4-imino-1-3-diazabicyclo(3.1.0)hexan-2-one and Disease-Models--Animal

Imexon is an aziridine compound originally studied for immune-enhancing effects on lymphocytes. The drug was well-tolerated in humans and was shown to be active in a variety of animal tumor models. Recently, imexon has demonstrated antitumor activity in human multiple myeloma cell lines in vitro. The pharmacokinetics of the compound using normal phase HPLC assay were studied in normal mice and in dogs with mast cell tumors. Doses of 100 mg/kg given intraperitoneally produced peak plasma levels over 100 micrograms/ml in mice and the drug was rapidly eliminated with half lives of 8 minutes (alpha phase) and 29 minutes (beta phase). Only 20% of an oral imexon dose was absorbed in the mouse. In dogs, the alpha and beta phase half lives ranged from 18-26 minutes and 91-110 minutes, respectively. Peak levels over 100 micrograms/ml were obtained following intravenous doses of 12.5 mg/kg and 25 mg/kg. Imexon was active in mice bearing either P-388 or L-1210 leukemia, but not in mice with B-16 melanoma. These results suggest that cytotoxic drug concentrations can be obtained in vivo and that imexon is active in lymphoproliferative tumors.

Topics: Administration, Oral; Animals; Antineoplastic Agents; Biological Availability; Chromatography, High Pressure Liquid; Disease Models, Animal; Dogs; Dose-Response Relationship, Drug; Drugs, Investigational; Half-Life; Hexanones; Injections, Intraperitoneal; Injections, Intravenous; Leukemia L1210; Leukemia P388; Male; Mast-Cell Sarcoma; Melanoma, Experimental; Mice; Tumor Cells, Cultured

The effects of two immunomodulators were investigated in severe combined immunodeficient mice reconstituted with human peripheral blood lymphocytes (hu-PBL-SCID mice). Both immunomodulators, maleic anhydride divinyl ether (MVE-2) and 4-imino-1,3-diazobicyclo-(3.1.0)-hexan-2- one (imexon), have been previously studied by us in retrovirus-infected mice. To determine the effects of these compounds as they may function in humans, 24 SCID mice were each reconstituted with 20 x 10(6) ficoll-purified lymphocytes from a single donor. Five weeks after reconstitution, the mice received 16 mg/kg/day of MVE-2 intraperitoneally (i.p.) on days 0, 7, and 14 or 110 mg/kg/day of imexon i.p. daily for 14 days. Spleens were removed and splenocytes labeled with monoclonal antibodies for T- and B-cell enumeration as determined by flow cytometry 24 h after final treatment. Imexon-treated mice demonstrated a slight increase in total T cells and T cell subsets compared to control mice. T helper/T suppressor cell ratios in imexon-treated mice were brought to a normal 3:2 ratio compared to placebo-treated mice. Human immunoglobulin levels were markedly increased in imexon-treated mice. MVE-2-treated hu-PBL-SCID mice had significantly reduced numbers of total T cells compared to controls. The T-cell population results using human cells in SCID mice were similar to the effects of these immunomodulators on murine cells in immunologically competent mice.

Topics: Adjuvants, Immunologic; Animals; Antibodies, Monoclonal; B-Lymphocytes; Cell Count; Disease Models, Animal; Female; Flow Cytometry; Hexanones; Immunoglobulins; Injections, Intraperitoneal; Mice; Mice, SCID; Pyran Copolymer; Severe Combined Immunodeficiency; Spleen; T-Lymphocyte Subsets

Severe combined immune-deficient (SCID) mice accept human cell xenografts. SCID mice inoculated intraperitoneally with human peripheral blood mononuclear cells (PBMCs) from EBV-seropositive donors develop a form of disseminated human large cell lymphoma similar to that seen in transplant recipients and AIDS patients. Imexon (4-imino-1,4-diazobicyclo-3.1.0-hexan-2-one), a cyanoziridine immunomodulator with a selective inhibitory effect on B cells, was tested for its effect on this lymphoma development. Imexon started 2 weeks after PBMC inoculation significantly reduced the number of animals with lymphoma and the number of lymphomas sites per animal. The lymphoma was widely metastatic in the control animals but limited to the peritoneal cavity in the treated animals. Morphological and molecular parameters were used to confirm the reduced takes in the treated animals. Imexon was not myelosuppressive as determined by measurement of white blood cell counts. Imexon did not significantly suppress human IgG levels in the animals' serum. The tumor growth and lethality of human B lymphoblastoid cell lines in SCID mice was also suppressed by imexon treatment. A relatively nontoxic class of drugs that can suppress the development and/or growth of EBV-related lymphoma should be explored with priority for potential use in patients at high risk of this type of lymphoma.

Topics: Animals; Antineoplastic Agents; Disease Models, Animal; Herpesvirus 4, Human; Hexanones; Humans; Immunoglobulin G; Immunologic Factors; Injections, Intraperitoneal; Leukocyte Count; Lymphoma, Large B-Cell, Diffuse; Mice; Mice, SCID; Severe Combined Immunodeficiency; Tumor Cells, Cultured

The Rauscher murine leukemia retrovirus system provides an in vivo model of the human acquired immune deficiency syndrome for testing the ability of antiviral agents and biological response modifiers (BRM) to suppress viremia and retroviral disease. In the present report we examined three agents in the Rauscher retrovirus model: imexon, Ampligen and poly[I,C]-LC. Imexon reduced splenomegaly, viremia, and serum reverse transcriptase levels even when treatment was not initiated until 7 days after virus infection. Imexon also significantly prolonged the survival of infected mice. Thus it proved to be an effective antiviral agent in this system, although imexon did not completely eliminate retroviral infection in treated mice. Poly[I,C]-LC and Ampligen had immunomodulatory effects. Both of these BRM augmented the cytolytic activity of splenic natural killer (NK) cells in infected animals when treatment was initiated 24 h after infection. Poly[I,C]-LC had antiretroviral activity when administered on this schedule. In order to examine the role of NK cell augmentation in the antiviral activity of poly[I,C]-LC, we attempted to deplete NK activity by treatment with rabbit antibody to asialo GM1, a ganglioside on the surface of murine NK cells. Combined treatment of infected mice with poly[I,C]-LC and anti-asialo GM1 decreased the antiviral activity of poly[I,C]-LC. This finding suggests that NK cells may be involved in the antiviral effect of this BRM.

Topics: Acquired Immunodeficiency Syndrome; Animals; Disease Models, Animal; Female; Hexanones; Immunologic Factors; Killer Cells, Natural; Leukemia, Experimental; Mice; Mice, Inbred BALB C; Rauscher Virus

Topics: Acquired Immunodeficiency Syndrome; Animals; Antiviral Agents; Disease Models, Animal; Female; Hexanones; Immunologic Factors; Ketones; Leukemia, Experimental; Mice; Mice, Inbred BALB C; Rauscher Virus; Retroviridae Infections; Reverse Transcriptase Inhibitors; Splenomegaly; Viremia