Irosustat

Irosustat (INN, USAN; developmental code names STX-64, 667-coumate, BN-83495; also known as oristusane) is an orally active, irreversible, nonsteroidal inhibitor of steroid sulfatase (STS) and member of the aryl sulfamate ester class of drugs[2] that was under development by Sterix Ltd and Ipsen for the treatment of hormone-sensitive cancers such as breast cancer, prostate cancer, and endometrial cancer but has not yet been marketed.[3][1] The drug[4][5] was designed and synthesized in the group of Professor Barry V L Potter at the Department of Pharmacy & Pharmacology, University of Bath, working together with Professor Michael J. Reed at Imperial College, London and its initial development was undertaken through the university spin-out company Sterix Ltd and overseen by Cancer Research UK (CRUK). Results of the "first-in-class" clinical trial in breast cancer of an STS inhibitor in humans were published in 2006[6] and dose optimisation studies and further clinical data have been reported.[7]

Irosustat
Clinical data
Other namesOristusane; STX-64; 667-Coumate; BN-83495; STX-64PC
Routes of
administration		By mouth[1]
Pharmacokinetic data
Elimination half-life24 hours[1]
Identifiers
CAS Number
PubChem CID
DrugBank
ChemSpider
UNII
KEGG
CompTox Dashboard (EPA)
Chemical and physical data
FormulaC14H15NO5S
Molar mass309.34 g·mol−1
3D model (JSmol)

By inhibiting STS, irosustat prevents the conversion of hormonally inactive steroid sulfates such as DHEA sulfate (DHEA-S) and estrone sulfate (E1S) into their respective active forms, DHEA and estrone (which, in turn, can be transformed into more potent androgens and estrogens, respectively).[1] Administration of 5 mg/day irosustat to women with breast cancer for 5 days inhibited STS activity by 98 to 99% in breast tumor tissue and significantly decreased serum levels of estrone (by 76%), estradiol (by 39%), DHEA (by 41%), androstenediol (by 70%), androstenedione (by 62%), and testosterone (by 30%), whereas levels of DHEA-S and E1S increased slightly (by 1.1% and 7.4%, respectively).[1]

Despite Irosustat being quickly degraded in plasma ex vivo, this is prevented in vivo by its sequestration almost completely inside red blood cells after oral administration, being bound to carbonic anhydrase II (CA II) like its parent steroidal sulfamate ester E2MATE and thus avoiding first pass metabolism.[8] The X-ray crystal structure of the drug bound to CAII has been determined.[9]

In 2004 Sterix Ltd was acquired by Ipsen and Irosustat continued in development through formal academic-industry partnerships by Ipsen with the University of Bath and Imperial College. The drug reached phase II clinical trials in women with hormone-dependent breast cancer and endometrial cancer prior to the discontinuation of its initial development by Ipsen as a monotherapy for endometrial cancer in women with advanced/metastatic or recurrent estrogen-receptor positive endometrial cancer after a futility analysis of trial data.[3][10] Results published in 2017 showed clinical activity and a good safety profile for Irosustat, with 36% of patients on Irosustat alive without progression at 6 months; 11% showed responses and there was more stable disease noted (47%) compared to the current therapy (32%), the progestin megestrol acetate (MA).[11] However, overall there were no statistically significant differences between Irosustat and the current standard of care MA in response and survival rates. It also reached a phase I trial in the USA for prostate cancer, being safe and well-tolerated in male patients with castration-resistant prostate cancer and ongoing androgen deprivation therapy. Pharmacodynamic proof of concept was demonstrated with Irosustat effecting nearly complete STS inhibition at three doses and in all patients there was notable suppression of endocrine parameters.[12] The development of Irosustat has continued with clinical trials overseen by CRUK designed to explore its activity in early breast cancer (IPET trial) [13] and also in combination with an aromatase inhibitor (AI) (IRIS trial).[14] The multicentre IRIS trial, an open-label phase II clinical study, explored the clinical value of adding an STS inhibitor in addition to a first-line AI in patients with advanced breast cancer and enrolled postmenopausal women with ER+ locally advanced or metastatic breast cancer who had benefited from a first-line AI but were subsequently progressing. The IPET trial was a pre-surgical window-of-opportunity study, assessing Irosustat for the first time in ER+ early breast cancer and recruiting postmenopausal women with untreated early disease. Importantly, these data are the first to demonstrate clinical activity of Irosustat in early breast cancer, albeit in a small patient population. The results of both trials were published in 2017, showing evidence of clinical benefit and underpinning the scientific concept of STS inhibition. Larger studies are now required. Further clinical development continues and the current status was reviewed in 2018.[15]

See also

in patients.

