Penciclovir (DENAVIR®) is a synthetic acyclic guanine derivative with antiviral activity, mainly used to treat infections from herpes simplex virus (HSV) types 1 and 2. In cells infected with HSV-1 or HSV-2, the viral thymidine kinase phosphorylates penciclovir to a monophosphate form that, in turn, is converted by cellular kinases to the active form penciclovir triphosphate. Biochemical studies demonstrate that penciclovir triphosphate inhibits HSV polymerase competitively with deoxyguanosine triphosphate. Consequently, herpes viral DNA synthesis and, therefore, replication are selectively inhibited. Famciclovir (FAMVIR®) is a prodrug form of penciclovir with improved oral bioavailability.

Cladribine is used for the treatment of hairy cell leukemia and multiple sclerosis (MS). As a purine analog, it is a synthetic anti-cancer agent that also suppresses the immune system. Chemically, it mimics the nucleoside adenosine and thus inhibits the enzyme adenosine deaminase, which interferes with the cell's ability to process DNA. It can be distinguished from other chemotherapeutic agents affecting purine metabolism in that it is cytotoxic to both actively dividing and quiescent lymphocytes and monocytes, inhibiting both DNA synthesis and repair. Cladribine injection is a potent antineoplastic agent with potentially significant toxic side effects. In MS, the novel mechanism of action of cladribine is expected to reduce inflammation, autoimmune effects and autoreactive cell damage, thereby improving the integrity of the blood–brain barrier. Thus, the effects of cladribine may target some of the key events that are central to the pathophysiology of MS.

Paclitaxel is a mitotic inhibitor used in cancer chemotherapy. It was discovered in a US National Cancer Institute program at the Research Triangle Institute in 1967 when Monroe E. Wall and Mansukh C. Wani isolated it from the bark of the Pacific yew tree, Taxus brevifolia and named it taxol. Later it was discovered that endophytic fungi in the bark synthesize paclitaxel. When it was developed commercially by Bristol-Myers Squibb (BMS), the generic name was changed to paclitaxel and the BMS compound is sold under the trademark Taxol. In this formulation, paclitaxel is dissolved in Kolliphor EL and ethanol, as a delivery agent. Taxol is marketed for the treatment of Breast cancer; Gastric cancer; Kaposi's sarcoma; Non-small cell lung cancer; Ovarian cancer. A newer formulation, in which paclitaxel is bound to albumin, is sold under the trademark Abraxane. Paclitaxel is a taxoid antineoplastic agent indicated as first-line and subsequent therapy for the treatment of advanced carcinoma of the ovary, and other various cancers including breast cancer. Paclitaxel is a novel antimicrotubule agent that promotes the assembly of microtubules from tubulin dimers and stabilizes microtubules by preventing depolymerization. This stability results in the inhibition of the normal dynamic reorganization of the microtubule network that is essential for vital interphase and mitotic cellular functions. In addition, paclitaxel induces abnormal arrays or "bundles" of microtubules throughout the cell cycle and multiple asters of microtubules during mitosis. Used in the treatment of Kaposi's sarcoma and cancer of the lung, ovarian, and breast. Abraxane® is specfically indicated for the treatment of metastatic breast cancer and locally advanced or metastatic non-small cell lung cancer. Paclitaxel interferes with the normal function of microtubule growth. Whereas drugs like colchicine cause the depolymerization of microtubules in vivo, paclitaxel arrests their function by having the opposite effect; it hyper-stabilizes their structure. This destroys the cell's ability to use its cytoskeleton in a flexible manner. Specifically, paclitaxel binds to the β subunit of tubulin. Tubulin is the "building block" of mictotubules, and the binding of paclitaxel locks these building blocks in place. The resulting microtubule/paclitaxel complex does not have the ability to disassemble. This adversely affects cell function because the shortening and lengthening of microtubules (termed dynamic instability) is necessary for their function as a transportation highway for the cell. Chromosomes, for example, rely upon this property of microtubules during mitosis. Further research has indicated that paclitaxel induces programmed cell death (apoptosis) in cancer cells by binding to an apoptosis stopping protein called Bcl-2 (B-cell leukemia 2) and thus arresting its function.

Fludarabine or fludarabine phosphate is a chemotherapy drug used in the treatment of hematological malignancies (cancers of blood cells such as leukemias and lymphomas). It is a purine analog, which interferes with DNA synthesis. Fludarabine phosphate is a fluorinated nucleotide analog of the antiviral agent vidarabine, 9-β-D-arabinofuranosyladenine (ara-A), that is relatively resistant to deamination by adenosine deaminase. Fludarabine (marketed as fludarabine phosphate under the trade name Fludara) is a chemotherapy drug used in the treatment of hematological malignancies. Fludarabine phosphate is rapidly dephosphorylated to 2-fluoro-ara-A and then phosphorylated intracellularly by deoxycytidine kinase to the active triphosphate, 2-fluoro-ara-ATP. This metabolite appears to act by inhibiting DNA polymerase alpha, ribonucleotide reductase and DNA primase, thus inhibiting DNA synthesis. The mechanism of action of this antimetabolite is not completely characterized and may be multi-faceted.

