Enhanced Plasma Concentration by Selective Deuteration of Rofecoxib in Rats

The plasma concentrations of BDD-11602 (4-[4- (methanesulfonyl)phenyl]-3-(pentadeuterophenyl)-5H-furan-2-one), a rofecoxib derivative in which the positions 2',3;4',5' and 6' of the phenyl ring were deuterated, and rofecoxib (4-(4-methylsulfonylphenyl)-3-phenyl-5H-furan-2-one, CAS 162011-90-7) were compared in order to explore the effects of selective deuteration on the systemic availability. The COX-2 selectivity in vitro was also compared. Following oral gavage administration of 0.1, 1 or 10 mg/kg BDD-11602 to Sprague Dawley rats, AUCo-t, (area under the curve) and Cmax (maximum concentration) values were statistically significant higher than those of rofecoxib at the same doses. The overall increase in AUC0-t and Cmax for BDD-11602 over rofecoxib was 1.53-fold and 1.60-fold, respectively. BDD-11602 and rofecoxib inhibited COX-2-derived PGE(2) synthesis with IC50 values of 173 nmol/l and 169 nmol/l, respectively. IC50 values for inhibition of human platelet COX-1 were estimated to be above 1 micromol/l for both compounds. The substitution of hydrogen by deuterium on the positions 2: 3',4',5' and 6' in BDD-11602 leads to superior oral availability compared to the non-deuterated compound, whereas the COX-2 selectivity is not affected.

Changed Phosphodiesterase Selectivity and Enhanced in vitro Efficacy by Selective Deuteration of Sildenafil

In order to explore whether selective deuteration of sildenafil affects selectivity and efficacy of the drug, the inhibitory activity of sildenafil (1-[4-ethoxy-3-(6,7-dihydro-1-methyl-7-oxo-3-propyl-1H-pyrazolo[4,3-d]pyrimidin-5-yl)phenyl-sulfonyl] -4-methylpiperazine citrate, CAS 139755-83-2) and three deuterated sildenafil derivatives, D8-piperazine-sildenafil (BDD-10402), D3-methyl-D8-piperazine-sildenafil (BDD-10403) and D5-ethoxy-Sildenafil (BDD-10406) against phosphodiesterases 1-6 was compared. Furthermore, the relaxant effect of sildenafil and its deuterated derivatives in a contractility assay on rabbit corpus cavernosum strips from New Zealand rabbits was investigated. BDD-10406 exhibits a 2-fold higher selectivity for phosphodiesterase 5 versus phosphodiesterase 6 than sildenafil. BDD-10406 and sildenafil inhibited cGMP formation with IC50 values of 6 nmol/L and 9 nmol/L, respectively. The corresponding IC80 values for BDD-10406 and Sildenafil were 33 nmol/L and 40 nmol/L, respectively. Sildenafil, BDD-10402, BDD-10403 and BDD-10406 relaxed the rabbit corpus cavernosum strips in a dose-dependent manner with ED50 values of 245 nmol/L, 91 nmol/L, 121 nmol/L and 85 nmol/L, respectively. Deuteration of sildenafil on the ethoxy group (BDD-10406) leads to enhanced selectivity for phosphodiesterase 5 versus phosphodiesterase 6 and higher efficacy in vitro. This is the first example of a deuteration effect on the inhibitory activity of a reversible enzyme inhibitor.

High-efficiency system for the construction of adenovirus vectors and its application to the generation of representative adenovirus-based cDNA expression libraries

We here describe a convenient system for the production of recombinant adenovirus vectors and its use for the construction of a representative adenovirus-based cDNA expression library. The system is based on direct site-specific insertion of transgene cassettes into a replicating donor virus. The transgene is inserted into a donor plasmid containing the viral 5' inverted terminal repeat, the complete viral packaging signal, and a single loxP site. The plasmid is then transfected into a Cre recombinase-expressing packaging cell line that has been infected with a donor virus containing a partially deleted packaging signal flanked by loxP sites. Cre recombinase, by two steps of action, sequentially catalyzes the generation of a nonpackageable donor virus acceptor substrate and the generation of the desired recombinant adenovirus vector. Due to its growth impairment, residual donor virus can efficiently be counterselected during amplification of the recombinant adenovirus vector. By using this adenovirus construction system, a plasmid-based human liver cDNA library was converted by a single step into an adenovirus-based cDNA expression library with about 10(6) independent adenovirus clones. The high-titer purified library was shown to contain about 44% of full-length cDNAs with an average insert size of 1.3 kb. cDNAs of a gene expressed at a high level (human alpha(1)-antitrypsin) and a gene expressed at a relatively low level (human coagulation factor IX) in human liver were isolated from the adenovirus-based library using an enzyme-linked immunosorbent assay-based screening procedure.

