# SRD5A1

Source: https://onco.cc/targets/srd5a1/  
OnCo record `srd5a1` (Target). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

SRD5A1 (3-oxo-5-alpha-steroid 4-dehydrogenase 1) is an enzyme. The public catalogues list it as a drug target, and an approved or late-stage drug is recorded against it. Tied to Prostate cancer.

## Summary

Catalyses the irreversible stereospecific reduction of the delta 4,5 bond (double bond between carbons 4 and 5) of various 3-oxo steroids (3-keto steroids) producing their 5alpha dihydro-3-oxo forms. Converts testosterone into 5-alpha-dihydrotestosterone (DHT), a more potent androgen as it is the preferred ligand for androgen receptor (AR) transactivation, making this reaction a key step in male sexual differentiation during development. Besides testosterone, it can also act on other steroids, including progesterone, androstenedione, and corticoids, producing metabolites with diverse roles.

Open Targets scores its association with cancer at 0.61 (direct and indirect evidence; datatypes literature 0.82, genetic association 0.03, clinical 0.96).

## Fields

- Kind: Target
- Last checked: 2026-09-23
- Also known as: steroid 5 alpha-reductase 1; 3-oxo-5-alpha-steroid 4-dehydrogenase 1
- Tags: cancer-genes-wave
- Symbol: SRD5A1
- Class: enzyme
- Biology: Catalyses the irreversible stereospecific reduction of the delta 4,5 bond (double bond between carbons 4 and 5) of various 3-oxo steroids (3-keto steroids) producing their 5alpha dihydro-3-oxo forms. Converts testosterone into 5-alpha-dihydrotestosterone (DHT), a more potent androgen as it is the preferred ligand for androgen receptor (AR) transactivation, making this reaction a key step in male sexual differentiation during development. Besides testosterone, it can also act on other steroids, including progesterone, androstenedione, and corticoids, producing metabolites with diverse roles. Hence, it plays a central role in sexual differentiation and androgen physiology. Location: Microsome membrane; Endoplasmic reticulum membrane (UniProt). Locus 5p15.31 (HGNC).
- Where found: Prostate cancer: Open Targets association 0.60 with prostate cancer (MONDO_0008315)

## Notes

- Written by scripts/fetch-cancer-genes.ts from CIViC, Open Targets, IntOGen, HGNC and UniProt; the function text is UniProt's, condensed and in UK spelling. Roles: Open Targets known-drug datatype score 0.96. Evidence tier "approved-drug" is the strongest of those signals.
- Prevalence not recorded: none of the sources gives a positivity rate.

## Sources

- HGNC HGNC:11284: https://www.genenames.org/data/gene-symbol-report/#!/hgnc_id/HGNC:11284
- UniProt P18405: https://www.uniprot.org/uniprotkb/P18405/entry
- NCBI Gene 6715: https://www.ncbi.nlm.nih.gov/gene/6715
- Ensembl ENSG00000145545: https://www.ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000145545

## Connected records

- collections: [Open Targets Platform](https://onco.cc/collections/open-targets/)
- cancers: [Prostate cancer](https://onco.cc/cancers/prostate/)

---
JSON: https://onco.cc/api/v1/entities/srd5a1.json