Adjunct Therapy with T Regulatory Cells Decreases Inflammation and Preserves the Anti-Tumor Activity of CAR T Cells.

With greater accessibility and an increased number of patients being treated with CAR T cell therapy, real-world toxicity continues to remain a significant challenge to its widespread adoption. We have previously shown that allogeneic umbilical cord blood-derived (UCB) regulatory T cells (Tregs) can resolve inflammation and treat acute and immune-mediated lung injuries. Allogeneic, cryopreserved UCB Tregs have shown a clinical benefit in patients suffering from COVID-19 acute respiratory distress syndrome. The unique properties of UCB Treg cells include a lack of plasticity under inflammatory micro-environments, no requirement for HLA matching, a long shelf life of cryopreserved cells, and immediate product availability, which makes them attractive for treating acute inflammatory syndromes. Therefore, we hypothesized that adjunct therapy with UCB Tregs may resolve the undesirable inflammation responsible for CAR T cell therapy-associated toxicity. In in vitro analysis, no interference from the addition of UCB Tregs was observed on CD19 CAR T cells' ability to kill CD19 Raji cells at different CAR T: Raji cell ratios of 8:1 (80.4% vs. 81.5%); 4:1 (62.0% vs. 66.2%); 2:1 (50.1% vs. 54.7%); and 1:1 (35.4% vs. 44.1%). In the xenogeneic B-cell lymphoma model, multiple injections of UCB Tregs were administered 3 days after CD19 CAR T cell injection, and no detrimental effect of add-on Tregs was noted on the circulating CD8+ T effector cells. The distribution of CAR T cells in multiple organs remained unaffected by the addition of the UCB Tregs. Specifically, no difference in the overall tumor burden was detected between the UCB Treg + CAR T vs. CAR T alone recipients. No tumor was detected in the liver or bone marrow in CAR T cells + UCB Tregs recipients, with a notable corresponding decrease in multiple circulating inflammatory cytokines when compared to CART alone recipients. Here we show the proof of concept for adjunct therapy with UCB Tregs to mitigate the hyper-inflammatory state induced by CAR T cells without any interference in their on-target anti-tumor activity. Administration of UCB Tregs after CAR T cells allows sufficient time for their synapse formation with tumor cells and exerts cytotoxicity, such that the UCB Tregs are diverted to interact with the antigen-presenting cells at the site of inflammation. Such a differential distribution of cells would allow for a two-pronged strategy of a UCB Treg "cooling blanket" effect and lay the groundwork for clinical study.

Human Mesenchymal Stem Cell (hMSC) Donor Potency Selection for the "First in Cystic Fibrosis" Phase I Clinical Trial (CEASE-CF).

Human Mesenchymal Stem Cell (hMSC) immunotherapy has been shown to provide both anti-inflammatory and anti-microbial effectiveness in a variety of diseases. The clinical potency of hMSCs is based upon an initial direct hMSC effect on the pro-inflammatory and anti-microbial pathophysiology as well as sustained potency through orchestrating the host immunity to optimize the resolution of infection and tissue damage. Cystic fibrosis (CF) patients suffer from a lung disease characterized by excessive inflammation and chronic infection as well as a variety of other systemic anomalies associated with the consequences of abnormal cystic fibrosis transmembrane conductance regulator (CFTR) function. The application of hMSC immunotherapy to the CF clinical armamentarium is important even in the era of modulators when patients with an established disease still need anti-inflammatory and anti-microbial therapies. Additionally, people with CF mutations not addressed by current modulator resources need anti-inflammation and anti-infection management. Furthermore, hMSCs possess dynamic therapeutic properties, but the potency of their products is highly variable with respect to their anti-inflammatory and anti-microbial effects. Due to the variability of hMSC products, we utilized standardized in vitro and in vivo models to select hMSC donor preparations with the greatest potential for clinical efficacy. The models that were used recapitulate many of the pathophysiologic outcomes associated with CF. We applied this strategy in pursuit of identifying the optimal donor to utilize for the "First in CF" Phase I clinical trial of hMSCs as an immunotherapy and anti-microbial therapy for people with cystic fibrosis. The hMSCs screened in this study demonstrated significant diversity in antimicrobial and anti-inflammatory function using models which mimic some aspects of CF infection and inflammation. However, the variability in activity between in vitro potency and in vivo effectiveness continues to be refined. Future studies require and in-depth pursuit of hMSC molecular signatures that ultimately predict the capacity of hMSCs to function in the clinical setting.

Phase I study of intra-osseous co-transplantation of a single-unit cord blood and mesenchymal stromal cells with reduced intensity conditioning regimens.

