Frontline Therapy Research Articles

Prospective evaluation to characterize the real-world performance of the EMBOVAC aspiration catheter for neurothrombectomy: a post-market clinical follow-up trial

BackgroundA direct aspiration first pass technique (ADAPT) is an effective alternative to stent retriever thrombectomy for patients with large vessel occlusion (LVO). The PERFECT study evaluated direct aspiration with the...

Complete response to front-line therapies is associated with long-term survival in HIV-related lymphomas in Taiwan

BackgroundThe prognosis for people living with HIV (PLWH) who develop lymphomas has been greatly improved by combination antiretroviral therapy (cART) and anti-CD20 monoclonal antibodies. However, real-world clinical data on this patient group in Asia are limited. MethodsTreatment outcomes were retrospectively examined for 104 PLWH with lymphomas between 2000 and 2019. The cohort comprised five PLWH with Hodgkin lymphoma (HL) and 99 with non-Hodgkin lymphomas, including 61 with diffuse large B-cell lymphoma (DLBCL), 19 with Burkitt lymphoma (BL), nine with primary central nervous system lymphoma (PCNSL) and ten with other subtypes. ResultsThe 5-year overall survival (OS) rates were as follows: HL (100%), PCNSL (76.2%), other subtypes (60.0%), BL (57.4%), and DLBCL (55.6%). Individuals who achieved complete response (CR) to front-line therapies had a significantly better 5-year OS rate than those without (96.2% vs. 17.8%, p < 0.001). PLWH who received cART for ≤6 months had significantly lower CD4+ T-cell counts at lymphoma diagnosis than those who received cART for longer periods (p = 0.048). Additionally, the 5-year OS rate was better for PLWH who received cART for ≤6 months before lymphomas diagnosis than those who received cART for longer periods (64.5% vs. 51.9%, p = 0.114). ConclusionsPLWH with DLBCL or BL had OS rates compatible to patients without HIV infection. Better outcomes for patients achieving CR to front-line therapy and those with shorter cART duration before lymphoma diagnosis suggest an underlying biological distinction in the lymphomas and the involvement of immunity, which warrants further studies.

Abstract CT150: Trial in progress: A phase 1b single-arm, open-label, study of emavusertib (CA-4948) in combination with azacitidine and venetoclax in acute myeloid leukemia patients in complete response with measurable residual disease

Abstract Background: Emavusertib is a novel potent oral inhibitor of interleukin-1 receptor-associated kinase 4 (IRAK4) with additional inhibitory activity against FMS-like tyrosine kinase 3 (FLT3) and CDC-like kinases (CLK1/2/4). Inhibition of these onco-proteins may induce remission thereby addressing a critical unmet need for novel therapies in acute myeloid leukemia (AML). Clinical studies with emavusertib monotherapy have demonstrated a significant reduction in AML blasts with clinical and molecular responses, including patients with relapsed or refractory AML, previously treated with an HMA and/or FLT3 inhibitors (Metzeler 2022). Azacitidine + venetoclax (aza+ven) has been approved in newly diagnosed, unfit patients with AML. In the VIALE-A study, composite complete response (CRc) (CR, CRh, or CRi) in the absence of measurable residual disease (MRD) of &amp;lt;1 residual blast/1000 leukocytes (MRD negative [MRD−]) resulted in longer duration of response (DOR), event-free survival, and overall survival (OS), and better HSCT outcome compared with patients who achieved CRc but were MRD+ (Pratz, 2022). In pre-clinical studies, emavusertib in combination with aza+ven demonstrated synergistic antileukemic effects in AML cell lines, including azacitidine- or venetoclax-resistant cell lines. Adding emavusertib to aza+ven in MRD+ patients at the time of CR may convert MRD status without adding significant toxicity and confirm that emavusertib can be safely added to aza+ven as a potential new regimen in front-line therapy. Study Design: This is a single-arm, open-label Phase 1b trial evaluating safety and tolerability, PK, and conversion of MRD status with emavusertib as an add-on agent to aza+ven in AML patients who achieved CR or CRh with MRD+ based on local testing (EU CT Number 2023-505828-58-00). The primary objective of the study is to determine a safe and tolerable dosing schedule for the triple combination. Secondary objectives include MRD conversion rate, DOR, OS, and pharmacokinetics. The study will enroll approximately 24 patients at 5 to 10 sites globally. Patients will have received azacitidine and venetoclax as first line therapy and achieved CR or CRh after 1-6 cycles of aza/ven. If MRD status remains positive, emavusertib will be added to the existing well tolerated aza+ven regimen. The starting emavusertib dose is 200 mg BID for 7 days per cycle of 28 days. If well tolerated, duration of emavusertib treatment will be extended to 14 and 21, respectively; no intra-patient change of emavusertib dosing duration is planned. The patients will continue triple treatment (emavusertib+aza+ven) until consent withdrawal, disease progression, intolerable toxicity, or not achieving MRD- within 6 cycles of triple treatment. In this Phase 1b trial, MRD can be evaluated by local testing of bone marrow. Key exclusion criteria include residual toxicities and significant comorbidities. Citation Format: Reinhard von Roemeling, Adolfo De La Fuente, Claudio Cerchione, Sebastian Scholl, Jan Moritz Middeke, Gaurav S. Choudhary, Maria Lamar, Steven Angelides, Uwe Platzbecker. Trial in progress: A phase 1b single-arm, open-label, study of emavusertib (CA-4948) in combination with azacitidine and venetoclax in acute myeloid leukemia patients in complete response with measurable residual disease [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr CT150.

