Mansfield, Aaron S.

e15024 Background: Anetumab ravtansine (AR) is an antibody-drug conjugate (ADC) containing the microtubule inhibitor DM4. ADC drugs have high interpatient variability in pharmacokinetics and pharmacodynamics (PK/PD), which raises concerns whether current dosing based on body weight (mg/kg) is optimal. Thus, we evaluated the effects of patient characteristics, including novel biomarkers of the innate immune system (IIS), on the PK/PD of AR. Methods: Studies were performed in patients in three clinical trials of different cancers with AR as part of treatment: 1) platinum-resistant or refractory high-grade ovarian cancer treated with AR at 2.2mg/kg IV weekly plus bevacizumab(N = 19); 2) pleural mesothelioma treated with AR at 6.5 mg/kg IV every 3 weeks plus pembrolizumab(N = 28); and 3) mesothelin-positive advanced pancreatic adenocarcinoma treated with AR at 5.5-6.5 mg/kg IV every 3 weeks plus nivolumab (and ipilimumab or gemcitabine, N = 27). Intensive plasma PK sampling was performed after the first dose to calculate clearance (CL), volume of distribution (Vd), and area-under-the-plasma-concentration-time curve (AUC 0-inf ). The relationship between biomarkers of FcɣRs (CD64, CD32, CD16) on IIS blood cells, total body weight (TBW), body surface area (BSA), lean body mass (LBM), and sex with PK parameters and clinical outcomes were evaluated by pearson correlation, t-test and multivariate regression analysis. Population PK (popPK) methods further evaluated patient covariates and variability in PK. Results: Patients with higher IIS FcγR CD64 and/or higher TBW or higher BSA had higher AR ADC CL (p < 0.05). AR ADC CL was lower in females (0.030 ± 0.007 L/h) versus males (0.042 ± 0.006 L/h) (p < 0.05). Patients with stable disease and partial response had higher AR ADC AUC 0-inf versus patients with progressive disease AR ADC disposition was described by linear CL with two pathways for the release of the payload DM4, hydrolysis and the IIS. A time-varying drug-to-antibody ratio predicted the release of the DM4 payload. In the PopPK model, LBM and albumin were associated with CL of the AR ADC, LBM and IIS FcγR CD64 were associated with the Vd of the AR ADC, and LBM and age were associated with the CL of the released DM4. Conclusions: These results suggest that TBW-based dosing of AR ADC is not optimal, whereas precision dosing of antibodies and ADCs based on the use of novel metrics of body habitus, IIS biomarkers, and sex may be more appropriate to reduce PK variability and improve response.

e20120 Background: In May 2024, the FDA approved tarlatamab, a Delta-like ligand (DLL3)/CD3-targeted bispecific T-cell engager, for patients with extensive-stage small cell lung cancer (SCLC) with disease progression following platinum-based chemotherapy and at least one other prior line of therapy. We aim to evaluate the real-world outcomes of agent. Methods: We conducted a retrospective multi-site single center analysis of adult patients who received tarlatamab at Mayo clinic sites including Arizona, Florida, Iowa, Minnesota, and Wisconsin. Data analysis was performed with Blue Sky statistics version 10.4. Results: Twenty patients with a median age 67 years (range 43-76) were included. Patients were predominantly women (55%) and all had a history of tobacco use. Metastatic disease commonly involved liver (55%) and CNS (60%). Majority (90%) had received prior PDL-1 therapy. 25% (5/20) of patients received prior gamma knife and in addition 10% (2/20) received whole brain radiation treatment in our cohort. Median time from CNS radiation and tarlatamab initiation was 4 months (range 3-28). Other characteristics, outcomes, and toxicity are presented in Table 1. Cytokine release syndrome (CRS) Grade (G) 1 was observed in 45% patients. G 2, 3 and 4 CRS were observed in 5% patients respectively. G 1 CRS was managed with acetaminophen initially followed dexamethasone 10mg or methylprednisone 1g if no improvement in 24 hours. Tocilizumab was used 20% patients for G 1,2,3 and 4 CRS depending on clinical course. Immune effector cell-associated neurotoxicity (ICANS) G 1 occurred in 10% patients, followed by G 2 in 15% and G 3 in 5% patients. ICANS was managed in a multidisciplinary fashion. All patients had resolution of CRS and ICANS. Conclusions: In this study investigating the real-world outcomes and toxicity of tarlatamab, a higher incidence of ICANS was observed than that reported in the DeLLphi-301 trial. The association between presence of CNS metastatic disease, prior CNS radiation and incidence of ICANS needs to be explored further. Mayo Clinic report of tarlatamab real world outcomes and toxicity. Patient Characteristics, Tarlatamab Outcomes and Toxicity Mayo Clinic Report DeLLphi-301 trial- Part 1 & 2 DeLLphi-301 trial- Part 3 ECOG no. (%) 2-4 4 (20) 0 (0) 0 (0) Metastatic Disease no.(%) 19 (95) 98 (98) 32 (94) Median no. of previous lines of therapy (range) 3 (2-4) 2 (1-6) 2 (2-6) Objective Response (%) 30% 40% CRS no (%) 12 (60) 49 (49) 19 (56) ICANS no (%) 6 (30) 7 (7) 4 (12) Neutropenia Grade 3 no (%) 2 (10) 6 (6) 2 (6) Fatal CRS, ICANS or Neutropenia 0 (0) 0 (0) 0 (0)

