Antiviral activity of CHO-SS cell-derived human omega interferon and other human interferons against HCV RNA replicons and related viruses.

The fully glycosylated human omega interferon produced from CHO-SS cells (glycosylated IFN-omega) has been shown to be well-tolerated in man and to induce a sustained virologic response in patients infected with hepatitis C virus (HCV). We examined the antiviral activity of glycosylated IFN-omega and various human IFNs (IFN-alpha, -beta, -gamma and non-glycosylated bacterial (Escherichia coli) recombinant IFN-omega (non-glycosylated IFN-omega)) against HCV RNA replicons and several viruses related to HCV. Since none of the IFNs displayed cytotoxicity we compared their activities based on the effective concentration of the IFN that inhibited virus growth by 50% (EC50). Glycosylated IFN-omega was found to be the most potent antiviral agent of all the IFNs tested against bovine viral diarrhea virus (BVDV), yellow fever virus and West Nile virus. With HCV RNA replicons, non-glycosylated IFN-omega was comparable in activity to IFN-alpha while glycosylated IFN-omega was markedly more potent, indicating that glycosylation has an important effect on its activity. Drug combination analysis of glycosylated IFN-omega+ribavirin (RBV) in BVDV showed a synergy of antiviral effects similar to IFN-alpha+RBV, as well as a unique antagonism of RBV cytotoxic effects by glycosylated IFN-omega. Transcription factor (TF) profiling indicated that IFN-alpha or glycosylated IFN-omega treatment upregulated the same 17 TFs. IFN-alpha and glycosylated IFN-omega also upregulated 9 and 40 additional unique TFs, respectively. The differences in the expression of these TFs were modest, but statistically significantly different for eight of the TFs that were upregulated exclusively by glycosylated IFN-omega. The activation of these additional TFs by glycosylated IFN-omega might contribute to its high potency.

Safety pharmacology, toxicology and pharmacokinetic assessment of recombinant human omega-interferon produced from CHO-SS cells.

Human omega-interferon (IFN-omega) has been shown to be well-tolerated in man and to induce reductions of hepatitis C virus RNA levels in a series of human clinical trials. Here we provide an overview of our preclinical safety evaluation of the fully-glycosylated human IFN-omega produced from CHO-SS cells that is currently being evaluated clinically. IFN-omega was not associated with any biologically-relevant adverse effects in a series of 10 safety pharmacology experiments, in the Ames mutagenicity test, in the micronucleus test, or in intraarterial, intravenous, paravenous or subcutaneous local tolerance studies. Acute, subacute, subchronic and reproductive toxicity studies performed in cynomolgus monkeys and rats showed a toxicity profile similar to that of human alpha interferon (IFN-alpha). Except for the acute (single-dose) toxicology study, all of the other toxicity studies showed evidence for the formation of anti-IFN-omega antibodies over time in the animals. These antibodies were found to neutralize IFN-omega antiviral activity in vitro in a dose-dependent manner. The average pharmacokinetic parameters following a single subcutaneous dose of IFN-omega in rabbits, rats and monkeys were determined and found to be similar to that of human IFN-alpha. These findings demonstrate that IFN-omega has a safety profile consistent with that required for its use in man. IFN-omega might be beneficial for the treatment of patients infected with hepatitis C virus who fail to respond to IFN-alpha or as a first-line treatment option.

Phase III, double-blind, controlled trial of atamestane plus toremifene compared with letrozole in postmenopausal women with advanced receptor-positive breast cancer.

PURPOSE: To compare time to progression (TTP) with a steroidal aromatase inhibitor (AI) atamestane (ATA) combined with toremifene (TOR; complete estrogen blockade) versus letrozole (LET) in receptor-positive advanced breast cancer (ABC). PATIENTS AND METHODS: Eligibility included postmenopausal receptor-positive ABC and adjuvant hormonal therapy completed more than 12 months prior to study entry. Participants received daily ATA 500 mg with TOR 60 mg (ATA + TOR), or letrozole 2.5 mg (LET). The primary end point was TTP, whereas secondary objectives included objective response (OR), overall survival (OS), and time to treatment failure (TTF). The study had 80% power to detect a 25% increase in TTP assuming a TTP of 9.4 months in the LET population. RESULTS: A total of 865 patients were randomly assigned (434 to ATA + TOR and 431 to LET) in 60 centers in the United States, Canada, Russia, and Ukraine. Baseline characteristics were balanced. Median TTP was identical in the two arms at 11.2 months (P < .92). Median TTF was similar at 9.24 months (ATA + TOR) versus 10.44 months (LET). The hazard ratios (LET/ATA + TOR) were 1.00 (95% CI, 0.92 to 1.08) for TTP, 0.99 (95% CI, 0.92 to 1.06) for TTF, and 0.98 (95% CI, 0.87 to 1.11) for OS. OR occurred in 30% of patients receiving ATA + TOR and in 36% of patients receiving LET (P < .1). Adverse events (AEs) were similar for patients receiving ATA + TOR versus LET, and serious AEs were 10% v 11%, respectively. CONCLUSION: TTP for patients receiving ATA + TOR was identical to that for patients receiving LET, representing the first endocrine therapy comparable to LET in ABC. Unlike in the Anastrozole, Tamoxifen, and Combined trial, addition of an antiestrogen did not decrease efficacy of the AI. Future studies of AIs in combination with more effective selective estrogen receptor modulators or selective receptor downregulators is warranted.