Overcoming osimertinib resistance with AKT inhibition in EGFRm-driven Non-Small-Cell-Lung-Cancer with PIK3CA/PTEN alterations

PURPOSE

Osimertinib is an epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI) indicated for the treatment of EGFR mutated (EGFRm)-driven lung adenocarcinomas. Osimertinib significantly improves progression-free survival in first-line treated patients with EGFRm advanced NSCLC. Despite the durable disease control, the majority of patients receiving osimertinib eventually develop disease progression.

EXPERIMENTAL DESIGN

ctDNA profiling analysis on-progression plasma samples from patients treated with osimertinib in both first (Phase 3, FLAURA trial) and second-line trials (Phase 3, AURA3 trial) revealed a high prevalence of PIK3CA/AKT/PTEN alterations. In vitro and in vivo evidence using CRISPR engineered NSCLC cell lines and PXD models support a functional role for PIK3CA and PTEN mutations in the development of osimertinib resistance.

RESULTS

These alterations are functionally relevant as EGFRm NSCLC cells with engineered PIK3CA/AKT/PTEN alterations develop resistance to osimertinib and can be re-sensitized by treatment with the combination of osimertinib and the AKT inhibitor capivasertib. Moreover, xenograft and PDX in vivo models with PIK3CA/AKT/PTEN alterations display limited sensitivity to osimertinib relative to models without alteration, and in these double mutant models capivasertib and osimertinib combination elicits an improved anti-tumor effect versus osimertinib alone.

CONCLUSIONS

Together, this approach offers a potential treatment strategy for patients with EGFRm-driven NSCLC that have a sub-optimal response, or develop resistance, to osimertinib through PIK3CA/AKT/PTEN alterations.

Resistance to BRAF inhibition explored through single circulating tumour cell molecular profiling in BRAF-mutant non-small-cell lung cancer

BACKGROUND

Resistance mechanisms to combination therapy with dabrafenib plus trametinib remain poorly understood in patients with BRAFV600E-mutant advanced non-small-cell lung cancer (NSCLC). We examined resistance to BRAF inhibition by single CTC sequencing in BRAFV600E-mutant NSCLC.

METHODS

CTCs and cfDNA were examined in seven BRAFV600E-mutant NSCLC patients at failure to treatment. Matched tumour tissue was available for four patients. Single CTCs were isolated by fluorescence-activated cell sorting following enrichment and immunofluorescence (Hoechst 33342/CD45/pan-cytokeratins) and sequenced for mutation and copy number-alteration (CNA) analyses.

RESULTS

BRAFV600E was found in 4/4 tumour biopsies and 5/7 cfDNA samples. CTC mutations were mostly found in MAPK-independent pathways and only 1/26 CTCs were BRAFV600E mutated. CTC profiles encompassed the majority of matched tumour biopsy CNAs but 72.5% to 84.5% of CTC CNAs were exclusive to CTCs. Extensive diversity, involving MAPK, MAPK-related, cell cycle, DNA repair and immune response pathways, was observed in CTCs and missed by analyses on tumour biopsies and cfDNA. Driver alterations in clinically relevant genes were recurrent in CTCs.

CONCLUSIONS

Resistance was not driven by BRAFV600E-mutant CTCs. Extensive tumour genomic heterogeneity was found in CTCs compared to tumour biopsies and cfDNA at failure to BRAF inhibition, in BRAFV600E-mutant NSCLC, including relevant alterations that may represent potential treatment opportunities.

Genomic landscape of liquid biopsy mutations in TP53 and DNA damage genes in cancer patients

Next-generation sequencing (NGS) assays based on plasma cell-free DNA (cfDNA) are increasingly used for clinical trials inclusion. Their optimized limit of detection applied to a large number of genes leads to the identification of mutations not confirmed in tissue. It becomes essential to describe the characteristics and consequences of these liquid biopsy-only mutations. In the STING protocol (Gustave Roussy, NCT04932525), 542 patients with advanced solid cancer had cfDNA-based and tissue-based NGS analysis (performed by FoundationOne® Liquid CDx and FoundationOne CDx™, respectively). Mutations identified in the liquid biopsy but not in the paired tissue were considered as liquid biopsy-only mutations irrespective of their variant allelic frequency (VAF). Out of 542 patients, 281 (51.8%) harbored at least one liquid biopsy-only mutation. These patients were significantly older, and more heavily pretreated. Liquid biopsy-only mutations occurring in TP53, and in DDR genes (ATM, CHEK2, ATR, BRCA2, and BRCA1) accounted for 90.8% of all the mutations. The median VAF of these mutations was generally low (0.37% and 0.40% for TP53 and DDR genes respectively). The variant type repartition depended on the gene. Liquid biopsy-only mutations affected hotspot in TP53 codon 273, 125, 195, 176, 237 or 280 and ATM codon 2891 and 3008. In a subset of 37 patients, 75.0%, 53.5% and 83.3% of the liquid biopsy-only mutations occurring respectively in ATM, TP53, and CHEK2 were confirmed in the matching whole blood sample. Although liquid biopsy-only mutations makes the interpretation of liquid biopsy results more complex, they have distinct characteristics making them more easily identifiable.

Alkylating Agent-Induced High Tumor Mutational Burden in Medullary Thyroid Cancer and Response to Immune Checkpoint Inhibitors: Two Case Reports

Background: Patients with metastatic medullary thyroid cancer (MTC) who progressed under tyrosine kinase inhibitors can benefit from an alkylating agent such as dacarbazine or temozolomide. Patient Findings: We describe two patients with metastatic MTC who developed a hypermutant phenotype after alkylating agent treatment. This phenotype was characterized by a high tumor mutational burden (TMB) and a mutational signature indicative of alkylating agent mutagenesis (single-base substitution 11). Both patients received immune checkpoint inhibitors, with partial morphological responses, clinical benefit, and progression-free survival of 6 and 9 months, respectively. Summary and Conclusions: Based on the described observations, we suggest that a hypermutant phenotype may be induced after alkylating agent treatment for MTC and the sequential use of immunotherapy should be further explored as a treatment option for MTC patients with increased TMB.

Genomic Profiling of Metastatic Castration-Resistant Prostate Cancer Samples Resistant to Androgen Receptor Pathway Inhibitors

PURPOSE

The androgen receptor axis inhibitors (ARPI; e.g., enzalutamide, abiraterone acetate) are administered in daily practice for men with metastatic castration-resistant prostate cancer (mCRPC). However, not all patients respond, and mechanisms of both primary and acquired resistance remain largely unknown.

EXPERIMENTAL DESIGN

In the prospective trial MATCH-R (NCT02517892), 59 patients with mCRPC underwent whole-exome sequencing (WES) and/or RNA sequencing (RNA-seq) of samples collected before starting ARPI. Also, 18 patients with mCRPC underwent biopsy at time of resistance. The objectives were to identify genomic alterations associated with resistance to ARPIs as well as to describe clonal evolution. Associations of genomic and transcriptomic alterations with primary resistance were determined using Wilcoxon and Fisher exact tests.

RESULTS

WES analysis indicated that no single-gene genomic alterations were strongly associated with primary resistance. RNA-seq analysis showed that androgen receptor (AR) gene alterations and expression levels were similar between responders and nonresponders. RNA-based pathway analysis found that patients with primary resistance had a higher Hedgehog pathway score, a lower AR pathway score and a lower NOTCH pathway score than patients with a response. Subclonal evolution and acquisition of new alterations in AR-related genes or neuroendocrine differentiation are associated with acquired resistance. ARPIs do not induce significant changes in the tumor transcriptome of most patients; however, programs associated with cell proliferation are enriched in resistant samples.

CONCLUSIONS

Low AR activity, activation of stemness programs, and Hedgehog pathway were associated with primary ARPIs' resistance, whereas most acquired resistance was associated with subclonal evolution, AR-related events, and neuroendocrine differentiation. See related commentary by Slovin, p. 4323.

Development of Novel Models of Aggressive Variants of Castration-resistant Prostate Cancer

BACKGROUND

Genomic studies have identified new subsets of aggressive prostate cancer (PCa) with poor prognosis (eg, neuroendocrine prostate cancer [NEPC], PCa with DNA damage response [DDR] alterations, or PCa resistant to androgen receptor pathway inhibitors [ARPIs]). Development of novel therapies relies on the availability of relevant preclinical models.

OBJECTIVE

To develop new preclinical models (patient-derived xenograft [PDX], PDX-derived organoid [PDXO], and patient-derived organoid [PDO]) representative of the most aggressive variants of PCa and to develop a new drug evaluation strategy.

DESIGN, SETTING, AND PARTICIPANTS

NEPC (n = 5), DDR (n = 7), and microsatellite instability (MSI)-high (n = 1) PDXs were established from 51 patients with metastatic PCa; PDXOs (n = 16) and PDOs (n = 6) were developed to perform drug screening. Histopathology and treatment response were characterized. Molecular profiling was performed by whole-exome sequencing (WES; n = 13), RNA sequencing (RNA-seq; n = 13), and single-cell RNA-seq (n = 14). WES and RNA-seq data from patient tumors were compared with the models.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Relationships with outcome were analyzed using the multivariable chi-square test and the tumor growth inhibition test.

RESULTS AND LIMITATIONS

Our PDXs captured both common and rare molecular phenotypes and their molecular drivers, including alterations of BRCA2, CDK12, MSI-high status, and NEPC. RNA-seq profiling demonstrated broad representation of PCa subtypes. Single-cell RNA-seq indicates that PDXs reproduce cellular and molecular intratumor heterogeneity. WES of matched patient tumors showed preservation of most genetic driver alterations. PDXOs and PDOs preserve drug sensitivity of the matched tissue and can be used to determine drug sensitivity.

CONCLUSIONS

Our models reproduce the phenotypic and genomic features of both common and aggressive PCa variants and capture their molecular heterogeneity. Successfully developed aggressive-variant PCa preclinical models provide an important tool for predicting tumor response to anticancer therapy and studying resistance mechanisms.

PATIENT SUMMARY

In this report, we looked at the outcomes of preclinical models from patients with metastatic prostate cancer enrolled in the MATCH-R trial (NCT02517892).

Precision medicine in the era of multi-omics: can the data tsunami guide rational treatment decision?

Precision medicine for cancer is rapidly moving to an approach that integrates multiple dimensions of the biology in order to model mechanisms of cancer progression in each patient. The discovery of multiple drivers per tumor challenges medical decision that faces several treatment options. Drug sensitivity depends on the actionability of the target, its clonal or subclonal origin and coexisting genomic alterations. Sequencing has revealed a large diversity of drivers emerging at treatment failure, which are potential targets for clinical trials or drug repurposing. To effectively prioritize therapies, it is essential to rank genomic alterations based on their proven actionability. Moving beyond primary drivers, the future of precision medicine necessitates acknowledging the intricate spatial and temporal heterogeneity inherent in cancer. The advent of abundant complex biological data will make artificial intelligence algorithms indispensable for thorough analysis. Here, we will discuss the advancements brought by the use of high-throughput genomics, the advantages and limitations of precision medicine studies and future perspectives in this field.

Resistance to Selective FGFR Inhibitors in FGFR-Driven Urothelial Cancer

Several fibroblast growth factor receptor (FGFR) inhibitors are approved or in clinical development for the treatment of FGFR-driven urothelial cancer, and molecular mechanisms of resistance leading to patient relapses have not been fully explored. We identified 21 patients with FGFR-driven urothelial cancer treated with selective FGFR inhibitors and analyzed postprogression tissue and/or circulating tumor DNA (ctDNA). We detected single mutations in the FGFR tyrosine kinase domain in seven (33%) patients (FGFR3 N540K, V553L/M, V555L/M, E587Q; FGFR2 L551F) and multiple mutations in one (5%) case (FGFR3 N540K, V555L, and L608V). Using Ba/F3 cells, we defined their spectrum of resistance/sensitivity to multiple selective FGFR inhibitors. Eleven (52%) patients harbored alterations in the PI3K-mTOR pathway (n = 4 TSC1/2, n = 4 PIK3CA, n = 1 TSC1 and PIK3CA, n = 1 NF2, n = 1 PTEN). In patient-derived models, erdafitinib was synergistic with pictilisib in the presence of PIK3CA E545K, whereas erdafitinib-gefitinib combination was able to overcome bypass resistance mediated by EGFR activation.

