Chemistry
Gemcitabine is a synthetic pyrimidine nucleoside prodrug—a nucleoside analog in which the hydrogen atoms on the 2 carbon of deoxycytidine are replaced by fluorine atoms.The synthesis described and pictured below is the original synthesis done in the Eli Lilly Company labs. Synthesis begins with enantiopure D-glyceraldehyde (R)-2 as the starting material which can made from D-mannitol in 2–7 steps. Then fluorine is introduced by a "building block" approach using ethyl bromodifluroacetate. Then, Reformatsky reaction under standard conditions will yield a 3:1 anti/syn diastereomeric mixture, with one major product. Separation of the diastereomers is carried out via HPLC, thus yielding the anti-3 gemcitabine in a 65% yield. At least two other full synthesis methods have also been developed by different groups. History
Gemcitabine was first synthesized in Larry Hertels lab at Eli Lilly and Company during the early 1980s. It was intended as an antiviral drug, but preclinical testing showed that it killed leukemia cells in vitro.During the early 1990s gemcitabine was studied in clinical trials. The pancreatic cancer trials found that gemcitabine increased one-year survival time significantly, and it was approved in the UK in 1995 and approved by the FDA in 1996 for pancreatic cancers. In 1998, gemcitabine received FDA approval for treating non-small cell lung cancer and in 2004, it was approved for metastatic breast cancer.European labels were harmonized by the EMA in 2008.By 2008, Lillys worldwide sales of gemcitabine were about $1.7 billion; at that time its US patents were set to expire in 2013 and its European patents in 2009.
TTP is a blood disorder and can lead to microangipathic hemolytic anemia (MAHA), neurologic abnormalities, fever, and renal disease. Pharmacology
Gemcitabine is hydrophilic and must be transported into cells via molecular transporters for nucleosides (the most common transporters for gemcitabine are SLC29A1 SLC28A1, and SLC28A3). After entering the cell, gemcitabine is first modified by attaching a phosphate to it, and so it becomes gemcitabine monophosphate (dFdCMP). This is the rate-determining step that is catalyzed by the enzyme deoxycytidine kinase (DCK). Two more phosphates are added by other enzymes. After the attachment of the three phosphates gemcitabine is finally pharmacologically active as gemcitabine triphosphate (dFdCTP). After being thrice phosphorylated, gemcitabine can masquerade as deoxycytidine triphosphate and is incorporated into new DNA strands being synthesized as the cell replicates.When gemcitabine is incorporated into DNA it allows a native, or normal, nucleoside base to be added next to it. This leads to "masked chain termination" because gemcitabine is a "faulty" base, but due to its neighboring native nucleoside it eludes the cells normal repair system (base-excision repair). Thus, incorporation of gemcitabine into the cells DNA creates an irreparable error that leads to inhibition of further DNA synthesis, and thereby leading to cell death.The form of gemcitabine with two phosphates attached (dFdCDP) also has activity; it inhibits the enzyme ribonucleotide reductase (RNR), which is needed to create new DNA nucleotides. The lack of nucleotides drives the cell to uptake more of the components it needs to make nucleotides from outside the cell, which also increases uptake of gemcitabine.