Phase <scp>II</scp> clinical trial of one dose of post‐transplant cyclophosphamide for graft versus host disease prevention following myeloablative, peripheral blood stem cell, matched‐unrelated donor transplantation
Authors: Omer Jamy, Raquel Innis‐Shelton, Susan Bal, Ravi Paluri, Donna Salzman, Antonio Di Stasi, Luciano Costa, Ruby Meredith, Lawrence Lamb, Kentaro Minagawa, Shin Mineishi, Ayman Saad
Journal: American Journal of Hematology (2021)

Graft versus host disease (GVHD) is a major complication in human leukocyte antigen (HLA) matched allogeneic hematopoietic stem cell transplantation (allo-HSCT). Pharmacologic GVHD prophylaxis typically include calcineurin inhibitors, mycophenolate mofetil (MMF), methotrexate, and sirolimus. Other methods for GVHD prophylaxis include T-cell depletion, however, these approaches could increase the risk of infections and relapse, and potentially have variable results of delayed immune reconstitution.1-3 Two doses of post-transplant cyclophosphamide (PTCy) have shown efficacy as GVHD prophylaxis in haploidentical (haplo)-HSCT. Extrapolating from its success in haplo-HSCT, PTCy has also demonstrated its effectiveness as a single agent in myeloablative HLA-matched-related and unrelated bone marrow transplant,2, 3 and in combination with other immunosuppressive agents in reduced-intensity peripheral blood stem cell (PBSC) transplant.4, 5 Furthermore, the combination of PTCy with other agents has retrospectively been found to be effective in myeloablative PBSC transplants.1 However, initial studies with two doses of PTCy, in the reduced intensity setting, raised concern for increased risk of relapse.6 Furthermore, PTCy may increase the risk of infectious complictions, particularly cytomegalovirus (CMV) infection.7 In the effort of balancing between GVHD and graft versus tumor effect, one dose of PTCy has been tested. In non-myeloablative haploidentical bone marrow transplant, there was a trend towards higher extensive chronic GVHD (cGVHD) with one dose, when compared to two doses. There was no significant difference in the incidence of infection.8 Whether one dose of PTCy is sufficient for GVHD prophylaxis in myeloablative, matched-unrelated PBSC transplant, remains unclear. We conducted a single-arm phase II clinical trial of one dose of PTCy, tacrolimus, and MMF for GVHD prophylaxis following myeloablative, matched-unrelated, PBSC allo-HSCT. The trial was registered with clinicaltrials.gov (NCT02065154). The primary endpoint of the study was the cumulative incidence (CI) of grade II-IV acute GVHD (aGVHD) at Day 100 post-transplant. Secondary endpoints included cumulative incidence of cGVHD, overall survival (OS), progression-free survival (PFS), relapse, and non-relapse related mortality (NRM). Details regarding eligibility, preparative regimens, GVHD prophylaxis, diagnosis and treatment, supportive care and statistical analysis are provided in Appendix S1. Thirty-nine patients were enrolled between September 2013 and June 2018. Demographic and clinical characteristics are detailed in Table S1. Thirty-six donors were 8/8 HLA matched unrelated, and three were 7/8 matched (A mismatch = 1, B mismatch = 1, C mismatch = 1) unrelated. The trial was later amended to exclude patients with 7/8 match with evolving data showing more effective GVHD control by using the traditional two doses of PTCy. There was one death, prior to engraftment, within the first 30 days. The remaining 38 (97%) patients successfully engrafted. The median time to ANC and platelet engraftment was 12 days (range 9–14 days) and 33 days (range 28–54 days), respectively. The 1-year data for donor chimerism and immune reconstitution are provided in Figures S1A, S1B, respectively. The CI of grades II-IV and III-IV aGVHD at Day 100 post-transplant was 30% (95% CI 15.2%–40.1%) (Figure 1A) and 5% (95% CI 2.1%–8.2%) (Figure 1B), respectively (Table S2). There were two patients with grade IV aGVHD (lower gastrointestinal tract involvement) and none with grade III. The 2-year CI of mild, moderate, and severe cGVHD was 15% (95% CI 7.1%–23.3%), 15% (95% CI 8.4%–23.3%) and 18% (95% CI 12.6%–27.4%), respectively. For patients with cGVHD, skin was the most common organ involved (n = 9). Six patients had liver GVHD (Bu/Flu = 6), whereas four had lung involvement (Bu/Flu =3, Cy/TBI =1). There was no significant difference in the occurrence of acute and chronic GVHD for age at diagnosis (≥60 years vs. <60 years and ≥55 years vs. <55 years), gender, conditioning regimen (Bu/Flu vs. others, TBI vs. non-TBI), disease (AML vs. others), DRI (high vs. others) and HLA-typing (8/8 vs. 7/8). The 2-year CI of relapse and NRM was 21% (95% CI 7.6%–33.4%) and 34% (95% CI 18.6%–49.6%), respectively (Figure S2). There were four non-relapse related deaths prior to Day 100 post-transplant. Three of those patients were >60 years old. One patient died before neutrophil engraftment. The cause of death in the remaining three patients was sepsis (Enterococcus faecalis = 1, Staphylococcus epidermidis = 1, organism unidentified = 1), leading to multi-organ failure. For patients expiring beyond Day 100 post-transplant, the most common causes of death were cGVHD (13%) followed by infection without underlying GVHD (5%). In patients dying from cGVHD, the leading secondary causes of death included respiratory failure due to underlying lung GVHD and infection. The 2-year estimate of PFS and OS was 45% (95% CI 29.5%–61.3%) and 51% (95% CI 34.7%–66.5%), respectively. The median OS was 36 months (95% CI 0–71.8 months) with a median follow up of 50 months (range 6–71 months) (Figure S3). Three patients had 7/8 matched-unrelated donors. The first patient, with MDS, developed grade II