CD34 Cell Dose Research Articles

Real World Experience using Cidofovir in BK Polyomavirus Haemorrhagic Cystitis following Stem Cell TransplantationAre Generics Equally Efficacious?

Introduction: BK Polyomavirus induced Haemorrhagic Cystitis (BKPyV-HC), a well-recognised complication following Haematopoietic Cell Transplantation (HCT), is associated with increased organ dysfunction and mortality. The treatment is a multipronged strategy which includes manipulating immunosuppression and antiviral therapy along with newer advances of virus specific cellular therapy. Cidofovir is a nucleotide analogue of Cytosine that is effective against many Deoxyribonucleic Acid (DNA) viruses and its use has been limited in the past because of cost and toxicity. Aim: To capture real world data on the use of cidofovir in BKPyVHC, post HCT especially with regard to dosage, efficacy, toxicity and predictors of response to therapy. The study compared the efficacy and safety of the innovator molecule of cidofovir with Generic versions. Materials and Methods: This study was a retrospective cohort of 67 patients, who were diagnosed with BKPyV-HC post haematopoietic stem cell transplant, and were treated with cidofovir. The study was conducted at a tertiary care centre at Vellore, Tamil Nadu, India, between 2015 and 2021. BKPyV Polymerase Chain Reaction (PCR) was checked in urine routinely in alternate donor transplants, and if there were typical lower urinary tract symptoms or haematuria in any other transplant setting. Treatment with cidofovir (initially innovator an subsequently generic) was as per physician’s discretion. Results: 985 patients underwent Allogeneic HCT during the study period, of which 67 had BKPyV-HC and were treated with cidofovir (47 with Innovator molecule, 20 with Generic molecule). There was clinical resolution in 47 (70.1%) and mortality in 32 (47.8%) of the cohort. On univariate analysis, risk factors associated with mortality were an absence of clinical resolution (p<0.001), treatment initiation at a higher grade of HC (p=0.032), CD34 cell dose >9x106 /Kg (p=0.029), partial remission of malignancy at the time of transplant (p=0.001), ≤3 doses of cidofovir used (p=0.036), BK log value >log 7 at the time of stopping cidofovir (p=0.021) and toxicity with cidofovir (p=0.036). However, only the absence of clinical resolution was significantly associated (p<0.001) with mortality risk on multivariate analysis. There was no significant difference between the two comparator molecules of cidofovir. Conclusion: Cidofovir is an effective and safe therapeutic option to treat BKPyV-HC with no significant differences seen between the innovator and Generic molecule of Cidofovir in this small series of patients.

Cytokine Release Syndrome Following Peripheral Blood Stem Cell Haploidentical Hematopoietic Cell Transplantation with Post-Transplantation Cyclophosphamide

Post-transplantation cyclophosphamide (PTCy) is a safe and efficacious graft-versus-host-disease (GVHD) prophylaxis following hematopoietic cell transplantation (HCT) from a haploidentical (haplo) donor. Cytokine release syndrome (CRS) is a common complication of this platform. Early fever post-haplo-HCT using bone marrow grafts is associated with higher CD3+ cell dose and CRS. However, the impact of CD3+ and CD34+ cell dose on CRS post-haplo-HCT using peripheral blood stem cell (PBSC) grafts is unknown. Our goals were to evaluate the incidence of CRS following PBSC transplantation (PBSCT) and to identify factors that can be modified to prevent the development of severe CRS in this setting. In 271 patients, we investigated factors associated with the development of CRS following haplo-PBSCT and examined the impact of CRS on clinical outcomes. Ninety-three percent of the patients developed CRS of any grade post-haplo-PBSCT. In multivariate analysis, severe CRS (grade 3-4 versus grade 0-1) was associated with higher nonrelapse mortality (hazard ratio [HR], 6.42; 95% confidence interval [CI], 2.68 to 15.39; P < .001), worse 1-year overall survival (HR, 3.40; 95% CI, 1.63 to 7.08; P=.005), and worse disease-free survival (HR, 4.02; 95% CI, 1.99 to 8.08; P < .001). Moderate to severe CRS (grade 2-4) did not impact 1-year relapse or acute GVHD (grade II-IV and III-IV) at 100 days (P=.71 and .19, respectively). Importantly, higher CD3+ cell dose, but not CD34+ cell dose, predicted a higher incidence of grade 2-4 CRS (HR, 1.20; 95% CI,1.07 to 1.36; P=.003) and grade 3-4 CRS (HR, 1.40; 95% CI, 1.05 to 1.86; P=.022). Both older age (HR, 8.57; 95% CI, 1.73 to 42.36; P < .001) and non-total body irradiation-based reduced-intensity conditioning with fludarabine/melphalan (HR, 15.38; 955 CI, 2.06 to 114.67; P < .001) were predictive of grade 3-4 CRS. Overall, we observed that severe CRS (grade 3-4) negatively affected transplantation outcome, and that higher CD3 cell dose was associated with the development of any grade CRS and severe CRS.

Association of CD34 Cell Dose with 5-Year Overall Survival after Peripheral Blood Allogeneic Hematopoietic Cell Transplantation in Adults with Hematologic Malignancies

Higher CD34 cell dose is associated with improved engraftment after peripheral blood allogeneic hematopoietic stem cell transplantation (alloHCT) but also may increase the risk of long-term complications, such as graft-versus-host disease (GVHD). Prior studies examining the relationship between CD34 cell dose and long-term survival outcomes have yielded conflicting results. In this study, we sought to clarify the prognostic impact of CD34 cell dose by examining a large contemporary cohort of patients undergoing alloHCT with a matched sibling peripheral blood stem cell (PBSC) donor. We retrospectively examined the impact of CD34 cell dose on overall survival (OS), neutrophil engraftment, platelet engraftment, treatment-related mortality, relapse, acute GVHD grade II-IV and III-IV, and chronic GVHD in 377 consecutive patients undergoing alloHCT with a PBSC graft source from a matched sibling donor at the University of Minnesota between 2002 and 2015. The patients were classified into 3 groups based on the tertile (T) of CD34 cell dose received: T1, <5×106 cells/kg; T2, 5 to 7.5×106 cells/kg; and T3, ≥7.5×106 cells/kg. Multivariable analysis demonstrated that high CD34 cell dose was associated with superior 5-year OS (hazard ratio [HR], 0.57; P=.01) and more rapid platelet engraftment (HR, 1.70; P < .01). Higher CD34 cell dose also was associated with improved absolute neutrophil count engraftment (T2: HR, 1.54; T3: HR, 1.52; P < .01). There was no association between CD34 cell dose and TRM or relapse at 5 years. Although higher CD34 cell dose was not associated with acute GVHD grade II-IV, it was associated with chronic GVHD (T2: HR, 1.68; T3: HR, 1.50; P=.04). Our data indicate that higher CD34 cell dose (>7.5×106/kg) is associated with superior OS at 5 years and improved engraftment but carries an increased risk of chronic GVHD. These data support a target CD34 cell dose goal of 7.5×106/kg for sibling PBSC graft donors.