SIGNIFICANCE

In the largest study on the topic thus far, we detected a high frequency of FGFR kinase domain mutations responsible for resistance to FGFR inhibitors in urothelial cancer. Off-target resistance mechanisms involved primarily the PI3K-mTOR pathway. Our findings provide preclinical evidence sustaining combinatorial treatment strategies to overcome bypass resistance. See related commentary by Tripathi et al., p. 1964. This article is featured in Selected Articles from This Issue, p. 1949.

Patterns of Treatment Failure After Selective Rearranged During Transfection (RET) Inhibitors in Patients With Metastatic Medullary Thyroid Carcinoma

PURPOSE

Medullary thyroid cancer (MTC) harbors frequent mutations in RET oncogene. Selective RET inhibitors (RETi) have emerged as effective treatments. However, resistance almost invariably occurs.

METHODS

MTC patients who were initiated on RETi between 2018 and 2022 were included. Baseline characteristics, RET mutational status, RETi response, available tumor tissue and molecular profiles sampled pre- and post-RETi were analyzed.

RESULTS

Among 46 MTC patients on RETi during the study period, 26 patients had discontinued at data cut-off because of progression (n = 16), death (n = 4), and toxicity (n = 6). The most frequent RET mutations at baseline were p.M918T (n = 29), and p.C634X (n = 6). Pre- and post-RETi molecular profiles were available in 14 patients. There was no primary resistance on pre-RETi samples. Post-RETi profiles revealed a bypass mechanism of resistance in 75% of the cases including RAS genes mutations (50%), FGFR2 and ALK fusions and and MYC p.P44L. RET solvent from and hinge region mutations was the only resistance mechanisms in 25% of the cases. Tumor samples from initial thyroidectomy, pre- and post-RETi, from six patients, showed an increase of the mean Ki 67-index of 7%, 17% and 40% respectively (P = 0.037) and a more aggressive poorly differentiated histology in three patients.

DISCUSSION

Bypass resistance may be the most frequent mechanism of progression under RETi. A more aggressive histology may arise following RETi and warrants further investigation.

Abstract 4678: Characterization of a PDX panel covering molecular diversity of non-small cell lung cancer to accelerate the development of precision therapy

Lung cancer remains the first cause of cancer-related deaths worldwide, of which Non-Small Cell Lung Cancer (NSCLC) represents more than 80% of patients with advanced disease at the time of diagnosis. NSCLC is a highly heterogenous disease, and the identification of its main actionable oncogenic drivers (i.e. EGFR, ALK, PI3K/AKT/mTOR, RET, MET, BRAF and NTRK/ROS1) and the development of specific inhibitors against these targets has transformed therapeutic care. In addition, immune-checkpoint therapy has emerged as an indispensable treatment modality, especially for patients lacking actionable oncogenic drivers, although biomarkers for predicting response to immune-checkpoint inhibition have remained elusive. Despite these new therapeutic options, NSCLC remains a lethal disease in the majority of patients due to tumor plasticity and selection leading to frequent resistance development and disease progression. Efforts are therefore needed to identify drugs and drug combinations that can prevent or overcome these resistance pathways. Patient-Derived Xenografts (PDX) models developed in immune-compromised mice recapitulate the disease more faithfully than any other in vivo model in terms of histopathologic and genomic features. They have proven their relevance in the study of pathways leading to the development and progression of cancer, to the mechanisms linked to tumor resistance and to the identification of novel effective therapies, facilitating the translation of preclinical results in the clinical setting. We describe a platform of over 35 NSCLC PDX models covering most of the molecular diversity of the disease, that have been fully characterized at the molecular level and for their response to a panel of cytotoxic chemotherapies and targeted therapies. These NSCLC PDX models have been established in immune-deficient mice from tumor biopsies collected in treatment-naïve patients or in patients having acquired resistance following an initial objective response to a variety of targeted inhibitors (EGFRi, ALKi, ROSi, BRAFi,⋯) in the MATCH-R clinical trial. In addition, 4 PDX models were established from circulating tumor cells (CTC) isolated from the blood of advanced NSCLC patients. Finally, some of these NSCLC PDX models were established in highly immunodeficient mice humanized with human PBMCs or CD34+ cells allowing testing of efficacy of bispecific T-Cell engager antibody or immune-checkpoint inhibitors. This panel of NSCLC PDX models provides a powerful preclinical platform to improve our knowledge on the mechanisms underlying resistance to treatment and to rapidly evaluate response to new treatments and translate this knowledge to the clinic.

Citation Format: Delphine Nicolle, Laura Brulle-Soumare, Katell Mevel, Ludovic Bigot, Tala Tayoun, Benjamin Besse, Françoise Farace, Luc Friboulet, Didier Decaudin, Erwan Corcuff, Anaïs Joachim, Bernard Malissen, Ana Zarubica, Hervé Luche, Jean-Gabriel Judde, Olivier Deas. Characterization of a PDX panel covering molecular diversity of non-small cell lung cancer to accelerate the development of precision therapy. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4678.

Abstract 3418: Alterations in PIK3CA/PTEN as resistance mechanisms in lung cancer patients progressing on first-line next generation EGFR/ALK tyrosine kinase inhibitors

Introduction: Advent of targeted therapies has deeply changed treatment of advanced oncogene-addicted non-small cell lung cancer (NSCLC), but development of resistance remains a main issue. Given the efficacy of next generation tyrosine kinase inhibitors (TKIs) against on-target mutations, their first-line administration could increase the relevance of off-target resistance mechanisms. Activating PIK3CA mutations and PTEN loss have been described as putative off-target resistance mechanisms across generations of EGFR TKIs. The role of these alterations in the development of resistance to ALK TKIs has been less described.

MATCH-R trial (NCT02517892) is an ongoing prospective study whose objective is to understand mechanisms of acquired resistance to cancer therapies and develop strategies to overcome it.

Materials and methods: We collected clinical and molecular data of patients (pts) with NSCLC enrolled in the molecular target group (MTG) of MATCH-R trial. We identified pts with EGFR mutations or ALK rearrangements who developed PIK3CA/PTEN alterations in tissue biopsy and/or circulating tumor DNA upon progression to first-line osimertinib/alectinib. We established patient-derived cell lines (PDCL) from the identified MATCH-R pts and we engineered commercial cell lines (CCL) harboring EGFR mutation (PC9) or ALK fusion (H3122) to constitutively express PIK3CA mutations and/or to have a permanent loss of PTEN. Cell viability assays and Western blot studies with different EGFR/ALK/PI3K/mTOR inhibitors were performed.

Results: Of the 186 pts with advanced NSCLC included in the MTG of MATCH-R, 110 (59.1%) harbored EGFR mutations (EGFR+) and 27 (14.5%) ALK rearrangements (ALK+). Among them, 19 received first-line osimertinib and seven first-line alectinib. Five and two pts developed PIK3CA/PTEN alterations in the EGFR+ and ALK+ groups, respectively. In the EGFR+ group, PIK3CA E545K (n=2), R108H, N345K and R357Q mutations were detected. PTEN mutations (F437fs*5 and Y27C) were concomitant with E545K and R357Q mutations, respectively. In both ALK+ pts, a PIK3CA E545K mutation was identified, together with PTEN exon 5 splicing in one case. We confirmed on CCL that PIK3CA E545K mutation, alone or in combination with PTEN loss, confers resistance to second-/third-generation EGFR/ALK TKIs. PTEN loss alone had a moderate

impact on TKIs sensitivity. Overcoming strategies combining EGFR/ALK TKIs with PIK3CA/mTOR inhibitors are being evaluated and will be disclosed at the meeting.

Conclusions: Activating PI3KCA mutations and molecular events leading to PTEN loss are frequent events at resistance to first-line EGFR/ALK TKIs, and can be detected concomitantly. Functional assays confirmed that these alterations act as resistance mechanisms. These observations are of interest as PI3KCA/mTOR inhibitors may have a role in overcoming resistance.

Citation Format: Giorgia Guaitoli, Francesco Facchinetti, Juan David Flórez-Arango, Floriane Braye, Hayato Mizuta, Santiago Ponce-Aix, Damien Vasseur, Ken André Olaussen, Stefan Michiels, Mihaela Aldea, Jordi Remon, Fabrice Barlesi, Benjamin Besse, David Planchard, Luc Friboulet. Alterations in PIK3CA/PTEN as resistance mechanisms in lung cancer patients progressing on first-line next generation EGFR/ALK tyrosine kinase inhibitors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3418.

Abstract 1034: Clinical utility of liquid biopsy for molecular characterization and resistance detection in patients with advanced NSCLC and ALK, ROS1 or RET fusions

Introduction Liquid biopsy (LB) is increasingly used in non-small cell lung cancer (NSCLC) for molecular diagnosis or resistance detection. Due to its non-invasive nature, it is often preferred over tissue biopsies, especially when sequential biopsies are warranted. Here, we report the clinical utility of liquid biopsy in patients with advanced NSCLC and ALK, ROS1 or RET fusions and its relevance to detect resistance after targeted therapy.

Methods Between December 2020 and June 2022, 597 patients with advanced lung cancer had at least one liquid biopsy assessed by Foundation One CDx Liquid (panel of 324 genes) in a single institution. Plasma collection was performed in treatment-naïve patients and/or at time of progression. Clinical and molecular data were collected from patients with known fusions (ALK, ROS1, RET). LB were defined as “positive” if the fusion or resistance mutations were identified and “negative” in the absence of circulating-tumor DNA. The clinical utility of LB was evaluated as the proportion of positive results. The clinical relevance for resistance detection was defined as the proportion of LB that identified a putative resistance mechanism after targeted therapy.

Results A total of 68 patients (29 ALK+, 22 RET+ and 17 ROS1+) with 83 LB were included. Patients were females in 50% of cases, had no smoking history in 58% of cases and had adenocarcinoma in 91% of cases. LB was positive in 55/83 (66%) cases overall, in 14/15 (93%) treatment-naïve patients and in 39/66 (59%) pre-treated patients. Factors significantly associated with a negative LB were limited disease progression (brain- or thoracic-only, p<0.001) and ongoing treatment at time of LB collection (p<0.05). Out of 47 LB performed at progression after targeted therapies, 7 (15%) found on-target resistance, 10 (21%) by-pass resistance, 10 (21%) no explainable resistance and 20 (43%) were negative. By-pass alterations included KRAS p.G12C/A mutations (N=2, ALK+), PIK3CA p.E545K/Q (N=3, ALK+), PTEN splice-site mutation (N=1, RET+), MYC amplifications (N=3, ALK+/RET+) and MET amplification (N=1, ROS1+).

Conclusion LB was able to detect resistance mechanisms in one third of NSCLC patients with ALK, RET or ROS1 fusions. However, LB frequently failed to detect circulating-tumor DNA especially in patients with limited disease progression or with ongoing treatment at time of sample collection.

Citation Format: Mihaela Aldea, Arianna Marinello, Marco Tagliamento, Filippo Dall'Olio, Damien Vasseur, Arnaud Bayle, Anas Gazzah, Miruna Grecea, Claudio Nicotra, Ludovic Lacroix, Santiago Ponce, Luc Friboulet, Fabrice Barlesi, Fabrice Andre, David Planchard, Etienne Rouleau, Antoine Italiano, Benjamin Besse. Clinical utility of liquid biopsy for molecular characterization and resistance detection in patients with advanced NSCLC and ALK, ROS1 or RET fusions [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1034.

