Mackall, Crystal L.

Abstract Chimeric antigen receptor (CAR) T-cell therapy has emerged as a transformative treatment for hematological malignancies, yet its potential to drive lymphomagenesis poses significant clinical concerns. In this study, we investigated the mechanisms underlying CAR T-cell–associated lymphomagenesis in the gastrointestinal (GI) tract on a single case, focusing specifically on the role of integrin α4β7 expression and a predisposing somatic SH2B3 mutation. We observed oligoclonal CAR T cells homing to, and clonally expanding in, the GI tract, with the dominant expanded clone harboring both a pathogenic SH2B3 mutation and a CAR transgene integration within a TFCP2 locus. The clonal CAR T cells subsequently transitioned beyond the GI tract into the peripheral blood, suggesting a potential pathway for systemic dissemination. We found clinical, histological, and molecular evidence demonstrating the efficacy of cyclosporine in reducing the expanded malignant clone and achieving durable clinical remission for more than a year. Our findings highlight the complex interplay between CAR T-cell therapy, preexisting genetic vulnerabilities, and the GI microenvironment, emphasizing the need for vigilant monitoring and tailored therapeutic strategies to address the risks associated with CAR T-cell lymphomagenesis.

Abstract Purpose: In many cancers, nivolumab in combination with ipilimumab improves response rates compared with either agent alone, but the combination has not been evaluated in childhood cancer. We conducted a phase I/II trial of nivolumab plus ipilimumab in children and young adults with recurrent/refractory solid tumors. Patients and Methods: ADVL1412, Part C assessed safety of nivolumab plus ipilimumab at two dose levels (DL): DL1 1 mg/kg of each drug and DL2 3 mg/kg nivolumab plus 1 mg/kg ipilimumab. Part D evaluated response at the recommended phase II dose (RP2D) in Ewing sarcoma, rhabdomyosarcoma, and osteosarcoma. Part E tested DL3 (1 mg/kg nivolumab plus 3 mg/kg ipilimumab) in Ewing sarcoma and rhabdomyosarcoma. Tumor response was measured using RECIST v1.1. Pharmacokinetics and PD-L1 expression on archival tissues were assessed. Results: Fifty-five eligible patients enrolled. Based on safety, tolerability, and similar drug exposure to the same doses administered in adults, DL2 was defined as the pediatric RP2D. Among 41 patients treated at the RP2D, 2 patients experienced dose-limiting toxicities during cycle 1, and 4 patients experienced toxicities beyond that period. Two patients had clinically significant sustained partial responses (1 rhabdomyosarcoma, 1 Ewing sarcoma) and 4 had stable disease. Among 8 patients treated at DL3, 3 dose-limiting toxicities (DLT) occurred, all immune-related adverse events; no objective responses were observed. Conclusions: The RP2D of nivolumab (3 mg/kg) plus ipilimumab (1 mg/kg) is well tolerated in children and young adults with solid tumors and shows some clinical activity. Increased dose of ipilimumab (3 mg/kg) plus nivolumab (1 mg/kg) was associated with increased toxicity without clinical benefit.

