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Sunday, June 16, 2013

Approved for Osteoporosis, Bazedoxifene (BZA) shows Promise, Even in Cancer of Breast Resistant to Tamoxifen

Posted by Prahallad Panda on 7:15 PM Comments

Now, there are several drugs for treatment of osteoporosis, commonly advised is a group of drugs called bisphosphonates. Commonly used bisphosphonates are alendronate, rosedronate and zolendronic acid etc..
The mode of administration may be oral or intravenous; for orally usable ones, there are specific advices like to be taken in empty stomach, patient remain without food, and in erect position for at least one hour after taking the drug etc.. Taking the drug in IV (Intravenous) route and following the instructions for oral intake may not be patient compliant too.
Bazedoxifene (BZA) from the family of drugs called SERMs (Selective Estrogen Receptor Modulators) that act in different way in different tissue expressing estrogen receptors; bone friendly (Agonist activity), but against breast (Antagonist); whereas bisphosphonates are antagonistic to all the tissue. In contrast to bisphosphonates, there is no specific instruction of oral intake of the drug.

Structural diagram of bazedoxifene. Created us...
Structural diagram of bazedoxifene. Created using ACD/ChemSketch 8.0 and Inkscape. (Photo credit: Wikipedia)

Bisphosphonates have the bad reputation of causing atypical fractures and osteonecrosis of jaw bones.
That is why, bezedoxifene may be considered as a safer alternative to the bisphosphonates. BZA has also been paired with conjugated estrogen (CE) in menopausal therapy called TSEC (Tissue Specific Estrogen Complex) for the prevention of osteoporosis and treatment of menopausal symptoms.
It was recently approved in the European Union for the treatment of osteoporosis in post-menopausal women at increased risk of fracture. The potential of this drug to treat the condition has been well documented in SMART (Estrogens, Menopause, And Response to Therapy) trial.
The benefits from tamoxifen and aromatase inhibitors like letrozole in breast caner treatment after surgery and chemotherapy in estrogen positive (ER+) tumours are invaluable in post-menopausal patients. Recently, researchers started recommending tamoxifen for 10 years instead of 5 years for this reason.
In a substantial number of patients, eventually, after initial response to tamoxifen treatment, cancers do recur. Treatment with tamoxifen, which is a SERM that works on tissue expressing estrogen receptor all over the body, makes patient prone for osteoporosis in absence of estrogen in bone, in a situation, where as such, there is lack of the hormone in post-menopausal state.
Now, it has been seen that bazedoxifene, like tamoxifen, although belongs to class of (SERMs); but unlike tamoxifen, has some of the properties of a newer group of drugs, known as selective estrogen receptor degraders, or SERDs, which can target the estrogen receptor for destruction in selective tissue.
These drugs are distinguished by their ability to behave like estrogen in some tissues, while significantly blocking estrogen action in other tissues.
It even works in case of breast cancers that has become resistant to treatment of tamoxifen and aromatase inhibitors because of this property.
So, it remains to be seen, if the drug can come out as a winner, to be recommended for treatment of breast cancer too; in which case, it will be a drug addressing two issues at one time i.e. breast cancer treatment and prevention of osteoporosis in those patients.
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