Go, William Y.

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]

209 Background: Metastatic colorectal (CRC), pancreatic (PANC), and gastroesophageal cancers are the leading causes of GI cancer–related mortality (5-y survival: 15%, 3%, and 5%-6%, respectively) (ACS 2022). HLA LOH is a recurrent mechanism of immune escape observed in 15%-20% of GI cancers (Hecht R., ASCO GI 2022). The Tmod platform is a logic-gated chimeric antigen receptor (CAR) T-cell modular system, comprising a carcinoembryonic antigen (CEA)- or mesothelin (MSLN)-targeting CAR activator and a separate HLA-A*02-targeting blocker receptor. Both in vitro/in vivo, Tmod CAR T therapy kills cells with HLA-A*02 LOH (tumor) without harming cells with retained HLA-A*02 expression (normal). However, HLA-A*02 LOH can only be therapeutically exploited if patients are identifiable through a feasible and timely clinical workflow. Methods: We established a biobanking protocol (BASECAMP-1, NCT04981119) to determine whether HLA-A*02 LOH patients can be prospectively identified. Patients with CRC, PANC, or non-small cell lung cancer (NSCLC), and a high risk for incurable relapse, were screened first using a standard HLA assay. Heterozygous HLA-A*02 positive tumor samples were then assessed for LOH using a bioinformatic algorithm applied via the Tempus xT platform. Results: As of Sep 1, 2022, 83 patients were consented at 4 institutions. HLA status was obtained from 70 patients and 28 were identified as HLA-A*02:01 heterozygous (40%; expected frequency based on USA NMDP data, 27.6%). LOH results were available for 16 patients; 4 LOH-positive patients were identified (25%, 2 PANC, 2 NSCLC). The LOH assay sensitivity declines below a tumor purity of 40% (Hecht R., ASCO GI 2022). Six patients had a tumor purity of 20% (all with PANC, a tumor known for high stromal content), limiting possible LOH detection. The impact of tumor purity on LOH sensitivity was highlighted in a patient with a low initial sample tumor purity (30%) that resulted in a 41% probability of HLA-A*02:01 LOH (below positive threshold). A second sample with a higher tumor purity (70%), obtained from formalin-fixed, paraffin-embedded sections, resulted in a 92% probability of HLA-A*02:01 LOH (positive). Conclusions: BASECAMP-1 prospective identification of HLA-A*02 LOH is feasible in the real-world setting. The frequencies of the HLA-A*02 allele and of HLA-A*02 LOH in this cohort mirrored expected population frequencies. LOH results can be obtained within a clinically feasible workflow and timeframe, although samples with a < 40% tumor purity have a reduced sensitivity for LOH detection, an issue recurrently observed in patients with PANC. The BASECAMP-1 strategy enables prospective identification of appropriate patients for future therapeutic clinical trials using Tmod CEA and MSLN logic-gated CAR T cells. Clinical trial information: NCT04981119 .

Head and neck squamous cell cancers (HNSCCs) represent a diverse group of tumors emerging within different mucosal surfaces of the oral cavity, nasopharynx, oropharynx, larynx, and hypopharynx. HNSCCs share common clinical risk factors and genomic features, including smoking, alcohol, age, male sex, aneuploidy, and TP53 mutations. Viral initiating and contributing events are increasingly recognized in HNSCCs. While both Epstein–Barr Virus (EBV) and human papilloma virus (HPV) are observed, EBV is more frequently associated with nasopharyngeal cancers whereas HPV is associated with oropharyngeal cancers. HNSCCs are associated with high tumor mutational burden and loss of tumor suppressor gene function, especially in TP53 and X-linked genes. Multiple lines of evidence suggest that HNSCCs are subject to immunologic surveillance and immune-induced evolutionary pressure that correlate with negative clinical outcomes. This review will discuss genomic mechanisms related to immune-mediated pressures and propose prognostic and therapeutic implications of detectable immune escape mechanisms that drive tumorigenesis and disease progression.