Background: Early data from anti-CD19 chimeric antigen receptor (CAR) T-cell trials suggest that concurrent infection can lead to poor outcomes. 1,2 The relationship between CAR T-cell mediated inflammatory responses and infections is not well-established. With CAR T-cell therapies more readily available, practitioners must identify which patient, disease and CAR T-cell specific parameters are associated with an increased risk of infection to optimize outcomes. We provide a comprehensive analysis of infection risk within the first 30 days after CAR T-cell infusion across multiple types of CAR T-cell trials targeting distinct antigens. Methods: This was a single-center, retrospective study conducted at the National Cancer Institute analyzing infectious complications in subjects who underwent CAR T-cell therapy on one of four phase I clinical trials, targeting CD19, CD22, B-cell maturation antigen (BCMA) or disialoganglioside (GD2) from 2012 though 2018. Baseline characteristics are in Table 1. The primary objective was to establish the incidence of infections between initiation of lymphodepleting (LD) chemotherapy through day 30 after CAR T-cell infusion. The secondary objective was to identify risk factors for infection. Patients were censored at relapse and/or initiation of alternative therapy, including treatment for relapse or consolidative hematopoietic stem cell transplantation (HSCT). Univariate screening methods were used to identify parameters associated with increased risk of infection Results: Amongst 144 subjects, 52 (36.1%) received anti-CD19 CAR T-cells (CAR-T); 53 (36.8%) received anti-CD22 CAR-T, 26 (18.1%) received anti-BCMA CAR-T; and 13 (9%) received anti-GD2 CAR-T. The median age was 18 years (range: 4 to 66). Sixty-one (42.4%) had undergone at least one prior allogeneic hematopoietic stem cell transplant (HSCT) and 24 (16.7%) had at least one prior autologous HSCT. Sixty-eight (47.2%) had a history of a recent infection within 100 days of initiation of LD chemotherapy, of which 17 were a major chronic infection and 9 were considered severe. Fifty-eight (40.3%) subjects experienced a total of 103 infections from initiation of LD chemotherapy through day 30 post CAR T-cell infusion, with the median time to first infection being 6 days post-CAR infusion. Twenty-eight (19.4%) subjects had more than 1 infection; 20 (13.9%) subjects had C. difficile infection. The 103 infections consisted of 47 (45.6%) distinct episodes of focal bacterial infections (e.g., sinusitis, pneumonia, urinary tract infection), 25 (24.2%) episodes of bacteremia, 22 (21.4%) viral infections, and 9 (8.7%) invasive fungal infections. Fourteen infections (13.6%) occurred between initiation of LD chemotherapy and day 0 (prior to CAR T-cell infusion). Fever and neutropenia, without a source, was documented as a distinct entity in 85 patients (59.0%). Using univariate statistical screening methods, we identified 4 parameters that were individually associated with an increased risk of infection: increasing number of prior therapies (p=0.0034), prior history of recent infection within the past 100 days (p=0.0064), age > 18 (p =0.028), or enrollment on the CD22 CAR trial (p=0.0028). Eliminating the trial, since that is not generalizable, and combining these into a multivariable logistic regression model identified age > 18, prior history of infection and prior lines of therapies jointly associated with an increased risk of infection. Using these parameters, a predictive model was developed, which, when applied to the data set used to develop the model, can correctly predict 69 of 86 patients without an infection (80.3%; CI: 70.3-88.0%) as well as 32 of 58 patients with an infection (55.2%; 95% CI: 41.5- 68.3%). Conclusion: In this retrospective analysis, we provide the largest experience to date analyzing infection in the setting of CAR T-cell therapy across multiple CAR constructs. Our study demonstrates that adult age, prior history of infection, increased number of prior therapies and enrollment on a particular CAR T-cell trial, in this case the CD22 CAR-T trial, may lead to a higher risk of infection than in those without these risk factors. Further investigations are underway to evaluate clinical outcomes with infection which occur in the peri CAR T-cell setting and potential strategies to minimize infection risk. Generalizability of this model will be tested in an independent data set. Disclosures Lee: Kite, a Gilead Company: Research Funding; Harpoon Therapeutics: Consultancy; Juno Therapeutics: Other: External Advisory Board; ACI Clinical on behalf of Celgene:: Other: Independent Central Quality Review Committee. Mackall:Obsidian: Research Funding; Lyell: Consultancy, Equity Ownership, Other: Founder, Research Funding; Nektar: Other: Scientific Advisory Board; PACT: Other: Scientific Advisory Board; Bryologyx: Other: Scientific Advisory Board; Vor: Other: Scientific Advisory Board; Roche: Other: Scientific Advisory Board; Adaptimmune LLC: Other: Scientific Advisory Board; Glaxo-Smith-Kline: Other: Scientific Advisory Board; Allogene: Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Apricity Health: Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Unum Therapeutics: Equity Ownership, Membership on an entity's Board of Directors or advisory committees. Kochenderfer:Kite and Celgene: Research Funding; Bluebird and CRISPR Therapeutics: Other: received royalties on licensing of his inventions. OffLabel Disclosure: Conditioning chemotherapy for CAR T-cell therapy; this is a retrospective study that used different lymphodepletion regimens.

10526 Background: Checkpoint inhibitors have produced impressive responses in cancer. We report results of a Phase 1 study of nivolumab (nivo) alone and in combination with ipilumumab (ipi) in children with relapsed/refractory solid tumors and activity of nivo in patients with osteosarcoma (OS) and Ewing sarcoma (EWS) treated with the RP2D. Methods: Children with relapsed/refractory solid tumors (excluding CNS tumors or metastases) were eligible for Phase I Cohorts A and C. Using a rolling 6 design, Cohort A tested nivo at the adult RP2D, 3mg/kg Q14d (cycle = 28d). Cohort C tested nivo + ipi at 2 dose levels (DLs): DL1 nivo 1mg/kg + ipi 1mg/kg and DL2 nivo 3mg/kg + ipi 1mg/kg Q21d x 4 then nivo alone Q14d. At the RP2Ds, 6 additional patients were enrolled in each cohort for pharmacokinetics (PK). Phase II expansion cohorts enrolled patients with measurable OS (Cohort B2, n = 10) or EWS (Cohort B4, n = 10) respectively to assess activity of the RP2D of single agent nivo. Results: Twelve evaluable patients enrolled in Cohort A, none had DLTs. The pediatric RP2D of nivo alone was identified as 3 mg/kg Q14d. Five evaluable patients enrolled in Cohort C:DL1 without DLT, then 12 patients enrolled in Cohort C:DL2 with one DLT within the 21d reporting period (Gr 2 creatinine increase), defining the RP2D of nivo 3mg/kg + ipi 1mg/kg at the schedule above. In 39 patients treated in cohorts A, B2, B4 and C, pleural effusions occurred in 7 with variable attributions to drug, leading to a protocol amendment mandating supportive care and corticosteroids for pleural effusions on study. Common toxicities included anemia, elevated liver enzymes, rash, fatigue, and nausea, generally Grade 1. In Cohort A, nivo Cmax, t1/2 and Clpvalues were 63.2±15.7 mg/mL, 10.7±1.8 d and 0.196±0.075 ml/h/kg, respectively. In the Phase II expansion cohorts, no objective responses were observed in OS or EWS. Conclusions: Nivo alone or with ipi at the doses tested is safe in pediatric patients with relapsed/refractory solid tumors. The pediatric RP2D of nivo is 3mg/kg alone or in combination with ipi 1mg/kg. Single agent nivo did not have antitumor activity in OS or EWS. Enrollment to other expansion cohorts with nivo or nivo/ipi is ongoing. Clinical trial information: NCT02304458.