Nonpathogenic E. coli engineered to surface display cytokines as a new platform for immunotherapy

Given the safety, tumor tropism, and ease of genetic manipulation in non-pathogenic Escherichia coli (E. coli), we designed a novel approach to deliver biologics to overcome poor trafficking and exhaustion of immune cells in the tumor microenvironment, via the surface display of key immune-activating cytokines on the outer membrane of E. coli K-12 DH5α. Bacteria expressing murine decoy-resistant IL18 mutein (DR18) induced robust CD8+ T and NK cell-dependent immune responses leading to dramatic tumor control, extending survival, and curing a significant proportion of immune-competent mice with colorectal carcinoma and melanoma. The engineered bacteria demonstrated tumor tropism, while the abscopal and recall responses suggested epitope spreading and induction of immunologic memory. E. coli K-12 DH5α engineered to display human DR18 potently activated mesothelin-targeting CAR NK cells and safely enhanced their trafficking into the tumors, leading to improved control and survival in xenograft mice bearing mesothelioma tumor cells, otherwise resistant to NK cells. Gene expression analysis of the bacteria-primed CAR NK cells showed enhanced TNFα signaling via NFkB and upregulation of multiple activation markers. Our novel live bacteria-based immunotherapeutic platform safely and effectively induces potent anti-tumor responses in otherwise hard-to-treat solid tumors, motivating further evaluation of this approach in the clinic.

Genetic Manipulation Approaches to Enhance the Clinical Application of NK Cell-Based Immunotherapy

Natural killer (NK) cells are a subset of cytotoxic lymphocytes within the innate immune system. While they are naturally cytotoxic, genetic modifications can enhance their tumor-targeting capability, cytotoxicity, persistence, tumor infiltration, and prevent exhaustion. These improvements hold the potential to make NK-cell-based immunotherapies more effective in clinical applications. Currently, several viral and non-viral technologies are used to genetically modify NK cells. For nucleic acid delivery, non-viral methods such as electroporation, lipid nanoparticles, lipofection, and DNA transposons have gained popularity in recent years. On the other hand, viral methods including lentivirus, gamma retrovirus, and adeno-associated virus, remain widely used for gene delivery. Furthermore, gene editing techniques such as clustered regularly interspaced short-palindromic repeats-based, zinc finger nucleases, and transcription activator-like effector nucleases are the pivotal methodologies in this field. This review aims to provide a comprehensive overview of chimeric antigen receptor (CAR) arming strategies and discuss key gene editing techniques. These approaches collectively aim to enhance NK cell/NK cell CAR-based immunotherapies for clinical translation.

Differentiation of BCMA-specific induced pluripotent stem cells into rejuvenated CD8αβ+ T cells targeting multiple myeloma

ABSTRACT

A major hurdle in adoptive T-cell therapy is cell exhaustion and failure to maintain antitumor responses. Here, we introduce an induced pluripotent stem cell (iPSC) strategy for reprogramming and revitalizing precursor exhausted B-cell maturation antigen (BCMA)-specific T cells to effectively target multiple myeloma (MM). Heteroclitic BCMA72-80 (YLMFLLRKI)-specific CD8+ memory cytotoxic T lymphocytes (CTL) were epigenetically reprogrammed to a pluripotent state, developed into hematopoietic progenitor cells (CD34+ CD43+/CD14- CD235a-), differentiated into the T-cell lineage and evaluated for their polyfunctional activities against MM. The final T-cell products demonstrated (1) mature CD8αβ+ memory phenotype, (2) high expression of activation or costimulatory molecules (CD38, CD28, and 41BB), (3) no expression of immune checkpoint and senescence markers (CTLA4, PD1, LAG3, and TIM3; CD57), and (4) robust proliferation and polyfunctional immune responses to MM. The BCMA-specific iPSC-T cells possessed a single T-cell receptor clonotype with cognate BCMA peptide recognition and specificity for targeting MM. RNA sequencing analyses revealed distinct genome-wide shifts and a distinctive transcriptional profile in selected iPSC clones, which can develop CD8αβ+ memory T cells. This includes a repertoire of gene regulators promoting T-cell lineage development, memory CTL activation, and immune response regulation (LCK, IL7R, 4-1BB, TRAIL, GZMB, FOXF1, and ITGA1). This study highlights the potential application of iPSC technology to an adaptive T-cell therapy protocol and identifies specific transcriptional patterns that could serve as a biomarker for selection of suitable iPSC clones for the successful development of antigen-specific CD8αβ+ memory T cells to improve the outcome in patients with MM.

Building a Better Defense: Expanding and Improving Natural Killer Cells for Adoptive Cell Therapy

Natural killer (NK) cells have gained attention as a promising adoptive cell therapy platform for their potential to improve cancer treatments. NK cells offer distinct advantages over T-cells, including major histocompatibility complex class I (MHC-I)-independent tumor recognition and low risk of toxicity, even in an allogeneic setting. Despite this tremendous potential, challenges persist, such as limited in vivo persistence, reduced tumor infiltration, and low absolute NK cell numbers. This review outlines several strategies aiming to overcome these challenges. The developed strategies include optimizing NK cell expansion methods and improving NK cell antitumor responses by cytokine stimulation and genetic manipulations. Using K562 cells expressing membrane IL-15 or IL-21 with or without additional activating ligands like 4-1BBL allows "massive" NK cell expansion and makes multiple cell dosing and "off-the-shelf" efforts feasible. Further improvements in NK cell function can be reached by inducing memory-like NK cells, developing chimeric antigen receptor (CAR)-NK cells, or isolating NK-cell-based tumor-infiltrating lymphocytes (TILs). Memory-like NK cells demonstrate higher in vivo persistence and cytotoxicity, with early clinical trials demonstrating safety and promising efficacy. Recent trials using CAR-NK cells have also demonstrated a lack of any major toxicity, including cytokine release syndrome, and, yet, promising clinical activity. Recent data support that the presence of TIL-NK cells is associated with improved overall patient survival in different types of solid tumors such as head and neck, colorectal, breast, and gastric carcinomas, among the most significant. In conclusion, this review presents insights into the diverse strategies available for NK cell expansion, including the roles played by various cytokines, feeder cells, and culture material in influencing the activation phenotype, telomere length, and cytotoxic potential of expanded NK cells. Notably, genetically modified K562 cells have demonstrated significant efficacy in promoting NK cell expansion. Furthermore, culturing NK cells with IL-2 and IL-15 has been shown to improve expansion rates, while the presence of IL-12 and IL-21 has been linked to enhanced cytotoxic function. Overall, this review provides an overview of NK cell expansion methodologies, highlighting the current landscape of clinical trials and the key advancements to enhance NK-cell-based adoptive cell therapy.

Prophylactic maintenance with venetoclax/azacitidine after reduced-intensity conditioning allogeneic transplant for high-risk MDS and AML

ABSTRACT

We conducted a phase 1 trial assessing safety and efficacy of prophylactic maintenance therapy with venetoclax and azacitidine (Ven/Aza) for patients with high-risk myelodysplastic syndromes (MDS)/acute myeloid leukemia (AML) undergoing reduced intensity allogeneic stem cell transplantation (allo-SCT) after Ven and fludarabine/busulfan conditioning (Ven/FluBu2 allo-SCT) with tacrolimus and methotrexate as graft-versus-host disease (GVHD) prophylaxis. Among 27 patients who underwent Ven/FluBu2 allo-SCT (55.6% with prior Ven exposure, and 96% with positive molecular measurable residual disease), 22 received maintenance therapy with Aza 36 mg/m2 intravenously on days 1 to 5, and Ven 400 mg by mouth on days 1 to 14 per assigned dose schedule/level (42-day cycles × 8, or 28-day cycles × 12). During maintenance, the most common grade 3-4 adverse events were leukopenia, neutropenia, and thrombocytopenia, which were transient and manageable. Infections were uncommon (n = 4, all grade 1-2). The 1-year and 2-year moderate/severe chronic GVHD rates were 4% (95% confidence interval [CI], 0.3%-18%) and 22% (95% CI, 9%-40%), respectively. After a median follow-up of 25 months among survivors, the median overall survival (OS) was not reached. Among the 22 patients who received Ven/Aza maintenance, the 2-year OS, progression-free survival, nonrelapse mortality, and cumulative incidence of relapse rates were 67% (95% CI, 43%-83%), 59% (95% CI, 36%-76%), 0%, and 41% (95% CI, 20%-61%), respectively. Immune monitoring demonstrated no significant impact on T-cell expansion but identified reduced B-cell expansion compared with controls. This study demonstrates prophylactic Ven/Aza maintenance can be safely administered for patients with high-risk MDS/AML, but a randomized study is required to properly assess any potential benefit. This trial was registered at www.clinicaltrials.gov as #NCT03613532.