Abstract ND05: The discovery of ARV-393, a potent, orally bioavailable BCL6 targeting PROTAC® for the treatment of Non-Hodgkin’s Lymphoma

Abstract Discovery of ARV-393, a potent, orally bioavailable BCL6 targeting PROTAC® for the treatment of Non-Hodgkin’s Lymphoma (NHL)Dan Sherman, Sheryl M. Gough, Lynn DeCarr, Sarah Eaton, Mark Bookbinder, Jennifer Pizzano, Elizabeth Bortolon, John Corradi, Rashaun Wilson, Daniel Rogoz, Ram Lingamaneni, Wei Zhang, Michelle Zhang, Xin Chen, Gan Wang, Hanqing Dong, Michael Berlin, Keith R. Hornberger, Lawrence Snyder, Achal Pashine and Ian Taylor. Arvinas, Inc., 5 Science Park, New Haven, CT, USA. Approximately 18,000 cases of Diffuse large B-cell lymphomas (DLBCL) are diagnosed worldwide per year making this cancer the most prevalent (30%) of the non-Hodgkin’s Lymphomas (NHL). Despite the success of R-CHOP treatment, approximately 40% of patients are refractory or relapse. While much progress has been made with CAR-Ts and bi-specific antibodies following frontline therapy in recent years, there remains a need for an orally bioavailable small-molecule that targets molecular drivers of NHL. The BCL6 transcription factor has long been known as an oncogenic driver of B-cell malignancy. The BCL6 gene has been found to be translocated and/or mutated resulting in deregulation of its expression, predominantly in DLBCL and Burkitt’s lymphoma (BL). The deregulated expression and scaffolding role of BCL6 in the transcriptional repressor complex make it an ideal target for the PROteolysis Targeting Chimera (PROTAC®) technology with one BCL6 degrader recently entering Phase 1 trials. We undertook a medicinal chemistry campaign to identify a BCL6-targeting PROTAC®. This effort identified ARV-393, an orally bioavailable PROTAC® that recruits BCL6 and the E3 ligase cereblon to rapidly degrade BCL6 via the cell’s natural ubiquitin proteasome system. ARV-393 is potent, demonstrating DC50 and GI50 values &amp;lt;1 nM in numerous DLBCL and BL cell lines. This agent demonstrates deep BCL6 degradation in vitro and in vivo, resulting in excellent TGI in several tumor xenograft models supporting a first-in-human trial in 1H 2024. We will present the chemical structure of ARV-393 and selected pre-clinical data. Citation Format: Dan Sherman. The discovery of ARV-393, a potent, orally bioavailable BCL6 targeting PROTAC® for the treatment of Non-Hodgkin’s Lymphoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr ND05.

Abstract LB265: IpY.20: Innovative strategies for post-CDK estrogen receptor (ER)+ metastatic breast cancer (mBC)

Abstract Cyclin-dependent kinases (CDK) 4/6 are key cell cycle regulators that form complexes with cyclin D1 and the master regulator p27Kip1. This ternary complex acts downstream of the ER- and HER2-pathways, which drive cell proliferation. CDK4/6 phosphorylates the Retinoblastoma protein and other substrates, and keeps p27 from inhibiting G1-associated CDK2. Targeted inhibition of CDK4/6 (CDK4/6i) blocks the growth of ER+ and HER2+ BC by dissolving the CDK4/6-cyclin D1 complex and permitting the shuttling of p27 to inhibit CDK2 complex. Approval of CDK 4/6i such as palbociclib, though a game changer for ER+ mBC, resulted in tumor resistance, leaving patients without effective treatments and a 5-yr survival of only 30%. Although CDK2 inhibitors (CDK2i) address compensatory CDK2 activity bypassing CDK4/6i, a key resistance mechanism, they lack selectivity due to CDK homology, resulting in off-target toxicity. To inhibit CDK2/4/6 simultaneously, combinations of CDK4/6i and CDK2i monotherapies were attempted, but the lack of coordination between CDK4/6 and CDK2 inhibition resulted in suboptimal efficacy. Concarlo presents a unique therapeutic rationale for directly targeting the CDK master regulator p27 to simultaneously inhibit CDK2/4/6 in a concerted manner, one that is guided by the role of p27 to turn all of the G1 CDKs ON and OFF during periods of proliferation and quiescence, respectively. This transition is facilitated by BRK (Breast tumor kinase)-mediated phosphorylation of p27. When p27 is Y phosphorylated, it converts CDK4/6 and CDK2 into open, active complexes. An endogenous BRK-spliced variant ALT can competitively bind to p27, block Y phosphorylation and lock CDK2/4/6 in the OFF conformation. Concarlo engineered a shorter variant of ALT (CCL20) and packaged in cationic liposomes for intracellular delivery, creating a novel IpY.20 drug product. As a single agent, IpY.20 inhibits cell proliferation in treatment-naïve and CDK4i-resistant HR+ cells with reduced non-tumor cell activity. In combination, IpY.20 enhances CDK4/6i responses in treatment-naïve HR+ cells, making it a potential front-line mBC therapy. While other CDKi activity is limited to cytostasis, IpY.20 shows dual cytostasis-cytotoxicity, potentially a more durable option. IpY.20 does not cause neutropenia commonly seen with other CDKis, and rescues the CDK4/6i-induced neutropenia in mice, suggesting better clinical tolerability. These findings underscore the significance of coordinated targeting of CDK2/4/6, making IpY.20 a first-in-class product uniquely exploiting p27-mediated CDK2/4/6 regulation. Direct targeting of p27 presents a new treatment paradigm bypassing the challenges of ATP-competitive CDKis, with potential to expand into tumor types with aberrant p27, CDK2/4/6 activity, or RAS/MAPK pathways that increase CDK4/6 activity. Citation Format: Grace Chen, Natalie Dudas, Kate Coleman, Carolina Guido, Natalia Zisman, Krishna Allamneni, Stacy Wister Blain. IpY.20: Innovative strategies for post-CDK estrogen receptor (ER)+ metastatic breast cancer (mBC) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr LB265.

