Preclinical studies show that Co-STARs combine the advantages of chimeric antigen and T cell receptors for the treatment of tumors with low antigen densities.

Two types of engineered T cells have been successfully used to treat patients with cancer, one with an antigen recognition domain derived from antibodies [chimeric antigen receptors (CARs)] and the other derived from T cell receptors (TCRs). CARs use high-affinity antigen-binding domains and costimulatory domains to induce T cell activation but can only react against target cells with relatively high amounts of antigen. TCRs have a much lower affinity for their antigens but can react against target cells displaying only a few antigen molecules. Here, we describe a new type of receptor, called a Co-STAR (for costimulatory synthetic TCR and antigen receptor), that combines aspects of both CARs and TCRs. In Co-STARs, the antigen-recognizing components of TCRs are replaced by high-affinity antibody fragments, and costimulation is provided by two modules that drive NF-κB signaling (MyD88 and CD40). Using a TCR-mimic antibody fragment that targets a recurrent p53 neoantigen presented in a common human leukocyte antigen (HLA) allele, we demonstrate that T cells equipped with Co-STARs can kill cancer cells bearing low densities of antigen better than T cells engineered with conventional CARs and patient-derived TCRs in vitro. In mouse models, we show that Co-STARs mediate more robust T cell expansion and more durable tumor regressions than TCRs similarly modified with MyD88 and CD40 costimulation. Our data suggest that Co-STARs may have utility for other peptide-HLA antigens in cancer and other targets where antigen density may limit the efficacy of engineered T cells.

Cancer therapy with antibodies.

The greatest challenge in cancer therapy is to eradicate cancer cells with minimal damage to normal cells. Targeted therapy has been developed to meet that challenge, showing a substantially increased therapeutic index compared with conventional cancer therapies. Antibodies are important members of the family of targeted therapeutic agents because of their extraordinarily high specificity to the target antigens. Therapeutic antibodies use a range of mechanisms that directly or indirectly kill the cancer cells. Early antibodies were developed to directly antagonize targets on cancer cells. This was followed by advancements in linker technologies that allowed the production of antibody-drug conjugates (ADCs) that guide cytotoxic payloads to the cancer cells. Improvement in our understanding of the biology of T cells led to the production of immune checkpoint-inhibiting antibodies that indirectly kill the cancer cells through activation of the T cells. Even more recently, bispecific antibodies were synthetically designed to redirect the T cells of a patient to kill the cancer cells. In this Review, we summarize the different approaches used by therapeutic antibodies to target cancer cells. We discuss their mechanisms of action, the structural basis for target specificity, clinical applications and the ongoing research to improve efficacy and reduce toxicity.

TRBC1-targeting antibody-drug conjugates for the treatment of T cell cancers.

Antibody and chimeric antigen receptor (CAR) T cell-mediated targeted therapies have improved survival in patients with solid and haematologic malignancies1-9. Adults with T cell leukaemias and lymphomas, collectively called T cell cancers, have short survival10,11 and lack such targeted therapies. Thus, T cell cancers particularly warrant the development of CAR T cells and antibodies to improve patient outcomes. Preclinical studies showed that targeting T cell receptor ß-chain constant region 1 (TRBC1) can kill cancerous T cells while preserving sufficient healthy T cells to maintain immunity12, making TRBC1 an attractive target to treat T cell cancers. However, the first-in-human clinical trial of anti-TRBC1 CAR T cells reported a low response rate and unexplained loss of anti-TRBC1 CAR T cells13,14. Here we demonstrate that CAR T cells are lost due to killing by the patient's normal T cells, reducing their efficacy. To circumvent this issue, we developed an antibody-drug conjugate that could kill TRBC1+ cancer cells in vitro and cure human T cell cancers in mouse models. The anti-TRBC1 antibody-drug conjugate may provide an optimal format for TRBC1 targeting and produce superior responses in patients with T cell cancers.

Identification of nonsense-mediated decay inhibitors that alter the tumor immune landscape.