Systematic evaluation of donor-KIR/recipient-HLA interactions in HLA-matched hematopoietic cell transplantation for AML

ABSTRACT

In acute myeloid leukemia (AML), donor natural killer cell killer immunoglobulin-like receptors (KIR) and recipient HLA interactions may contribute to the graft-versus-leukemia effect of allogeneic hematopoietic cell transplantation (HCT). Analyses of individual KIR/HLA interactions, however, have yielded conflicting findings, and their importance in the HLA-matched unrelated donor (MUD) setting remains controversial. We systematically studied outcomes of individual donor-KIR/recipient-HLA interactions for HCT outcomes and empirically evaluated prevalent KIR genotypes for clinical benefit. Adult patients with AML (n = 2025) who received HCT with MUD grafts in complete remission reported to the Center for International Blood and Marrow Transplantation were evaluated. Only the donor-2DL2+/recipient-HLA-C1+ pair was associated with reduced relapse (hazard ratio [HR], 0.79; 95% confidence interval [CI], 0.67-0.93; P = .006) compared with donor-2DL2-/recipient-HLA-C1+ pair. However, no association was found when comparing HLA-C groups among KIR-2DL2+-graft recipients. We identified 9 prevalent donor KIR genotypes in our cohort and screened them for association with relapse risk. Genotype 5 (G5) in all recipients and G3 in Bw4+ recipients were associated with decreased relapse risk (HR, 0.52; 95% CI, 0.35-0.78; P = .002; and HR, 0.32; 95% CI, 0.14-0.72; P = .006; respectively) and G2 (HR 1.63, 95% CI, 1.15-2.29; P = .005) with increased relapse risk in C1-homozygous recipients, compared with other patients with the same ligand. However, we could not validate these findings in an external data set of 796 AML transplants from the German transplantation registry. Neither a systematic evaluation of known HLA-KIR interactions nor an empiric assessment of prevalent KIR genotypes demonstrated clinically actionable associations; therefore, these data do not support these KIR-driven strategies for MUD selection in AML.

Opportunistic Infections in Patients Receiving Post-Transplantation Cyclophosphamide: Impact of Haploidentical versus Unrelated Donor Allograft

Post-transplantation cyclophosphamide (PTCy) is an effective strategy for graft-versus-host disease (GVHD) prophylaxis and is the standard of care for haploidentical hematopoietic cell transplantation (HCT). It is increasingly used for matched and mismatched unrelated donor (MUD/MMUD) HCT, but infections remain a concern. The objective of this study was to evaluate the characteristics and risk factors for infections in haploidentical and unrelated donor HCT recipients treated with PTCy-based GVHD prophylaxis. This single-center retrospective study examined 354 consecutive adults undergoing HCT with PTCy-based GVHD prophylaxis (161 MUD/MMUD; 193 haploidentical) between 2015 and 2022. Opportunistic infections (OIs), including cytomegalovirus (CMV), adenovirus (AdV), Epstein-Barr virus (EBV), and invasive fungal disease (IFD), were assessed from day 0 through day +365. The 1-year cumulative incidence functions of OIs and nonrelapse mortality (NRM) were calculated using dates of relapse and repeat HCT as competing risks. Secondary analysis evaluated risk factors for OIs and NRM using univariate and multivariable Cox regression models. Haploidentical HCT recipients had an increased risk of OIs compared to unrelated donor allograft recipients (39% for haploidentical versus 25% for MUD/MMUD; hazard ratio [HR], 1.70; 95% confidence interval [CI], 1.16 to 2.49; P = .006). On multivariable analysis, haploidentical donor (HR, 1.50; 95% CI, 1.01 to 2.23; P = .046), prior HCT (HR, 1.99; 95% CI, 1.29 to 3.09; P = .002), and diagnosis of aGVHD (HR, 1.47; 95% CI, 1.02 to 2.14; P = .041) were associated with increased risk of OIs. NRM within the first year was not significantly different between the 2 cohorts (HR, 1.11; 95% CI, .64 to 1.93; P = .70). Overall, haploidentical donor was a significant risk factor for OIs in patients receiving PTCy, although 1-year NRM was not different between haploidentical HCT and MUD/MMUD HCT recipients. CMV and AdV infections were significantly increased among haploidentical HCT recipients, whereas the incidences of EBV infection and IFD were similar in the 2 cohorts. Our findings may have implications for infection monitoring and prophylaxis in the setting of PTCy, particularly in haploidentical HCT recipients.

Single-cell functional genomics reveals determinants of sensitivity and resistance to natural killer cells in blood cancers

Cancer cells can evade natural killer (NK) cell activity, thereby limiting anti-tumor immunity. To reveal genetic determinants of susceptibility to NK cell activity, we examined interacting NK cells and blood cancer cells using single-cell and genome-scale functional genomics screens. Interaction of NK and cancer cells induced distinct activation and type I interferon (IFN) states in both cell types depending on the cancer cell lineage and molecular phenotype, ranging from more sensitive myeloid to less sensitive B-lymphoid cancers. CRISPR screens in cancer cells uncovered genes regulating sensitivity and resistance to NK cell-mediated killing, including adhesion-related glycoproteins, protein fucosylation genes, and transcriptional regulators, in addition to confirming the importance of antigen presentation and death receptor signaling pathways. CRISPR screens with a single-cell transcriptomic readout provided insight into underlying mechanisms, including regulation of IFN-γ signaling in cancer cells and NK cell activation states. Our findings highlight the diversity of mechanisms influencing NK cell susceptibility across different cancers and provide a resource for NK cell-based therapies.

Phase I-II Trial of Early Azacitidine after Matched Unrelated Donor Hematopoietic Cell Transplantation

Graft-versus-host disease (GVHD) is a major complication after allogeneic hematopoietic cell transplantation (allo-HCT). The hypomethylating agent azacitidine (AZA) has been shown to be effective in preclinical and clinical studies for the prevention of acute GVHD (aGVHD). We sought to determine the maximum tolerated dose (MTD) of AZA when given on days 1 to 5 of a 28-day cycle for 4 cycles, starting on day +7 after allo-HCT, as well as its impact on aGVHD and chronic GVHD (cGVHD), relapse, and overall survival (OS) in patients undergoing matched unrelated donor allo-HCT. This study was a single-arm, single-center, open-label phase I-II study with a total of 15 and 38 patients enrolled in the phase I and II portions of the trial, respectively. A standard 3+3 study design was used in phase I, and all patients in phase II received AZA at the MTD determined in phase I. The MTD of AZA starting at day +7 post-transplantation was 45 mg/m2. Phase II of the study was halted after enrolling 38 of the planned 46 patients following an interim analysis that suggested futility. Overall, AZA at 45 mg/m2 exhibited a side effect profile consistent with prior reports and had a minimal impact on engraftment. The cumulative incidence of clinically significant aGVHD by day +180 was 39.9% (95% confidence interval [CI], 22% to 53.7%). The incidence of all-grade cGVHD was 61.4% (95% CI, 40.3% to 75%). At 1 year, OS was 73.7% (95% CI, 60.9% to 89.1%), and the disease relapse rate was 11.4% (95% CI, .2% to 21.3%). Our results suggest that early post-allo-HCT AZA has limited efficacy in preventing aGVHD and cGVHD but could have a beneficial effect in preventing disease relapse.

Preventing NK cell activation in the damaged liver induced by cabozantinib/PD-1 blockade increases survival in hepatocellular carcinoma models

The addition of anti-VEGF antibody treatment to immune checkpoint blockade (ICB) has increased the efficacy of immunotherapy in advanced hepatocellular carcinoma (HCC). Despite an initial promise, adding multitargeted kinase inhibitors of VEGFR with ICB has failed to increase survival in HCC. To reveal the mechanisms underlying treatment failure, we studied the effects of cabozantinib/ICB using orthotopic murine HCC models with or without liver damage. We monitored tumor growth and liver function, recorded survival outcomes, and performed immune profiling studies for intra-tumoral and surrounding liver. Cabozantinib/ICB treatment led to tumor regression and significantly improved survival in mice with normal livers. However, consistent with the clinical findings, combination therapy failed to show survival benefits despite similar tumor control when tested in the same models but in mice with liver fibrosis. Moreover, preclinical and clinical data converged, showing that activating immune responses by cabozantinib/ICB treatment induced hepatoxicity. Immune profiling revealed that combination therapy effectively reprogrammed the tumor immune microenvironment and increased NK cell infiltration and activation in the damaged liver tissue. Surprisingly, systemic depletion of NK reduced hepatotoxicity elicited by the combination therapy without compromising its anti-cancer effect, and significantly enhanced the survival benefit even in mice with HCC and underlying liver fibrosis. These findings demonstrate that preventing NK activation allowed for maintaining a favorable therapeutic ratio when combining ICB with cabozantinib in advanced HCC models.

Posttransplant cyclophosphamide vs tacrolimus-based GVHD prophylaxis: lower incidence of relapse and chronic GVHD

The ability of posttransplant cyclophosphamide (PTCY) to facilitate haploidentical transplantation has spurred interest in whether PTCY can improve clinical outcomes in patients with HLA-matched unrelated donors undergoing peripheral blood stem cell transplantation (PBSCT). We investigated our institutional experience using PTCY-based graft-versus-host disease (GVHD) prophylaxis compared with conventional tacrolimus-based regimens. We compared overall survival, progression-free survival (PFS), relapse, nonrelapse mortality, and acute and chronic GVHD in 107 adult patients receiving a PTCY-based regimen vs 463 patients receiving tacrolimus-based regimens for GVHD prophylaxis. The 2 cohorts were well balanced for baseline characteristics except that more patients in the PTCY cohort having received 7-of-8-matched PBSCT. There was no difference in acute GVHD. All-grade chronic GVHD and moderate-to-severe chronic GVHD were substantially reduced in patients receiving PTCY compared with in those receiving tacrolimus-based regimens (2-year moderate-to-severe chronic GVHD: 12% vs 36%; P < .0001). Recipients of PTCY-based regimens also had a lower incidence of relapse compared with recipients of tacrolimus-based regimens (25% vs 34% at 2-years; P = .027), primarily in patients who received reduced intensity conditioning. This led to improved PFS in the PTCY cohort (64% vs 54% at 2 years; P = .02). In multivariable analysis, the hazard ratio was 0.59 (P = .015) for PFS and the subdistribution hazard ratio was 0.27 (P < .0001) for moderate-to-severe chronic GVHD and 0.59 (P = .015) for relapse. Our results suggest that PTCY prophylaxis is associated with lower rates of relapse and chronic GVHD in patients who receive HLA-matched unrelated donor PBSCT.

