The data suggest that the slow rate of release of XMT-1191 from the polymer conjugate XMT-1107 provided a low but consistent exposure to the highly active XMT-1191 small molecule , providing an apparent half life of 22 hours compared with a half life of less than five minutes with free XMT-1191 administration.The data are consistent with the significantly higher in vivo activity seen for XMT-1107 relative to XMT-1191 in xenograft activity reported in a separate poster .