Grierson, Patrick

TPS2698 Background: Chimeric antigen receptor (CAR) T-cell therapies for treating solid tumors are challenging due to a lack of tumor-specific targets that discriminate cancer from normal cells. Previous studies using CEA T-cell receptors and T-cell engagers have resulted in dose-limiting, on-target, off-tumor toxicities (1,2). A2B530 is an autologous logic-gated, CEA-targeted Tmod CAR T-cell therapy that addresses the challenges of on-target, off-tumor toxicity by combining a CAR-activating receptor with a blocking receptor to discriminate tumor from normal cells (3). The activator recognizes CEA on the surface of both tumor and normal cells while specificity for tumor cells is provided by a blocker that binds HLA-A*02. In patients with both germline HLA-A*02 and tumor-associated HLA-A*02 LOH, the blocker prevents on-target, off-tumor toxicity on normal cells owing to retained HLA-A*02 expression (4). HLA-A*02 LOH can be detected using next-generation sequencing (Tempus AI, Inc.). With this definitive discriminator target, A2B530 can potentially provide a therapeutic window to treat patients with CEA-expressing solid tumors exhibiting HLA LOH. Methods: EVEREST-1 (NCT05736731) is a seamless, phase 1/2, open-label, nonrandomized study to evaluate the safety and efficacy of A2B530 in adult patients. Patients are enrolled through BASECAMP-1 (NCT04981119), a master prescreening study that identifies patients with HLA LOH at any time in the course of their disease. BASECAMP-1–eligible patients undergo leukapheresis and, when clinically appropriate, their banked T cells are manufactured for the EVEREST-1 study. The key inclusion criteria include histologically confirmed recurrent unresectable, locally advanced, or metastatic cancers associated with CEA expression: non-small cell lung, colorectal, or pancreatic cancers. Patients should have received ≥1 line of prior therapy such as checkpoint inhibitor, molecular targeted, or chemotherapy. The primary objective of phase 1 is to evaluate the safety and tolerability of A2B530 and determine the recommended phase 2 dose (RP2D). The dose-escalation portion is based on the Bayesian optimal interval design. The dose-expansion phase will confirm RP2D and collect biomarker data to further characterize A2B530. Phase 2 will assess overall response rate per RECIST v1.1. As of January 29, 2024, 8 patients have been enrolled on EVEREST-1. A2B530 was successfully manufactured for all patients, and all patients have received A2B530 infusion, with the first patient dosed in May 2023. Dose escalation is ongoing. 1. Parkhurst, et al. Mol Ther. 2022. 2. Tabernero, et al. J Clin Oncol. 2017. 3. Hamburger, et al. Mol Immunol. 2020. 4. Sandberg, et al. Sci Transl Med. 2022. Clinical trial information: NCT05736731 .

1604 Background: Diversity in clinical studies is essential to address health disparities, but racial and ethnic minorities are often underrepresented in clinical studies, especially in precision medicine studies using genetic data (1). BASECAMP-1 (NCT04981119) is an ongoing prescreening study to identify patients with unresectable advanced or metastatic solid tumors and tumor-associated HLA-A*02 LOH for the EVEREST-1 and -2 Tmod chimeric antigen receptor T-cell therapy trials. When enrollment began in 2021, eligibility for Part 1 was restricted to patients with germline HLA-A*02:01 based on preclinical data. Additional analysis revealed the blocker in the Tmod construct had activity across HLA-A*02 subtypes (Mock, et al. Mol Ther Oncolytics.2022). Eligibility for Part 1 was then expanded to all HLA-A*02 subtypes, allowing enrollment of more diverse patient populations. HLA-A*02 allele subtypes vary by ethnicity and race; the frequency of HLA-A*02:01 is 96% in non-Hispanic Whites, but ranges from 53% to 73% in other ethnicities and races. The frequency of all other HLA-A*02 allele subtypes (HLA-A*02:XX) is <5% in non-Hispanic Whites but up to 66% in other ethnicities and races (2,3). Methods: Patients eligible for BASECAMP-1 were identified at United States study sites. All patients screened before January 16, 2024, for Part 1 were included for demographic and central lab HLA-A typing. The % increase in eligibility and % of heterozygous HLA-A*02 patients with HLA-A*02:XX were calculated by ethnicity and race. Results: A total of 1124 patients were screened for germline HLA-A*02 typing; 431 patients were HLA-A*02:01 heterozygous, of whom 37 (9%) were Hispanic, 14 (3%) African American (AA), 2 (<1%) American Indian or Alaska Native, 17 (4%) Asian or Pacific Islander (API), and 324 (75%) non-Hispanic White (Table). The eligibility expansion identified 62 patients with HLA-A*02:XX heterozygosity, of whom 6 (10%) were Hispanic, 6 (10%) AA, 19 (31%) API, and 25 (40%) non-Hispanic White. Conclusions: By expanding enrollment to include HLA-A*02:XX, 16% more Hispanic, 43% more AA, and 112% more API patients were identified, improving the diversity in this trial compared with that of initial enrollment. 1. Aldrighetti, et al. JAMA Netw Open 2021. 2. Ellis, et al. Human Immunol. 2000. 3. Gragert, et al. Human Immunol.2013. Clinical trial information: NCT04981119 . [Table: see text]