Construction, rescue, and characterization of vectors derived from ovine atadenovirus

Gene transfer vectors derived from ovine atadenovirus type 7 (OAdV) can efficiently infect a variety of mammalian cells in vitro and in vivo to deliver and express transgenes. However, early OAdV vectors were designed on human mastadenovirus principles prior to the complete characterization of OAdV genes and transcripts. The distinctive arrangement of the OAdV genome has suggested ways to improve OAdV vector design and utility. We therefore developed a cosmid-based approach that allows efficient construction of recombinant ovine atadenovirus genomes in which the transgene is inserted at one of three sites. Viruses were rescued by transfection of viral DNA into a new ovine fetal skin fibroblast producer cell line, HVO156. The suitability of the three insertion sites was compared with respect to virus rescue efficiency, gene expression levels, and genetic stability of the vectors. We found that one vector with a transgene inserted at site 1, between the pVIII and fiber genes, was unstable. Only one vector that carried a transgene at site 2, near the right end of the genome, together with a nearby deletion was rescued. In contrast, several vectors with different transgenes inserted in site 3, between the E4 and RH transcription units, were repeatedly rescued, and these vectors were stable over at least four passages. Transgene orientation in site 3 had only little effect on expression. Finally, a vector carrying a human factor IX cDNA at site 3, when administered intravenously, produced nearly physiological levels of human factor IX in mice. The availability of an efficient method for vector construction and the identification of a new insertion site for virus rescue and gene expression substantially enhance the utility of the OAdV vector system.

Advances in the development of non-human viral DNA-vectors for gene delivery

Within the last two decades, various vectors based on human viruses have been developed as gene transfer vehicles for gene therapy applications and vaccination. However, one yet unresolved problem connected to the use of viral vectors in humans is the pre-existing immunity to most of these vectors in the vast majority of the population which can result in impaired gene transfer efficiency and increased secondary toxicity. One approach to solve this problem is the development of recombinant viruses of non-human origin as vectors for gene transfer. The major rationale for using such vectors is the avoidance of vector neutralization by pre-existing antibodies directed against the virus on which the vector is based. Use of vectors based on non-human viruses may therefore allow the use of lower initial vector doses to achieve efficient gene transfer. Side-effects caused by interactions between vectors derived from human viruses with a primed immune system or with blood components could also be reduced. Furthermore, these vectors might show new cell type tropisms and could therefore infect tissue and organs that are not accessible to current viral vectors. This review outlines some of the problems inherent in the human origin of current viral vectors and describes features and progress with non-human adenovirus and baculovirus-derived vectors that may provide alternatives.

Chromosomal integration pattern of a helper-dependent minimal adenovirus vector with a selectable marker inserted into a 27.4-kilobase genomic stuffer

Helper-dependent minimal adenovirus vectors are promising tools for gene transfer and therapy because of their high capacity and the absence of immunostimulatory or cytotoxic viral genes. In order to characterize this new vector system with respect to its integrative properties, the integration pattern of a minimal adenovirus vector with a neo(r) gene inserted centrally into a noncoding 27.4-kb genomic stuffer element derived from the human X chromosome after infection of a sex chromosome aneuploid (X0) human glioblastoma cell line was studied. Our results indicate that even extensive homologies and abundant chromosomal repeat elements present in the vector did not lead to integration of the vector via homologous or homology-mediated mechanisms. Instead, integration occurred primarily by insertion of a monomer with no or little loss of sequences at the vector ends, apparently at random sites, which is very similar to E1 deletion adenovirus vectors. It is therefore unlikely that the incorporation of stuffer elements derived from human genomic DNA, which were shown to allow long-term transgene expression in vivo in a number of studies, leads to an enhanced risk of insertional mutagenesis. Furthermore, our findings indicate that the potential of minimal adenovirus vectors as tools for targeted insertion and gene targeting is limited despite the possibility of incorporating long stretches of homologous sequences. However, we found an enhanced efficiency of stable neo(r) transduction of the minimal adenovirus vector compared to an E1 deletion adenovirus vector, possibly caused by the absence of potential growth-inhibitory viral genes. Complete integration of the vector and tolerance of the integrated vector sequences by the cell might indicate a potential use of these vectors as tools for stable transfer of (large) genes.

