BaF3 Cells Research Articles

New ABL1 Kinase Domain Mutations in BCR::ABL1-Positive Acute Lymphoblastic Leukemia.

Since the development of the first-generation Tyrosine Kinase Inhibitor (TKI), it has played a crucial role in the treatment of BCR::ABL1-positive acute lymphoblastic leukemia (ALL) and chronic myeloid leukemia (CML). However, ABL1 kinase domain (ABL1 KD) mutations confer resistance to several TKIs. These mutations have been extensively studied in chronic myeloid leukemia (CML) but less so in BCR::ABL1-positive acute lymphoblastic leukemia (ALL). Our study aimed to analyze the the ABL1 KD mutations in 97 consecutive newly-diagnosed adults with BCR::ABL1-positive ALL before therapy, in cytogenetic complete remission and at relapse with next generation sequencing (NGS). The relationship between ABL1 KD mutations and TKI selection was also analyzed. Previously unreported ABL1 KD mutations R239G, F401V/L, R516L and K262T were the most prevalent in pre-therapy and cytogenetic remission samples, whereas T315I/P and P-loop mutations were most prevalent in relapse samples. R239G, F401V/L, R516L and K262T are related to the BCR::ABL1 structure, whereas T315I/P and P-loop mutations directly alter kinase activity. BaF3 cells transfected with ABL1 KD F401V, K262T, R239G, or R516L mutations were resistant to imatinib but strongly inhibited by olverembatinib with IC50 values of 0.73 to 1.52nM. Meanwhile, olverembatinib had advantages in increasing complete molecular response (CMR) and good prognosis. Overall, our findings indicate the prevalence and impact of new ABL1 KD mutations in BCR::ABL1-positive ALL patients, highlighting the necessity for effective therapies targetingthese mutations.

Discovery of Novel 2-Aminopyridine-Based and 2-Aminopyrimidine-Based Derivatives as Potent CDK/HDAC Dual Inhibitors for the Treatment of Refractory Solid Tumors and Hematological Malignancies.

Co-inhibition of histone deacetylase (HDAC) and cyclin-dependent kinase (CDK) synergizes to produce enhanced antitumor effects and potentially overcomes the drug resistance. In this work, we discovered a series of novel CDK9/HDACs dual inhibitors. Among them, compound 8e was identified to show potent CDK9 and HDAC1 inhibitory activities, with IC50 values at 88.4 and 168.9 nM, respectively, and exhibited antiproliferative capacities against hematological and solid tumor cells. Meanwhile, 8e showed high selectivity for CDK9 and HDAC1, remarkably induced MV-4-11 cell apoptosis and S cell cycle arrests. Furthermore, 8e possessed a significant antitumor potency with a T/C value of 29.98% in the MV-4-11 xenograft model. Interestingly, a potent FLT3/HDAC dual inhibitor 9e was also identified (FLT3/HDAC1/3 IC50 = 30.4/52.4/14.7 nM) and found to possess powerful apoptosis induction ability in MV-4-11 cell and potent antiproliferative capacities against FLT3 mutant-transformed BaF3 cells. Overall, our work provided valuable lead compounds for dual inhibitors with potent anticancer activity.

Discovery of SILA-123 as a Highly Potent FLT3 Inhibitor for the Treatment of Acute Myeloid Leukemia with Various FLT3 Mutations.

The FLT3-ITD (internal tandem duplication) mutant has been a promising target for acute myeloid leukemia (AML) drug discovery but is now facing the challenge of resistance due to point mutations. Herein, we have discovered a type II FLT3 inhibitor, SILA-123. This inhibitor has shown highly potent inhibitory effects against FLT3-WT (IC50 = 2.1 nM) and FLT3-ITD (IC50 = 1.0 nM), tumor cells with the FLT3-ITD mutant such as MOLM-13 (IC50 = 0.98 nM) and MV4-11 (IC50 = 0.19 nM), as well as BaF3 cells associated with the FLT3-ITD mutant and point mutations like BaF3-FLT3-ITD-G697R (IC50 = 3.0 nM). Moreover, SILA-123 exhibited promising kinome selectivity against 310 kinases (S score (10) = 0.06). In in vivo studies, SILA-123 significantly suppressed the tumor growth in MV4-11 (50 mg/kg/d, TGI = 87.3%) and BaF3-FLT3-ITD-G697R (50 mg/kg/d, TGI = 60.0%) cell-inoculated allograft models. Our data suggested that SILA-123 might be a promising drug candidate for FLT3-ITD-positive AML.

Baicalein attenuates oxidative damage in mice haematopoietic cells through regulation of PDGFRβ

Platelet-derived growth factor receptor β (PDGFRβ) plays a crucial role in murine haematopoiesis. Baicalein (BAI), a naturally occurring flavonoid, can alleviate disease damage through anti-oxidative, anti-apoptotic, and anti-inflammatory mechanisms. However, whether BAI attenuates oxidative damage in murine haematopoietic cells by PDGFRβ remains unexplored. In this study, we utilized a tert-butyl hydroperoxide (TBHP)-induced BaF3 cell injury model and an ionising radiation (IR)-induced mice injury model to investigate the impact of the presence or absence of PDGFRβ on the pharmacological effects of BAI. In addition, the BAI-PDGFRβ interaction was characterized by molecular docking and dynamics simulations. The results show that a specific concentration of BAI led to increased cell viability, reduced reactive oxygen species (ROS) content, upregulated nuclear factor erythroid 2-related factor 2 (NRF2) expression, and its downstream target genes heme oxygenase 1 (HO-1) and NAD(P)H Quinone Dehydrogenase 1 (NQO1), and activated protein kinase B (AKT) pathway in cells expressing PDGFRβ plasmid and experiencing damage. Similarly, BAI elevated lineage−Sca1+cKIT+ (LSK) cell proportion, promoted haematopoietic restoration, enhanced NRF2-mediated antioxidant response in PDGFRβ+/+ mice. However, despite BAI usage, PDGFRβ knockout mice (PDGFRβ−/−) showed lower LSK proportion and less antioxidant capacity than the total body irradiation (TBI) group. Furthermore, we demonstrated an interaction between BAI and PDGFRβ at the molecular level. Collectively, our results indicate that BAI attenuates oxidative stress injury and helps promote haematopoietic cell recovery through regulation of PDGFRβ.

