PEG-interferon conjugates: effects of length and structure of linker

Di-branched (Y-shaped) polyethylene glycols (PEGs) are considered more effective than linear molecules to enhance the efficacy of the conjugated drug. In the present study interferon α-2a was conjugated with three different 40 KDa di-branched PEGs. The results of this study show that length and/or the structure of linker between PEG and the protein is also involved in the synthesis, in vitro biological activity and stability of the conjugate. Three conjugates i.e., mPEG2L-IFN, mPEG2P-IFN and mPEG(2)M-IFN yielded 25%, 24% and 17%, with bioactivities 2.8 x 10(6) IU/mg, 3.95 x 10(6) IU/mg and 6.7 x 10(6) IU/mg, respectively. The order of bioactivity stability is mPEG2L-IFN > mPEG2P-IFN > mPEG2M-IFN > IFN (native). We report that although lengthy linkers are more reactive in terms of conjugation, they have opposite effect on the in vitro bioactivity of the conjugate. PEGylation as a whole increases the stability of the conjugate, and linkers also add in stability.

Stability of an extemporaneously prepared recombinant human interferon alfa-2b eye drop formulation

PURPOSE

The stability of an extemporaneously prepared recombinant human interferon alfa-2b (rh-IFN-alpha2b) eye drop formulation was studied.

METHODS

A volume of 3 x 10(6) International Units (IU) of rh-IFN-alpha2b formulated in solution was diluted with 5 mL of a 0.01% benzalkonium chloride solution. The stability of the extemporaneous formulation was evaluated for 30 days at room temperature (5 +/- 3 degrees C) and at 28 +/- 2 degrees C. Solutions were periodically subjected to bioactivity assay (antiviral titration), enzyme-linked immunosorbent assay, preservative-efficacy and sterility testing, organoleptic evaluation, and pH testing. Preservative efficacy was tested against five microorganisms. The organoleptic characteristics were verified by checking for the transparency and absence of suspended solids against light and dark backgrounds. Statistical significance was determined using analysis of variance after a comparison of the homogeneity of variance (Bartlett's test).

RESULTS

Results from this evaluation indicated that the formulation was stable for 15 days at 5 +/- 3 C. During this storage period, the biological activity varied between 80 and 125% of the nominal value (0.5 x 10(6) IU/mL). The formulation was sterile and organoleptically acceptable. The pH ranged from 6.7 to 7.3, and the preservative was effective. The formulation was stable for 7 days when stored at 28 +/- 2 degrees C. The formulation remained sterile, colorless, and without suspended solids. The pH range was 6.7-7.3.

CONCLUSION

An extemporaneously pre -pared rh-IFN-alpha2b eye drop formulation was stable at 5 +/- 3 degrees C for 15 days and at 28 +/- 2 degrees C for 7 days.

Pegylated protein encapsulated multivesicular liposomes: a novel approach for sustained release of interferon alpha

Hepatitis C viral chemotherapy suffers from a relatively short half-life of the interferon alpha-2a (IFN alpha). To address this issue, we investigated the effects of polyethylene glycol modification and their subsequent encapsulation in multivesicular liposomes (MVLs), on the release properties of IFN alpha. In the present study, interferon-alpha was conjugated with methoxy-polyethylene glycol (mPEG, MW 5000). Prepared IFN alpha-mPEG5000 conjugate (IFN alpha-mPEG5000) was purified with size exclusion chromatography. The relative in vitro anti-viral activity of pegylated interferon alpha-2a was found to 87.9% of the unmodified IFN alpha. Pegylated IFN alpha encapsulated multivesicular liposomes were prepared by double emulsification technique followed by evaporation of organic solvents from chloroform ether spherules suspended in water. Prepared MVLs were then characterized for shape, size, vesicle count, encapsulation efficiency, and in vitro release rate. In process stability studies of pegylated IFN alpha protein exhibited better stability when exposed to chloroform: diethyl ether (1:1 ratio) mixture as well as variable vortexing time as compared to native IFN alpha. Relatively high percentage of encapsulation of protein ( approximately 75%) was achieved. In vitro release profile of pegylated IFN alpha-mPEG5000 containing MVLs in the PBS showed lower initial burst release with sustained and incomplete release over a period of 1 week. In contrast, native IFN alpha entrapped MVLs were observed as higher initial burst release, i.e., nearly 35% followed by almost complete release. The results confirmed the possibility of multivesicular liposomes as a long-acting or sustained-release delivery system using a combination of pegylation and encapsulation technique for controlled delivery of interferon alpha.