Abstract Recent studies have described the tumor microenvironment and the key transcription factors in untreated small cell lung cancer (SCLC), but less is known about the salient features in recurrent SCLC (rSCLC). This information could provide valuable insight about the effectiveness of second and later line therapies. In this study, we compared transcriptome profiles (by RNA-seq) of rSCLC against untreated primaries (pSCLC). rSCLC samples (n=23) were obtained from frozen biopsies in patients enrolled in our MC1923 (NCT04607954) phase 2 clinical trial whose disease progressed after chemoimmunotherapy. The pSCLC group (n=73) included publicly available data from fresh frozen primary tumors after surgical resections. Normalized expression data were used in immune deconvolution and gene set enrichment analysis (GSEA) in molecular signature database. Additional GSEA included gene sets describing ASCL1 (A), NEUROD1 (N), ASCL1 and NEUROD1 (AN), and POU2F3 (P) transcription factor activities which are used for subtyping of SCLC. Immune deconvolutions by multiple software algorithms suggested depletion of immune infiltrates in rSCLC compared with pSCLC including dendritic cells, B cells, CD8+ T cells, and M1 macrophages. Furthermore, we found decreased chemotaxis and increased apoptosis of dendritic cells, reduced TNF signaling, and reduced lymphocyte co-stimulation in rSCLC by GSEA. Additionally, in comparisons with pSCLC, rSCLC tumors had significantly lower enrichment scores for POU2F3 activity, representing the SCLC-P subtype (p &lt; 0.007). Importantly, the SCLC-P was recently reported to be more immune inflamed than the other A, N, and AN subtypes. Altogether, our analyses provide strong evidence that the tumor microenvironment of rSCLC is significantly more immunosuppressed and with reduced immune cell infiltrates compared to pSCLC. Developing therapeutic strategies aimed at “warming” the tumor microenvironment and enhancing anti-tumor immune activity in ongoing multimodal therapies of recurrent SCLC will likely provide significant benefits to patients. Citation Format: Farhad Kosari, Mohamed Ali, Sarah H. Johnson, Alex Adjei, Julian R. Molina, Aaron S. Mansfield, Anastasios Dimou, Kaushal Parikh, Mohamed Shanshal, Katherine E. Smith, Ailsa G. Luce, Anna J. Schwecke, Janet Lensing, Ying-Chun Lo, John C. Cheville, George Vasmatzis, Konstantinos Leventakos. Small cell lung cancer (SCLC) at recurrence has a “colder” tumor microenvironment than primary SCLC according to gene expression profiling [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 6614.

