Graft-versus-malignancy Research Articles

Improving Unrelated Donor Equity: Assessing Mismatched Donor Opportunities with Real-World Data in a Minority-Predominant Cohort

Recent advances in graft-versus-host disease (GVHD) prophylaxis including post-transplant cyclophosphamide (PTCy) and abatacept have significantly improved outcomes following HLA-mismatched allogenic hematopoietic stem cell transplantation (allo-HSCT) and have tremendous potential for reducing racial disparities in donor availability. A recent small study employing bone marrow as the source of stem cells showed similar outcomes after 5/8 versus 7/8 matches and is currently being tested in a larger study using peripheral blood stem cells. In this study, we examine real-world alternative donor HSCT options for a minority-predominant cohort in the Bronx, NY, focusing on the availability of lesser-matched (5/8 to 7/8) donors. Records of patients who underwent HLA typing at Montefiore Medical Center (2019 to 2022) were reviewed. The National Marrow Donor Program registry was queried to evaluate the availability of donors with at least 99% likelihood of HLA match at various levels (5/8, 6/8, 7/8, 8/8). Two hundred forty-one patients were included, 70% were non-White. Although the availability of ≥7/8 donors was less common in non-White patients, 100% of patients from each group had at least one or more 5/8 and 6/8 HLA-matched donors and more than 80% of these patients had >100 potential 5/8 and 6/8 HLA-matched donors. There was no statistical difference by race or ethnicity in the mean number of donors at 5/8 and 6/8 HLA-match levels. We demonstrate through real-world data that patients from diverse ethnic and racial backgrounds have access to 5/8 and 6/8 HLA-matched donors for allo-HSCT, potentially eliminating disparities in donor availability and allowing prioritization of other donor selection characteristics such as donor age, sex, ABO, and B leader matching. Further work is needed to study whether the use of mismatched donors offers a more potent graft-versus malignancy effect and optimal GVHD prophylaxis.

Ixazomib Maintenance to Prevent Alloreactivity and Provide Anti-Malignancy Effects Following Nonmyeloablative T-Replete Haploidentical Peripheral Blood Stem Cell Transplantation with Post-Transplant Cyclophosphamide

Inhibition of the ubiquitin-proteasome proteolytic pathway results in extensive immunomodulatory effects, augmenting NK cell cytotoxicity while inhibiting aspects of T-, B- and dendritic cell function. To this end, short course bortezomib has been utilized post-transplant to decrease the risk of graft-versus-host disease (GVHD) while preserving graft-versus-malignancy (GVM) effects (Koreth, Haematologica 2018). We performed a phase II study examining the effects of ixazomib for GVHD prophylaxis (up to 12 cycles), in addition to post-transplant cyclophosphamide and tacrolimus, following the original Baltimore nonmyeloablative haploidentical transplant (HIDT) regimen. We hypothesized that substituting ixazomib for mycophenolate would provide acceptable GVHD control while potentially augmenting GVM. Ixazomib was started on day +5 at a dose of 4mg on days 1, 8, 15 of a 28-day cycle, with dose reductions allowed in future cycles for toxicity and mycophenolate, used for conventional post-HIDT GVHD prophylaxis, was eliminated. Donors were selected to maximize NK alloreactivity (i.e. B/x KIR haplotype). Twenty-five patients were enrolled, median age 62 (range 35-77) years, with acute leukemia [4], MDS [7], NHL/HL/CLL [8] and myeloma [6]. Comorbidity index (HCT-CI) was ≥3 in 68%. Donor KIR haplotype was B/x and A/A in 18 and 7 patients respectively. After a median follow-up of 33.5 months (range 9.2-52.8), 19 patients survive with an estimated 1- and 3-year overall survival of 84% and 74% respectively. Engraftment occurred in all patients with no secondary graft failure. Median time to ANC>500 and PLT>20 was 16 and 29 days respectively. CMV reactivation was frequent occurring in 88% of CMV-seropositive patients, however there was no cases of CMV disease. Infectious mortality occurred in 3 patients (disseminated adenovirus, HHV6 encephalitis and fungal pneumonia). The 3-yr cumulative incidence of non-relapse mortality (NRM) was 12% but was significantly higher when the donor possessed the more inhibitory KIR A/A vs. stimulatory B/x haplotype (43% vs. 0%). Relapse incidence at 1- and 3-years was 24% and 44%. Cumulative incidence of Grade 3-4 acute GVHD at day +180 was 8%, while 2-year moderate-to-severe chronic GVHD occurred in 21%. Hematologic and cutaneous toxicities possibly related to ixazomib were common, resulting in dose reductions and treatment interruptions in most patients. Median number of ixazomib cycles was 3 (range 1-12), with only one patient receiving all 12 planned cycles. Rash, at least possibly related to ixazomib, was particularly frequent occurring in 19 (76%) patients at a median day +32 (range, 17-139) following transplant. Reasons for early ixazomib discontinuation included rash [9], cytopenias [7], relapse/progression [4], GVHD [2], diarrhea [1] and arthralgias [1]. In conclusion, the substitution of ixazomib for mycophenolate post-HIDT is feasible and results in reliable engraftment with low rates of clinically significant GVHD and NRM, without any appreciable effect on relapse protection. The occurrence of rash in the first several months in three quarters of patients was unexpected and made it difficult to distinguish drug toxicity from low-grade skin-only acute GVHD. The finding that Infectious mortality occurred exclusively in recipients of KIR A/A haplotype donors is interesting and requires further study. Figure Disclosures Solh: Celgene: Speakers Bureau; Amgen: Speakers Bureau; ADC Therapeutics: Research Funding. OffLabel Disclosure: Use of ixazomib for GVHD prophlaxis following haploidentical transplantation.

