Therapeutic pegylated interferon-␣s (IFN-␣) are mixtures of positional isomers that have been monopegylated at specific sites on the core IFN-␣ molecule. The pegylation results in lower in vitro specific activity associated with the core IFN-␣ molecule that is related to the site of pegylation and size of polyethylene glycol (PEG) attached. We prepared purified, homogeneous, positional pegylation isomers of IFN-␣2b that were monopegylated using 5-30-kDa linear PEG molecules attached at 7 primary reactive amino acid residues: Chronic hepatitis C is considered one of the major causes of chronic liver disease, cirrhosis, and hepatocellular carcinoma and is the most common reason for liver transplantation in the United States (1). It is estimated that there are 3 million chronically infected individuals in the United States and over 170 million worldwide (1). Treatment of hepatitis C has evolved from the use of interferon-␣ (IFN-␣), 1 either alone or in combination with ribavirin, to the newer pegylated interferons (PEGIFNs), which have provided a dramatic increase in virological response, especially in combination with ribavirin. Standard IFN-␣ therapy has a short (Ͻ12-h) half-life that requires subcutaneous injection three times weekly to maintain effective levels in the blood (2). The short half-life of IFN-␣ has led to the development of longer lasting preparations achieved by the attachment of a large polyethylene glycol (PEG) molecule directly to IFN-␣. Two different commercial preparations of PEG-IFN-␣ have been developed for clinical use, PEG-IFN-␣2b (PEG-INTRON®) and PEG-IFN-␣2a (Pegasys®); both have long half-lives (40 and 80 h, respectively) that permit once weekly administration (3). Both of these preparations have been demonstrated to be effective for the treatment of patients with hepatitis C (4), and clinical trial results have shown further that both of the pegylated molecules produce sustained viral response rates superior to those achieved with their respective standard IFN-␣s (5-7).Whereas pegylation has proven to be highly effective for slowing the clearance of biological molecules, including IFN-␣, and thus increasing serum half-life, it has been shown to also modify in vitro biological activity (8). For instance, we have reported that pegylation of IFN-␣2b with a 12-kDa linear PEG molecule results in a preparation that has a specific activity of 28% relative to IFN-␣2b; the loss in activity was not due to structural perturbation of the core IFN-␣2b core protein (9). Other groups have reported that pegylation of IFN-␣2a with a 40-kDa branched PEG molecule results in a preparation that contains from 1 to 7% relative specific activity compared with IFN-␣2a (10, 11). These two pegylated interferon-␣s (PEG-IFN␣s) differ substantially in their postpegylation constituent properties. PEG-IFN-␣2b has a 12-kDa linear PEG molecule attached using succinimidyl carbonate polyethylene glycol (SC-PEG) chemistry via a covalent urethane-like bond to the IFN␣2b protein (12). The pegylation linkage process results...

Reaction pH can be used to select the preferred pegylation site chemistry.

Intravascular administration of recombinant adenovirus (rAd) in cancer patients has been well tolerated. However, dose-limiting hemodynamic responses associated with suppression of cardiac output have been observed at doses of 7.5 x 10(13) particles. While analysis of hemodynamic responses induced by small-molecule pharmaceuticals is well established, little is known about the cardiovascular effects of rAd. Telemetric cardiovascular (CV) monitoring in mice was utilized to measure hemodynamic events following intravascular rAd administration. Electrocardiogram analysis revealed a block in the SA node 3-4 min postinfusion, resulting in secondary pacemaking initiated at the AV node. This was associated with acute bradycardia, reduced blood pressure, and hypothermia followed by gradual recovery. Adenovirus-primed murine sera with high neutralizing antibody (nAb) titers could inhibit CV responses, whereas human sera with equivalent nAb titers induced by natural infection were, surprisingly, not inhibitory. Interestingly, repeat dosing within 2-4 h of the primary injection resulted in desensitization, resembling tachyphylaxis, for subsequent CV responses. Last, depletion of Kupffer cells prior to rAd infusion precluded induction of CV responses. These inhibitory effects suggest that rAd interactions with certain cells of the reticular endothelial system are associated with induction of CV responses. Significantly, these studies may provide insight into management of acute adverse effects following rAd systemic delivery, enabling a broadening of therapeutic index.

No abstract

As with certain successful protein drug treatments, the attachment of polyethylene glycol (PEG) molecules to recombinant adenovirus (rAd) can augment their therapeutic potential. Unlike these proteins, the rAd particle has thousands of target sites for PEG conjugation. The reliable measurement of the average number of PEG molecules attached to the virion, or the degree of PEGylation (DP), is crucial not only for the characterization of PEGylated virus but also for optimization of the PEGylation reaction. Using a fluorescein-labeled PEG-SPA linker (SPA, succinimidyl ester of PEG propionic acid) with a 5-kDa linear PEG moiety, multiple preparations of fluoro-PEG-rAds were produced under various reaction conditions, purified, and analyzed by size-exclusion high-performance liquid chromatography (HPLC) with fluorescence quantification of the virus peak. The DP was strongly dependent on the percent linker concentration in the reaction. For example, under one set of conditions, fluoro-PEG-rAd samples prepared at 1.3, 2.5, 5.0, 7.4, and 10.0% linker concentration had DPs of approximately 540, 1,000, 1,590, 1,990, and 2,170, respectively. The fluoro-PEG-rAds were compared with a set of nonfluorescent PEG-rAds. Analytical ultracentrifugation in CsCl density gradients showed distinct peaks at decreased buoyant density corresponding to the increased DP of the rAd samples; sodium dodecyl sulfate-polyacrylamide gel electrophoresis/scanning densitometry showed decreased hexon monomer and penton base. Both techniques were used to estimate the DP of nonfluorescent PEG-rAds versus fluoro-PEG-rAds, and anion-exchange HPLC revealed the different surface chemistries of the two vector types. In summary, these studies should provide investigators with the ability to reproducibly prepare and characterize PEGylated rAds or other large viral or nonviral particles for further in vivo studies.