function of MERTK, and together with the MERTK knock-out mouse, phenocopy retinitis pigmentosa in humans with MERTK mutations. Given recent efforts and interest in MERTK as a potential immuno-oncology target, development of a strategy to assess ocular safety at an early pre-clinical stage is critical. We have applied a state-of-the-art, multi-modal imaging platform to assess the in vivo effects of pharmacological inhibition of MERTK in mice. This involved the application of mass spectrometry imaging (MSI) to characterize the ocular spatial distribution of our highly selective MERTK inhibitor; AZ14145845, together with histopathology and transmission electron microscopy to characterize pathological and ultra-structural change in response to MERTK inhibition. In addition, we assessed the utility of a human retinal in vitro cell model to identify perturbation of phagocytosis post MERTK inhibition. We identified high localized total compound concentrations in the retinal pigment epithelium (RPE) and retinal lesions following 28 days of treatment with AZ14145845. These lesions were present in 4 of 8 treated animals, and were characterized by a thinning of the outer nuclear layer, loss of photoreceptors (PR) and accumulation of photoreceptor outer segments at the interface of the RPE and PRs. Furthermore, the lesions were very similar to that shown in the RCS rat and MERTK knock-out mouse, suggesting a MERTK-induced mechanism of PR cell death. This was further supported by the observation of reduced phagocytosis in the human retinal cell model following treatment with AZ14145845. Our study provides a viable, translational strategy to investigate the pre-clinical toxicity of MERTK inhibitors but is equally transferrable to novel chemotypes.
受体酪氨酸激酶 MERTK 通过吞噬感光细胞脱落的外核段,在视网膜的动态平衡中发挥重要作用。皇家外科学院(Royal College of Surgeons)大鼠视网膜变性模型与 MERTK 功能丧失有关,与 MERTK 敲除小鼠一起,可模拟人类 MERTK 突变引起的色素性视网膜炎。鉴于最近人们对 MERTK 作为潜在免疫肿瘤学靶点的关注,开发一种策略以在早期临床前阶段评估眼部安全性至关重要。我们应用了最先进的多模态成像平台来评估在体药物抑制 MERTK 在小鼠体内的作用。这涉及应用质谱成像(MSI)来描绘我们高度选择性的 MERTK 抑制剂(AZ14145845)在眼部的空间分布;结合组织病理学和透射电子显微镜,来描绘对 MERTK 抑制的病理和超微结构变化。此外,我们评估了人视网膜体外细胞模型在识别 MERTK 抑制后吞噬作用扰动方面的效用。我们发现,在 28 天的 AZ14145845 治疗后,视网膜色素上皮(RPE)和视网膜病变中存在高局部总化合物浓度。在 8 只治疗动物中有 4 只出现病变,表现为外核层变薄、感光细胞(PR)丧失和 PR 与 RPE 交界处的感光细胞外节堆积。此外,病变与 RCS 大鼠和 MERTK 敲除小鼠中的病变非常相似,表明这是一种由 MERTK 诱导的 PR 细胞死亡机制。这一观察结果进一步得到了以下观察结果的支持:在 AZ14145845 治疗后,人视网膜细胞模型中的吞噬作用减少。我们的研究提供了一种可行的、转化性的策略来研究 MERTK 抑制剂的临床前毒性,但同样适用于新型化学型。