Onapristone Explained

Onapristone (developmental code names ZK-89299, ZK-299) is a synthetic and steroidal antiprogestogen with additional antiglucocorticoid activity which was developed by Schering^[1] and described in 1984 but was never marketed.^{[2] [3]} 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).^[4] Moreover, compared to mifepristone, onapristone has reduced antiglucocorticoid activity, shows little antiandrogenic 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 endometrial contraceptive, but was discontinued during phase III clinical trials in 1995 due to findings that liver function abnormalities developed in a majority patients.^{[5] [6]}

Onapristone has been found to be effective in the treatment of breast cancer.^{[7] [8] [9]}

As of 2016, onapristone has re-emerged and is under development for the treatment of prostate cancer, currently in phase II clinical trials.^[10] 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.

Synthesis

Reaction of the steroid derivative (1) and the Grignard reagent 4-(dimethylamino)phenylmagnesium bromide (2) gives (3) by vinylogous addition to the epoxide. Oxidation of the alcohol group in the five-membered ring to a ketone gives compound (4). Irradiation of this material for 16 minutes with a mercury lamp results in the methyl group adjacent to the ketone changing from the beta to the alpha configuration, giving (5). Alkynylation with the anion formed from the acetylene derivative (6) using butyllithium gives (7). Catalytic hydrogenation to convert the alkyne group to an alkyl group, followed by acid treatment to remove the protecting groups yielded onapristone.^{[11] [12]}

See also

• List of investigational sex-hormonal agents § Progestogenics
• Aglepristone
• Lilopristone
• Telapristone
• Toripristone

Notes and References

1. Book: Lange CA, Sartorius CA, Abdel-Hafiz H, Spillman MA, Horwitz KB, Jacobsen BM . Progesterone receptor action: translating studies in breast cancer models to clinical insights . Advances in Experimental Medicine and Biology . 630 . 94–111 . 2008 . Springer . 18637487 . 10.1007/978-0-387-78818-0_7 . 978-0-387-78817-3 .
2. Book: 10.1007/978-1-4757-2085-3_15 . O . Dictionary of Drugs . 1990 . Elks J, Ganellin CR . 892–927 . Springer . 978-1-4757-2087-7 .
3. Book: 10.1007/978-94-011-4439-1_14 . O . Concise Dictionary of Pharmacological Agents . 1999 . Morton IK, Hall JM . 206–213 . Springer . 978-94-010-5907-7 .
4. Book: 10.1007/978-1-4612-4096-9_5 . Antiestrogen Resistance in Human Breast Cancer . Estrogens, Progestins, and Their Antagonists . 1997 . Pavlik EJ, Nelson K, Srinivasan S, Depriest PD, Kenady DE . Hormones in Health and Disease . 115–160 . Birkhäuser . 978-1-4612-8650-9 .
5. Katkam RR, Gopalkrishnan K, Chwalisz K, Schillinger E, Puri CP . Onapristone (ZK 98.299): a potential antiprogestin for endometrial contraception . American Journal of Obstetrics and Gynecology . 173 . 3 Pt 1 . 779–787 . September 1995 . 7573244 . 10.1016/0002-9378(95)90341-0 .
6. Book: 10.1007/978-3-540-69743-5_18 . Endocrine Therapy . Management of Breast Diseases . 2010 . Howell SJ, Howell A . 329–352 . Springer . 978-3-540-69742-8 .
7. Klijn JG, Setyono-Han B, Foekens JA . Progesterone antagonists and progesterone receptor modulators in the treatment of breast cancer . Steroids . 65 . 10–11 . 825–830 . 2000 . 11108894 . 10.1016/S0039-128X(00)00195-1 . 25524094 .
8. Robertson JF, Willsher PC, Winterbottom L, Blamey RW, Thorpe S . Onapristone, a progesterone receptor antagonist, as first-line therapy in primary breast cancer . European Journal of Cancer . 35 . 2 . 214–218 . February 1999 . 10448262 . 10.1016/S0959-8049(98)00388-8 .
9. Cottu PH, Bonneterre J, Varga A, Campone M, Leary A, Floquet A, Berton-Rigaud D, Sablin MP, Lesoin A, Rezai K, Lokiec FM, Lhomme C, Bosq J, Bexon AS, Gilles EM, Proniuk S, Dieras V, Jackson DM, Zukiwski A, Italiano A . Phase I study of onapristone, a type I antiprogestin, in female patients with previously treated recurrent or metastatic progesterone receptor-expressing cancers . PLOS ONE . 13 . 10 . e0204973 . 2018 . 30304013 . 6179222 . 10.1371/journal.pone.0204973 . free . 2018PLoSO..1304973C .
10. Web site: Onapristone - Context Therapeutics . Adis Insight . Springer Nature Switzerland AG .
11. EP . 0129499 . Neef G, Sauer G, Wiechert R, Beier S, Elger W, Henderson D, Rohde R . 13-alpha-alkyl gonanes, their preparation and pharmaceutical compositions containing them . patent . 1987-12-09 . 1984-06-13 . 1983-06-15 . Schering AG.
12. Neef G, Beier S, Elger W, Henderson D, Wiechert R . New steroids with antiprogestational and antiglucocorticoid activities . Steroids . 44 . 4 . 349–372 . October 1984 . 6152725 . 10.1016/S0039-128X(84)80027-6 .