Profiling of Natural Killer Interactions With Cancer Cells Using Mass Cytometry

We developed a comprehensive method for functional assessment of the changes in immune populations and killing activity of peripheral blood mononuclear cells after cocultures with cancer cells using mass cytometry. In this study, a 43-marker mass cytometry panel was applied to a coculture of immune cells from healthy donors' peripheral blood mononuclear cells with diverse cancer cell lines. DNA content combined with classical CD45 surface staining was used as gating parameters for cocultures of immune cells (CD45high/DNAlow) with hematological (CD45low/DNAhigh) and solid cancer cell lines (CD45neg/DNAhigh). This strategy allows for universal discrimination of cancer cells from immune populations without the need for a specific cancer cell marker and simultaneous assessment of phenotypical changes in both populations. The use of mass cytometry allows for simultaneous detection of changes in natural killer, natural killer T cell, and T cell phenotypes and degranulation of immune populations upon target recognition, analysis of target cells for cytotoxic protein granzyme B content, and cancer cell death. These findings have broad applicability in research and clinical settings with the aim to phenotype and assess functional changes following not only NK-cancer cell interactions but also the effect of those interactions on other immune populations.

Cytokine release syndrome in haploidentical stem cell transplant may impact T-cell recovery and relapse

Cytokine release syndrome (CRS) following haploidentical hematopoietic cell transplantation (HCT) resembles the CRS after chimeric antigen receptor (CAR)-T therapy. We conducted this single-center retrospective study evaluating the association of post-haploidentical HCT CRS with clinical outcomes and immune reconstitution. One hundred sixty-nine patients who underwent haploidentical HCT between 2011 and 2020 were identified. Of these, 98 patients (58%) developed CRS after HCT. CRS was diagnosed based on the presence of fever within the first 5 days after HCT without evidence of infection or infusion reaction, and graded according to established criteria. The development of post-haploidentical HCT CRS was associated with a lower incidence of disease relapse (p=0.024) but with an increased risk of chronic GVHD (p=0.01). The association of CRS with a lower incidence of relapse was not confounded by graft source or disease diagnosis. Neither CD34 nor TNC dose was associated with CRS independently of graft type. In patients developing CRS, CD4+ Treg (p<0.0005), CD4+ Tcon (p<0.005) and CD8+ T-cells (p<0.005) were increased at 1 month following HCT compared to those who did not develop CRS, but not at later time points. The increase in CD4+ regulatory T cells at 1 month post HCT was most notable among patients with CRS who received a bone marrow graft (p<0.005). The development of post haploidentical HCT CRS is associated with a reduced incidence of disease relapse and with a transient effect on post HCT immune reconstitution of T cells and their subsets. Validation of these observations in a multicenter cohort is required.

Clinical Features of AKI in the Early Post-Transplant Period Following Reduced Intensity Allogeneic Hematopoietic Stem Cell Transplantation

BACKGROUND

Allogeneic hematopoietic stem cell transplant (HCT) is a potentially curative therapy for patients with hematologic malignancies but is associated with acute kidney injury (AKI). Few studies have examined risk factors for AKI at engraftment, or its relationship with clinical outcomes.

OBJECTIVE

The objective of this study was to examine the incidence and risk factors for peri-engraftment AKI, as well as the association between AKI and overall survival and non-relapse mortality.

METHODS

We conducted a retrospective analysis of adult patients receiving reduced intensity conditioning (RIC) allogeneic HCT at the Dana-Farber Cancer Institute between 2012 and 2019. Peri-engraftment (day 0 to day 30) AKI incidence and severity was defined using modified Kidney Disease: Improving Global Outcomes criteria. Factors associated with peri-engraftment AKI risk were examined using Cox regression analysis. The impact of peri-engraftment AKI on overall survival and non-relapse mortality (defined as death without recurrent disease after HCT), was evaluated using Cox regression and Fine and Gray's competing risk model, respectively. Kidney recovery, defined as a return of serum creatinine within 25% of baseline or liberation from kidney replacement therapy (KRT), was examined at day 90 in relation to HCT.

RESULTS

Peri-engraftment AKI occurred in 330 of 987 patients (33.4%) at a median of 13 days [IQR 4-30] post-transplant. Factors associated with a higher multivariable-adjusted risk of AKI were supratherapeutic rapamycin (HR: 1.56, 95% CI: 1.20-2.03; p<0.001), fludarabine/melphalan conditioning (HR: 1.35, 95% CI: 1.01-1.81; p=0.05; compared to fludarabine/busulfan and fludarabine, cyclophosphamide, total body irradiation), HCT-Comorbidity Index ≥4 (HR: 1.43, 95% CI: 1.14-1.79; p=0.002), albumin <3.4 g/dl (HR: 2.04, 95% CI: 1.33-3.12; p=0.001), hemoglobin ≤12 (HR 1.96, 95% CI 1.38-2.78; p<0.001), supratherapeutic tacrolimus (HR 1.45, 95% CI 1.07 - 1.95; p=0.02), and baseline serum creatinine >1.1 mg/dl (HR: 1.87, 95% CI: 1.48-2.35; p<0.001). Peri-engraftment AKI was associated with worse overall survival (HR 1.40, 95% CI: 1.16-1.71; p<0.001) and non-relapse mortality (subdistribution HR 2.10, 95% CI: 1.52-2.89; p<0.001). Kidney recovery occurred in 18%, 15%, and 30% of patients with stage 1, 2, and 3 AKI without KRT, respectively, and 4 of 16 (25%) patients were liberated from KRT.

CONCLUSION

Peri-engraftment AKI is common among RIC allogeneic HCT recipients. We identified several important risk factors for peri-engraftment AKI. Peri-engraftment AKI is associated with worse overall survival and non-relapse morality, highlighting the importance of timely recognition and management of AKI.

The natural killer cell immunotherapy platform: an overview of the landscape of clinical trials in liquid and solid tumors

The translation of natural killer (NK) cells to the treatment of malignant disease has made significant progress in the last few decades. With a variety of available sources and improvements in both in vitro and in vivo NK cell expansion, the NK cell immunotherapy platform has come into its own. The enormous effort continues to further optimize this platform, including ways to enhance NK cell persistence, trafficking to the tumor microenvironment, and cytotoxicity. As this effort bears fruit, it is translated into a plethora of clinical trials in patients with advanced malignancies. The adoptive transfer of NK cells, either as a standalone therapy or in combination with other immunotherapies, has been applied for the treatment of both liquid and solid tumors, with numerous early-phase trials showing promising results. This review aims to summarize the key advantages of NK cell immunotherapy, highlight several of the current approaches being taken for its optimization, and give an overview of the landscape of clinical trials translating this platform into clinic.

2098. Cytomegalovirus (CMV) Infection Following Hematopoietic Cell Transplantation (HCT) with Post-transplant Cyclophosphamide (PTCy): Outcomes in Haploidentical versus Matched or Mismatched Unrelated Donor (MUD/MMURD) Allografts

Background

PTCy is increasingly being used in MUD/MMURD, and haploidentical donor HCT for prevention of graft-versus-host disease (GVHD). PTCy has been associated with increased risk of infections including CMV viremia after HCT. It remains unclear if this observation is independent of graft type. This study aims to evaluate the incidence of clinically significant CMV infection (CS-CMVi) following PTCy in MUD/MMURD compared to haploidentical donor HCT.

Methods

We performed a single-center retrospective study of all adults undergoing HCT with PTCy between January 1, 2015 and July 1, 2021. CS-CMVi, defined as CMV viremia or disease requiring initiation of CMV therapy, was evaluated in two groups: haploidentical HCT (n=170) and MUD/MMURD HCT (n=137). We assessed the incidence of CMV viremia, CS-CMVi, and CMV disease, as well as incidence of letermovir breakthrough infections and late CMV events after cessation of prophylaxis. Cumulative Incidence Functions were calculated based on time to CS-CMVi using dates of infection-free death, disease relapse, and repeat HCT as competing risks.

Results

The one-year cumulative incidence of CS-CMVi accounting for competing risks was 25% (95% CI 19 – 32) in the haploidentical group and 18% (95% CI 12 – 25) in the MUD/MMURD group (HR 1.50; 95% CI 0.91 – 2.46; p=0.11). CMV disease was rare, (haploidentical n=1; MUD/MMURD n=1) and no patients died of CMV infection. CS-CMVi in CMV seropositive patients was more common in the haploidentical group (23% versus 9%; p=0.002). Notably, CMV D+/R- HCT patients had a significantly higher rate of CS-CMVi in the MUD/MMURD cohort than in the haploidentical cohort. Of the CS-CMVi, letermovir breakthrough constituted 26% in the haploidentical group and 29% in the MUD/MMURD group. Late infections after cessation of letermovir occurred in only 14% of cases in the haploidentical group and 25% of cases in the MUD/MMURD group.

Conclusion

Rates of CS-CMVi, CMV viremia, and CMV disease were similar following PTCy in haploidentical donor HCT and MUD/MMURD HCT. CS-CMVi in CMV seropositive patients was more common in the haploidentical donor HCT population and MUD/MMURD HCT recipients had a higher incidence of CS-CMVi in the D+/R- patients.