Abstract 4526: Molecular landscape of clonal hematopoiesis in patients with lung cancer: First results of the CHIC study

Introduction: CHIC (Clonal Hematopoiesis In Lung Cancer) is a retro-prospective study that aims to describe the characteristics of clonal hematopoiesis (CH) in patients with non-small cell lung cancer (NSCLC). We present preliminary results from the retrospective cohort.

Experimental procedures: A retrospective analysis conducted in patients with metastatic or recurrent NSCLC included in the MATCH-R study (NCT02517892) at Gustave Roussy (Villejuif, France). CH was evaluated by a 74-gene targeted NGS panel (HaloPlex - Agilent) performed on DNA extracted by isolated-by-blood leukocytes. The variant allele frequency (VAF) threshold of detection was set at 1%.

Results: 108 consecutive patients with advanced NSCLC included from October 2015 to July 2019 were evaluated, irrespective of the tumor molecular profile. 46% of the patients were female, 67% were former or current smokers. 82% of the patients had adenocarcinoma and 44%, 23%, 33% had bone, liver and/or brain metastases, respectively. Patients had received a median of 2 lines of systemic therapy and 81% were on active anticancer treatment at the time of CH assessment. At least one CH mutation was found in 38 out of 108 patients (35% prevalence), with an increasing with age trend. Patients carrying CH were older as compared to those without CH and had in 29% vs. 11% of cases tumor histology other than adenocarcinoma (p=0.009). No difference in overall survival was observed according to CH detection (log rank p=0.318). We found 64 mutations in 19 different genes: 63% of the patients carried a single mutation, while co-occurrence of two, three, four or five mutations, within the same gene or in more than one, was found in seven (18%), four (11%), one (3%) and two patients (5%), respectively. Epigenetic modifiers (DNMT3A, TET2, ASXL1) were the most frequently mutated genes: 38 mutations with a median VAF of 6.5% detected in 32 patients. DNA repair genes (PPM1D, TP53, CHEK2, ATM) were the second most frequently mutated: 11 mutations at a median VAF of 4% were detected in 9 patients. 7 mutations in genes encoding for the cohesin complex (SMC3, SMC1A, RAD21, STAG2) were found in 6 patients, with a median VAF of 5%. A non-simultaneous cfDNA sequencing by FoundationOne Liquid CDx assay (324-gene panel) was performed in 9 patients for tumor profiling. In 2 out of 3 tested cases the presence of CH was confirmed in plasma liquid biopsy. 4 patients with no detectable CH by the targeted blood sequencing subsequently were found having CH mutations in plasma NGS, on average 45 months apart. To note, as many as 5 out of the 19 detected mutated genes (PPM1D, SMC3, SMC1A, PRPF8, ZRSR2) are not part of the FDA-approved NGS panel used for cfDNA profiling in solid tumors.

Conclusion: We found a consistent prevalence of CH in patients with NSCLC by using a sequencing approach targeted for hematologic disorders. Prognostic implications of CH are under investigation and will be evaluated in the full cohort.

Citation Format: Marco Tagliamento, Christophe Marzac, Mihaela Aldea, Damien Vasseur, Arnaud Bayle, Anas Gazzah, Maud Ngocamus, Claudio Nicotra, Julieta Rodriguez, Antonin Levy, Capucine Baldini, Santiago Ponce, Felix Blanc-Durand, Etienne Rouleau, Antoine Italiano, Ludovic Lacroix, Luc Friboulet, David Planchard, Fabrice Barlesi, Yohann Loriot, Jean-Baptiste Micol, Benjamin Besse. Molecular landscape of clonal hematopoiesis in patients with lung cancer: First results of the CHIC study. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4526.

Abstract 425: Characterization of TKI-induced drug-tolerant persister cells from a patient-derived cell line

Introduction: Targeted therapies provide clinical benefits in patients harboring oncogene-driven cancers, but relapses invariably occur. Studies on resistance mechanisms are essential to guide the development of next-generation inhibitors. An increasing number of studies focus on an earlier stage of disease evolution. Resistance may develop from the selection of preexisting resistant cells or by adaptation of drug-tolerant persister (DTP) cells. In this context, our study depicts DTP cells able to survive the initial tyrosine kinase inhibitor (TKI) exposure without harboring genetic changes, in order to identify the vulnerabilities existing in this cell state. Materials and

Methods: This project focuses on a patient-derived cell line from the prospective MATCH-R clinical trial (NCT0251782). The model is a non-small cell lung cancer harboring EML4-ALK fusion and ALK C1156Y/G1269A mutation, sensitive to the 3rd generation ALK TKI lorlatinib. In vitro, fully resistant cells were generated by long-term lorlatinib exposure and the acquired resistance mechanism resulted from an epithelial-mesenchymal transition (EMT). DTP cells were generated under shorter drug exposures that eradicate sensitive carcinoma cells.

Results and Discussion: Carcinoma cell plasticity drives cell transformation towards a phenotypic state, rendering them more tolerant to drugs. To better characterize this phenotype, we first focused on EMT and observed that DTP cells co-harbored epithelial and mesenchymal markers. We noticed that DTP cells exhibited an intracellular reactive oxygen species (ROS) rate making them dependent on protective oxidation-reduction mechanisms against oxidative stress-related damage. We revealed the overexpression of p21 and p27, known to bind to cyclin-CDK complexes and induce cell-cycle arrest. This dormant phenotype of DTP cells was underlined by a global repressive chromatin state evidenced by enrichment in H3K27me3, H3K36me3 and H3K9me3 marks; the latter mark also being a component of senescence-associated heterochromatin foci. In agreement, a high level of SA-β-gal and senescence-associated secretory phenotype components (CXCL10, PAI-1), evidenced that our DTP model displayed a senescence-like phenotype. We quantified an increase in γH2AX DNA damage foci in DTP cells compared to sensitive cells, in line with the concept that TKI treatment may have a role in DNA repair modulation that ultimately promotes new mutations. Together, our data depicted DTP features that might be relevant to identify drug candidates overcoming resistance (HDAC inhibitors, senolytic drugs and DNA repair inhibitors).

Conclusion: We demonstrated potential targetable features of DTP cells. A combination of targeted therapies with DTP drug candidates could represent a therapeutic opportunity to improve the depth of response and delay the emergence of resistance in patients.

Citation Format: Floriane Brayé, Francesco Facchinetti, Helena Gerber, Juliette Juigné, Giorgia Guaitoli, Jean-Paul Thiery, Santiago Ponce, Benjamin Besse, Ken A. Olaussen, Luc Friboulet. Characterization of TKI-induced drug-tolerant persister cells from a patient-derived cell line [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 425.

Abstract 4664: MatchR a preclinical platform of models resistant to innovative therapies

Introduction: In the last 20 years, the advances in molecular oncology and cancer genetics allowed the identification of an increasing number of actionable oncogenic drivers and the development and clinical use of specific inhibitors. Despite these successes, it is now well established that tumour cells adapt and develop acquired resistance. It is crucial to understand these mechanisms of acquired resistance to develop overcoming therapeutic strategies. At Gustave Roussy, a prospective clinical trial MATCH-R (NCT02517892) is conducted to study the acquired resistance mechanisms and to find new therapeutic approaches for patients.. In parallel, of genetics analysis from patients biopsies, we develop Patient Derived Xenograft (PDX) to deepen our understanding of the resistance mechanism and to investigate new therapeutic approaches.

Material and Method: Fresh tumor biopsy specimens were obtained prospectively from patients through a prospective single-institution clinical trial (MATCH-R, NCT02517892). Patient derived xenografts (PDX) in NOD Scid Gamma (NSG) mice as well as patient derived organoids from PDX (PDXO) and Patient derived cell lines were developed and characterized. Extensive molecular profiling including whole exome sequencing (WES), RNA sequencing (RNAseq) and immunohistochemistry were performed on human samples; PDX; Patient derived cells lines and PDXO.

Results and Discussion: As of November 2022, 145 PDX models have been successfully obtained from 371 biopsies (global take rate of 39%). Our focus is the development of models from different cohorts: Androgen receptor inhibitors in castration-resistant prostate cancer, (18 PDX), ALK inhibitors in lung cancers (16 PDX including 3 post brigatinib, 7 post Lorlatinib and 6 Alectinib), EGFR inhibitors in lung cancers (33 PDX includind 24 post osimertinib), FGFR inhibitors in urothelial carcinoma and cholangiocarcinoma (29 PDX including 14 post erdafitinib, 4 post pemigatinib, 4 post futibatinib) and KRAS inhibitors in lung cancer and pancreatic cancers (20 PDX). The PDX models recapitulate the genetics, the phenotype and the pharmacology of the original biopsies. Novel mechanisms of resistance to tyrosine kinase inhibitors (TKI) in solid tumors were identified. Adaptive treatment with novel TKI or combinatorial strategies were evaluated to restore the sensitivity in PDX (readout: mean tumor growth). These results confirmed that PDX models are crucial to study the resistance mechanism and to develop new therapeutic strategies.

Conclusion: Overall, the MATCH-R study provides a unique preclinical platform to identify resistance mechanisms to innovative therapies and to develop next generation therapeutic strategies.

Citation Format: Ludovic Bigot, Catline Nobre, Francesco Facchinetti, Loic Poiraudeau, Floriane Braye, Jonathan Sabio, Naoual Mensourri, Olivier Deas, Claudio Nicotra, Maud Ngo-Camus, Lambros Tselikas, Jean Yves Scoazec, Karim Fizazi, Siantiago Ponce, Benjamin Besse, Luc Friboulet, Yohann Loriot. MatchR a preclinical platform of models resistant to innovative therapies. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4664.

Integrative pan-cancer genomic and transcriptomic analyses of refractory metastatic cancer

Metastatic relapse after treatment is the leading cause of cancer mortality, and known resistance mechanisms are missing for most treatments administered to patients. To bridge this gap, we analyze a pan-cancer cohort (META-PRISM) of 1,031 refractory metastatic tumors profiled via whole-exome and transcriptome sequencing. META-PRISM tumors, particularly prostate, bladder, and pancreatic types, displayed the most transformed genomes compared to primary untreated tumors. Standard-of-care resistance biomarkers were identified only in lung and colon cancers - 9.6% of META-PRISM tumors, indicating that too few resistance mechanisms have received clinical validation. In contrast, we verified the enrichment of multiple investigational and hypothetical resistance mechanisms in treated compared to non-treated patients, thereby confirming their putative role in treatment resistance. Additionally, we demonstrated that molecular markers improve six-month survival prediction, particularly in patients with advanced breast cancer. Our analysis establishes the utility of META-PRISM cohort for investigating resistance mechanisms and performing predictive analyses in cancer.

Abstract PR009: Integrative pan-cancer genomic and transcriptomic analyses of refractory metastatic cancer

Metastatic relapse after treatment is the primary cause of cancer morbidity and mortality. While genetic mechanisms of primary tumors and, to a lesser extent, metastatic cancers have been studied in large cohorts, refractory metastatic tumors are not yet sufficiently characterized. Markers of aggressiveness and resistance that molecular profiling can extract from these tumors have yet to be identified and incorporated into clinical care. In this study, we present a pan-cancer cohort of 1,031 metastatic tumors (which we refer to as META-PRISM) that are resistant to at least one systemic therapy or with no approved treatment options. We retrieved the complete clinical history of patients and performed whole-exome (n=571) and transcriptome sequencing (n=947) for this cohort. The prevalence of detected cancer biomarkers was assessed and compared to an external cohort of primary tumors. In the META-PRISM cohort, we observed an increase in (i) whole-genome duplication frequency, (ii) tumor mutational burden, (iii) germline cancer-predisposing variants, and (iv) somatic alterations in cancer genes, including KRAS, EGFR, CCND1, MYC, and TP53, as compared to the tumor type-matched primary tumors. The most extensive increase in genomic variation at metastatic stage was observed in prostate cancer. We also identified enrichment of standard-of-care resistance biomarkers in most cancer types. However, only 7.6% of tumors harbored at least one such biomarker, indicating that the current understanding of resistance mechanisms remains insufficient. Our cohort demonstrated a significantly improved 6-month survival prediction from models incorporating molecular markers over models with only clinical markers for breast cancer patients and to a lesser extent for other studied tumor types. Overall, our data establish a unique resource for investigating treatment resistance mechanisms and performing predictive analyses in cancer.

