Gemcitabine is a nucleoside analog used as chemotherapy. It is marketed as Gemzar® by Eli Lilly and Company. Gemcitabine inhibits thymidylate synthetase, leading to inhibition of DNA synthesis and cell death. Gemcitabine is a prodrug so activity occurs as a result of intracellular conversion to two active metabolites, gemcitabine diphosphate and gemcitabine triphosphate by deoxycitidine kinase. Gemcitabine diphosphate also inhibits ribonucleotide reductase, the enzyme responsible for catalyzing synthesis of deoxynucleoside triphosphates required for DNA synthesis. Finally, Gemcitabine triphosphate (diflurorodeoxycytidine triphosphate) competes with endogenous deoxynucleoside triphosphates for incorporation into DNA. Gemcitabine is indicated for the treatment of advanced ovarian cancer that has relapsed at least 6 months after completion of platinum-based therapy; metastatic ovarian cancer; inoperable, locally advanced (Stage IIIA or IIIB), or metastatic (Stage IV) non-small cell lung cancer; and locally advanced (nonresectable Stage II or Stage III) or metastatic (Stage IV) adenocarcinoma of the pancreas.

Rigosertib sodium (ON 01910.Na) is a small molecule inhibitor of critical pathways important in the growth and survival of cancer cells, being developed by Onconova Therapeutics ("Onconova") for the treatment of hematologic malignancies and solid tumors. Rigosertib (ON-01910) is a non-ATP-competitive inhibitor of PLK1 with IC50 of 9 nM in a cell-free assay. It shows 30-fold greater selectivity against Plk2 and no activity to Plk3. Extensive Phase I and Phase II studies with rigosertib have been conducted at leading institutions in the U.S. and abroad in more than 450 patients with solid tumors and hematological cancers, including MDS and AML. MDS and AML are blood disorders widely recognized as difficult to manage, with limited therapeutic options available for patients, especially those with drug-resistant disease. The multi-site Phase III ONTIME trial in MDS patients is under a Special Protocol Assessment (SPA) from the U.S. FDA and is being supported by an award from the Therapeutics Acceleration Program (TAP) of the Leukemia and Lymphoma Society (LLS). FDA has granted Orphan Drug Designation for the use of rigosertib in MDS. The clinical program in solid tumors is also advancing with initiation of the Phase II/III combination ONTRAC trial (ON 01910.Na TRial in Patients with Advanced Pancreatic Cancer) and Phase II single agent trial in ovarian cancer. In Japan, SymBio is developing rigosertib for the treatment of refractory/relapsed HR-MDS (IV form) and first-line LR-MDS (oral form).

Gemcitabine elaidate is an ester of anticancer drug gemcitabine and elaidic fatty acid. The motivation to make an ester was to facilitate gemcitabine uptake and prolong retention in the cell. The drug is converted to parent compound gemcitabine both inside and outside the cell. Gemcitabine elaidate was developed by Clavis Pharma for treatment of solid tumors, including non-small cell lung cancer and pancreatic cancer, but its development was discontinued after product missed the primary endpoint in the Phase II LEAP trial to treat metastatic pancreatic cancer.

Cytosine is a pyrimidine nucleobase, one of the five main bases of nucleic acids. In DNA and RNA cytosine is paired with guanine. Only small amounts of cytosine administered with food are incorporated in DNA. The majority of cytosine is synthesized de-novo starting from carbamoyl phosphate.