Steven D. Hartman

Purpose Therapies with novel mechanisms of action are needed for multiple myeloma (MM). T cells can be genetically modified to express chimeric antigen receptors (CARs), which are artificial proteins that target T cells to antigens. B-cell maturation antigen (BCMA) is expressed by normal and malignant plasma cells but not normal essential cells. We conducted the first-in-humans clinical trial, to our knowledge, of T cells expressing a CAR targeting BCMA (CAR-BCMA). Patients and Methods Sixteen patients received 9 × 10 6 CAR-BCMA T cells/kg at the highest dose level of the trial; we are reporting results of these 16 patients. The patients had a median of 9.5 prior lines of MM therapy. Sixty-three percent of patients had MM refractory to the last treatment regimen before protocol enrollment. T cells were transduced with a γ-retroviral vector encoding CAR-BCMA. Patients received CAR-BCMA T cells after a conditioning chemotherapy regimen of cyclophosphamide and fludarabine. Results The overall response rate was 81%, with 63% very good partial response or complete response. Median event-free survival was 31 weeks. Responses included eradication of extensive bone marrow myeloma and resolution of soft-tissue plasmacytomas. All 11 patients who obtained an anti-MM response of partial response or better and had MM evaluable for minimal residual disease obtained bone marrow minimal residual disease–negative status. High peak blood CAR + cell levels were associated with anti-MM responses. Cytokine-release syndrome toxicities were severe in some cases but were reversible. Blood CAR-BCMA T cells were predominantly highly differentiated CD8 + T cells 6 to 9 days after infusion. BCMA antigen loss from MM was observed. Conclusion CAR-BCMA T cells had substantial activity against heavily treated relapsed/refractory MM. Our results should encourage additional development of CAR T-cell therapies for MM.

Abstract Anti-CD19 chimeric antigen receptor (CAR) T cells have powerful activity against B-cell lymphoma, but improvement is clearly needed. Toxicity, including cytokine-release syndrome (CRS) and neurologic toxicity, occurs after anti-CD19 CAR T cell infusions. Most CAR T-cell toxicity is caused, either directly or indirectly, by cytokines or other proteins that are secreted from CAR T cells. The structure of a CAR is an extracellular antigen-recognition domain connected by hinge and transmembrane (TM) domains to intracellular T-cell signaling moieties. In vitro, T cells expressing CARs with hinge and TM domains from the CD8-alpha molecule released significantly lower levels of cytokines compared with T cells expressing CARs with hinge and TM domains from CD28; however, T cells expressing CARs with hinge and TM domains from CD8-alpha retained sufficient functional capability to eradicate tumors from mice (Alabanza et al. Molecular Therapy. 2017. 25(11) 2452). To reduce cytokine production with a goal of reducing clinical toxicity, we incorporated CD8-alpha hinge and TM domains into an anti-CD19 CAR. The CAR also had a human antigen-recognition domain, a CD28 costimulatory domain, and a CD3-zeta domain. This CAR was designated Hu19-CD828Z and was encoded by a lentiviral vector. Hu19-CD828Z was different from the FMC63-28Z CAR that we used in prior studies. FMC63-28Z had hinge and TM domains from CD28 along with a CD28 costimulatory domain, a CD3-zeta domain, and murine-derived antigen-recognition domains. Twenty patients with B-cell lymphoma were treated on a phase I dose-escalation clinical trial of Hu19-CD828Z T cells (Table). Patients received low-dose cyclophosphamide and fludarabine daily for 3 days on days -5 to -3. Two days later, on day 0, CAR T cells were infused. The overall response rate (ORR) after 1st treatments with Hu19-CD828Z T cells was 70%, and the complete response (CR) rate 55%; the 6-month event-free survival was 55%. The anti-lymphoma activity of Hu19-CD828Z T cells in the current trial was comparable to the anti-lymphoma activity of FMC63-28Z T cells in a similar prior trial that also enrolled patients with advanced B-cell lymphoma. In the prior trial, we observed a 73% ORR, a 55% CR rate, and a 6-month event-free survival of 64% in 22 patients treated with FMC63-28Z T cells (Kochenderfer et al. Journ. Clin. Oncology. 2017 35(16) 1803). In our previous clinical trial of FMC63-28Z T cells, the rate of Grade 3 or 4 neurologic toxicity among 22 patients treated was 55%. Strikingly, in our trial of Hu19-CD828Z T cells, the rate of Grade 3 or 4 neurologic toxicity was only 5% (1/20 patients). In addition, the rate of Grade 2 or greater neurologic toxicity with FMC63-28Z T cells was 77.3% while the rate of Grade 2 or greater neurologic toxicity with Hu19-CD828Z T cells was 15%. To explore the mechanism for the difference in neurologic toxicity in patients receiving FMC63-28Z T cells versus Hu19-CD828Z T cells, we assessed serum levels of 41 proteins in patients treated with these CAR T-cells. This comparison is valid because the same Luminex methodology was used for the serum protein analysis for both trials, and controls of known amounts of each protein were assayed to ensure that protein levels were comparable on the different trials. Lower levels of several serum proteins that might be important in CAR toxicity were found in patients treated with Hu19-CD828Z T cells versus patients treated with FMC63-28Z T cells: Granzyme A (P<0.001), Granzyme B (P<0.001), interferon gamma (P=0.011), interleukin (IL)-15 (P=0.007), IL-2 (P=0.0034), and macrophage inflammatory protein-1A (P<0.001). Median peak patient blood CAR+ cell levels were 44 cells/µL for Hu19-CD828Z and 46.5 cells/µL for FMC63-28Z (P=not significant). We hypothesize that lower levels of potentially neurotoxic proteins in patients receiving Hu19-CD828Z T cells versus FMC63-28Z T cells led to a lower frequency of neurologic toxicity in patients receiving Hu19-CD828Z T cells. The lower levels of immunologically active proteins found in the serum of patients receiving Hu19-CD828Z T cells compared with patients receiving FMC63-28Z T cells is consistent with our in vitro experiments showing lower cytokine production by T cells expressing CARs with CD8 hinge and TM domains versus CD28 hinge and TM domains. Altering CAR hinge and TM domains can affect CAR T-cell function and is a promising approach to improve the efficacy to toxicity ratio of CAR T-cells. Disclosures Rossi: KITE: Employment. Shen:Kite, a Gilead Company: Employment. Xue:Kite, a Gilead Company: Employment. Bot:KITE: Employment. Rosenberg:Kite, a Gilead Company: Research Funding. Kochenderfer:Kite a Gilead Company: Patents & Royalties: CAR technology, Research Funding; Celgene: Research Funding.