Discovery of LHQ490 as a highly selective fibroblast growth factor receptor 2 (FGFR2) inhibitor

Fibroblast growth factor receptor 2 (FGFR2) represents an appealing therapeutic target for multiple cancers, yet no selective FGFR2 inhibitors have been approved for clinical use to date. Here, we report the discovery of a series of new selective, irreversible FGFR2 inhibitors. The representative compound LHQ490 potently inhibited FGFR2 kinase activity with an IC50 of 5.2 nM, and was >61-, >34-, and >293-fold selective against FGFR1, FGFR3, and FGFR4, respectively. LHQ490 also exhibited high selectivity in a panel of 416 kinases. Cell-based studies revealed that LHQ490 efficiently suppressed the proliferation of BaF3-FGFR2 cells with an IC50 value of 1.4 nM, and displayed >70- and >714-fold selectivity against BaF3-FGFR1 and the parental BaF3 cells, respectively. More importantly, LHQ490 potently suppressed the FGFR2 signaling pathways, selectively inhibited FGFR2-driven cancer cell proliferation, and induced apoptosis of FGFR2-driven cancer cells. Taken together, this study provides a potent and highly selective FGFR2 inhibitor for further development of FGFR2-targeted therapeutic agents.

Discovery of Novel 5,6-Dihydro-4H-pyrido[2,3,4-de]quinazoline Irreversible Inhibitors Targeting Both Wild-Type and A775_G776insYVMA Mutated HER2 Kinases.

HER2 mutations were seen in 4% of non-small-cell lung cancer (NSCLC) patients. Most of these mutations (90%) occur as an insertion mutation within the exon 20 frame, leading to the downstream activation of the PI3K-AKT and RAS/MAPK pathways. However, no targeted therapies have yet been approved worldwide. Here a novel series of highly potent HER2 inhibitors with a pyrido[2,3,4-de]quinazoline core were designed and developed. The derivatives with the pyrido[2,3,4-de]quinazoline core displayed superior efficacy of antiproliferation in BaF3 cells harboring HER2insYVMA mutation compared with afatinib and neratinib. Rat studies showed that 8a and 9a with the newly developed core have good pharmacokinetic properties with an oral bioavailability of 41.7 and 42.0%, respectively. Oral administration of 4a and 10e (30 mg/kg, QD) displayed significant antitumor efficacy in an in vivo xenograft model. We proposed promising strategies for the development of HER2insYVMA mutant inhibitors in this study.

EX VIVO DRUG SENSITIVITY EVALUATION OF A RARE ZMYM2::FGFR1+ LEUKEMIA PATIENT

Introduction: 8p11 myeloproliferative syndrome (EMS) is a hematologic malignancy caused by a translocation of FGFR1, most commonly joined with zinc- finger domain ZNF198 (ZMYM2). Pemigatinib is approved for FGFR fusion positive myeloid/lymphoid neoplasms (MLNs). Material and Methods: We analyzed samples and clinical data from a patient with a ZMYM2::FGFR1 translocation. Ex vivo drug sensitivity assays examined patient mononuclear cells isolated from blood and bone marrow. ZMYM2::FGFR1 transformed BaF3 cells were evaluated with single agent and drug combination panels. Sanger sequencing of the FGFR portion of the fusion sought to identify potential Ponatanib resistance mutations. Results: This case involves a 36-year-old man with 8p11 myeloproliferative syndrome and a ZMYM2::FGFR1 fusion along with a RUNX1R201Q mutation treated with HyperCVAD with Ponatinib, then HyperCVAD with Ponatinib and Bortezomib followed by Pemigatinib. Hematologic response suggested efficacy of Pemigatinib alone. Over time, the patient developed resistance to Ponatinib while maintaining sensitivity to Pemigatinib. Sequencing identified an amino acid substitution (FGFR1F686L; ZMYM2::FGFR1F1171L) within the kinase domain that could contribute to Ponatinib resistance. Bortezomib and Axitinib exhibited high efficacy on the patient’s sample. Ex vivo drug assays performed on ZMYM2::FGFR1 transformed BaF3 cells confirmed the high effectiveness of Pemigatinib and Ponatinib. Other FGFR inhibitors, including Olverematinib, AZD4547, Axitinib, Cediranib, Dovitinib, and Lenvatinib, showed exquisite sensitivity. Conclusions: Ex vivo drug sensitivity assays demonstrated the high efficacy of FGFR inhibitors in ZMYM2::FGFR1 fusion-positive leukemia cells and a fusion- expressing cell line. Mutations in the FGFR1 kinase domain (ZMYM2::FGFR1F1171L) may contribute to Ponatinib insensitivity. Further investigations are needed to determine if Pemigatinib alone is sufficient for treating ZMYM2::FGFR1 fusion-positive patients.

Abstract C151: BLU-451 is a CNS-penetrant, wild-type-sparing EGFR inhibitor with broad coverage of uncommon EGFR mutations across structure-based subsets

Abstract Introduction: Uncommon EGFR mutations in non-small cell lung cancer (NSCLC), including exon 20 insertion and atypical mutations, are generally associated with poorer clinical outcomes than common EGFR mutations. Patients (pts) with these mutations have limited effective therapeutic options. Afatinib is the only approved agent for uncommon mutations but is associated with high rates of toxicity and limited central nervous system (CNS) penetration. Amivantamab and mobocertinib are approved for patients with relapsed EGFR exon 20 insertion NSCLC but are associated with limitations in efficacy and CNS activity. BLU-451 is an investigational, CNS-penetrant, EGFR-wild-type (WT)–sparing, selective inhibitor against exon 20 insertion and uncommon EGFR mutations that is currently being evaluated in the phase 1/2 CONCERTO study (NCT05241873). Here, we report on the prevalence of uncommon EGFR mutations from a single center, real-world data set (MD Anderson Cancer Center [MDACC]), and report preclinical activity of BLU-451 on a broad spectrum of uncommon EGFR mutations by structure classification. Methods: BLU-451 cellular activity was evaluated in engineered BaF3 cell lines expressing 62 EGFR kinase domain mutations as well as in cell lines dependent on WT EGFR, using the CellTiter-Glo® Luminescent Cell Viability Assay and a phosphorylation-specific EGFR AlphaLISA® assay. The MDACC Moon Shot™ Genomic Marker-Guided Therapy Initiative (GEMINI) database was searched for pts with NSCLC whose tumors harbored EGFR kinase domain mutations. Results: In the MDACC GEMINI database, a total of 1495 unique patients with NSCLC harboring EGFR mutations were identified, including 1025 with classical mutations (exon 19 deletion and L858R) with or without T790M, 223 with exon 20 insertion mutations, and 247 with only atypical mutations. In BaF3 cells, BLU-451 demonstrated nanomolar potency in multiple atypical and exon 20 insertion mutation cell lines with selectivity against WT EGFR. Conclusion: Atypical EGFR mutations represent a sizable NSCLC pt population, of similar magnitude to that of EGFR exon 20 insertion mutations. BLU-451 preclinical data in EGFR atypical and exon 20 insertion mutations showed broad, potent, and selective activity, supporting continued evaluation of BLU-451 in the phase 1/2 CONCERTO study in pts with advanced or metastatic NSCLC harboring uncommon EGFR mutations. Citation Format: Xiuning Le, Yves Millet, Monique Nilsson, Aditya Dhande, Jeffrey Keats, Holly Ponichtera, Joseph Kim, Junqin He, Yasir Y. Elamin, John V. Heymach, Chiara Conti, Stephanie Lee. BLU-451 is a CNS-penetrant, wild-type-sparing EGFR inhibitor with broad coverage of uncommon EGFR mutations across structure-based subsets [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr C151.