Exploiting autoimmunity unleashed by low-dose immune checkpoint blockade to treat advanced cancer.

As a result of the cancer immunotherapy revolution, more than 2000 immuno-oncology agents are currently being tested or are in use to improve responses. Not unexpectedly, the 2018 Nobel Prize in Physiology or Medicine was awarded to James P. Allison and Tasuku Honjo for their development of cancer therapy by the blockade of co-inhibitory signals. Unfortunately, manipulation of the co-inhibitory receptors has also resulted in a safety issue: widespread iatrogenic immune-related adverse events (irAEs). Autoimmunity is emerging as the nemesis of immunotherapy. Originally, it was assumed that CTLA-4 blockade selectively targets T cells relevant to the antitumour immune response. However, an uncontrolled pan T cell activation was induced compromising tolerance to healthy self-tissues. The irAEs are very similar to that of a chronic graft-versus-host-disease (GVHD) reaction following allogeneic bone marrow transplantation (BMT). We hypothesized that ipilimumab induced a graft-versus-malignancy (GVM) effect, which eradicated metastatic melanoma in a minority of patients, but also involved an auto-GVHD reaction that resulted in widespread autoimmunity in the majority. Therefore, we argued for a profound theoretical point against the consensus of experts. The task is not to desperately put the genie back in the bottle by immune-suppressive treatments, but instead to harness the autoimmune forces. In this way, the same goal could be achieved by an antibody as by the adoptive transfer of alloreactive donor lymphocytes, but without severe GVHD. The proof-of-principle of a low-dose-combination immune checkpoint therapy, consisting only of approved drugs and treatments, was demonstrated in 111 stage IV cancer patients.

PB2332 NK‐CELLS REGENERATION AS A PART OF IMMUNOLOGICAL REGENERATION AFTER AUTOLOGOUS STEM CELLS TRANSPLANTATION

Background:Natural killer (NK) cells have gained increasing focus in the field of stem cells transplantation, with a number of discoveries that NK cells can play critical roles in immune responses, e.g. by mediating graft‐versus‐malignancy (GVM) responses.Aims:The study was conducted with the aim to monitoring and analyze the dynamics of NK‐cell population reconstruction after autologous stem cells transplantation.Methods:Samples from 58 patients (27 male and 31 female) with median age 31.4 years (14‐58) as well as 28 age‐matched control samples were studied by a lymphoid oriented panel of antibodies and flow cytometry in nine different points for a period of 24 months. The absolute count (AC) and % of NK‐cells were determined. The group included patients with lymphoma (n = 32); leukemia (n = 7); solid tumors (n = 12) and multiple myeloma (n = 7). According to the disease status at transplantation, 17 patients were in complete response (CR) and very good partial response (VGPR), 31 in PR and 10 in progression.Results:The mean AC of CD56+ NK‐cells was 314 cells/μl in the control group (p5 ‐ 164 cells/μl; p95 ‐ 718 cells/μl) and the mean % was 14% (p5 ‐ 7%; p95 ‐ 26%). In general, patients’ levels of CD56+ NK‐cells (% and AC) before ASCT were low, around the p5 values (mean 10.76% and AC 102.78 cells/μl). The % values increased after +2 month (mean 12.387%), however, values approached the mean values of the control group at +24 month. No significant correlation was found between the level of hematological reconstitution and NK‐cells (% and AC). The AC NK‐cells 30 days after ASCT statistically correlated with CD19+ B‐cells reconstitution (r = 0.3465; p<0.05). As a whole, regardless of the fluctuations, the % NK‐cells remained below the control average but within the range of p5‐p95 in patients >20 years of age, while in patients <20 years the % remained closer to the lower limit during the entire period. The recovery of the AC showed similar dynamics in all age groups and after +18 month remained below p5 only in the group < 20 years. According to the diagnosis, only patients with solid tumors demonstrated higher % values before the ASCT (mean 14.16%), while after the transplantation all except myeloma patients showed recovery within the control ranges. Certain differences in the recovery dynamics were observed according to the disease status at transplantation. In patients, transplanted in CR and VGPR, after the decrease (mean 8.23 ± 6.05% and AC 58.96 ± 61.045 cells/μl) at +1 month, values showed a sharp increase at +2 month (mean 12.23 ± 8.26% and AC 110.709 ± 8.727cells/μl). The same was found in patients transplanted in progression (from mean 7.37 ± 6.69% and AC 34.913 ± 53.145 cells/μl to mean 8.31 ± 2.63% and AC 104.106 ± 57.117 cells/μl). In patients with PR, the lowest levels were recorded at +3 month (mean 9.71 ± 5.43% % and AC 101.071 ± 49.973 cells/μl). Further, we compared two conditioning regimens in lymphoma patients: BEAM (n = 15) and LACE (n = 10) and found differences in the recovery after +6 month. The % NK‐cells in the BEAM group decreased from +6 to +9 month and then increased from +18 to +24 month, while in the LACE group there was a sharp decline later from +9 to +18 month and an increase thereafter, however staying within the reference interval throughout the follow‐up period.Summary/Conclusion:NK‐cells population showed faster reconstruction after ASCT in comparison to other lymphoid populations. The process of recovery depends more on age‐related factors than on diagnosis, disease status at transplantation or the conditioning therapy.

