Abemaciclib, previously known as LY2835219, is a potent and selective inhibitor of cyclin-dependent kinases: CDK4 and CDK6, developed by Eli Lilly, which is in clinical trial phase III for the treatment of breast cancer and non-small cell lung cancer (NSCLC) and in phase II for investigation of its treatment glioblastoma and melanoma.

Ribociclib, also known as LEE011, is an orally available cyclin-dependent kinase (CDK) inhibitor targeting cyclin D1/CDK4 and cyclin D3/CDK6 cell cycle pathway, with potential antineoplastic activity. CDK4/6 inhibitor LEE011 specifically inhibits CDK4 and 6, thereby inhibiting retinoblastoma (Rb) protein phosphorylation. Inhibition of Rb phosphorylation prevents CDK-mediated G1-S phase transition, thereby arresting the cell cycle in the G1 phase, suppressing DNA synthesis and inhibiting cancer cell growth. Overexpression of CDK4/6, as seen in certain types of cancer, causes cell cycle deregulation. Ribociclib is in phase III clinical trials by Novartis for the treatment of postmenopausal women with advanced breast cancer. Phase II clinical trials are also in development for the treatment of liposarcoma, ovarian cancer, fallopian tube cancer, peritoneum cancer, endometrial cancer, and gastrointestinal cancer. Preregistration for Breast cancer (First-line therapy, Combination therapy, Late-stage disease) in the USA (PO) in November 2016.

Niraparib (MK-4827) displays excellent PARP 1 and 2 inhibition. Inhibition of PARP in the context of defects in other DNA repair mechanisms provide a tumor specific way to kill cancer cells. Niraparib is in development with TESARO, under licence from Merck & Co, for the treatment of cancers (ovarian, fallopian tube and peritoneal cancer, breast cancer, prostate cancer and Ewing's sarcoma). Niraparib was characterized in a number of preclinical models before moving to phase I clinical trials, where it showed excellent human pharmacokinetics suitable for once a day oral dosing, achieved its pharmacodynamic target for PARP inhibition, and had promising activity in cancer patients. It is currently being tested in phase 3 clinical trials as maintenance therapy in ovarian cancer and as a treatment for breast cancer.

Rucaparib is a poly (ADP-ribose) polymerase (PARP) inhibitor indicated for the treatment of advanced mutant BRCA ovarian cancer. Rucaparib is being investigated in clinical trials against prostate cancer, breast cancer and other neoplasms.

Ixabepilone is an antineoplastic agent, epothilone and mitotic inhibitor that is FDA approved for the treatment of patients with metastatic or locally advanced breast cancer resistant to treatment with an anthracycline and a taxane, or whose cancer is taxane resistant and for whom further anthracycline therapy is contraindicated. Ixabepilone binds directly to beta-tubulin subunits on microtubules, leading to suppression of microtubule dynamics. Ixabepilone suppresses the dynamic instability of alpha-beta-II and alpha-beta-III microtubules. The most common adverse reactions (≥20%) are peripheral sensory neuropathy, fatigue/asthenia, myalgia/arthralgia, alopecia, nausea, vomiting, stomatitis/mucositis, diarrhea, and musculoskeletal pain. Inhibitors of CYP3A4 may increase plasma concentrations of ixabepilone.

Lapatinib is a small molecule and a member of the 4-anilinoquinazoline class of kinase inhibitors. It is present as the monohydrate of the ditosylate salt (trade name TYKERB). Lapatinib is dual inhibitor of the EGFR (epidermal growth factor receptor; also called HER1 or ErbB1) and HER2 receptor tyrosine kinases. Lapatinib was developed by GlaxoSmithKline, however, Novartis subsequently acquired all the rights to the drug from GlaxoSmithKline. TYKERB is indicated in combination therapy for the treatment of metastatic breast cancer that overexpresses the HER2 receptor.

Capecitabine is a fluoropyrimidine carbamate with antineoplastic activity. It is an orally administered systemic prodrug which is converted to 5-fluorouracil (5-FU). Both normal and tumor cells metabolize 5-FU to 5-fluoro-2’-deoxyuridine monophosphate (FdUMP) and 5-fluorouridine triphosphate (FUTP). These metabolites cause cell injury by two different mechanisms. First, FdUMP and the folate cofactor, N5-10-methylenetetrahydrofolate, bind to thymidylate synthase (TS) to form a covalently bound ternary complex. This binding inhibits the formation of thymidylate from 2’-deoxyuridylate. Thymidylate is the necessary precursor of thymidine triphosphate, which is essential for the synthesis of DNA, so that a deficiency of this compound can inhibit cell division. Second, nuclear transcriptional enzymes can mistakenly incorporate FUTP in place of uridine triphosphate (UTP) during the synthesis of RNA. This metabolic error can interfere with RNA processing and protein synthesis. Most common adverse reactions (≥30%) were diarrhea, hand-and-foot syndrome, nausea, vomiting, abdominal pain, fatigue/weakness, and hyperbilirubinemia. The concentration of 5-fluorouracil is increased and its toxicity may be enhanced by leucovorin.