Long-acting interferon-alpha 2a modified with a trimer-structured polyethylene glycol: preparation, in vitro bioactivity, in vivo stability and pharmacokinetics

The proper selection of size and shape for polyethylene glycol (PEG) is one of the most important points in PEGylation technology. Therefore, PEGs of various sizes and shapes have been widely developed to endow specific properties. In this study, a unique, trimer-structured, 43 kDa PEG was conjugated to interferon-alpha 2a (IFN) by forming an amide bond to improve the pharmacokinetic properties and minimize the loss of IFN bioactivity. Mono-PEGylated IFN (PEG(3)-IFN) prepared by utilizing this unique PEG was purified and characterized by cation-exchange chromatography and MALDI-TOF mass spectrometry. The in vitro bioactivity, in vivo stability, and pharmacokinetics of PEG(3)-IFN were examined and compared to those of native IFN. PEG(3)-IFN exhibited comparable in vitro bioactivities to native IFN and an excellent stability of the conjugation linkage in rat serum and various organs following subcutaneous injection. Furthermore, it showed slow absorption and markedly reduced clearance in rats, thereby increasing the biological half-life by about 40-fold compared to that of native IFN. This is the first report on the application of unique, trimer-structured PEG to bioactive proteins. The results suggest that unique, trimer-structured 43 kDa PEG can provide some advantages to improve the pharmacokinetic properties and to maintain the bioactivity of therapeutic proteins in clinical use.

Synthesis and biological properties of chimeric interferon-alpha2b peptides

We have previously reported the antiproliferative activity of synthetic sequences 29-35 and 122-139 of the interferon-alpha2b (IFN-alpha2b), both probably representing a common receptor recognition domain. In the search of new peptidic agonists, we designed and synthesized the linear peptide (Gly)2-122-137-Gly138-Gly29-30-35-(Gly)2, in which Gly residues replaced the 138 and 29 Cys bound through a disulfide bridge in the native cytokine. Additionally, a cyclic analog was obtained by reaction of the N- and C-terminal ends of the linear fragment. Thus, the distance that separates residues 122 and 35 in the crystalline structure of the IFN-alpha2b was maintained through a (Gly)4 bridge. When the influence of chimeric peptides on the proliferation of WISH cells was studied, it was shown that both derivatives significantly diminished cell growth. A more evident inhibitory effect on (125)I-IFN-alpha2b binding to WISH cell-membrane receptors was observed for both peptides. Results indicated that chimeric IFN-alpha2b peptides behaved as partial agonists of the IFN-alpha2b molecule and may be of interest for drug design purposes.

Pegasys (Hoffmann-La Roche)