Abstract B153: Resistance mechanisms to mobocertinib in treating NSCLC with EGFR exon 20 insertion mutations

Abstract Background: Mobocertinib is an oral epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI) that received FDA accelerated approval for non-small cell lung cancer (NSCLC) with EGFR exon 20 insertion (ex20ins) mutations, based on data from a pivotal phase 1/2 study of mobocertinib (NCT02716116). In platinum-pretreated patients (pts) with EGFR ex20ins NSCLC (N=114), the overall response rate (ORR) was 28%, median duration of response was 17.5 months, and median progression-free survival was 7.3 months. Despite this encouraging clinical activity, de novo and acquired resistant mechanisms to mobocertinib remain largely unknown. Methods: Tumor samples and circulating tumor DNA (ctDNA) samples were obtained from platinum-pretreated pts with EGFR ex20ins+ NSCLC treated with mobocertinib (NCT02716116) and subjected to next-generation sequencing (NGS) analyses. CtDNA was collected at baseline, cycle 3 day 1 (C3D1) and progression per protocol. Tumor growth assay was performed in BaF3 cells and patient-derived xenograft models to evaluate efficacy of combination therapies to overcome resistance. Results: At baseline, in tumor (n=56), the combined presence of BRAF and PIK3CA mutations alone (n=9) or together with copy number gains (CNV) in EGFR, MYC, CDK4, or CCND1 (n=19) was significantly associated with inferior ORR to mobocertinib with odd ratios of ‘infinity’ (p=0.045) and 13.21 (p=0.0047), respectively. Individual co-occurring gene mutations and CNV were not significantly associated with differential clinical outcomes. Longitudinal analysis of paired tumor-blood samples at baseline and C3D1 showed that 22 out of 55 pts (40%) achieved clearance at C3D1, including 81.2% (13/16) of PR pts, 50% of SD pts, and 20% of PD pts. CtDNA was also used to assess emerging mutations after mobocertinib progression after at least 5 months of treatment (n=18). TP53 (n=11) and acquired secondary EGFR (n=5) were the most common genes with emerging variants, including EGFR T790M (n=4) and D379E (n=1). With this observation, T790M was engineered in Ba/F3 cells in the context of EGFR ex20ins mutations (H773_V774insNPH and 769_D770insASV). T790M did confer resistance to mobocertinib in vitro, and to all EGFR TKIs tested including osimertinib. In patient-derived xenograft models (H773_V774insNPH and 769_D770insASV), the combination of mobocertinib plus the bispecific monoclonal antibody amivantamab demonstrated greater antitumor activity than either agent alone. Conclusions: Our results indicate that bypass pathway alterations are associated with de novo resistance whereas T790M emergence mediates acquired resistance to mobocertinib. Future research is warranted to determine the potential clinical benefits of combination strategies in patients with EGFR ex20ins+ NSCLC. Citation Format: Xiuning Le, Monique Nilsson, Sampurna Chatterjee, Zhenqiang Su, Junqin He, Hibiki Udagawa, Xiaoxing Yu, Alissa Poteete, Qian Huang, John V Heymach, Sylvie Vincent. Resistance mechanisms to mobocertinib in treating NSCLC with EGFR exon 20 insertion mutations [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr B153.

Abstract B167: Preclinical characterization of THE-349, a mutant-selective, CNS-active, fourth-generation EGFR inhibitor to overcome T790M- and C797S-mediated resistance in NSCLC

Abstract Background: EGFR activating mutations are observed in 10-50% of NSCLC patients. Although the common mutations (L858R [L] and exon 19 deletions [D]) are initially sensitive to first-, second-, and third-generation EGFR inhibitors (e.g., erlotinib [1G], afatinib [2G], and osimertinib [3G], respectively), on-target resistance is observed in a substantial percentage of patients, with T790M (T) and C797S (C) observed most frequently (post-1G/2G and post-3G, respectively). Furthermore, EGFR mutational heterogeneity can increase during treatment with existing inhibitors, inhibition of wild type (WT) EGFR leads to dose-limiting toxicities, and tumors commonly metastasize to the brain. We have designed THE-349 to be a fourth-generation EGFR inhibitor with potent activity against all 8 major single- (L, D), double- (LT, DT, LC, DC), and triple- (LTC, DTC) mutant variants, selectivity over WT EGFR, and activity in the CNS. Methods: Kinome selectivity was evaluated biochemically against a panel of 412 kinases. In vitro potency was determined by assessing effects (IC50s) on human and BaF3 cell lines expressing WT or mutant forms of EGFR. Efficacy studies were conducted using engineered BaF3 cell lines, a luciferase-tagged human NSCLC cell line, and a patient-derived xenograft (PDX) model dosed orally, once-daily at levels that did not exceed the maximum tolerated dose (40 mg/kg THE-349 and 25 mg/kg osimertinib). Results:THE-349 potently inhibited the biochemical activity of all major EGFR mutant variants (IC50s <2 nM) with a high degree of kinome selectivity. In engineered BaF3 cells in vitro, THE-349 potently inhibited viability of all 8 major EGFR mutant variants (L, LT, LC, LTC, D, DT, DC, and DTC), with IC50s <6 nM and with ≥10-fold selectivity over WT EGFR. Similarly, THE-349 demonstrated robust anti-tumor activity against the same 8 EGFR variants in vivo, in all cases inducing deep tumor regressions (>80% TR) in mice implanted with engineered BaF3 cells. In a PDX model from an osimertinib-resistant tumor containing D and DTC variants, THE-349 induced deep and sustained regressions (99% TR) through 56 days of dosing, and tumor regrowth that occurred during a subsequent 5-week dosing holiday was reversed (88% TR) upon redosing with THE-349. In an intracranial tumor model using a triple-mutant (LTC) NSCLC cell line, THE-349 significantly prolonged median survival (from 42.5 to 71.5 days), while osimertinib had no effect. THE-349 has a favorable ADME profile and promising safety profile in IND-enabling toxicology studies. Conclusion: THE-349 is a fourth-generation, CNS-active, mutant-selective EGFR inhibitor that has potent, single-agent activity against all major classes of EGFR activating and resistance mutations. A phase 1 clinical trial of THE-349 is planned. Citation Format: Sen Zhang, Sara Nadworny, Wei-Sheng Huang, Adam Talbot, Emily Ye, Narayana Narasimhan, William C Shakespeare, Victor M Rivera. Preclinical characterization of THE-349, a mutant-selective, CNS-active, fourth-generation EGFR inhibitor to overcome T790M- and C797S-mediated resistance in NSCLC [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr B167.

