In a prospective, dose ranging, feasibility study, Carr et al (2013) evaluated the 12-month safety and potential efficacy of autologous muscle derived cells (Cook MyoSite Incorporated, Pittsburgh, PA) as therapy for SUI. A total of 38 women in whom SUI had not improved with conservative therapy for 12 or more months underwent intra-sphincter injection of low-doses (1, 2, 4, 8 or 16 × 10(6)) or high-doses (32, 64 or 128 × 10(6)) of autologous muscle derived cells, which were derived from biopsies of their quadriceps femoris. All patients could elect a second treatment of the same dose after 3-month follow-up. Assessments were made at 1, 3, 6 and 12 months after the last treatment. The primary end point was the incidence and severity of adverse events. In addition, changes in SUI severity were evaluated by pad test, diary of incontinence episodes and quality of life surveys. Of the 38 patients, 33 completed the study. Treatment-related complications were limited to minor events such as pain/bruising at the biopsy and injection sites. Of patients who received 2 treatments of autologous muscle derived cells who were eligible for analysis, a higher percentage of those in the high-dose versus the low-dose group experienced a 50 % or greater reduction in pad weight (88.9 %, 8 of 9 versus 61.5 %, 8 of 13), had a 50 % or greater reduction in diary reported stress leaks (77.8 %, 7 of 9 versus 53.3 %, 8 of 15) and had 0 to 1 leaks during 3 days (88.9 %, 8 of 9 versus 33.3 %, 5 of 15) at final follow-up. The authors concluded that injection of autologous muscle derived cells in a wide range of doses appears safe with no major treatment-related adverse events reported. They stated that treatment with autologous muscle derived cells shows promise for relieving SUI symptoms and improving quality of life. Moreover, they noted that the most effective dose of cells has yet to be determined, and a placebo-controlled study powered to determine treatment efficacy is necessary. Two ongoing studies have been designed to address these issues.