Abstract Background: Diffuse pleural mesothelioma (DPM) is a rare and aggressive cancer arising from mesothelial cells of the pleura. Over 2, 500 new cases are diagnosed annually in the United States, mainly attributable to asbestos exposure. The prognosis is poor, and while nivolumab (PD-1 inhibitor) and ipilimumab (CTLA-4 inhibitor) have been approved for first-line treatment of unresectable DPM, the three-year survival rate is only 23%. DPM tumors express high levels of epidermal growth factor receptor (EGFR) and mesenchymal-epithelial transition (MET), but targeted therapies like erlotinib (EGFR tyrosine kinase inhibitors) have shown no clinical benefit. We hypothesized that amivantamab, a bispecific antibody that targets both EGFR and MET, may have activity against DPM through antibody-dependent cellular cytotoxicity (ADCC). Objective: The purpose of this study was to assess the potential of amivantamab to mediate ADCC in tissue culture experiments with DPM cell lines. Methods: We assessed DPM for the expression of EGFR and MET using available data from bulk RNA sequencing. We also examined protein expressions of EGFR and MET by Western blot analysis in five epithelial (EM-Meso, H2452, H2461, Mero-41 and Mero-95), three sarcomatoid (H2373, H2596 and ONE58), and one normal mesothelial (MeT-5A) cell lines. Co-culture experiments were performed with the DPM and normal cell lines and NK cells in the presence of amivantamab to evaluate ADCC. Results: We identified high levels of EGFR and MET expression in both epithelial and sarcomatoid cases of DPM from 183 patients. This finding was corroborated by Western blot analysis of all eight DPM cell lines. In vitro experiments demonstrated that amivantamab induced dose-dependent ADCC in DPM cell lines, with robust NK cell-mediated ADCC observed across all tested DPM lines. Notably, sarcomatoid-type DPM cells were more sensitive to amivantamab-induced ADCC than epithelial-type cells. These findings suggest that amivantamab may offer therapeutic benefits for DPM tumors with high EGFR and MET expression. Conclusion: This study provides preclinical evidence supporting the potential of amivantamab as a novel therapeutic option for DPM, especially in sarcomatoid tumors. Ongoing in vivo studies including in patient-derived xenograft (PDX) models will further evaluate the efficacy of amivantamab in DPM. Citation Format: Shinichiro Suzuki, Lin Yang, Jennifer Ayers-Ringler, Ezequiel J. Tolosa, Kuan-Li Wu, Janet L. Schaefer-Klein, Farhad Kosari, Aaron S. Mansfield. Antitumor activity of amivantamab in diffuse pleural mesothelioma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 7331.

Despite ongoing efforts to employ structure-based methods to discover targeted protein degraders (TPD), the prevailing strategy remains synthesizing a focused set of heterobifunctional compounds and screening them for target protein degradation.

ABSTRACTAnetumab ravtansine, like other ADC drugs, has high inter‐patient variability in its pharmacokinetic (PK) and pharmacodynamic (PD) outcomes, which raises concerns about whether current dosing regimens are optimal for patients. The objective of this study was to evaluate covariates, especially body habitus and the innate immune system (IIS), which may affect anetumab ravtansine PK and PD as part of two clinical trials in patients with ovarian cancer and mesothelioma. Biomarkers of Fcγ receptors(FcγR) CD64 on IIS cells, total body weight (TBW), body surface area (BSA), and other covariates, such as sex and age, were analyzed for an association with anetumab ravtansine PK. Higher FcγR CD64, TBW, and BSA were associated with higher clearance (CL) of anetumab ravtansine (p < 0.05). However, there was no relationship between TBW or BSA and FcγR CD64. Female patients had a lower anetumab ravtansine CL (0.030 ± 0.007 L/h) compared to male patients (0.042 ± 0.006 L/h) (p < 0.05). In both studies, patients with stable disease (SD) and partial response (PR) had higher anetumab ravtansine AUC0‐inf compared to patients with progressive disease (PD). Individualizing the dose of anetumab ravtansine and potentially other ADCs based only on TBW is not optimal, whereas precision dosing of an ADC based on the inclusion of novel metrics of IIS biomarkers, body habitus, and sex may be more appropriate to reduce variability in PK exposure, reduce toxicity, and improve response.