Ex Vivo Drug Sensitivity Evaluation of a ZMYM2::FGFR1 Fusion-Positive 8p11 Myeloproliferative Syndrome (EMS) Leukemia

Introduction : Fibroblast growth factor receptors (FGFRs) are conserved single transmembrane receptor tyrosine kinases (RTKs) with an extracellular ligand-binding domain and a cytoplasmic tyrosine kinase domain. They play vital roles in cellular proliferation, survival, development, fetal organogenesis, metabolism, and tissue repair. 8p11 myeloproliferative syndrome (EMS) is a hematologic malignancy caused by a translocation of the fibroblast growth factor receptor 1 (FGFR1) gene on chromosome 8p11-12. The most common fusion partner of FGFR1 is the zinc-finger domain ZNF198 (also known as ZMYM2) on chromosome 13q12. Pemigatinib is approved for FGFR fusion positive myeloid/lymphoid neoplasms (MLNs), and other FGFR inhibitors are being tested in clinical trials. However, EMS patients still face a poor prognosis and drug resistance, necessitating further research to overcome these challenges. This study evaluated ex vivo drug screening assay data generated from ZMYM2::FGFR1 positive primary leukemia samples throughout the course of an EMS patient's clinical response and validated these findings on a ZMYM2::FGFR1 positive cell line. Methods : Ex vivo and drug screening experiments were performed on freshly isolated primary patient samples and a ZMYM2::FGFR1-expressing cell line. The fusion was confirmed using FISH, and additional clinical specimens were collected with informed patient consent. Ex vivo drug sensitivity assays were conducted on patient mononuclear cells isolated from blood and bone marrow. IL-3 dependent BaF3 cells were infected with retrovirus containing a ZMYM2::FGFR1-V5 construct. ZMYM2::FGFR1 transformed BaF3 cells were evaluated with single agent and drug combination panels. Sanger sequencing of the FGFR portion of the fusion was performed on patient samples to confirm the breakpoint and identify potential mutations affecting sensitivity to Ponatinib throughout the course of treatment. Results : Sample were obtained with informed consent from a 36-year-old man diagnosed with 8p11 myeloproliferative syndrome and a ZMYM2::FGFR1 fusion along with a RUNX1 R201Q mutation. Ex vivo drug screens performed on isolated mononuclear cells demonstrated sensitivity to Ponatinib and Pemigatinib. He underwent treatment with HyperCVAD plus Ponatinib and subsequently HyperCVAD with Ponatinib and Velcade (Bortezomib) to CR1, FISH for FGFR1 rearrangement was undetected. He was scheduled to proceed with hematopoietic stem cell transplant (HSCT), however his pre-transplant bone marrow biopsy showed return of his FGFR1 translocation by FISH. Ex vivo drug screening assays confirmed resistance to Ponatinib, but continued sensitivity to Pemigatinib. He was transitioned to treatment with single agent Pemigatinib and was able to re-clear his FGFR1 fusion by FISH, and has since undergone hematopoietic stem cell transplantation. He remains in remission on post-transplant Pemigatinib maintenance therapy. Sanger sequencing performed at the time of progression on Ponatinib identified a nucleotide alteration resulting in an amino acid substitution (FGFR1 F686L; ZMYM2::FGFR1 F1171L) within the kinase domain that could contribute to decreased Ponatinib sensitivity. Bortezomib and Axitinib exhibited high efficacy on the patient's sample. Ex vivo drug assays performed on ZMYM2::FGFR1 transformed BaF3 cells confirmed the efficacy of Pemigatinib and Ponatinib. Other FGFR inhibitors, including Olverematinib, AZD4547, Axitinib, Cediranib, Dovitinib, and Lenvatinib, also demonstrated exquisite sensitivity. Despite extensive screening, no other single agents or drug combinations exhibited increased effectiveness in the ZMYM2::FGFR1 transformed BaF3 cells except for Trametinib, a MEK inhibitor, and the combination of Belvarafenib (RAF inhibitor) and Gilteritinib (FLT3 inhibitor). Conclusions : Ex vivo drug sensitivity assays demonstrated the highly selective efficacy of FGFR inhibitors in ZMYM2::FGFR1 fusion-positive leukemia cells and a fusion-expressing BaF3 cell line. Mutations in the FGFR1 kinase domain (ZMYM2::FGFR1 F1171L) could contribute to Ponatinib insensitivity. These ex vivo drug screening results provide further support for ongoing clinical trials which are investigating the use of single agent Pemigatinib and other FGFR1 inhibitors for the treatment of patients with FGFR1-fusion positive leukemias.

ITGB3 Promotes the Progression of JAK2V617F-Positive Myeloproliferative Neoplams By Regulating Calreticulin to Inhibit Cellular Autophagy

