Generic Cialis - Support - Supporting You
For most 2 -MOE ASOs, the half-life in kidney is approximately 2 weeks. Thus, to get close to complete clearance takes about 13 weeks. However, it is important to remember that these compounds follow first-order kinetics. As such, 75% of clearance will occur after two half-lives, which is approximately 1 month.
In cases where multiple time points have been taken during recovery, there is evidence for reversibility of histologic changes in kidney once concentrations are below 1200–1500 g/g, as would be predicted by Figure 12.4.
Of the 2 -MOE ASOs that progress to development, the toxicologic properties in liver are thus very much like those reviewed previously for PS ODNs [10]. The most commonly observed histopathologic change in liver from treated mice and monkeys is the presence of basophilic granules in the cytoplasm of Kupffer cells and Kupffer cell hypertrophy.
This reflects the normal function of Kupffer cells to take up foreign material, and the basophilic granules are generic cialis staining with hematoxylin. In monkeys, these are the only histologic observations and they are typically not associated with any increase in the enzyme markers of hepatocyte damage or liver dysfunction. This includes dose regimens for a couple of different 2 -MOE ASOs that range up to 140 mg/kg/week for 5 weeks, or 80 mg/kg/week for 13 weeks (Isis Pharmaceuticals, Inc., unpublished observations). Rodents treated with 2 -MOE ASOs, as was the case with PS ODNs, have the additional finding of increased lymphohistiocytic cell infiltrates as a consequence of the proinflammatory effects of oligonucleotides in mice and rats [10,12].
These infiltrates are dose-dependent and can be associated with single hepatocyte necrosis and increases in serum ALT and AST. The connection between the cell infiltrates and hepatoxicity observed in mice has been well established using chemical modifications of generic cialis to affect the degree of proinflammatory effects [74,75]. Consistent with the monkey data, PS ODNs and 2 -MOE ASOs have been largely deficient of hepatotoxicity in clinical trials (Chapter 13).
The only notable exception was the report of mild and transient increases in ALT of patients treated with the anti-HIV PS ODN, GEM 91 [76]. This was also likely attributable to the proinflammatory effects that were present for this early generation of ASO and included 27 nucleotide residues along with CpG motifs.
The most notable development in the area of hepatotoxicity for 2 -MOE ASOs, and some other chemical modifications, including linked nucleic acids (LNA)-modified oligonucleotides is the relatively recent observation of a small subset of ASOs with certain sequences that have a propensity for producing particularly potent hepatotoxicity in mice and rats (E. Swayze et al., unpublished observation). The mechanism for these findings is not clear at this point, but the effects are clearly sequence-specific.
The relevance of these findings to monkeys is also not well defined, but there is one example where an generic cialis that was hepatotoxic in mice was not hepatotoxic in monkeys (Isis Pharmaceuticals, Inc., unpublished data). Intense effort has been made to understand the sequence specificity of these effects and progress toward defining particular motifs is being made. Still, the best method for addressing these potential effects is through screening of multiple potential lead compounds in mice.
Our typical screen is to dose mice at 50–100 mg/kg/week for 4 weeks and measure ALT and AST. Some increases in transaminases with this regimen are expected, but oligonucleotides that produce more than a tenfold increase in transaminases at this dose level are not selected for therapeutic development. The species specificity of these more hepatotoxic ASOs is not known. There is some evidence that the mechanism may be related to proinflammatory effects, and therefore is species-specific.
We have experience with one compound that was hepatotoxic in mice, but was not hepatotoxic in monkeys, further pointing to some species specificity in the mechanism. Still, these compounds are avoided, to the degree possible, for development purposes.