Sequential Cyclophosphamide and Trametinib Improve Clinical Graft Versus Host Disease and Survival in Murine Hematopoietic Stem Cell Transplant

Background Ongoing acute graft versus host disease (aGVHD) after allogeneic stem cell transplantation (alloSCT) causes significant morbidity and mortality with no standard therapy except corticosteroids, which are broadly immunosuppressive and toxic. Cyclophosphamide (Cy) given day 3 and day 4 is effective for prophylaxis of aGVHD but has proven ineffective when given later as in ongoing aGVHD in both murine and human studies. We previously demonstrated that the MEK inhibitor trametinib (Tram) is effective for aGVHD prophylaxis in murine models of aGVHD through the novel mechanism of inhibition of naive T cells (CD44−CD62L+). Our hypothesis is that ongoing aGVHD could be better inhibited by sequential Cy and post-Cy Tram inhibition (to prevent naive T cells from re-initiating alloreactivity) without compromising graft-versus-malignancy (GVM) responses. Methods Mice were administered sequential Cy and Tram post SCT starting day 12. Efficacy of treatment was assessed in a murine model of MHC-mismatched alloSCT. Overall survival was assessed and clinical GVHD was scored three times weekly. Peripheral blood, spleen, and lymph node cells phenotypes were determined by flow cytometry. GVM was also assessed with A20 luciferase/YFP (A20luc/YFP) lymphoma cells imaged with in vivo imaging system (IVIS). Results Overall survival following sequential Cy and Tram was identical to that seen with T cell depleted bone marrow alone and significantly superior to treatment using either single-agent Cy or Tram (p Conclusions Combination cyclophosphamide and trametinib demonstrates superior overall survival and limits GVHD severity without affecting regulatory T cells or GVM in murine allogeneic stem cell models. Utilizing Cy and Tram are readily translatable and support the notion that clinical approaches can be developed in the future.

Donor Lymphocyte Infusions Used to Treat Mixed-Chimeric and High-Risk Patient Populations in the Relapsed and Nonrelapsed Settings after Allogeneic Transplantation for Hematologic Malignancies Are Associated with High Five-Year Survival if Persistent Full Donor Chimerism Is Obtained or Maintained

Mixed chimerism (MC), a persistent or increasing number of host cells after allogeneic hematopoietic stem cell transplantation (HSCT), is a predictor of disease relapse. Donor lymphocyte infusions (DLI) have the potential to enhance the graft-versus-malignancy (GVM) effect, reducing the risk of relapse in patients with MC. Hence, in addition to utilizing DLI in the relapsed setting, there is a motivation to pursue pre-emptive DLI for patients in complete remissions after HSCT. To assess the safety and efficacy of DLI, records of 86 patients who received DLI between 2003 and 2015 at a single institution were studied retrospectively. Patients who received DLI included 50 patients with relapsed/residual (RR) disease, 29 patients with emerging MC without detectable disease, and 7 patients in an “other” cohort who had neither RR disease nor emerging MC after HSCT. DLI were administered using a dose-escalation protocol. After DLI, 93% of MC patients converted to full donor chimerism (FDC). Nonrelapsed patients (MC and other) reported high overall survival (OS) at 1 and 5 years (83% at 1 year, 70% at 5 years for MC; 86% at 1 year, 69% at 5 years for other) and was statistically superior to 5-year OS for RR patients (nonrelapsed 69% versus RR 28%; P = .00032). Improved survival correlated with successful conversion to FDC after DLI for RR and MC cohorts: 71% 2-year OS for patients converted to FDC versus 13% for patients who failed to achieve FDC (P < .0001). DLI for nonrelapsed patients was associated with a superior 5-year progression-free survival (PFS) of 71% compared with 18% 5-year PFS in the RR group (P < .0001). Relapse/progressive disease was the most frequent cause of death (41%). Seven MC (24%), 2 other (29%), and 39 RR patients (78%) relapsed or did not respond after DLI. Overall, 6 patients (7%) died of graft-versus-host disease after DLI. Our results demonstrate a successful dose-escalation approach for nonrelapsed patients that correlated with high survival and a high rate of achieving FDC in MC and RR populations. DLI remain a viable option to boost the GVM effect in the relapsed setting and may pre-emptively protect against relapse in MC populations after HSCT.