O bjectives: Integrins are integral cell-surface proteins composed of an alpha chain and a beta chain, of which integrin beta 3 (ITGB3) was known to participate in cell adhesion as well as cell-surface mediated signaling and plays vital roles in different tumors. However, the role of ITGB3 in JAK2V617F-positive classical myeloproliferative neoplasms (cMPNs) remians unclear, and the aim of this study was to explore the effect of ITGB3 on cellular autophagy in JAK2V617F-positive cMPN cell line and its underlying mechanisms. Methods: ITGB3 expression in bone marrows from JAK2V617F-positive cMPN patients compared to normal controls were detected by quantitative reverse-transcription PCR (qPCR) and further validated by western blotting. Cell models of cMPNs were constructed using human HEL cell lines carrying JAK2V617F mutation and cytokine-dependent wild type BaF3 cells (Jak2 V617F BaF3 cells) with ectopic expression of Jak2 V617F seperately to perform phenotype and mechanism investigation. The putative targets of STAT5a on the promoters of ITGB3 were disclosed by public databases and a dual-luciferase reporter assay and chromatin immunoprecipitation assay (ChIP) was used to analyze the binding of STAT5a to ITGB3 promoter region. To observe the role of ITGB3 played in cMPN progression, stable-transfected HEL cell line with ITGB3 knockdown or overexpression were established by lentivirus packaging and cell transfection. Cell phenotype including cell proliferation, apoptosis and cell cycle distribution were detected by soft agar colony formation assay, BrdU staining, flow cytometry and Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assays. The variations of autophagic flux after ITGB3 dysregulation in HEL cells was analyzed using mRFP-GFP-LC3 adenovirus transfection and fluorescence microscopy, and LC3-II/I ratio as well as autophagy-related protein were detected by western blotting. Transmission electron microscopy was used to observe the formation of intracellular autophagosomes and autophagic lysosomes. RNA sequencing and GSEA analysis were applied to predict the downstream pathway and putative targets of ITGB3. Western blotting, immunofluorescence and qPCR were performed to detect the transcription and expression levels of genes. Results: 1.Western blotting and qRT-PCR detection showed increased expression of ITGB3 in bone marrow of JAK2V617F-positive cMPN patients compared to normal controls (A-B). Also, the evaluation of ITGB3 in a variety of myeloid tumor cell lines (HEL, HL60, K562, KG-1a) and wild-type BaF3 cells as well as Jak2 V617F BaF3 cells revealed that ITGB3 protein level is the highest in HEL (which harboring the JAK2V617F) and Jak2 V617F BaF3 cells (C-F). 2. Dual-luciferase reporter assay showed that STAT5a significantly induced the transcription activities of promoters of ITGB3 and inhibition of STAT5a reduced the transcription activities of promoters of ITGB3 (G-H). ITGB3 knockdown (I) in HEL cells reduced the proliferation capacity (J-L), promoted early apoptosis (M-O) and caused cell cycle arrest (P-Q). While ITGB3 overexpression in HEL cells (R) reduced the cell cycle arrest (S) and apoptosis (T-U). 3. Autophagic flux analysis showed that ITGB3 knockdown promoted the autophagic flux in HEL cells (V-X). Inhibition of ITGB3 increases the synthesis and degradation of autophagosomes and accelerates the process of cellular autophagy (Y-Z). Further identification of DEGs in ITGB3-dysregulated HEL cells (AA-AB) reveals that ITGB3 inhibits the expression of calreticulin (AC-AE), and ITGB3 might be involved in the regulation of autophagy in HEL cells through the regulation of calreticulin. Conclusions: 1. ITGB3 is significantly activated in HEL cell lines carrying the JAK2V617F mutation. 2. ITGB3 protein acts as a pro-oncogene in JAK2V617F-positive myeloproliferative neoplams progression by regulating calreticulin to inhibit autophagy, which deserves more in-depth study in JAK2V617F mutation-positive cMPNs.

DUSP1 Specific Protac Selectively Targets the JAK2 V617F Expressing Cells

Constitutive JAK-STAT signaling resulting from mutations in JAK2 V617F and certain growth-factor receptors has provided a strong rationale for targeting JAK2 kinase activity in myeloproliferative neoplasms (MPNs). Although several JAK2 inhibitors have been approved for MPN treatment, their clinical efficacy is limited to alleviating the constitutional symptoms associated with inflammatory cytokine signaling. These inhibitors are not cytotoxic and only exert a cytostatic response, failing to eradicate the malignant clone, induce molecular remission, or prevent progression to acute myeloid leukemia (AML). The inability of JAK2 TKIs to fully suppress the inflammatory cytokine overproduction, a key feature of MPN development and transition to AML, contributes to clonal persistence and TKI refractoriness. Recently, we reported that the cytokine signaling, in the context of JAK2 V617F signaling induces the expression of DUSP1, which enhances P53 degradation that leads to TKI refractoriness. Enhanced DUSP1 expression blocks P53 phosphorylation at Serine 15 (S15 phosphorylation prevents its interaction with MDM2) by inhibiting the P38 kinase activity. Consequently, reduced phosphorylation under JAK2 V617F signaling enhances P53 turnover. Deletion of DUSP1 enhances P38 kinase activity, leading to greater P53 stabilization and expression, which selectively induce cell death in JAK2 V617F expressing MPN cells while sparing normal cells. However, chemical inhibition of DUSP1 using a small molecule inhibitor (BCI) was ineffective in achieving synthetic lethality to JAK2 V617F cells, mainly due to pERK1/2 rebound caused by the off-target inhibition of DUSP6. Reintroduction of DUSP6 and BCI treatment restored JAK2 V617F clonal selectivity. This study provided the first mechanistic basis of TKI refractoriness in JAK2 targeted MPNs and suggested that selectively targeting DUSP1 could offer a stable or curative response in JAK2 V617F -driven MPNs. To address this, we developed a DUSP1-protac, a novel and highly potent DUSP1 selective PROTAC. Treatment of BaF3 cells expressing JAK2 V617F with DUSP1-protac resulted in dose- and time-dependent degradation of DUSP1, accompanied by increased P38 activity and P53 stabilization. The maximal level of DUSP1 degradation (Dmax) achieved was 95% with a DC50 of 70 nM/L within 24 hours. Pre-treatment with the proteasome inhibitor MG132, but not the lysosomal inhibitor chloroquine, reversed DUSP1 degradation, confirming that degradation occurs via the 26S-proteasome. As expected, DUSP1-protac induced cytotoxicity specifically in JAK2 V617F expressing cells, with a cellular IC50 of 50 nM. No toxicity was observed in BaF3 cells or those expressing MPL or CALR variants at concentrations up to 1000 nM, confirming its selectivity. In conclusion, our data suggest that DUSP1-protac is an exceptionally potent first-in-class DUSP1 selective PROTAC. It exerts a cytotoxic response specifically in JAK2 V617F expressing cells by enhancing P53 expression. Cellular uptake experiments and efficacy studies in primary cells are currently underway and will be presented in subsequent reports. The development of DUSP1-protac represents a promising approach for targeting JAK2 V617F -driven MPNs, offering potential benefits in achieving a stable or curative therapeutic response.