Letrozole (trade name Femara), a nonsteroidal aromatase inhibitor. Femara is indicated for the adjuvant treatment of postmenopausal women with hormone receptor positive early breast cancer. Also is indicated for the extended adjuvant treatment of early breast cancer in postmenopausal women, who have received 5 years of adjuvant tamoxifen therapy. Femara has to be used for first-line treatment of postmenopausal women with hormone receptor positive or unknown, locally advanced or metastatic breast cancer and for the treatment of advanced breast cancer in postmenopausal women with disease progression following antiestrogen therapy. Treatment of breast cancer thought to be hormonally responsive (i.e., estrogen and/or progesterone receptor positive or receptor unknown) has included a variety of efforts to decrease estrogen levels (ovariectomy, adrenalectomy, hypophysectomy) or inhibit estrogen effects (antiestrogens and progestational agents). These interventions lead to decreased tumor mass or delayed progression of tumor growth in some women. In postmenopausal women, estrogens are mainly derived from the action of the aromatase enzyme, which converts adrenal androgens (primarily androstenedione and testosterone) to estrone and estradiol. The suppression of estrogen biosynthesis in peripheral tissues and in the cancer tissue itself can therefore be achieved by specifically inhibiting the aromatase enzyme. Letrozole inhibits the conversion of androgens to estrogens. Letrozole selectively inhibits gonadal steroidogenesis but has no significant effect on adrenal mineralocorticoid or glucocorticoid synthesis. Letrozole inhibits the aromatase enzyme by competitively binding to the heme of the cytochrome P450 subunit of the enzyme, resulting in a reduction of estrogen biosynthesis in all tissues. Treatment of women with letrozole significantly lowers serum estrone, estradiol and estrone sulfate and has not been shown to significantly affect adrenal corticosteroid synthesis, aldosterone synthesis, or synthesis of thyroid hormones. Letrozole is rapidly and completely absorbed from the gastrointestinal tract and absorption is not affected by food. Metabolism to a pharmacologically inactive carbinol metabolite (4,4'¬ methanol-bisbenzonitrile) and renal excretion of the glucuronide conjugate of this metabolite is the major pathway of letrozole clearance. In human microsomes with specific CYP isozyme activity, CYP3A4 metabolized letrozole to the carbinol metabolite while CYP2A6 formed both this metabolite and its ketone analog. In human liver microsomes, letrozole strongly inhibited CYP2A6 and moderately inhibited CYP2C19. The most common side effects are sweating, hot flashes, arthralgia (joint pain), and fatigue

Docetaxel was protected by patents (U.S. patent and European patent) which were owned by Sanofi-Aventis, and so was available only under the Taxotere brand name internationally. The European patent expired in 2010. Docetaxel is a clinically well-established anti-mitotic chemotherapy medication used for the treatment of patients with locally advanced or metastatic breast cancer after failure of prior chemotherapy. Also used as a single agent in the treatment of patients with locally advanced or metastatic non-small cell lung cancer after failure of prior platinum-based chemotherapy. It is also used in combination with prednisone, in the treatment of patients with androgen independent (hormone refractory) metastatic prostate cancer. Furthermore, docetaxel has uses in the treatment of gastric adenocarcinoma and head and neck cancer. Docetaxel interferes with the normal function of microtubule growth. Whereas drugs like colchicine cause the depolymerization of microtubules in vivo, docetaxel 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, docetaxel binds to the β-subunit of tubulin. Tubulin is the "building block" of mictotubules, and the binding of docetaxel locks these building blocks in place. The resulting microtubule/docetaxel 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 docetaxel 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.

Anastrozole (marketed under the trade name Arimidex by AstraZeneca) is a drug indicated in the treatment of breast cancer in post-menopausal women. It is used both in adjuvant therapy (i.e. following surgery) and in metastatic breast cancer. It decreases the amount of estrogens that the body makes. Anastrozole belongs in the class of drugs known as aromatase inhibitors. It inhibits the enzyme aromatase, which is responsible for converting androgens (produced by women in the adrenal glands) to estrogens. The growth of many cancers of the breast is stimulated or maintained by estrogens. In postmenopausal women, estrogens are mainly derived from the action of the aromatase enzyme, which converts adrenal androgens (primarily androstenedione and testosterone) to estrone and estradiol. The suppression of estrogen biosynthesis in peripheral tissues and in the cancer tissue itself can therefore be achieved by specifically inhibiting the aromatase enzyme. Anastrozole is a selective non-steroidal aromatase inhibitor. It significantly lowers serum estradiol concentrations and has no detectable effect on formation of adrenal corticosteroids or aldosterone.