Prevention of oncogenic viral infections in mice with CGP 11637, a synthetic muramyl dipeptide analog

Critical Review of Preclinical Approaches to Evaluate the Potential of Immunosuppressive Drugs to Influence Human Neoplasia

Many immunosuppressive drugs are associated with an increased risk of B-cell lymphoma, squamous cell carcinoma, and Kaposi sarcoma. Thirteen immunosuppressive drugs have been tested in 2-year carcinogenicity studies (abatacept; azathioprine; busulfan; cyclophosphamide; cyclosporine; dexamethasone; everolimus; leflunomide; methotrexate; mycophenolate mofetil; prednisone; sirolimus; and tacrolimus) and in additional models including neonatal and genetically modified mice; chemical, viral, ultraviolet, and ionizing radiation co-carcinogenesis, and in models with transplanted tumor cells. The purpose of this review is to outline the mechanisms by which immunosuppressive drugs can influence neoplasia, to summarize the available preclinical data on the 13 drugs, and to critically review the performance of the models. A combination of primary tumor and metastasis assays conducted with transplanted cells may provide the highest value for hazard identification and can be applied on a case-by-case basis. However, for both small molecules and therapeutic proteins, determining the relative risk to patients from preclinical data remains problematic. Classifying immunosuppressive drugs based on their mechanism of action and hazard identification from preclinical studies and a prospective pharmacovigilance program to monitor carcinogenic risk may be a feasible way to manage patient safety during the clinical development program and postmarketing.

Enhancement of host resistance against virus infections by MTP-PE, a synthetic lipophilic muramyl peptide--I. Increased survival in mice and guinea pigs after single drug administration prior to infection, and the effect of MTP-PE on interferon levels in sera and lungs

Muramyl tripeptide-phosphatidylethanolamine (MTP-PE, CGP 19835) displays prophylactic antiviral activity in mice infected with influenza viruses A and B, parainfluenza 1 virus or herpes simplex type 1 viruses (HSV/1) and in guinea pigs infected with herpes simplex type 2 viruses (HSV/2). MTP-PE is effective when given in a single intranasal dose as early as 1-4 weeks before infection. In the case of HSV/2 infections, prophylactic effectiveness can be demonstrated after a single topical application into the vagina seven days before infection. Antiviral effects are observed in response to doses as little as 0.001 mg/kg bodyweight. The activity of the substance seems to be inversely related to the size of the viral inoculum, but poor dose-effect relation is demonstrable in a dose-range extending over four to five orders of magnitude. Furthermore, the compound is devoid of antiviral effects in vitro. MTP-PE does not induce interferon (IFN) in serum and lung, nor does it influence kinetics or quantity of serum and lung IFN content in the course of viral infections. However, when given intranasally 7 days before an oral dose of tilorone, increased levels of IFN in lung suspensions are observed.