Fedratinib Overcomes Ruxolitinib Resistance through Inhibition of the Interferon Signaling Pathway

Background: Myelofibrosis (MF) is a clonal myeloproliferative neoplasm characterized by hyperactive JAK-STAT signaling, bone marrow fibrosis, extramedullary hematopoiesis and splenomegaly. Ruxolitinib (RUX) and Fedratinib are both JAK inhibitors used for the treatment of patients with intermediate or higher risk MF. While RUX is the first line treatment for patients with MF, about 50% of the patients discontinue treatment due to lack of efficacy or intolerance (Harrison et al., Ann. Hematol. 2020) after 3 years. Fedratinib is used as a second line therapy in MF based on efficacy from the JAKARTA2 study. The recently concluded FREEDOM and FREEDOM2 studies further support this. In this work, using in vitro approaches, we have explored the mechanistic basis of fedratinib's ability to overcome RUX resistance. Pharmacologically, Fedratinib binds with high affinity to the substrate-binding site and with low affinity to the ATP-binding site of JAK2(Kesarwani etal., Sci. Rep. 2015) while RUX binds only to the ATP-binding site. Previous studies on RUX resistance have shown acquired mutations driving resistance to RUX but not to Fedratinib. Here, we use RUX sensitive and resistant BaF3 (expressing human JAK2 WT or V617F) cell lines to examine the mechanism of resistance to RUX and the mechanism of efficacy of Fedratinib in RUX resistance. Methods: BaF3 cell lines overexpressing JAK2 WT or JAK2 activating mutation V617F were incrementally exposed to RUX over 3 weeks (up to IC 90) to induce resistance. Cell proliferation and phosphorylation of STAT5 in Fedratinib and RUX-treated cells were measured using celltiter glo and immunoblotting, respectively. RNAseq and ATAC-seq analyses were performed in triplicates by treating the relevant cell lines with DMSO, RUX or Fedratinib at two timepoints (6 and 15 hours). Pathway analysis was performed on RNAseq data using Metacore®. Results and Discussion: Ruxolitinib resistant BaF3 JAK2V617F cells showed minimal inhibition of proliferation (<10%) when treated with RUX but maintained sensitivity towards Fedratinib (IC 50 650nM vs 1552nM in RUX sensitive and resistant cells respectively) in 24-hour proliferation assays. Biochemical analysis revealed that Fedratinib inhibited JAK-STAT signaling in the RUX resistant cell line while RUX was unable to do so as measured by p-STAT5. Similar results were observed in BaF3-JAK2-WT cells as well. To further understand the mechanism of RUX-resistance and differential activity of RUX and Fedratinib, we performed RNAseq analysis on our RUX sensitive and resistant models before and after RUX and Fedratinib treatment. Myelofibrosis is associated with aberrant cytokine production and pro-inflammatory signaling that are mediated through activation of TNF-α and NF-κB signaling (Dunbar et al., Blood 2023). Consistent with this, RNAseq analysis of BaF3 JAK2 V617F cells treated with RUX or Fedratinib showed effective inhibition of these pathways by both agents as early as 6 hours. In the RUX resistant cells, while RUX did not have any significant pathway level changes, the top enriched pathways upon treatment with Fedratinib were predominantly interferon signaling pathways which includes JAK-STAT signaling suggesting that Fedratinib's efficacy in MF is not impacted by RUX resistance. To understand the mechanism of resistance, comparison of gene expression data from RUX senstive and RUX resistant cells without any drug treatment revealed minimal gene expression/pathway level differences suggesting that the mechanism of resistance could be driven by genetic (Downes et al. NPJ Precis Oncol, 2021) or epigenetic changes(Dunbar et al., Blood 2023). Ongoing analyses includes whole genome sequencing and ATAC-seq to investigate potential mutations and chromatin accessibility changes during resistance acquisition to RUX and how Fedratinib may overcome these. Conclusion: Our stable RUX resistant preclinical model demonstrates that Fedratinib is effective in overcoming RUX resistance by continuing to target key pathways in MPN biology including interferon signaling. Resistance to RUX on the other hand seems to be driven through potential genetic or epigenetic changes based on the minimal changes observed in gene expression profiles. Our ongoing analyses will reveal these potential genetic and epigenetic modifications associated with RUX resistance and explain the differential activity of RUX versus Fedratinib.

JAK2V617F Activates IL-10R Signalling Potentially through Transactivation of JAK1

Classical myeloproliferative neoplasms (MPNs) arise from somatic mutations in haematopoietic stem cells (HSCs) that lead to unregulated proliferation of mature myeloid cells. The most common mutation associated with MPNs is JAK2 V617F, this causes constitutive JAK-STAT signalling leading to excessive production of mature myeloid cells. In humans, for MPN to arise, a JAK2 V617F HSC must have a selective advantage over WT HSC. However, in mouse MPN models Jak2 V617F HSCs do not display an overt selective advantage. This suggests that unique selective pressures may be present among those predisposed to acquire MPN that allow for the emergence of Jak2 V617F clones. We have identified defects in the IL-10R signalling pathway among MPN patients, with evidence that this defect is an intrinsic not acquired abnormality. In mice, we found that the blockade of IL-10R extends the cycling of WT but not Jak2 V617FHSC in response to inflammatory stimuli and hastens proliferation-induced WT HSC exhaustion. We hypothesized that IL-10R blockade may create an environment that affords Jak2 V617F HSC a selective advantage, indeed we found that IL-10R blocking antibody allowed Jak2 V617F cells to outcompete WT cells in mouse transplant experiments. From these mouse data, we hypothesized that Jak2 V617Fenhances IL-10R signalling. To test this hypothesis, we created Ba/F3 cell lines co-expressing IL-10Rα and Jak2 V617F. We found that Jak2 V617F enhances growth at limiting concentrations of IL-10. We also found that cytokine-independent IL-10Rα Jak2 V617F clones (but never IL-10Rα Jak2 WTor IL-10Rα cells) emerge at day 8-10 in culture after withdrawal of cytokines. We performed a limiting dilution assay to pinpoint the proportion of IL-10R Jak2 V617F cells capable of surviving IL-3 withdrawal. One in 126 IL-10Rα Jak2 V617F cells has transforming ability, whereas 1 in 1.4 MPL Jak2 V617F has transforming ability. Together, these data support our hypothesis that Jak2 V617F enhances IL-10R signalling and can activate IL-10Rα, however with weaker transformation potential compared to Jak2V617F's activation of MPL signalling. JAK2 canonically does not participate in the IL-10R pathway. It has been previously shown that JAK1 can transactivate JAK2 when JAK2 V617F cells are under the stress of persistent JAK2 inhibitor exposure, and this is the purported mechanism of JAK inhibitor resistance among MPN patients. We hypothesized that JAK2 V617F can transactivate JAK1, leading to the activation of IL-10R. The same transfected BaF3 cells aforementioned were serum starved for 4 hours and stimulated with mIL-10 for 15 minutes to induce signalling. By way of Western Blot analysis, cytokine-independent Jak2 V617F IL-10Rα Ba/F3 cells showed constitutive activation of phosphorylated JAK1 and JAK2 as well as STAT3 and STAT5, consistent with transactivation. Studies to demonstrate direct interactions between JAK2 V617F and JAK1 are currently ongoing.