Citation Format: Yoann Pradat, Julien Viot, Konstantin Gunbin, Andrei Iurchenko, Marc Deloger, Luigi Cerbone, Guillaume Grisay, Loic Verlingue, Veronique Scott, Stefan Michiels, Antoine Hollebecque, Gerome Jules-Clement, Antoine Laine, Luc Friboulet, Laura Mezquita, Yohann Loriot, Benjamin Besse, Fabrice Andre, Paul-Henry Cournede, Daniel Gautheret, Sergey Nikolaev. Integrative pan-cancer genomic and transcriptomic analyses of refractory metastatic cancer [abstract]. In: Proceedings of the AACR Special Conference: Cancer Metastasis; 2022 Nov 14-17; Portland, OR. Philadelphia (PA): AACR; Cancer Res 2022;83(2 Suppl_2):Abstract nr PR009.

Implementing the European Society for Medical Oncology Scale for Clinical Actionability of Molecular Targets in a Comprehensive Profiling Program: Impact on Precision Medicine Oncology

PURPOSE

To facilitate implementation of precision medicine in clinical management of cancer, the European Society of Medical Oncology proposed in 2018 a new scale to harmonize and standardize the reporting and interpretation of clinically relevant genomics data (ESMO Scale of Actionability of molecular Targets [ESCAT]). This study aims to characterize the clinical impact of matching targetable genomic alterations (GAs) in patients with advanced cancer according to ESCAT.

MATERIAL AND METHODS

Analysis of next-generation sequencing results from 552 patients is included in two prospective precision medicine studies at Gustave Roussy. End points included objective response rates, progression-free survival, and overall survival according to ESCAT.

RESULTS

Molecular data from 516 patients were available and discussed within a Molecular Tumor Board. The most common tumor types were GI (n = 164; 30%), lung (n = 137; 25%), and urologic tumors (n = 68; 13%). Overall, 379 GAs were considered as actionable targets according to ESCAT in 348 (67%) patients. In 31 (6%) patients, two concomitant actionable targets were identified. On the basis of ESCAT, GAs were considered to be classified as tier I in 120 patients (29%), II in 25 patients (5%), III in 80 patients (16%), and IV in 153 patients (30%). A total of 136 patients (27%) received a matched therapy. ESCAT was significantly associated with objective response rates and clinical benefit rates. The median progression-free survival was 6.5 months (95% CI, 4.2 to 8.9), 3 months (95% CI, 1 to not available), 3 months (95% CI, 2.2 to 3.8), and 4 months (95% CI, 2.8 to 6.3) for ESCAT I, II, III, and IV, respectively ( P = .0125).

CONCLUSION

Implementation of ESCAT classification for clinical decision making by Molecular Tumor Board is feasible and useful to better tailor therapies in patients with cancer.

The Clinical Landscape of Cell-Free DNA Alterations in 1,671 Patients with Advanced Biliary Tract Cancer

BACKGROUND

Targeted therapies have transformed clinical management of advanced biliary tract cancer (BTC). Cell-free DNA (cfDNA) analysis is an attractive approach for cancer genomic profiling that overcomes many limitations of traditional tissue-based analysis. We examined cfDNA as a tool to inform clinical management of patients with advanced BTC and generate novel insights into BTC tumor biology.

PATIENTS AND METHODS

We analyzed next-generation sequencing data of 2,068 cfDNA samples from 1,671 patients with advanced BTC generated with Guardant360. We performed clinical annotation on a multi-institutional subset (n=225) to assess intra-patient cfDNA-tumor concordance and the association of cfDNA variant allele fraction (VAF) with clinical outcomes.

RESULTS

Genetic alterations were detected in cfDNA in 84% of patients, with targetable alterations detected in 44% of patients. FGFR2 fusions, IDH1 mutations, and BRAF V600E were clonal in majority of cases, affirming these targetable alterations as early driver events in BTC. Concordance between cfDNA and tissue for mutation detection was high for IDH1 mutations (87%) and BRAF V600E (100%), and low for FGFR2 fusions (18%). cfDNA analysis uncovered novel putative mechanisms of resistance to targeted therapies, including mutation of the cysteine residue (FGFR2 C492F) to which covalent FGFR inhibitors bind. High pre-treatment cfDNA VAF associated with poor prognosis and shorter response to chemotherapy and targeted therapy. Finally, we report the frequency of promising targets in advanced BTC currently under investigation in other advanced solid tumors, including KRAS G12C (1.0%), KRAS G12D (5.1%), PIK3CA mutations (6.8%), and ERBB2 amplifications (4.9%).

CONCLUSIONS

These findings from the largest and most comprehensive study to date of cfDNA from patients with advanced BTC highlight the utility of cfDNA analysis in current management of this disease. Characterization of oncogenic drivers and mechanisms of therapeutic resistance in this study will inform drug development efforts to reduce mortality for patients with BTC.

Abstract 3337: Preclinical activity of NVL-655 in ALK-driven cancer models beyond non-small cell lung cancer

The ALK receptor tyrosine kinase can be aberrantly activated by gene fusions, point mutations, or amplification to promote cancer. ALK fusions are detected in approximately 5% of advanced non-small cell lung cancers (NSCLC), 50% of inflammatory myofibroblastic tumors, 50% of adult and 90% of childhood anaplastic large cell lymphomas, and rare cases of cholangiocarcinomas. Over 90 fusion partners of ALK have been identified, each exerting a different influence on the biochemical properties of the fusion protein and its preclinical sensitivity to ALK inhibitors. Besides fusions, ALK point mutations and amplification account for up to 14% and 2% of sporadic neuroblastomas, respectively, with most activating mutations occurring at residues F1174, F1245, or R1275. Some activating mutations, such as those occurring at F1174 and I1171, also confer resistance to FDA-approved ALK inhibitors. Because ALK plays an oncogenic role in diverse cancer types, it is an important therapeutic target for other indications beyond NSCLC.

NVL-655 is a novel, brain-penetrant ALK-selective inhibitor that exhibits preclinical activity against ALK alterations, including resistance mutations, while also sparing inhibition of TRKB. TRKB inhibition in the central nervous system has been implicated in adverse events observed with FDA-approved ALK inhibitor lorlatinib. We previously reported the preclinical activity of NVL-655 in several NSCLC models bearing ALK-fusions, including human cell lines, a human cell-line derived xenograft, and a patient-derived xenograft. Here we report a broader characterization of NVL-655 in ALK-driven cancer models beyond NSCLC, alongside other ALK inhibitors that are either FDA-approved or in development.

In biochemical assays, NVL-655 showed potent inhibition (IC50 < 10 nM) of ALK with mutations at residues 1151, 1174, or 1275, all of which have been identified in neuroblastoma. In cell-based assays, NVL-655 was observed to inhibit proliferation of a human anaplastic large cell lymphoma cell line harboring NPM1-ALK fusion and human neuroblastoma cell lines harboring ALK activating mutations or amplification. In conclusion, the preclinical profile of NVL-655 supports its potential to address a medical need for patients with ALK-driven disease in both NSCLC and other cancers such as anaplastic large cell lymphoma and neuroblastoma.

Citation Format: Anupong Tangpeerachaikul, Ludovic Bigot, Luc Friboulet, Henry E. Pelish. Preclinical activity of NVL-655 in ALK-driven cancer models beyond non-small cell lung cancer [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 3337.

Abstract 3113: Molecular and pharmacological profiling of a novel prostate cancer-derived xenograft panel to identify resistance mechanisms and new therapeutic options

Prostate Cancer (PCa) is the most frequently diagnosed cancer in men and remains one of the leading causes of cancer death worldwide. It is a highly heterogenous and complex disease, presenting serious challenges to preclinical drug development and biomedical research. Prostate normal development, growth and function, as well as most of its pathological drifts, are associated to androgen receptor (AR) pathway regulation. Most patients subjected to androgen deprivation therapy (ADT) respond well to the treatment, however they usually progress into intractable castration-resistant PCa (CRPC) within 2 to 3 years. Therefore, understanding the mechanisms of castration resistance underlying PCa progression is key to develop future therapies. Patient-Derived Xenografts (PDX) are mouse models that recapitulate the disease more faithfully than any other in vivo model in terms of histopathologic, genomic and metastatic features, facilitating the translation of preclinical results in the clinical setting. PCa PDXs are challenging to develop, and only few are available to the scientific community. This lack of relevant preclinical models is a major limitation in PCa research. In particular, the development of PCa PDX models from castration-resistant tumors to explore new treatments against CRPC is a requirement. To fill this gap, XenTech and Gustave Roussy Institute are collaborating to develop a panel of PCa PDX models. In the framework of the MATCH-R clinical trial (NCT02517892), in which patients with disease progression under treatment are enrolled and switched to new targeted therapy based on the genetic alterations identified in biopsies, 8 PCa PDXs have been developed from metastatic lesions biopsy. In addition, we developed a PCa PDX model from circulating tumor cells (CTCs) obtained by leukapheresis at diagnosis. These 9 models, plus 4 PCa PDXs previously developed at XenTech, increases our PCa PDX panel to 13 models. All models were characterized at molecular level by whole exome and RNA sequencing and pharmacologically for response to standards of care, physical castration and response to the androgen receptor inhibitor enzalutamide. This PDX collection is a valuable preclinical tool to identify pivotal mechanisms underlying acquired resistance to current therapies and develop novel treatment strategies against PCa and CRPC.

Citation Format: Laura Brulle-Soumare, Ludovic Bigot, Katell Mevel, Enora Le Ven, Luc Friboulet, Benjamin Besse, Françoise Farace, Jean Gabriel Judde, Stefano Cairo, Yohann Loriot, Olivier Déas. Molecular and pharmacological profiling of a novel prostate cancer-derived xenograft panel to identify resistance mechanisms and new therapeutic options [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 3113.

Abstract 1251: Low plasma Arginine level is associated with resistance to immune checkpoint blockers in patients with advanced cancer

Background: The discovery of immune checkpoint blockers (ICB) has revolutionized the systemic approach of the treatment of cancer. However, most patients receiving ICB do not derive benefit. Therefore, there is a crucial need to identify reliable predictive biomarkers of response to anti-PD-1/PD-L1 agents, both to develop precision medicine in cancer immunotherapy and to better understand mechanisms of sensitivity and resistance. One pathway that plays an important role in the regulation of immune cell reactivity is L-Arginine (Arg) metabolism, which is essential to T-cell activation. We therefore aimed at evaluating the association of baseline plasmatic level of Arg - serving as a surrogate of Arginase (Arg1) activity - and clinical benefit to ICB.

Methods: Correlation with Arg levels and efficacy of ICB in the pre-clinical setting was assessed by using a syngeneic mouse model of colorectal cancer (MC38) known to be responsive to ICB. Correlation of Arg levels and clinical activity of ICB was assessed by analyzing the plasma samples obtained before treatment onset in two independent cohorts of patient with advanced cancer and included in two institutional molecular profiling programs (discovery cohort: BIP, NCT02534649, n=77; validation cohort: PREMIS, n=295, NCT03984318). In addition, using matched PBMCs-plasma samples, we analyzed the correlation between Arg level and features of PBMCs that were captured through multiplexed-flow cytometry analysis.

