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The safety and toxicokinetics of SCH 721015, an adenovirus encoding the human interferon alpha-2b gene, and Syn3 (SCH 209702), a novel excipient, were assessed in cynomolgus monkeys administered intravesical doses of 2.5 × 10E11 or 1.25 × 10E13 particles SCH 721015 in 25 mg Syn3 or 25 mg Syn3 alone on study days 1 and 91. There was no systemic toxicity. Monkeys dosed with SCH 721015 in Syn3 were positive for SCH 721015-specific DNA in the urine for 2 to 3 days following each dose and had interferon alpha-2b protein in the urine for 1-3 days after a single dose and in fewer animals after a second dose. Intracystic administration was associated with inflammation and focal/multifocal ulceration in the urinary bladder and irritation in the ureters and urethra at necropsy. The physical trauma from catheterization and filling/emptying of the bladder was likely a contributing factor and Syn3 exacerbated the trauma. There was nearly complete resolution of these findings 2 months after the last dose. The trauma to the bladder likely contributed to low, transient systemic exposure to Syn3, SCH 721015 and human interferon protein. The results of this study support the clinical investigation of SCH 721015 in Syn3.

Over the past several years we have obtained considerable evidence indicating that adenoviruses-expressing interferon α (Ad-IFNα) can overcome resistance to the IFNα protein itself. Since cancer cells infected with Ad-IFNα also show high perinuclear cytoplasmic IFNα expression, we were interested in whether endoplasmic reticulum (ER) stress and cleavage of caspase 4 could have a major role in Ad-IFNα-produced cancer cell death. Indeed, procaspase 4 was upregulated and cleaved as early as 12 h after Ad-IFNα infection of the cancer cells, which co-localized with IFNα staining and ER tracker. In contrast, immortalized normal human urothelial cells, although exhibiting similar perinuclear IFNα staining, showed no cleaved caspase 4. Caspase 4 cleavage was not blocked by the caspase 8 specific inhibitor zIETD, indicating that caspase 4 activation was independent of caspase 8 activation. Blocking caspase 4 also inhibited activation of caspase 3 in Ad-IFNα containing cells. Finally, the cleaved form of caspase 4 (p10) was detected in Ad-IFNα-positive cancer cells from the urine of a patient following intravesical Ad-IFNα/Syn3 treatment. Therefore, ER stress and activation of caspase 4 appears to be an important mechanism involved in the direct cancer cell death produced by Ad-IFNα and also occurs in the clinical setting.

There is a need to improve the treatment of superficial bladder cancer. One area which holds promise is intravesical gene therapy. Recently, studies undertaken by us have shown that marked tumor regression of bladder cancers occurred after two daily intravesical administrations of an adenovirus encoding human interferon alpha (Ad-IFNalpha) using a mouse superficial bladder cancer model in which human bladder tumors are growing. A dose of 1 x 10(11) particles/ml (P/ml) was used along with 1 mg/ml of Syn3, a gene transfer-enhancing agent. Since clinical studies are being planned using this approach, it became critical to determine if one exposure and lower particle number could be equally effective. We report that indeed a single dose of Ad-IFNalpha in Syn3 at doses of 1 x 10(10)-1 x 10(11) P/ml is highly effective in reducing the size of the tumors, whereas 1 x 10(9) P/ml was not. Efficacy was also correlated with the level of IFN produced in the urine after treatment. Based on the results of the present studies, a Phase I trial is being planned for superficial bladder cancer, which will involve a single initial treatment with Ad-IFNalpha/Syn3 and measurement of IFN in the urine over time as an indicator of adequate gene transfer and expression.