Lineage Specific Chimerism Analysis Reveals That Mixed Donor T-Cell Chimerism Is Common in the Early Post-Transplant Period Following Myeloablative Allotransplants from HLA-Matched but Not HLA-Haploidentical Donors: A Multivariable Analysis of Allografted Patients from a Single Center

Failure to achieve complete donor T-cell chimerism in the early post-transplant period may impair the graft-versus malignancy effect and contribute to a higher risk of disease relapse. Lineage specific chimerism analysis (LSCA) of T-lymphocytes versus myeloid cells is routinely performed following reduced-intensity or non-myeloablative hematopoietic cell allografts. However, many centers do not perform LSCA following myeloablative conditioning. We performed LSCA in all consecutive patients receiving a first T-replete allotransplant using myeloablative conditioning as defined by the CIBMTR (Giralt 2009 BBMT 15;367) between 2/2006 and 2/2015 (n=232; patient characteristics: median age 49 (18-73); Female 50%, Black 19%, Asian 3% white 78%; donor MRD 41%, MUD 39%, Haploidentical 20%; graft PBSC 88%, BM 11.5%, both 0.5%; diagnosis AML 52%, ALL 18%, MDS 11%, CML 11%, NHL 4% MPS1%, CLL1%, HL 1%; DRI low 10%, intermediate 51%, high 29%, very high 10%. Our objectives were to determine the rate of full-donor and mixed T-cell chimerism in the early post-transplant period (d 30 and d 90) , to determine the association of T-cell chimerism with patient, disease and regimen specific factors, and to determine whether early mixed chimerism impacts post-transplant outcomes following myeloablative conditioning. LSCA was performed on peripheral blood using a RoboSep instrument for automated sorting of CD3-positive T-cells and CD33 positive myeloid cells to 96.5-100% and 98.3-100% purity respectively, and short tandem repeat analysis by PCR. Full donor chimerism was defined as > 90% donor derived cells. Probability of achieving full donor T-cell chimerism in evaluable patients on d 30 and d 90 post transplant were 55% and 71%. In contrast the probabilities of achieving full-donor myeloid chimerism were 99.5% and 93.5% respectively. On univariate analysis the following factors were significantly associated with achievement of full-donor T-cell chimerism on d 30: donor type (haploidentical 100%, MRD 39%, MUD 47%, p<0.001), diagnosis (AML 58%, ALL 60%, MDS/MPS/CML 35%, NHL/HL/CLL 90%, p=0.003), conditioning regimen (busulfan based 37%, TBI based 56%, post-transplant Cy 100%, p<0.001), and on d 90: donor type (haploidentical 100%, MRD 56%, MUD 70%, p<0.001), diagnosis (AML 76%, ALL 77%, MDS/MPS/CML 49%%, NHL/HL/CLL 100%, p=0.002), conditioning regimen (busulfan based 56%, TBI based 77%, post-transplant Cy 100%, p<0.001). For multivariate analysis (Table 1) the exact logistic regression method was used to accommodate the nature of the data. The odds ratios (OR) were estimated by exponentiating median unbiased estimates of regression coefficients. Donor type (haploidentical vs other) and diagnosis (MDS/MPS vs AML) were significant factors. Our institutional approach to patients failing to achieve full-donor chimerism by d 90 is to withdraw immnosuppressive therapy in the absence of active GVHD if T-cell chimerism is > 50% or to administer DLI (starting at 1 x 10e6 CD3+ cells/kg) for patients with CD3 chimerism < 50% . Using this approach long term outcomes for patients who failed to achieve full-donor CD3 chimerism by d 30 were not significantly different from those achieving this threshold (2 yr estimated survival -81% vs 67%; disease-free survival 62%% vs 57%; 6 month CI of grade 2-4 acute GVHD 33% vs 41%; 2 yr CI of non-relapse mortality 9% vs 15%, relapse 29% vs 28%; p=NS for all). These data demonstrate that failure to induce early full-donor T-cell chimerism is relatively common following myeloablative allotransplantation using HLA-matched but not haploidentical donors. Although spontaneous improvement can occur, routine LSCA followed by immunologic manipulation of patients with suboptimal chimerism may assist in preventing adverse long term outcomes.Table 1D 30 - OR = odds ratio of achieving full-donor CD3 chimerismFactorEffectOR95% CIP valueDiagnosisALL vs AML0.980.36 - 2.651.000MDS/MPS/CML vs AML0.370.13 - 0.940.035NHL/HD/CLL vs AML5.220.48 - 2700.255DonorTypeMRD vs MUD0.630.29 - 1.350.266Haploidentical vs MUD57.312.0 - ∞<0.001Table 2OR = odds ratio of achieving full-donor CD3 chimerismFactorEffectOR95% CIP valueDiagnosisALL vs AML0.700.20 - 2.490.719MDS/MPS/CML vs AML0.150.04 - 0.48<0.001NHL/HD/CLL vs AML3.870.68 - ∞0.216Donor TypeMRD vs MUD0.350.12 - 0.980.045Haplo vs MUD19.03.64 - ∞<0.001 DisclosuresNo relevant conflicts of interest to declare.

