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Missense mutations in the polymerase epsilon (POLE) gene have been reported to generate proofreading defects resulting in an ultramutated genome and sensitize tumors to checkpoint blockade immunotherapy. However, many POLE mutated tumors do not respond to such treatment. To better understand the link between POLE mutation variants and response to immunotherapy, we. prospectively assessed the efficacy of nivolumab in a multicenter clinical trial in patients bearing advanced mismatch repair proficient POLE-mutated solid tumors. We found that only tumors harboring selective POLE pathogenic mutations in the DNA binding or catalytic site of the exonuclease domain presented high mutational burden with specific single base substitution signature, high T-cell infiltrates, and high response rate to anti-PD1 monotherapy. This study illustrates how specific DNA repair defects can sensitize to immunotherapy, POLE proofreading deficiency representing a novel tumor agnostic biomarker for response to PD-1 checkpoint blockade therapy.

11520 Background: AcSé Pembrolizumab is a Phase 2, non-randomized parallel arms, open-label, multicentric study from Unicancer investigating the efficacy and safety of pembrolizumab monotherapy in different cohorts of patients with rare cancers (NCT03012620). Here we report the results of pembrolizumab in the rare sarcoma cohort. Methods: Selected histotypes were all rare sarcomas patients (pts) (incidence < 0.2/100,000/year). Main inclusion criteria were age > 18, ECOG PS≤1 and advanced or metastatic disease resistant to standard treatment. Patients received pembrolizumab 200 mg IV as a 30-minute infusion on Day 1 of every 21-day cycle for a maximum of 2 years. The primary endpoint was the confirmed objective response rate according to RECIST v1.1 at 12 weeks. Secondary endpoints included clinical benefit rate, duration of response, progression-free survival (PFS), overall survival (OS), and safety. Five groups of pts were distinguished, namely chordoma, alveolar soft-part sarcoma (ASPS), desmoplastic small round cell tumor (DSRCT), smarca4 deficient malignant rhabdoid tumor (SMRT), and other histotypes. Results: 98 patients including 34 with chordoma, 14 ASPS, 11 SMRT, 8 DSCRT and 31 with other histotypes, were included from July 2017 to December 2020. The median number of cycles was 5 (range, 1 to 35) with 78 (79.6%) patients who discontinued the trial after a median of 4 cycles. There were 6 (7.3%) partial response (PR) at 12 weeks. The best response was CR in 1 patient (1%), PR in 14 patients (14.3%), and stable disease (SD) in 33 (33.7%). Median duration of response was 8.2 months [IQR, 4.1 to 9.0]. The occurrence of best response depended on the histotype, with 3 (8.8%) responses in chordoma, 7 (50%) in ASPS, 3 (27%) in SMRT, 1 (12.5%) in DSCRT and 1 (3.2%) in other histotypes (p = 0.0011). At the data cut off, median PFS was 2.75 months, and median OS was 19.7 months on the overall population. Outcomes differed according to the histotype group, with the 12 months PFS rates at 31.2% (chordoma), 35.7% (ASPS), 18.2% (SMRT), 0% (DSCRT) and 3.3% (other), respectively (p < 0.0001), and median PFS at 6.6 (chordoma), 7.5 (ASPS), 1.1 (SMRT), 2.1 (DSCRT) and 2.1 months (other), while 1-year OS rates were 76.6% (chordoma), 85.7% (ASPS), 36.4% (SMRT), 17.5% (DSCRT) and 42.9% (other) with median OS only reached for SMRT (2.4 months), DSRCT (10 months), and the other histotype group (7.1 months) (p = 0.004). The side effect profile of pembrolizumab was similar to other tumor type. Conclusions: Pembrolizumab is safe and well tolerate in this pop od STS pts, AcSé study reports high levels response rate and prolonged activity in selected subtypes of rare sarcomas. Clinical trial information: NCT03012620.

