8547 Background: Since MPM is an uncommon neoplasia, its rarity has limited available data on molecular drivers. Methods: RAMES study evaluated the second-line efficacy of gemcitabine/ramucirumab treatment vs. gemcitabine/placebo. From December 2016 to July 2018 (end of enrolment), 164 patients (pts) were admitted to this study, which involved the collection of tumor samples - with diagnosis - to evaluate 34 genes by NGS (ACTB, ACTG1, ACTG2, ACTR1A, BAP1,CDH8, CDK4, CDKN2A, CDKN2B, COL3A1, COL5A2, CUL1, DHFR, GOT1, KDR, KIT, MXRA5, NF2, NFRKB, NKX6,-2, NOD2, PCBD2, PDZK1IP1, PIK3CA, PIK3CB, PSMD13, RAPGEF6, RDX, SETDB1, TAOK1, TP53,TXNRD1, UQCRC1, XRCC6). We reported the results of the first 87 pts (54%): hystotype was epithelioid in 70 pts (80%), biphasic in 14 pts (16%) and sarcomatoid in 3 pts (4%). Median age was 63 years (range 45-81). 70 pts were male (80%) and 17 pts were female (20%). In the present analysis, we included 55 pts in stage III (63%), 26 pts in stage IV (30%) and 6 pts whose stage was unknown. Median first-line PFS platinum/pemetrexed therapy was for 5.75 months (I.C. 95% 4.75-6.76). PFS was ≤6 months for 40 pts (49%), and 6 months for 41 pts (51%). Results: 187 functional somatic mutations were identified. Genomic alterations/patient were 1 gene in 29 pts (33%), 3 genes in 18 pts (21%) and ≥5 genes in 2 pts (2%). The most frequent somatic mutations were RDX in 35 pts (40%), MXRA5 in 20 pts (23%), BAP1 in 13 pts (15%) and ACTG 1 in 9 pts (11%). When patients were collated by stage, the most frequent mutations were: MXRA5 in 16 pts in stage III (29%), BAP1 in 5 pts in stage IV (19%) and RDX in 16 pts in stage IV (62%). The percentage of somatic mutations in patients with PFS as first-line chemotherapy for ≤6 and >6 months was 2.2 and 1.6 (p=0.032), respectively. The most frequent mutations/patient for ≤6 and >6 months PFS were: RDX in 14 pts (35%) with PFS < 6, RDX in 19 pts (46%) with PFS >6 and MXRA5 in 11 pts (27%) with PFS >6. Conclusions: This preliminary data suggests a possible role that a genetic signature may play in distinguishing MPM with different clinical-pathological features. The results are expected to be clarified further in the second step of the study, which is ongoing. Clinical trial information: 2016-001132-36.