Janis Upeslacis

Novel Nonnucleoside Inhibitor of Hepatitis C Virus RNA-Dependent RNA Polymerase

ABSTRACT A novel nonnucleoside inhibitor of hepatitis C virus (HCV) RNA-dependent RNA polymerase (RdRp), [(1R)-5-cyano-8-methyl-1-propyl-1,3,4,9-tetrahydropyano[3,4-b]indol-1-yl] acetic acid (HCV-371), was discovered through high-throughput screening followed by chemical optimization. HCV-371 displayed broad inhibitory activities against the NS5B RdRp enzyme, with 50% inhibitory concentrations ranging from 0.3 to 1.8 μM for 90% of the isolates derived from HCV genotypes 1a, 1b, and 3a. HCV-371 showed no inhibitory activity against a panel of human polymerases, including mitochondrial DNA polymerase gamma, and other unrelated viral polymerases, demonstrating its specificity for the HCV polymerase. A single administration of HCV-371 to cells containing the HCV subgenomic replicon for 3 days resulted in a dose-dependent reduction of the steady-state levels of viral RNA and protein. Multiple treatments with HCV-371 for 16 days led to a >3-log10 reduction in the HCV RNA level. In comparison, multiple treatments with a similar inhibitory dose of alpha interferon resulted in a 2-log10 reduction of the viral RNA level. In addition, treatment of cells with a combination of HCV-371 and pegylated alpha interferon resulted in an additive antiviral activity. Within the effective antiviral concentrations of HCV-371, there was no effect on cell viability and metabolism. The intracellular antiviral specificity of HCV-371 was demonstrated by its lack of activity in cells infected with several DNA or RNA viruses. Fluorescence binding studies show that HCV-371 binds the NS5B with an apparent dissociation constant of 150 nM, leading to high selectivity and lack of cytotoxicity in the antiviral assays.

Chapter 16. Angiogenesis Inhibitors

Publisher Summary The evidence that inhibiting angiogenesis have a positive effect on controlling solid tumors has increased dramatically. However, as the various biological factors that promote or inhibit this process are identified, It is evident that angiogenesis may be difficult to control and no single target is fundamental over the rest. Angiogenesis is required for the development of many proliferative diseases, including rheumatoid arthritis, psoriasis, solid tumor growth, metastasis, as well as diabetic retinopathy and age related macular degeneration. At least, 20 endogenous factors have been identified so far that either promote or inhibit angiogenesis. This chapter discusses those factors that may be useful as targets for therapy. The chapter discusses the oncology aspects of anti-angiogenesis research because most of the effort in recent times has been spent there, even though several models for assessing anti-angiogenic effects for oncology involve testing in eye models. For cancer, the inhibition of angiogenesis is a departure from the traditional therapy. In that, it attempts to inhibit the process, whereby a tumor recruits its own microvasculature to gain nutrients and rid itself of cellular by-products rather than attempting to kill the tumor itself. Thus, anti-angiogenic therapy should be viewed as cytostatic rather than cytotoxic and drugs that inhibit angiogenesis may need to be administered in conjunction with traditional anti-cancer agents.

Chapter 16. Chemical Modification of Antibodies for Cancer Chemotherapy

Publisher Summary This chapter discusses the chemistry behind conjugation of agents to MoAbs. Recent reviews dealing with other aspects of MoAb-based therapy have appeared, covering subjects, such as the generation of hybridomas, the various tumor-associated antigens, and the problems inherent in MoAb-based approaches to tumor therapy, and clinical experiences with MoAbs and their conjugates. Modifications at more specific sites have involved cysteine residues or carbohydrate chains. Several recent reviews have dealt with the restrictions placed on useful conjugation reactions because of the nature of MoAbs. Briefly, all methods of activating agents for conjugation must yield intermediates that are stable to, but reactive, under aqueous conditions. Although maximum loadings achieved by a particular method are cited, such loadings differ from one MoAb to the next, and often reflect a point, at which immunoreactivity was lost upon further loading. Because direct conjugation of MTX to some MoAbs leads to the precipitation of the product after as little as two or three molecules of MTX have been conjugated, human serum albumin (HSA) has been used extensively as an intermediate carrier for MTX-MoAb conjugates. HSA contains numerous amino groups for amide formation and solubilization is relatively small (-65,000 M W) and contains a cysteine at residue 34 that makes the complex amenable to later attachment to a MoAb. Cobra venom factor (CVF), a 140,000 MW functional analog of complement C 3 /C 5 convertase, has been attached to several MoAbs in an effort to achieve cytotoxicity by complement fixation. A number of hetero-bifunctional cross-linking reagents were evaluated for their potential as spacers between CVF and MoAbs, including 4-(N-maleimidomethyl)cyclohexanecarboxyl N-hydroxysuccinimide, γ-(N-maleimidobutyryl) N-hydroxysuccinimide, MBS, SPDP, and iodoacetyl N-hydroxysuccinimide.

Chapter 14 Anti-neoplastic Agents

Publisher Summary Although the primary thrust of this chapter is to highlight the agents that act directly on tumor cells, other, more subtle areas of cancer research are evolving. The biochemical basis for cell differentiation has been discussed in the chapter, as well as the potential for chemotherapy with this approach. Retinoids, as anti-proliferative agents and inducers of differentiation and the early clinical experience with hexamethylene bisacetamide, have been discussed in the chapter. The biochemical rationale behind metastatic invasiveness is being elucidated. As knowledge of the process builds, drugs that hold promise as anti-metastatic agents are evolving. Two recombinant alpha-interferons have been granted food and drug administration (FDA) approval for clinical use against hairy cell leukemia. Numerous clinical trials for use of other interferons against cancer are in progress. Human trials are reported that used IL-2-activated autologous lymphocytes as well as high-dose IL-2 itself. Although objective responses are observed in both trials, the treatment is not without its critics because of its high cost and toxic side-effects. Tumor necrosis factor is also discussed in this chapter. As more monoclonal antibodies are developed that recognize tumor-associated antigens, the potential for passive immunotherapy increases, as does the possibility of active immunotherapy, either by vaccination with tumor antigens or through anti-ideotype responses.