Metastatic patterns and hormone receptor status among breast cancer patients in Tanzania

Introduction: Metastatic breast cancer is a common presentation in Tanzania. Estrogen-receptor (ER)-positive tumors are known to metastasize to the bones and require hormonal treatment as first-line therapy. Challenges with accessing immunohistochemistry services can delay information on breast cancer subtypes, further delaying treatment with effective hormonal therapy. Objectives: This study aimed to assess the pattern of distribution of metastatic lesions in patients with metastatic breast cancer and evaluate its association with their hormone and HER-2 status, which could help provide recommendations on the use of front-line hormone therapy in areas where access to immunohistochemistry is a challenge. Methods: A retrospective study covering histologically confirmed breast cancer patients in 2020 with metastatic lesions and complete medical records at Ocean Road Cancer Institute. Clinical information on the number, state and sites of metastasis, presence of symptoms and treatment received, and pathological variables, including histology, ER, PR and HER-2 status, were documented. Results: Forty-nine (96.1%) of 51 patients analysed were female, with a mean age of 49.5 years. 47% presented with up-front metastatic disease. Lung was the most common metastatic site (76.5%) followed by bone/spine (53%). About half the patients had multiple sites involved. ER-positive tumors accounted for 47%, PR positive for 31% and HER-2 positive 39.2%. ER-positive tumors were more likely to present as a recurrence than up-front metastasis. ER-positive tumors were significantly more likely to be associated with bone and spine metastasis (59%) compared to ER-negative tumors (29%) Conclusion: The clinical and pathological features of MBC in Tanzanian women are similar in many ways to those in other African regions. However, the ER positivity rate is lower. This study found a significant association between ER-positive tumours and skeletal metastasis, which has implications for the up-front treatment of these patients, especially where access to immunohistochemistry can be a challenge.

Exploring the anti-inflammatory activity of the plant-derived phytochemical sulforaphane from cruciferous vegetables

Dysregulation of immune responses results in the development of chronic inflammatory conditions. The current frontline therapy, glucocorticoids, are effective immunosuppressive drugs but come with a trade-off of cumulative, debilitating side effects with sustained use. Clearly, alternative drug options with improved safety profiles are urgently needed. Macrophage Migration Inhibitory Factor (MIF) is a pleotropic pro-inflammatory cytokine and integral component of immune and inflammatory responses. MIF counter-regulates the immunosuppressive effects of glucocorticoids and promotes NLRP3 inflammasome activation.1, 2 Elevated MIF is a feature of multiple diseases, including multiple sclerosis, rheumatoid arthritis, and systemic lupus erythematous. Given the association of increased MIF in serum with multiple disease models, it is considered MIF may be a plausible, specific druggable target in treatment of chronic inflammatory and autoimmune diseases, particularly as a target for glucocorticoid-sparing therapy to reduce the dose or duration of glucocorticoid treatment. The organosulfur isothiocyanate phytochemical sulforaphane (SFN) is extracted from cruciferous vegetables, including broccoli and Brussel sprouts following hydrolysis of its inactive precursor, glucoraphanin. SFN has antioxidant and cancer chemoprotective properties, and promotes NRF2 antioxidant signalling to upregulate the expression of numerous antioxidant enzymes. SFN has been shown to covalently modify MIF with high reactivity and is a potent inhibitor of MIF tautomerase activity. However, to date, no such study has evaluated the role of SFN as a novel inhibitor of MIF-mediated inflammatory pathway activation. Using cell-based assays, we have sought to investigate the role of SFN as an inhibitor of multiple inflammatory pathways which have previously implicated MIF as a possible regulator. Our initial work has examined SFN as an inhibitor of NF-κB activity, inflammasome activation, and evaluated if MIF is required for this effect. RAW264.7 murine macrophage cells stably expressing NF-κB-luciferase reporter construct were pre-treated with SFN (2.5 µM) before the induction of inflammation, via LPS (100ng/mL). For NLRP3 inflammasome activation, cells were subsequently treated with the NLRP3-specific inflammasome activator, nigericin (10 µM). TNF, IFN-β and IL-1β cytokine expression was measured by ELISA and NF-κB activity by luciferase reporter assay. We found SFN is a potent inhibitor of NF-κB activity and inhibits release of the pro-inflammatory cytokine IL-1β through inhibition of NLRP3 inflammasome activation. Finally, co-incubation of SFN with the glucocorticoid dexamethasone significantly suppressed TNF and IFN-β expression, demonstrating steroid sparing activity of SFN in vitro. Thus, SFN may be a suitable treatment for disruption of inflammatory pathways and suggest some of these effects may be mediated through direct interactions with MIF.

Primary analysis of a prospective cohort study of Japanese patients with plasma cell neoplasms in the novel drug era (2016–2021)

The emergence of novel drugs has significantly improved outcomes of patients with plasma cell neoplasms (PCN). The Japanese Society of Hematology conducted a prospective observational study in newly diagnosed PCN patients between 2016 and 2021. The analysis focused on 1385 patients diagnosed with symptomatic PCN between 2016 and 2018. The primary endpoint was the 3-year overall survival (OS) rate among patients requiring treatment (n = 1284), which was 70.0% (95%CI 67.4–72.6%). Approximately 94% of these patients received novel drugs as frontline therapy. The 3-year OS rate was 90.3% (95%CI 86.6–93.1%) in the 25% of patients who received upfront autologous stem cell transplantation (ASCT), versus just 61.4% (95%CI 58.0–64.6%) in those who did not receive upfront ASCT. The only unfavorable prognostic factor that affected OS in ASCT recipients was an age of 65 or higher. For patients who did not receive ASCT, independent unfavorable prognostic factors included frontline treatment with conventional chemotherapies, international staging system score of 2/3, extramedullary tumors, and Freiberg comorbidity index of 2/3. This study unequivocally demonstrates that use of novel drugs improved OS in Japanese myeloma patients, and underscores the continued importance of upfront ASCT as the standard of care in the era of novel drugs.

MicroRNA Expression Profiles in Human Samples and Cell Lines Revealed Nine miRNAs Associated with Cisplatin Resistance in High-Grade Serous Ovarian Cancer.

