We analyzed 100 tumor samples from 44 patients (median progression free survival or PFS = 145 days; range = 84 to 489) (Table 1; Fig. 1A; Supplementary Fig. S1 and Table S1) whose melanomas developed acquired resistance to either vemurafenib or dabrafenib monotherapy....Accordingly, when treated with vemurafenib, WM2664 over-expressing PIK3R2 N561D was more resistant to BRAF inhibition compared with WM2664 introduced with the vector or wild type PIK3R2 (Fig. 3C).