Hoffmann-La Roche has developed a PEGylated interferon alpha-2a, Pegasys, for the potential treatment of chronic hepatitis C and hepatitis B virus infection. It was first approved in Switzerland in August 2001 [418260] and was expected to be launched in September/October 2001 [419333]. In May 2000, Roche submitted a BLA to the US FDA, for approval to market Pegasys for the treatment of chronic HCV infection in non-cirrhotic and cirrhotic patients with compensated liver disease [329872], [348368], [367781]. Approval was still pending in December 2000 [387363], [392481]. Roche expects the US launch to take place in the second half of 2001 [400857]. In April 2001, Roche received a complete response letter from the FDA for Pegasys and was working with the FDA to address the questions raised in the letter [407595], [418310]. In August 2001, Roche expected approval for HCV in the US in 2002 and for HBV in 2004 [419333]. At this time, Roche planned to file an sNDA for combination with ribavirin [421285]. By March 2001, EU and Canadian filings had been made [401793]. Roche also planned to launch the product for chronic HBV infection and various malignancies in 2004 and 2005, respectively [400857]. Pegasys was filed for registration in Brazil in the first part of 2000 [418310]. As of December 1999, the drug was in phase II for HCV infection in Japan. It is being developed by Nippon Roche, which intended to extrapolate foreign phase III data for use in an NDA application in Japan [351804]. As a result of a meeting of Japan's PMSB in March 2001, Pegasys may be given priority in the review of its NDA, if submitted [403782]. In August 2001, Schering-Plough entered into a licensing agreement with F Hoffman-La Roche Ltd and Hoffmann-La Roche Inc that settles all patent disputes regarding the two companies' PEGinterferon products. Under the terms of the agreement, Schering-Plough and Roche will cross license to each other all patents applicable to Peg-Intron and Pegasys. The settlement agreement also includes a Schering-Plough sublicense of Enzon's branched PEG patents to Roche [418935], [418956]. Roche is collaborating with Maxim Pharmceuticals to develop PEG-IFN alpha-2a in conjunction with Maxim's Maxamine [378609]. In July 1998, Hoffmann-La Roche and Weston Medical signed a global agreement to license INTRAJECT (Weston's single-use, disposable, prefilled, needle-free injector for subcutaneous delivery of injectable liquid pharmaceuticals) for delivery of Pegasys [292119]. In April 1999, ABN Amro predicted annual sales of SFr 25 million in 2000, rising to SFr 75 million in 2002 [328676]. In September 2000, Merrill Lynch predicted sales of SFr 70 million in 2001, rising to SFr 700 million in 2004 [383742]. In March 2001, Deutsche Bank estimated that the product has sales potential of SFr 1600 million [421009].

Rational design of a potent, long-lasting form of interferon: a 40 kDa branched polyethylene glycol-conjugated interferon alpha-2a for the treatment of hepatitis C

A potent, long-lasting form of interferon alpha-2a mono-pegylated with a 40 kilodalton branched poly(ethylene glycol) was designed, synthesized, and characterized. Mono-pegylated interferon alpha-2a was comprised of four major positional isomers involving Lys31, Lys121, Lys131, and Lys134 of interferon. The in vitro anti-viral activity of pegylated interferon alpha-2a was found to be only 7% of the original activity. In contrast, the in vivo antitumor activity was severalfold enhanced compared to interferon alpha-2a. Pegylated interferon alpha-2a showed no immunogenicity in mice. After subcutaneous injection of pegylated interferon alpha-2a, a 70-fold increase in serum half-life and a 50-fold increase in mean plasma residence time concomitant with sustained serum concentrations were observed relative to interferon alpha-2a. These preclinical results suggest a significantly enhanced human pharmacological profile for pegylated interferon alpha-2a. Results of Phase II/III hepatitis C clinical trials in humans confirmed the superior efficacy of pegylated interferon alpha-2a compared to unmodified interferon alpha-2a.

[Immunochemical and biological properties of synthetic peptide fragments from the 124-144 sequence of human leukocyte interferon alpha2]

Three peptides corresponding to the sequences 124-144, 124-138, 129-144 of the human leukocyte interferon alpha 2 (IFN-alpha 2) were synthesized. The synthesis was performed by DCC-HOBT coupling of protected peptide segments in solution. The segments were obtained by the active ester coupling methodology using base-labile 2-[4-(phenylazobenzyl)sulfonyl]ethyl (Pse) group as carboxyterminal protection. After complete deprotection with 1 M methanesulphonic acid in trifluoroacetic acid--thioanisol--m-cresol mixture the peptides were purified by reversed-phase chromatography. The studies of interaction of the peptides with rabbit antiserum against IFN-alpha 2 revealed at least one minor antigenic determinant within the 124-144 region of IFN-alpha 2 amino acid sequence. Rabbit antisera developed against peptides 124-138 and 129-144 showed ability of binding recombinant IFN-alpha 2 and neutralizing its antiviral activity. Free peptides or their conjugates with bovine serum albumine did not display antiviral activity, neither could they inhibit the activity of IFN-alpha 2.