Metastasis and drug resistance are major contributors to cancer-related fatalities worldwide. In ovarian cancer (OC), a staggering 70% develop resistance to the front-line therapy, cisplatin. Despite proposed mechanisms, the molecular events driving cisplatin resistance remain unclear. Dysregulated microRNAs (miRNAs) play a role in OC initiation, progression, and chemoresistance, yet few studies have compared miRNA expression in OC samples and cell lines. This study aimed to identify key miRNAs involved in the cisplatin resistance of high-grade-serous-ovarian-cancer (HGSOC), the most common gynecological malignancy. MiRNA expression profiles were conducted on RNA isolated from formalin-fixed-paraffin-embedded human ovarian tumor samples and HGSOC cell lines. Nine miRNAs were identified in both sample types. Targeting these with oligonucleotide miRNA inhibitors (OMIs) reduced proliferation by more than 50% for miR-203a, miR-96-5p, miR-10a-5p, miR-141-3p, miR-200c-3p, miR-182-5p, miR-183-5p, and miR-1206. OMIs significantly reduced migration for miR-183-5p, miR-203a, miR-296-5p, and miR-1206. Molecular pathway analysis revealed that the nine miRNAs regulate pathways associated with proliferation, invasion, and chemoresistance through PTEN, ZEB1, FOXO1, and SNAI2. High expression of miR-1206, miR-10a-5p, miR-141-3p, and miR-96-5p correlated with poor prognosis in OC patients according to the KM plotter database. These nine miRNAs could be used as targets for therapy and as markers of cisplatin response.

Activity refinement of aryl amino acetamides that target the P. falciparum STAR-related lipid transfer 1 protein

Malaria is a devastating disease that causes significant morbidity worldwide. The development of new antimalarial chemotypes is urgently needed because of the emergence of resistance to frontline therapies. Independent phenotypic screening campaigns against the Plasmodium asexual parasite, including our own, identified the aryl amino acetamide hit scaffold. In a prior study, we identified the STAR-related lipid transfer protein (PfSTART1) as the molecular target of this antimalarial chemotype. In this study, we combined structural elements from the different aryl acetamide hit subtypes and explored the structure-activity relationship. It was shown that the inclusion of an endocyclic nitrogen, to generate the tool compound WJM-715, improved aqueous solubility and modestly improved metabolic stability in rat hepatocytes. Metabolic stability in human liver microsomes remains a challenge for future development of the aryl acetamide class, which was underscored by modest systemic exposure and a short half-life in mice. The optimized aryl acetamide analogs were cross resistant to parasites with mutations in PfSTART1, but not to other drug-resistant mutations, and showed potent binding to recombinant PfSTART1 by biophysical analysis, further supporting PfSTART1 as the likely molecular target. The optimized aryl acetamide analogue, WJM-715 will be a useful tool for further investigating the druggability of PfSTART1 across the lifecycle of the malaria parasite.

Abstract 2603: Targeting chemo-resistant ovarian cancer with a first-in-class, first-in-human immune-oncology agents containing granzyme B

Abstract Ovarian cancer (OC) is the fifth leading cause of cancer-related mortality in women. The current standard of care consists of debulking surgery with platinum-taxane maintenance chemotherapy. However, OC will recur in most patients, resulting in a five-year survival rate of 45%. In the past decades, there have been several developments in front-line maintenance therapy including bevacizumab or PARP inhibitors. While these therapies have shown effectiveness in prolonging progression free survival, this has not translated into improvements in overall survival. It is, therefore, essential to develop more effective maintenance therapies and most of the current efforts are focused on targeted approaches and immune therapeutics. Though immunotherapeutic strategies have induced durable responses in patients with melanoma, lung cancer, and other malignancies, the OC response to immunotherapy is limited as there is a significant subset of patients who do not respond. Our laboratory has developed several fully human granzyme B (GrB) based fusion proteins against key OC targets including folate receptor 1 (GrB-Fc-mov018) and fibroblast growth factor-inducible 14 (GrB-Fc-IT4) which retain high specificity of the targeting agent, combined with the GrB specific activity, a pro-apoptotic mechanism of action, and a robust in vivo efficacy. We assessed the in vitro cytotoxicity of GrB-based constructs against a panel of OC cell lines sensitive (OVCAR8, SKOV3, A2780, HeyA8) or resistant (SKOV3-TX, A2780/Cl-16, HeyA8-MDR) to common chemotherapeutic agents. SKOV3-TX cells were &amp;gt;10 fold more resistant to Paclitaxel than the parental SKOV3 cells while A2780/Cl-16 were 11-fold more resistant to Cisplatin than the parental A2780 cells. In contrast, none of the chemo-resistant cell lines showed resistance to the GrB-based constructs and the IC50 values observed were similar to those of the parental cell lines in the low nanomolar range (&amp;lt;50 nM). Moreover, target expression analysis did not show significant differences between parental and chemo-resistant cell lines. A pilot in vivo efficacy study of GrB-Fc-IT4 and GrB-Fc-mov018 against a subcutaneous, established ovarian tumor (OVCAR8) xenograft showed promising growth inhibition of established tumors compared to vehicle controls. In vivo studies evaluating the response to different treatments of mice bearing chemo-resistant ovarian tumors are ongoing. Our results suggest that the mechanism of resistance developed to conventionally used chemotherapeutic agents such as Paclitaxel, Doxorubicin, Cisplatin or Mitomycin do not confer resistance to GrB-based constructs. Hence, we speculate that GrB-based constructs could be an effective therapy in OC patients with immune-excluded tumors that have developed resistance to conventional treatment. Research conducted, in part, by the Clayton Foundation for Research. Citation Format: Ana Alvarez-Cienfuegos, Lawrence H. Cheung, Khalid A. Mohamedali, Michael G. Rosenblum. Targeting chemo-resistant ovarian cancer with a first-in-class, first-in-human immune-oncology agents containing granzyme B [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2603.