Disclosures

Roman M. Shapiro, M.D., Miltenyi Biotec: Honoraria Rizwan Romee, M.D., Crispr Therapeutics: Grant/Research Support|Glycostem Therapeutics: Advisor/Consultant|NK Therapeutics: Advisor/Consultant|Skyline Therapeutics: Grant/Research Support Robert J. Soiffer, M.D., CSL Behring: Advisor/Consultant|Gilead: Career Chair Development Award|Jasper Therapeutics: Advisor/Consultant|Jazz Pharmaceuticals: Advisor/Consultant|Juno (BMS): DSMB|Kiadis: Board Member|Vor: Advisor/Consultant Vincent T. T. Ho, M.D., Alexion Pharmaceuticals: Advisor/Consultant|Allovir: Advisor/Consultant|Allovir: DSMC|Jazz Pharmaceuticals: Grant/Research Support|Omeros: Advisor/Consultant Nicolas C. Issa, MD, AiCuris: Grant/Research Support|Merck: Grant/Research Support.

Abstract A08: Divergent tumor cell states in neuroblastoma possess distinct immunogenic phenotypes

Active immunotherapy approaches for neuroblastoma (NB), a pediatric cancer of the sympathetic nervous system, has met with limited success. Especially challenging is the genetic heterogeneity of NB which makes it difficult to identify factors that consistently indicate the likelihood of an effective immune response and thereby select patients who are most likely to benefit from immunotherapy. Hence, we undertook an unbiased analysis of gene expression signatures from &gt;500 well-annotated primary NBs representing diverse clinical and genetic subtypes to identify of predictors of immune response. Using clustering analysis of bulk transcriptomic signatures from these tumors, we identified a subset of NBs that was notable for the high expression of genes associated with anti-tumor immune response. These “immunogenic” tumors showed a predominance of gene expression signatures derived from malignant cells with primitive neural crest-like or mesenchymal properties, one of the two cell states that shape intratumoral heterogeneity in NB. In contrast, tumors that expressed committed, adrenergic neuron-like signatures were less immunogenic. Single-cell (sc) RNA-seq and immunohistochemistry analysis further confirmed that NBs comprise both adrenergic and mesenchymal tumor cells, and that the presence of mesenchymal cells positively associated with immune cell infiltration into the TME. scRNA-seq also revealed that mesenchymal NB cells were enriched for inflammatory gene signature. Gene expression analysis of isogenic pairs of adrenergic and mesenchymal cells showed that mesenchymal NBs differentially upregulate genes involved in regulating antigen processing and presentation, MHC class I expression, type-I interferon and TLR3 signaling, and NK cell activation. This is achieved through a permissive chromatin landscape at the promoters of these immune regulatory genes that support their high expression in mesenchymal cells. By contrast, in adrenergic cells, tumor-intrinsic immune genes are epigenetically silenced by the PRC2 complex and PRC2 inhibition leads to increased immune cell activation. Remarkably, induction of the mesenchymal state in adrenergic cells through transcriptional reprogramming by PRRX1 or therapy resistance is accompanied by the epigenetic activation of innate and adaptive immune response genes. Functionally, the inherent immunogenicity of mesenchymal cells promotes T cell infiltration by secreting inflammatory cytokines, enables efficient targeting by antigen-specific cytotoxic T and NK cells, and imparts responsiveness to immune checkpoint blockade in a syngeneic NB model. In conclusion, our study uncovers an unappreciated link between immunogenicity and tumor lineage state in NB, and rationalizes future interrogations into (i) avenues through which the vulnerability of mesenchymal cells to immune-mediated targeting could be harnessed clinically and (ii) how perturbation of epigenetically-regulated cell states could be harnessed to promote anti-tumor immune response.

Citation Format: Satyaki Sengupta, Sanjukta Das, Angela C. Crespo, Annelisa M. Cornel, Anand G. Patel, Navin R. Mahadevan, Marco Campisi, Alaa K. Ali, Bandana Sharma, Jared H. Rowe, Rogier Versteeg, Rudolf Jaenisch, Stefani Spranger, Rizwan Romee, Brian C. Miller, David A. Barbie, Stefan Nierkens, Michael A. Dyer, Judy Lieberman, Rani E. George. Divergent tumor cell states in neuroblastoma possess distinct immunogenic phenotypes [abstract]. In: Proceedings of the AACR Special Conference: Tumor Immunology and Immunotherapy; 2022 Oct 21-24; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2022;10(12 Suppl):Abstract nr A08.

Activation of Tumor-Cell STING Primes NK-Cell Therapy

Activation of the stimulator of interferon genes (STING) pathway promotes antitumor immunity but STING agonists have yet to achieve clinical success. Increased understanding of the mechanism of action of STING agonists in human tumors is key to developing therapeutic combinations that activate effective innate antitumor immunity. Here, we report that malignant pleural mesothelioma cells robustly express STING and are responsive to STING agonist treatment ex vivo. Using dynamic single-cell RNA sequencing of explants treated with a STING agonist, we observed CXCR3 chemokine activation primarily in tumor cells and cancer-associated fibroblasts, as well as T-cell cytotoxicity. In contrast, primary natural killer (NK) cells resisted STING agonist-induced cytotoxicity. STING agonists enhanced migration and killing of NK cells and mesothelin-targeted chimeric antigen receptor (CAR)-NK cells, improving therapeutic activity in patient-derived organotypic tumor spheroids. These studies reveal the fundamental importance of using human tumor samples to assess innate and cellular immune therapies. By functionally profiling mesothelioma tumor explants with elevated STING expression in tumor cells, we uncovered distinct consequences of STING agonist treatment in humans that support testing combining STING agonists with NK and CAR-NK cell therapies.

Memory-like NK cells armed with a neoepitope-specific CAR exhibit potent activity against NPM1 mutated acute myeloid leukemia

Acute myeloid leukemia (AML) remains a therapeutic challenge, and a paucity of tumor-specific targets has significantly hampered the development of effective immune-based therapies. Recent paradigm-changing studies have shown that natural killer (NK) cells exhibit innate memory upon brief activation with IL-12 and IL-18, leading to cytokine-induced memory-like (CIML) NK cell differentiation. CIML NK cells have enhanced antitumor activity and have shown promising results in early phase clinical trials in patients with relapsed/refractory AML. Here, we show that arming CIML NK cells with a neoepitope-specific chimeric antigen receptor (CAR) significantly enhances their antitumor responses to nucleophosphmin-1 (NPM1)-mutated AML while avoiding off-target toxicity. CIML NK cells differentiated from peripheral blood NK cells were efficiently transduced to express a TCR-like CAR that specifically recognizes a neoepitope derived from the cytosolic oncogenic NPM1-mutated protein presented by HLA-A2. These CAR CIML NK cells displayed enhanced activity against NPM1-mutated AML cell lines and patient-derived leukemic blast cells. CAR CIML NK cells persisted in vivo and significantly improved AML outcomes in xenograft models. Single-cell RNA sequencing and mass cytometry analyses identified up-regulation of cell proliferation, protein folding, immune responses, and major metabolic pathways in CAR-transduced CIML NK cells, resulting in tumor-specific, CAR-dependent activation and function in response to AML target cells. Thus, efficient arming of CIML NK cells with an NPM1-mutation-specific TCR-like CAR substantially improves their innate antitumor responses against an otherwise intracellular mutant protein. These preclinical findings justify evaluating this approach in clinical trials in HLA-A2+ AML patients with NPM1c mutations.

Abstract 4168: Tumor cell stimulator of interferon genes (STING) activation primes NK cell therapy in mesothelioma

Background: Activation of the anti-viral STING pathway promotes antitumor immunity but STING agonists have yet to achieve clinical success. Understanding their mechanism of action in human tumors is key to developing STING-based therapies and combinations. Higher tumor STING expression correlates with better response to treatment and multiple cancers have been shown to silence STING and the downstream interferon response to avoid immune detection, demonstrating an important role for tumor cell STING in antitumor immunity. Recent mouse studies have explored the complex interplay of STING activation in the tumor immune microenvironment (TIME), identifying unexpected T-cell toxicity and novel effector mechanisms including NK cells. Yet how STING agonists impact the human TIME has not been carefully examined and could inform development of novel therapeutic combinations. Here we address this question using human tumors cultured ex vivo to maintain the TIME, dissecting STING agonist response in malignant pleural mesothelioma (MPM), an inflamed cancer with high STING expression.

Methods: We performed STING immunohistochemistry on 300 thoracic tumor specimens, followed by functional ex vivo studies of STING agonist response in human mesothelioma explants, measuring cell death and cytokine production. Dynamic single cell RNA sequencing was performed after treatment with a STING agonist. Primary human T-cells and NK cells were used to study STING agonist toxicity in the context of STING cycling and patient derived organotypic tumor spheroids (PDOTS) were treated for six days with STING agonists +/- NK and anti-mesothelin chimeric antigen receptor (CAR)-NK cell therapies.

Results: Amongst thoracic cancers, MPM robustly expressed tumor cell STING and was responsive to STING agonist treatment ex vivo. We observed tumor cell death &gt;20%, p&lt;0.05 in 12/35 MPM PDOTS after STING agonist treatment. Cell death was prevented by CD8 neutralizing antibody co-treatment. Dynamic single-cell RNA sequencing of MPM explants treated with a STING agonist unveiled CXCR3 chemokine activation primarily in tumor cells and cancer associated fibroblasts, coupled with an interferon stimulated gene program. However, STING agonism was also toxic to T-cells. In contrast, primary NK cells manifested rapid STING turnover and resisted STING agonist-induced toxicity. STING agonists enhanced NK and especially anti-mesothelin CAR-NK cell migration and killing, improving therapeutic activity in MPM PDOTS.

