Insulin Glargine: A Reevaluation of Rodent Carcinogenicity Findings

The 1995 to 1997 lifetime carcinogenicity studies of insulin glargine in rats and mice were reanalyzed and reassessed for their validity according to current guidelines. In 2-year studies, 50 animals per sex and per group were used. Survival rates between weeks 80 and 90 in female mice and rats were greater than 20 animals in all groups, fulfilling current Food and Drug Administration requirements that enough animals lived long enough to provide adequate exposure to glargine and to be at risk of forming late-developing tumors. Exposure to 5 or 12.5 IU/kg glargine was similar to or 2 to 3 times greater than 5 IU/kg neutral protamine Hagedorn insulin, respectively. Using statistical methods recommended by current guidelines, no significant effect of glargine on mammary gland neoplastic lesions in female rodents was found, confirming earlier results. Thus, both studies can be considered valid according to contemporary standards. Insulin glargine does not present a carcinogenic risk.