Abstract 1224: 3D models of chemotherapy- and PARPi-resistant ovarian cancer indicate essential roles for JAK/STAT signaling in mediating drug resistance

Abstract Ovarian cancer is the deadliest gynecological cancer with a low 5-year overall survival rate that affects over 300,000 women globally each year. Given lack of routine screening procedures, ovarian cancer patients are frequently diagnosed with late-stage disease that rapidly progress despite initial responses to front line therapy. PARPi and VEGFi targeted therapies have improved progression free survival in small subsets of patients but have largely failed to improve overall survival. Since the robust uptake of PARPis in the front line setting, resistance to this class of drugs is a growing problem. The literature is filled with many novel treatment approaches, but the vast majority fail to gain traction in pre-clinical models and early phase trials. A contributing factor to these disappointments relates to the prevalent use of 2D monoculture model systems that do not recapitulate the tumor microenvironment. To address this issue, we utilized the Rastrum 3D cell printer to grow ovarian cancer cells and PDX models in bio-functional matrices which provide optimal stiffness and extracellular matrix components specific to the ovarian tumor microenvironment. We found that ovarian cancer cells grown under these conditions exhibit dramatic up-regulation of the JAK/STAT signaling pathway, including autocrine/paracrine signaling factors, which correlated with increased sensitivity to JAK/STAT inhibitors. This affect was lost when STAT1 and STAT3 knockout cell lines were grown in this 3D environment. Ovarian tumors are known to be rich in cancer-associated fibroblasts (CAFs) and tumor-associated macrophages (TAMs). We incorporated primary CAFs into this 3D culture system and found they could promote ovarian cancer cell growth only in cancer cells with intact JAK/STAT signaling further indicating the essential role of this pathway in mediating tumor progression. Co-culture with M2 macrophages was also found to induce ovarian cancer cell growth, particularly in resistant models. Conversely, co-culture with M1 macrophages inhibited treatment naïve ovarian cancer cell growth but not resistant cell line growth. Single-cell RNAseq of the complex 3D cultures elucidated profound differences in the cross-talk between these cell types that is dependent on cancer cell sensitivity to standard-of-care agents. Finally, the addition of JAK/STAT inhibitors was found to substantially alter this cross-talk between cell types and inhibit cancer cell viability. These data further implicate the importance of JAK/STAT signaling, specifically in clinically relevant 3D models, in supporting ovarian cancer progression and response to chemotherapy and PARPi treatment. Ongoing studies are aimed at confirming these findings in pre-clinical mouse models and to elucidate the most effective JAK/STAT inhibitors in vivo with the goal of informing the design of future clinical trials. Citation Format: Esther Rodman, Xiyin Wang, Hannah Smith, Xiaonan Hou, Scott Kaufmann, John Weroha, John Hawse. 3D models of chemotherapy- and PARPi-resistant ovarian cancer indicate essential roles for JAK/STAT signaling in mediating drug resistance [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1224.

Abstract 980: Plasma tumor fraction is an independent prognostic marker of response to front line chemotherapy in high-grade serous epithelial ovarian cancer: The MITO-16a/MANGO-OV2a/clinical trial experience

Abstract Background. Although 80% of high grade serous ovarian cancer (HGSOC) patients are initially responsive to platinum (Pt)-based chemotherapy, the majority of them experience relapse with a progressive Pt-resistant disease. One of the most challenging issue that hampers the possibility to effectively treat relapsed disease is the lack of biological information about tumor recurrence. To date, the Pt-free interval (PFI), an empirical measure of the time lagging between the end of front-line chemotherapy and relapse, is the only and widely accepted parameter to predict patient outcome and sensitivity to Pt second-line chemotherapy. We have previously demonstrated that analysis of circulating tumor DNA (ctDNA) by low pass whole genome sequencing (sWGS) is a suitable tool to predict patient outcome and to intercept early signs of relapsed disease (Paracchini et al. PMID:33323403). In the present study, we quantified the percentage of tumor fraction (TF) in plasma of patients enrolled within the frame of a phase III clinical trial (MITO-16A/MaNGO-OV2A-EUDRACT number: NCT01706120) to demonstrate, at baseline, the prognostic value of untargeted ctDNA analysis. Methods. 172 eligible patients enrolled with the frame of the MITO-16A/MaNGO-OV2A clinical trial, for whom plasma sample was collected at chemotherapy before chemotherapy, were selected for the study. For each plasma sample, circulating-free DNA (cfDNA) was purified and whole genome libraries (HyperPlus, Roche) sequenced (mean coverage 0.5X). ichorCN algorithm was used to infer the percentage of TF, as previously published (Paracchini et al. PMID:33323403). Results. In 168 out of 172 plasma samples analyzed, the TF was detectable and it ranged from 2.4% to 47%. Cox-model univariate analysis with patients’ overall survival (OS) and Progression-Free Survival (PFS), indicates association of TF levels with both OS and PFS (p&amp;lt;0.001). The prognostic relevance of TF was also confirmed in multivariate analysis, where, considering CA-125, residual tumor, stage of disease, histology and age as co-variables, TF maintained its statistical significance in PFS (HR = 2.1, CI 95%, p-value &amp;lt; 0.003). Conclusion. Retrospective analysis of baseline plasma samples collected within the frame of the MITO-16A/MaNGO-OV2A clinical trial, demonstrated that the percentage of TF is an independent prognostic marker of relapse. This finding confirms the importance of liquid biopsy analysis based on untargeted sWGS tool as an innovative approach to predict response to front line therapy and patient’s outcome Citation Format: Sergio Marchini, Lara Paracchini, Laura Arenare, Giovanni Scambia, Carmela Pisano, Riccardo Zadro, Laura Mannarino, Annamaria Ferrero, Paolo Chiodini, Daniela Califano, Sandro Pignata, Maurizio D'Incalci. Plasma tumor fraction is an independent prognostic marker of response to front line chemotherapy in high-grade serous epithelial ovarian cancer: The MITO-16a/MANGO-OV2a/clinical trial experience [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 980.