Updated Outcomes during the Pandemic: Relationship between CD34and CD3 Cell Doses, One-Year Graft-Versus-Relapse-Free-Survival, Graft-Versus-Host Disease, and Overall Survival in Haploidentical Hematopoietic Stem Cell Transplantation Using Post Transplant Cytoxan: A Single Center Experience

Background:Haploidentical hematopoietic cell transplantation (haplo-HCT) has emerged as a popular alternative to traditional HLA-matched hematopoietic cell transplant. The major advancement of haplo-HCT has increased donor availability to many patients in need, therefore investigating the factors that may affect outcomes is necessary to improve overall survival and reduce transplant-related mortality. Data regarding optimal dose of CD34 cells, CD3 cells and CD34/CD3 ratio used during haplo-HCT to ensure favorable outcomes with post-transplant cyclophosphamide (PTCy) is lacking. Previously we have reported improved outcomes using CD34 cells limited to 7x10^6 cells/kg or less. In this report we are presenting an updated analysis including outcomes related to CD34/CD3 ratio used during haplo-HCT.Methods:We retrospectively analyzed adult patients at USC Norris Cancer Hospital who received haplo-HCT from 2014 to 2020. The primary endpoint assessed was 1-year GVHD-free/relapse-free survival (GRFS). Secondary endpoints included overall survival (OS), 1-year transplant related mortality (TRM) and incidence of acute and chronic GVHD. Kaplan Meier survival curves and log-rank tests were used to evaluate 1-year GRFS and OS with CD34 cell dose ≥ 7x10^6 cells/kg and < 7x10^6 cells/kg; CD3 cell dose < 2.5x10^8 cells/kg and ≥ 2.5x10^8 cells/kg; and CD34/CD3 ratio <2, 2-3, >3-5 and >5.Results:103 adult haplo-HCT recipients were reviewed with 55.3% male and 44.7% female. The age range was 21-71 years old (median = 51), and a majority of patients were Hispanic (62%). The most common underlying hematologic disorders included AML (40.8%), ALL (34.1%), and MDS/MPN (13.6 %). 41.7% patients with leukemia were in CR1, 55% were CR2/CR3 and 78% were MRD negative by flow cytometry prior to transplant. 73% received myeloablative conditioning and 83.5% received peripheral blood stem cells.Median CD34 dose, CD3 dose and CD34/CD3 ratio were 6.1 x10^6cells/kg, 2.27 x10^8 cells/kg and 3.2 respectively. Median time to recovery of neutrophil, platelets, and lymphocyte was 17, 24, and 124 days respectively. Incidence of 1-year GRFS was 43.7%. 1-year TRM was 13.6% and rate of aGVHD and cGVHD was 42.7% (n = 44) and 35.9% (n = 37) respectively.There was no difference in 1-year GRFS and OS when multiple dose levels of CD34 cells and CD3 cells were compared. Although when dichotomized, a CD34 cell dose of ≥ 7x10^6 cells/kg compared to < 7x10^6 cells/kg showed higher dose had significant improvement in 1- year overall survival (p-value=0.01) but no statistical difference in 1 year GRFS (p value=0.24).CD3 cell dose < 2.5 x 10^8 cells/kg trended towards worse 1-Year GRFS compared to ≥ 2.5 x 10^8 cells/kg (43.9% compared to 58.6%; p-value 0.075), similarly CD3 dose of < 2.5x10^8 cells/kg showed a lower 1-year OS compared to > 2.5x10^8 cells/kg but was not statistically significant (78.7% compared to 89.4%; p-value 0.092). 1-year GRFS and OS did not show statistical difference at CD34:CD3 ratios of < 2, 2-3, 3-5 and > 5, although on cox regression analysis the HR for 1-year GRFS was 2.92 (95% CI 1.21-7.05) in patients with CD34:CD3 > 5 as compared to reference of < 2 (p-value 0.017). Multivariate regression also showed CD3 cell doses of 2-3x10^8 cells/kg and >3 x 10^8 cells/kg were associated with worse 1-year GRFS with HR of 0.43 and 0.40 and p-value of 0.041 and 0.048 respectively when compared to reference of < 1x10^8 CD3 cells/kg.Discussion:Our results demonstrate 43.7% survived 1 year compared with reports of 24-35%. The OS was significantly better in the CD34 dose > 7x10^6 cells/kg. CD3 <2.5x10^8 cells/kg showed a trend towards lower 1-year GRFS and OS, which was not statistically significant. On multivariate analysis CD3 dose of > 2x10^8 cells/kg was associated with inferior 1-year GRFS. Conversely, higher CD34/CD3 ratio >5 was associated with increased 1-year GRFS. Thus, our findings indicate that along with improvement in OS by using >7x10^6 CD34 cells/kg, lower CD 3 cell dose <2x10^8 cells/kg and higher CD34/CD3 ratio > 5 can improve 1-year GRFS in patients receiving haplo-HCT. [Display omitted] DisclosuresChaudhary: Angeles Therapeutics: Current holder of individual stocks in a privately-held company, Current holder of stock options in a privately-held company, Membership on an entity's Board of Directors or advisory committees, Other: Founder, Patents & Royalties: Cell therapy ; Athelas: Consultancy, Current holder of stock options in a privately-held company; Oncotartis: Consultancy; Pancella: Consultancy; Moderna: Current equity holder in publicly-traded company; Celldex: Current equity holder in publicly-traded company; TCR2: Current equity holder in publicly-traded company; Allogene: Current equity holder in publicly-traded company. Yaghmour: Jazz: Consultancy, Honoraria; Astellas: Consultancy; Takeda: Consultancy; Incyte: Consultancy.