Results: As expected, treatment of MC38-tumor bearing mice with anti-PD(L)1 antibodies demonstrated a strong anti-tumor effect with tumor rejection observed for app. 40% of mice (11 out of 28). The tumor rejection rate was significantly higher in mice with high baseline Arg level than in mice with low Arg level: 85.7% versus 23.8%, p=0.004. In both discovery and validation cohorts, low Arg level at baseline (42 <µmol/L) was significantly associated with worse clinical benefit rate, progression-free survival (PFS) and overall survival (OS). Multivariate analysis showed that low baseline Arg level isd an independent prognostic factor for both PFS and OS. Finally, PBMCs immunophenotyping showed that low Arg level was significantly associated with increased PDL1 expression in several immune cell subsets from the myeloid lineage.

Conclusions: Altogether, our results demonstrate that baseline Arg levels are highly predictive of ICB efficacy. Increase in PDL1 expression in myeloid cells upon Arg deprivation could partly underly its suppressive activity. Plasmatic Arg quantification can therefore represent an attractive biomarker to tailor novel therapeutic regimens targeting the Arginase pathway in combination with ICB.

Citation Format: Jean-Philippe Guegan, Florent Peyraud, Aurelien Marabelle, Nathalie Chaput, Dominique Bodet, Laure Fontan, Anthony Gaultier, Imane NAFIA, Francois-Xavier Danlos, David Planchard, Caroline Robert, Caroline Even, Mohamed Khettab, Lambros Tselikas, Luc Friboulet, Jean-Charles Soria, Fabrice Andre, Fabrice Barlesi, Alban Bessede, Antoine Italiano. Low plasma Arginine level is associated with resistance to immune checkpoint blockers in patients with advanced cancer [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 1251.

Plasma proteomics identifies leukemia inhibitory factor (LIF) as a novel predictive biomarker of immune-checkpoint blockade resistance

BACKGROUND

Immune checkpoint blockers (ICBs) are now widely used in oncology. Most patients, however, do not derive benefit from these agents. Therefore, there is a crucial need to identify novel and reliable biomarkers of resistance to such treatments in order to prescribe potentially toxic and costly treatments only to patients with expected therapeutic benefits. In the wake of genomics, the study of proteins is now emerging as the new frontier for understanding real-time human biology.

PATIENTS AND METHODS

We analyzed the proteome of plasma samples, collected before treatment onset, from two independent prospective cohorts of cancer patients treated with ICB (discovery cohort n = 95, validation cohort n = 292). We then investigated the correlation between protein plasma levels, clinical benefit rate, progression-free survival and overall survival by Cox proportional hazards models.

RESULTS

By using an unbiased proteomics approach, we show that, in both discovery and validation cohorts, elevated baseline serum level of leukemia inhibitory factor (LIF) is associated with a poor clinical outcome in cancer patients treated with ICB, independently of other prognostic factors. We also demonstrated that the circulating level of LIF is inversely correlated with the presence of tertiary lymphoid structures in the tumor microenvironment.

CONCLUSION

This novel clinical dataset brings strong evidence for the role of LIF as a potential suppressor of antitumor immunity and suggests that targeting LIF or its pathway may represent a promising approach to improve efficacy of cancer immunotherapy in combination with ICB.

Abstract 358: A prospective study of prostate cancer metastases identifies an androgen receptor activity-low, stemness program associated with resistance to androgen receptor axis inhibitors and unveils mechanisms of clonal evolution

Background: The androgen receptor axis inhibitors (ARi) (e.g, enzalutamide, abiraterone acetate) are administered in daily practice for men with metastatic castration-resistant prostate cancer (mCRPC). However, not all patients respond, and mechanisms of both primary and acquired resistance remain largely unknown.

Methods: In a prospective trial MATCH-R (NCT02517892), 55 mCRPC patients underwent whole exome sequencing (WES) (n=45) and RNA-sequencing (RNA-seq) (n=52) of metastatic biopsies before starting ARi. Also, 16 mCRPC patients underwent biopsy at time of resistance (WES=14, RNA-seq = 14). The objectives were to identify genomic alterations associated with resistance to ARi as well as to describe clonal evolution. Primary resistance was determined at 4 months of treatment using composite criteria for progression that included serum prostate specific antigen measurements, bone scan, CT imaging and symptom assessments. Acquired resistance was defined by occurrence of progressive disease after initial response or stable disease. Associations of genomic and transcriptomic alterations with primary resistance were determined using Wilcoxon and Fisher's exact tests.

Results: At 4 months, 22/55 patients in the cohort had disease progression (primary resistance). No genomic alterations from WES analysis were significantly associated with primary resistance. Analysis of sequential biopsies suggests that mCRPC follows mainly a parallel evolution model and involve DNA-repair related mutational processes. At time of acquired resistance to ARi, most tumors acquired new drivers affecting AR pathway (e.g, AR, NCOR1/2) or lineage switching (e.g, RB1, PTEN, TP53). Using computational methods, we measured AR transcriptional function and performed gene set enrichment analysis to identify pathways whose activity state correlated with resistance. AR gene alterations and AR expression were similar between responding and non-responding patients. Transcriptional analysis demonstrated that multiple specific gene sets — including those linked to low AR transcriptional activity, stemness program, RB loss and homologous repair deficiency — were activated in both primary and acquired resistance.

Conclusion: Resistance to AR axis inhibitors results from multiple transcriptional programs already activated in pre-treatment samples. Clonal evolution analysis along with RNA-seq data indicate the role of genomic instability and lineage switching in driving acquired resistance

Citation Format: Naoual Menssouri, Loic Poiraudeau, Carole Helissey, Ludovic Bigot, Jonathan Sabio, Tony Ibrahim, Claudio Nicotra, Maud Ngocamus, Lambros Tselikas, Thierry De Baere, Etienne Rouleau, Ludovic Lacroix, Anne Chaucherau, Luc Friboulet, Ronan Flippot, Giulia Baciarello, Laurence Albiges, Emeline Colomba, Pernelle Lavaud, Stefan Michiels, Aline Maillard, Antoine Italiano, Fabrice Barlesi, Jean-Charles Soria, Jean-Yves Scoazec, christophe Massard, Benjamin Besse, Fabrice André, Karim Fizazi, Daniel Gautheret, Yohann Loriot. A prospective study of prostate cancer metastases identifies an androgen receptor activity-low, stemness program associated with resistance to androgen receptor axis inhibitors and unveils mechanisms of clonal evolution [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 358.

Abstract 448: High prevalence of pathogenic germline variants in patients with oncogene-driven non-small cell lung cancer

BACKGROUND: Preliminary data has highlighted inherited predisposition to lung cancer related to certain genes. The frequency of pathogenic germline variants (PGV) PGV in patients (pts) with lung cancer according to the presence of an oncogenic driver is unknown. We studied the PGV of genes predisposing to cancer in pts with non-small cell lung cancer (NSCLC), and the somatic molecular profile of lung tumors.

METHODS: Retrospective study of whole exome sequencing (WES) from tissue biopsies performed in pts with advanced NSCLC enrolled, after signature of the inform consent, in the MOSCATO/MATCH-R trials between 2012 and 2018. Variants were considered as PGVs in the cancer predisposing genes (PMID: 29625052) if they satisfied the following criteria: (i) they had a “PASS” flag in HaplotypeCaller, (ii) were annotated as “Pathogenic” or “Likely Pathogenic” in ClinVar (PMID: 29165669) or InterVar (PMID: 28132688), or (iii) were truncating variants. Somatic driver mutations and Loss of Heterozygocity (LOH) of PGV harboring genes were further evaluated. The overlap to loss of heterozygocity regions was reported only when the variant allele frequency of the PGV was significantly higher than in the normal tissue. Cancer history, clinical and molecular data were retrospectively collected. The somatic mutations (m) in EGFR/BRAF/MET/HER2/KRAS and fusions in ALK/ROS1/RET were also considered for analysis.

RESULTS: Among 134 pts, 48% were women, median age was 61 (range 24-83), 45% were nonsmokers, 74% had adenocarcinoma. The most common somatic oncogenic driver alterations were: EGFRm in 44 pts (33%), KRASm in 19 pts (14%), BRAFm in 12 pts (9%) and ALK in 12 pts (9%).PGV were found in 22 out of 152 (15%) cancer-predisposing genes; 4 pts had additional somatic mutations (2) or LOHs (2) in the same genes. 77% of PGVs were in genes which are part of DNA repair pathways including 3.6% nucleotide excision repair (ERCC1/2/3, XPA), 6.5% homologous recombination/Fanconi Anemia: (FANC/A/C/M/D2, BRCA1, RECQL), 2.1% base excision repair (MUTYH, NTHL1), while the others were represented by genes related to cell signaling and metabolism (NF1, MET, ELANE, PRDM9, TRIM37).In the 22 PGV-carriers, 68% had a somatic oncogene-driven alteration (15/22) : EGFRm (n=7; 5 ex19del, 2 ex21(L858R)), KRASm (n=3; 2 G12D, 1 G12V), METm (n=2), HER2m (n=1), ROS1 (n=1) and RET (n=1). PGV were observed in 16% of EGFRm (7/44), 67% of METm (2/3), 15% in KRASm (3/19), 33% of HER2m (1/3), 25% of ROS1 (1/4), 50% of RET (1/2); but no PGV was identified in pts with BRAFVm (12) or ALK (12).

CONCLUSION: In our cohort, 15% of pts with NSCLC were PGV-carriers; 68% of PGV-carriers had oncogene-driven tumors, particularly with somatic EGFR mutations. PGV and oncogene-driven lung carcinogenesis need further evaluation.

Citation Format: Laura Mezquita, Andrei Iurchenko, Jose Carlos Benitez, Maria Baz, Sergey Nikolaev, David Planchard, Felix Blanc-Durand, Mihaela Aldea, Patricia Martín-Romano, Yohann Loriot, Claudio Nicotra, Maud Ngocamus, Jean-Yves Scoazec, Stefan Michiels, Sophie Postel-Vinay, Julien Viot, Luc Friboulet, Antoine Italiano, Fabrice Andre, Christophe Massard, Jean-Charles Soria, Etienne Rouleau, Daniel Gautheret, Benjamin Besse. High prevalence of pathogenic germline variants in patients with oncogene-driven non-small cell lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 448.

Abstract 3016: Identification of the mechanisms of resistance to targeted therapies in advanced solid cancers

Despite progress in understanding aberrations that contribute to the development and progression of cancer, resistance to classical chemotherapeutic agents or novel targeted drugs continues to be a major problem in cancer therapy. Hence, the identification of the mechanisms underlying drug resistance acquisition is the key to explore new and efficient therapeutic pathways for patients. The MATCH-R clinical trial enrolls patients with oncogene-driven cancer who have had previous clinical response to targeted therapy and subsequently experienced disease progression under treatment. In the framework of this project, Gustave Roussy and XenTech are joining forces to develop a panel of patient-derived xenografts (PDXs) derived from biopsies collected from these patients at the stage of acquired resistance. These PDX models are being fully characterized at both molecular and pharmacological levels and used to improve knowledge on the mechanisms underlying resistance to treatment and to evaluate response to new treatments. In this perspective, the development of 75 PDX-AR (Acquired Resistance) models is planned over 3 years. To favor successful xenograft establishment, the first passages are performed without drug treatment, then all the models are maintained under the same therapeutic pressure the parental tumor was submitted to at the time of biopsy. When applying therapeutic pressure, we observed different types of response: resistance from the first passage under treatment, stabilization under treatment at the first passages and rapidly acquired resistance over passages, or sensitivity to treatment whereas the patient tumor showed progression under the same treatment. These different behaviors can be observed in PDX models developed from multiple metastases of a same patient and may reflect different mechanisms of resistance. Most interestingly, PDX models obtained from different metastatic lesions of a same patient can recapitulate the different behavior observed in this patient. This behavior is translated by either tumor progression in one PDX model and/or stabilization under treatment in another. These paired models greatly facilitate the identification of relevant mechanisms of drug resistance.We have now completed the development of a panel of 25 PDX models of various indications and exposed to a variety of last generation targeted therapies. We will discuss relevant examples of results that can be generated from this panel, with particular focus on the molecular features of models with acquired or intrinsic resistance to treatment and of paired models with different drug sensitivity. These data highlight the unique potential of the MATCH-R preclinical platform to identify resistance mechanisms and develop next generation therapeutic strategies.