Despite exciting developments in cancer immunotherapy, its broad application is limited by the paucity of targetable antigens on the tumor cell surface. As an intrinsic cellular pathway, nonsense-mediated decay (NMD) conceals neoantigens through the destruction of the RNA products from genes harboring truncating mutations. We developed and conducted a high throughput screen, based on the ratiometric analysis of transcripts, to identify critical mediators of NMD. This screen implicated disruption of kinase SMG1's phosphorylation of UPF1 as a potential disruptor of NMD. This led us to design a novel SMG1 inhibitor, KVS0001, that elevates the expression of transcripts and proteins resulting from truncating mutations in vivo and in vitro . Most importantly, KVS0001 concomitantly increased the presentation of immune-targetable HLA class I-associated peptides from NMD-downregulated proteins on the surface of cancer cells. KVS0001 provides new opportunities for studying NMD and the diseases in which NMD plays a role, including cancer and inherited diseases. One Sentence Summary: Disruption of the nonsense-mediated decay pathway with a newly developed SMG1 inhibitor with in-vivo activity increases the expression of T-cell targetable cancer neoantigens resulting from truncating mutations.

Hydrophobic interactions dominate the recognition of a KRAS G12V neoantigen.

Specificity remains a major challenge to current therapeutic strategies for cancer. Mutation associated neoantigens (MANAs) are products of genetic alterations, making them highly specific therapeutic targets. MANAs are HLA-presented (pHLA) peptides derived from intracellular mutant proteins that are otherwise inaccessible to antibody-based therapeutics. Here, we describe the cryo-EM structure of an antibody-MANA pHLA complex. Specifically, we determine a TCR mimic (TCRm) antibody bound to its MANA target, the KRASG12V peptide presented by HLA-A*03:01. Hydrophobic residues appear to account for the specificity of the mutant G12V residue. We also determine the structure of the wild-type G12 peptide bound to HLA-A*03:01, using X-ray crystallography. Based on these structures, we perform screens to validate the key residues required for peptide specificity. These experiments led us to a model for discrimination between the mutant and the wild-type peptides presented on HLA-A*03:01 based exclusively on hydrophobic interactions.

13C- and 15N-labeling of amyloid-ß and inhibitory peptides to study their interaction via nanoscale infrared spectroscopy.

Interactions between molecules are fundamental in biology. They occur also between amyloidogenic peptides or proteins that are associated with different amyloid diseases, which makes it important to study the mutual influence of two polypeptides on each other's properties in mixed samples. However, addressing this research question with imaging techniques faces the challenge to distinguish different polypeptides without adding artificial probes for detection. Here, we show that nanoscale infrared spectroscopy in combination with 13C, 15N-labeling solves this problem. We studied aggregated amyloid-ß peptide (Aß) and its interaction with an inhibitory peptide (NCAM1-PrP) using scattering-type scanning near-field optical microscopy. Although having similar secondary structure, labeled and unlabeled peptides could be distinguished by comparing optical phase images taken at wavenumbers characteristic for either the labeled or the unlabeled peptide. NCAM1-PrP seems to be able to associate with or to dissolve existing Aß fibrils because pure Aß fibrils were not detected after mixing.

Allogeneic Blood or Marrow Transplantation with High-Dose Post-Transplantation Cyclophosphamide for Acute Lymphoblastic Leukemia in Patients Age ≥55 Years.

Patients age ≥55 years with acute lymphoblastic leukemia (ALL) fare poorly with conventional chemotherapy, with a 5-year overall survival (OS) of ∼20%. Tyrosine kinase inhibitors and novel B cell-targeted therapies can improve outcomes, but rates of relapse and death in remission remain high. Allogeneic blood or marrow transplantation (alloBMT) provides an alternative consolidation strategy, and post-transplantation cyclophosphamide (PTCy) facilitates HLA-mismatched transplantations with low rates of nonrelapse mortality (NRM) and graft-versus-host disease (GVHD). The transplantation database at Johns Hopkins was queried for patients age ≥55 years who underwent alloBMT for ALL using PTCy. The database included 77 such patients. Most received reduced-intensity conditioning (RIC) (88.3%), were in first complete remission (CR1) (85.7%), and had B-lineage disease (90.9%). For the entire cohort, 5-year relapse-free survival (RFS) and overall survival (OS) were 46% (95% confidence interval [CI], 34% to 57%) and 49% (95% CI, 37% to 60%), respectively. Grade III-IV acute GVHD occurred in only 3% of patients, and chronic GVHD occurred in 13%. In multivariable analysis, myeloablative conditioning led to worse RFS (hazard ratio [HR], 4.65; P = .001), whereas transplantation in CR1 (HR, .30; P = .004) and transplantation for Philadelphia chromosome-positive (Ph+) ALL versus T-ALL (HR, .29; P = .03) were associated with improved RFS. Of the 54 patients who underwent RIC alloBMT in CR1 for B-ALL, the 5-year RFS and OS were 62% (95% CI, 47% to 74%) and 65% (95% CI, 51% to 77%), respectively, with a 5-year relapse incidence of 16% (95% CI, 7% to 27%) and an NRM of 24% (95% CI, 13% to 36%). RIC alloBMT with PTCy in CR1 represents a promising consolidation strategy for B-ALL patients age ≥55 years.