Busulfan (Bu) and Cyclophosphamide (Cy) Based Conditioning Regimen Still Holds the Promise of Being a Safe and Efficacious Regimen for Allogeneic Transplantation in Patients with Transfusion Dependent Thalassemia (TDT) Even in High Risk

Introduction: Allogeneic stem cell transplantation (HSCT) is a potential curative treatment for TDT. BuCy based regimen has been used widely as a standard myeloablative chemotherapy. However, the use of treosulfan based conditioning regimen has increased over the last decade (Choudhary D et al BBMT 2013). We analysed the safety and efficacy of BuCy based vs Treosulfan/Thiotepa/Fludrabine (Treo/Thio/Flu) regimens in TDT between September 2013 and March 2021.Method: This is an observational retrospective hospital record-based study approved by Institutional Review Board. Regimen used: Treo/Thio/ Flu : Thiotepa 8 mg/kg , treosulfan 14 g/m2/day for 3 days, and fludarabine 40 mg/m2/day for 4 days . Flu/Bu/Cy/ATG : Fludrabine 30mg/ m2/ day for 6 days ,Antithymocytoglobulin 4.5mg/kg in 3 days , Busulfan (per oral) 14mg/kg ( boys) and 12mg/kg (girls) in 4 days, Cyclophosphamide 40mg/kg/day ( boys)and 50mg/kg/day ( girls) for 4 days.Statistical Analysis: Fisher's exact test was used for discrete variables and t-test was used for continuous variables. Log-rank test was used for the difference in survival between the groups. P value < .05 was considered statistically significant. Cox regression for survival analysis was also used for time to event data of the predicted variables.Results: As shown in Table 1, 74 patients were enrolled, out of which 35 (47.2%) patients received BuCy based regimen whereas 39(52.7%) patients received Treo/Thio/Flu. All were fully HLA matched. Median age was 5.5 (1-12) years and 9 (1-15) years respectively. According to Lucarelli classification, number of patients with Class I, II, III were 17, 12, 6 in BuCy group vs 2, 14,18 in Treo/Thio/Flu group respectively. When stratified according to Matthew classification, 06 (17.1%) and 11 (28.2%) patients were in class IIIB respectively (Mathews V et al, BBMT 2007). Source of graft was bone marrow in BuCy group vs peripheral blood stem cell (PBSC) in Treo/Thio/Flu group. Mean CD34 cell dose was 3.82(2.2-9.1) vs 5(1.65-8.01) 106/kg in BuCy vs Treo/ Thio/Flu group respectively. Neutrophils and platelets engrafted at median of 16 days (14-21) and 16 days (9-47 ) in BuCy and 15 days (10-20) and 13 days (9-41) in Treo/ Thio/ Flu. Median duration of follow-up was 28 (23-32.9) months. Two (5.7%) patients had rejection (primary=1, secondary=1) in BuCy group whereas none in Treo/Thio/Flu. Five (14.3%) vs 10 (25.6%) patients developed grade ¾ oral mucositis respectively where 1 patient in each group belonged to Class III. Sinusoidal obstruction Syndrome (SOS) was observed in 02 (5.7%) vs 04 (10.3%) patients (p=0.047) respectively, with no patients affected in Class III. BuCy group had 04(11.4%) patients with acute GVHD, including one patient with grade 3. Treo/Thio/Flu group had 15(38.5%) patients with acute GVHD including 4 patients with grade 3 which had significant impact on survival (p=0.038). We also observed chronic GVHD in 04(11.4%) and 11(28.2%) patients respectively which was mainly limited stage in former and extensive in later which impacted the survival (p=0.031). CMV viremia was observed in 14 (40%) vs 8 (20.5%) patients respectively. We also encountered significant infections in both groups {21 (60%) vs 17 (43.6%)}, however, difference was not statistically significant. Four (5.1%) patients had transplant related mortality (TRM) in Treo/Thio/Flu group, in contrast to none in BuCy group. Commonest cause of death was sepsis. Mixed chimerism was commonly seen in BuCy group {20 (57.1%)} vs Treo/Thio/Flu group {12(30.1%)}.(Table 2) At last follow up, all alive patients except two patients with rejection are transfusion independent. Five-year Thalassemia-free survival (TFS) and overall survival (OS) of entire cohort was 94%+3% and 93%+4% respectively. Estimated OS and Event free survival (EFS) of BuCy vs Treo/Thio/ Flu was 100% vs 89.7% (p=0.060) and 93.9% vs 89.7% (p=0.472) respectively.(Figure 1)Discussion: We observed significant difference in TRM, acute and chronic GvHD and SOS favoring the BuCy group even in class III. On the contrary, we encountered rejections(n=2) and increased number of mixed chimerism in BuCy group which corroborates with previous literature (Fouzia N et al, BMT 2018).Conclusion: In our experience BuCy based conditioning regimen is a safe and effective regimen even in high risk class III TDT, with less TRM in comparison to Thio/Treo/Flu regimen. However, one needs to be vigilant for rejections and mixed chimerism. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

The Two-Step Approach to Haploidentical Transplant: Can Altering Timing in the Conditioning Regimen Increase Graft Versus Tumor Effects?