aGVHD of the skin at Day 35 and relapsed at Day 105 with transition to hospice due to poor functional status. The second patient developed moderate cGVHD with skin, ocular, joint/fascia and genital tract involvement. The patient remains disease-free and is receiving investigational treatment for cGVHD. The third patient developed grade II aGVHD of the skin at Day 70 and extensive cGVHD with skin and oral involvement at 2-year. The patient remains disease and GVHD-free. Note, CMV reactivation occurred in 18% of patients, and BK viruria occurred in 5% of patients. A list of non-hematological and non-infectious grades 3–4 toxicities up to Day 100 post-transplant is provided in Table S3. Our findings indicate that the use of a modified strategy of one dose PTCy in myeloablative, unrelated, PBSC transplant results in a low incidence of severe aGVHD without compromising relapse risk. However, this regimen does not appear to mitigate the risk of cGVHD compared to standard pharmacologic prophylaxis, including two doses of PTCy. The low incidence of severe aGVHD observed in our study is comparable to previous trials utilizing PTCy in various settings. The incidence of GVHD is reportedly higher with myeloablative allo-HSCT. Kanakry et al., reported a 60% CI of grades II-IV and 19% CI of grades III-IV aGVHD with two doses of PTCy, as a single agent, in myeloablative, matched-unrelated bone marrow transplant.2 Luznik et al., using two doses of single agent PTCy in myeloablative matched-related and unrelated bone marrow transplant, reported an incidence of 43% and 10% for grades II-IV and III-IV aGVHD, respectively.3 Moiseev et al., reported a CI of 19% and 4% for grades II-IV and III-IV, respectively, with two doses of PTCy, tacrolimus, and MMF, in unrelated PBSC transplant. About 65% of the patients in that study received reduced-intensity conditioning, which was independently associated with a lower incidence of aGVHD.4 In comparison to the current literature, we show that one dose of PTCy was effective in controlling aGVHD in myeloablative, unrelated, PBSC transplants. The rates of moderate and severe cGVHD in our study do not seem to be different than those observed with conventional pharmacologic GVHD prophylaxis with myeloablative PBSC transplants. On the other hand, results of studies with two doses of PTCy, in different platforms, have shown excellent control of cGVHD.2-5 The discrepancy among studies is likely not only related to the number of PTCy doses, but also to the type of donors (related vs. unrelated), HLA-matching status, conditioning regimen intensity, and graft source (bone marrow vs. PBSC). The 2-year relapse risk was 21% in our cohort, that included about one-third of patients with persistent disease at the time of transplant, and a large proportion with intermediate or high-risk disease. The reported incidence of relapse with PTCy has ranged from 19% to 46% using different conditioning intensity and donor sources.2-5 The balance between impairing alloreactive T-cells and preserving Tregs with PTCy may determine the risk of both GVHD and relapse in this setting. However, several studies have now shown that there does not appear to be an increased risk of relapse with PTCy.5 Our reported NRM rate was comparable to prior reports of myeloablative PBSC transplant.4 Mortality before Day 100 in our study was primarily seen in patients >60 years old and attributed to sepsis rather than organ dysfunction. Beyond Day 100, cGVHD was the main cause of death. A recent CIBMTR analysis reported a 1-year NRM and cGVHD rate of 15% and 25%, respectively, in myeloablative, matched-unrelated donor transplant using two doses of PTCy.9 Extrapolating from these results, it is possible that two doses of PTCy would have resulted in lower NRM rates due to better cGVHD control compared to one dose, especially in a myeloablative, matched-unrelated, PBSC transplant. We acknowledge the limitations of our study, being a single center with a relatively small sample size. Although we find one dose of PTCy to be effective in terms of aGVHD control and low incidence of relapse, we do not find a significant advantage with this strategy to improve the overall outcomes of myeloablative PBSC transplant and perhaps two doses are needed for better outcomes. To the best of our knowledge, our study is the first report to describe outcomes of myeloablative, matched-unrelated, PBSC transplant with one dose of PTCy. It serves as a platform to further investigate PTCy in larger such trials. The authors declare no conflict of interest. Omer Jamy, Ayman Saad and Shin Minieshi contributed towards the conception of the presented study. Omer Jamy, Raquel Innis-Shelton, Susan Bal, Ravi Paluri, Antonio Di Stasi, Ruby Meredith, Luciano Costa and Lawrence Lamb contributed towards data collection and analysis. Omer Jamy, Raquel Innis-Shelton, Susan Bal, Antonio Di Stasi, Ruby Meredith, Luciano Costa, Lawrence Lamb, Donna Salzman, Kentaro Minagawa, Shin Minieshi and Ayman Saad contributed towards drafting, revising, and approving the manuscript. The data that support the findings of this study are available on request from the corresponding author. Table S1. Demographic & clinical characteristics Table S2. GvHD Table S3. Day 100 grades III-IV non-infectious, non-hematological toxicities Appendix S1. Supporting Information Figure S1A. Median donor chimerism data for CD3 and CD15 at Day 28, Day 84, Day 175 and Day 365. Figure S1B. Immune reconstitution profile (CD3, CD4, CD8, CD16+56) at Day 28, Day 84, Day 175 and Day 365 Figure S2. 1 & 2-year relapse and non-relapse related mortality Figure S3. Progression-free and overall survival Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.