Cord blood (CB) is a valuable graft source for patients undergoing allogeneic hematopoietic cell transplant (HCT) who lack human leukocyte antigen (HLA)-matched donors. However, single-unit CB-HCT is limited by the insufficient cell dose and slow engraftment. To overcome these limitations, we combined a single-unit CB with third-party healthy donors' bone marrow (BM) derived mesenchymal stromal cells (MSCs) to improve engraftment and injected intra-osseously (IO) to enhance homing. In this phase I clinical trial, six patients with high-risk hematologic malignancies were enrolled and received allogeneic HCT using reduced intensity conditioning regimens. The primary objective was to determine the engraftment rate at day 42. The median age of enrolled patients was 68 years, and only one patient was in complete remission at the time of HCT. The median CB total nucleated cell dose was 3.2x107/kg. No serious adverse events were reported. Two patients had early deaths due to persistent disease and multi-drug resistant bacterial infection, respectively. Of the remaining four evaluable patients, all had successful neutrophil engraftment in a median of 17.5 days. No grade 3 or higher acute graft-versus-host disease (GvHD) was observed, and only one patient developed moderate-extensive chronic GvHD. In conclusion, IO co-transplantation of a single-unit CB and MSCs was feasible and resulted in a reasonable engraftment rate in these very high-risk patients.

A Phase I Study to Determine the Maximum Tolerated Dose of ex Vivo Expanded Natural Killer Cells Derived from Unrelated, HLA-Disparate Adult Donors.

The administration of allogeneic natural killer (NK) cells following a lymphodepleting chemotherapy regimen is emerging as a well-tolerated therapeutic approach in the management of various malignancies. Contrary to the expected complications of allogeneic T cell therapy, there remains no evidence of graft-versus-host disease (GVHD) mediated by NK cells in numerous clinical trials. On the contrary, preclinical and clinical studies suggest that NK cells do not induce GVHD and in fact may prevent its development following allogeneic hematopoietic cell transplantation (HCT). In this study, we sought to determine the maximum tolerated dose of non-HLA-matched donor NK cells derived from peripheral blood and ex vivo expanded using a novel feeder cell platform. In a single-center Phase I clinical trial using a 3 × 3 design, 9 subjects each received 2 infusions of NK cells 2 weeks apart following a preparative regimen of cyclophosphamide (60 mg/kg i.v.) and fludarabine (25 mg/m2/day i.v for 5 days). No exogenous cytokines were administered. NK cells were administered at 3 dose levels: 1 × 107/kg, 2.5 × 107/kg, and 5 × 107/kg. Three subjects had myelodysplastic syndrome (MDS) or acute myelogenous leukemia (AML), and the other 6 subjects had colorectal carcinoma. Recipients were monitored over a 4-week period for GVHD as well as other adverse events and for persistence of donor NK cells in systemic circulation. Disease assessment was started at 28 days following the first NK cell infusion and continued until postinfusion day 100 or disease progression. In all 9 study subjects, there was no occurrence of GVHD and no dose-limiting toxicities that would warrant cohort expansion at any of the 3 planned cell dose levels. Low-level donor NK cell persistence was observed up to 4 weeks after the first NK cell infusion at all dose levels. The best observed response was a complete response with incomplete platelet recovery in a MDS subject who experienced disease relapse after prior allogeneic HCT. Other responses were stable disease in 1 subject with MDS and 2 subjects with colorectal cancer up to postinfusion day 100. This off-the-shelf, third-party NK cell product can be administered safely without inducing GVHD and exhibits in vivo persistence promoted by preparative lymphodepletion alone. The observed clinical responses could be enhanced by administration of exogenous cytokine support, as well as complementary approaches that promote NK cell function in the tumor microenvironment.

Optimization of Human Mesenchymal Stem Cells for Rheumatoid Arthritis: Implications for Improved Therapeutic Outcomes.

OBJECTIVE: Seropositive rheumatoid arthritis (RA) is a chronic autoimmune disease that is rarely "cured." Human mesenchymal stem cells (hMSCs) are known to reduce inflammation and restore immune homeostasis. However, methods for predicting therapeutic hMSC potency have not been established. The goal of these studies was to use and refine an ex vivo functional assay that determines potency of hMSCs and can then be validated in clinical trials as a potency measure of hMSCs used therapeutically to treat RA. METHODS: Allogeneic hMSCs were cytokine-stimulated, and a conditioned medium (CM) was harvested. The CM was tested for the potential to attenuate RA CD4+ T cell proliferation using suppression assays. Indoleamine 2, 3-dioxygenase (IDO) mRNA, and protein were quantified in hMSCs as a measure to compare hMSCs across (prior) studies. RESULTS: To mimic a proinflammatory environment that resembles that in RA, interleukin-1(IL1ß), tumor necrosis factor α (TNFα), and interferon γ (IFNγ) (alone or in combination) were used to precondition hMSCs. Treating hMSCs with a combination of these cytokines generated a CM "secretome" that suppressed T cell proliferation between 70 and 83%. Forty-eight hours of cytokine preconditioning hMSCs was required to maximize this effect. T cell suppression positively correlated with increases in hMSC cellular IDO mRNA and protein. CONCLUSION: By standardizing assays to measure hMSC effects, their potency on T cell suppression can be quantified. These studies demonstrate that hMSCs can be compared functionally to identify optimal preparation(s) for therapeutic use in RA and that the potency of hMSC-dependent T cell suppression may differ between hMSC donors. Clinical studies are warranted to validate the hypothesis that ex vivo potency in suppressing T cells will positively correlate with a reduction in RA disease activity and increase in immunological quiescence.

