Toxicological and pharmacokinetic properties of QPI-1007, a chemically modified synthetic siRNA targeting caspase 2 mRNA, following intravitreal injection.

We report the toxicological and pharmacokinetic properties of the synthetic, small interfering RNA (siRNA), QPI-1007, following intravitreal administration. QPI-1007 is a chemically modified siRNA designed to act via the RNA interference (RNAi) pathway to temporarily inhibit expression of the caspase 2 protein and is being developed as a neuroprotectant for the treatment of nonarteritic anterior ischemic optic neuropathy and other optic neuropathies such as glaucoma that result in the death of retinal ganglion cells. The half-life of QPI-1007 in the vitreous and retina/choroid in the Dutch Belted rabbit was about 2 days, and there was no sign of accumulation after repeated administrations at either 2- or 4-week dosing intervals in the rabbit. QPI-1007 was well tolerated in Dutch Belted rabbits following single or repeated intravitreal administrations of up to 11 doses over 9 months. Test-article-related effects were limited to the eyes, with minimal to mild vitreal cellular infiltration being the major finding, which was reversible. In repeated-dose studies, a modest reduction in B-wave amplitude obtained by electroretinography was observed in animals treated with the highest dose level tested (3 mg, which is equivalent to a 12 mg/eye human dose) that was not considered to be clinically meaningful. Administration in the rat of either a single bolus intravenous (i.v.) injection of 100 mg/kg or daily bolus i.v. injections of 75 mg/kg/day for 28 days failed to elicit any macroscopic or microscopic changes, suggesting a low risk for systemic toxicity. QPI-1007 was negative in three genetic toxicity studies. Overall, the nonclinical studies support the further development of QPI-1007.

Toxicological and pharmacokinetic properties of chemically modified siRNAs targeting p53 RNA following intravenous administration.

We report the toxicological and pharmacokinetic properties of the synthetic, small interfering RNA I5NP following intravenous administration in rodents and nonhuman primates. I5NP is designed to act via the RNA interference (RNAi) pathway to temporarily inhibit expression of the pro-apoptotic protein p53 and is being developed to protect cells from acute ischemia/reperfusion injuries such as acute kidney injury that can occur during major cardiac surgery and delayed graft function that can occur following renal transplantation. Following intravenous administration, I5NP was very rapidly cleared from plasma was distributed predominantly to the kidney, with very low levels in liver and other tissues. Doses of 800 mg/kg I5NP in rodents, and 1,000 mg/kg I5NP in nonhuman primates, were required to elicit adverse effects, which in the monkey were isolated to direct effects on the blood that included a sub-clinical activation of complement and slightly increased clotting times. In the rat, no additional adverse effects were observed with a rat analogue of I5NP, indicating that the effects likely represent class effects of synthetic RNA duplexes rather than toxicity related to the intended pharmacologic activity of I5NP. Taken together, these data support clinical testing of intravenous administration of I5NP for the preservation of renal function following acute ischemia/reperfusion injury.

Local tolerance and systemic safety of pegaptanib sodium in the dog and rabbit.

PURPOSE: To evaluate the local tolerance, systemic toxicity, and toxicokinetics in dogs and rabbits of pegaptanib sodium, an aptamer that targets vascular endothelial growth factor (VEGF(165)). METHODS: Dogs received biweekly, bilateral, intravitreous (IVT) injections of pegaptanib sodium for 9 months at doses of 0.3 (n = 10), 1 (n = 10), or 3 mg (n = 14); 14 control dogs received phosphate-buffered saline (PBS). In rabbits, pegaptanib sodium was administered by IVT injection biweekly for 6 months at doses of 0.2 (n = 14), 0.67 (n = 14), or 2 mg (n = 18); 18 rabbits received PBS. The systemic and ocular safety of pegaptanib sodium was assessed. Assessments in both dogs and rabbits included complete ophthalmologic examinations, serum chemistry, hematology, urinalysis, and coagulation assessments, as well as gross and microscopic pathologic examination. In addition, dogs were assessed by electroretinography and electrocardiography. In a cardiovascular safety study, loading intravenous boluses and maintenance infusions of pegaptanib sodium or PBS were administered to dogs (n = 4) in an ascending dose design, with each dose level separated by 2-3 days. The pegaptanib dosing regimens were designed to achieve pegaptanib plasma concentrations of approximately 90, 270, or 900 ng/mL. RESULTS: There were no pegaptanib sodium-associated clinical, ophthalmologic, pathologic, or cardiovascular abnormalities at doses of pegaptanib that achieved systemic and ocular exposure levels in excess of those associated with the recommended pegaptanib IVT dosing regimen of 0.3 mg per study eye in patients with age-related macular degeneration. CONCLUSION: These studies, together with data from clinical trials, provide strong evidence that inhibition of VEGF(165) by pegaptanib in the eye is a safe therapy for the treatment of ocular neovascular disease.

