No Safety

 Safety pharmacology programme 

No dedicated safety pharmacology studies with mRNA-1273 were conducted. This is considered acceptable in light of the lack of signais on vital organ functions from the completed GLP repeat-dose toxicity studies and clinical studies submitted with MRNA-1273, as recommended by applicable vaccines guidelines (e.g. WHO Guidelines on Nonclinical Evaluation of Vaccines). 

2.3.3. Pharmacokinetics

 No dedicated ADME studies with MRNA-1273 were conducted, which is acceptable as generally nonclinical PK studies are not relevant to support the development and licensure of vaccine for infectious diseases. However, distribution studies should be conducted in the case of new formulations or novel excipients used.

 Accordingly, the biodistribution of the vaccine platform was evaluated with mRNA-1647 in a non-GLP, single-dose, intramuscular injection study in Sprague Dawley rats. The objectives of this study were to determine the tissue distribution and pharmacokinetic characteristics of MRNA-1647 constructs following IM administration.

 mRNA-1647 contains 6 MRNAS, which encode the full length CMV glycoprotein B (gB), and the pentameric glycoprotein H (gH)/glycoprotein L (gL)/UL128/UL130/UL131A glycoprotein complex (Pentamer). The 6 MRNA are formulated at a target mass ratio of 1:1:1:1:1:1 in the Sponsor's standard proprietary SM-102-containing LNPS. It is MRNA vaccine is determined by the lipid nanoparticle content, whereas the influence of the mRNA itself iologically plausible that the distribution of the is considered very limited. Therefore, it is acceptable that the biodistribution study was performed with the same lipid nanoparticles containing another MRNA (i.e. MRNA-1647). 

The amount of the LNPS in the test material differed slightly in particle size from the final vaccine formulation of MRNA-1273. Even though it is not straightforward to understand the impact that the different particle size might have on mRNA tissue distribution, if any, nevertheless the liver distribution is not affected because the average diameter of endothelial fenestrae in the liver sinusoids in the test system (Sprague-Dawley rats) is 161 nm. The observed biodistribution with smaller LNP particle size should thus represent a worst-case scenario. 

A qualified multiplex branched DNA (BDNA) assay was used for determination of MRNA in various tissues in the biodistribution study conducted with MRNA-1647. The LLOQ of the method were set at 0.05 ng/mL for the gB MRNA and UL130 mRNA, and 0.01 ng/mL for the gH, gl, UL128 and UL131A MRNAS. Following single IM injection at 100 ug MRNA-1647, subgroups of 5 rats were sequentially sacrificed pre-dose and 2, 8, 24, 48, 72, and 120 hours after dosing, for quantitation of 6 MRNA constructs in blood and a pre-specified set of organs/tissues. 

 *Concentrations of MRNA-1647 were quantifiable in the majority of tissues examined at the first time point collected (2 hours post-dose) and peak concentrations were reached between 2- and 24-hours post-dose in tissues with exposures above that of plasma. Besides injection site [muscle] and lymph nodes [proximal and distal), increased mRNA concentrations (compared to plasma levels) were found in the spleen and eye. Both tissues were examined in the frame of the toxicological studies conducted with mRNA-1273 final vaccine formulation. Low levels of mRNA could be detected in all examined tissues except the kidney. This included heart, lung, testis and also brain tissues, indicating that the MRNA/LNP platform crossed the blood/brain barrier, although to very low levels (2-4% of the plasma level). Liver distribution of MRNA-1647 is also evident in this study, consistent with the literature reports that liver is a common target organ of LNPS.* 

安全药理学计划

 没有对 mRNA-1273 进行专门的安全药理学研究。 鉴于已完成的 GLP 重复剂量毒性研究和随 mRNA-1273 提交的临床研究缺乏重要器官功能的迹象，这被认为是可以接受的，如适用疫苗指南（例如 WHO 疫苗非临床评估指南）的建议。

 2.3.3. 药代动力学

  没有使用 mRNA-1273 进行专门的 ADME 研究，这是可以接受的，因为一般非临床 PK 研究与支持传染病疫苗的开发和许可无关。 但是，如果使用新配方或新赋形剂，则应进行分布研究。

  因此，在 Sprague Dawley 大鼠的非 GLP、单剂量、肌内注射研究中，用 mRNA-1647 评估了疫苗平台的生物分布。 本研究的目的是确定肌肉注射给药后 mRNA-1647 构建体的组织分布和药代动力学特征。

  mRNA-1647 包含 6 个 MRNAS，编码全长 CMV 糖蛋白 B (gB) 和五聚体糖蛋白 H (gH)/糖蛋白 L (gL)/UL128/UL130/UL131A 糖蛋白复合物 (Pentamer)。  6 种 mRNA 以 1:1:1:1:1:1 的目标质量比在赞助商的标准专有 SM-102 含 LNPS 中配制。  mRNA 疫苗是由脂质纳米颗粒的含量决定的，而 mRNA 本身的影响在生物学上是合理的，认为 mRNA 的分布非常有限。 因此，使用含有另一种 mRNA（即 mRNA-1647）的相同脂质纳米颗粒进行生物分布研究是可以接受的。

 测试材料中 LNPS 的量在粒度上与 mRNA-1273 的最终疫苗制剂略有不同。 尽管了解不同粒径可能对 mRNA 组织分布（如果有的话）的影响并不简单，但肝脏分布不会受到影响，因为测试系统中肝窦中内皮窗孔的平均直径（Sprague-  Dawley 大鼠）是 161 nm。 因此，观察到的具有较小 LNP 粒径的生物分布应该代表最坏的情况。

 在使用 mRNA-1647 进行的生物分布研究中，使用合格的多重分支 DNA (BDNA) 测定法测定各种组织中的 mRNA。 该方法的 LLOQ 对于 gB mRNA 和 UL130 mRNA 设置为 0.05 ng/mL，对于 gH、gl、UL128 和 UL131A MRNAS 设置为 0.01 ng/mL。 在单次肌肉注射 100 ug mRNA-1647 后，5 只大鼠的亚组在给药前和给药后 2、8、24、48、72 和 120 小时依次处死，用于定量血液中的 6 种 mRNA 构建体和预 指定的一组器官/组织。

  在收集的第一个时间点（给药后 2 小时），在大多数检查的组织中，mRNA-1647 的浓度是可量化的，并且在暴露于血浆浓度以上的组织中，在给药后 2 和 24 小时之间达到峰值浓度。 除了注射部位 [肌肉] 和淋巴结 [近端和远端)，在脾脏和眼睛中发现 mRNA 浓度增加（与血浆水平相比）。 在用 mRNA-1273 最终疫苗制剂进行的毒理学研究的框架内检查了两种组织。 在除肾脏外的所有检查组织中都可以检测到低水平的 mRNA。 这包括心脏、肺、睾丸和脑组织，表明 mRNA/LNP 平台穿过了血/脑屏障，尽管水平非常低（血浆水平的 2-4%）。 本研究中 mRNA-1647 的肝脏分布也很明显，这与文献报道肝脏是 LNPS 的常见靶器官一致。