Adverse vacuolation in multiple tissues in cynomolgus monkeys following repeat-dose administration of a PEGylated protein.

PEGylation is considered a safe mechanism to enhance the pharmacokinetics (PK) and pharmacodynamics (PD) of biotherapeutics. Previous studies using PEGylation as a PK enhancement tool have reported benign PEG-related vacuolation in multiple tissues. This paper establishes a threshold for PEG burden beyond which there are alterations in tissue architecture that could potentially lead to dysfunction. As part of the nonclinical safety assessment of Compound A, a 12 kDa protein conjugated to a 40 kDa branched PEG molecule, monkeys were dosed subcutaneously twice weekly for 3 months at protein doses resulting in weekly PEG doses of 8, 24, 120, or 160 mg/kg. Consistent with previous reports with PEGylated biomolecules, Compound A administration resulted in intracellular vacuoles attributed to the PEG moiety in macrophages in numerous tissues and epithelial cells in the choroid plexus and kidney. Vacuolation occurred at all doses with dose-dependent severity and no evidence of recovery up to 2 months after dosing cessation. The vacuolation was considered nonadverse at PEG doses ≤120 mg/kg/week. However, at 160 mg/kg/week PEG, the vacuolation in choroid plexus, pituitary gland, kidney, and choroid of the eye was considered adverse due to significant alterations of tissue architecture that raised concern for the possibility of compromised tissue function. To our knowledge, this is the first report of potentially adverse cellular consequences of PEG accumulation in tissues other than kidney. Furthermore, the lack of reversibility of vacuolation coupled with the lack of a biomarker for intracellular PEG accumulation highlights a potential risk that should be weighed against the benefits of PK/PD enhancement for long-term administration of PEGylated compounds at high doses.

Occurrence of spontaneous pancreatic lesions in normal and diabetic rats: a potential confounding factor in the nonclinical assessment of GLP-1-based therapies.

Glucagon-like peptide 1-based therapies, collectively described as incretins, produce glycemic benefits in the treatment of type 2 diabetes. Recent publications raised concern for a potential increased risk of pancreatitis and pancreatic cancer with incretins based in part on findings from a small number of rodents. However, extensive toxicology assessments in a substantial number of animals dosed up to 2 years at high multiples of human exposure do not support these concerns. We hypothesized that the lesions being attributed to incretins are commonly observed background findings and endeavored to characterize the incidence of spontaneous pancreatic lesions in three rat strains (Sprague-Dawley [S-D] rats, Zucker diabetic fatty [ZDF] rats, and rats expressing human islet amyloid polypeptide [HIP]; n = 36/group) on a normal or high-fat diet over 4 months. Pancreatic findings in all groups included focal exocrine degeneration, atrophy, inflammation, ductular cell proliferation, and/or observations in large pancreatic ducts similar to those described in the literature, with an incidence of exocrine atrophy/inflammation seen in S-D (42-72%), HIP (39%), and ZDF (6%) rats. These data indicate that the pancreatic findings attributed to incretins are common background findings, observed without drug treatment and independent of diet or glycemic status, suggesting a need to exercise caution when interpreting the relevance of some recent reports regarding human safety.