Abstract 6528: Integrin ɑvβ6 upregulation as a mechanism of T-cell evasion in head and neck squamous cell carcinoma

Abstract Head and neck squamous cell carcinoma (HNSCC) encompasses malignancies of the mucosal epithelium in the oral cavity, pharynx, and larynx. The lack of effective screening strategies and the typically late stage of detection are contributors to a considerable annual death toll of HNSCC. Additionally, the anatomical proximity of the malignancy to delicate structures of the head and neck leads to tremendous treatment-related morbidity. Therefore, there is great interest in developing life-saving therapies and strategies for treatment de-escalation. The immune checkpoint inhibitor pembrolizumab (αPD-1) has been approved for recurrent or metastatic HNSCC and as a frontline therapy for unresectable disease. However, only about a quarter of patients respond to αPD-1 therapy. The immunosuppressive effect of TGFβ has been widely described as relevant to the HNSCC tumor microenvironment. However, attempts to blockade TGFβ have failed mainly due to the widespread side effects of disrupting a highly promiscuous cytokine. Integrin αvβ6 is a major activator of the inert latent TGFβ into the active, immunosuppressive form. With its high relative specificity to HNSCC tissue, inhibition of αvβ6 could offer a safer approach for disrupting TGFβ to overcome resistance to immune checkpoint blockade. After screening ɑvβ6 expression levels of HNSCC cell lines via flow cytometry, cell lines FaDu and CAL27 were selected for further investigation due to high endogenous ITGB6 expression (FaDu 35.57% cells ITGB6+, CAL27 95.69% cells ITGB6+). The cell lines were transduced with a doxycycline-inducible short hairpin RNA (shRNA) knockdown of αvβ6 using a lentiviral system. Both knockdown and control shRNA cell lines were pretreated with 1 μg/mL of doxycycline for five days to induce the shRNA and subsequently co-cultured with TALL-104 T-cells. Quantitative fluorescence microscopy of the co-culture revealed that the knockdown of αvβ6 substantially increased T-cell killing over 24hrs (FaDu CTRL shRNA 6.72%±2.49 dead vs. FaDu ITGB6 shRNA 12.80%±3.16 dead, p&amp;lt;0.001). However, treatment of FaDu and CAL27 cell lines with active-TGFβ showed no change in PD-L1 expression via flow cytometric analysis. To determine whether the T cell evasive effect of αvβ6 is driven by other immune checkpoints on the cancer cells or by the direct effect that TGFβ has on immune cells, we show the generation of relevant mouse αvβ6 shRNA knockdown cells. These syngeneic in vivo studies will facilitate cytokine profiling to uncover the dynamics of tumor-immune cell interactions in response to αvβ6 inhibition. Citation Format: William J. MacDonald, Praveen R. Srinivasan, Maximilian Pinho-Schwermann, Shengliang Zhang, Vida Tajiknia, Connor Purcell, Jillian Strandberg, Nolan Stubbs, Wafik S. El-Deiry. Integrin ɑvβ6 upregulation as a mechanism of T-cell evasion in head and neck squamous cell carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6528.

Abstract 1902: ADRX-0706 Nectin-4 antibody-drug conjugate PK/PD characterization elucidates its widened therapeutic window

Abstract Nectin-4 is a well validated tumor target, which is highly expressed in several solid cancers, while expression in normal tissues is limited. A first-generation antibody-drug conjugate targeting Nectin-4, called enfortumab vedotin-ejfv (EV), was granted accelerated FDA approval in 2019 for urothelial cancers, and is currently approved for frontline therapy in cisplatin-ineligible patients with locally advanced or metastatic urothelial carcinoma, providing groundbreaking improvement in patient survival. However, clinical use of EV has also revealed safety-driven limitations, which result in reduced and/or interrupted drug exposures impacting efficacy. To overcome these limitations in therapeutic window, Adcentrx has developed ADRX-0706, a Nectin-4-targeting next-generation ADC with a drug-antibody ratio (DAR) of 8. ADRX-0706 utilizes a novel tubulin inhibitor payload AP052 with a proprietary cleavable linker utilizing Adcentrx’ proprietary i-ConjugationTM technology, which results in excellent biophysical features. Most noteworthy, ADRX-0706 displays a very stable PK profile with overlapping curves for total antibody and ADC as well as full DAR retention in circulation as determined by mass spectrometry. This translates to superior efficacy of ADRX-0706 over EV in multiple in vivo cancer cell line- and patient-derived xenograft mouse models across indications. Detailed PK/PD characterization of ADRX-0706 validates the mechanism of action as an anti-mitotic agent inducing cell cycle arrest and apoptosis. In addition, ADRX-0706 treatment leads to increased PD-L1 expression in mouse pharmacology models, which is a consequence of immunogenic cell death as described for this payload class. These findings are in line with emerging data on EV and provide rationale for combination regimens with checkpoint inhibitors. Besides the improvement in efficacy, ADRX-0706 was also designed for superior safety. A payload distribution study in tumor-bearing mice reveals a preferential and increased delivery of payload to tumors and lower payload delivery to normal tissues as well as lower free payload levels in plasma for ADRX-0706 compared to EV. Taken together, these data provide association of the improved drug-linker stability of ADRX-0706 to an improved Nectin-4 directed delivery of AP052 payload to the tumor and lower exposure in normal tissues, which may translate to an improved therapeutic window. In summary, the preclinical efficacy and safety properties of ADRX-0706 support clinical evaluation of this next generation anti-Nectin-4 ADC. ADRX-0706 is currently in a phase 1a/b study (NCT06036121). Citation Format: Maria Shahmoradgoli, Andrew Hau, Dong Jun Lee, Anna Wang, Peter P. Challita, Oscar Betancourt, Wes Sisson, Mario M. Kuo, Kris Zhang, Albert Goldson, Sam Janssen, Paul Datta, Felipe Acosta, Alexander Chu-Kung, Hui Li, Pia M. Challita-Eid, Sabine Rottmann. ADRX-0706 Nectin-4 antibody-drug conjugate PK/PD characterization elucidates its widened therapeutic window [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1902.

