Phase II Study of Myeloablative 7-8/8-Matched Allotransplantation with Post-Transplantation Cyclophosphamide, Tacrolimus, and Mycophenolate Mofetil

Update in GVHD Prophylaxis: Novel Pharmacologic and Graft Manipulation Strategies

Prevention of graft-versus-host disease (GVHD) is critical to successful allogeneic hematopoietic cell transplantation (HCT), but for many years was difficult to achieve. Advances in the understanding of allogeneic HCT biology and immunology have paved the way for novel clinical approaches to GVHD prophylaxis, highlighted by the broad adoption of posttransplant cyclophosphamide and the approval of abatacept by the US Food and Drug Administration to prevent acute GVHD. Patients undergoing allogeneic HCT are now experiencing severe acute GVHD at historically low rates, and significant improvements in preventing chronic GVHD are also being achieved. This review highlights key pharmacological approaches and graft manipulation strategies being used or investigated for GVHD prophylaxis. Furthermore, we discuss the ongoing unmet needs in GVHD prevention and the challenges in addressing these areas in future clinical trials.

GVHD prophylaxis in matched related stem cell transplantation: Why post-transplant cyclophosphamide can be recommended a study by the EBMT transplant complications working party

Rabbit anti-thymocyte globulin (rATG) reduced chronic GVHD after matched related donor (MRD) allogeneic stem cell transplantation (alloSCT) from 69% to 32% in a randomized trial and is the recommended standard in Europe. Post-transplantation Cyclophosphamide (PTCy) is an emerging alternative but lacks such solid data in MRD alloSCT. We therefore analyzed outcomes of rATG (n = 4140) vs. PTCy (n = 1069) in adult patients with hematologic malignancies undergoing MRD alloSCT between 2017 and 2021 in the EBMT database. The provided hazard ratios (HR) and P-values are adjusted for potential risk factors using multivariate analysis. Results are given at 2 years after alloSCT for all endpoints except for acute GVHD (100 days). The main difference was a lower relapse incidence after PTCy vs. rATG (26.2% vs. 32.8%; HR 0.78 [CI 95%: 0.66-0.92], p = 0.003). Interaction analyses confirmed the consistency of this result across different disease risk index and conditioning intensity subgroups. Other major transplant outcomes showed no significant differences: non-relapse mortality, overall survival, progression-free survival, GVHD-free relapse-free survival, incidence and severity of acute GVHD as well as chronic GVHD. In summary, PTCy results in comparable GVHD and survival outcomes but lower relapse rates compared to rATG. We conclude that PTCy can be recommended in MRD alloSCT.

Immune reconstitution dynamics after unrelated allogeneic transplantation with post-transplant cyclophosphamide compared to classical immunosuppression with anti-thymocyte globulin: a prospective cohort study

Post-transplant cyclophosphamide (PTCy) has contributed to the success of haploidentical hematopoietic stem cell transplantation (HSCT) and is also used in transplantation from matched donors. However, limited data on the immune reconstitution after this type of immunosuppression is available. We aimed to evaluate immune reconstitution after HSCT from unrelated donors, comparing anti-thymocyte globulin (ATG) and PTCy. Consecutive patients undergoing HSCT from unrelated donors and receiving either ATG or PTCy were prospectively included. Immune reconstitution analyses were performed by flow cytometry pre-transplant and on days 30, 60, 90, and 180 post-transplant. We included 36 patients, 20 in the ATG group and 16 in the PTCy group. In the early post-transplant period (day [d]+30), the ATG group showed a higher number of total lymphocytes, T, B, and natural killer (NK) cells compared to the PTCy group. However, at d+180, the PTCy group exhibited a higher number of B cells. On d+60 and d+90, the ATG group displayed higher number of NK cells CD56dim compared to the PTCy group, while on d+180, the PTCy group showed higher number of CD56-, CD16+, and, NKG2D+ NK cells. Naive CD4+, transition CD4+, and naive CD8+ T cells on d+60 were identified as risk factors for acute graft-versus-host disease grade 2-4, and a higher count of CD4+ memory cells on d+180 was identified as a risk factor for chronic graft-versus-host disease. In the context of unrelated allogeneic transplantation, immunosuppression with PTCy was associated with later B-, T- and NK-cell reconstitution compared to ATG.