Inhibition of rat respiratory-tract cytochrome P-450 activity after acute low-level m-xylene inhalation: role in 1-nitronaphthalene toxicity.

The xylenes are commonly used industrial solvents that have been shown to inhibit cytochrome P-450 (CYP450) activities in an organ- and isozyme-specific pattern. This study examined the dose-response and durational effects of m-xylene inhalation on cytochrome P-450 activities in the respiratory tract and liver as well as the effects of these CYP450 alterations on 1-nitronaphthalene (1-NN)-induced respiratory or hepatic toxicity. After m-xylene inhalation exposure there was a dose-related inhibition of all nasal mucosa CYPs examined. At 300 ppm, inhibition was sustained up to 2 days after exposure, but on day 5 all CYP activities were increased. There was also dose-related inhibition of lung CYPs 2B1, 2E1, and 4B1. The activities of these CYPs returned to those of control by day 2 but lung CYP 2B1 was increased 5 days following m-xylene exposure. Hepatic CYP 2E1 activity was increased immediately following m-xylene exposure (300 ppm). CYP 2B1 and CYP 1A2 activities were increased through day 2, all activities returning to control values 5 days postexposure. 1-NN treatment caused severe respiratory toxicity that was prevented by prior m-xylene exposure. Lactate dehydrogenase (LDH) and protein were increased in nasal lavage fluid (NLF) but gamma-glutamyl transferase (GGT) was unchanged. m-Xylene coexposure prevented or ameliorated the increases in LDH and protein but increased GGT. 1-NN-induced increases in bronchoalveolar lavage fluid (BALF) LDH and GGT were attenuated by m-xylene. 1-NN caused pronounced histopathological changes in both respiratory and olfactory regions of the nasal mucosa. Lesions in both regions were characterized by acute epithelial necrosis and exfoliation and suppurative exudate in the airways. These changes were prevented by m-xylene coexposure. Serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels were not changed in animals exposed to 1-NN but were increased by m-xylene coexposure. Low-level m-xylene exposure organ-selectively altered CYP450 isozyme activities and subsequent 1-NN toxicity.

A comparison of mathematical methods for the determination of in vitro dissolution constants for glass fibers.

Biopersistence plays a significant role in determining the potential bioactivity of respirable fibers. In vivo biopersistence in the lung is frequently assessed by in vitro fiber dissolution studies using simulated biological solutions and flow-through techniques. The dissolution rate (k) of a fiber is typically determined by elemental analysis of the flow-through solution to measure the mass of material leached from the fibers over a given time. Various methods may be used to estimate the value of k from these results. The present study compared the in vitro dissolution characteristics of seven experimental glass fiber compositions to those obtained for four recognized fiber compositions (MMVF 10-glass fiber; MMVF 11-glass fiber; MMVF 21-rockwool fiber; crocidolite fiber). Fiber dissolution was examined over a 17-wk period using a flow-through system designed to simulate the conditions encountered by fibers in the extracellular environment of the lung. Mass loss and changes in fiber diameter were determined over time and were then used to calculate k using five different methods. Although the selected methodologies did not produce identical estimations of k for each fiber, the resulting ranking of fiber solubility for each method was consistent. The seven experimental glass fibers were found to have k values intermediate between those of MMVF 11 and MMVF 21.