Asciminib Enhances Its Treatment Efficacy Synergistically in the Treatment of Chronic Myeloid Leukemia Harboring ABL1 Kinase Domain Mutation When Combined with a Reduced Dose of Ponatinib, Dasatinib, or Bosutinib, but Not with Nilotinib or Imatinib

Background: Asciminib (ASC) monotherapy has been approved for chronic myeloid leukemia (CML) treatment in the patients who failed at least 2 lines of tyrosine kinase inhibitor (TKI) therapy. Theoretically, dual inhibition of the ABL1 kinase protein is plausible by combining ASC with ATP-binding pocket inhibitors (ABPIs) including Imatinib (IMA), Dasatinib (DAS), Nilotinib (NIL), Bosutinib (BOS) or Ponatinib (PON). A phase 1 study determined the appropriate dose of ASC with fixed doses of ABPIs (IMA, DAS, NIL). However, this approach of using full dose ABPIs with variable dose of ASC would raise a concern of tolerability given that all the toxicity from the doses of ABPI will be augmented by adding even half dose of ASC, evidenced by the FASCINATION trial (Ernst et al. EHA 2023). Questions still remained such as what is the best dose for combination? Is the combination of full dose ASC with reduced dose ABPIs effective? Is this combination effective to other ABL1 kinase domain mutant CML? For the ABL1 kinase domain (KD) mutant CML, which ABPI and what dose is more effective and more synergistic than other ABPIs? Methods and Materials: To investigate the combined effect of ASC with ABPIs, we determined the IC 50 values for ASC and ABPIs in the wild-type (WT) BaF3 BCR-ABL+ cell line, and utilized the IC 50 as baselines throughout the study. From the baseline IC 50s of ASC (3nM), IMA (150nM), NIL (10nM), BOS (10nM), DAS (0.8nM) and PON (0.6nM), serially diluted ASC alone, ABPIs alone or in combination were administered to BaF3 cell lines. We conducted IC 50 determining experiment in different combination of ASCs/ABPIs/combination in different concentration (conc) on eleven different KD mutant (KDM) BaF3 cell lines, including WT, G250E, E255K, T315A, M351T, F317L, F317V, H396P, Y253F, M244V, and T315I mutant cell lines. ZIP synergy scores for these cell lines were analyzed using SynergyFinder. Results We observed that the addition of 3 nM ASC to ABPI at baseline IC 50 conc led to a higher response (% cell growth inhibition) compared to treatment with ABPI alone at baseline conc, irrespective of the mutation. Moreover, the combined treatment of ABPI at half baseline conc with 3nM ASC demonstrated similar or even higher effects than ABPI alone at IC 50 baseline conc. These results suggest that double blockade allows for the reduction of ABPI dose by half while maintaining cell inhibition activity. According to its sensitivity to ASC monotherapy and combination, we have stratified the cell lines into 3 categories. High sensitive cell lines to ASC monotherapy (i.e. WT, G250E, and E255K) achieving 100% of response rate when combined with ABPI. Also, T315A mutation showed a significant synergistic effect (ZIP = 12.91~21.75) with the combination of ASC 3nM with a half conc of ABPI, resulting in 1.90-2.43 times higher inhibitory effect than ABPI monotherapy.Intermediate sensitive cell lines (i.e. M351T and F317L) displaying 69-85% inhibition efficiency with ASC 6nM combined with ABPI, without significant increases in all ABPI conc.Low sensitive cell lines (i.e. F317V, H396P, Y253F, M244V, and T315I) exhibiting unique resistance profiles that varied with different combinations. Notably, F317V and F317L mutations showed resistance to DAS. When combined with ASC 3nM, F317V showed restored sensitivity with IMA or NIL than with DAS, while F317L better with DAS. Moreover, the H396P, Y253F, and M244V mutations demonstrated higher sensitivities with BOS or DAS. Interestingly, in the combination treatment with ASC at 3 or 6 nM, with exception of the F317V and T315I mutations, both DAS and PON exhibited a potent efficacy. High resistance of T315I to ABPIs can be overcome with combination of ASC at baseline conc with reduced dose PON. In the case of T315I, the combination of 3nM ASC with a half conc PON resulted in a higher inhibitory effect than baseline conc PON alone. Conclusion: The present study demonstrated that a half of baseline conc ABPIs in combination with ASC is as effective as other ABPIs not just in WT but also in other ABL1 KDM CML cell lines. Different CML cell lines harboring different ABL KDM has different treatment spectrum on optimal ABPI drug as well as optimal drug conc. This result will be useful to design future clinical trial of dual blockade of ASC with other ABPIs considering the ABL KDM profiles. It also emphasizes the importance of ABL KDM testing prior to ASC monotherapy or combination with other ABPIs.

Design, synthesis and biological evaluation of 2-aminopyrimidine derivatives as potent FLT3 inhibitors

Acute myeloid leukemia (AML) is an aggressive cancer, which is characterized by clonal expansion of myeloid progenitors in the bone marrow and peripheral blood. FMS-like tyrosine kinase 3 (FLT3) mutations are the most frequently identified mutations, present in approximately 25–30 % AML patients, making FLT3 inhibitors a crucial treatment option for AML. In this study, we described the design, synthesis and biological evaluation of a series of 2-aminopyrimidine derivatives as potent FLT3 inhibitors. Notably, compound 15 displayed potent kinase inhibitory activities against FLT3 (FLT3-WT IC50 = 7.42 ± 1.23 nM; FLT3-D835Y IC50 = 9.21 ± 0.04 nM) and robust antiproliferative activities against MV4-11 cells (IC50 = 0.83 ± 0.15 nM) and MOLM-13 cells (IC50 = 10.55 ± 1.70 nM). Compound 15 also possessed potent antiproliferative activities against BaF3 cells carrying various FLT3-TKD and FLT3-ITD-TKD mutations, indicating its potential to overcome on-target resistance caused by FLT3 mutations. In summary, compound 15 showed promising potential for further exploration as a treatment of AML.