In the two-step approach to haploidentical hematopoietic stem cell transplantation (HI-HSCT), following conditioning, recipients receive the lymphoid portion of their graft (“DLI”) containing a fixed dose of 2 x 10 8/kg CD3+ cells (Step 1 of the transplant). After the DLI, a 2 day period of alloreactivity and haploimmunostorm occurs which resolves with the administration of Cyclophosphamide (CY) for GVHD prophylaxis/rejection prevention. After the completion of CY, a CD34-selected donor product is infused (Step 2 of the transplant). It has been postulated that a rapid reduction in quantity and a functional impairment of alloreactive T cells by CY contributes to the establishment of tolerance between the donor and recipient immune systems. Based on their degree of disease burden at HSCT, a potentially important difference between patients undergoing HI-HSCT is the percentage of graft versus tumor (GVT) versus graft versus host (GVH) reactive T cells that are likely to become activated during the haploimmunostorm, and as a result of this activation, their subsequent inhibition by CY. In the initial two-step trial (2006-2010-initial group), relapsed disease was the major barrier to long-term survival (OS). In the follow-up trial (2013-2016-later group), extra time between the end of conditioning and the DLI was added to allow for a greater reduction in disease burden prior to the introduction of the DLI (Figure). We hypothesized that by allowing more of the malignancy to die off, less GVT specific T-cells in the DLI would become activated prior to CY administration. The result would be the avoidance of suppression of these cells by CY resulting in reduced relapse rates.We compared the outcomes of patients treated on the initial trial to those treated on the later trial. The number and median age of subjects in the initial and the later groups were 27 vs 40 and 51 vs 52 years. Diagnoses were AML (59% vs 33%), MDS (7% vs 18%), ALL (15% vs 27.5%), Burkitt's (0% vs 5%), NHL (11% vs 10%), and other (8% vs 6.5%). There was no significant differences between the groups in Revised Disease Risk Index on chi square analysis or HCT-CI on Mann-Whitney analysis. All patients received 12 Gy total body irradiation for conditioning; the initial group over 4 days, the later group over 3 days. Patients in both groups received a fixed dose of 2 x 10 8/kg of T cells in the DLI, and tacrolimus and mycophenolate mofetil for additional GVHD prophylaxis. Median CD34 cell dose was 3.6 x 10 6/kg versus 6.0 x 10 6/kg (p=0.01) in the initial versus later groups respectively.At two years in the initial and later groups, the cumulative incidence of relapse-related mortality was 30% vs 10% (p=0.04), non-relapse mortality was 22% vs 30% (p=0.28), acute GVHD 48% vs 38% (p=0.198), and chronic GVHD 15% vs 20% (p=0.591). Kaplan-Meier probability of OS at 2 years was 48% vs 63% (p=0.431).The analysis was limited by its retrospective comparison of two groups and small sample size. However, the data supports a potential relapse benefit, without increased toxicity, of the later approach. Improved GVT effects due to the alteration in DLI timing potentially contributed to lower relapse related-mortality, although superior tumor control based on a different radiation strategy should be considered. A prospective, randomized two arm trial comparing the two conditioning approaches is warranted. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Haploidentical Natural Killer Cell Therapy As an Adjunct to Stem Cell Transplantation for Refractory Acute Myeloid Leukemia

Refractory acute myeloid leukemia (AML), defined as failure of 2 cycles of induction therapy at diagnosis or of 1 cycle at relapse, represents a subgroup with poor clinical outcomes. In our transplant cohort, the 5-year overall survival in this subgroup was 16% (Ganapule at al. JGO 2017). Haploidentical natural killer cell (NK) therapy is a strategy that is being explored in refractory malignancies. Our in-vitro and animal model data suggest that exposure to arsenic trioxide (ATO) results in enhanced NK cytotoxicity (Alex AA et al. Front. Immunol 2018). Historically, at our center, patients with refractory AML have been treated with cytoreductive therapy (FLAG ± idarubicin or mitoxantrone + etoposide for 3 to 5 days) followed by 1-week rest and then a reduced-intensity transplant with fludarabine + melphalan conditioning while in peak cytopenia. From February 2019, we initiated a phase II single arm clinical trial (CTRI/2019/02/017505) enrolling patients with refractory AML planned for a stem cell transplant in peak cytopenia. Patients received CD56-positive cells from an HLA haploidentical related family donor (other than the stem cell donor, wherever feasible) following cytoreductive chemotherapy. The NK cell donor preference strategy included presence of KIR ligand mismatch, greater number of KIR B motifs (or the B score), lower donor age, and negative donor specific antibodies tested using flowcytometry crossmatch (Figure 1a). CD56-positive selection was done using CliniMACS prodigy system. This was followed by overnight incubation of the CD56 positive cells in autologous plasma with 2 micromolar ATO and 500 U/mL of interleukin-2. The CD56 positive cells were then infused to the patient 1-day after the completion of cytoreductive chemotherapy. This was followed by a reduced intensity stem cell transplant (Figure 1b). The primary outcome variable was 1-year relapse free survival. From February 2019, 14 patients with median age 28 years (IQR: 15.75-31.5) were enrolled in this trial. Six were females. Six had primary-refractory AML while 8 had relapsed-refractory AML. The cytoreductive chemotherapy was FLAG ± idarubicin (n=7), Mitoxantrone + Etoposide (n=6) and GCLAC (n=1). The median blast percentage on flowcytometry MRD testing prior to NK infusion was 15.9% (IQR: 9.1%-54.5%) (n=11). The median B score for the NK cell donors was 2 (IQR: 1-3). The median age of the NK cell donor was 43 years (IQR: 36-49.5). KIR ligand mismatch with the patient was noted in 2 donors. The median CD56-cell dose infused was 46.16 x 10 6/kg (IQR: 25.06-70.36) (Figure 1c). Pre-defined release criteria, including sterile cultures, and endotoxin negativity were met in all cases. There was no infusion related toxicity. The median blast percentage on flowcytometry MRD testing done following NK cell infusion was 11.9% (IQR: 4.9%-47.6%) (n=8). One patient withdrew consent after NK cell infusion and did not undergo transplant. For the remaining 13 patients, the stem cell donor was HLA matched (n=4), HLA 9/10 matched (n=1) or HLA haplomatched (n=8). The median CD34 cell dose infused was 10 x 10 6/kg (IQR:7.51-11.6). Five (38.5%) patients died of immediate post-transplant complications (sepsis (n=3) on days 1, 2 and 28, cerebral venous sinus thrombosis (n=1) on day 1 in a patient treated with hormonal contraceptives for menorrhagia, and veno-occlusive disease (n=1) on day 15 in a patient undergoing a second transplant) while 2 (15.4%) did not engraft (both subsequently died of infective complications following engraftment post-second transplant). Of the remaining 6 (46.2%) patients who engrafted and survived beyond 1 month of the transplant, the day 28 post-transplant MRD was negative for 5 patients while it was positive in 1 patient (0.13%). On follow up, 2 (15.4%) patients developed disease relapse (on days 54 and 218 respectively) and died. The remaining 4 (30.8%) patients are alive and relapse free at last follow up (mean follow up of surviving patients is 16 months). One patient received a CD34 cell boost on day 96 (cell dose - 8.55 x 10 6/kg) for poor graft function. For the entire cohort, the estimated 1-year event free survival is 28.8% ± 13.1%(Figure 1d). Whereas, acute GVHD was noted in 3 patients (50%; out of 6 evaluable patients) and chronic GVHD was noted in 3 patients (50%; out of the 6 evaluable patients). Thus, haploidentical NK cell therapy as an adjunct to transplant is safe and merits further evaluation in patients with AML. [Display omitted] DisclosuresMathews: Christian Medical College: Patents & Royalties: US 2020/0345770 A1 - Pub.Date Nov.5, 2020; AML: Other: Co-Inventor.