Allogeneic Blood or Marrow Transplantation with Post-Transplantation Cyclophosphamide for Peripheral T Cell Lymphoma: The Importance of Graft Source.

The use of post-transplantation cyclophosphamide (PTCy) for graft-versus host-disease (GVHD) prophylaxis has revolutionized allogeneic blood or marrow transplantation (alloBMT), but there is limited published experience in peripheral T cell lymphoma (PTCL). We sought to assess outcomes in patients with PTCL who underwent alloBMT with PTCy. We reviewed the charts of all adult patients age ≥18 years who underwent alloBMT with nonmyeloablative conditioning and PTCy-based GVHD prophylaxis at the Sidney Kimmel Comprehensive Cancer Center between January 2004 and December 2020. Sixty-five patients were identified. The median age was 59 years (range, 24 to 75 years). Lymphoma histology included PTCL not otherwise specified (n = 24), anaplastic lymphoma kinase-negative anaplastic large cell lymphoma (n = 14), angioimmunoblastic T cell lymphoma (n = 7), enteropathy-associated T cell lymphoma (n = 6), hepatosplenic T cell lymphoma (n = 4), and others (n = 10). Eleven patients were in first complete remission (17%); the remaining patients were in first partial remission or underwent salvage therapy to at least PR prior to transplantation. Forty-eight patients underwent alloBMT from a haploidentical related donor (74%), 10 from a fully matched donor (15%), and 7 from a mismatched unrelated donor (11%). All patients received fludarabine, cyclophosphamide, and total body irradiation (TBI). The graft source was bone marrow (BM) in 46 patients (71%) and peripheral blood (PB) in 19 patients (29%); all patients in the BM cohort received 200 cGy TBI, and most patients in the PB cohort (15 of 19) received 400 cGy TBI. GVHD prophylaxis comprised PTCy, mycophenolate mofetil, and a calcineurin inhibitor or sirolimus. With a median follow-up of 2.8 years (range, 290 days to 14.2 years), the 2-year progression-free survival (PFS) for the entire cohort was 49% (95% confidence interval [CI], 38% to 64%), and the 2-year overall survival (OS) was 55% (95% CI, 44% to 69%). Outcomes were significantly improved in those receiving PB compared to those receiving BM, including a 2-year PFS of 79% (95% CI 63% to 100%) versus 39% (95% CI, 27% to 56%), 2-year OS of 84% (95% CI, 69% to 100%) versus 46% (95% CI, 33% to 63%), and 1-year cumulative incidence of relapse of 5% (95% CI, 0 to 16%) versus 33% (95% CI, 19% to 46%), with no difference in GVHD and nonrelapse mortality. AlloBMT with PTCy is safe and well-tolerated in patients with PTCL. Our data suggest that increasing the TBI dose to 400 cGy and using PB allografts may offer improved disease control and better survival outcomes, though additional studies are needed to confirm these findings.

Structural engineering of chimeric antigen receptors targeting HLA-restricted neoantigens.

Chimeric antigen receptor (CAR) T cells have emerged as a promising class of therapeutic agents, generating remarkable responses in the clinic for a subset of human cancers. One major challenge precluding the wider implementation of CAR therapy is the paucity of tumor-specific antigens. Here, we describe the development of a CAR targeting the tumor-specific isocitrate dehydrogenase 2 (IDH2) with R140Q mutation presented on the cell surface in complex with a common human leukocyte antigen allele, HLA-B*07:02. Engineering of the hinge domain of the CAR, as well as crystal structure-guided optimization of the IDH2R140Q-HLA-B*07:02-targeting moiety, enhances the sensitivity and specificity of CARs to enable targeting of this HLA-restricted neoantigen. This approach thus holds promise for the development and optimization of immunotherapies specific to other cancer driver mutations that are difficult to target by conventional means.

