{"entity":{"id":"formestane","kind":"drug","name":"Formestane","aka":["4-Hydroxyandrostenedione","4-OHA"],"tldr":"Formestane, launched in Europe in 1993, was the first selective aromatase inhibitor for advanced breast cancer, given by injection every two weeks; oral exemestane and the non-steroidal inhibitors made it redundant within a few years.","summary":"Formestane was developed by Angela Brodie's laboratory in the 1970s as the first aromatase inhibitor designed to be selective, in contrast to aminoglutethimide, and Ciba-Geigy brought it to market in the United Kingdom and other European countries in 1993 for advanced postmenopausal breast cancer after tamoxifen. It lowered oestrogen levels effectively but had to be injected because of poor oral bioavailability. Anastrozole, letrozole and the oral steroidal inactivator exemestane followed between 1995 and 1999 and displaced it; it was withdrawn from most markets in the mid-2000s. It was never approved in the United States.","status":"historic","asOf":"2026-09-08","wikipedia":"https://en.wikipedia.org/wiki/Formestane","links":[{"label":"Wikipedia","url":"https://en.wikipedia.org/wiki/Formestane"},{"label":"ChEMBL CHEMBL1201310","url":"https://www.ebi.ac.uk/chembl/explore/compound/CHEMBL1201310"}],"tags":["gap-fill","chembl-universe"],"related":[],"cancers":["breast-hr-positive"],"sections":[],"technologies":["endocrine-therapy"],"targets":["aromatase"],"drugs":["exemestane"],"companies":[],"institutions":[],"pathways":[],"terms":[],"trials":[],"people":[],"bottlenecks":[],"keyPapers":[],"journals":[],"notes":[],"brand":"Lentaron","modality":"Steroidal aromatase inactivator, fortnightly intramuscular injection","mechanism":"An androstenedione analogue that aromatase binds and converts to a reactive intermediate, permanently inactivating the enzyme that makes oestrogen.","approvals":[],"mechanismSteps":[],"toxicity":[],"access":[],"regulatoryEvents":[]},"route":"/drugs/formestane/","neighbours":{"cancer":[{"id":"breast-hr-positive","kind":"cancer","name":"HR-positive / HER2-negative breast cancer","route":"/cancers/breast-hr-positive/"}],"technology":[{"id":"endocrine-therapy","kind":"technology","name":"Endocrine therapy (SERMs, AIs, SERDs)","route":"/technologies/endocrine-therapy/"}],"target":[{"id":"aromatase","kind":"target","name":"Aromatase (CYP19A1)","route":"/targets/aromatase/"}],"drug":[{"id":"exemestane","kind":"drug","name":"Exemestane","route":"/drugs/exemestane/"}]}}