Multiple site place-of-care manufactured anti-CD19 CAR-T cells induce high remission rates in B-cell malignancy patients.

Chimeric antigen receptor (CAR) T cells targeting the CD19 antigen are effective in treating adults and children with B-cell malignancies. Place-of-care manufacturing may improve performance and accessibility by obviating the need to cryopreserve and transport cells to centralized facilities. Here we develop an anti-CD19 CAR (CAR19) comprised of the 4-1BB co-stimulatory and TNFRSF19 transmembrane domains, showing anti-tumor efficacy in an in vivo xenograft lymphoma model. CAR19 T cells are manufactured under current good manufacturing practices (cGMP) at two disparate clinical sites, Moscow (Russia) and Cleveland (USA). The CAR19 T-cells is used to treat patients with relapsed/refractory pediatric B-cell Acute Lymphocytic Leukemia (ALL; n = 31) or adult B-cell Lymphoma (NHL; n = 23) in two independently conducted phase I clinical trials with safety as the primary outcome (NCT03467256 and NCT03434769, respectively). Probability of measurable residual disease-negative remission was also a primary outcome in the ALL study. Secondary outcomes include complete remission (CR) rates, overall survival and median duration of response. CR rates are 89% (ALL) and 73% (NHL). After a median follow-up of 17 months, one-year survival rate of ALL complete responders is 79.2% (95%CI 64.5‒97.2%) and median duration of response is 10.2 months. For NHL complete responders one-year survival is 92.9%, and median duration of response has not been reached. Place-of-care manufacturing produces consistent CAR-T cell products at multiple sites that are effective for the treatment of patients with B-cell malignancies.

Prophylactic Tocilizumab Prior to Anti-CD19 CAR-T Cell Therapy for Non-Hodgkin Lymphoma.

Anti-CD19 chimeric antigen receptor T (CAR-T) cells have demonstrated activity against relapsed/refractory lymphomas. Cytokine release syndrome (CRS) and immune effector cell - associated neurotoxicity syndrome (ICANS) are well-known complications. Tocilizumab, a monoclonal antibody targeting the interleukin-6 (IL-6) receptor was administered 1 hour prior to infusion of anti-CD19 CAR-T cells with CD3ζ/4-1BB costimulatory signaling used to treat non-Hodgkin lymphoma patients. Relapsed/refractory lymphoma patients treated with anti-CD19 CAR-T cells were included in this analysis. Cytokine plasma levels were measured by electrochemiluminescence before lymphodepleting chemotherapy, prior to infusion and then on days 2, 4,6, and 14 days after treatment. Twenty patients were treated. Cell products included locally manufactured anti-CD19 CAR-T (n=18) and tisagenlecleucel (n=2). There were no adverse events attributed to tocilizumab. Ten patients had grade 1-2 CRS at a median of 4 (range 3-7) days. There were no cases of grade ≥3 CRS. Five patients had ICANS, grade 1 (n=4) and grade 4 (n=1). Laboratory studies obtained prior to lymphodepleting chemotherapy were comparable between patients with and without CRS, except for interleukin (IL)-15 plasma concentrations. patients with CRS had higher post-infusion ferritin and C reactive protein, with more marked increases in inflammatory cytokines, including IL-6, IL-15, IFN-γ, fractalkine and MCP-1. Fifteen patients (75%) achieved CR and 2 (10%), PR. One-year OS and PFS estimates were 83% and 73%. Prophylactic tocilizumab was associated with low CRS incidence and severity. There were no adverse events associated with tocilizumab, no increase in frequency or severity of ICANS and excellent disease control and overall survival.

Feasibility of mesenchymal stem cell culture expansion for a phase I clinical trial in multiple sclerosis.