Frontline-matched sibling donor transplant of aplastic anemia patients using primed versus steady-state bone marrow grafts.

Priming donors with G-CSF before BM harvest is reported to improve engraftment and GvHD in recipients. These effects are highly desirable when transplanting patients with non-neoplastic hematologic diseases, particularly AA patients. Here we retrospectively report the outcomes of 39 AA patients receiving a primed BM graft from MSD to 43 patients receiving a steady-state BM graft from MSD, otherwise transplanted using a uniform transplant platform. The graft had higher TNC and CD34 cell concentrations in the primed group (p < 0.001), and that was reflected in higher TNC and CD34 doses per kilogram of recipient in the primed group (p = 0.004 and 0.03, respectively). The OS for primed BM graft recipients was 97.4% and 78.9% for the steady-state BM graft recipients, p-value = 0.01. The cumulative incidence of death without GF was 2.6% in the primed group and 16.3% in the steady-state group, p-value = 0.03. There was no difference in GvHD incidence between the two groups. We confirm that priming improved the TNC and CD34 graft concentration and cell dose; this evidence along with other reported studies constitute reasonable evidence to prove that BM priming improve engraftment. We observed no increase in GvHD using primed BM graft.

Effect of pre-transplant JAK1/2 inhibitors and CD34 dose on transplant outcomes in myelofibrosis.

Allogeneic hematopoeitic cell transplantation (allo-HCT) is the only curative treatment for myelofibrosis (MF). We evaluate the impact of various factors on survival outcomes post-transplant in MF. Data of 89 consecutive MF patients (primary 47%) who underwent allo-HCT between 2005 and 2018 was evaluated. Fifty-four percent patients had received JAK1/2 inhibitors (JAKi) pre-HCT. The median CD34 count was 7.1x106 cells/kg. Graft failure was seen in 10% of the patients. Grade 3-4 acute GVHD (aGVHD) and moderate/severe chronic graft versus host disease (cGVHD) occurred in 24% and 40% patients, respectively. Two-year overall survival (OS) and relapse free survival (RFS) were 51% and 43%, respectively. Cumulative incidence of relapse (CIR) and non-relapse mortality (NRM) at 2years were 11% and 46%, respectively. Higher CD34 cell dose (≤5×106 cells/kg vs 5-9 or ≥9×106 cells/kg) and lower pre-HCT ferritin (</=1000ng/ml) were associated with better OS, RFS and lower NRM. Grade 3-4 aGVHD was associated with higher NRM. Use of pre-transplant JAKi was associated with lower incidence of grade 3-4 aGVHD. In summary, higher CD34 cell dose is associated with better allo-HCT outcomes in MF and pre-HCT JAKi use is associated with reduced risk of severe aGVHD. These two modifiable parameters should be considered during allo-HCT for MF.

Identifying Risk Factors for Acute and Chronic Graft-Versus-Host Disease in T-Replete HLA-Haploidentical Hematopoietic Cell Transplantation with Post-Transplant Cyclophosphamide

Introduction: Acute(aGVHD) and chronic graft-versus-host disease (cGVHD) cause significant morbidity and mortality in patients post hematopoietic cell transplantation (HCT). The use of T-replete HLA-haploidentical transplantation (HIDT) with post-transplant cyclophosphamide has become a common donor source for patients lacking a suitably matched donor. In spite of the increase in HIDT, there is paucity of data describing aGVHD and cGVHD outcomes and potential risk factors for developing graft-versus-host disease after HIDT.Methods: The outcomes and the characteristics of 203 patients undergoing first allogeneic transplantation using HIDT with post-transplant cyclophosphamide between 2005 and 2016 were retrospectively assessed to identify the incidence and risk factors for aGVHD and cGVHD. Variables included in the analysis included patient related (age, sex, race, karnofsky, HCT-CI), disease related (diagnosis, disease type, disease risk index DRI, CIBMTR risk status) and transplant related (graft source as marrow vs peripheral blood, donor age, donor/recipient relationship, donor/recipient gender match, donor/recipient CMV match, conditioning intensity, high dose TBI in conditioning intensity, CD34 cell dose, CD3 cell dose and year of transplant). Univariate analysis with Gray's test and log-rank was carried for cumulative incidence and survival respectively. The proportional hazard cox model was used with backward elimination to select significant covariates. Multivariate analyses for developing GVHD, overall survival (OS), disease free survival (DFS), and relapse were conducted.Results: The median age was 51 years (range 19, 75) with a median follow up for survivors of 37 months. Seventy patients (34%) received bone marrow as graft source and 43% had Myeloablative conditioning. All patients received GVHD prophylaxis consisting of post-transplant cyclophosphamide on Days +3 and +4, MMF till day +35 and tacrolimus till day +180. The cumulative incidence for aGVHD grade II-IV and grade III-IV were 45% and 12% respectively. The common organs involved in aGVHD were skin (76% of cases, 39% stage 3 /4), gut (58% of cases, stage 3 /4 11%) and liver (7% of cases, stage 3 /4 of 1%). Subsequent aGVHD flare developed in 6 patients (5 with gut GVHD and 1 skin GVHD). The cumulative incidences of all grade cGVHD and moderate-severe cGVHD were 32% and 24% respectively (table 1). Conditioning intensity was the only risk factor associated with developing grade 2-4 aGVHD (p=0.04). Patients that received myeloablative regimens as compared to those who received a reduced intensity or non-myeloablative regimen had statistically higher rates of grade 2-4 aGVHD (hazard ratio [HR] of 1.52 (95% CI, 1.01-2.29, p=0.04). Risk factors for cGVHD showed that race and hematopoietic cell transplantation-comorbidity index (HCT-CI) had a statistically significant bearing on the likelihood of developing all-grade cGVHD (p=0.004 and 0.01 respectively). Graft source (marrow vs Peripheral blood) was a significant risk factor for developing moderate-severe cGVHD (p=0.03). Multivariate analysis on OS, DFS and relapse showed that Patients aged 55 or older (HR of 1.91, 95% CI 1.22-2.99, p =.005) and High/very high DRI risk (HR 2.06, CI 1.05-4.00, p=0.03) had worse overall survival rates. Older age, not developing chronic GVHD and receiving a transplant between 2005 and 2010 were all associated with a worse DFS (P<0.01 for all). High/very high DRI, male gender and not developing cGVHD were all significant factors for a higher relapse rate.Conclusions: This single center analysis of GVHD incidence and risk factors after HIDT using post-transplant cyclophosphamide showed that conditioning intensity, graft source and HCT-CI to be factors affecting incidence of GVHD. Higher disease risk and older patient age were associated with worse overall survival. [Display omitted] DisclosuresSolh:Amgen: Speakers Bureau; ADC Therapeutics: Research Funding; Celgene: Speakers Bureau.

