Acadesine, also known as 5-aminoimidazole-4-carboxamide-1-β-D-ribofuranoside, AICA-riboside, and AICAR, is an AMP-activated protein kinase activator which is used for the treatment of acute lymphoblastic leukemia (ALL) and may have applications in treating other disorders such as mantle cell lymphoma (MCL). The mechanism by which acadesine selectively kills B-cells is not yet fully elucidated. The action of acadesine does not require the tumour suppressor protein p53 like other treatments. This is important, as p53 is often missing or defective in cancerous B-cells. Studies have shown acadesine activates AMPK and induces apoptosis in B-cell chronic lymphocytic leukemia cells but not in T lymphocytes. Antiapoptotic proteins of the Bcl-2 family regulate MCL cell sensitivity to acadesine and combination of this agent with Bcl-2 inhibitors might be an interesting therapeutic option to treat MCL patients. Acadesine has anti-ischemic properties that is currently being studied (Phase 3) for the prevention of adverse cardiovascular outcomes in patients undergoing coronary artery bypass graft (CABG) surgery. Adenosine itself has many beneficial cardioprotective properties that may therefore be harnessed by this new class of drugs. Unlike adenosine, acadesine acts specifically at sites of ischemia and is therefore void of the systemic hemodynamic effects that may complicate adenosine therapy. Animal and in vitro studies have established acadesine as a promising new agent for attenuating ischemic and reperfusion damage to the myocardium. Acadesine also possesses the theoretical (but unproven) benefit of attenuating reperfusion injury after acute myocardial infarction (MI). Further research is needed to define the full potential of this unique agent in various clinical situations involving myocardial ischemia.

Raltitrexed belongs to a group of medicines known as antimetabolites. It is used to treat cancer of the colon and rectum. It may also be used to treat other kinds of cancer, as determined by your doctor. Raltitrexed blocks an enzyme needed by the cell to live. This interferes with the growth of cancer cells, which are eventually destroyed. Since the growth of normal body cells may also be affected by raltitrexed, other effects will also occur. Some of these may be serious and must be reported to your doctor. Other effects, like hair loss, may not be serious but may cause concern. Raltitrexed inhibits thymidylate synthase (TS) leading to DNA fragmentation and cell death. It is transported into cells via a reduced folate carrier. Inside the cell Raltitrexed is extensively polyglutamated, which enhances thymidylate synthase inhibitory power and duration. Inhibition of this enzyme results in decreased synthesis of thymidine triphosphate which is required for DNA synthesis. Raltitrexed is used for the treatment of malignant neoplasm of colon and rectum. Although raltitrexed is not approved by the US FDA, the drug was licensed in Canada and some European countries.

Tiazofurin (NSC-286193; 2-beta-D-ribofuranosylthiazole-4-carboxamide) an approved chronic myeloid leukemia (CML) drug, is converted by cellular enzymes into tiazofurin adenine dinucleotide, TAD, which inhibits the enzyme as a cofactor mimic. Resistance to tiazofurin is quickly developed due to diminished ability of resistant cells to synthesize TAD and increased enzymatic degradation of TAD. It is a nucleoside analog with oncolytic activity being developed by Ribapharm (formerly ICN Pharmaceuticals) as a potential treatment for leukemia. Ribapharm, through a Russian subsidiary of ICN, is planned to conduct phase II studies of tiazofurine involving patients suffering from advanced ovarian cancer or multiple myeloma which is resistant to conventional therapy.

ALANOSINE is an antiviral and antitumor antibiotic derived from Streptomyces alanosinicus. It inhibits adenylosuccinate synthetase, which converts inosine monophosphate into adenylosuccinate, an intermediate in purine metabolism. ALANOSINE-induced disruption of de novo purine biosynthesis is potentiated by methylthioadenosine phosphorylase (MTAP) deficiency. In cancer cells that lack MTAP, required in the salvage pathway, ALANOSINE should deprive such cells (but not normal cells) of de novo synthesized adenosine. However, in clinical trials, it was ineffective in patients with advanced MTAP-deficient tumors.