Citation Format: Olivier Deas, Emilie Dassé, Laura Brulle-Soumare, Katell Mevel, Ludovic Bigot, Yohann Loriot, Fabrice André, Jean-Charles Soria, Benjamin Besse, Enora Le Ven, Stefano Cairo, Luc Friboulet, Jean-Gabriel Judde. Identification of the mechanisms of resistance to targeted therapies in advanced solid cancers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 3016.

Abstract 598: Resistance mechanisms to BRAF inhibition identified by single circulating tumor cell and cell-free tumor DNA molecular profiling in BRAF-mutant non-small cell lung cancer

Background: Combination therapy with dabrafenib + trametinib demonstrated robust activity in patients (pts) with BRAFV600E-mutant advanced non-small cell lung cancer (NSCLC), but its resistance mechanisms are poorly known. Liquid biopsy components such as circulating tumor cells (CTCs) and cell-free (cf) tumor DNA can provide a comprehensive genomic picture of tumor content. Molecular profiling of single CTCs from pts with BRAF-V600Emutant NSCLC was performed to carry out a pilot study to identify resistance mutations at failure to dabrafenib + trametinib and to compare the mutations detected on CTCs to the mutations found on cfDNA and tumor biopsies.

Patients and Methods: Eight pts with advanced BRAFV600E-mutant NSCLC at failure to dabrafenib + trametinib were prospectively enrolled between Jul 2018 and Mar 2019 at Gustave Roussy (IDRCB2008-A00585-50). Bloods samples were collected. Matched tissue-cfDNA and CTCs were available in 3 pts and matched tissue-CTCs for 4 pts. Single CTC isolation strategy included RosetteSep enrichment, immunofluorescent staining (Hoechst/CD45/cytokeratins) and fluorescence activated cell-sorting. The process to identify CTC mutations included Ampli1 whole-genome amplification, quality controls, multiplex targeted PCR with the Ampli1 CHPCustomBeta cancer panel developed by (Menarini Silicon Biosystems) and next-generation sequencing (NGS). The cfDNA was analyzed using InVisionFirst-Lung. Tissue samples were analyzed using targeted NGS in the MATCH-R trial (Recondo G; NPJ Precis Oncol 2020).

Results: Single CTCs were isolated from 7 pts. As baseline characteristics, the median age was 66 years, 5 (71%) were smoker; all the pts with adenocarcinoma histology. Most of the pts received dabrafenib + trametinib as 2nd line (86%). The median of CTCs isolated by patient was 20 (8-28). A wide spectrum of mutations in CTCs was observed at treatment failure that were involved in the main cancer pathways, including MAPK (n=1; NRAS), tyrosine kinase receptors (n=5; EGFR, ALK, FLT3, HER2,…), signal transduction (n=4; IDH1, EZH2,⋯), and DNA repair (n=2; AKT1, ATM,⋯). In the same CTC, several mutations were observed in 5/7 patients, commonly involving more than one cancer pathways. A higher degree of mutational diversity was observed in CTCs compared to tumor tissue biopsies and cfDNA. In the 3 patients with an available tumor/liquid biopsy, only 1 shared mutations between CTCs and matched tumor and cfDNA.

Conclusion: Single CTC profiling reveals a wide spectrum of therapeutic resistance mutations not detected by other analyses in pts with BRAFV600E-mutant NSCLC at failure to dabrafenib + trametinib. Integration of single CTC sequencing to tumor and cfDNA analysis, provides important perspectives to assess heterogeneous resistance mechanisms and to guide precision medicine in BRAFV600E- NSCLC.

Citation Format: Laura Mezquita, Marianne Oulhen, Agathe Aberlenc, Marc Deloger, Aurélie Honoré, Marianna Garonzi, Genny Buson, Claudio Forcato, Yann Lecluse, Mihaela Aldea, Maud NgoCamus, Claudio Nicotra, Karen Howarth, Ludovic Lacroix, Luc Friboulet, Benjamin Besse, Nicolò Manaresi, David Planchard, Françoise Farace. Resistance mechanisms to BRAF inhibition identified by single circulating tumor cell and cell-free tumor DNA molecular profiling in BRAF-mutant non-small cell lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 598.

Immune checkpoint inhibitors in oncogene-addicted non-small cell lung cancer: a systematic review and meta-analysis

Background

Treatment of oncogene-addicted non-small cell lung cancer (NSCLC) has been changed by the advent of tyrosine kinase inhibitors (TKIs). Albeit great benefits are achieved with target therapies, resistance invariably occurs and recourse to alternative treatments is unavoidable. Immune checkpoint inhibitors (ICIs) role and the best setting of immunotherapy administration in oncogene-driven NSCLC are matter of debate.

Methods

We performed a systematic literature review through PubMed, in order to gather all the available information regarding ICI activity and efficacy in oncogene-addicted NSCLC, from both prospective trials and retrospective series. A meta-analysis of objective response rate in different molecular subgroups was provided. Combinatorial strategies including ICIs and related toxicities were also recorded.

Results

Eighty-seven studies were included in the qualitative analysis. EGFR mutation may be a biomarker of poor response to single-agent ICIs (7% of EGFR-mutant NSCLC patients achieved disease response in prospective trials), while encouraging results have been shown with combination strategies. KRAS-mutated disease (response rate, RR, 22%) has different clinical and pathological characteristics, and the co-existence of additional mutations (e.g., STK11 or TP53) influence tumor microenvironment and response to immunotherapy. Other molecular alterations have been marginally considered prospectively, and data from clinical practice are variegated, given poor effectiveness of ICIs in ALK-rearranged disease (RR 9.5%, pooling the data of retrospective studies) or some encouraging results in BRAF-(RR 25%, retrospective data) or MET-driven one (with estimations conditioned by the presence of both exon 14 skipping mutations and gene amplification in reported series).

Conclusions

In oncogene-addicted NSCLC (with the exception of KRAS-mutated), ICIs are usually administered at the failure of other treatment options, but administering single-agent immunotherapy in later disease phases may limit its efficacy. With the progressive administration of TKIs and ICIs in early-stage disease, molecular characterization will become fundamental in this setting.

Clinicogenomic Analysis of FGFR2-Rearranged Cholangiocarcinoma Identifies Correlates of Response and Mechanisms of Resistance to Pemigatinib

Pemigatinib, a selective FGFR1-3 inhibitor, has demonstrated antitumor activity in FIGHT-202, a phase II study in patients with cholangiocarcinoma harboring FGFR2 fusions/rearrangements, and has gained regulatory approval in the United States. Eligibility for FIGHT-202 was assessed using genomic profiling; here, these data were utilized to characterize the genomic landscape of cholangiocarcinoma and to uncover unique molecular features of patients harboring FGFR2 rearrangements. The results highlight the high percentage of patients with cholangiocarcinoma harboring potentially actionable genomic alterations and the diversity in gene partners that rearrange with FGFR2. Clinicogenomic analysis of pemigatinib-treated patients identified mechanisms of primary and acquired resistance. Genomic subsets of patients with other potentially actionable FGF/FGFR alterations were also identified. Our study provides a framework for molecularly guided clinical trials and underscores the importance of genomic profiling to enable a deeper understanding of the molecular basis for response and nonresponse to targeted therapy. SIGNIFICANCE: We utilized genomic profiling data from FIGHT-202 to gain insights into the genomic landscape of cholangiocarcinoma, to understand the molecular diversity of patients with FGFR2 fusions or rearrangements, and to interrogate the clinicogenomics of patients treated with pemigatinib. Our study highlights the utility of genomic profiling in clinical trials.This article is highlighted in the In This Issue feature, p. 211.

Circulating Tumor DNA Genomics Reveal Potential Mechanisms of Resistance to BRAF-Targeted Therapies in Patients with BRAF-Mutant Metastatic Non-Small Cell Lung Cancer

PURPOSE

The limited knowledge on the molecular profile of patients with BRAF-mutant non-small cell lung cancer (NSCLC) who progress under BRAF-targeted therapies (BRAF-TT) has hampered the development of subsequent therapeutic strategies for these patients. Here, we evaluated the clinical utility of circulating tumor DNA (ctDNA)-targeted sequencing to identify canonical BRAF mutations and genomic alterations potentially related to resistance to BRAF-TT, in a large cohort of patients with BRAF-mutant NSCLC.

EXPERIMENTAL DESIGN

This was a prospective study of 78 patients with advanced BRAF-mutant NSCLC, enrolled in 27 centers across France. Blood samples (n = 208) were collected from BRAF-TT-naïve patients (n = 47), patients nonprogressive under treatment (n = 115), or patients at disease progression (PD) to BRAF-TT (24/46 on BRAF monotherapy and 22/46 on BRAF/MEK combination therapy). ctDNA sequencing was performed using InVisionFirst-Lung. In silico structural modeling was used to predict the potential functional effect of the alterations found in ctDNA.

RESULTS

BRAF^V600E ctDNA was detected in 74% of BRAF-TT-naïve patients, where alterations in genes related with the MAPK and PI3K pathways, signal transducers, and protein kinases were identified in 29% of the samples. ctDNA positivity at the first radiographic evaluation under treatment, as well as BRAF-mutant ctDNA positivity at PD were associated with poor survival. Potential drivers of resistance to either BRAF-TT monotherapy or BRAF/MEK combination were identified in 46% of patients and these included activating mutations in effectors of the MAPK and PI3K pathways, as well as alterations in U2AF1, IDH1, and CTNNB1.

CONCLUSIONS

ctDNA sequencing is clinically relevant for the detection of BRAF-activating mutations and the identification of alterations potentially related to resistance to BRAF-TT in BRAF-mutant NSCLC.

Abstract 1867: Characterization of multiple driver alterations in acquired resistance to osimertinib in EGFR-mutated lung cancer: implementation of single cell approaches

Background Despite a primary benefit, resistance to the 3rd generation EGFR-Tyrosine Kinase Inhibitor (TKI) osimertinib invariably occurs. Several reports have recently highlighted the emergence of new oncogenic alterations as an actionable mechanism of resistance. However, the question of whether those alterations occur within a single tumor cell or in distinct tumor cell populations is still pending. Understanding those mechanisms at a cellular level is essential for a better comprehension of acquired resistance mechanisms and to identify new therapeutic opportunities.

Methods This project studied tissues and patient derived cell lines from the ongoing prospective MATCH-R study (NCT0251782), in which patients with unresectable or metastatic cancer are included upon acquired resistance to targeted therapies or immunotherapy. Serial blood samples and tumor biopsies are collected at progression, for targeted NGS, WES and RNAseq, as well as PDX and patient-derived cell lines development. EGFR-mutated patients presenting a new driver alteration at osimertinib progression were identified. Single cell isolation and whole genome amplification were performed on corresponding frozen biopsies and derived cell lines. Cell lines were then exposed to specific inhibitors targeting the different pathways involved and functional analysis were performed to study the efficiency of combining different targeted therapies.