Myxoma virus suppresses proliferation of activated T lymphocytes yet permits oncolytic virus transfer to cancer cells

AbstractAllogeneic hematopoietic cell transplant (allo-HCT) can be curative for certain hematologic malignancies, but the risk of graft-versus-host disease (GVHD) is a major limitation for wider application. Ideally, strategies to improve allo-HCT would involve suppression of T lymphocytes that drive GVHD while sparing those that mediate graft-versus-malignancy (GVM). Recently, using a xenograft model, we serendipitously discovered that myxoma virus (MYXV) prevented GVHD while permitting GVM. In this study, we show that MYXV binds to resting, primary human T lymphocytes but will only proceed into active virus infection after the T cells receive activation signals. MYXV-infected T lymphocytes exhibited impaired proliferation after activation with reduced expression of interferon-γ, interleukin-2 (IL-2), and soluble IL-2Rα, but did not affect expression of IL-4 and IL-10. MYXV suppressed T-cell proliferation in 2 patterns (full vs partial) depending on the donor. In terms of GVM, we show that MYXV-infected activated human T lymphocytes effectively deliver live oncolytic virus to human multiple myeloma cells, thus augmenting GVM by transfer of active oncolytic virus to residual cancer cells. Given this dual capacity of reducing GVHD plus increasing the antineoplastic effectiveness of GVM, ex vivo virotherapy with MYXV may be a promising clinical adjunct to allo-HCT regimens.

Pushing the envelope-nonmyeloablative and reduced intensity preparative regimens for allogeneic hematopoietic transplantation.

Allogeneic hematopoietic cell transplantation (HCT) was originally developed to allow delivery of myeloablative doses of chemotherapy and radiotherapy. With better understanding of disease pathophysiology, the graft vs malignancy (GVM) effect of allogeneic hematopoietic transplantation and toxicities associated with myeloablative conditioning (MAC) regimens, the focus shifted to developing less toxic conditioning regimens to reduce treatment-related morbidity without compromising survival. Although HCT with MAC is preferred to reduced intensity conditioning (RIC) for most patients ⩽60 years with AML/myelodysplastic syndrome and ALL, RIC and nonmyeloablative (NMA) regimens allow HCT for many otherwise ineligible patients. Reduced intensity preparative regimens have produced high rates of PFS for diagnoses, which are highly sensitive to GVM. Relapse of the malignancy is the major cause of treatment failure with RIC/NMA HCT. Incorporation of novel agents like bortezomib or lenalidomide, addition of cellular immunotherapy and use of targeted radiation therapies could further improve outcome. In this review, we discuss commonly used RIC/NMA regimens and promising novel regimens.

Proceedings from the National Cancer Institute's Second International Workshop on the Biology, Prevention, and Treatment of Relapse after Hematopoietic Stem Cell Transplantation: Part I. Biology of Relapse after Transplantation

In the National Cancer Institute's Second Workshop on the Biology, Prevention, and Treatment of Relapse after Hematopoietic Stem Cell Transplantation, the Scientific/Educational Session on the Biology of Relapse discussed recent advances in understanding some of the host-, disease-, and transplantation-related contributions to relapse, emphasizing concepts with potential therapeutic implications. Relapse after hematopoietic stem cell transplantation (HSCT) represents tumor escape, from the cytotoxic effects of the conditioning regimen and from immunologic control mediated by reconstituted lymphocyte populations. Factors influencing the biology of the therapeutic graft-versus-malignancy (GVM) effect—and relapse—include conditioning regimen effects on lymphocyte populations and homeostasis, immunologic niches, and the tumor microenvironment; reconstitution of lymphocyte populations and establishment of functional immune competence; and genetic heterogeneity within the malignancy defining potential for clonal escape. Recent developments in T cell and natural killer cell homeostasis and reconstitution are reviewed, with implications for prevention and treatment of relapse, as is the application of modern genome sequencing to defining the biologic basis of GVM, clonal escape, and relapse after HSCT.

Treosulfan: reduced toxicity conditioning for allogeneic stem cell transplantation in acute myeloid leukemia and myelodysplastic syndrome

Allogeneic hematopoietic stem cell transplant (SCT) is a potentially curative treatment for a variety of hematological malignancies. The therapeutic effect of SCT depends on both the administration of high-dose chemo-radiotherapy and the induction of the graftversus-malignancy (GvM) effect by imCorrespondence: Arnon Nagler Hematology Division Chaim Sheba Medical Center Tel Hashomer, Israel, 52621 E-mail: a.nagler@sheba.health.gov.il

Promising Role of Reduced-Toxicity Hematopoietic Stem Cell Transplantation (PART-I)

Allogeneic hematopoietic stem cell transplantation (HSCT) remains a potential curative option for many patients with hematological malignancies (HM). However, the high rate of transplantation-related mortality (TRM) restricted the use of standard myeloablative HSCT to a minority of young and fit patients. Over the past few years, it has become evident that the alloreactivity of the immunocompetent donor cells mediated anti-malignancy effects independent of the action of high dose chemoradiotherapy. The use of reduced intensity conditioning (RIC) regimens has allowed a graft-versus-malignancy (GvM) effect to be exploited in patients who were previously ineligible for HSCT on the grounds of age and comorbidity. Retrospective analysis showed that RIC has been associated with lower TRM but a higher relapse rate leading to similar intermediate term overall and progression-free survivals when compared to standard myeloablative HSCT. However, the long term antitumor effect of this approach is less well established. Prospective studies are ongoing to define which patients might most benefit from reduced toxicity stem cell transplant (RT-SCT) and which transplant protocols are suitable for the different types of HM. The advent of RT-SCT permits the delivery of a potentially curative GvM effect to the majority of patients with HM whose outcome with conventional chemotherapy would be dismal. Remaining challenges include development of effective strategies to reduce relapse rates by augmenting GvM effects without increasing toxicity.