THU048 Determination Of Receptor Binding Affinity Of Growth Hormone Analogues To The Growth Hormone Receptor In A Drug Screening Context

Abstract Disclosure: S. Erlendsson: Employee; Self; Novo Nordisk. Stock Owner; Self; Novo Nordisk. A. Kulakova: Employee; Self; Novo Nordisk. S. Poulsen: Employee; Self; Novo Nordisk. Stock Owner; Self; Novo Nordisk. P. Thygesen: Employee; Self; Novo Nordisk. Stock Owner; Self; Novo Nordisk. Growth hormone (GH) and GH analogues are characterized by their ability to bind and activate the GH receptor (GHR). Binding affinity and functional activity are pivotal parameters for development and characterization of new GH analogues for treatment of growth disorders. The GHR is a member of the class I cytokine family and obtains a tripartite structure consisting of two extracellular fibronectin type III domains (ECD), a single-pass transmembrane domain (TMD), and a disordered intracellular domain (ICD). These receptors lack intrinsic kinase activity but rely on recruitment of intracellular signalling kinases and regulatory proteins. Activation of the downstream JAK-STAT signalling cascade is initiated by formation of an asymmetric GHR dimer induced by binding of GH to the GHR ECDs via two partially overlapping binding sites designated site I and II. The structural rearrangement in the ECDs propagates through the TMD and results in a separation of the ICDs which leads to activation through cross-phosphorylation of the Janus kinases 2 (JAK2). Here we utilize isothermal titration calorimetry (ITC), surface plasmon resonance (SPR) and small angle x-ray scattering (SAXS) to characterize the binding of native GH and GH analogues including somapacitan and pegvisomant to the monomeric GHR as well as an artificial soluble stabilized dimeric GHR. The GH analogues with good binding properties were subsequently tested in vitro for biological activity using a STAT3-luciferase reporter gene assay (RGA) and a proliferation assay with BAF3 cells expressing the human GHR. Both assays were established in two formats enabling testing of both receptor agonists and antagonists. Using SPR we show that the binding of all tested compounds is preserved between the monomeric and dimeric GHR with affinities ranging from near-picomolar to lower micromolar and we are subsequently able to confirm the expected stoichiometry by utilizing a combination of ITC and SAXS. In the RGA and the proliferation assay we demonstrate that a 1:2 stoichiometry is critical for receptor activation regardless of the affinity and therefore we propose high throughput screening of receptor stoichiometry as key in discovery of new growth disorder therapeutics. Presentation: Thursday, June 15, 2023

Discovery of 2-Aminopyrimidine Derivatives as Potent Dual FLT3/CHK1 Inhibitors with Significantly Reduced hERG Inhibitory Activities.

FLT3 inhibitors as single agents have limited effects because of acquired and adaptive resistance and the cardiotoxicity related to human ether-a-go-go-related gene (hERG) channel blockade further impedes safe drugs to the market. Inhibitors having potential to overcome resistance and reduce hERG affinity are highly demanded. Here, we reported a dual FLT3/CHK1 inhibitor 18, which displayed potencies to overcome varying acquired resistance in BaF3 cells with FLT3-TKD and FLT3-ITD-TKD mutations. Moreover, 18 displayed high selectivity over c-KIT more than 1700-fold and greatly reduced hERG affinity, with an IC50 value of 58.4 μM. Further mechanistic studies demonstrated 18 can upregulate p53 and abolish the outgrowth of adaptive resistant cells. In the in vivo studies, 18 demonstrated favorable PK profiles and good safety, suppressed the tumor growth in the MV-4-11 cell inoculated mouse xenograft model, and prolonged the survival in the Molm-13 transplantation model, supporting its further development.

Protein Tyrosine Phosphatase Non-Receptor 11 (PTPN11/Shp2) as a Driver Oncogene and a Novel Therapeutic Target in Non-Small Cell Lung Cancer (NSCLC)

PTPN11 encodes the SHP2 protein tyrosine phosphatase that activates the mitogen-activated protein kinase (MAPK) pathway upstream of KRAS and MEK. PTPN11/Shp2 somatic mutations occur frequently in Juvenile myelomonocytic leukaemia (JMML); however, the role of mutated PTPN11 in lung cancer tumourigenesis and its utility as a therapeutic target has not been fully addressed. We applied mass-spectrometry-based genotyping to DNA extracted from the tumour and matched the normal tissue of 356 NSCLC patients (98 adenocarcinomas (LUAD) and 258 squamous cell carcinomas (LUSC)). Further, PTPN11 mutation cases were identified in additional cohorts, including TCGA, Broad, and MD Anderson datasets and the COSMIC database. PTPN11 constructs harbouring PTPN11 E76A, A72D and C459S mutations were stably expressed in IL-3 dependent BaF3 cells and NSCLC cell lines (NCI-H1703, NCI-H157, NCI-H1299). The MAPK and PI3K pathway activation was evaluated using Western blotting. PTPN11/Shp2 phosphatase activity was measured in whole-cell protein lysates using an Shp2 assay kit. The Shp2 inhibitor (SHPi) was assessed both in vitro and in vivo in a PTPN11-mutated cell line for improved responses to MAPK and PI3K targeting therapies. Somatic PTPN11 hotspot mutations occurred in 4/98 (4.1%) adenocarcinomas and 7/258 (2.7%) squamous cells of 356 NSCLC patients. Additional 26 PTPN11 hotspot mutations occurred in 23 and 3 adenocarcinomas and squamous cell carcinoma, respectively, across the additional cohorts. Mutant PTPN11 significantly increased the IL-3 independent survival of Ba/F3 cells compared to wildtype PTPN11 (p < 0.0001). Ba/F3, NCI-H1703, and NCI-H157 cells expressing mutant PTPN11 exhibited increased PTPN11/Shp2 phosphatase activity and phospho-ERK1/2 levels compared to cells expressing wildtype PTPN11. The transduction of the PTPN11 inactivating mutation C459S into NSCLC cell lines led to decreased phospho-ERK, as well as decreased phospho-AKT in the PTPN11-mutated NCI-H661 cell line. NCI-H661 cells (PTPN11-mutated, KRAS-wild type) were significantly more sensitive to growth inhibition by the PI3K inhibitor copanlisib (IC50: 13.9 ± 4.7 nM) compared to NCI-H1703 (PTPN11/KRAS-wild type) cells (IC50: >10,000 nM). The SHP2 inhibitor, in combination with the PI3K targeting therapy copanlisib, showed no significant difference in tumour development in vivo; however, this significantly prevented MAPK pathway induction in vitro (p < 0.0001). PTPN11/Shp2 demonstrated the in vitro features of a driver oncogene and could potentially sensitize NSCLC cells to PI3K inhibition and inhibit MAPK pathway activation following PI3K pathway targeting.