Contemporary Updates in the Prevention and Treatment of Graft-Versus-Host Disease

PURPOSE OF REVIEW

Graft-versus-host disease (GVHD) is a serious complication after allogeneic HCT. Recently, several pivotal studies have been conducted demonstrating significant improvements in the management of GVHD. Here, we review important trials pertaining to GVHD prevention, acute GVHD treatment, and treatment of steroid refractory acute and chronic GVHD.

RECENT FINDINGS

Clinical trials in preventing GVHD demonstrate lower rates of severe acute GVHD and chronic GVHD with post-transplant cyclophosphamide. For acute GVHD, lower risk acute GVHD appears amenable to steroid-sparing therapies, such as sirolimus and itacitinib. Combinations with novel agents such as itolizumab appear promising for high risk acute GVHD. For steroid-refractory acute GVHD, ruxolitinib should be considered first line therapy. For chronic GVHD requiring therapy beyond steroids, ruxolitinib, belumosudil, and ibrutinib are now available and should be considered. Increasingly, GVHD has become a manageable complication after allogeneic HCT potentially translating to greater success with allogeneic HCT in the future.

JAK2/mTOR inhibition fails to prevent acute GVHD despite reduced Th1/Th17 cells: final phase 2 trial results

ABSTRACT

Our phase 1 graft-versus-host disease (GVHD) prevention trial of JAK2 inhibitor, pacritinib (PAC; recommended phase 2 dose: 100 mg orally twice a day on day 0 to +70) plus sirolimus and tacrolimus (SIR/TAC) demonstrated the regimen was safe and free of pan-JAK myelosuppression after allogeneic hematopoietic cell transplantation (alloHCT). PAC inhibits interleukin 6 (IL-6) receptor activity and pathogenic T helper cell 1 (Th1)/Th17 differentiation in preclinical models and the phase 1 trial. Herein, we report on our completed phase 2 trial of PAC/SIR/TAC after 8/8 human leukocyte antigen matched alloHCT. This single-arm phase 2 trial (NCT02891603) was powered to determine if PAC/SIR/TAC suppressed percentage phosphorylated STAT3 (pSTAT3)+ CD4+ T cells at day +21 (primary end point: percentage pSTAT3+ CD4+ T cells ≤ 35%) and estimated grade II to IV acute GVHD by day +100. The impact of PAC/SIR/TAC on T-cell subsets, CD28 (pS6 and pH3ser10), and IL-2 receptor (pSTAT5) signal transduction was also evaluated. Eligible patients (n = 28) received alloHCT for hematologic malignancies or myeloproliferative neoplasms. Reduced or myeloablative intensity conditioning was permitted. PAC/SIR/TAC met the primary end point, reducing percentage pSTAT3+ CD4+ T cells to 9.62% at day +21. Th1/Th17 cells were decreased at day +21, increasing the ratio of regulatory T cells to Th1 and Th17 cells with PAC/SIR/TAC at recommended phase 2 dose PAC compared with dose level 1 PAC. The cumulative incidence of grade II to IV acute GVHD by day +100 with PAC/SIR/TAC was similar to historic SIR/TAC values (46% vs 43%). Although PAC/SIR/TAC suppressed pSTAT3 and Th1/Th17 cells, the regimen did not improve acute GVHD prevention.

Comparable relapse incidence after unrelated allogeneic stem cell transplantation with post-transplant cyclophosphamide versus conventional anti-graft versus host disease prophylaxis in patients with acute myeloid leukemia: A study on behalf of the Acute Leukemia Working Party of the European Society for Blood and Marrow Transplantation

