Epirubicin is an anthracycline drug used for chemotherapy. It can be used in combination with other medications to treat breast cancer in patients who have had surgery to remove the tumor. It is marketed by Pfizer under the trade name Ellence in the US and Pharmorubicin or Epirubicin Ebewe elsewhere.
Similarly to other anthracyclines, epirubicin acts by intercalating DNA strands.
Intercalation results in complex formation which inhibits DNA and RNA synthesis. It also triggers DNA cleavage by topoisomerase II, resulting in mechanisms that lead to cell death. Binding to cell membranes and plasma proteins may be involved in the compound's cytotoxic effects. Epirubicin also generates free radicals that cause cell and DNA damage.
Epirubicin is favoured over doxorubicin, the most popular anthracycline, in some chemotherapy regimens as it appears to cause fewer side-effects. Epirubicin has a different spatial orientation of the hydroxyl group at the 4' carbon of the sugar - it has the opposite chirality - which may account for its faster elimination and reduced toxicity. Epirubicin is primarily used against breast and ovarian cancer, gastric cancer, lung cancer and lymphomas.
Medical uses
Adjuvant therapy
The aim of Epirubicin as adjuvanted therapy is to eradicate micro metastasis and prolong disease free survival.
Vs standard adjuvant therapy
The Standard adjuvant therapy is a combination of cyclophosphamide, methotrexate and fluorouracil (CMF). In comparison to this the Epirubicin therapy contains fluorouracil/epirubicin/cyclophosphamide (FEC). Three large randomized studies have directly compared the epirubicin-containing regimen fluorouracil/epirubicin/cyclophosphamide (FEC) with CMF in the adjuvant setting. Trial one and two contained premenopausal node-positive women with breast cancer, Trial three pre- and postmenopausal women with node-positive or negative breast cancer. It was discovered that FEC is at least as effective as CMF in premenopausal women with node positive- or negative breast cancer and that FEC produced no additional benefit in terms of 5-year relapse-free or overall survival.
Pharmacology
Mechanism of action
The mechanism of action of epirubicin is similar to that of doxorubicin and other anthracycline drugs. The observed clinical differences between epirubicin and doxorubicin can be explained by the pharmacokinetic differences based on the different affinity to DNA and lipophilicity, as there is no indication that different mechanisms are involved in their activity.
Epirubicin first forms a complex with DNA by intercalation of its planar rings between nucleotide base pairs. (Pharmacia & Upjohn Company LLC, 1999) This inhibits replication and transcription and triggers DNA cleavage by topoisomerase II. Epirubicin then stabilizes the topoisomerase II-DNA complex, resulting in irreversible DNA strand breakage, leading to cell death. Epirubicin is also capable of generating cytotoxic free radicals, which are very reactive against DNA, cell membranes and mitochondria.
Epirubicin exhibits activity in all phases of the cell cycle, but maximal cell kill occurs during the S phase and G2 phase of the cell cycle.
Pharmacokinetics
The pharmacokinetic properties of epirubicin can be described by a 3-compartment model, with half-lives for the initial (alpha), intermediate (beta) and terminal (gamma) elimination phases of approximately 3 minutes, 1 hour and 30 hours, respectively. Only the latter differs substantially compared to doxorubicin, as the terminal elimination half-life of doxorubicin is estimated to be approximately 40-70% longer than that of epirubicin.
The volume of distribution of epirubicin is found to be high and variable (1 000- 1 500), but similar to those reported for doxorubicin. This unique pathway might explain the better tolerability of this drug compared with doxorubicin. Cardiotoxicity is a severe side effect and the exact pathway is still unknown. However, there is good evidence to suggest that cardiotoxicity is caused at least in part by the avid interaction of anthracyclines with iron, resulting in the formation of metal ion complexes. at 2.2% overall with a cumulative doxorubicin dose-dependent incidence of CHF of 3%, 7%, and 18% at 400, 550, and 700 mg/m2, respectively.
There are a lot of adverse effects of epirubicin related with the dose-limiting. The major commun negative effects are fever, diarrhea, nausea and vomiting.
Common toxicities are neutropenia (<1 × 109 cells/L) without any death related and in lesser measures anemia and thrombocytopenia.
Its shelf life (def. as the time it takes to degrade 10% from the initial concentration) has been documented as at least 14 and 180 days at 25 °C and 4 °C, respectively in a 0.9% sodium chloride solution in polypropylene syringes.
Synthesis
There are multiple ways of synthesizing epirubicin depending on which starting material is used as a precursor.
Daunorubicin
One pathway starts from Daunorubicin, a common byproduct found in fermentation, since it is relatively easily available and already structurally similar to the product (only requiring minor alterations).
Firstly, the amine group is protected using trifluoroacetic acid to stop it from further reactions. Next the hydroxyl group needs to be changed from an equatorial position to an axial, this is achieved by firstly oxidizing an intermediate sulfoxy salt to a keto group (losing the optical center) followed by a stereo-specific reduction using sodium borohydride to give the hydroxide group in the axial position.
Secondly, the focus shifts to carbon number 13 where it is necessary to add a hydroxide group which is achieved by bromination followed by a reaction with an alkali salt of formic acid and water to give the final product.
There is an older variant of this pathway which involves first splitting the Daunorubicin, into daunomycin one and daunosamine methyl ether, using methanol. Analogous reactions are performed to get the two hydroxyl groups onto their positions and the rings are then recombined and the protecting groups released. The drawbacks are more chemicals are used and daunomycin one and daunosamine need to be separated first.
13-daunorubicinol
The second pathway Upjohn applied for approval by the U.S. Food and Drug Administration (FDA) in node-positive breast cancer in 1984, but was turned down because of lack of data. In 1999 Pharmacia (who had by then merged with Upjohn) received FDA approval for the use of epirubicin as a component of adjuvant therapy in node-positive patients.
Patent protection for epirubicin expired in August 2007.