Targeting loss of heterozygosity for cancer-specific immunotherapy.

Developing therapeutic agents with potent antitumor activity that spare normal tissues remains a significant challenge. Clonal loss of heterozygosity (LOH) is a widespread and irreversible genetic alteration that is exquisitely specific to cancer cells. We hypothesized that LOH events can be therapeutically targeted by "inverting" the loss of an allele in cancer cells into an activating signal. Here we describe a proof-of-concept approach utilizing engineered T cells approximating NOT-gate Boolean logic to target counterexpressed antigens resulting from LOH events in cancer. The NOT gate comprises a chimeric antigen receptor (CAR) targeting the allele of human leukocyte antigen (HLA) that is retained in the cancer cells and an inhibitory CAR (iCAR) targeting the HLA allele that is lost in the cancer cells. We demonstrate that engineered T cells incorporating such NOT-gate logic can be activated in a genetically predictable manner in vitro and in mice to kill relevant cancer cells. This therapeutic approach, termed NASCAR (Neoplasm-targeting Allele-Sensing CAR), could, in theory, be extended to LOH of other polymorphic genes that result in altered cell surface antigens in cancers.

Bispecific antibodies targeting mutant RAS neoantigens.

Mutations in the RAS oncogenes occur in multiple cancers, and ways to target these mutations has been the subject of intense research for decades. Most of these efforts are focused on conventional small-molecule drugs rather than antibody-based therapies because the RAS proteins are intracellular. Peptides derived from recurrent RAS mutations, G12V and Q61H/L/R, are presented on cancer cells in the context of two common human leukocyte antigen (HLA) alleles, HLA-A3 and HLA-A1, respectively. Using phage display, we isolated single-chain variable fragments (scFvs) specific for each of these mutant peptide-HLA complexes. The scFvs did not recognize the peptides derived from the wild-type form of RAS proteins or other related peptides. We then sought to develop an immunotherapeutic agent that was capable of killing cells presenting very low levels of these RAS-derived peptide-HLA complexes. Among many variations of bispecific antibodies tested, one particular format, the single-chain diabody (scDb), exhibited superior reactivity to cells expressing low levels of neoantigens. We converted the scFvs to this scDb format and demonstrated that they were capable of inducing T cell activation and killing of target cancer cells expressing endogenous levels of the mutant RAS proteins and cognate HLA alleles. CRISPR-mediated alterations of the HLA and RAS genes provided strong genetic evidence for the specificity of the scDbs. Thus, this approach could be applied to other common oncogenic mutations that are difficult to target by conventional means, allowing for more specific anticancer therapeutics.

Targeting a neoantigen derived from a common TP53 mutation.

TP53 (tumor protein p53) is the most commonly mutated cancer driver gene, but drugs that target mutant tumor suppressor genes, such as TP53, are not yet available. Here, we describe the identification of an antibody highly specific to the most common TP53 mutation (R175H, in which arginine at position 175 is replaced with histidine) in complex with a common human leukocyte antigen-A (HLA-A) allele on the cell surface. We describe the structural basis of this specificity and its conversion into an immunotherapeutic agent: a bispecific single-chain diabody. Despite the extremely low p53 peptide-HLA complex density on the cancer cell surface, the bispecific antibody effectively activated T cells to lyse cancer cells that presented the neoantigen in vitro and in mice. This approach could in theory be used to target cancers containing mutations that are difficult to target in conventional ways.

TCR ß chain-directed bispecific antibodies for the treatment of T cell cancers.

Immunotherapies such as chimeric antigen receptor (CAR) T cells and bispecific antibodies redirect healthy T cells to kill cancer cells expressing the target antigen. The pan-B cell antigen-targeting immunotherapies have been remarkably successful in treating B cell malignancies. Such therapies also result in the near-complete loss of healthy B cells, but this depletion is well tolerated by patients. Although analogous targeting of pan-T cell markers could, in theory, help control T cell cancers, the concomitant healthy T cell depletion would result in severe and unacceptable immunosuppression. Thus, therapies directed against T cell cancers require more selective targeting. Here, we describe an approach to target T cell cancers through T cell receptor (TCR) antigens. Each T cell, normal or malignant, expresses a unique TCR ß chain generated from 1 of 30 TCR ß chain variable gene families (TRBV1 to TRBV30). We hypothesized that bispecific antibodies targeting a single TRBV family member expressed in malignant T cells could promote killing of these cancer cells, while preserving healthy T cells that express any of the other 29 possible TRBV family members. We addressed this hypothesis by demonstrating that bispecific antibodies targeting TRBV5-5 (α-V5) or TRBV12 (α-V12) specifically lyse relevant malignant T cell lines and patient-derived T cell leukemias in vitro. Treatment with these antibodies also resulted in major tumor regressions in mouse models of human T cell cancers. This approach provides an off-the-shelf, T cell cancer selective targeting approach that preserves enough healthy T cells to maintain cellular immunity.