BACKGROUND: Multiple sclerosis is an inflammatory, neurodegenerative disease of the central nervous system for which therapeutic mesenchymal stem cell transplantation is under study. Published experience of culture-expanding multiple sclerosis patients' mesenchymal stem cells for clinical trials is limited. OBJECTIVE: To determine the feasibility of culture-expanding multiple sclerosis patients' mesenchymal stem cells for clinical use. METHODS: In a phase I trial, autologous, bone marrow-derived mesenchymal stem cells were isolated from 25 trial participants with multiple sclerosis and eight matched controls, and culture-expanded to a target single dose of 1-2 × 106 cells/kg. Viability, cell product identity and sterility were assessed prior to infusion. Cytogenetic stability was assessed by single nucleotide polymorphism analysis of mesenchymal stem cells from 18 multiple sclerosis patients and five controls. RESULTS: One patient failed screening. Mesenchymal stem cell culture expansion was successful for 24 of 25 multiple sclerosis patients and six of eight controls. The target dose was achieved in 16-62 days, requiring two to three cell passages. Growth rate and culture success did not correlate with demographic or multiple sclerosis disease characteristics. Cytogenetic studies identified changes on one chromosome of one control (4.3%) after extended time in culture. CONCLUSION: Culture expansion of mesenchymal stem cells from multiple sclerosis patients as donors is feasible. However, culture time should be minimized for cell products designated for therapeutic administration.

Pilot trial of intravenous autologous culture-expanded mesenchymal stem cell transplantation in multiple sclerosis.

BACKGROUND: Mesenchymal stem cells (MSCs) exhibit immunomodulatory, tissue-protective, and repair-promoting properties in vitro and in animals. Clinical trials in several human conditions support the safety and efficacy of MSC transplantation. Published experience in multiple sclerosis (MS) is modest. OBJECTIVE: To assess feasibility, safety, and tolerability and explore efficacy of autologous MSC transplantation in MS. METHODS: Participants with relapsing-remitting multiple sclerosis (RRMS) or secondary progressive multiple sclerosis (SPMS), Expanded Disability Status Scale score 3.0-6.5, disease activity or progression in the prior 2 years, and optic nerve involvement were enrolled. Bone-marrow-derived MSCs were culture-expanded and then cryopreserved. After confirming fulfillment of release criteria, 1-2 × 106 MSCs/kg were thawed and administered IV. RESULTS: In all, 24 of 26 screened patients were infused: 16 women and 8 men, 10 RRMS and 14 SPMS, mean age 46.5, mean Expanded Disability Status Scale score 5.2, 25% with gadolinium-enhancing magnetic resonance imaging (MRI) lesions. Mean cell dosage (requiring 1-3 passages) was 1.9 × 106 MSCs/kg (range, 1.5-2.0) with post-thaw viability uniformly ⩾95%. Cell infusion was tolerated well without treatment-related severe or serious adverse events, or evidence of disease activation. CONCLUSION: Autologous MSC transplantation in MS appears feasible, safe, and well tolerated. Future trials to assess efficacy more definitively are warranted.

Comparison of 2 Carmustine-Containing Regimens in the Rituximab Era: Excellent Outcomes Even in Poor-Risk Patients.

High-dose chemotherapy followed by autologous hematopoietic cell transplantation (HCT) improves outcomes in relapsed lymphoma, but the relative efficacy of different preparative regimens is not well defined. We included patients undergoing autologous HCT using BEAM (carmustine, 300 mg/m(2), etoposide, cytarabine, and melphalan) or BEP (carmustine 600 mg/m(2), etoposide, and cisplatin) between January 2004 and December 2013; 65 patients received BEP and 64 patients BEAM. Both cohorts were similar for advanced-stage disease, extranodal and bulky disease, and prior therapies. Median neutrophil and platelet engraftment was 10 and 20 days for both regimens, respectively. Febrile neutropenia, serum creatinine concentration increase, and electrolyte abnormalities were more frequent with BEP. Incidence of carmustine pneumonitis was not higher with BEP, likely the result of corticosteroid prophylaxis, although 2 cases of fatal pneumonitis were observed after BEP. One-year nonrelapse mortality was 6.8% after BEP and 0% after BEAM (P = .379). After a median follow-up of 39.4 months (range, 1 to 128), 4-year rates of overall survival (OS) after BEP and BEAM were 80.4% and 72.3%, respectively (P = .611). Diffuse large B cell lymphoma patients transplanted after early relapse post-rituximab-based first-line therapy presented 3-year rates of OS and progression-free survival (PFS) of 73.8% and 65%, respectively. There were no statistically significant differences in the OS and PFS of follicular lymphoma, mantle cell lymphoma, or Hodgkin lymphoma. BEP is a valid alternative to BEAM in autologous HCT. Although associated with more renal and electrolytic toxicities, BEP results in similar disease control and long-term survival as BEAM. Prospective studies are needed to confirm whether intensification of conditioning regimens for autologous HCT can improve disease control in high-risk relapsed lymphoma patients.