Interesting possibilities to improve the safety of ipilimumab.

e13102 Background: The problem of the ipilimumab therapy is that a common molecular target (CTLA-4 receptor) is expressed on the targeted and non-targeted T cells, respectively. We suggest that the frequency of immune-related adverse events can be reduced by treating conditions in which the number of the targeted cells is larger than the non-targeted ones and/or by improving the accuracy of the targeting. Methods: The first approach was tested in a phase I clinical trial in patients with relapsed malignancy following allogeneic hematopoietic stem cell transplantation. An ipilimumab blockade was used against CTLA-4 positive allogeneic T cells (responding patients had greater than 80% donor T-cell chimerism). The graft-versus-malignancy (GVM) effects were augmented without a significant impact on graft-versus-host disease (GVHD). A feasible approach could also be pretargeting that has been worked out for radioimmunodetection and radioimmunotherapy. To this end we suggest a testable thought experiment for the treatment of chronic lymphocytic leukemia (CLL). First a streptavidin (StAv) modified anti-CD19 mAb is administered, which is followed by the subsequent delivery of biotin labeled anti-CTLA-4 mAb. The latter endows T cells with the ability to travel to tumor sites without prematurely succumbing to apoptosis, while streptavidin’s ultra-high affinity for biotin (10-15M) ensures a tight bond to the biotin labeled anti-CTLA-4. Results: Using the law of mass action we calculated that above 1 mg/L ipilimumab concentration (i.e. about 5 mg/patient ~70kg) more than 80% of anti-CD19-StAv sensitized B cells will have been bound to anti-CTLA-4-biotin sensitized T cells. Conclusions: This way, the forces of the immune system liberated by the anti-CTLA-4 antibody blockade could be focused with laser sharp accuracy on CLL cells without collateral damage to normal host cells. One should note that 0.3 mg/kg ipilimumab alone already caused mild autoimmunity.

Immune Reactions following Cord Blood Transplantations in Adults

Cord blood transplantation (CBT) is an attractive alternative therapy in adult patients with advanced hematological malignancies in whom matched donors are unavailable. However, the risk of complications, especially infections, post-CBT increases the mortality rates in these patients. Although the incidence of acute and chronic graft versus host disease (GVHD) post-CBT is lower than that following bone marrow transplantation and peripheral blood stem cell transplantation (SCT), the additional immunosuppressive therapy required to treat it could increase the mortality in these patients. Further, chronic GVHD following CBT is milder and responds better to treatment than that occurring after bone marrow transplants. Unlike bone marrow transplantation, the onset of GVHD is a positive prognostic indicator of overall survival in patients receiving CBT, due to the graft versus malignancy (GVM) effect. This paper focuses on the immune reactions following CBT and aims to elucidate a management strategy for acute and chronic GVHD.

CTLA-4 Blockade following Relapse of Malignancy after Allogeneic Stem Cell Transplantation Is Associated with T Cell Activation But Not with Increased Levels of T Regulatory Cells

Cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) is a key negative regulator of T cell activation and proliferation. Ipilimumab is a human monoclonal antibody that specifically blocks the binding of CTLA-4 to its ligand. To test the hypothesis that blockade of CTLA-4 by ipilimumab could augment graft-versus-malignancy (GVM) effects without a significant impact on graft-versus-host disease (GVHD), we conducted a phase I clinical trial of ipilimumab infusion in patients with relapsed malignancy following allogeneic hematopoietic stem cell transplantation (allo-HSCT). Here, we report the analysis of peripheral blood T lymphocyte reconstitution, T regulatory cell (Treg) expression, and T cell activation markers after a single dose of ipilimumab in 29 patients. Peripheral blood samples were collected from all patients before and after ipilimumab infusion. Lymphocyte immunophenotyes, including levels of CD4(+)CD25(high) cells and T cell activation markers, were analyzed in all cases. Levels of CD4(+)CD25(high)Foxp3(+) cells and intracellular CTLA-4 in CD4(+) T cells also were evaluated in the last 11 cases. We found lower baseline levels of CD4(+) and CD45RO(+) T cells in patients compared with normal controls. More than 50% of the patients had abnormally low lymphocyte counts (CD4 or/and CD8 T cells), and some had no circulating B lymphocytes. The percentages of both CD4(+)CD25(high) and CD4(+)CD25(high)Foxp3(+) T cells were significantly higher in patients before ipilimumab infusion than in healthy donors. Twenty of 29 patients exhibited an elevated level of CD4(+)CD25(low) activated T cells at baseline, compared with only 3 of 26 healthy donors. Both CD4(+) and CD8(+) T lymphocyte counts were significantly increased after ipilimumab infusion. There was no consistent change in absolute lymphocyte count or in the number of T cells expressing the activation marker CD69. However, increases in CD4(+)CD25(low) T cells were seen in 20 of 29 patients and increases in CD4(+)HLA-DR(+) T cells were seen in the last 10 patients in the first 60 days after ipilimumab infusion. Although the percentages of both CD4(+)CD25(high) and CD4(+)CD25(high)Foxp3(+) T cells decreased significantly during the observation period, the absolute cell counts did not change. Intracellular CTLA-4 expression in CD4(+)CD25(lo/-) T cells increased significantly after ipilimumab infusion. We conclude that CTLA-4 blockade by a single infusion of ipilimumab increased CD4(+) and CD4(+)HLA-DR(+) T lymphocyte counts and intracellular CTLA-4 expression at the highest dose level. There was no significant change in Treg cell numbers after ipilimumab infusion. These data demonstrate that significant changes in T cell populations occur on exposure to a single dose of ipilimumab. Further studies with multiple doses are needed to explore this phenomenon further and to correlate changes in lymphocyte subpopulations with clinical events.