Abstract 2989: MicroRNA profiling in human samples and cell lines uncovers eight key players in the cisplain resistance of HGSOC

Abstract Metastasis and drug resistance remain significant contributors to cancer-related mortality globally. In ovarian cancer, a substantial 70% of cases develop resistance to the front-line therapy, cisplatin. Despite numerous proposed mechanisms for cisplatin resistance, the complete molecular events leading to this phenomenon in ovarian cancer remain incompletely understood. Mounting evidence suggests that dysregulation of microRNAs (miRNAs) plays a pivotal role in carcinogenesis, including the development of drug resistance. While various miRNAs have been identified in ovarian cancer samples and cell lines, few studies have compared miRNA expression in human paraffin ovarian samples and cisplatin-resistant high-grade serous ovarian cancer (HGSOC), the most prevalent and malignant of gynecological malignancies. This study aimed to identify key miRNAs implicated in cisplatin resistance. We performed miRNA expression profiles in RNA isolated from human paraffin ovarian tumors and ovarian cancers cell lines. Eight miRNAs were commonly increased in paraffin samples and cisplatin resistant ovarian cancer cells. Targeting these miRNAs with inhibitors significantly reduced cell proliferation by more than 50% for miR-203a, miR-96-5p, miR-10a-5p, miR-141-3p, miR-200c-3p, and miR-182-5p, and to a lesser extent, miR-296-5p and miR-1206. Inhibitors demonstrated a reduction in cell migration for all targets except miR-200c-3p and miR-10a-5p. Analysis of online databases, literature reports, and molecular pathway construction revealed that these eight miRNAs regulate key molecular pathways associated with cell proliferation, primarily through PTEN regulation in cisplatin-resistant HGSOC cells. Interrogation of the KM plotter patient database revealed that high expression of miR-1206, miR-10a, miR-141, and miR-96 correlates with a poor prognosis in ovarian cancer patients. These findings position these eight miRNAs as potential therapeutic targets and markers for cisplatin response in ovarian cancer therapy. Citation Format: Mariela Rivera-Serrano, Marienid Flores, Jose Rolon, Victor Reyes, Fatma Valiyeva, Pablo E. Vivas-Mejia. MicroRNA profiling in human samples and cell lines uncovers eight key players in the cisplain resistance of HGSOC [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2989.

Abstract 3357: Identifying mechanisms of acquired resistance to lorlatinib utilizing a genome-wide CRISPR-Cas9 screen

Abstract Survival rates for neuroblastoma (NB), a predominantly pediatric solid tumor arising from the sympathoadrenal neural crest, have improved incrementally from 25% to 50% over three decades with dramatic escalation in therapy intensity. Gain-of-function mutations in anaplastic lymphoma kinase (ALK), of which 85% occur at residues F1174, F1245, and R1275, confer inferior survival compared to patients with wild-type ALK. Lorlatinib, a third generation ALK inhibitor, has completed Phase 1 testing in the NANT Consortium and has moved to frontline therapy in the Children’s Oncology Group. The robust and sustained activity observed with minimal toxicity is transient in relapse patients harboring MYCN amplification and ALK activation. We aim to elucidate and target mechanisms of acquired resistance that emerge from lorlatinib treatment. We utilized the Brunello library, a genome-wide CRISPR-CAS9 loss of function screen targeting 19,114 genes (4 sgRNA per gene), which allows for a high confidence of detection of hits. We screened four clinically representative cell lines: Kelly (ALKF1174L, MYCN-amplified, p53P117T), SMS-SAN (ALKF1174L, MYCN-amplified), LAN5 (ALKR1275Q, MYCN-amplified), and SY5Y (ALKF1174L, MYCN-nonamplified). sgRNAs were ranked according to the degree of depletion or enrichment. We validated top depleted targets through cell-based assays and immunoblotting. We identified several actionable targets across multiple NB cell lines that, when depleted, increase the efficacy of lorlatinib, including FGFR2, BCL2L1, SOX11, SMARCA2, and SMARCD2. Genetic knockout of FGFR2 led to a 40% reduction (p&amp;lt;0.05) in KO cells upon lorlatinib treatment compared to control. PROTAC degradation of the anti-apoptotic BCL-xL (BCL2L1) revealed the combination of lorlatinib and the PROTAC led to a decrease in IC50 in vitro. Additionally, we identified conserved core components of the SWI/SNF complex, a subfamily of ATP-dependent chromatin remodelers, as well as SOX11, a regulator of the SWI/SNF complex and transcription factor of the core regulatory circuitry in adrenergic high-risk NB. In conclusion, we identified actionable targets across four NB cell lines that, when depleted, increase the efficacy of lorlatinib. Depletion of FGFR2 led to increased sensitivity to lorlatinib, however enzymatic inhibition showed minimal effect. Future investigation into dual targeting of ALK and FGFR2 through novel alternative methods is warranted. Furthermore, we observed a synergistic relationship between lorlatinib and a BCL-xL PROTAC in vitro. Ongoing in vivo studies will test the combinatorial efficacy in lorlatinib-naïve and resistant models. Finally, we are investigating epigenetic remodeling by the SWI/SNF complex and its regulators in NB cells during lorlatinib treatment through targeted genetic manipulation of SOX11 to understand its role as a master transcriptional regulator of MYCN and FGFR2. Citation Format: Joshua Renn Kalna, Smita Matkar, Emily O'Drisoll, Skye Balyasny, Matteo Calafatti, Mark Gerelus, Dave Groff, Tina Acholla, Colleen E. Casey, Paul Kamitsuka, Grant Li, Steven J. Pastor, Gabriela Witek, Kateryna Krytska, Jarrett Lindsay, Ophir Shalem, Yael P. Mossé. Identifying mechanisms of acquired resistance to lorlatinib utilizing a genome-wide CRISPR-Cas9 screen [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3357.

