Context: Polymerase epsilon (POLE) gene missense hotspot mutations can generate pathogenic (p) proofreading defects resulting in hypermutated genomic profiles. Aim: Determine the prevalence, genomic consequences and immunotherapy sensitivity of advanced POLE mutated tumors according to mutation site, primary tumor and tumor mutational burden (TMB). Results: Pan-Cancer TCGA & MSKCC databases genomic analyses found a prevalence of non-pathogenic POLE mutations (POLEnp) of 3.4% with median TMB of 11 mutations/Megabase (mt/Mb, IQR 3-34). Pathogenic POLE mutations (POLEp) prevalence was 0.4% with median TMB of 215 mt/Mb (IQR 107-324), predominantly in colorectal and endometrial cancers. Prevalence dropped to 0.1% in metastatic cancers. We assessed prospectively the efficacy of PD-1 blockade in mismatch repair proficient advanced solid tumors harboring POLE missense mutations (phase II ASCe Nivolumab trial; NCT03012581). Variants were categorized prospectively by a molecular board as POLEp, POLEnp or Variants with Unknown significance (VUS). The primary endpoint was the Overall Response Rate (ORR) at 12 weeks according to RECIST 1.1, and secondary endpoints included survival analyses according to POLE variants pathogenicity. Among 61 screened patients, 21 were eligible and 20 received Nivolumab and 19 were assessable for response (table 1). The 12-week ORR was 37% for patients harboring POLEp and VUS and resulted in major survival improvement compared to POLEnp patients (HR=0.1 ; CI95% 0.02-0.7); see results in Table 1. Among patients POLEp tumors, while higher TMB was not predictive of response, higher proportion of POLE-related mutational signature correlated with improved benefit. In silico exonucleasic POLE domain analyses confirmed that all POLEp and 2 VUS clustered in the DNA binding or the Catalytic site. Recategorizing the VUS according to the location within the exonucleasic domain improved the prediction of survival outcomes. Impact: This study gives new insights on how DNA repair defects, mutational burden and signatures sensitize to PD-1 blockade and may offer emerging tumor agnostic biomarkers for benefit to checkpoint blockade. POLE variant pathogenicity All(N=21) POLEnp(N=5) VUS(N=4) POLEp(N=12) Age, years ± SD 57 ± 16 64 ± 10 56 ± 16 54 ± 17 Sex, Male (%) 12 (57) 5 (100) 2 (50) 5 (42) PS (ECOG)=1 (%) 16 (75) 4 (80) 2 (50) 10 (83) Primary tumor Colorectal 9 (43) 2 (40) 2 (50) 5 (42) Endometrial 6 (29) 0 (0) 0 (0) 6 (50) Gastric 2 (9) 2 (40) 0 (0) 0 (0) Glial 1 (5) 0 (0) 0 (0) 1 (8) Biliary tract 1 (5) 0 (0) 1 (25) 0 (0) Pancreas 2 (9) 1 (20) 1 (25) 0 (0) Number of previous treatments 2.4 ± 2 5 ± 2 1.8 ± 1 1.5 ± 1 TMB (mt/Mb, Min-Max)(N=16) 36.2 (2-385) 5 (4-9) 3 (2-4) 114 (25-385) ORR at 12 weeks (CR+PR) 37%(N=7/19) 0%(N=0/5) 50%(N=2/4) 46%(5/10) DCR at 12 weeks (CR+PR+SD) 58%(N=11/19) 0%(N=0/5) 75%(N=3/4) 80%(8/10) Median Progresssion-Free survival (months) 5.6 2.3 10.3vs POLEnp: HR=0.2 IC95% 0.1-0.7 Median Overall Survival (months) 9.1 5.0 Not Reachedvs POLEnp:HR=0.1 IC95% 0.02-0.7 Citation Format: Benoît Rousseau, Ivan Bieche, Eric Pasmant, Nadim Hamzaoui, Nicolas Leulliot, Lucas Michon, Aurelien de Reynies, Mike Foote, Julien Masliah-Planchon, Magali Svrcek, Romain Cohen, Victor Simmet, Paule Augereau, David Malka, Antoine Hollebecque, Damien Pouessel, Carlos Gomez-Roca, Rosine Guimbaud, Amandine Bruyas, Marielle Guillet, Muriel Duluc, Sophie Cousin, Christelle de la Fourchardiere, Frederic Rolland, Sandrine Hiret, Esma Saada-Bouzid, Olivier Bouche, Thierry Andre, Diane Pannier, Farid El Hajbi, Stephane Oudard, Christophe Tournigand, Jean-Charles Soria, Drew Gerber, Dennis Stephens, Michelle Lamandola-Essel, Steven B Maron, Bill Diplas, Guillem Argiles, Asha Krishnan, Neil Segal, Andrea Cercek, Nathalie Hoog-Labouret, Frederic Legrand, Clotide Simon, Assia Lamrani-Ghaouti, Luis A. Diaz, Pierre Saintigny, Sylvie Chevret, Aurelien Marabelle. PD-1 blockade in solid tumors with defects in polymerase epsilon [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr CT021.