100 Background: HER2 is overexpressed in various GI tumors. Tucatinib (TUC), which is approved in combination with trastuzumab (Tras) in the US for previously treated RAS WT HER2+ metastatic colorectal cancer (mCRC), is a tyrosine kinase inhibitor highly selective for HER2. Preliminary safety and antitumor activity results of TUC + trastuzumab + FOLFOX in patients (pts) with HER2+ GI cancers are presented. Methods: The phase 1b/2 SGNTUC-024 (NCT04430738) study evaluated TUC + Tras + FOLFOX in pts with HER2+ metastatic GI cancers in Cohorts 1A, 1B, 1D (pts in Japan), and 2B. For Cohorts 1A, 1B, and 1D (enrolled sequentially), eligible pts had unresectable or metastatic HER2+ GI malignancies, including mCRC. Cohort 2B is still enrolling, and pts with HER2+ mCRC are eligible. Pts received a combination of TUC 150 mg orally twice a day (PO BID; Cohort 1A) or TUC 300 mg PO BID (Cohorts 1B, 1D, and 2B) + Tras + FOLFOX. Pts in Cohort 2B were enrolled to further assess the study regimen. Antidiarrheal prophylaxis was required for Cohort 1D. Results: As of July 10, 2023, 25 pts were treated (5, 11, 7, and 2 in Cohorts 1A, 1B, 1D, and 2B, respectively). In Cohort 1A (TUC 150 mg PO BID), the most common TEAEs were diarrhea, fatigue, nausea, and proteinuria (each in 60.0% [3/5]). For pts receiving TUC 300 mg PO BID, the most common TEAEs were diarrhea (90.0% [18/20]) and fatigue (65.0% [13/20]). Table 1 presents the overall summary of adverse events. In Cohort 1A, Treatment-emergent adverse events (TEAEs) leading to any treatment discontinuation were reported in 40.0% (2/5) pts, with 20.0% (1/5) discontinuing tucatinib. For pts treated with TUC 300 mg, TEAEs leading to treatment discontinuation were reported in 35.0% (7/20), with 15.0% (3/20) discontinuing tucatinib. One TEAE leading to death (aspiration) in Cohort 1A was unrelated to study treatment. Grade ≥3 diarrhea was observed in 45.5% (5/11) pts in Cohort 1B; most were observed in elderly pts or pts with gastric, gastroesophageal, or esophageal cancer or pts who were generally noncompliant with antidiarrheal treatment. No grade ≥3 diarrhea was observed in Cohort 1D. Among pts receiving TUC 300 mg, confirmed objective response rate was 83.3% (5/6) for mCRC, 40.0% (4/10) for gastroesophageal cancers, and 0% (0/4) for biliary tract cancer. Conclusions: TUC + Tras + FOLFOX showed manageable safety in the enrolled pt population and preliminary antitumor activity in pts with HER2+ mCRC and gastroesophageal cancer. This regimen will be compared with the standard of care (FOLFOX with or without bevacizumab/cetuximab) in the ongoing randomized, phase 3 study (MOUNTAINEER-03; NCT05253651) for pts with HER2+ RAS WT mCRC. Clinical trial information: NCT04430738 . [Table: see text]

Cancers originating in the esophagus or esophagogastric junction constitute a major global health problem. Esophageal cancers are histologically classified as squamous cell carcinoma (SCC) or adenocarcinoma, which differ in their etiology, pathology, tumor location, therapeutics, and prognosis. In contrast to esophageal adenocarcinoma, which usually affects the lower esophagus, esophageal SCC is more likely to localize at or higher than the tracheal bifurcation. Systemic therapy can provide palliation, improved survival, and enhanced quality of life in patients with locally advanced or metastatic disease. The implementation of biomarker testing, especially analysis of HER2 status, microsatellite instability status, and the expression of programmed death-ligand 1, has had a significant impact on clinical practice and patient care. Targeted therapies including trastuzumab, nivolumab, ipilimumab, and pembrolizumab have produced encouraging results in clinical trials for the treatment of patients with locally advanced or metastatic disease. Palliative management, which may include systemic therapy, chemoradiation, and/or best supportive care, is recommended for all patients with unresectable or metastatic cancer. Multidisciplinary team management is essential for all patients with locally advanced esophageal or esophagogastric junction cancers. This selection from the NCCN Guidelines for Esophageal and Esophagogastric Junction Cancers focuses on the management of recurrent or metastatic disease.