Eli Lilly and partner Acrux are celebrating after regulators in the USA gave the green light to their underarm testosterone solution Axiron.

The US Food and Drug Administration  has approved Axiron topical solution for replacement therapy in men over 18 for certain conditions associated with a deficiency or absence of testosterone. It is the first such treatment approved for application via an armpit applicator.

David Ricks, president of Lilly USA, said the company is "proud to expand our focus in men's health," as it already markets the erectile dysfuncrtion drug Cialis (tadalafil). It has been estimated that up to 13 million men over 45 in the USA may have symptoms associated with low testosterone and the testosterone therapy market across the Atlantic is worth around $1 billon, growing at 20% per annum.

The FDA approval is particularly good news for Acrux, which says it has joined "a select group of Australian companies" to get a regulatory thumbs-up. The Melbourne-based company, whose shares have hit record levels, licensed Axiron to Lilly in March and received an upfront fee of around $53 million.

Acrux will now pocket $87 million following the FDA approval and may receive up to $195 million in commercialisation milestones, as well as royalties.