Low Dose Donor Lymphocyte Infusion (DLI) Is Effective As Prophylactic Therapy for Mixed Chimerism in the Setting of In-Vivo T Cell Depleted Allogeneic Hematopoietic Cell Transplantation

Introduction: Donor lymphocyte infusion (DLI) has been used as a preemptive therapy for those with mixed donor chimerism (MDC) or in the presence of minimal residual disease or as salvage therapy for relapse of disease post allogeneic stem cell transplantation (allo SCT). The efficacy of DLI and the ease of therapy are balanced by the potential for significant toxicity with 100-day DLI-related mortality rate approaching 20%. A number of strategies have been employed in an effort to avoid the major complication of DLI, namely Graft-versus-host disease (GVHD). These strategies include the use of escalating doses of T cells (1 x 10 6 - 1 x 10 8/ kg) and manipulations of the T cells prior to infusion. We conducted a retrospective study of the prophylactic role of low dose DLI (< 5 x 10 6 /kg) in patients with mixed chimerism in the setting of in-vivo T cell depleted allo SCT.Methods: We identified 33 consecutive patients who underwent allo SCT with T cell depletion conditioning regimen with a minimum of 100-day post-transplant follow up. Five patients qualified for our study. MDC was defined by CD3 or CD33 subsets <=95% of the donor and trending down in two or more consecutive samples measured at 100-day or beyond. Full donor chimerism (FDC) was > 95% of CD3 or CD33 subsets. We adopted two myelo-ablative and 1 reduced intensity conditioning with in-vivo T cell depletion in all regimens. Myelo-ablative regimens: Fludarabine 30 mg IV day -8 to day -4 and Busulfan 3.2 mg IV from day -5 to day -2. GVHD prophylaxis consisted of anti-thymocyte globulin for a total dose of 7.5 mg/kg IV from day -4 to day -2 and tacrolimus starting day -1 (FB-ATG regimen). Carmustine 300 mg/ m2 IV day -6, Cytarabine 400 mg/ m2 and etoposide 200mg/ m2 IV on day -5 to day -3, melphalan 140 mg/ m2 IV on day -2. GVHD prophyalxis consisted of alemtuzumab 20 mg IV on day -5 to day -2 and tacrolimus starting day -1 (BEAM-C regimen). Reduced intensity regimen consisted of Fludarabine 30mg/m2 on day -6 to day -2 and melphalan 140 mg/ m2 on day -2. GVHD prophylaxis consisted of alemtuzumab 20 mg IV daily from day -8 to day -5 and tacrolimus starting day -1 (FMC regimen). Demographic, disease and transplant variables were collected.Results: The median age was 52 (range: 28-57) years. There was 1 patient each with diagnoses of T-cell Acute Lymphoblastic Leukemia, Acute Myelogenous Leukemia, Relapsed Hodgkin Lymphoma, Chronic Lymphocytic Leukemia, and Chronic Myelomonocytic Leukemia. Three patients had received FMC regimen and 1 each received FB-ATG and BEAM-C regimen. All five patients had MDC in CD3 subset and FDC in CD33 subset pre-DLI. The median CD3 chimerism pre-DLI was 21% (9%-81%). None of the patients were diagnosed with acute or chronic GVHD pre-DLI. The median time to DLI infusion was 6 (3-9.5) months. The median CD3 dose of the DLI was 3 (range: 3-10) x 106 /kg. The median time for conversion of MDC to FDC was 3 (2-7.5) months. All 5 patients converted to FDC in CD3 subset. One out of five patients needed a second DLI (CD3 cell dose: First DLI 3 x 106 /kg and second DLI 10 x 106 /kg) due to persistent MDC in CD3 subset (Table 1). One patient (20%) developed steroid responsive acute GVHD of the skin, GI and liver (grade III) following DLI (CD 3 dose 3 x 106 /kg) and this has evolved into extensive cGVHD which is under partial remission. At 1 year follow up: none relapsed and the OS was 100%.Conclusion: Low dose DLI (CD 3 dose starting at 3-4 x 106 /kg) is highly effective (80%) as a prophylactic therapy for conversion of MDC to FDC with minimal risk of GVHD in the setting of in-vivo T cell depleted allo SCT. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Defining a Bone Marrow Immune Signature Associated with Immunoglobulin Isotype Switching after Autologous Stem Cell Transplant