Abstract Introduction: Immune checkpoint inhibitors (ICI) are an essential systemic therapy for advanced melanoma. However, most melanomas develop resistance to ICI. Tumor-derived soluble PD-L1 (sPD-L1) and other soluble immunosuppressive factors drive checkpoint inhibitor resistance and correlate with inferior survival. We previously showed that therapeutic plasma exchange (TPE) removes sPD-L1 from circulation. Thus, we hypothesized that TPE-mediated removal of sPD-L1 and other immunosuppressive factors could overcome immunotherapy resistance in refractory melanoma. Methods: In this clinical trial (NCT04581382), we prospectively enrolled eighteen (18) patients with widely metastatic melanoma with progression despite anti-PD-1 ICI and elevated sPD-L1 by ELISA (≥1.7ng/mL). Each patient received radiotherapy to between one and three metastatic lesions (at least two unirradiated lesions) followed by three TPE sessions on consecutive days and re-challenge with checkpoint inhibitor. The primary safety and efficacy endpoints of the study were adverse events (AEs) and sPD-L1 reduction by TPE, respectively. Secondary endpoints included RECIST-based response in unirradiated lesions and overall survival. Correlative studies included kinetics of sPD-L1 and soluble immonsuppressive factors and dynamics of peripheral immune cell phenotypes. Results: Mean age was 62 (SD 13) and seven of eighteen (39%) were female. Mean baseline sPD-L1 was 26.31 ng/mL (40.01). The treatment was well-tolerated with one (6%) patient with grade 3 and 4 adverse events from a central line infection after TPE. Levels of sPD-L1 were significantly reduced by TPE (mean 80.2% reduction, p<0.0001). Two patients (11.1%) experienced complete response (CR), one (5.6%) partial response, three (16.7%) stable disease, and 12 (66.7%) progressive disease. In one case, immunotherapy was discontinued after two years due to no detectable lesions. Changes in tumor-reactive (TTR) GZMB+/CX3CR1+/CD11ahigh and other peripheral immune cell populations predicted overall survival in this cohort. In addition to sPD-L1, other soluble mediators of ICI resistance were also reduced by TPE and predicted overall survival in this cohort. Summary/Conclusion: sPD-L1 and other soluble immunoregulatory signaling molecules are important mediators of ICI resistance. SBRT and TPE can resensitize ICI-refractory melanoma by removing these factors. Patients with persistently elevated or rapid rebound of sPD-L1 following TPE experienced poor response and overall survival. Serial monitoring of sPD-L1 may predict response to ICI and multiple courses of TPE may be necessary. Our findings may apply in other ICI-resistant cancers with elevated sPD-L1. ClinicalTrials.gov registration: NCT04581382, ReCIPE-M1 (Rescuing Cancer Immunotherapy with Plasma Exchange in Melanoma 1).

e20588 Background: MET exon 14 skipping mutations are seen in about 3% of patients (pts) with NSCLC, with 2 FDA approved METi for pts with stage IV NSCLC harboring it. Besides the original clinical trials, there is a paucity of real-world data about their outcomes, and adverse events (AE). Our aim was to compare and analyze the utilization of capmatinib (cap) and tepotinib (tep) in this population. Methods: We performed a retrospective chart review of the electronic medical records of all pts with stage IV NSCLC treated with METi between the date of FDA-accelerated approval of these drugs, 5/6/20 for cap and 2/3/21 for tep, and 12/1/23. All pts were treated at the Mayo Clinic Health System. We collected data about baseline characteristics, diagnosis, AE, and outcomes. Chi-squared test was used to compare the frequency of AE, while Kaplan-Meier method was used to calculate median progression free survival (mPFS). Results: A total of 49 pts were treated with METi. Cap was used in 45 pts, 14 received tep, and 10 pts received both, with tep following cap. In the cap group, median age of diagnosis was 74 years (y), 42.22% were male, and the median number of previous lines of therapy (mPLT) was 0. In the tep group, median age of diagnosis was 72 y, 21.43% were male, and the mPLT was 2. Median ECOG at the time of diagnosis was 1 in both groups. There was no statistically significant difference between AE in both groups. Peripheral edema occurred in 75.56% pts who received cap, and in 64.29% with tep (p = 0.41). Pneumonitis happened in 4.44% with cap, and 7.14% with tep (p = 0.69). Creatinine elevation was seen in 37.78% with cap, while 42.86% with tep (p = 0.73), grade 3 elevation was seen in 5.88% and 16.67% respectively. Abnormality in liver function tests occurred in 35.56% of pts in the cap group, and 28.57% in the tep group (p = 0.63), grade 3/4 abnormality occurred in 31.25% and 0% respectively. Finally, pancreatic enzymes elevation was seen in 33.33% of patients in each group (p = 0.67), with none being grade 3/4. Cap was discontinued in 20% of pts due to AE, while it happened in 28.57% of pts with tep. Dose reduction happened in 64.44% of pts who received cap, and 42.86% who received tep. The mPFS was 12.03 months (m) in the cap group, and 8.94 m in the tep group, which was not statistically significant (p = 0.18). Similarly, the mPFS in those treated with tep following cap was 8.94 m. Conclusions: We performed the first real-word comparison between cap and tep. The results demonstrated similar outcomes with both drugs, and no significant differences in AE, suggesting these agents can be employed equivalently. Importantly, rates of therapy discontinuation and dose reduction were high with both, indicating the importance of closely monitoring these pts. The retrospective nature and small sample size are initial limitations that can be overcome with future multi-centric prospective studies.