Background The AcSé-crizotinib program provides extensive screening of crizotinib-targeted genomic alteration in several malignancies. We here report the results in patients with esogastric MET-amplified adenocarcinomas. Objective The objective of the study was to evaluate the efficacy and tolerability of crizotinib in patients with pretreated esogastric MET-amplified adenocarcinoma who have no alternative treatment options. Patients and Methods MET expression was evaluated by fluorescence in situ hybridization in tumor samples with immunohistochemistry scores ≥ 2+. Patients with chemo-refractory tumors showing ≥ 6 MET copies were eligible for crizotinib 250 mg twice daily. The primary efficacy outcome was the objective response rate after two cycles of crizotinib. Results MET was prospectively analyzed in 570 esogastric adenocarcinomas. Amplifications were found in 35/570 adenocarcinomas (29/523 gastric and 6/47 esophageal). Nine patients were treated with crizotinib. The objective response rate after two cycles was 33.3% (95% CI 7.5-70), the best overall response rate was 55.6% (95% CI 21.2-86.3), with median progression-free survival of 3.2 months (95% CI 1.0-5.4), and overall survival of 8.1 months (95% CI 1.7-24.6). Safety was consistent with that previously reported for crizotinib. Conclusions Large-scale screening for MET-amplified esogastric adenocarcinomas is feasible. MET amplification was observed in 5.5% of gastric and 12.8% of esophageal adenocarcinomas. Crizotinib shows encouraging results in selected patients. Thus, c-MET inhibition for MET-amplified tumors deserves further evaluation. Trial Registration Number NCT02034981.

Background: AcSé Pembrolizumab is a Phase 2, open-label, single-arm, multi-cohort, multicentric study investigating the efficacy and safety of pembrolizumab monotherapy in patients with advanced rare cancers (NCT03012620). Here, we report the first results of Pembrolizumab in the cohort of Primary Central Nervous System Lymphoma (PCNSL). Methods: Main inclusion criteria were: relapsed or refractory PCNSL after one or several lines of treatment including high dose Methotrexate based chemotherapy, pathologically confirmed diffuse large B cell lymphoma, age&gt;18, HIV negative, concurrent steroid medication at a dose no greater than prednisone 20 mg/day or equivalent. Patients received pembrolizumab 200 mg IV as a 30-minute infusion on Day 1 of every 21-day cycles for a maximum of 2 years. The primary endpoint was the confirmed objective response rate according to IPCG at 84 day after the start of treatment. Secondary endpoints included best response (ORR), duration of response, progression-free survival (PFS), overall survival (OS), and safety. Analysis used all enrolled patients. Results: 50 patients suffering from PCNSL, including 9 primary vitreoretinal lymphoma (PVRL) were included from July, 2017 to October, 2019. Median age was 72 years (range: 43 to 83), Median PS (ECOG) was 1 (range 0-1). The median number of cycles was 4 (range 1-35). At 84 days from start of treatment, 6 patients responded (4 CR+2PR). Overall, 3 patients whose response was not assessed were considered as failures, and the rates of ORR (CR+PR), stable disease (SD), progressive disease (PD) were 26% (13/50, 8 CR + 5 PR), 10% (5/50), 58% (29/50), respectively. ORR was 29% (12/41) and 11% (1/9) in primary cerebral lymphoma and PVRL respectively. After a median follow-up of 6.7 months (range 0.2-27.4), median PFS was 2.6 months, with 6-month PFS of 29.8% and 6-month OS of 60.4%. In responders, median duration of response was estimated at 10 months (95%CI, 2.7 to 12.5). Grade III and IV toxicities related to the drug were observed in 4 patients (8%) and one patient (2%) respectively. No related toxic death was reported. Conclusion: Pembrolizumab shows moderate activity in relapsed/ refractory PCNSL with acceptable toxicity, supporting further studies evaluating its use in combination therapies. Disclosures Hoang-Xuan: BTG: Consultancy, Research Funding. Houot:Bristol-Myers Squibb: Honoraria; MSD: Honoraria; Gilead: Honoraria; Kite: Honoraria; Roche: Honoraria; Novartis: Honoraria; Janssen: Honoraria; Celgene: Honoraria. Schmitt:Celgene: Membership on an entity's Board of Directors or advisory committees; Roche, Janssen: Honoraria. Ahle:Roche: Honoraria; Novartis: Honoraria; Biogene: Honoraria; Abbvie: Honoraria; Sanofi: Honoraria. Bories:Abbvie: Consultancy; Celgen: Consultancy; Gilead: Consultancy; BMS: Honoraria; Novartis: Honoraria. Houillier:BTG: Consultancy.