3052 Background: T cells expressing chimeric antigen receptors (CARs) targeting CD19 have powerful activity against B-cell lymphoma. A limitation to CAR T-cell therapy for lymphoma is occurrence of toxicities, especially neurologic toxicities. Methods: We designed an anti-CD19 CAR with fully human variable regions (Hu19CAR). This CAR has CD8α hinge and transmembrane domains and a CD28 costimulatory domain; T cells expressing this CAR release relatively low levels of cytokines. A phase I dose-escalation trial was conducted to investigate the safety of Hu19CAR T cells and to assess efficacy for patients with previously treated B-cell lymphoma. Patients received cyclophosphamide and fludarabine chemotherapy to enhance CAR T-cell activity. Two days after the completion of chemotherapy, Hu19CAR T cells were infused. Results: Twenty patients have received Hu19CAR T-cell infusions. Of these patients, 75% had lymphoma that was chemotherapy-refractory or relapsed after autologous stem cell transplant. Patients received a median of 4 prior lines of therapy. The overall response rate is 75%, with 55% complete remissions (CRs). CRs were observed in patients with chemotherapy-refractory lymphomas and in patients with double-hit diffuse large B-cell lymphoma. Durations of response currently range from 1 to 17 months. Forty percent of patients are in ongoing remissions. Only one patient experienced greater than Grade 2 neurotoxicity (5%), which is a neurotoxicity rate lower than that of many anti-CD19 CAR trials. This patient had Grade 4 neurotoxicity which reversed in less than 24 hours with corticosteroid therapy. Three patients had Grade 3 cytokine release syndrome (CRS), and 1 patient had Grade 4 CRS; all other patients had Grade 2 or lower CRS. CRS and neurotoxicities resolved completely in all patients. Loss of CD19 expression by lymphoma cells was observed in 4 of the 8 patients who underwent biopsies of recurrent or residual lymphoma after Hu19CAR T-cell infusions. CAR T cells were detected in the blood of all patients at levels ranging from 4-2216 cells/µL. Conclusions: Hu19CAR T cells have substantial activity against advanced lymphoma with a low rate of neurotoxicity. Clinical trial information: NCT02659943.

Background: Data regarding racial differences in patients with hypertrophic cardiomyopathy (HCM) is sparse. We hypothesized that Hispanic-Latino (HL), Non-Hispanic (NH), and African-American (AA) race impacts the clinical presentation of HCM. Methods: A total of 641 HCM patients (HL = 294, NH = 274, AA = 73) were identified retrospectively from our institutional registry between 2005–2021. Clinical characteristics, echocardiographic indices, and outcomes were assessed using analysis of variance, Kruskal-Wallis, and multivariate linear regression statistical analyses, with Dunn-Bonferroni and Tukey test applied in post-hoc pairwise assessments. Results: The HL and NH patients were older compared with AA (69.2 ± 14.7 vs 67.9 ± 15.3 vs 59.4 ± 15.8 years; p < 0.001). The HL group had higher prevalence of females compared with NH (62 vs 47%; p = 0.002), and more moderate-severe mitral regurgitation (35 vs 23 vs 12% p < 0.001) and a higher E/e’ ratio (16.4 ± 8.1 vs 14.9 ± 6.6 vs 13.3 ± 4.5; p = 0.002) when compared with NH and AA. Multivariate linear regression analysis revealed HL ethnicity (β = 0.1) was associated with worse New York Heart Association (NYHA) class independent from moderate-severe mitral regurgitation (β = 0.2), chronic obstructive pulmonary disease (β = 0.17), female gender (β = 0.13), coronary artery disease (β = 0.12), atrial fibrillation (β = 0.11), peak trans-mitral E-wave velocity (β = 0.11), left ventricular mass index (β = 0.1), and reverse septal curve morphology (β = 0.1) (model, r = 0.5, p < 0.001). At 2.5-year median follow-up, all-cause mortality (8%) and composite complications (33%) were similar across the cohort. Conclusions: HCM patients of HL race have worse heart failure symptoms when compared with NH and AA, with severity independent of cardiovascular co-morbidities.