Product Code Database
Onapristone () (developmental code names ZK-89299, ZK-299) is a synthetic and antiprogestogen with additional antiglucocorticoid activity which was developed by Schering AG (2025). 9780387788173, Springer. ISBN 9780387788173 and described in 1984 but was never marketed. (1990). 9781475720877, Springer. ISBN 9781475720877 (1999). 9789401059077, Springer. ISBN 9789401059077 It is a silent antagonist of the progesterone receptor (PR), in contrast to the related antiprogestogen mifepristone (which is a weak partial agonist of the receptor). (1997). 9781461286509, Birkhäuser. ISBN 9781461286509 Moreover, compared to mifepristone, onapristone has reduced antiglucocorticoid activity, shows little activity, and has 10- to 30-fold greater potency as an antiprogestogen. The medication was under development for clinical use, for instance in the treatment of breast cancer and as an endometrium contraceptive, but was discontinued during phase III in 1995 due to findings that liver function abnormalities developed in a majority patients. (2025). 9783540697428, Springer. ISBN 9783540697428
Onapristone has been found to be effective in the treatment of breast cancer.
As of 2016, onapristone has re-emerged and is under development for the treatment of prostate cancer, currently in phase II . It was also under development for the treatment of endometrial cancer, breast cancer, ovarian cancer, and uterine cancer, but was discontinued for these indications in favor of focusing on prostate cancer.
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