Conclusions: MPM, an inflamed cancer type with marginal response to immune checkpoint blockade, demonstrated high tumor cell STING expression and response to STING agonists in combination with NK cell therapies ex vivo. These studies reveal the fundamental importance of using human tumor samples to assess innate and cellular immune therapies, identifying STING agonism as an effective strategy to prime NK cell therapy.

Citation Format: Erik H. Knelson, Elena Ivanova, Mubin Tarannum, Marco Campisi, Patrick H. Lizotte, Matthew A. Booker, Brittany Meisenheimer, Minyue Chen, Nathaniel Spicer, Bonje Obua, Ha V. Vo, Thomas P. Albertson, Marina Vivero, Michael Y. Tolstorukov, Rizwan Romee, Cloud P. Paweletz, Raphael Bueno, David A. Barbie. Tumor cell stimulator of interferon genes (STING) activation primes NK cell therapy in mesothelioma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 4168.

Abstract 568: A novel memory-like NK cell CAR targeting proximal mesothelin domain shows promising preclinical activity in ovarian cancer using cell lines and patient derived organoids

Epithelial ovarian cancer (OVC) is the leading cause of death among gynecological malignancies. Natural killer (NK) cells are an attractive platform for immunotherapy owing to their superior safety, multiple mechanisms of target killing, and reduced risk of alloreactivity. Recently, paradigm-shifting studies have shown that brief activation of NK cells with inflammatory cytokines induces differentiation into cytokine induced memory-like (CIML) NK cells. CIML NK cells have demonstrated potent anti-leukemia activity in preclinical settings and in recent clinical trials and therefore represent a novel platform for genetically modified chimeric antigen receptor (CAR) cells for OVC therapy. Mesothelin (MSLN) is expressed in around 82% of OVCs and its expression is corelated with chemoresistance, increased metastasis, and poor overall survival in patients. We hypothesize arming CIML NK cells with a CAR targeting the proximal mesothelin domain will enhance their antitumor responses. We designed and tested anti-MSLN CAR CIML NK cells for their anti-cancer functionality against OVC cell lines and patient-derived organoids (PDOs). We first validated the mesothelin expression in 13 OVC patient samples which, based on pathological scoring showed high mesothelin in 8, moderate in 3, and low in 2 patient samples. PDOs also showed high expression of mesothelin, confirming it as an attractive candidate for CAR cells. We designed the aMSLN-CAR using an ScFv sequence against the proximal domain of the protein with 4-1BB and CD3ζ as co-stimulatory domains. Primary NK cells were purified from peripheral blood, activated using IL-12, IL-18, and IL-15 to afford CIML NK cells. The CAR gene was transduced into CIML NK cells via our optimized baboon lentiviral system to achieve a high transduction efficiency of 40-60%. The direct cytotoxic effect of these NK cells was tested against OVC cell lines. OVC cell lines were co-cultured with NK cells at various effector:target (E:T) ratios for 6 hours and analyzed using apoptotic markers. Compared to CIML NK cells, aMSLN-CAR CIML NK cells showed enhanced cytotoxicity against OVCAR3 (47.9% vs 14.8%), SKOV3 (29.3% vs 8.0%) and OVCAR8 (60.7% vs 39.8%) at 10:1 ratio. To test the therapeutic potential of CAR CIML NK cells in vitro, three different PDOs were used. Cytotoxicity was determined by evaluating apoptotic EpCAM+ cancer cells amongst the organoid cell population after 18-hour co-culture with NK cells. The aMSLN-CAR CIML NK cells were shown to cause increased apoptosis in cells from PDOs compared to CIML NK cells; 58.2% vs 11.0%, 4.5% vs 61.0%, and 10.5% vs 32.0%. We are currently evaluating the in vivo functionality of aMSLN-CAR CIML NK cells in a xenograft mouse model using OVC cell lines and PDOs. The successful application of CAR CIML-NK cells will pave way for the use of NK cell platforms for other solid tumors.

Citation Format: Mubin Tarannum, Juliana A. Vergara, Yasmin Abdulhamid, Khanhlinh Dinh, Katherine N. Lynch, Sarah Hill, Rizwan Romee. A novel memory-like NK cell CAR targeting proximal mesothelin domain shows promising preclinical activity in ovarian cancer using cell lines and patient derived organoids [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 568.

Abstract CT540: A phase 1 trial of cytokine-induced memory-like (CIML) natural killer (NK) cell therapy with IL-15 superagonist in advanced head and neck cancer: Part 1 results

Purpose: Outcomes for patients with recurrent, incurable or metastatic (R/M) squamous cell carcinoma of the head and neck (SCCHN) refractory to platinum and immunotherapy are poor. Cellular therapies are emerging treatments with potential utility in epithelial cancers. This proof-of-concept trial investigates an allogeneic cytokine-induced, memory-like (CIML) NK cell infusion with IL-15 superagonist (sa) after lymphodepleting (LD) chemotherapy in advanced SCCHN.

Patients and methods: This phase 1 single-center trial enrolled patients (pts) with R/M SCCHN regardless of human papillomavirus (HPV) status who had prior platinum and immunotherapy. Pts received LD fludarabine (25 mg/m2) and cyclophosphamide (60 mg/m2/kg) on days -6 to -2 prior to haploidentical CIML NK cell infusion on day 0 (5-10 x 106 viable cells/kg=dose level 0) followed by N-803 (IL-15sa, 15 mcg/kg subcutaneously) starting on day +1 every 21-days for 4-doses. Part 1 treated 3 pts at dose level 0; &lt;2 DLTs triggered an additional 3 pts. Part 2 will treat an additional 6 pts with lead-in ipilimumab (day -7). Primary objective: safety, maximum tolerated dose of CIML NK cells. Secondary objectives: objective response rate, progression-free survival (PFS), overall survival (OS), and phenotypic expansion and function of adoptively transferred NK cells.

Results: From 9/8/20 to 9/7/21, 6 pts enrolled to Part 1. One DLT was observed at dose level 0. Among 6 pts, median age: 59; 5/6 (83%) were men; 5/6 (83%) had oropharyngeal primaries (4 HPV+) with a median 6 prior lines of therapy for R/M disease (range: 4-8). R/M disease sites: lung, bone, skin, liver. 5/6 (83%) had offspring donors. Grade (G) 3-4 hematologic adverse events were common (6/6, 100%). One patient died of G5 febrile neutropenia and infection. Median days hospitalized: 14 (range: 9-37). Mild cytokine release syndrome was observed in 5/6 (83%) (median peak ferritin: 2248, CRP: 168); 3/5 required anti-IL6 therapy; no neurotoxicity was noted. There were no dose adjustments or discontinuation of therapy. One (17%) partial response (PR) was observed lasting 6.5 months; 4 (67%) pts had stable disease (SD), and 1 (17%) had progression. Tumor regression was observed in 3/6 (50%) pts at day +30. At a median follow-up of 9.5 months, median PFS: 3.4 months (95%CI 2.6-6.5); median OS: 4.7 months (95%CI 3.4-11.8). CIML NK cells showed large expansion in the peripheral blood (PB) at day +7 in all pts; mean increase: 66% (6-fold; standard deviation [SD] 10.5), to constitute 80% (SD 12.1) of PB lymphocytes. In pts with tumor regression at day +30 compared to those without, the % of PB NK cells remained high at day +28 (mean: 78 vs. 11%). PB NK cells remained &gt;50% at day +42 in the pt with a PR.

Conclusion: Allogeneic CIML NK cells can induce tumor regression associated with persistent CIML NK cell expansion among advanced SCCHN pts. In Part 1 we demonstrate safety and feasibility with the expected risks of LD conditioning. These findings have important implications for the development of cellular therapies in solid tumors.

Citation Format: Glenn J. Hanna, Kimberly Coleman, Grace Birch, Robert A. Redd, Alejandro Alonso, Samantha Bednarz, Heather Daley, Diego E. Hernandez Rodriguez, Kit L. Shaw, Robert I. Haddad, Ravindra Uppaluri, Jerome Ritz, Sarah Nikiforow, Robert J. Soiffer, Rizwan Romee. A phase 1 trial of cytokine-induced memory-like (CIML) natural killer (NK) cell therapy with IL-15 superagonist in advanced head and neck cancer: Part 1 results [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr CT540.

