The study involved a more dose-dense regimen than the proposed human dosing frequency of every 2 weeks which is being used herein. Although more frequent administration of antigens can impact immunogenic responses, it is unlikely that more frequent dosing would interfere with immunogenicity of this drug product as the antig ens expressed are not intended for the rodent and are selected to cross a broad spectrum of major histocompatibility complex (MHC) specificities. A more aggressive regimen than the intended clinical dosing frequency was selected to thoroughly characterize drug product toxicity. Although the vaccine design of NCI-4650 is 100% personalized (i.e., sequences coding for tumor-associated neoantigens unique to the subject and predicted to be most immunogenic will be administered for each subject), the sequence tested in this toxicology study represented a human-based sequence of comparable size and composition to the NCI-4650 that will be generate d for each subject in the clinical study, and was manufactured in a similar ma nner to how NCI-4650 will be manuf actured in this clinical study, with the exception that the immunogenic neoantigens coded by NCI-4650 will be determined by laboratory techniques at the NC I-SB and bioinformatics prediction algorithms described in Section 3.2.R in IND 17390. The primary driver of safety that can be adequately assessed non-clinically is that of the LNP and mRNA chemistry, and any immunological effects of antigen expression is likely to be subject-specific and more adequately assessed clinically. The results of the repeat-dose toxicity study in rats indicated that mR NA-4157 was tolerated at all dose levels (no mRNA-4157 related mortality was observed). In addition, no changes in body temperature (measured indirectly by clinical observation), serum chemistry, urinalysis, or ocular findings were noted. Weekly administration of mRNA-4157 to Sprague Dawley rats (both male and female) at dose levels of 0.012, 0.035, and 0.117 mg was associated with a dose-dependent VOLJKWWRPLOGGHFUHDVHLQERG\ZHLJKWJDLQDWGRVHV 0.012 mg and this correlated with reduced food consumption. Clinical observations of inject ion-site reaction (ISR) were observed at all doses and included erythema (slight to mild) and edema (slight to moderate) that increased in incidence and severity with increasing dose. These clinical observations were associated with gross and microscopic changes at the injection site and associated enlargement of lymph nodes. Hematology changes consistent with inflammation were also observed and included mild to moderate increased white blood cells (WBCs) (dri ven primarily by neutrophils), and a decrease in lymphocytes. Systemic effects were primarily considered responses to local inflammation at the injection site.