Uridine triacetate (formally PN401) is an acetylated prodrug of uridine. Following oral administration, uridine triacetate is deacetylated by nonspecific esterases present throughout the body, yielding uridine in the circulation. Uridine triacetate under VISTOGARD trade name is a uridine replacement agent approved for the emergency treatment of fluorouracil or capecitabine overdose (regardless of the presence of symptoms) or early-onset severe or life-threatening cardiac or central nervous system (CNS) toxicity and/or early-onset unusually severe adverse reactions (eg, gastrointestinal [GI] toxicity and/or neutropenia) within 96 hours following the end of fluorouracil or capecitabine administration in adult and pediatric patients. Uridine competitively inhibits cell damage and cell death caused by fluorouracil. Fluorouracil is a cytotoxic antimetabolite that interferes with nucleic acid metabolism in normal and cancer cells. Cells anabolize fluorouracil to the cytotoxic intermediates 5-fluoro-2’-deoxyuridine-5’- monophosphate (FdUMP) and 5-fluorouridine triphosphate (FUTP). FdUMP inhibits thymidylate synthase, blocking thymidine synthesis. Thymidine is required for DNA replication and repair. Uridine is not found in DNA. The second source of fluorouracil cytotoxicity is the incorporation of its metabolite, FUTP, into RNA. This incorporation of FUTP into RNA is proportional to systemic fluorouracil exposure. Excess circulating uridine derived from VISTOGARD is converted into uridine triphosphate (UTP), which competes with FUTP for incorporation into RNA. Uridine triacetate is also approved for the treatment of hereditary orotic aciduria under XURIDEN trade name. Uridine triacetate provides uridine in the systemic circulation of patients with hereditary orotic aciduria who cannot synthesize adequate quantities of uridine due to a genetic defect in uridine nucleotide synthesis.

Pemetrexed is a new-generation antifolate, approved for the treatment of mesothelioma and non-small cell lung cancer, currently being evaluated for the treatment of a variety of other solid tumors. Pemetrexed, is a folate analog metabolic inhibitor that exerts its action by disrupting folate-dependent metabolic processes essential for cell replication. In vitro studies have shown that pemetrexed inhibits thymidylate synthase (TS), dihydrofolate reductase (DHFR), glycinamide ribonucleotide formyltransferase (GARFT) and and to a lesser extent aminoimidazole carboxamide ribonucleotide formyltransferase (AICARFT), which are folate-dependent enzymes involved in the de novo biosynthesis of thymidine and purine nucleotides. Pemetrexed is taken into cells by membrane carriers such as the reduced folate carrier and membrane folate binding protein transport systems. Once in the cell, pemetrexed is converted to polyglutamate forms by the enzyme folylpolyglutamate synthetase. The polyglutamate forms are retained in cells and are inhibitors of TS and GARFT. Polyglutamation is a time- and concentration-dependent process that occurs in tumor cells and, is thought to occur to a lesser extent, in normal tissues. Polyglutamated metabolites are thought to have an increased intracellular half-life resulting in prolonged drug action in malignant cells.

Clofarabine is a anti-cancer drug which was approved by FDA for the treatment of pediatric patients with relapsed or refractory acute lymphoblastic leukemia. After crossing the cell membrane the drug is rapidly metabolized by deoxycytidine kinase to diphosphate and triphosphate metabolites and these metabolites reversibly inhibit hRNR by binding to alpha subunit. Also the triphosphate is incorporated to DNA where it acts as a chain terminator.

The potential antiviral effect of adefovir, an acyclic nucleoside phosphonate analog of 2′-deoxyadenosine monophosphate, was first studied by Holý and De Clercq in 1980s. Adefovir is an acyclic nucleotide analog of adenosine monophosphate which is phosphorylated to the active metabolite adefovir diphosphate by cellular kinases. Adefovir diphosphate inhibits HBV DNA polymerase (reverse transcriptase) by competing with the natural substrate deoxyadenosine triphosphate and by causing DNA chain termination after its incorporation into viral DNA. Oral adefovir dipivoxil is effective and generally well tolerated in HBeAg-positive and -negative patients chronically infected with wild-type or lamivudine-resistant HBV.

The potential antiviral effect of adefovir, an acyclic nucleoside phosphonate analog of 2′-deoxyadenosine monophosphate, was first studied by Holý and De Clercq in 1980s. Adefovir is an acyclic nucleotide analog of adenosine monophosphate which is phosphorylated to the active metabolite adefovir diphosphate by cellular kinases. Adefovir diphosphate inhibits HBV DNA polymerase (reverse transcriptase) by competing with the natural substrate deoxyadenosine triphosphate and by causing DNA chain termination after its incorporation into viral DNA. Oral adefovir dipivoxil is effective and generally well tolerated in HBeAg-positive and -negative patients chronically infected with wild-type or lamivudine-resistant HBV.

(R)-9-(2-Phosphonylmethoxypropyl)adenine (PMPA known as tenofovir) is an antiviral drug. Diphosphate of PMPA acts as a selective inhibitor of the HIV-1 reverse transcriptase. Tenofovir disoproxil was approved for clinical use for the treatment of HIV infection (AIDS) and chronic HBV infection.