System for efficient helper-dependent minimal adenovirus construction and rescue

Helper-dependent minimal adenoviral vectors deleted for all viral coding sequences are promising vectors for gene therapy. They retain only the adenovirus cis elements for replication and packaging, can accommodate up to 36 kb of foreign DNA, and exhibit prolonged transgene expression and reduced tissue toxicity as compared with first-generation adenoviral vectors. We have developed a system consisting of a set of cosmid cloning vectors (pMV and pMVX) for simple routine construction and efficient rescue of minimal adenoviral vectors. In the cloning vectors the inverted terminal repeats (ITRs) are flanked by recognition sites for the super rare-cutting endonuclease I-SceI. This allows the release of linear minimal adenovirus genomes for rescue of minimal adenovirus regardless of the sequence of the insert DNA. pMV contains a multiple cloning site for the insertion of 26 to 36 kb of therapeutic DNA. pMVX contains a noncoding human X-chromosomal DNA fragment as a vector backbone, which provides endonuclease restriction sites that allow for complete or partial replacement of the vector backbone by 1 to 26 kb of therapeutic DNA sequences, while retaining a packageable final minimal adenovirus genome size between 27 and 37.5 kb. Both vectors exist in two forms, with or without an Escherichia coli lacZ reporter gene cassette. Several minimal adenoviral vectors with insert sizes ranging from 1.5 to 16 kb were constructed with these cloning vectors. Minimal adenoviruses were efficiently rescued and amplified to high titers, using a Cre/lox-based helper system. Vectors containing the X-chromosomal backbone were stable during amplification. This simple and efficient system facilitates the construction of minimal adenoviruses and should be useful for further improvement of these new vectors.

Ovine adenovirus vectors mediate efficient gene transfer to skeletal muscle

Ovine adenovirus (OAV) vectors represent a promising tool for human gene therapy since these vectors overcome the problem of pre-existing immunity against human adenovirus vectors. In this report we investigated the in vivo characteristics of this novel vector system with respect to its potential for gene transfer into skeletal muscle. We found that moderate doses of an OAV-derived vector expressing the human alpha1-antitrypsin gene (OAVhaat) infected skeletal muscle in mice very efficiently resulting in high serum hAAT levels. The infection was restricted to skeletal muscle, but gene expression was transient and vector DNA was rapidly cleared. Vector clearance was also observed with a vector that lacked the transgene. The loss of vector DNA was accompanied by a cellular immune response in the infected muscle but was not connected with detectable expression of early or late genes of the viral backbone as analyzed by RT-PCR. A very low dose of OAVhaat (3x 10(7) infectious particles) was sufficient to produce reasonable amounts (>100 ng/ml) of serum hAAT, and this was accompanied by a weak immune response to the vector. Under these conditions, a second intramuscular injection of the same recombinant OAV vector was successful. Our study expands the known tissue tropism of OAV-derived vectors in vivo and points to the possible utility of the vector for muscle gene transfer and vaccination.

Enhanced sensitivity of small cell lung cancer cell lines to cisplatin and etoposide after infection with adeno-associated virus type 2

In previous studies we have reported the sensitisation of human tumour cells to gamma irradiation and chemotherapeutic drugs upon infection with the human non-pathogenic adeno-associated virus type 2 (AAV-2) in vitro and in vivo. Treatment of small cell lung cancer (SCLC) is consistently hampered by relapses due to the selection of chemotherapy-resistant cell clones. Hence, we were interested to test whether selection of chemotherapy-resistant SCLC cells might be reduced or even prevented if chemotherapy is applied in combination with AAV-2 infection. In vitro proliferation assays indicated that the number of proliferating cells, after combined treatment with cisplatin and etoposide, can be significantly reduced by concomitant AAV-2 infection, as compared with treated but non-infected controls. H446 SCLC cells, which show resistance to etoposide/cisplatin chemotherapy (compared with a cell line which was never chemotherapeutically treated before, like NCI-H209) were significantly more sensitive after AAV-2 infection, suggesting that the therapeutic efficacy of chemotherapy in SCLC can be enhanced even if the cells are already relatively resistant to chemotherapy. Similarly, in vivo growth of tumours induced by inoculation of SCLC cells into immunocompromised nude mice was reduced more efficiently in AAV-2-infected animals compared with tumours in mice treated with chemotherapeutic drugs alone. These data extend and further support our previous reports on AAV functions which might be useful in improving the efficacy of chemotherapeutic drugs used in human cancer treatment.