OncoSignal
Live from Open Targets Platform, fetched 2026-11-12 01:06 UTC. Every row links to its source record.

CYP19A1 cytochrome P450 family 19 subfamily A member 1

ENSG00000137869 · protein coding · Open Targets profile

A cytochrome P450 monooxygenase that catalyzes the conversion of C19 androgens, androst-4-ene-3,17-dione (androstenedione) and testosterone to the C18 estrogens, estrone and estradiol, respectively (PubMed:27702664, PubMed:2848247). Catalyzes three successive oxidations of C19 androgens: two conventional oxidations at C19 yielding 19-hydroxy and 19-oxo/19-aldehyde derivatives, followed by a third oxidative aromatization step that involves C1-beta hydrogen abstraction combined with cleavage of the C10-C19 bond to yield a phenolic A ring and formic acid (PubMed:20385561). Alternatively, the third oxidative reaction yields a 19-norsteroid and formic acid. Converts dihydrotestosterone to delta1,10-dehydro 19- nordihydrotestosterone and may play a role in homeostasis of this potent androgen (PubMed:22773874). Also displays 2-hydroxylase activity toward estrone (PubMed:22773874). Mechanistically, uses molecular oxygen inserting one oxygen atom into a substrate, and reducing the second into a water molecule, with two electrons provided by NADPH via cytochrome P450 reductase (CPR; NADPH-ferrihemoprotein reductase) (PubMed:20385561, PubMed:22773874). {ECO:0000269|PubMed:20385561, ECO:0000269|PubMed:22773874, ECO:0000269|PubMed:27702664, ECO:0000269|PubMed:2848247}.

6 of the 6 drugs recorded against CYP19A1 are approved

Each band is a group of drugs. It runs from the kind of drug on the left to the furthest stage that drug has reached in any disease on the right. Thicker bands mean more drugs.

6 small molecule drugs at Approved: TESTOLACTONE, FADROZOLE, AMINOGLUTETHIMIDE, LETROZOLE, ANASTROZOLE, EXEMESTANESmall molecule 6Approved 6

Approved bands are highlighted. Withdrawn means the drug was pulled from the market or from development. A combined phase counts as the later one (Phase 1/2 is shown as Phase 2). Hover a band for the drug names. Source: Open Targets Platform, fetched live.

In 4 of 15 cancers, the evidence for CYP19A1 comes mainly from inherited variants

Each row is a cancer, strongest overall evidence first. The two dots show how strong the inherited (germline) and tumour-mutation (somatic) evidence is; the line between them is the gap.

Inherited (germline) variantsMutations in tumours (somatic)
00.250.50.751breast cancerbreast cancerbreast carcinomabreast carcinomaendometrial carcinomaendometrial carcinomaendometrial carcinoma: germline 0.68endometrial cancerendometrial cancerendometrial cancer: germline 0.66ovarian carcinomaovarian carcinomamalignant epithelial tumor of ovarymalignant epithelial tumor of ovaryestrogen-receptor positive breast cancerestrogen-receptor positive breast cancerductal breast carcinoma in situductal breast carcinoma in situendometrial endometrioid carcinomaendometrial endometrioid carcinomaendometrial endometrioid carcinoma: germline 0.49primary peritoneal carcinomaprimary peritoneal carcinomafallopian tube cancerfallopian tube cancerbreast adenocarcinomabreast adenocarcinomauterine canceruterine canceruterine cancer: germline 0.45estrogen-receptor negative breast cancerestrogen-receptor negative breast canceratypical endometrial hyperplasiaatypical endometrial hyperplasia

Scores run from 0 (no evidence) to 1 (strongest). A missing dot at 0 means Open Targets holds no evidence of that kind. Source: Open Targets Platform, fetched live.

Tractability

Small molecule
Approved Drug, Structure with Ligand, High-Quality Ligand, Druggable Family
Antibody
UniProt SigP or TMHMM
PROTAC
Small Molecule Binder

gnomAD loss of function constraint: o/e 0.7206400036811829 (upper bound 0.9679700136184692). Low values mean loss of function is poorly tolerated, a safety flag for inhibition.

Who runs trials of these drugs

Principal investigators and study chairs on 400 registry trials, updated in the last three years, of the most advanced drugs against CYP19A1 (testolactone, fadrozole, aminoglutethimide, letrozole, anastrozole, exemestane), ranked by Phase 2+ trials. Live from ClinicalTrials.gov.

107 of 376 trials of drugs against CYP19A1 have sites only in United States

Registry trials of testolactone, fadrozole, aminoglutethimide, letrozole, anastrozole, exemestane updated in the last three years, counted by the country group of their listed sites. A trial with sites in several groups counts in each; 270 of 376 have all sites in one country.

