Androstenediol, or 5-androstenediol (abbreviated as A5 or Δ5-diol), also known as androst-5-ene-3β,17β-diol, is an endogenous weak androgen and estrogen steroid hormone and intermediate in the biosynthesis of testosterone from dehydroepiandrosterone (DHEA).

Androstenediol is a direct metabolite of the most abundant steroid produced by the human adrenal cortex, DHEA.

[6] Its potential use as a radiation countermeasure was developed by the Armed Forces Radiobiology Research Institute (AFRRI) and subsequently studied by AFRRI and Hollis-Eden Pharmaceuticals under the proposed brand name Neumune for the treatment of acute radiation syndrome.

[8] Hollis-Eden had applied for a contract from the U.S. Government under the BioShield Request for Proposals (RFP) for radiation countermeasures.

After being encouraged for 2.5 years that Neumune was in the competitive range, on March 9, 2007, the RFP was canceled by HHS.