  • Steroid sulfatase § Inhibitors

References
  1. Palmieri C, Januszewski A, Stanway S, Coombes RC (2011). "Irosustat: a first-generation steroid sulfatase inhibitor in breast cancer". Expert Rev Anticancer Ther. 11 (2): 179–83. doi:10.1586/era.10.201. PMID 21342037.
  2. Thomas M P, Potter B V L (2015). "Discovery and Development of the Aryl O-Sulfamate Pharmacophore for Oncology and Women's Health". J. Med. Chem. 58 (19): 197634–7658. doi:10.1021/acs.jmedchem.5b00386. PMC 5159624. PMID 25992880.
  3. "Irosustat - AdisInsight".
  4. Woo LW, Purohit A, Malini B, Reed MJ, Potter BV (2000). "Potent active site-directed inhibition of steroid sulphatase by tricyclic coumarin-based sulphamates". Chemistry & Biology. 7 (10): 773–791. doi:10.1016/S1074-5521(00)00023-5. PMID 11033081.
  5. Woo, L W L, Ganeshapillai D, Thomas M P, Sutcliffe O B, Malini B, Mahon M F, Purohit A & Potter B V L Structure-Activity Relationship of the Clinical Steroid Sulfatase Inhibitor Irosustat (STX64, BN83495). (2011). "Structure-Activity Relationship of the Clinical Steroid Sulfatase Inhibitor Irosustat (STX64, BN83495)". ChemMedChem. 6 (11): 2019–2034. doi:10.1002/cmdc.201100288. PMC 3262147. PMID 21990014.
  6. Stanway, S, Purohit A, Woo L W L, Sufi S, Vigushin D, Ward R, Wilson R, Stanczyk F Z, Dobbs N, Kulinskaya E, Elliott M, Potter B V L, Reed M J and Coombes R C (2006). "Phase I study of STX64 (667 Coumate) in breast cancer patients: the first study of a steroid sulphatase inhibitor". Clin Cancer Res. 12 (5): 1585–1592. doi:10.1158/1078-0432.CCR-05-1996. PMID 16533785.
  7. Coombes RC, Cardoso F, Isambert N, Lesimple T, Soulié P, Peraire C, Fohanno V, Kornowski A, Ali T, Schmid P (2013). "A phase I dose escalation study to determine the optimal biological dose of irosustat, an oral steroid sulfatase inhibitor, in postmenopausal women with estrogen receptor-positive breast cancer". Breast Cancer Res. Treat. 140 (1): 73–82. doi:10.1007/s10549-013-2597-8. PMID 23797179.
  8. Ireson, C R, Chander S K, Purohit A, Parish D C, Woo L W L, Potter B V L & Reed M J (2004). "Pharmacokinetics of the nonsteroidal steroid sulphatase inhibitor 667 COUMATE and its sequestration into red blood cells in rats". Br. J. Cancer. 91 (7): 1399–1404. doi:10.1038/sj.bjc.6602130. PMC 2409900. PMID 15328524.
  9. Lloyd, M D, R L Pederick, R Natesh, L W L Woo, A Purohit, M J Reed, K R Acharya & B V L Potter (2005). "Crystal structure of human carbonic anhydrase II at 1.95 Å resolution in complex with 667-Coumate, a novel anti-cancer agent". Biochem. J. 385 (Pt 3): 715–720. doi:10.1042/BJ20041037. PMC 1134746. PMID 15453828.
  10. Carmen Avendano; J. Carlos Menendez (11 June 2015). Medicinal Chemistry of Anticancer Drugs. Elsevier Science. pp. 105–. ISBN 978-0-444-62667-7.
  11. Pautier P, Vergote I, Joly F, Melichar B, Kutarska E, Hall G, Lisyanskaya A, Reed N, Oaknin A, Ostapenko V, et al. (2017). "A phase 2, randomized, open-label study of Irosustat versus megestrol acetate in advanced endometrial cancer". International Journal of Gynecological Cancer. 27 (2): 258–266. doi:10.1097/IGC.0000000000000862. PMID 27870712.
  12. Denmeade, S, George D, Liu G, Peraire C, Geniaux A, Baton F, Ali T & Chetaille (2011). "2011 A phase I pharmacodynamics dose escalation study of steroid sulphatase inhibitor Irosustat in patients with prostate cancer". European Journal of Cancer. 47: S499. doi:10.1016/S0959-8049(11)71998-0.
  13. Palmieri C, Szydlo R, Miller M, Barker L, Patel NH, Sasano H, Barwick T, Tam H, Hadjiminas D, Lee J, et al. (2017). "IPET study: an FLT-PET window study to assess the activity of the steroid sulfatase inhibitor irosustat in early breast cancer". Breast Cancer Res. Treat. 166 (2): 527–539. doi:10.1007/s10549-017-4427-x. PMC 5668341. PMID 28795252.
  14. Palmieri C, Stein RC, Liu X, Hudson E, Nicholas H, Sasano H, Guestini F, Holcombe C, Barrett S, Kenny L, et al. (2017). "IRIS study: a phase II study of the steroid sulfatase inhibitor Irosustat when added to an aromatase inhibitor in ER-positive breast cancer patients". Breast Cancer Res. Treat. 165 (2): 343–353. doi:10.1007/s10549-017-4328-z. PMC 5543190. PMID 28612226.
  15. Potter, BVL (2018). "SULFATION PATHWAYS: Steroid Sulfatase Inhibition by Aryl Sulfamates: Clinical Progress, Mechanism, and Future Prospects". J Mol Endocrinol. 61 (2): T233–T252. doi:10.1530/JME-18-0045. PMID 29618488.
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