Sites only in this groupSites here and elsewhere
United StatesUnited States: 107 trials with sites only hereUnited States: 87 trials with sites here and elsewhere194ChinaChina: 61 trials with sites only hereChina: 33 trials with sites here and elsewhere94EuropeEurope: 56 trials with sites only hereEurope: 76 trials with sites here and elsewhere132JapanJapan: 4 trials with sites only hereJapan: 38 trials with sites here and elsewhere42OtherOther: 56 trials with sites only hereOther: 86 trials with sites here and elsewhere142

Site counts are not patients per country, and trials registered only outside ClinicalTrials.gov are not covered. Where sites are is a fact about the record, not a judgement of its quality. Europe is the EU and EEA, the UK and Switzerland. 24 trials list no sites and are left out. Source: ClinicalTrials.gov, fetched live.

165 trials of drugs against CYP19A1 were stopped early; 19 give no reason

Terminated, withdrawn and suspended interventional trials of testolactone, fadrozole, aminoglutethimide, letrozole, anastrozole, exemestane, newest update first, live from ClinicalTrials.gov. Each reason is quoted exactly as the registry gives it; we do not sort reasons into safety, efficacy or business. Dates are the last registry update. Showing the 25 most recent of 165.

  • suspended · 2026-09-02 · Alliance for Clinical Trials in Oncology · Anastrozole, Letrozole, Exemestane
    “Amending protocol to increase sample size”
  • terminated · 2026-07-10 · Novartis Pharmaceuticals · Letrozole
    “Novartis terminated the trial early because the collected data were sufficient to perform the analysis stated for the primary endpoint.”
  • terminated · 2026-06-25 · SOLTI Breast Cancer Research Group · Ribociclib + Letrozole OR Fulvestrant, Palbociclib + Letrozole OR Fulvestrant
    “The study was prematurely halted because enrollment was significantly delayed compared with the original projections due to the evolving therapeutic landscape.”
  • withdrawn · 2026-06-22 · Novartis Pharmaceuticals · Letrozole
    “Business decision”
  • terminated · 2026-06-04 · University of Washington · Letrozole
    “Study ended earlier than anticipated due to end of funding.”
  • terminated · 2026-05-14 · EQRx, Inc. · Lerociclib + Letrozole or Fulvestrant
    “The study is being closed based on corporate changes at EQRx and is not related to any efficacy or safety issues with lerociclib.”
  • terminated · 2026-04-28 · OHSU Knight Cancer Institute · Exemestane, Letrozole
    “Loss of support.”
  • terminated · 2026-04-15 · University of Maryland, Baltimore · Anastrozole, Letrozole
    “This study was terminated due to slow accrual, and this due to the changing practice patterns, and difficulties with insurance coverage for some of the study related tests, such as OncotypeDx.”
  • terminated · 2026-04-09 · Peking Union Medical College Hospital · matched by the registry's drug synonyms
    “Results failed to achieve the anticipated effect.”
  • terminated · 2026-02-24 · Sanofi · Anastrozole, Letrozole, Exemestane
    “Sponsor decision to prematurely stop the study, not linked to any safety concern.”
  • withdrawn · 2026-02-12 · Danish Breast Cancer Cooperative Group · matched by the registry's drug synonyms
    “Lack of funding”
  • terminated · 2025-12-18 · Mario Negri Institute for Pharmacological Research · Anastrozole 1mg
    “Low enrolment rate”
  • terminated · 2025-12-15 · Fudan University · Letrozole 2.5mg
    “No enough participants”
  • terminated · 2025-09-18 · Sanofi · Letrozole
    “early discontinuation based on strategic sponsor decision not driven by any safety concerns”
  • terminated · 2025-09-11 · Sanofi · Letrozole, Letrozole-matching placebo
    “The study was terminated based on the review by an independent data monitoring committee of the prespecified interim analysis of the Phase 3 AMEERA-5 efficacy data. No new safety signals were observed.”
  • terminated · 2025-07-29 · University of Milano Bicocca · matched by the registry's drug synonyms
    “Difficulties in patient recruitment”
  • terminated · 2025-04-10 · Inova Health Care Services · matched by the registry's drug synonyms
    “Lack of enrollment to meet the primary and secondary study goals”
  • terminated · 2025-03-07 · Fondazione Policlinico Universitario Agostino Gemelli IRCCS · Letrozole 2.5mg
    “Logistical problems impacting the speed of enrolment”
  • terminated · 2025-01-31 · Erasme University Hospital · Letrozole
    “The study had to be terminated due to the new European legislation on drug studies. This legislation requires all studies aimed at evaluating treatments to be registered as such, even in the context of Standard of Care.”
  • withdrawn · 2025-01-13 · University of California, San Diego · Letrozole
    “study not funded in previous iteration. new clinicaltrials.gov protocol submitted for funded version of study”
  • terminated · 2024-12-27 · M.D. Anderson Cancer Center · Anastrozole, Letrozole
    “Despite modifications, accrual was poor and the closed”
  • terminated · 2024-12-24 · Albert Einstein College of Medicine · matched by the registry's drug synonyms
    “Interventional component of study terminated prior to full enrollment”
  • terminated · 2024-11-26 · Georgetown University · matched by the registry's drug synonyms
    “Sufficient accrual into the African American/Black patient cohort and insufficient accrual into the NHW patient cohort.”
  • terminated · 2024-09-03 · Pfizer · PF-06804103 + Palbociclib +Letrozole
    “The trial was terminated based on the stage in drug development and assessment of PF-06804103 relative to the leading external competition. The decision was not due to a safety concern.”
  • terminated · 2024-07-31 · Genentech, Inc. · Letrozole
    “The Sponsor discontinued the manufacturing and development of taselisib due to modest clinical benefit and limited tolerability.”
Paediatric incentives and obligations for CYP19A1's drugs

