Allergan has reported mixed top-line data from a mid-stage trial testing Botox as a treatment for major depressive disorder (MDD), but says the results are “encouraging” and warrant a move into Phase III development.

The Phase II study evaluated the efficacy, safety and tolerability of a single administration of two different doses of Botox (30 units or 50 units) relative to placebo in adult females with MDD over duration of up to 24 weeks.

According to the data, the lower dose of the drug demonstrated numerical superior efficacy in the Montgomery-Asberg Depression Scale (MADRS) score compared to placebo; the treatment (LS mean) difference for 30 U being -4.2 at 3 weeks (p- value 0.005), -3.7 at week 6 (p-value 0.053; the primary endpoint), and -3.6 at week 9 (p-value 0.049).

The 50 U dose of Botox failed to demonstrate superior efficacy over placebo (LS mean difference was 1.3) on the MADRS score.

Secondary efficacy variables (CGI-S and HAMD-17) showed numerically superior efficacy over placebo and trended in the same direction as the primary efficacy variable for the 30 U but not the 50 U dose, the firm said, but noted that both were well tolerated in patients.

"We are encouraged by these data and the potential impact on adults with major depressive disorder. Given our in-depth and extensive clinical trial experience in CNS including depression, we plan to move forward and develop a phase III program for  a potential new treatment option for patients," said David Nicholson, chief research and development officer at Allergan.

Botox’ indications already approved include chronic migraine, overactive bladder, severe underarm sweating, eyelid spasms and limb spasticity.