The Role of Missing Killer Cell Immunoglobulin-Like Receptor Ligands in T Cell Replete Peripheral Blood Stem Cell Transplantation from HLA-Identical Siblings

The contribution of natural killer (NK) cells to graft-versus-malignancy (GVM) effects following hematopoietic stem cell transplantation (HSCT) remains uncertain, particularly in the HLA-identical setting. A model considering missing HLA ligands to the donor's inhibitory killer cell immunoglobulin-like receptor (KIR), termed the missing KIR ligand model, has been established in T cell depleted bone marrow transplantation (BMT), but lacks validity in other cohorts with different treatment characteristics. We hypothesized that the impact of missing KIR ligands on relapse-free survival (RFS) and overall survival (OS) in T cell replete peripheral blood SCT (PBSCT) differs from that in the T cell depleted BMT setting, and retrospectively evaluated 100 consecutive, HLA-identical sibling transplantations for hematologic malignancies. In addition to KIR ligand status, we considered the donors' activating KIRs and grafted NK, T, and CD34(+) cell doses. Our findings demonstrate noninferiority for OS (P = .005) and RFS (P = .002) for the heterozygous HLA-C group KIR ligand status (C1/2; n = 47) compared with patients missing either C1 or C2 (n = 53). Similarly, OS (P = .031) and RFS (P = .034) of Bw4-positive patients was noninferior to that of patients missing a Bw4 ligand to KIR3DL1. By multivariate analysis, C1/2 heterozygous patients had a favorable risk ratio (RR) for relapse (RR = 0.28; P = .003), RFS (RR = 0.56; P = .046), and acute graft-versus-host disease grade II-IV (RR = 0.36; P = .05). Following reduced-intensity conditioning (RIC), but not standard-intensity conditioning, myeloablative (MA) transplantation, a grafted NK cell dose above the median (3.4 x 10(7)/kg) was associated with a lower risk of relapse (RR = 0.57; P = .003) and improved survival (RR = 0.78; P = .03). Overall, our findings support a role for NK alloreactivity in HLA-identical HSCT, but argue against a favorable impact of missing KIR ligands in the given setting. We conclude that the mechanism favoring the missing KIR ligand constellation in T cell depleted BMT may not operate in T cell replete PBSCT. The reasons for this differential effect remain unresolved.

CTLA4 blockade with ipilimumab to treat relapse of malignancy after allogeneic hematopoietic cell transplantation

AbstractRelapse of malignancy after allogeneic hematopoietic cell transplantation (allo-HCT) remains a therapeutic challenge. Blockade of the CTLA4 molecule can effectively augment antitumor immunity mediated by autologous effector T cells. We have assessed the safety and preliminary efficacy of a neutralizing, human anti-CTLA4 monoclonal antibody, ipilimumab, in stimulating the graft-versus-malignancy (GVM) effect after allo-HCT. Twenty-nine patients with malignancies that were recurrent or progressive after allo-HCT, received ipilimumab as a single infusion at dose cohorts between 0.1 and 3.0 mg/kg. Dose-limiting toxicity was not encountered, and ipilimumab did not induce graft-versus-host disease (GVHD) or graft rejection. Organ-specific immune adverse events (IAE) were seen in 4 patients (grade 3 arthritis, grade 2 hyperthyroidism, recurrent grade 4 pneumonitis). Three patients with lymphoid malignancy developed objective disease responses following ipilimumab: complete remission (CR) in 2 patients with Hodgkin disease and partial remission (PR) in a patient with refractory mantle cell lymphoma. At the 3.0 mg/kg dose, active serum concentrations of ipilimumab were maintained for more than 30 days after a single infusion. Ipilimumab, as administered in this clinical trial, does not induce or exacerbate clinical GVHD, but may cause organ-specific IAE and regression of malignancy. This study is registered at http://clinicaltrials.gov under NCI protocol ID P6082.

