The clinical use of tumor necrosis factor alpha (TNF) as an anticancer drug is limited to local treatments because of its dose-limiting systemic toxicity. We show here that murine TNF fused with CNGRC peptide (NGR-TNF), an aminopeptidase N (CD13) ligand that targets activated blood vessels in tumors, is 12-15 times more efficient than murine TNF in decreasing the tumor burden in lymphoma and melanoma animal models, whereas its toxicity is similar. Similarly, human NGR-TNF induced stronger antitumor effects than human TNF, even with 30 times lower doses. Coadministration of murine NGR-TNF with a CNGRC peptide or an anti-CD13 antibody markedly decreased its antitumor effects. Tumor regression, induced by doses of murine NGR-TNF lower than the LD50, was accompanied by protective immunity. In contrast, no cure was induced by TNF at any dose. These results suggest that targeted delivery of TNF to CD13 may enhance its immunotherapeutic properties. Moreover, these findings reveal the potential of tumor homing peptides to generate a new class of recombinant cytokines that compared to immunocytokines have a simpler structure, could be easier to produce and are potentially less immunogenic.

Drug delivery and penetration into neoplastic cells distant from tumor vessels are critical for the effectiveness of solid-tumor chemotherapy. We have found that targeted delivery to tumor vessels of picogram doses of TNF-α (TNF), a cytokine able to alter endothelial barrier function and tumor interstitial pressure, enhances the penetration of doxorubicin in tumors in murine models. Vascular targeting was achieved by coupling TNF with CNGRC, a peptide that targets the tumor neovasculature. This treatment enhanced eight-to tenfold the therapeutic efficacy of doxorubicin, with no evidence of increased toxicity. Similarly, vascular targeting enhanced the efficacy of melphalan, a different chemotherapeutic drug. Synergy with chemotherapy was observed with 3-5 ng/kg of targeted TNF (intraperitoneally), about 10 6-fold lower than the LD 50 and 10 5-fold lower than the dose required for nontargeted TNF. In addition, we have also found that targeted delivery of low doses of TNF to tumor vessels does not induce the release of soluble TNF receptors into the circulation. The delivery of minute amounts of TNF to tumor vessels represents a new approach for avoiding negative feedback mechanisms and preserving its ability to alter drug-penetration barriers. Vascular targeting could be a novel strategy for increasing the therapeutic index of chemotherapeutic drugs.

Cyclic and linear peptides containing the Asn-Gly-Arg (NGR) motif have proven useful for delivering various anti-tumor compounds and viral particles to tumor vessels. We have investigated the role of cyclic constraints on the structure and tumor-homing properties of NGR peptides using tumor necrosis factor-␣ (TNF) derivatives containing disulfide-bridged (CNGRC-TNF) and linear (GNGRG-TNF) NGR domains. Experiments carried out in animal models showed that both GNGRG and CNGRC can target TNF to tumors. However, the antitumor activity of CNGRC-TNF was >10-fold higher than that of GNGRG-TNF. Molecular dynamic simulation of cyclic CNGRC showed the presence of a bend geometry involving residues Gly 3 -Arg 4 . Molecular dynamic simulation of the same peptide without disulfide constraints showed that the most populated and thermodynamically favored configuration is characterized by the presence of a ␤-turn involving residues Gly 3 -Arg 4 and hydrogen bonding interactions between the backbone atoms of Asn 2 and Cys 5 . These results suggest that the NGR motif has a strong propensity to form ␤-turn in linear peptides and may explain the finding that GNGRG peptide can target TNF to tumors, albeit to a lower extent than CNGRC. The disulfide bridge constraint is critical for stabilizing the bent conformation and for increasing the tumor targeting efficiency.Phage display peptide libraries are commonly used to obtain peptide sequences interacting with proteins differentially expressed in normal and pathological tissues (1, 2). For instance, in vivo panning of phage libraries in tumor-bearing animals have proven useful for selecting peptides able to interact with proteins expressed within tumor-associated vessels and to home to neoplastic tissues (3). Among the various tumor targeting ligands identified so far, the CNGRC peptide have proven useful for delivering various anti-tumor compounds, like chemotherapeutic drugs, apoptotic peptides and cytokines, to tumor vessels (3-5). For example, we have recently shown that targeted delivery of tumor necrosis factor-␣ (TNF) 1 to tumor vasculature can be obtained by coupling its N terminus to the C terminus of the CNGRC peptide, by genetic engineering technology (5). This approach markedly improved the therapeutic index of TNF in animal models, either when used alone (5) or in combination with chemotherapeutic agents (6). Studies on the mechanism of action showed that the targeting domain of this TNF derivative (called NGR-TNF) binds an aminopeptidase (CD13) isoform expressed in tumor vessels, and not other isoforms expressed in normal epithelia or myeloid cells (7). Besides CNGRC, other tumor vasculature targeting peptides containing the NGR motif have been identified, such as linear NGRAHA and cyclic CVLNGRMEC (3). These and other linear and cyclic NGR peptides have been used for targeting viral particles to endothelial cells (8, 9). Although these findings may suggest that peptide cyclization is not necessary for the targeting properties of NGR peptides, the role of cysteines and th...

The conclusions of EFSA following the peer review of the initial risk assessment carried out by the competent authority of the rapporteur Member State, the United Kingdom, for the pesticide risk assessment for the triazole derivative metabolites are reported. The context of the peer review was that requested by the European Commission following the submission and evaluation of confirmatory data in relation to mammalian toxicology, metabolism and residue data. The conclusions were reached on the basis of the evaluation of various uses for a number of triazole fungicides. Recommendations are proposed. Missing information identified as being required by the regulatory framework is listed. Concerns are identified.

Purpose: Subnanogram doses of NGR-tumor necrosis factor (TNF), a TNF-α derivative able to target tumor neovessels, can enhance the antitumor activity of doxorubicin and melphalan in murine models. We have examined the antitumor activity of NGR-TNF in combination with various chemotherapeutic drugs acting via different mechanisms, including, besides doxorubicin and melphalan, cisplatin, paclitaxel, and gemcitabine. Experimental Design: Chemotherapeutic drugs were tested alone and in combination with NGR-TNF (0.1 ng) in murine lymphoma, fibrosarcoma, and mammary adenocarcinoma models. Different administration schedules have been tested and the effects on tumor growth, animal weight, tumor perfusion, and cell cytotoxicity have been investigated. Results: Pretreatment with NGR-TNF enhanced the response to all these drugs although to a different extent. The increased efficacy was not accompanied by increased toxicity at least as judged from the loss of animal weight. The synergistic effect was transient, maximal synergism being observed with a 2-hour delay between NGR-TNF and drug administrations in all models and with all drugs tested. NGR-TNF did not increase the in vitro cytotoxicity of chemotherapeutic drugs against tumor cells, suggesting that the in vivo synergism depends on NGR-TNF effects on host cells rather than on tumor cells. Conclusions: Targeted delivery of low doses of NGR-TNF to the tumor vasculature can increase the efficacy of various drugs acting via different mechanisms. Optimal administration schedule requires 2 hours of pretreatment with NGR-TNF independently from the mechanism of drug cytotoxicity. This work could provide important information for designing clinical studies with NGR-TNF in combination with chemotherapeutic drugs.