Eflornithine is a prescription drug indicated in the treatment of facial hirsutism (excessive hair growth). Eflornithine hydrochloride cream for topical application is intended for use in women suffering from facial hirsutism and is sold by Allergan, Inc. under the brand name Vaniqa. Besides being a non-mechanical and non-cosmetic treatment, eflornithine is the only non-hormonal and non-systemic prescription option available for women who suffer from facial hirsutism. Eflornithine for injection against sleeping sickness was manufactured by Sanofi Aventis and sold under the brand name Ornidyl in the USA. It is now discontinued. Eflornithine is on the World Health Organization's List of Essential Medicines. Eflornithine prevents hair growth by inhibiting the anagen phase of hair production. This occurs by eflornithine irreversibly binding (also called suicide inhibition) to ornithine decarboxylase (ODC) and physically preventing the natural substrate ornithine from accessing the active site.

Idarubicin is an antineoplastic in the anthracycline class.Idarubicin hydrochloride is a DNA-intercalating analog of daunorubicin which has an inhibitory effect on nucleic acid synthesis and interacts with the enzyme topoisomerase II. The absence of a methoxy group at position 4 of the anthracycline structure gives the compound a high lipophilicity which results in an increased rate of cellular uptake compared with other anthracyclines.Idarubicin possesses an antitumor effect against a wide spectrum of tumors, either grafted or spontaneous. Idarubicin in combination with other approved antileukemic drugs is indicated for the treatment of acute myeloid leukemia (AML) in adults.

Podofilox ((abbreviated as PPT), otherwise known as podofilox) is an antimitotic drug which can be chemically synthesized or purified from the plant families Coniferae and Berberidaceae (e.g. species of Juniperus and Podophyllum). Podofilox 0.5% solution is indicated for the topical treatment of external genital warts (Condyloma acuminatum). This product is not indicated in the treatment of perianal or mucous membrane warts. Treatment of genital warts with podofilox results in necrosis of visible wart tissue. The exact mechanism of action is unknown, but is believed to exert its antimitotic effect by binding to tubulin, at a site close to but not identical to the binding site of colchicine; it is thought that this antimitotic effect causes necrosis of wart tissue, the observed clinical effect. In addition, podofilox is known to interfere with nucleoside transport, which may also contribute to its action. Adverse effects reported in less than 5% of the patients included pain with intercourse, insomnia, tingling, bleeding, tenderness, chafing, malodor, dizziness, scarring, vesicle formation, crusting edema, dryness/peeling, foreskin irretraction, hematuria, vomiting and ulceration.

Carboplatin is an organoplatinum compound that possesses antineoplastic activity. Carboplatin is an intravenously administered platinum coordination complex and alkylating agent, which is used as a chemotherapeutic agent for the treatment of various cancers, mainly of advanced ovarian. Carboplatin is indicated for the palliative treatment of patients with ovarian carcinoma recurrent after prior chemotherapy, including patients who have been previously treated with cisplatin. In addition this drug can be used to treat others cancers. Carboplatin therapy is associated with a low rate of transient serum aminotransferase elevations and with rare instances of clinically apparent liver injury. Carboplatin, like cisplatin, produces predominantly interstrand DNA cross-links rather than DNA-protein cross-links. This effect is apparently cell-cycle nonspecific. The aquation of carboplatin, which is thought to produce the active species, occurs at a slower rate than in the case of cisplatin. Despite this difference, it appears that both carboplatin and cisplatin induce equal numbers of drug-DNA cross-links, causing equivalent lesions and biological effects.

Ganciclovir is a synthetic acyclic nucleoside analogue of 2'-deoxyguanosine active against cytomegalovirus. Ganciclovir has been shown to be active against cytomegalovirus (CMV) and herpes simplex virus (HSV) in humans. To achieve anti-CMV activity, ganciclovir is phosphorylated first to the monophosphate form by a CMV-encoded (UL97 gene) protein kinase homologue, then to the di- and triphosphate forms by cellular kinases. Ganciclovir triphosphate concentrations may be 100-fold greater in CMV-infected than in uninfected cells, indicating preferential phosphorylation in infected cells. Ganciclovir triphosphate, once formed, persists for days in the CMV-infected cell. Ganciclovir triphosphate is believed to inhibit viral DNA synthesis by (1) competitive inhibition of viral DNA polymerases; and (2) incorporation into viral DNA, resulting in eventual termination of viral DNA elongation. Ganciclovir is indicated for the treatment of CMV retinitis in immunocompromised patients, including patients with acquired immunodeficiency syndrome (AIDS) and for the treatment of acute herpetic keratitis.

Zidovudine is a nucleoside reverse transcriptase inhibitor (NRTI) with activity against Human Immunodeficiency Virus Type 1 (HIV-1). Zidovudine is phosphorylated to active metabolites that compete for incorporation into viral DNA. They inhibit the HIV reverse transcriptase enzyme competitively and act as a chain terminator of DNA synthesis. The lack of a 3'-OH group in the incorporated nucleoside analogue prevents the formation of the 5' to 3' phosphodiester linkage essential for DNA chain elongation, and therefore, the viral DNA growth is terminated. Zidovudine, a structural analog of thymidine, is a prodrug that must be phosphorylated to its active 5′-triphosphate metabolite, zidovudine triphosphate (ZDV-TP). It inhibits the activity of HIV-1 reverse transcriptase (RT) via DNA chain termination after incorporation of the nucleotide analogue. It competes with the natural substrate dGTP and incorporates itself into viral DNA. It is also a weak inhibitor of cellular DNA polymerase α and γ. Zidovudine is used in combination with other antiretroviral agents for the treatment of human immunovirus (HIV) infections. Zidovudine is marketed as Retrovir.