Results Out of 466 patients included in MATCH-R study since June 2015, 110 patients presented EGFR-mutated adenocarcinoma. Among the 38 patients who experienced progression to 2nd line osimertinib, 5 patients were identified with a new oncogenic driver alteration, including STRN-ALK fusion (n=1), FGFR3-TACC3 fusion (n=1), BRAFV600E mutation (n=2), KIF-RET fusion (n=1). One patient progressing to 1st line osimertinib was identified with FGFR3-TACC3 fusion. All samples presented the persistence of EGFR activating mutation, i.e. EGFR exon 19 deletion (n=4) and exon 21 L858R mutation (n=2). After single cell isolation from tissue biopsies, PCR and targeted NGS allowed to highlight the co-existence of both drivers within single tumor cells for three patients. The remaining samples are still under investigation. Combination strategies with dual TKI are currently ongoing in order to restore sensitivity in cell lines (IC50 and Western Blots).

Perspectives These data allow a better understanding of mechanisms underlying cell adaptation to EGFR-driven tumor inhibition. Combining targeted therapies represents a valuable therapeutic opportunity to overcome drug resistance in EGFR-mutated lung cancer. Updated results will be presented at the Meeting.

Citation Format: Jeanne Chen, Floriane Braye, Francesco Facchinetti, Ludovic Lacroix, Jean-Yves Scoazec, Lambros Tselikas, David Planchard, Laura Mezquita, Anas Gazzah, Charles Naltet, Pernelle Lavaud, Aline Maillard, Stefan Michiels, Christophe Massard, Ken.A. Olaussen, Fabrice André, Gilles Vassal, Jean-Charles Soria, Benjamin Besse, Luc Friboulet. Characterization of multiple driver alterations in acquired resistance to osimertinib in EGFR-mutated lung cancer: implementation of single cell approaches [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1867.

Abstract 1114: Novel preclinical models of aggressive variants of castration-resistant prostate cancer

Background: Recent advances in the biology of prostate cancer have identified aggressive variants of metastatic castration-resistant prostate cancer [mCRPC] (e.g, CRPC with neuroendocrine (NE) features, or microsatellite instability [MSI], or BRCA2 mutations). However, few preclinical models have been successfully established to study these aggressive mCRPC variants owing to their historically low establishment success and to the difficulty in accessing such clinical samples

Methods: Fresh tumor biopsy specimens were obtained prospectively from patients with mCRPC through a prospective single-institution clinical trial (MATCH-R, NCT02517892). Patient-derived xenografts (PDX) in NOD Scid Gamma mice were developed and characterized as well as PDX-derived organoids derived from the same PDX (PDXO). Whole-exome sequencing, RNA sequencing and immunohistochemistry were performed on human samples and their corresponding PDX and PDXO. The primary aim was to successfully derive PDX and PDXO models reproducing the clinical features of mCRPC aggressive variants.

Results: As of November 2019, 83 tumor biopsies were obtained from 61 mCRPC patients, 16 biopsies from 13 patients were successfully engrafted with an overall success rate of 26% (16/61). In addition, 16 PDXO were developed with a success rate of 100%. Overall, we developed 4 PDX and 4 PDXO from 2 patients with germline BRCA2 mutation, 2 PDX and 2 PDXO from 1 patient with MSI-high CPRC, 10 PDX and 6 PDXO from 10 patients with NE mCPRC. Molecular profiling revealed a high concordance between PDX, PDXO and human tumor samples for histological phenotype, driver mutations and transcriptomic phenotypes. The two models harbouring BRCA2 mutation were highly sensitive to both carboplatin and olaparib (in PDX and PDXO) reflecting the clinical scenario observed in the patients. BRCA2-mutated PDX models were treated in vivo to derive olaparib-resistant mCRPC models. Genetic analysis identified secondary mutations restoring the reading-frame of the gene which reversed the sensitivity of the PDX to carboplatin and olaparib. Preclinical models derived from mCRPC with NE features (including the case of small cell carcinoma) globally reproduced the clinical patterns seen in human samples. Results from high-throughput organoid drug screening suggest good concordance with patients clinical response

Conclusion: The study demonstrated the feasibility of establishing preclinical models (PDX and PDXO) derived from aggressive mCRPC variants. Overall, our models reproduce the phenotypic, molecular and pharmacological characteristics of their initial human samples and may represent a unique preclinical platform modeling BRCA2 mutated, MSI and neuroendocrine prostate cancers.

Citation Format: Ludovic Bigot, Jonathan Sabio, Tony Ibrahim, Naoual Menssouri, Loic poiraudeau, Carole Helissey, Jean-Yves Scoazec, Zahira Merabet, Thierry De Baere, Frederic Deschamps, Maud Ngocamus, Claudio Nicotra, Etienne Rouleau, Ludovic Lacroix, Olivier Deas, Luc Friboulet, Gilles Vassal, Eric Solary, Jean-Charles Soria, Karim Fizazi, Fabrice André, Christophe Massard, Benjamin Besse, Yohann Loriot. Novel preclinical models of aggressive variants of castration-resistant prostate cancer [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1114.

Clinical Relevance of an Amplicon-Based Liquid Biopsy for Detecting ALK and ROS1 Fusion and Resistance Mutations in Patients With Non-Small-Cell Lung Cancer

PURPOSE

Liquid biopsy specimen genomic profiling is integrated in non-small-cell lung cancer (NSCLC) guidelines; however, data on the clinical relevance for ALK /ROS1 alterations are scarce. We evaluated the clinical utility of a targeted amplicon-based assay in a large prospective cohort of patients with ALK/ROS1-positive NSCLC and its impact on outcomes.

PATIENTS AND METHODS

Patients with advanced ALK/ROS1-positive NSCLC were prospectively enrolled in the study by researchers at eight French institutions. Plasma samples were analyzed using InVisionFirst-Lung and correlated with clinical outcomes.

RESULTS

Of the 128 patients included in the study, 101 were positive for ALK and 27 for ROS1 alterations. Blood samples (N = 405) were collected from 29 patients naïve for treatment with tyrosine kinase inhibitors (TKI) or from 375 patients under treatment, including 105 samples collected at disease progression (PD). Sensitivity was 67% (n = 18 of 27) for ALK/ROS1 fusion detection. Higher detection was observed for ALK fusions at TKI failure (n = 33 of 74; 46%) versus in patients with therapeutic response (n = 12 of 109; 11%). ALK-resistance mutations were detected in 22% patients (n = 16 of 74) overall; 43% of the total ALK-resistance mutations identified occurred after next-generation TKI therapy. ALK G1202R was the most common mutation detected (n = 7 of 16). Heterogeneity of resistance was observed. ROS1 G2032R resistance was detected in 30% (n = 3 of 10). The absence of circulating tumor DNA mutations at TKI failure was associated with prolonged median overall survival (105.7 months). Complex ALK-resistance mutations correlated with poor overall survival (median, 26.9 months v NR for single mutation; P = .003) and progression-free survival to subsequent therapy (median 1.7 v 6.3 months; P = .003).

CONCLUSION

Next-generation, targeted, amplicon-based sequencing for liquid biopsy specimen profiling provides clinically relevant detection of ALK/ROS1 fusions in TKI-naïve patients and allows for the identification of resistance mutations in patients treated with TKIs. Liquid biopsy specimens from patients treated with TKIs may affect clinical outcomes and capture heterogeneity of TKI resistance, supporting their role in selecting sequential therapy.

High Prevalence of Somatic Oncogenic Driver Alterations in Patients With NSCLC and Li-Fraumeni Syndrome

INTRODUCTION

Actionable somatic molecular alterations are found in 15% to 20% of NSCLC in Europe. NSCLC is a tumor observed in patients with germline TP53 variants causing Li-Fraumeni syndrome (LFS), but its somatic molecular profile is unknown.

METHODS

Retrospective study of clinical and molecular profiles of patients with NSCLC and germline TP53 variants.

RESULTS

Among 22 patients with NSCLC and LFS (n = 23 lung tumors), 64% were women, median age was 51 years, 84% were nonsmokers, 73% had adenocarcinoma histological subtype, and 84% were diagnosed with advanced-stage disease. These patients harbored 16 distinct germline TP53 variants; the most common was p.R158H (5/22; three in the same family). Personal and family histories of cancer were reported in 71% and 90% of patients, respectively. In most cases (87%, 13/15), lung cancer was diagnosed with a late onset. Of the 21 tumors analyzed, somatic oncogenic driver mutations were found in 19 of 21 (90%), EGFR mutations in 18 (exon 19 deletion in 12 cases, L858R in three cases, and G719A, exon 20 insertion, and missing mutation subtype, each with one case), and ROS1 fusion in one case. A PI3KCA mutation was concurrently detected at diagnosis in three EGFR exon 19-deleted tumors (3/12). The median overall survival was 37.3 months in 14 patients treated with EGFR inhibitors; seven developed resistance, five (71%) acquired EGFR-T790M mutation, and one had SCLC transformation.

CONCLUSIONS

Driver oncogenic alterations were observed in 90% of the LFS tumors, mainly EGFR mutations; one ROS1 fusion was also observed. The germline TP53 variants and lung cancer carcinogenesis driven by oncogenic processes need further evaluation.

Oncogenic Fusions May Be Frequently Present at Resistance of EGFR Tyrosine Kinase Inhibitors in Patients With NSCLC: A Brief Report

Introduction

Despite initial benefit, virtually all patients suffering from EGFR-mutant NSCLC experience acquired resistance to tyrosine kinase inhibitors (TKIs), driven by multiple mechanisms. Recent reports have identified oncogenic kinase fusions as off-target resistance mechanisms; however, these alterations have been rarely investigated at EGFR TKIs progression.

Methods

Patients with EGFR-mutated metastatic NSCLC (N = 62) with tissue and plasma biopsies at EGFR TKI progression between January 2015 and June 2019, at a French hospital and optionally before progression, were identified from the prospective MATCH-R study (NCT02517892). Postprogression biopsy samples were analyzed for gene fusions using targeted gene panel sequencing, whole-exome sequencing, RNA sequencing, and comparative genomic hybridization array.

Results

Six gene fusions were detected in tumor progression biopsies under an EGFR TKI from 62 consecutive patients (9.7%) with EGFR-mutated advanced NSCLC. Among 31 patients progressing to first- or second-generation EGFR TKIs, one (3%) had an Eukaryotic translation initiation factor 4 gamma 2–GRB2 associated binding protein 1 (EIF4G2-GAB1) fusion. Among 31 patients progressing to the third-generation osimertinib, five (16%) presented oncogene fusions of fibroblast growth factor receptor 3–transforming acidic coiled-coil containing protein 3 (FGFR3-TACC3) (n = 2), kinesin family member 5B–Ret proto-oncogene (KIF5B-RET) (n = 1), striatin–anaplastic lymphoma kinase (STRN-ALK) (n = 1), and zinc finger DHHC-Type palmitoyltransferase 20–Thr790Met (ZDHHC20-BRAF) (n = 1) transcripts. Out of two patients that received osimertinib at first-line, one acquired an FGFR3-TACC3 fusion at progression. In all patients, fusions co-occurred with the original activating EGFR mutation; however, among four patients with an acquired T790M mutation, three (75%) lost the T790M mutation.

Conclusions

Oncogenic fusions at the time of EGFR TKI resistance were identified at a relatively high frequency, mainly after the third-generation TKI osimertinib. Patients progressing to EGFR TKIs may have a new opportunity for targeted therapy when oncogenic fusions are identified.