Single cell transcriptomic characterization of natural killer (NK) cell populations in clear cell renal cell carcinoma and association with clinical outcomes

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Background: Natural killer (NK) cells are thought to play a key role in the immune response against cancer, including clear cell renal cell carcinoma (ccRCC). However, the transcriptomic landscape of NK cells in ccRCC and the mechanisms of NK cell evasion by ccRCC are poorly understood. Methods: We analyzed scRNA-sequencing (10x Genomics) data from tumor specimens and adjacent non-tumor tissue from ccRCC at various clinical stages. Clustering analysis and NK cell lineage markers were used to identify distinct NK cell populations. Differential gene expression analysis was used to characterize each cluster compared to the total population of NK cells. Results were correlated with clinical stage. Gene signatures, derived from NK cell subclusters of interest, were then used to interrogate bulk transcriptomic datasets and associate expression with clinical outcomes. Results: Single-cell RNA-sequencing data was analyzed from 13 patients, corresponding to > 23,000 individual NK cells. Clustering analysis revealed 11 distinct NK cell subsets, including two “resident” NK cell clusters that were enriched among patients with metastatic disease. These clusters expressed CD9, ITGA1/CD49a, and ITGAE/CD103. Further examination of these clusters showed a common panel of differentially expressed genes, including decreased expression of cytotoxicity markers and upregulation of inhibitor checkpoints such as KLRC1/NKG2a. A gene expression signature representing this resident NK cell phenotype was associated with worse overall survival in two large, independent patient cohorts (TCGA and CheckMate-025). Conclusions: Among patients with ccRCC, a retrospective single cell transcriptomic analysis revealed heterogeneous NK cell populations. A seemingly dysfunctional, “resident” NK cell phenotype is enriched among patients with metastatic disease and is associated with worse survival in patients with advanced ccRCC, including those treated with immune checkpoint inhibitors. Restoration of NK cell function could be a future therapeutic opportunity among patients with ccRCC.

Expansion, persistence, and efficacy of donor memory-like NK cells infused for posttransplant relapse

BackgroundResponses to conventional donor lymphocyte infusion for postallogeneic hematopoietic cell transplantation (HCT) relapse are typically poor. Natural killer (NK) cell-based therapy is a promising modality to treat post-HCT relapse.MethodsWe initiated this ongoing phase I trial of adoptively transferred cytokine-induced memory-like (CIML) NK cells in patients with myeloid malignancies who relapsed after haploidentical HCT. All patients received a donor-derived NK cell dose of 5 to 10 million cells/kg after lymphodepleting chemotherapy, followed by systemic IL-2 for 7 doses. High-resolution profiling with mass cytometry and single-cell RNA sequencing characterized the expanding and persistent NK cell subpopulations in a longitudinal manner after infusion.ResultsIn the first 6 enrolled patients on the trial, infusion of CIML NK cells led to a rapid 10- to 50-fold in vivo expansion that was sustained over months. The infusion was well tolerated, with fever and pancytopenia as the most common adverse events. Expansion of NK cells was distinct from IL-2 effects on endogenous post-HCT NK cells, and not dependent on CMV viremia. Immunophenotypic and transcriptional profiling revealed a dynamic evolution of the activated CIML NK cell phenotype, superimposed on the natural variation in donor NK cell repertoires.ConclusionGiven their rapid expansion and long-term persistence in an immune-compatible environment, CIML NK cells serve as a promising platform for the treatment of posttransplant relapse of myeloid disease. Further characterization of their unique in vivo biology and interaction with both T cells and tumor targets will lead to improvements in cell-based immunotherapies.Trial RegistrationClinicalTrials.gov NCT04024761.FundingDunkin' Donuts, NIH/National Cancer Institute, and the Leukemia and Lymphoma Society.

Invasive Yeast Infection After Haploidentical Donor Hematopoietic Cell Transplantation Associated with Cytokine Release Syndrome

BACKGROUND

Use of haploidentical donor hematopoietic cell transplantation (haploHCT) has expanded but recent reports raise concern for increased rates of infectious complications. The incidence and risk factors for invasive fungal disease (IFD) after haploHCT have not been well elucidated.

OBJECTIVE

The objective of this study is to evaluate the incidence and risk factors for IFD after haploHCT. The identification of key risk factors will permit targeted prevention measures and may explain elevated risk for other infectious complications after haploHCT.

STUDY DESIGN

We performed a single-center retrospective study of all adults undergoing haploHCT between May 2011 and May 2021 (n=205). The 30-day and one-year cumulative incidence of proven or probable IFD and one-year non-relapse mortality (NRM) were assessed. Secondary analysis evaluated risk factors for invasive yeast infection (IYI) using univariate and multivariable Cox regression models.

RESULTS

Twenty-nine patients (14%) developed IFD following haploHCT. Nineteen (9.3%) developed IYI in the first year, 13 of which occurred early with a 30-day cumulative incidence of 6.3% (95% CI 2.9 - 9.6%) and increased NRM in patients with IYI (53.9% versus 10.9%). The majority of yeast isolates (17/20; 85%) were fluconazole susceptible. The incidence of IYI in the first 30 days after haploHCT was 10% among the 110 (54%) patients who developed cytokine release syndrome (CRS) and 21% among the 29 (14%) who received tocilizumab. On multivariable analysis, AML (HR 6.24; 1.66 - 23.37; p=0.007) and CRS (HR 4.65; 1.00 - 21.58; p=0.049) were associated with an increased risk of early IYI after haploHCT.

CONCLUSION

CRS after haploHCT is common and is associated with increased risk of early IYI. The identification of CRS as a risk factor for IYI raises questions about its potential association with other infections after haploHCT. Recognition of key risk factors for infection may permit individualized strategies for prevention and intervention and minimize potential side effects.

Phenotypic and functional characterization of the CD6-ALCAM T cell costimulatory pathway after allogeneic cell transplantation

CD6 is a co-stimulatory receptor expressed on T cells that binds activated leukocyte cell adhesion molecule (ALCAM), expressed on antigen presenting cells, epithelial and endothelial tissues. The CD6-ALCAM pathway plays an integral role in modulating T-cell activation, proliferation, and trafficking. In this study we examined expression of CD6 by reconstituting T cells in 95 patients after allogeneic cell transplantation and evaluated the effects of itolizumab, an anti-CD6 monoclonal antibody, on T-cell activation. CD6 T cells reconstituted early after transplant with CD4 regulatory T cells (Treg)-expressing lower levels of CD6 compared to conventional CD4 T cells (Tcon) and CD8 T cells. After onset of acute graft-versus-host disease (aGvHD), CD6 expression was further reduced in Treg and CD8 T cells compared to healthy donors, while no difference was observed for Tcon. ALCAM expression was highest in plasmacytoid dendritic cells (pDC), lowest in myeloid dendritic cells (mDC) and intermediate in monocytes and was generally increased after aGvHD onset. Itolizumab inhibited CD4 and CD8 T-cell activation and proliferation in preGvHD samples, but inhibition was less prominent in samples collected after aGvHD onset, especially for CD8 T cells. Functional studies showed that itolizumab did not mediate direct cytolytic activity or antibody-dependent cytotoxicity in vitro. However, itolizumab efficiently abrogated the costimulatory activity of ALCAM on T-cell proliferation, activation and maturation. Our results identify the CD6-ALCAM pathway as a potential target for aGvHD control and a phase I/II study using itolizumab as first line treatment in combination with steroids for patients with aGvHD is currently ongoing (clinicaltrials gov. Identifier: NCT03763318).

Innovative Strategies to Improve the Clinical Application of NK Cell-Based Immunotherapy

Natural killer cells constitute a part of the innate immune system that mediates an effective immune response towards virus-infected and malignant cells. In recent years, research has focused on exploring and advancing NK cells as an active immunotherapy platform. Despite major advances, there are several key challenges that need to be addressed for the effective translation of NK cell research to clinical applications. This review highlights some of these challenges and the innovative strategies being developed to overcome them, including in vitro expansion, in vivo persistence, infiltration to the tumor site, and prevention of exhaustion.

Hematopoietic cell transplantation donor-derived memory-like NK cells functionally persist after transfer into patients with leukemia

Natural killer (NK) cells are innate lymphoid cells that eliminate cancer cells, produce cytokines, and are being investigated as a nascent cellular immunotherapy. Impaired NK cell function, expansion, and persistence remain key challenges for optimal clinical translation. One promising strategy to overcome these challenges is cytokine-induced memory-like (ML) differentiation, whereby NK cells acquire enhanced antitumor function after stimulation with interleukin-12 (IL-12), IL-15, and IL-18. Here, reduced-intensity conditioning (RIC) for HLA-haploidentical hematopoietic cell transplantation (HCT) was augmented with same-donor ML NK cells on day +7 and 3 weeks of N-803 (IL-15 superagonist) to treat patients with relapsed/refractory acute myeloid leukemia (AML) in a clinical trial (NCT02782546). In 15 patients, donor ML NK cells were well tolerated, and 87% of patients achieved a composite complete response at day +28, which corresponded with clearing high-risk mutations, including TP53 variants. NK cells were the major blood lymphocytes for 2 months after HCT with 1104-fold expansion (over 1 to 2 weeks). Phenotypic and transcriptional analyses identified donor ML NK cells as distinct from conventional NK cells and showed that ML NK cells persisted for over 2 months. ML NK cells expressed CD16, CD57, and high granzyme B and perforin, along with a unique transcription factor profile. ML NK cells differentiated in patients had enhanced ex vivo function compared to conventional NK cells from both patients and healthy donors. Overall, same-donor ML NK cell therapy with 3 weeks of N-803 support safely augmented RIC haplo-HCT for AML.

Autologous cellular therapy for myeloma: Giving ex vivo expanded NK cells their due

Ex vivo feeder-free autologous NK cell expansion is an efficient modality for clinical translation. In this issue of Cell Reports Medicine, Nahi et al. describe the use of this approach as consolidation therapy for multiple myeloma,¹ thereby reviving an alternate avenue for NK cell therapy.

