A safety evaluation of DAS181, a sialidase fusion protein, in rodents.

DAS181 is a novel inhaled drug candidate blocking influenza virus (IFV) and parainfluenza virus (PIV) infections through removal of sialic acid receptors from epithelial surface of the respiratory tract. To support clinical development, a 28-day Good Laboratory Practices inhalation toxicology study was conducted in Sprague-Dawley rats. In this study, achieved average daily doses based on exposure concentrations were 0.47, 0.90, 1.55, and 3.00 mg/kg/day of DAS181 in a dry powder formulation. DAS181 was well tolerated at all dose levels, and there were no significant toxicological findings. DAS181 administration did not affect animal body weight, food consumption, clinical signs, ophthalmology, respiratory parameters, or organ weight. Gross pathology evaluations were unremarkable. Histological examination of the lungs was devoid of pulmonary tissue damage, and findings were limited to mild and transient changes indicative of exposure and clearance of a foreign protein. DAS181 did not show any cytotoxic effects on human and animal primary cells, including hepatocytes, skeletal muscle cells, osteoblasts, or respiratory epithelial cells. DAS181 did not cause direct or indirect hemolysis. A laboratory abnormality observed in the 28-day toxicology study was mild and transient anemia in male rats at the 3.00 mg/kg dose, which is an expected outcome of enhanced clearance of desialylated red blood cells resulting from systemic exposure with DAS181. Another laboratory observation was a transient dose-dependent elevation in alkaline phosphatase (ALP), which can be attributed to reduced ALP clearance resulting from increased protein desialylation due to DAS181 systemic exposure. These laboratory parameters returned to normal at the end of the recovery period.

CD10 is a key enzyme involved in the activation of tumor-activated peptide prodrug CPI-0004Na and novel analogues: implications for the design of novel peptide prodrugs for the therapy of CD10+ tumors.

Traditional chemotherapeutic drugs are often restricted by severe side effects and lack of tumor specificity. Peptide prodrugs cleavable by peptidases present in the tumor environment have been explored to improve the therapeutic index of cytotoxic drugs. One such prodrug of doxorubicin (Dox), CPI-0004Na [N-succinyl-beta-alanyl-L-leucyl-L-alanyl-L-leucyl-Dox (sALAL-Dox)] has been shown to have an improved antitumor efficacy profile with reduced toxicity compared with Dox in tumor xenograft models (V. Dubois et al., Cancer Res., 62: 2327-2331, 2002). In this study, we demonstrate that CD10, a cell surface metalloprotease expressed on a variety of tumor cell types, is capable of cleaving CPI-0004Na and related peptide prodrugs such as N-succinyl-beta-alanyl-L-isoleucyl-L-alanyl-L-leucyl-Dox (sAIAL-Dox). This proteolytic cleavage generates leucyl-Dox, which is capable of entering cells and generating intracellular Dox. In a [(3)H]thymidine proliferation assay, analogues of CPI-0004Na showed a 100-300-fold increase in potency on CD10(+) cells compared with CD10(-) cells. Cytotoxicity of CPI-0004Na was inhibited by phosphoramidon, a known inhibitor of CD10 enzymatic activity. Furthermore, Chinese hamster ovary CHO-S cells, which are resistant to CPI-0004Na, could be sensitized to the cytotoxic effect of the prodrug by transfection of a CD10 cDNA. Tumor xenograft studies using LNCaP prostate tumor cells support the important role of CD10 in the antitumor efficacy of these prodrugs against tumors expressing CD10. CPI-0004Na and sAIAL-Dox achieved statistically significant 70% tumor growth inhibition at day 22. CD10 is expressed on many types of human tumors including B-cell lymphoma, leukemia, and prostate, breast, colorectal, and lung carcinomas; therefore, CD10-cleavable prodrugs may be effective in a range of different tumor types.

CPI-0004Na, a new extracellularly tumor-activated prodrug of doxorubicin: in vivo toxicity, activity, and tissue distribution confirm tumor cell selectivity.

The search for cancer therapies that are more selective for tumor cells and spare normal sensitive cells has been very active for at least 20 years. The extracellularly tumor-activated peptidic prodrug of doxorubicin (Dox) CPI-0004Na (N-succinyl-beta-alanyl-L-leucyl-L-alanyl-L-leucyl-Dox) is potentially such a treatment. Here, we report the results of lethality studies performed with this compound in the mouse, showing that it is up to 4.6 times less toxic than Dox.HCl by the i.v. route and up to 16.2 times after i.p. administration. Pharmacokinetics and tissue distribution data indicate that this reduced toxicity is attributable to a lower uptake of Dox in normal tissues after treatment with CPI-0004Na than after the administration of an equimolar dose of Dox.HCl. For example, heart exposure to Dox is reduced >10-fold. Because of this reduced toxicity, higher doses of CPI-0004Na than of the parent drug could be used to treat nude mice bearing s.c. human breast (MCF-7/6) and colon (LS-174-T and CXF-280/10) tumors. In all three models, the prodrug showed a much improved efficacy as compared with Dox.HCl. Particularly, LS-174-T tumors that do not respond to Dox were inhibited by 68% after treatment with CPI-0004Na. Tissue distribution studies performed with MCF-7/6 tumor-bearing nude mice and comparing CPI-0004Na and Dox.HCl confirmed that the improved activity of the prodrug is actually the result of selective generation and uptake of Dox at the tumor site. Dox levels in tumor tissue were 2-fold higher after treatment with CPI-0004Na than after treatment with an equimolar dose of Dox.HCl, whereas normal tissue levels were reduced 1.4-29-fold.