Autologous graft-versus-host disease: harnessing anti-tumor immunity through impaired self-tolerance

The absence of a graft-versus-malignancy (GVM) effect may be responsible for the higher relapse rate seen after autologous hematopoietic cell transplantation (auto-HCT) compared with allogeneic hematopoietic cell transplantation (allo-HCT). Acute GVHD developing after allo-HCT, however, is associated with significant morbidity and mortality. An autoimmune syndrome similar to acute GVHD has been reported to occur after auto-HCT and has been termed the 'auto-aggression' syndrome or autologous GVHD (auto-GVHD). Auto-GVHD tends to be milder than classical GVHD, most commonly involves the skin (rarely the gastrointestinal tract, liver or both) and often is self-limited. Auto-GVHD has been reported to occur both spontaneously and in subjects receiving post transplant immune modulation with CsA, IFN-gamma or the combination. The development of auto-GVHD depends upon the derangement of self tolerance either through administration of post transplant CsA, depletion of regulatory T cells following the preparative chemoradiotherapy or both. Self-reactive CD8(+) T cells paradoxically are able to recognize a self peptide antigen presented by MHC class II molecules and appear to mediate the syndrome. Many clinical trials have been performed using CsA with or without IFN-gamma in an attempt to induce auto-GVHD. While many patients do indeed develop the syndrome, any associated anti-tumor effect remains questionable to date. New strategies to exploit auto-GVHD and enhance a GVM effect such as through the depletion of regulatory T cells or through use of newer immunomodulatory agents may improve the efficacy of auto-HCT.

Acute Graft-Versus-Host Disease Following Umbilical Cord Blood Transplantation: Retrospective Survey Involving 2015 Japanese Patients.

BACKGROUND Limited information is available on incidences and clinical features of acute graft-versus host disease (GVHD) after cord blood transplantation and large-sized researches have been awaited.METHODS We investigated the incidences and clinical features of acute GVHD in 2,015 patients reported to the Japan Cord Blood Bank Network, who underwent cord blood transplantation between June 1997 and August 2006.RESULTS Of 2,015 patients, 1481 patients (73%) achieved neutrophil engraftment at a median of day 22 (range, 6–81). Cumulative incidence of neutrophil recovery at day 100 was 0.74 (95%CI, 0.73–0.76). Of 2015 patients, 708 patients developed grade II-IV acute GVHD: grade II (n=423), grade III (n=237), and grade IV (n=48). The median onset was day 19 (range, 4–190). The cumulative incidences of grade II-IV and III-IV acute GVHD at day 100 were 0.35 (95% CI, 0.33–0.37) and 0.14 (95% CI, 0.12–0.15), respectively. Skin and gastrointestinal acute GVHD was documented in 1,006 and 405 patients, respectively, whereas liver GVHD was diagnosed in 149 patients. Multivariate analysis identified the following predictors of grade II-IV acute GVHD: the number of infused nucleated cells, transplantation from female donors to female recipients, TBI-containing preparative regimens, methotrexate-containing GVHD prophylaxis, and tacrolimus-based GVHD prophylaxis. Overall survival rates at three years of patients with grade 0-I, II and III-IV GVHD who survived 100 days or longer were 0.58 (95%CI, 0.53–0.63), 0.61 (95% CI, 0.54–0.67) and 0.40 (95%CI, 0.31–0.49), respectively.CONCLUSIONS Acute GVHD following cord blood transplantation is mild and has graft-versus malignancy effects. [Display omitted]

Association of serum interleukin-7 and interleukin-15 levels with immune reconstitution (IR), graft-versus-host disease (GVHD), and survival after reduced-intensity allogeneic stem cell transplantation (RIST)

7107 Background: In laboratory models, interleukin-7 (IL-7) and IL-15 significantly influence IR after allogeneic stem cell transplantation (SCT), thereby affecting immunity, graft-versus-malignancy (GVM) effects, and GVHD. Interleukin-7 (IL-7) is the main homeostatic regulator of naïve CD4+ and CD8+ T cells, and IL-15 is homeostatic for CD8+ memory and effector T cells and NK cells. The contributions of these cytokines to IR after allogeneic SCT are not well characterized in a clinical setting. Methods: We studied serum IL-7 and IL-15 levels in 31 pts with hematologic malignancies undergoing RIST from HLA-matched siblings in a prospective trial. Pts received identical transplant conditioning (fludarabine/cyclophosphamide) and GVHD prophylaxis (CSA/MTX). IL-7 and IL-15 levels and peripheral blood lymphocyte subpopulations (ALC, CD3, CD4, CD8, B, NK, and NKT) were measured before RIST, and post RIST at 1 and 2 weeks; 1, 2, 3, 6, 9, and 12 months. Results: Consistent with their homeostatic effects, IL-7 and IL-15 levels rose from baseline as transplant conditioning induced lymphopenia, and then decreased with lymphocyte recovery. These inverse correlations were strongest within 1 month post RIST. In an exploratory analysis, IL-15 levels at day 0 were correlated with baseline age (r=0.49; p=0.0058) and were higher among patients with CMV reactivation after RIST (p=0.048). At 2 weeks post RIST, higher IL-7 levels were strongly associated with subsequent acute GVHD (p=0.000033), and higher IL-15 levels were associated with inferior survival (p=0.007), mainly from relapse. At 3 months post RIST, superior survival was associated with higher NK cell counts (p=0.0008), and to a lesser extent with higher CD4 counts (p=0.036). Conclusions: These data support preclinical observations that IL-7 promotes GVHD after allogeneic SCT. The association of higher post-RIST IL-15 levels with death from relapse may identify pts with impaired IR leading to inadequate GVM effects. This hypothesis is consistent with the finding that higher NK cell counts after RIST were associated with better survival. Further studies must confirm the hypotheses generated in this setting. No significant financial relationships to disclose.