Triplet induction therapy followed by autologous stem cell transplant (ASCT) and maintenance therapy can render long-term remission for newly diagnosed multiple myeloma (MM) patients (pts). Robust post-ASCT immune-reconstitution correlates with lower minimal residual disease (MRD) and better clinical outcomes but immune signatures to define such responses are lacking (Ho et al. Blood Advances 1.15 (2017). Following ASCT, the Immunoglobulin Isotype Switch (IIS) results in a new serum M-protein on serum protein electrophoresis (SPE), distinct from the M-protein pattern present at diagnosis, may be associated with a good prognosis. The objective of this study was to analyze humoral immune reconstitution that presents as IIS after ASCT and to determine if there was a correlation with patient or disease characteristics, transplant parameters and to define the associated immune signature.MethodsThe Institutional Review Board-approved study evaluated MM pts who underwent ASCT between 2007 and 2016. Data collection included patients' characteristics, induction therapy, mobilization regimen, graft characteristics including CD34 cell dose, myeloid and erythroid progenitor cells (multi-potential colony forming unit or CFU-GM and erythroid burst-forming unit (BFU-E). Percentage of NK cells (CD56(+) CD3(-) and CD16(+)CD3(-)), T-cells (CD3(+),CD56 (-)), B-cells (CD19(+)),and T-cell subpopulations (CD4(+), CD8(+),were measured with flow cytometry in pre- and post-ASCT bone marrow samples. IIS was defined as the appearance of a new serum monoclonal spike on SPE and immunofixation different from original heavy or light chain detected at diagnosis. Monoclonal proteins and quantitative immunoglobulins were assessed day+100 and with frequency of 2-8 times per year afterward.The start date for all time dependent variables was the day of transplant. The Kaplan-Meier method was used to assess overall survival (OS) and progression-free survival (PFS). Two-tailed log-rank tests compared OS and PFS curves. Factors with a P -value <0.2 in univariate analysis were included in multivariate analysis, which was performed using the Cox regression hazard model. All analyses were performed utilizing SAS 9.2 (SAS Institute, Cary, NC, USA).ResultsThe analysis included 177 patients with median age of 60.7 years. IIS was detected in 39 pts (22.0%) with a significantly higher incidence in pts who received lenalidomide before ASCT (11.2% vs. 30.4%, P=0.001). Post-ASCT IIS was more frequent in IgA, light chain disease, and in pts who experience very good partial and complete response post-ASCT rather than less optimal response (Table-1 and 2). The occurrence of IIS did not correlate with ASCT toxicity, i.e., mucositis duration or grade as well as length of hospital admission (Table 2). IIS occurred more frequently in pts without suppressed un-involved immunoglobulin (92% vs 8%, p=0.001).The presence of post-ASCT IIS correlated significantly with PFS and OS (Figure.1.A and B). Age, cytogenetics, response category, presence of IIS and low LDH correlated with PFS by univariate analysis. Cytogenetics, LDH and IIS presence were also significantly associated with response as determined by multivariate analysis. The median time between pre- and post-ASCT BM was 92 days (range 79-123). Pts with IIS showed a trend toward faster B cell recovery in comparison to pts without IIS, however this difference did not reach statistical significance. All pts had low CD4/CD8 ratio, due to low number of CD4 and higher number of CD8. Appearance of post-ASCT IIS was associated with statistically lower CD8 T cell percentages and higher CD4/CD8 ratio in comparison to pts without IIS (Figure.1.C), suggestive of faster immune reconstitution in this group of pts. All pts who relapsed had an isotype different from IIS, highlighting the benign nature of this phenomenon.ConclusionOur data are consistent with the benign nature of IIS that may emerge in certain patients following ASCT. Association of a robust recovery of specific immune cell subpopulations with IIS occurrence and superior survival outcomes may represent an anti-myeloma protective effect resulted from cellular and humoral immunoreconstitution. Efforts to better understand how specific immune subpopulations trigger and regulate the immune response to tumors may improve long-term control of MM. Further research to define underlying anti-tumor effect of ISS is needed. [Display omitted] DisclosuresDe Lima:Pfizer: Membership on an entity's Board of Directors or advisory committees; Celgene Corporation: Research Funding. Malek:Sanofi: Membership on an entity's Board of Directors or advisory committees; Celgene: Speakers Bureau; Takeda: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau.

Autologous Stem Cells as Backup for Patients Undergoing Allogeneic Related Transplant for Thalassemia Major.

Abstract 4539Autologous backup of harvested stem cells from patients with Beta thalassemia major, undergoing allogeneic HLA matched sibling transplantation, in order to rescue the patient in the event of graft failure, has been practiced in some transplant centers in the world. From February 2007 we instituted a program of harvesting and cryopreserving autologous bone marrow for all patients undergoing transplant for thalassemia at our center and this abstract is a report on 62 patients for whom this was done over the past 26 months till June 2009. Since most of the patients were below 10 years a bone marrow harvest was performed under general anesthesia. The harvest was depleted of red cells by gravity sedimentation using hydroxyethyl starch, plasma depleted and cryopreserved using 10% dimethyl sulfoxide and stored at -18-degC in the vapor phase of a liquid nitrogen storage system. The mean volume of the product before freezing was 180 ml. The median CD34 cell dose was 8.35 × 106 cells/kg (range 0.6 to 24.6 × 106 cells/kg).During this 26 month period there was one early rejection, after initial engraftment, without autologous recovery with the patient being critically ill and febrile. Autologous stem cells were re-infused on day + 90 when the ANC was 0. However there was progressive deterioration in respiratory function and the patient died on day+92 with disseminated pulmonary aspergillosis. It is extremely difficult to decide when to re-infuse autologous stem cells in a patient who is sick post transplant and may not engraft. There was only one other rejection in this cohort of 62 patients but this patient had spontaneous recovery of autologous hematopoiesis and did not require intervention.The total cost of harvesting autologous stem cells under anesthesia and Cryopreservation, at this center is approximately $ 1600 and this represents 10% of the total cost of an allogeneic stem cell transplant. In this cohort of 62 patients, cryopreserved stem cells were used in only one patient without preventing mortality. The increased cost, manpower and time required for this procedure needs further evaluation and also the criteria on which autologous stem cells are to be re-infused needs to be established. Disclosures:No relevant conflicts of interest to declare.

