Discontinuations because of AEs/deaths and for other reasons were proportionally higher for EFV than for RPV for both genders, and therefore overall there were no observed gender-related differences in the proportion of responders. Where

gender differences in response rate to ARV regimens have been observed, in most cases the cause has not been an inherent PLX4032 chemical structure difference in antiviral activity of ARVs in men and women. In the CASTLE study, the lower response rate in women compared with men was driven by discontinuations for reasons other than virological failure, and no difference in response rate was observed in the on-treatment analysis [1]. Similarly, a small, albeit nonsignificant, difference in response rate between women and men in the gender, race, and clinical experience (GRACE), study of darunavir/ritonavir was attributable to a higher discontinuation rate in women [17]. Reasons for the higher discontinuation GKT137831 rate appear complex but have included poorer adherence, pregnancy, and a higher incidence of some gastrointestinal AEs in women than in men [1, 17]. In contrast, discontinuation rates in ECHO and THRIVE were similar for men and women; this was particularly apparent in the RPV groups. The difference in response rates according to race, which was observed in both the RPV and EFV treatment groups, is consistent with the findings

of several trials with other ARVs which also observed lower response rates in Black, compared with Asian and White, patients [3, 5, 9-13]. In this study, the lower responses in Black patients were mainly a result of a higher frequency of virological failure and treatment discontinuation for reasons such as loss to follow-up, noncompliance and withdrawal of consent, compared with Asian and White patients. Of note, in both treatment groups, the proportion of Black patients who reported > 95% adherence was lower than for the Fenbendazole other racial groups, which could explain the higher virological failure rate in Black

patients. In other studies, a relationship has been observed between adherence and a lower virological response to ARV regimens in Black patients [5, 12], while one study has suggested that a higher virological failure rate in such patients could not be explained by lower adherence or socio-demographic factors [13]. Another study was designed to equalize variables such as access to care and study drugs between all participants, but the authors were not able to account for the socioeconomic and other differences that they believed led to more Black patients discontinuing than other patients and the resulting lower response rate in these patients [10]. Patients had substantial mean increases in CD4 cell counts at week 48 in both treatment groups, irrespective of gender or race.