Treatment with thymosin alpha-1 increases fertilizing capacity of sperm of infertile men: a multicenter trial.

Thymosin alpha-1 (T alpha 1) significantly enhances the fertilizability of sperm from fertile men by increasing capacitation and/or acrosome reaction. The present study was conducted to investigate the effect of T alpha 1 on fertilizing capacity of sperm of infertile men using the sperm penetration assay (SPA) in a multicenter clinical trial. T alpha 1 significantly (p = .0006 to < .0001) increased (31 to 45%) fertilizing capacity of sperm of 76% (50/68) of infertile men as defined by the sperm penetration index in SPA. The enhancing effect of T alpha 1 and the degree of enhancement depended on the T alpha 1 concentration in the seminal plasma, since these parameters showed a significant intercorrelation (r = .65 to .74, p = .039 to .01). It would appear that T alpha 1 may have clinical application in the diagnosis and treatment of male infertility especially mediated through defective sperm function.