Facts and New Hopes on Selective FGFR Inhibitors in Solid Tumors

Precision oncology relies on the identification of molecular alterations, responsible for tumor initiation and growth, which are suitable targets of specific inhibitors. The development of FGFR inhibitors represents an edifying example of the rapid evolution in the field of targeted oncology, with 10 different FGFR tyrosine kinase inhibitors actually under clinical investigation. In parallel, the discovery of FGFR activating molecular alterations (mainly FGFR3 mutations and FGFR2 fusions) across many tumor types, especially urothelial carcinomas and intrahepatic cholangiocarcinomas, widens the selection of patients that might benefit from selective FGFR inhibitors. The ongoing concomitant clinical evaluation of selective FGFR inhibitors in molecularly selected solid tumors brings new hopes for patients with metastatic cancer, for tumors so far excluded from molecularly guided treatments. Matching molecularly selected tumors with selective FGFR inhibitors has indeed led to promising results in phase I and II trials, justifying their registration to be expected in a near future, such as the recent accelerated approval of erdafitinib granted by the FDA for urothelial cancer. Widening our knowledge of the activity, efficacy, and toxicities relative to the selective FGFR tyrosine kinase inhibitors under clinical investigation, according to the exact FGFR molecular alteration, will be crucial to determine the optimal therapeutic strategy for patients suffering from FGFR-driven tumors. Similarly, identifying with appropriate molecular diagnostic, every single tumor harboring targetable FGFR alterations will be of utmost importance to attain the best outcomes for patients with FGFR-driven cancer.

Abstract B043: Identification of secreted PD-L1 variants as a decoy of PD-L1 blockade antibody mediating the therapeutic resistance

Immune checkpoint blockade therapy targeting PD-L1/PD-1 have been widely used and shown remarkable clinical response in various cancers. However, therapeutic resistance after initial response is increasingly observed and the detailed mechanisms of resistance have yet to be fully understood. Recently, several mechanisms including loss-of-function alteration in genes related to antigen presentation and interferon-receptor signaling have been suggested to induce the resistance to PD-1 blockade treatment, yet few studies have focused on anti-PD-L1 (aPD-L1) blockade therapy. In current study, we performed whole exome sequencing and RNA-sequencing analysis in two non-small cell lung cancer (NSCLC) patients who were refractory during aPD-L1 therapy. We have identified the mutations in RNA splicing related gene, TARDBP/TDP-43, which were uncovered as hot spot mutations in Amyotrophic lateral sclerosis (ALS), and found two unique secreted PD-L1 variants, which lacked the transmembrane domain by aberrant RNA splicing. These secreted PD-L1 variants were shown to be stable by pulse chase assay, and worked as “decoys” of aPD-L1 antibody in the HLA-matched coculture system of iPSC-derived CD8 T cells and cancer cells. Moreover, expression of secreted mPD-L1 variant in mouse MC38 cancer cells conferred the resistance to PD-L1 blockade therapy, and soluble PD-L1 were time dependently accumulated in plasma using the MC38 syngeneic mice model. To further investigate the presence of secreted PD-L1 splicing variants in patients, we additionally analyzed 15 specimen who were resistant to anti-PD-L1 treatment by RNA-seq. We revealed that approximately 20% of therapeutic resistant patients harbored secreted PD-L1 variants and several new mutations in JAK1/2, the key mediator of interferon-receptor signaling, were found in a part of patients as well. Furthermore, we also identified the presence of secreted PD-L1 variants in the surgical specimens of squamous NSCLC patients without prior chemotherapy, targeted therapy, and /or immune-checkpoint inhibitor therapy. Consistent to the data, the plasma level of soluble PD-L1 in patients with secreted PD-L1 variants were high than those without the variants. Collectively, our results elucidated a novel resistant mechanism of PD-L1 blockade antibody mediated by secreted PD-L1 variants. The presence of sPD-L1 splicing variants or the level of soluble PD-L1 in plasma or pleural effusion may work as a biomarker to predict a patient’s response to PD-L1 blockade therapy.

Citation Format: Bo Gong, Kazuma Kiyotani, Seiji Sakata, Ken Takahashi, Seiji Nagano, Shun Kumehara, Satoko Baba, Benjamin Besse, Noriko Yanagitani, Luc Friboulet, Makoto Nishio, Kengo Takeuchi, Hiroshi Kawamoto, Naoya Fujita, Ryohei Katayama. Identification of secreted PD-L1 variants as a decoy of PD-L1 blockade antibody mediating the therapeutic resistance [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics; 2019 Oct 26-30; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2019;18(12 Suppl):Abstract nr B043. doi:10.1158/1535-7163.TARG-19-B043

Diverse Resistance Mechanisms to the Third-Generation ALK Inhibitor Lorlatinib in ALK-Rearranged Lung Cancer

PURPOSE

Lorlatinib is a third-generation anaplastic lymphoma kinase (ALK) tyrosine kinase inhibitor with proven efficacy in patients with ALK-rearranged lung cancer previously treated with first- and second-generation ALK inhibitors. Beside compound mutations in the ALK kinase domain, other resistance mechanisms driving lorlatinib resistance remain unknown. We aimed to characterize the mechanisms of resistance to lorlatinib occurring in patients with ALK-rearranged lung cancer and design new therapeutic strategies in this setting.

EXPERIMENTAL DESIGN

Resistance mechanisms were investigated in 5 patients resistant to lorlatinib. Longitudinal tumor biopsies were studied using high-throughput next-generation sequencing. Patient-derived models were developed to characterize the acquired resistance mechanisms, and Ba/F3 cell mutants were generated to study the effect of novel ALK compound mutations. Drug combinatory strategies were evaluated in vitro and in vivo to overcome lorlatinib resistance.

RESULTS

Diverse biological mechanisms leading to lorlatinib resistance were identified. Epithelial-mesenchymal transition (EMT) mediated resistance in two patient-derived cell lines and was susceptible to dual SRC and ALK inhibition. We characterized three ALK kinase domain compound mutations occurring in patients, L1196M/D1203N, F1174L/G1202R, and C1156Y/G1269A, with differential susceptibility to ALK inhibition by lorlatinib. We identified a novel bypass mechanism of resistance caused by NF2 loss-of-function mutations, conferring sensitivity to treatment with mTOR inhibitors.

CONCLUSIONS

This study shows that mechanisms of resistance to lorlatinib are diverse and complex, requiring new therapeutic strategies to tailor treatment upon disease progression.

Profile of entrectinib and its potential in the treatment of ROS1-positive NSCLC: evidence to date

ROS1 inhibition provides impressive survival benefits in ROS1-rearranged non-small cell lung cancer (NSCLC) patients. Crizotinib is the only tyrosine kinase inhibitor (TKI) approved by both FDA and EMA for the treatment of ROS1-positive lung cancer. In addition, several TKI have been tested with preliminary proofs of success in this oncogene-driven disease, either in the post-crizotinib setting or as first-line targeted agents. Here we present the evidence concerning entrectinib, an ALK/ROS1/NTRK inhibitor developed across different tumor types harboring rearrangements in these genes, in the context of ROS1-driven NSCLC. Of interest, in August 2019 entrectinib was granted by FDA accelerated approval for the treatment of ROS1-rearranged NSCLC, as well as of NTRK-driven solid tumors.

Acquired Resistance Mutations to ALK Inhibitors Identified by Single Circulating Tumor Cell Sequencing in ALK-Rearranged Non-Small-Cell Lung Cancer

PURPOSE

Patients with anaplastic lymphoma kinase (ALK)-rearranged non-small-cell lung cancer (NSCLC) inevitably develop resistance to ALK inhibitors. New diagnostic strategies are needed to assess resistance mechanisms and provide patients with the most effective therapy. We asked whether single circulating tumor cell (CTC) sequencing can inform on resistance mutations to ALK inhibitors and underlying tumor heterogeneity in ALK-rearranged NSCLC.

EXPERIMENTAL DESIGN

Resistance mutations were investigated in CTCs isolated at the single-cell level from patients at disease progression on crizotinib (n = 14) or lorlatinib (n = 3). Three strategies including filter laser-capture microdissection, fluorescence activated cell sorting, and the DEPArray were used. One hundred twenty-six CTC pools and 56 single CTCs were isolated and sequenced. Hotspot regions over 48 cancer-related genes and 14 ALK mutations were examined to identify ALK-independent and ALK-dependent resistance mechanisms.

RESULTS

Multiple mutations in various genes in ALK-independent pathways were predominantly identified in CTCs of crizotinib-resistant patients. The RTK-KRAS (EGFR, KRAS, BRAF genes) and TP53 pathways were recurrently mutated. In one lorlatinib-resistant patient, two single CTCs out of 12 harbored ALK compound mutations. CTC-1 harbored the ALK ^{G1202R/F1174C} compound mutation virtually similar to ALK ^{G1202R/F1174L} present in the corresponding tumor biopsy. CTC-10 harbored a second ALK ^{G1202R/T1151M} compound mutation not detected in the tumor biopsy. By copy-number analysis, CTC-1 and the tumor biopsy had similar profiles, whereas CTC-10 harbored multiple copy-number alterations and whole-genome duplication.

CONCLUSIONS

Our results highlight the genetic heterogeneity and clinical utility of CTCs to identify therapeutic resistance mutations in ALK-rearranged patients. Single CTC sequencing may be a unique tool to assess heterogeneous resistance mechanisms and help clinicians for treatment personalization and resistance options to ALK-targeted therapies.

Abstract 2122: Generation of a fully characterized preclinical PDX panel to accelerate the identification of next generation treatments for patients with acquired resistance to targeted therapies

The last 20 years have witnessed the identification of an increasing number of actionable oncogenic drivers and the development and clinical use of specific inhibitors against these targets. Unfortunately, patients treated with targeted therapies consistently develop resistance and progression under treatment. Hence, important scientific, pharmaceutical and medical research efforts are directed towards understanding the mechanisms of acquired resistance to explore new therapeutic pathways.

The MATCH-R clinical trial enrolls patients with oncogene-driven cancer who have had previous clinical response to targeted therapy and subsequently experienced disease progression. In the framework of this project, Gustave Roussy and XenTech are joining forces to develop a panel of patient-derived xenografts (PDXs) derived from biopsies collected from these patients at the stage of acquired resistance. These PDX models will be fully characterized at molecular and pharmacological level and used to improve knowledge on the mechanisms underlying resistance to treatment and to evaluate response to new treatments.

In this perspective, the development of 75 PDX-AR (Acquired Resistance) models is planned over 3 years. All the models are maintained under the same therapeutic pressure the parental tumor was submitted to at the time of biopsy, and will be subjected to extensive phenotypic and genotypic characterization.

To favor successful xenograft establishment, the first two passages are performed without drug treatment, which is applied from the third passage on. When doing so, we observed 3 types of response: some models showed resistance from the first passage under treatment, some showed stabilization under treatment at the first passages and rapidly acquired resistance over passages, and others showed sensitivity to treatment, whereas the patient tumor showed progression under the same treatment. These different behaviors might be due to different mechanisms of resistance, irreversible for the former, reversible for the two latter, as well as to suboptimal correlation of the clinical dose with the one used in mice.

An example of such discrepancies has been found in two models of NSCLC PDX obtained from two metastases from a patient treated by a ROS1 and ALK inhibitor. While LCx-MR135PD2-AR PDX does not respond to the treatment, the LCx-MR135PD1 model is highly sensitive. As both metastases were progressing under treatment in the patient, molecular and pharmacological comparative analysis of these two models will investigate these discrepancy and provide important insights into the mechanisms of resistance to such inhibitors.

Overall, the MatchR PDX project will provide a unique preclinical platform to identify resistance mechanisms to current targeted therapies and to develop next generation therapeutic strategies.

Citation Format: Olivier Déas, Ludovic Bigot, Emilie Dasse, Guillaume Lang, Yohann Loriot, Fabrice Andre, Jean-Charles Soria, Benjamin Besse, Stefano Cairo, Marie Tavernier, Katell Mevel, Enora Le Ven, Jean-Gabriel Judde, Luc Friboulet. Generation of a fully characterized preclinical PDX panel to accelerate the identification of next generation treatments for patients with acquired resistance to targeted therapies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2122.