We compared relapse incidence (RI) post-unrelated transplantation with post-transplant cyclophosphamide (PTCy) versus no PTCy graft-versus-host disease (GVHD) prophylaxis, in 7049 acute myeloid leukemia (AML) patients in remission, 707 with PTCy, and 6342 without (No PTCy). The patients in the PTCy group were younger, 52.7 versus 56.6 years (p < .001). There were more 9/10 donors in the PTCy group, 33.8% versus 16.4% (p < .001), and more received myeloablative conditioning, 61.7% versus 50.2% (p < .001). In the No PTCy group, 87.7% of patients received in vivo T-cell depletion. Neutrophil and platelet engraftment were lower in the PTCy versus No PTCy group, 93.8% and 80.9% versus 97.6% and 92.6% (p < .001). RI was not significantly different in the PTCy versus the No PTCy group, hazard ratio (HR) of 1.11 (95% confidence interval [CI] 0.9-1.37) (p = .31). Acute GVHD grades II-IV and III-IV, were significantly lower in the PTCy versus the No PTCy group, HR of 0.74 (95% CI 0.59-0.92, p = .007) and HR = 0.56 (95% CI 0.38-0.83, p = .004), as were total and extensive chronic GVHD, HRs of 0.5 (95% CI 0.41-0.62, p < .001) and HR = 0.31 (95% CI 0.22-0.42, p < .001). Non-relapse mortality (NRM) was significantly lower with PTCy versus the No PTCy group, HR of 0.67 (95% CI 0.5-0.91, p = .007). GVHD-free, relapse-free survival (GRFS) was higher in the PTCy versus the No PTCy group, HR of 0.69 (95% CI 0.59-0.81, p = .001). Leukemia-free survival (LFS) and overall survival (OS) did not differ between the groups. In summary, we observed comparable RI, OS, and LFS, significantly lower incidences of GVHD and NRM, and significantly higher GRFS in AML patients undergoing unrelated donor-hematopoietic stem cell transplantation with PTCy versus No PTCy GVHD prophylaxis.

Antiviral Agents for Preventing Cytomegalovirus Disease in Recipients of Hematopoietic Cell Transplantation

This systematic review discusses the use of prophylaxis to prevent cytomegalovirus (CMV) infection in recipients who have undergone hematopoietic cell transplantation. It highlights the need for new approaches to control and prevent CMV infection. The approval of the anti-CMV drug letermovir has made antiviral prophylaxis more popular. CMV-specific T cell-mediated immunity tests are effective in identifying patients who have undergone immune reconstitution and predicting disease progression. Maribavir (MBV) has been approved for the treatment of post-transplant CMV infection/disease in adolescents. Adoptive T-cell therapy and the PepVax CMV vaccine show promise in tackling refractory and resistant CMV. However, the effectiveness of PepVax in reducing CMV viremia/disease was not demonstrated in a phase II trial. Cell-mediated immunity assays are valuable for personalized management plans, but more interventional studies are needed. MBV and adoptive T-cell therapy are promising treatments, and trials for CMV vaccines are ongoing.

Treatment-Responsive Acute Graft-versus-Host Disease after Post-Transplantation Cyclophosphamide-Based Prophylaxis: Incidence and Clinical Outcomes

Post-transplantation cyclophosphamide (PTCy) following hematopoietic cell transplantation (HCT) has emerged as standard of care for graft-versus-host disease (GVHD) prevention in adult patients without increasing malignant relapse. We previously defined acute GVHD (aGVHD) treatment response categories as corticosteroid-sensitive (SS), -dependent (SD), or -resistant (SR) based on response to first-line corticosteroids and reported their clinical outcomes following non-PTCy-based prophylaxis. More than one-third of patients developed aGVHD necessitating systemic therapy. Cases were predominantly SR, with a 14% overall incidence of SR aGVHD. The incidence and clinical outcomes of these 3 distinct aGVHD treatment response groups following PTCy-based prophylaxis have not been well described. The objective of this retrospective single-institution cohort study was to assess the incidence and clinical outcomes of SS, SD, and SR aGVHD following HCT with PTCy-based prophylaxis using a prophylactic regimen of PTCy, tacrolimus, and mycophenolate mofetil (MMF). We included 196 consecutive adult and pediatric patients undergoing allogeneic HCT for malignant and non-malignant disorders at the University of Minnesota between 2017 and 2021. Patients received PTCy on days +3 and +4 plus tacrolimus and MMF prophylaxis. Bone marrow and peripheral blood stem cell graft sources and related and unrelated donors were included. Recipients received myeloablative or reduced-intensity conditioning regimens. Of the 196 allografts, 54 (28%) developed aGVHD before day +180, with a median time to onset of 50 days (interquartile range, 34 to 71 days). Of those, 32 patients (16% overall) developed maximum grade II-III aGVHD necessitating systemic corticosteroids, with the following response: 13 SS (41%), 10 SD (31%), and 9 SR (28%). The overall incidence of SR aGVHD was 4.6%. Only 12 patients (6%) developed maximum grade III aGVHD, and none had grade IV aGVHD. The 2-year overall survival analyzed from 80 days after initiation of systemic treatment was similar in the SS and SD groups (77 and 75%, respectively), comparable to those without aGVHD (81%), and was lowest in the SR group (20%), with GVHD the primary cause of death. Nonrelapse mortality was highest in the SR group. MN high-risk and higher GVHD grade at onset were risk factors for developing SR aGVHD. Overall, we report a low incidence (16%) of aGVHD requiring systemic corticosteroids with PTCy-based prophylaxis. aGVHD cases were predominantly SS aGVHD, with lower incidences of SD and SR aGVHD. Our findings suggest that PTCy-based prophylaxis reduces the rate of treatment-resistant aGVHD. Patients with SR aGVHD had the worst clinical outcomes and poorest survival. Those with SS and SD aGVHD had similar clinical outcomes, both better than seen with SR aGVHD.