Abstract 6646: Investigating the combination of radiation and subsequent immune checkpoint inhibitor treatment in head and neck squamous cell carcinoma models

Abstract Purpose: Head and neck squamous cell carcinoma (HNSCC) is often marked by an immunosuppressive tumor microenvironment, which contributes to the dismal 10-20% response rate to immune checkpoint inhibitor (ICI) therapy in HNSCC patients. Radiotherapy (RT) is a currently standard of care and frontline therapy for HNSCC, yet resistance is common. We sought to examine the combination therapy of RT followed by ICI therapy to test if RT induces an in situ vaccination which enhances the efficacy of subsequent ICI. Methods: We utilized SCC cell lines derived from K15.KrasG12D/Smad4−/− SCCs, which mimic the progression of HPV-unrelated HNSCC, and transplanted SCC cells into immune-competent C57BL/6J mouse recipients. Mice were subjected to RT followed by anti-PD-L1/anti-TGFb therapy. CD8+ splenic T cells of responder or non-responder mice were examined by paired single-cell VDJ sequencing and single cell RNA sequencing (TCR/sc-RNAseq) to look for adaptations of the cytotoxic T cell compartment following combination therapy. Responder and non-responder tumor lines or tumors were treated with RT alone in vitro and in vivo, respectively, to examine major histocompatibility complex I (MHC-I) levels on tumor cells. Results: Responders to this combination therapy exhibited complete tumor eradication while non-responders displayed rapid tumor progression. When re-challenged with same HNSCCs cells, responders rejected implanted tumor cells while naïve recipients rapidly developed HNSCCs. Single-cell TCR sequencing of splenic CD8+ T cells revealed that responders, but not naïve recipients exhibited multiclonal CD8+ T cell expansion specifically of memory cell populations. Responder tumor cells exhibited greater levels of MHC-I protein level presentation than non-responders when stimulated with RT. Conclusions: Our data suggest that 1) elevated MHC-I by SCC tumor cells presentation driven by RT and ICI combination therapy facilitate a systemic expansion of memory CD8+ T cell clonotypes which drive anti-tumor immunity and 2) MHC-I expression at baseline or when induced by RT may serve as a predictive marker for therapeutic response to RT and ICI combination therapy in HNSCCs. Citation Format: Hanne Lind, Alexander Strait, Spencer Hall, Jack B. Goon, John D. Aleman, Samantha Chen, Philip Owens, Jing H. Wang, Christian Young, Xiao-Jing Wang. Investigating the combination of radiation and subsequent immune checkpoint inhibitor treatment in head and neck squamous cell carcinoma models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6646.

Abstract 3724: Targeting the LIFR-LCN2 pathway to sensitize liver cancer to immunotherapy

Abstract Liver cancer, primarily hepatocellular carcinoma (HCC), is highly lethal with limited treatment options and no biomarker to predict therapy response. The current frontline therapies for liver cancer, including sorafenib and the combination of atezolizumab (anti-PD-L1) and bevacizumab (anti-VEGF), have limited therapeutic benefits, which could be attributed, at least in part, to the highly immunosuppressive tumor microenvironment in liver cancer. Leukemia inhibitory factor receptor (LIFR) is frequently downregulated in HCC. My recent studies revealed that in oncogene-induced liver tumors, overexpression of LIFR increased, while knockout of Lifr decreased CD8+ T cell infiltration, which may be mediated by LCN2-dependent inhibition of T cell viability, proliferation, and effector function. In ongoing and future work, I will investigate whether LIFR or therapeutic LCN2 neutralization can sensitize HCC to immunotherapy. If successful, this project will illuminate how to improve liver cancer immunotherapy by targeting the LIFR-LCN2 pathway. Low LIFR expression and high LCN2 expression may be used to select HCC patients who will likely benefit from the combination therapy with the LCN2-neutralizing antibody plus immune checkpoint inhibitors. Citation Format: Yalan Deng, Li Ma. Targeting the LIFR-LCN2 pathway to sensitize liver cancer to immunotherapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3724.

Abstract 1229: BDTX-1535: A MasterKey EGFR inhibitor targeting classical and non-classical oncogenic driver mutations and the C797S acquired resistance mutation to address the evolving molecular landscape of EGFR mutant NSCLC

Abstract The molecular landscape of EGFR mutated NSCLC has evolved over time in response to changing treatment practices with EGFR inhibitors and through the expanding use of NGS. With the replacement of first-generation reversible EGFR tyrosine kinase inhibitors (TKIs) by the third generation covalent TKI osimertinib as front-line therapy for patients with NSCLC expressing classical EGFR mutations, acquired resistance mutations have shifted with the near disappearance of EGFR-T790M and the emergence and growing incidence of EGFR-C797S. Our understanding of the EGFR mutation landscape has also continued to mature with comprehensive sequencing across all EGFR exons and with the vast majority of patients now undergoing sequencing. We now see how classical oncogenic drivers represent only a subset of oncogenic EGFR driver mutations and where other non-classical driver mutations are numerous and represent a major unmet medical need. Furthermore, there is a growing appreciation of the differences between the classical EGFR-L858R and EGFR-Ex19 deletion (Ex19del) mutations. For patients expressing L858R, many co-express non-classical drivers and this may explain the weaker relative activity for osimertinib in patients expressing L858R versus Ex19del. For patients expressing Ex19del, the co-expression of non-classical mutations is less common. In contrast, patients with Ex19del more often gain C797S as an acquired resistance mutation. Using the Foundation Medicine’s FoundationInsights™ web-based platform, we present real world evidence (RWE) to define the molecular landscape of classical, non-classical, and acquired resistance mutations from a survey of &amp;gt;80,000 sequenced cases of NSCLC, including &amp;gt;12000 EGFR altered cases. We further present the profile for BDTX-1535 as a MasterKey EGFR inhibitor designed to address this evolved EGFR mutational landscape and tested against over &amp;gt;50 EGFR mutations. We also show how BDTX-1535 can address classical EGFR mutations in addition to on target mechanisms of resistance post osimertinib with potency against C797S as well as non-classical mutations affecting both the intracellular and extracellular domains, including L718X, E709X, S784F, V834L and A289V. Citation Format: Etienne Dardenne, Matthew O'Connor, Monique Nilsson, Junqin He, Xiaoxing Yu, John V. Heymach, Xiuning Le, Elizabeth Buck. BDTX-1535: A MasterKey EGFR inhibitor targeting classical and non-classical oncogenic driver mutations and the C797S acquired resistance mutation to address the evolving molecular landscape of EGFR mutant NSCLC [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1229.