Checkpoint Blockade Treatment May Sensitize Hodgkin Lymphoma to Subsequent Therapy.

BACKGROUND: Targeted therapies and checkpoint blockade therapy (CBT) have shown efficacy for patients with Hodgkin lymphoma (HL) in the relapsed and refractory (R/R) setting, but once discontinued owing to progression or side effects, it is unclear how successful further therapies will be. Moreover, there are no data on optimal sequencing of these treatments with standard therapies and other novel agents. In a multicenter, retrospective analysis, we investigated whether exposure to CBT could sensitize HL to subsequent therapy. MATERIALS AND METHODS: Seventeen centers across the U.S. and Canada retrospectively queried medical records for eligible patients. The primary aim was to evaluate the overall response rate (ORR) to post-CBT treatment using the Lugano criteria. Secondary aims included progression-free survival (PFS), duration of response, and overall survival (OS). RESULTS: Eighty-one patients were included. Seventy-two percent had stage III-IV disease, and the population was heavily pretreated with a median of four therapies before CBT. Most patients (65%) discontinued CBT owing to progression. The ORR to post-CBT therapy was 62%, with a median PFS of 6.3 months and median OS of 21 months. Post-CBT treatment regimens consisted of chemotherapy (44%), targeted agents (19%), immunotherapy (15%), transplant conditioning (14%), chemotherapy/targeted combination (7%), and clinical trials (1%). No significant difference in OS was found when stratified by post-CBT regimen. CONCLUSION: In a heavily pretreated R/R HL population, CBT may sensitize patients to subsequent treatment, even after progression on CBT. Post-CBT regimen category did not impact OS. This may be a novel treatment strategy, which warrants further investigation in prospective clinical trials. IMPLICATIONS FOR PRACTICE: Novel, life-prolonging treatment strategies in relapsed and refractory (R/R) Hodgkin lymphoma (HL) are greatly desired. The results of this multicenter analysis concur with a smaller, earlier report that checkpoint blockade therapy (CBT) use in R/R HL may sensitize patients to their subsequent treatment. This approach may potentially enhance therapeutic options or to bridge patients to transplant. Prospective data are warranted prior to practice implementation. As more work is done in this area, we may also be able to optimize sequencing of CBT and novel agents in the treatment paradigm to minimize treatment-related toxicity and thus improve patient quality of life.

Non-Myeloablative Allogeneic Transplantation with Post-Transplant Cyclophosphamide after Immune Checkpoint Inhibition for Classic Hodgkin Lymphoma: A Retrospective Cohort Study.

: Immune checkpoint inhibitors (ICIs) are approved in relapsed classic Hodgkin lymphoma (cHL). The safety and effectiveness of allogeneic blood or marrow transplantation (alloBMT) in ICI-pretreated patients with cHL remain unclear. The aim of this study is to assess outcomes of patients with cHL receiving ICIs before alloBMT using post-transplantation cyclophosphamide (PTCy) graft-versus-host-disease (GVHD) prophylaxis.  : We performed a retrospective study of relapsed/refractory patients with cHL undergoing alloBMT with PTCy at Johns Hopkins between November 2004 and September 2019. Engraftment, GVHD incidence, nonrelapse mortality, progression-free survival (PFS), and overall survival (OS) were compared between patients receiving pre-alloBMT ICI or standard salvage chemotherapy.  : We identified 105 consecutive relapsed/refractory patients with cHL, of whom 37 (35.2%) received ICIs and 68 (64.7%) received chemotherapy without ICIs (no-ICI) before alloBMT. ICI and no-ICI patients experienced a 3-year estimated OS of 94% versus 78% (hazard ratio [HR], 0.35; 95% confidence interval [CI], 0.08 to 1.56; P = .17) and a 3-year estimated PFS of 90% and 65% (HR, 0.3; 95% CI, 0.09 to 1; P = .05), respectively. We observed no statically significant difference in the 12-month cumulative incidence of acute grade II to IV GVHD or in the 24-month incidence of chronic GVHD.  : ICIs do not increase acute or chronic GVHD incidence compared with salvage chemotherapy. Patients with cHL receiving ICIs prior to alloBMT experienced outstanding PFS and OS. Thus, ICI therapy is safe in patients with cHL when undergoing alloBMT with PTCy and may improve post-alloBMT disease progression and survival.