Post-Transplantation Cyclophosphamide Is Associated with an Increase in Non-Cytomegalovirus Herpesvirus Infections in Patients with Acute Leukemia and Myelodysplastic Syndrome

The use of post-transplantation cyclophosphamide (PTCy) for graft-versus-host disease (GVHD) prophylaxis in recipients of haploidentical and fully matched transplantations is on the increase. Published studies have reported an increased incidence of cytomegalovirus (CMV) infection with the use of PTCy. Limited data exist on the incidence and outcomes of infection with non-CMV herpesviruses (NCHV) in this setting. The aim of this study was to evaluate the cumulative incidence of NCHV infections and the association of NCHV infections with transplantation-specific outcomes in recipients of haploidentical transplantation with PTCy (HaploCy), matched sibling donor transplantation with PTCy (SibCy), and matched sibling donor transplantation with calcineurin inhibitor-based prophylaxis (SibCNI). We hypothesized that, like CMV infection, HaploCy recipients of also will have a higher risk of NCHV infections. Using the Center for International Blood and Marrow Transplantation Research database, we analyzed 2765 patients (HaploCy, n = 757; SibCNI, n = 1605; SibCy, n = 403) who had undergone their first hematopoietic stem cell transplantation (HCT) between 2012 and 2017 for acute myelogenous leukemia, acute lymphoblastic leukemia, or myelodysplastic syndrome. The cumulative incidence of NCHV at 6 months post-NCT was 13.9% (99% confidence interval], 10.8% to 17.3%) in the HaploCy group, 10.7% (99% CI, 7.1% to 15%) in the SibCy group, and 5.7% (99% CI, 4.3% to 7.3%) in the Sib CNI group (P < .001). This was due primarily to a higher frequency of human herpesvirus 6 viremia reported in patients receiving PTCy. The incidence of Epstein-Barr viremia was low in all groups, and no cases of post-transplantation lymphoproliferative disorder were seen in either PTCy group. The incidence of NCHV organ disease was low in all 3 cohorts. The development of NCHV infection was associated with increased treatment-related mortality, particularly in the HaploCy group. There was no association with the development of GVHD, relapse, or disease-free survival. Patients in PTCy cohorts who did not develop NCHV infection had lower rates of cGVHD. This study demonstrates that the use of PTCy is associated with an increased risk of NCHV infection. The development of NCHV infection was associated with increased nonrelapse mortality, especially in the HaploCy group. Prospective trials should consider viral surveillance strategies in conjunction with assessment of immune reconstitution for a better understanding of the clinical relevance of viral reactivation in different HCT settings.

Adding venetoclax to fludarabine/busulfan RIC transplant for high-risk MDS and AML is feasible, safe, and active

Adding the selective BCL-2 inhibitor venetoclax to reduced-intensity conditioning chemotherapy (fludarabine and busulfan [FluBu2]) may enhance antileukemic cytotoxicity and thereby reduce the risk of posttransplant relapse. This phase 1 study investigated the recommended phase 2 dose (RP2D) of venetoclax, a BCL-2 selective inhibitor, when added to FluBu2 in adult patients with high-risk acute myeloid leukemia (AML), myelodysplastic syndromes (MDS), and MDS/myeloproliferative neoplasms (MPN) undergoing transplant. Patients received dose-escalated venetoclax (200-400 mg daily starting day -8 for 6-7 doses) in combination with fludarabine 30 mg/m2 per day for 4 doses and busulfan 0.8 mg/kg twice daily for 8 doses on day -5 to day -2 (FluBu2). Transplant related-toxicity was evaluated from the first venetoclax dose on day -8 to day 28. Twenty-two patients were treated. At study entry, 5 patients with MDS and MDS/MPN had 5% to 10% marrow blasts, and 18 (82%) of 22 had a persistent detectable mutation. Grade 3 adverse events included mucositis, diarrhea, and liver transaminitis (n = 3 each). Neutrophil/platelet recovery and acute/chronic graft-versus-host-disease rates were similar to those of standard FluBu2. No dose-limiting toxicities were observed. The RP2D of venetoclax was 400 mg daily for 7 doses. With a median follow-up of 14.7 months (range, 8.6-24.8 months), median overall survival was not reached, and progression-free survival was 12.2 months (95% confidence interval, 6.0-not estimable). In patients with high-risk AML, MDS, and MDS/MPN, adding venetoclax to FluBu2 was feasible and safe. To further address relapse risk, assessment of maintenance therapy after venetoclax plus FluBu2 transplant is ongoing. This study was registered at clinicaltrials.gov as #NCT03613532.

Cytokine-induced memory-like natural killer cells for cancer immunotherapy

Natural killer cells are an important part of the innate immune system mediating robust responses to virus-infected and malignant cells without needing prior antigen priming. NK cells have always been thought to be short-lived and with no antigen specificity; however, recent data support the presence of NK cell memory including in the hapten-specific contact hypersensitivity model and in certain viral infections. The memory-like features can also be generated by short-term activation of both murine and human NK cells with cytokine combination of IL-12, IL-15 and IL-18, imparting increased longevity and enhanced anticancer functionality. Preclinical studies and very early clinical trials demonstrate safety and very promising clinical activity of these cytokine-induced memory-like (CIML) NK cells, making them an attractive cell type for developing novel adoptive cellular immunotherapy strategies. Furthermore, efforts are on to arm them with novel gene constructs for enhanced tumor targeting and function.

Combination of dociparstat sodium (DSTAT), a CXCL12/CXCR4 inhibitor, with azacitidine for the treatment of hypomethylating agent refractory AML and MDS

Leukemia stem cells utilize cell adhesion molecules like CXCR4/CXCL12 to home to bone marrow stromal niches where they are maintained in a dormant, protected state. Dociparstat sodium (DSTAT, CX-01) is a low anticoagulant heparin with multiple mechanisms of action, including inhibition of the CXCR4/CXCL12 axis, blocking HMGB1, and binding platelet factor 4 (PF-4). We conducted a pilot study adding DSTAT to azacitidine for patients with AML or MDS unresponsive to or relapsed after prior hypomethylating agent therapy, hypothesizing that DSTAT may improve response rates. Twenty patients were enrolled, with a median of 2 prior lines of therapy and 6 cycles of prior hypomethylating agents. Among fifteen patients evaluable for response, there was 1 complete remission, and 3 marrow complete remissions, for a response rate of 27 % among evaluable patients (20 % overall). Hematologic improvement was observed in 5 additional patients. The median overall survival for all enrolled patients was 205 days (95 % CI 119-302). While cytopenias and infections were common, these were not out of proportion to what would be expected in this population of patients undergoing treatment with azacitidine alone. In summary, this trial demonstrated the feasibility of combining DSTAT with azacitidine, with several responses observed, suggesting this combination warrants further study.

Ibrutinib in Steroid-Refractory Chronic Graft-versus-Host Disease, a Single-Center Experience

Chronic graft-versus-host disease (cGVHD) is a leading cause of late morbidity and mortality after allogenic hematopoietic stem cell transplantation. Corticosteroid-based therapies are a mainstay of its initial treatment but there is no consensus in how to treat steroid-refractory cGVHD. Ibrutinib is a Bruton tyrosine kinase and IL-2-inducible kinase inhibitor thought to affect pathways driving cGVHD, and it was approved for the treatment of refractory cGVHD by the Food and Drug Administration (FDA) in August 2017 after a landmark phase 1b/2 study. It was the first medication approved for this indication, but how to best treat refractory cGVHD remains an open question, and there has been limited literature on ibrutinib after the FDA approval. This study sought to characterize the utilization and outcomes associated with ibrutinib use in cGVHD via a retrospective single-center study. Fifty-three patients were identified as having been treated with ibrutinib for cGVHD following FDA approval between September 1, 2017, and December 31, 2020, using an institutional data repository. Their records were reviewed for demographics, cGVHD characteristics, and outcomes. For the entire cohort, two-year overall survival was 76% (95% confidence interval [CI], 60% to 86%), with a median follow-up among survivors of 26 months (range, 1.3 to 39.5 months). However, the 2-year failure-free survival (FFS) after initiation of ibrutinib was 9% (95% CI, 2.6% to 20%), and the median FFS was 4.5 months (95% CI, 2.8 to 7.1 months). Events of FFS included treatment change due to lack of response or toxicity, malignant relapse, or non-treatment related mortality. At the time of this report, 11 patients (21%) remained on ibrutinib. At the time of the FFS event or last follow-up, 6 patients (12%) had a complete or partial response, 34 (64%) had stable disease, and 13 (25%) had progressive disease. Ibrutinib use was associated with no reduction in corticosteroid dose between ibrutinib initiation and FFS event or last follow-up (mean difference, 0.00; P = .98). The most frequently used noncorticosteroid cGVHD therapy after ibrutinib was ruxolitinib (n = 14; 33%). The most common adverse events associated with treatment discontinuation were infection (lung, skin, enterocolitis; n = 6), bleeding and bruising (hematoma, epistaxis, gastrointestinal bleed; n = 5), and muscle aches (n = 2). In a real-world setting, ibrutinib is associated with a modest response rate and FFS and its use in a narrower, more targeted patient population may be indicated.

Genome-scale screens identify factors regulating tumor cell responses to natural killer cells

To systematically define molecular features in human tumor cells that determine their degree of sensitivity to human allogeneic natural killer (NK) cells, we quantified the NK cell responsiveness of hundreds of molecularly annotated 'DNA-barcoded' solid tumor cell lines in multiplexed format and applied genome-scale CRISPR-based gene-editing screens in several solid tumor cell lines, to functionally interrogate which genes in tumor cells regulate the response to NK cells. In these orthogonal studies, NK cell-sensitive tumor cells tend to exhibit 'mesenchymal-like' transcriptional programs; high transcriptional signature for chromatin remodeling complexes; high levels of B7-H6 (NCR3LG1); and low levels of HLA-E/antigen presentation genes. Importantly, transcriptional signatures of NK cell-sensitive tumor cells correlate with immune checkpoint inhibitor (ICI) resistance in clinical samples. This study provides a comprehensive map of mechanisms regulating tumor cell responses to NK cells, with implications for future biomarker-driven applications of NK cell immunotherapies.