Potential of Fecal Microbiota Transplantation to Prevent Acute GVHD: Analysis from a Phase II Trial

PURPOSE

Intestinal microbiota disruptions early after allogeneic hematopoietic cell transplantation have been associated with increased risk for acute GVHD (aGVHD). In our recent randomized phase II trial of oral, encapsulated, third-party fecal microbiota transplantation (FMT) versus placebo, FMT at the time of neutrophil recovery was safe and ameliorated dysbiosis. Here, we evaluated in post hoc analysis whether donor microbiota engraftment after FMT may protect against aGVHD.

EXPERIMENTAL DESIGN

We analyzed pre- and post-FMT stool samples and estimated donor microbiota engraftment (a preplanned secondary endpoint) by determining the fraction of post-FMT microbiota formed by unique donor taxa (donor microbiota fraction; dMf).

RESULTS

dMf was higher in patients who later developed grade I or no aGVHD (median 33.9%; range, 1.6%-74.3%) than those who developed grade II-IV aGVHD (median 25.3%; range, 2.2%-34.8%; P = 0.006). The cumulative incidence of grade II-IV aGVHD by day 180 was lower in the group with greater-than-median dMf than the group with less-than-median dMf [14.3% (95% confidence interval, CI, 2.1-37.5) vs. 76.9% (95% CI, 39.7-92.8), P = 0.008]. The only determinant of dMf in cross-validated least absolute shrinkage and selection operator (LASSO)-regularized regression was the patient's pre-FMT microbiota diversity (Pearson correlation coefficient -0.82, P = 1.6 × 10-9), indicating more potent microbiota modulation by FMT in patients with more severe dysbiosis. Microbiota network analysis revealed major rewiring including changes in the most central nodes, without emergence of keystone species, as a potential mechanism of FMT effect.

CONCLUSIONS

FMT may have protective effects against aGVHD, especially in patients with more severe microbiota disruptions.

Graft-versus-host disease: teaching old drugs new tricks at less cost

Graft-versus-host disease (GVHD) remains a major cause of morbidity and mortality after allogeneic stem cell transplantation (SCT). Currently, more patients can receive SCT. This is attributed to the use of reduced intensity regimens and the use of different GVHD prophylaxis that breaks the barrier of human leukocyte antigen, allowing an increase in the donor pool. Once an area with relatively few clinical trial options, there has been an increase in interest in GVHD prophylaxis and treatment, which has led to many US Food and Drug Administration (FDA) approvals. Although there is considerable excitement over novel therapies, many patients may not have access to them due to geographical or other resource constraints. In this review article, we summarize the latest evidence on how we can continue to repurpose drugs for GVHD prophylaxis and treatment. Drugs covered by our review include those that have been FDA approved for other uses for at least 15 years (since 2008); thus, they are likely to have generic equivalents available now or in the near future.