Checkpoint blockade treatment sensitises relapsed/refractory non-Hodgkin lymphoma to subsequent therapy.

Patients with relapsed/refractory (R/R) non-Hodgkin lymphoma (NHL) have limited options for salvage, and checkpoint blockade therapy (CBT) has little efficacy. Usage in solid malignancies suggests that CBT sensitises tumours to subsequent chemotherapy. We performed the first analysis of CBT on subsequent NHL treatment. Seventeen North American centres retrospectively queried records. The primary aim was to evaluate the overall response rate (ORR) to post-CBT treatment. Secondary aims included progression-free survival (PFS), duration of response (DOR) and overall survival (OS). Fifty-nine patients (68% aggressive NHL, 69% advanced disease) were included. Patients received a median of three therapies before CBT. Fifty-three (90%) discontinued CBT due to progression. Post-CBT regimens included chemotherapy (49%), targeted therapy (30%), clinical trial (17%), transplant conditioning (2%) and chimeric antigen receptor T cell (CAR-T) therapy (2%). The ORR to post-CBT treatment was 51%, with median PFS of 6·1 months. In patients with at least stable disease (SD) to post-CBT, the median DOR was significantly longer than to pre-CBT (310 vs. 79 days, P = 0·005) suggesting sensitisation. Nineteen patients were transplanted after post-CBT therapy. Median overall survival was not reached, nor affected by regimen. Prospective trials are warranted, as this may offer R/R NHL patients a novel therapeutic approach.

Impact of Treatment Beyond Progression with Immune Checkpoint Blockade in Hodgkin Lymphoma.

Atypical response patterns following immune checkpoint blockade (ICB) in Hodgkin lymphoma (HL) led to the concept of continuation of treatment beyond progression (TBP); however, the longitudinal benefit of this approach is unclear. We therefore performed a retrospective analysis of 64 patients treated with ICB; 20 who received TBP (TBP cohort) and 44 who stopped ICB at initial progression (non-TBP cohort). The TBP cohort received ICB for a median of 4.7 months after initial progression and delayed subsequent treatment by a median of 6.6 months. Despite receiving more prior lines of therapy, the TBP cohort achieved longer progression-free survival with post-ICB treatment (median, 17.5 months vs. 6.1 months, p = .035) and longer time-to-subsequent treatment failure, defined as time from initial ICB progression to failure of subsequent treatment (median, 34.6 months vs. 9.9 months, p = .003). With the limitations of a retrospective study, these results support the clinical benefit of TBP with ICB for selected patients.

Allogeneic Haploidentical Blood or Marrow Transplantation with Post-Transplantation Cyclophosphamide in Chronic Lymphocytic Leukemia.

Allogeneic blood or marrow transplantation (allo-BMT) remains the only treatment for chronic lymphocytic leukemia (CLL) with curative potential. Although post-transplantation cyclophosphamide (PTCy) reduces allo-BMT toxicity by decreasing the risk of graft-versus-host disease (GVHD), its effect on CLL allo-BMT outcomes is unknown. We studied 64 consecutive patients with CLL who underwent nonmyeloablative (NMA) haploidentical allo-BMT at Johns Hopkins Sidney Kimmel Comprehensive Cancer Center. In this cohort, the 4-year overall survival was 52% (95% confidence interval [CI], 40% to 68%), and progression-free survival was 37% (95% CI, 26% to 54%). Six patients experienced engraftment failure. PTCy prophylaxis was associated with a modest cumulative incidence of 1-year grade II-IV acute GVHD (27%; %95% CI, 15% to 38%) and %%%2-year chronic GVHD (17%; 95% CI, 7% to 26%). We demonstrate that NMA haploidentical allo-BMT with PTCy is a safe and effective treatment option.