RésuméObjet de réticences diverses, la prescription médicamenteuse chez la femme enceinte répond pourtant à une absolue nécessité dans un certain nombre de cas. Une évaluation correcte du médicament s'impose donc, axée sur l'efficacité et la sécurité ou essentiellement sur la sécurité, selon l'expérience disponible en dehors de la grossesse. La méthodologie d'évaluation ne répond pas nécessairement à des caractéristiques particulières. Des recommandations de développement sont formulées suivant les situations les plus fréquentes ainsi que des propositions concrètes, pour permettre une meilleure sensibilisation des différents partenaires de santé impliqués (institutions, industriels et prescripteurs). En particulier, des incitations d'ordre réglementaire et économique, superposables à celles adoptées en Europe et aux Etats-Unis pour les maladies orphelines, devraient être mises en place pour favoriser l'évaluation obstétricale du médicament.

Background: BRAF mutations occur in 2 to 3% of patients (pts) with non-small cell lung cancer (NSCLC). In these pts vemurafenib, a selective oral BRAF inhibitor is associated with a response rate (RR) of 42%, rising to 64% for combination treatment with dabrafenib and trametinib. Despite initial responses, most pts ultimately develop resistance to therapy. Mechanisms of resistance to BRAF inhibitors in NSCLC have only been reported in 2 pts (acquired KRAS G12D and primary resistance due to BRAF G469L) Objective: To assess the molecular mechanisms of resistance and to monitor disease response to treatment using liquid biopsies in NSCLC pts treated with BRAF inhibitors. Strategy: We performed a longitudinal genomic analysis of circulating-tumor DNA (ctDNA) in BRAF-mutated NSCLC pts treated in the AcSé vemurafenib program (NCT02304809) (n=44), or with the combination of dabrafenib and trametinib (n=6). We have collected 24 samples at baseline, 45 during follow-up and 9 at progressive disease (PD). ctDNA genotyping of 36 genes was performed using the Inivata InVisionFirst™ assay. Functional analyses of potentially resistant mutations and in vitro strategies to revert the resistant phenotype are ongoing. Results: Our preliminary analyses showed that BRAF mutations were detected at diagnosis in 16/24 pts, including 12 BRAF V600E mutations and 4 non-V600E mutations (i.e. G466V, G596R, G469A and K601E). 4/12 (34%) of BRAF V600E-mutated pts presented coexistent mutations, in FGFR2, CTNNB1, IDH1 or PI3KCA, whereas concomitant mutations in KRAS, NRAS or MYC were found in 3/4 (75%) of non-V600E cases. Analyses of response to treatment vs mutational profile will be presented. For the remaining 8/24 pts, TP53 mutations were found in 5 pts in absence of BRAF mutations, and no mutations were detected in 3 pts. Mechanisms of resistance were evaluated in 9 pts. One patient who progressed after 11 months on vemurafenib had MAP2K1 C121S and NFE2L2 p.31-32:GV/X mutations. In this patient, longitudinal ctDNA profiling revealed agreement between the %AF of BRAF and TP53 mutations and response to treatment, and detectable levels of the BRAF V600E and the MAP2K1 C121S mutations up to 6 months before the clinical confirmation of PD. Acquired PI3KCA H1047R and E545K mutations were seen in two pts, respectively, who progressed after 15 and 7 months of vemurafenib. Finally, a fourth patient who relapsed after 3 months on vemurafenib, presented a KRAS G12C mutation. All 4 cases also presented detectable levels of the BRAF V600E mutation at PD. In 3/8 pts, we detected the BRAF V600E mutation at PD but no other mutations; drivers of resistance may be present in genes outside this panel. ctDNA sequencing data on additional 7 pts at PD will be presented. Conclusion: Our results suggest that ctDNA genotyping might be an informative tool for monitoring disease response and resistance in NSCLC pts treated with BRAF-targeted therapies. Citation Format: Sandra Ortiz-Cuaran, Julien Mazières, Aurélie Swalduz, Washington René Chumbi Flores, Yohan Loriot, Virginie Westeel, Anne Pradines, Claire Tissot, Christelle Clement Duchene, Christine Raynaud, Xavier Quantin, Radj Gervais, Etienne Brain, Isabelle Monnet, Etienne Giroux Leprieur, Séverine Neymarc, Virginie Avrillon, Solène Marteau, Séverine Martinez, Gilles Clapisson, Nathalie Girerd-Chambaz, Celine Mahier, Nathalie Hoog-Labouret, Frank de Kievit, Karen Howarth, Emma Green, Clive Morris, Maurice Pérol, Jean-Yves Blay, Pierre Saintingy. Integrative analysis of resistance to BRAF-targeted therapies in lung adenocarcinomas [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1841.