Standardizing Definitions of Hematopoietic Recovery, Graft Rejection, Graft Failure, Poor Graft Function, and Donor Chimerism in Allogeneic Hematopoietic Cell Transplantation: A Report on Behalf of the American Society for Transplantation and Cellular Therapy

Allogeneic hematopoietic cell transplantation (allo-HCT) is potentially curative for certain hematologic malignancies and nonmalignant diseases. The field of allo-HCT has witnessed significant advances, including broadening indications for transplantation, availability of alternative donor sources, less toxic preparative regimens, new cell manipulation techniques, and novel GVHD prevention methods, all of which have expanded the applicability of the procedure. These advances have led to clinical practice conundrums when applying traditional definitions of hematopoietic recovery, graft rejection, graft failure, poor graft function, and donor chimerism, because these may vary based on donor type, cell source, cell dose, primary disease, graft-versus-host disease (GVHD) prophylaxis, and conditioning intensity, among other variables. To address these contemporary challenges, we surveyed a panel of allo-HCT experts in an attempt to standardize these definitions. We analyzed survey responses from adult and pediatric transplantation physicians separately. Consensus was achieved for definitions of neutrophil and platelet recovery, graft rejection, graft failure, poor graft function, and donor chimerism, but not for delayed engraftment. Here we highlight the complexities associated with the management of mixed donor chimerism in malignant and nonmalignant hematologic diseases, which remains an area for future research. We recognize that there are multiple other specific, and at times complex, clinical scenarios for which clinical management must be individualized.

HLA-haploidentical vs matched unrelated donor transplants with posttransplant cyclophosphamide-based prophylaxis

Posttransplant cyclophosphamide (PTCy) graft-versus-host disease (GVHD) prophylaxis has enabled haploidentical (Haplo) transplantation to be performed with results similar to those after matched unrelated donor (MUD) transplantation with traditional prophylaxis. The relative value of transplantation with MUD vs Haplo donors when both groups receive PTCy/calcineurin inhibitor/mycophenolate GVHD prophylaxis is not known. We compared outcomes after 2036 Haplo and 284 MUD transplantations with PTCy GVHD prophylaxis for acute leukemia or myelodysplastic syndrome in adults from 2011 through 2018. Cox regression models were built to compare outcomes between donor types. Recipients of myeloablative and reduced-intensity regimens were analyzed separately. Among recipients of reduced-intensity regimens, 2-year graft failure (3% vs 11%), acute grades 2 to 4 GVHD (hazards ratio [HR], 0.70; P = .022), acute grades 3 and 4 GVHD (HR, 0.41; P = .016), and nonrelapse mortality (HR, 0.43; P = .0008) were lower after MUD than with Haplo donor transplantation. Consequently, disease-free (HR, 0.74; P = .008; 55% vs 41%) and overall (HR, 0.65; P = .001; 67% vs 54%) survival were higher with MUD than with Haplo transplants. Among recipients of myeloablative regimens, day-100 platelet recovery (95% vs 88%) was higher and grades 3 and 4 acute (HR, 0.39; P = .07) and chronic GVHD (HR, 0.66; P = .05) were lower after MUD than with Haplo donor transplantation. There were no differences in graft failure, relapse, nonrelapse mortality, and disease-free and overall survival between donor types with myeloablative conditioning regimens. These data extend and confirm the importance of donor-recipient HLA matching for allogeneic transplantation. A MUD is the preferred donor, especially for transplantations with reduced-intensity conditioning regimens.

Cytokine release syndrome after haploidentical hematopoietic cell transplantation: an international multicenter analysis

Haploidentical related donor transplantation (haplo-HCT) is associated with cytokine release syndrome (CRS). We conducted a multicenter retrospective study to analyze risk factors for CRS and outcomes after haplo-HCT. We included 451 patients from four academic centers receiving both peripheral blood and bone marrow grafts. Severe CRS was more common with PB vs. BM grafts (19.5% vs 4.9%, OR 2.9, p = 0.05). Multivariable analysis identified recipient CMV sero-positivity, prior transplant, HCT-CI score and donor-recipient sex mismatch as risk factors for severe CRS. Outcomes were analyzed with no CRS as the comparison group. Overall survival (OS) was superior with mild CRS (HR 0.64, p = 0.05) and worst with severe CRS (HR 2.12, p = 0.0038). Relapse risk was significantly decreased in both mild CRS (HR 0.38, p < 0.0001) and severe CRS (HR 0.17, p < 0.0001) groups. The risk of non-relapse mortality was notably higher in severe CRS group (HR 8.0, p < 0.0001), but not in mild CRS group. Acute GVHD was similar among groups. Chronic GVHD at 1 year was 18.5% for no CRS, 23% for mild CRS, and 4.3% for severe CRS (p = 0.0023), with the competing risk of early mortality and short follow up of surviving patients contributing to the low chronic GVHD rates in the severe CRS group.

Ruxolitinib resistance or intolerance in steroid-refractory acute graft-versus-host disease - a real-world outcomes analysis

Ruxolitinib for steroid-refractory acute graft-versus-host disease (SR-aGVHD) results in resistance or intolerance in 1/5 of patients. Outcomes of such patients are undefined. We identified these patients in a multicentre review and reported outcomes. Ruxolitinib-resistant aGVHD was identified in 48/307 patients. Among patients receiving additional therapy, the overall response rate to next therapy was 36%. Median survival was 21 days. Ruxolitinib intolerance led to treatment discontinuation in 16/307 patients. Ten intolerant patients received additional therapy with 50% experiencing continued improvement of aGVHD. Median survival was 50 days in these patients. These data serve as a baseline for future SR-aGVHD studies.

Incidence and impact of community respiratory viral infections in post-transplant cyclophosphamide-based graft-versus-host disease prophylaxis and haploidentical stem cell transplantation

Community respiratory viral infections (CRVIs) are associated with pulmonary function impairment, alloimmune lung syndromes and inferior survival in human leucocyte antigen (HLA)-matched allogeneic haematopoietic stem cell transplant (HCT) recipients. Although the incidence of viral infections in HLA-haploidentical HCT recipients who receive post-transplant cyclophosphamide (PTCy)-based graft-versus-host disease (GVHD) prophylaxis is reportedly increased, there are insufficient data describing the incidence of CRVIs and the impact of donor source and PTCy on transplant outcomes. Analysing patients receiving their first HCT between 2012 and 2017 for acute myeloid leukaemia, acute lymphoblastic leukaemia and myelodysplastic syndromes, we describe comparative outcomes between matched sibling transplants receiving either calcineurin-based GVHD prophylaxis (SibCNI, N = 1605) or PTCy (SibCy, N = 403), and related haploidentical transplants receiving PTCy (HaploCy, N = 757). The incidence of CRVIs was higher for patients receiving PTCy, regardless of donor type. Patients in the HaploCy cohort who developed a CRVI by day +180 had both a higher risk of treatment-related mortality [hazard ratio (HR) 2⋅14, 99% confidence interval (CI) 1⋅13-4⋅07; P = 0⋅002] and inferior 2-year overall survival (HR 1⋅65, 99% CI 1⋅11-2⋅43; P = 0⋅001) compared to SibCNI with no CRVI. This finding justifies further research into long-term antiviral immune recovery, as well as development of preventive and treatment strategies to improve long-term outcomes in such patients.

Posttransplant cyclophosphamide is associated with increased cytomegalovirus infection: a CIBMTR analysis

Prior studies suggest increased cytomegalovirus (CMV) infection after haploidentical donor transplantation with posttransplant cyclophosphamide (HaploCy). The role of allograft source and posttransplant cyclophosphamide (PTCy) in CMV infection is unclear. We analyzed the effect of graft source and PTCy on incidence of CMV infection, and effects of serostatus and CMV infection on transplant outcomes. We examined patients reported to the Center for International Blood and Marrow Transplantation Research between 2012 and 2017 who had received HaploCy (n = 757), matched related (Sib) with PTCy (SibCy, n = 403), or Sib with calcineurin inhibitor-based prophylaxis (SibCNI, n = 1605). Cumulative incidences of CMV infection by day 180 were 42%, 37%, and 23%, respectively (P < .001). CMV disease was statistically comparable. CMV infection risk was highest for CMV-seropositive recipients (R+), but significantly higher in PTCy recipients regardless of donor (HaploCy [n = 545]: hazard ratio [HR], 50.3; SibCy [n = 279]: HR, 47.7; SibCNI [n = 1065]: HR, 24.4; P < .001). D+/R- patients also had increased risk for CMV infection. Among R+ or those developing CMV infection, HaploCy had worse overall survival and nonrelapse mortality. Relapse was unaffected by CMV infection or serostatus. PTCy was associated with lower chronic graft-versus-host disease (GVHD) overall, but CMV infection in PTCy recipients was associated with higher chronic GVHD (P = .006). PTCy, regardless of donor, is associated with higher incidence of CMV infection, augmenting the risk of seropositivity. Additionally, CMV infection may negate the chronic GVHD protection of PTCy. This study supports aggressive prevention strategies in all receiving PTCy.