Decline in skeletal muscle mass and function occurs in older men and women.Age-associated loss of muscle increases risk of functional limitations,falls,fractures,loss of independence and poor quality of life.Functional decline and loss of independence in older individuals present a huge burden on healthcare services and costs,particularly because of continued growth of aging population and lack of therapeutic options for the treatment of functional limitations associated with aging as well as chronic illness.Thus,there is an enormous unmet need for function promoting anabolic therapies that can prevent or reverse muscle loss,improve physical function and reduce the burden of disability.Testosterone supplementation increases skeletal muscle mass and maximal voluntary strength in healthy,androgen-deficient and eugonadal young and older men,and in men with many chronic disorders,such as COPD,cancer,or end-stage renal disease,etc.However,administration of supraphysiologic doses of androgens is associated with high frequency of dose-limiting adverse effects,such as erythrocytosis,prostate stimulation and leg edema.Here we describe our journey of discovery of novel tissue selective androgen receptor modulator (SARM) that achieve anabolic effects on the skeletal muscle and bone,however,unlike testosterone and other anabolic steroids,it spares growth effect on prostate and other secondary sexual organs.