Abstract Background: ZUMA-1 is a pivotal, multicenter trial of axi-cel, an autologous anti-CD19 chimeric antigen receptor (CAR) T cell therapy, for the treatment of patients with refractory, aggressive NHL. The objective response rate (ORR) was 82% with a 54% rate of complete response and 44% of responses were ongoing at the time of the primary analysis (Locke et al. AACR 2017. #9986). Grade ≥ 3 cytokine release syndrome (CRS) and neurologic events (NE) occurred in 13% and 28% of patients, respectively. A safety expansion cohort was added to further characterize mechanisms underlying CRS and NE associated with CAR T cell therapy and to evaluate the impact of prophylactic use of tocilizumab and levetiracetam on the rates of these adverse events (AEs). Methods: Patients (≥ 18 years) must have had an Eastern Cooperative Oncology Group performance status of 0-1 and refractory or relapsed transplant ineligible disease. Patients received low-dose conditioning of 500 mg/m2 cyclophosphamide and 30 mg/m2 fludarabine for 3 days followed by axi-cel at a target dose of 2 × 106 CAR T cells/kg. Patients also received prophylactic treatment with 750 mg of levetiracetam twice a day on day 0 and 8 mg/kg of tocilizumab on day 2 post axi-cel infusion. To evaluate the mechanisms of NE, paired serum and cerebrospinal fluid (CSF) were obtained for all patients prior to conditioning chemotherapy and after axi-cel infusion (day 5). Results: As of April 26, 2017, 31 patients received axi-cel. Median age was 51 years (range, 21-74), 52% were male, 65% had stage III-IV disease, 74% were refractory to ≥ second-line therapy, and 19% relapsed ≤ 12 months after autologous stem cell transplant. Most patients (97%) experienced at least 1 grade ≥ 3 AE. The most common grade ≥ 3 AEs were neutropenia/neutrophil count decreased (71%), anemia (55%), thrombocytopenia/platelet count decreased (52%), leukopenia/white blood cell count decreased (35%), febrile neutropenia (29%), encephalopathy (23%), and hypotension (23%). One patient (3%) experienced a grade ≥ 3 (grade 4) CRS. Grade 3 and 4 NE occurred in 29% and 6% of patients, respectively. One patient died of cerebral edema; there were no other deaths due to AE. Updated efficacy, safety, subgroups, and paired blood/serum/CSF biomarker associative analyses will be presented. Conclusions : Early use of tocilizumab may reduce the incidence of severe CRS but not NE in patients treated with CAR T cell therapy. These data provide evidence that the underlying pathophysiology of NE may differ from that of CRS. Understanding the mechanisms of NE may help to further improve the benefit:risk profile for CAR T cell therapy. Drs Locke and Neelapu contributed equally to this work. Disclosures Locke: Kite Pharma: Consultancy; Cellular Biomedicine Group Inc: Consultancy. Neelapu: Kite Pharma: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; BMS: Research Funding; Merck: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Poseida: Research Funding; Cellectis: Research Funding; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees. Jacobson: Pharmacyclics, LLC: Consultancy; Kite Pharma: Consultancy. Braunschweig: Kite Pharma: Equity Ownership. Oluwole: Kite Pharma: Consultancy. Siddiqi: Seattle Genetics: Speakers Bureau; Juno: Other: Steering committee for JCAR017; Pharmacyclics, an AbbVie Company: Other: Steering committee for ibrutinib, Speakers Bureau. Timmerman: Celgene: Consultancy; Seattle Genetics: Consultancy; Kite Pharma: Research Funding; ImmuneGene: Research Funding; Bristol-Myers Squibb: Consultancy, Honoraria, Other: Travel expenses, Research Funding; Genmab: Consultancy, Equity Ownership. Reagan: Seattle Genetics: Research Funding. Bot: Kite Pharma: Employment, Equity Ownership. Rossi: Kite Pharma: Employment, Equity Ownership. Sherman: Kite Pharma: Employment, Equity Ownership. Navale: Kite Pharma: Employment, Equity Ownership. Jiang: Kite Pharma: Employment, Equity Ownership. Aycock: Kite Pharma: Employment, Equity Ownership. Elias: Kite Pharma: Employment, Equity Ownership. Wiezorek: Kite Pharma: Employment, Equity Ownership. Go: Kite Pharma: Employment, Equity Ownership. Miklos: Pharmacyclics, LLC: Consultancy, Other: Travel expenses, Patents & Royalties, Research Funding; Kite Pharma: Consultancy, Other: Travel expenses, Research Funding; Adaptive Biotechnologies: Consultancy, Other: Travel expenses; Roche: Research Funding; Genentech: Research Funding; Novartis: Research Funding; Janssen: Consultancy, Honoraria, Other: Travel expenses; Sanofi: Honoraria.