For testolactone, fadrozole, aminoglutethimide, letrozole, anastrozole, exemestane: what EMA and FDA publish about paediatric plans, orphan status and pediatric approvals, and how many registered studies take children. Each line is a yes, no or not published fact from the record linked under it; none of it is a forecast.

  • EU paediatric investigation plan: yes · EMEA-001575-PIP01-13 (anastrozole;levonorgestrel, Treatment of endometriosis): W: decision granting a waiver in all age groups for all conditions or indications, 2 May 2014; EMEA-000283-PIP-01-08 (anastrozole, Gynaecomastia;McCune-Albright syndrome;Short stature due to Growth Hormone deficiency;Testotoxicosis): P: decision agreeing on a investigation plan, with or without partial waiver(s) and or deferral(s), 6 Feb 2009; compliance positive 3 Apr 2009
    Rule: An EMA PIP decision (agreement, modification or waiver) lists the drug as its active substance, exact name. Source: EMA data download (dated snapshot), 2026-11-11
  • EU orphan designation: no · No EU orphan designation names testolactone, fadrozole, aminoglutethimide, letrozole, anastrozole, exemestane
    Rule: An EU orphan designation lists the drug as its active substance (exact name) or belongs to a medicine that does; withdrawn and expired designations are listed with their status. Source: EMA data download (dated snapshot), 2026-11-11
  • Authorised in the EU: no · EMA lists no centrally authorised medicine of testolactone, fadrozole, aminoglutethimide, letrozole, anastrozole, exemestane
    Rule: An EMA medicine record lists the drug as its active substance or INN, exact name; national-only authorisations are not in this file. Source: EMA data download (dated snapshot), 2026-11-11
  • FDA orphan designation: not published · FDA's orphan designation database turns away automated requests, so this app does not read it; search it by hand at the link
    Rule: Would be: an FDA orphan designation names the drug. Source: FDA orphan designations search
  • FDA pediatric oncology approval: no · FDA's table lists no pediatric approval of testolactone, fadrozole, aminoglutethimide, letrozole, anastrozole, exemestane
    Rule: FDA's Pediatric Oncology Drug Approvals table names the drug. Source: FDA Pediatric Oncology Drug Approvals (content current as of 2026-03-03), 2026-11-12
  • Registered studies open to children: yes · 89 interventional studies of testolactone, fadrozole, aminoglutethimide, letrozole, anastrozole, exemestane include patients under 18; 9 are recruiting, not yet recruiting or active
    Rule: The registry's age group includes Child (birth to 17 years), which also counts studies that set no minimum age. Source: ClinicalTrials.gov search, 2026-11-12

Rare pediatric disease voucher. FDA, content current as of 29 Apr 2026: “As of February 3, 2026, enactment of the Consolidated Appropriations Act, 2026, the rare pediatric disease PRV program will sunset after September 30, 2029. FDA may not award any PRVs under this program after September 30, 2029.” Voucher sale prices are not shown here; they appear only as company-reported news. FDA: Rare Pediatric Disease Designation and Priority Review Voucher Programs

All 6 drugs and clinical candidates as a table

Each drug, stage and indication links to its Open Targets record, where the trials and approvals behind it are listed. Salt forms (for example a mesylate) are listed as Open Targets records them, as separate entries.

DrugTypeHighest stageIndicationsSource records
TESTOLACTONESmall moleculeapprovalbreast cancer, congenital adrenal hyperplasia, precocious pubertyOpen Targets · ChEMBL
FADROZOLESmall moleculeapprovalbreast cancerOpen Targets · ChEMBL
AMINOGLUTETHIMIDESmall moleculeapprovalneoplasm, breast cancer, prostate cancerOpen Targets · ChEMBL
LETROZOLESmall moleculephase 4breast cancer, breast carcinoma, neoplasm, hypogonadotropic hypogonadism, hypogonadism, gender identity disorder, Infertility, polycystic ovary syndrome, +64 moreOpen Targets · ChEMBL
ANASTROZOLESmall moleculephase 4breast cancer, breast carcinoma, neoplasm, ductal breast carcinoma in situ, Infertility, Gynecomastia, Klinefelter syndrome, precocious puberty, +31 moreOpen Targets · ChEMBL
EXEMESTANESmall moleculephase 4breast cancer, breast carcinoma, neoplasm, malignant epithelial tumor of ovary, ovarian carcinoma, prostate cancer, breast neoplasm, endometrial cancer, +17 moreOpen Targets · ChEMBL