{"entity":{"id":"srd5a2","kind":"target","name":"5-alpha-reductase type 2 (SRD5A2)","aka":[],"tldr":"5-alpha-reductase turns testosterone into the more potent dihydrotestosterone inside the prostate; finasteride and dutasteride block it, and two large trials showed they cut prostate cancer diagnoses by about a quarter while raising concern about high-grade tumours.","summary":"Steroid 5-alpha-reductase type 2 converts testosterone to dihydrotestosterone, the androgen that drives prostate growth. Finasteride (type 2 selective) and dutasteride (types 1 and 2) are approved for benign prostatic enlargement and were tested for prevention in the Prostate Cancer Prevention Trial and the REDUCE trial, where they reduced the overall incidence of prostate cancer but were associated with a small excess of high-grade cancers, so neither is approved for prevention. In castration-resistant prostate cancer, tumour cells raise their own 5-alpha-reductase and other steroidogenic enzymes to make androgens, part of the rationale for abiraterone and the newer androgen receptor blockers.","asOf":"2026-09-04","wikipedia":"https://en.wikipedia.org/wiki/SRD5A2","links":[{"label":"UniProt P31213: SRD5A2","url":"https://www.uniprot.org/uniprotkb/P31213/entry"},{"label":"HGNC:11285 SRD5A2","url":"https://www.genenames.org/data/gene-symbol-report/#!/hgnc_id/HGNC:11285"},{"label":"ChEMBL target CHEMBL1856","url":"https://www.ebi.ac.uk/chembl/explore/target/CHEMBL1856"}],"tags":["chembl-gap"],"related":["androgen-receptor","cyp17a1"],"cancers":["prostate"],"sections":[],"technologies":[],"targets":[],"drugs":["abiraterone"],"companies":[],"institutions":[],"pathways":[],"terms":[],"trials":[],"people":[],"bottlenecks":[],"keyPapers":[],"journals":[],"dependsOn":[],"notes":[],"symbol":"SRD5A2","role":[],"sources":[],"specificity":"tumour-associated","distribution":"one-type","specificityNote":"Tumour-associated overexpression: HPA finds the RNA group enriched in cancer (Liver Hepatocellular Carcinoma (TCGA), Prostate Adenocarcinoma (TCGA)) and group enriched in normal epididymis, fallopian tube, liver, prostate, so the tumour and the normal tissue it comes from share the target and the medicine relies on the difference in level. HPA SRD5A2: RNA group enriched (epididymis 22 nTPM, fallopian tube 19 nTPM, liver 57 nTPM); no normal tissue stained high. Distribution: 1 cancer family in the corpus carries a prevalence row, label threshold or catalogue link for it (Prostate cancer); Open Targets associates it with 3 specific cancer types at or above 0.5 (benign prostatic hyperplasia, prostate carcinoma, prostate cancer); the corpus evidence decides and the Open Targets list is quoted for comparison. (Rule 7 of scripts/fetch-target-specificity.ts.)","specificitySources":[{"label":"Human Protein Atlas SRD5A2 tissue","url":"https://www.proteinatlas.org/ENSG00000277893-SRD5A2/tissue","note":"RNA tissue and blood lineage specificity, normal tissue antibody staining (version 25.1, CC BY-SA 3.0)"},{"label":"Human Protein Atlas SRD5A2 pathology","url":"https://www.proteinatlas.org/ENSG00000277893-SRD5A2/pathology","note":"patients per staining level per cancer type (version 25.1, CC BY-SA 3.0)"},{"label":"Open Targets ENSG00000277893 associations","url":"https://platform.opentargets.org/target/ENSG00000277893/associations","note":"cancer associations at or above 0.5 (CC0)"}],"hgnc":"HGNC:11285","ensembl":"ENSG00000277893","uniprot":"P31213","entrez":"6716","firstDescribed":1991,"firstDescribedBasis":"sequence","firstDescribedNote":"Earliest sequence paper UniProt cites for the protein: Andersson et al, Nature, 1991, \"Deletion of steroid 5 alpha-reductase 2 gene in male pseudohermaphroditism\".","firstDescribedSource":"https://pubmed.ncbi.nlm.nih.gov/1944596/","biology":"A membrane enzyme of the endoplasmic reticulum in prostate, genital skin and hair follicles; it is NADPH-dependent and genetic loss causes a disorder of sex development.","whereFound":["Prostate epithelium and stroma","Castration-resistant prostate cancer cells making their own androgens"],"targetClass":"enzyme","prevalence":[{"cancerId":"prostate","pct":"host","measure":"Host enzyme in normal and malignant prostate; finasteride and dutasteride were tested for prevention, not as a tumour marker","source":"https://www.cancer.gov/types/prostate/hp/prostate-prevention-pdq"}]},"route":"/targets/srd5a2/","neighbours":{"target":[{"id":"androgen-receptor","kind":"target","name":"Androgen receptor","route":"/targets/androgen-receptor/"},{"id":"cyp17a1","kind":"target","name":"CYP17A1 (17-alpha-hydroxylase/17,20-lyase)","route":"/targets/cyp17a1/"}],"cancer":[{"id":"prostate","kind":"cancer","name":"Prostate cancer","route":"/cancers/prostate/"}],"drug":[{"id":"abiraterone","kind":"drug","name":"Abiraterone acetate","route":"/drugs/abiraterone/"}]}}