Safety (toxicity), pharmacokinetics, immunogenicity, and impact on elements of the normal immune system of recombinant human IL-15 in rhesus macaques.

IL-15 uses the heterotrimeric receptor IL-2/IL-15Rß and the γ chain shared with IL-2 and the cytokine-specific IL-15Rα. Although IL-15 shares actions with IL-2 that include activation of natural killer (NK) and CD8 T cells, IL-15 is not associated with capillary leak syndrome, activation-induced cell death, or with a major effect on the number of functional regulatory T cells. To prepare for human trials to determine whether IL-15 is superior to IL-2 in cancer therapy, recombinant human IL-15 (rhIL-15) was produced under current good manufacturing practices. A safety study in rhesus macaques was performed in 4 groups of 6 animals each that received vehicle diluent control or rhIL-15 at 10, 20, or 50 µg/kg/d IV for 12 days. The major toxicity was grade 3/4 transient neutropenia. Bone marrow examinations demonstrated increased marrow cellularity, including cells of the neutrophil series. Furthermore, neutrophils were observed in sinusoids of enlarged livers and spleens, suggesting that IL-15 mediated neutrophil redistribution from the circulation to tissues. The observation that IL-15 administration was associated with increased numbers of circulating NK and CD8 central and effector-memory T cells, in conjunction with efficacy studies in murine tumor models, supports the use of multiple daily infusions of rhIL-15 in patients with metastatic malignancies.

Renal histopathology in toxicity and carcinogenicity studies with tert-butyl alcohol administered in drinking water to F344 rats: a pathology working group review and re-evaluation.

An independent Pathology Working Group (PWG) re-evaluated the kidney changes in National Toxicology Program (NTP) toxicology/carcinogenicity studies of tert-butyl alcohol (TBA) in F344/N rats to determine possible mode(s) of action underlying renal tubule tumors in male rats at 2-years. In the 13-week study, the PWG confirmed that the normal pattern of round hyaline droplets in proximal convoluted tubules was replaced by angular droplet accumulation, and identified precursors of granular casts in the outer medulla, changes typical of alpha(2u)-globulin (α(2u)-g) nephropathy. In the 2-year study, the PWG confirmed the NTP observation of increased renal tubule tumors in treated male groups. Linear papillary mineralization, another hallmark of the α(2u)-g pathway was present only in treated male rats. Chronic progressive nephropathy (CPN) was exacerbated in high-dose males and females, with a relationship between advanced grades of CPN and renal tumor occurrence. Hyperplasia of the papilla lining was a component of CPN in both sexes, but there was no pelvic urothelial hyperplasia. High-dose females showed no TBA-related nephrotoxicity. The PWG concluded that both α(2u)-g nephropathy and exacerbated CPN modes of action were operative in TBA renal tumorigenicity in male rats, neither of which has relevance for human cancer risk.