8071 Background: Data from the PACIFIC study demonstrated a 5-yr median progression free survival (PFS) and overall survival (OS) of 16.9 and 47.5 months respectively for patients with stage 3A and stage 3B NSCLC demonstrating a high risk of relapse. The 8th ed. of the IASLC staging project reports that the 60-month OS for stage 3A, B and C disease is 41%, 24% and 12% respectively, indicating that improved treatment options are needed for this patient population. Induction chemo-IO (ID chemo-IO) followed by concurrent chemo-radiation (CRT) has not been fully investigated due to concerns regarding the toxicity profile, but this may representant an important unexplored avenue for research. We aim to describe the outcomes of patients who received ID chemo-IO followed by CRT with or without maintenance IO. Methods: We conducted a retrospective study across all Mayo Clinic sites. Patients were included if they were diagnosed with Stage 3 NSCLC deemed ineligible for resection and/or requiring raditation over a large-field ] by a multidisciplinary team with plans for ID chemo-IO prior to CRT and maintenance IO. A total of 927 cases of stage 3 NSCLC patients were screened and those receiving ID chemo-IO followed by CRT were extracted (n = 36). Clinical endpoints are PFS, OS, overall response rate (ORR) and treatment related adverse events (TrAE) defined using CTCAE 5.0. Results: The median age was 67 years, 52.8% were female, all patients were past smokers and 97.2% identified as white. The tumor histologies were adenocarcinoma (66.67%), squamous (27.8%), mucinous adenocarcinoma (2.8%) and sarcomatoid (2.8%). Majority were Stage 3B (47.2%) followed by 3C (38.9%) and 3A (13.9%). N2 and N3 disease was noted in 36.1% and 55.6% of patients respectively. PD-L1 by IHC was > 1-49% (47.2%), > 50% (22.2%) and < 1% (19.4%). Patients received ID chemo-IO with pembrolizumab (83.3%), nivolumab (11.1%) and atezolizumab (2.78%). Average number of ID chemo-IO cycles were 3.67 cycles. The ORR to ID chemo-IO was 86.11%. The median PFS was 23.67 mths and the median OS was 32.07 months. About 94% of patients received CRT afterwards and 66.67% received maintenance IO with pembrolizumab (53.17%) or durvalumab (45.83%). Any grade TrAE occured in 58.33% of patients. Pneumonitis was the most common event (38.9%). Grade 3 -4 pneumonitis was noted in 28.5% (4/11) patients. Other toxicities included hepatitis (8.3%), colitis (11.1%) and myasthenia gravis (2.8%) and 22% of these TrAE’s were grade 3 or 4. Conclusions: Our results indicate that ID chemo-IO shows promise as a therapeutic approach for patients with unresectable stage III NSCLC, especially for patients deemed ineligible or high risk for upfront radiation. Further investigation is needed through a randomized clinical trial to systematically explore and validate the safety and efficacy of ID chemo-IO.