Prophylactic Foscarnet for Human Herpesvirus 6: Effect on Hematopoietic Engraftment after Reduced-Intensity Conditioning Umbilical Cord Blood Transplantation

The high incidence of human herpesvirus-6 (HHV-6) reactivation, potentially interfering with engraftment after umbilical cord blood (UCB) hematopoietic cell transplantation (HCT), remains a major challenge. To potentially address this problem, we evaluated the effect of prophylactic foscarnet administered twice daily beginning on day +7 and continuing through engraftment in 25 patients. To determine the impact of foscarnet on HHV-6, engraftment, and other transplantation outcomes, we compared results in 61 identically treated patients with hematologic malignancies. Treatment and control groups underwent reduced-intensity conditioning UCB HCT with a conditioning regimen of fludarabine, cyclophosphamide, and total body irradiation 200 cGy with or without antithymocyte globulin (ATG), using sirolimus plus mycophenolate mofetil immune suppression. The treatment and control groups were similar in terms of age, disease risk, use of ATG, Hematopoietic Cell Transplantation Comorbidity Index, and graft CD34 cell dose; however, foscarnet-treated patients were less likely to receive a double UCB graft and to be treated more recently (2016 to 2018). The cumulative incidence of HHV-6 reactivation by day +100 was 63% for all patients (95% confidence interval [CI], 51% to 75%) and was not significantly different between the 2 groups. HHV-6 reactivation occurred at a median of 34 days in the foscarnet group and 25.5 days in the control group. The incidence of neutrophil engraftment at day 42 was higher in the foscarnet group compared with the control group (96%; [95% CI, 83% to 100%] versus 75% [95% CI, 64% to 85%]; P< .01). The cumulative incidence of platelet engraftment by 6 months was 92% (95% CI, 69% to 100%) for the foscarnet group versus 75% (95% CI, 60% to 90%) for the control group (P= .08), and multivariate analysis identified the use of foscarnet as an independent predictor of better platelet engraftment. No patients died as a result of graft failure in recipients of foscarnet, whereas 5 patients died from graft failure in the control group. Six-month overall survival (OS) and nonrelapse mortality (NRM) were better in the foscarnet group (96% versus 72% [P= .02] and 4% versus 18% [P= .07], respectively). Even though foscarnet prophylaxis did not prevent HHV-6 viremia, we observed a delay in time to HHV-6 reactivation, a trend toward differences in engraftment, NRM, and OS compared with historical controls.

The Two-Step Approach to Haploidentical Hematopoietic Stem Cell Transplantation (HI HSCT): 15 Years of Transplants in Patients 19-78 Years Old

Background/Methods: The two-step approach to HI HSCT was developed in 2005 with the first patient treated on clinical trial in early 2006. In this approach, after myeloablative [MA- 12 Gy total body irradiation (TBI)], reduced intensity (RIC- fludarabine, 2 Gy TBI and cytarabine, OR thiotepa, OR busulfan), or nonmyeloablative (NMA-fludarabine and 2 Gy TBI) conditioning, patients receive a fixed dose of unmanipulated donor lymphocytes (DLI) containing 2 x 108/kg CD3+ cells (Step 1). Two days later, cyclophosphamide (CY) 60 mg/kg/day x 2 is infused for bidirectional T cell tolerization. One day after the completion of CY, a CD34-selected stem cell product is infused (Step 2). All patients receive tacrolimus and mycophenolate mofetil starting at d-1. The two-step approach avoids stem cell exposure to CY, allows a growth factor-naïve fixed dose of donor T-cells to be infused increasing uniformity for outcomes analysis, and permits easier manipulation of both T-cell and CD34 cell dosing. In later protocols, the timing of the DLI after conditioning and the CD34 cell dose have been manipulated with the goal of reducing relapse, and age-based comorbidity and performance status indices were added to eligibility criteria to reduce non-relapse mortality (NRM). Results: We analyzed all 283 patients treated on a two-step HI HSCT clinical trial at our institution. The median follow-up is 63 (range 1-165) months. Diagnoses were AML (n=118), MDS (n=43), myeloproliferative disorder (n=7), CMML (n=3), B-ALL (n=21), Ph+ ALL (n=15), multiple myeloma (n=14), T cell ALL (n=9), aggressive lymphoma (n=15), CLL (n=8), Hodgkin (n=7), aplastic anemia (n=5), and lymphoma-other (n=18). Patients had high (45%), intermediate (43%), very high (5%), and low (4%) risk disease per the Revised Disease Risk Index. Median age of the group is 58 (19-78) years and 21% of patients were &amp;gt;age 65. Conditioning was MA in 56%, RIC in 37%, and NMA in 7%. All patients received 2 x 108/kg CD3+ cells in step 1 of the HSCT except for 1 early patient who received 1.7 x 108/kg CD3+ cells. Median CD34 cell dose was 6.3 (range 1.0-20.0) x 106/kg, median non-CY-exposed T cells in the CD34 product was 2.88 (range 0.33-50.0) x 103/kg. Patients developed a haploimmunostorm manifested by high grade fever, diarrhea and rash within 24 hours of receiving DLI. These symptoms effectively resolved after the administration of CY. Median peak fever of patients during the haploimmunostorm was 103.6 (range 98.6-106.1). No patients died as a consequence of the haploimmunostorm. Cumulative incidence (CI) of donor engraftment was 97%. Median time to neutrophil and platelet engraftment was 11 (8-21) days and 17 (10-173) days respectively. All results at 2 years: CI of relapse and NRM were 25% each. CI grades 2-4 and 3-4 acute GVHD were 39% and 7% respectively, and CI chronic GVHD was 15%. Probability of survival (OS) was 55% in the total cohort and 34% in patients &amp;gt;65 years. In patients with AML which represented the largest subgroup of patients, OS was 51% in the total cohort and 40% in patients &amp;gt; 65. Conclusion: HI HSCT using the two-step approach is an effective treatment for a variety of hematologic malignancies and dyscrasias. Despite older age, over 1/3 of patients &amp;gt;65 years were alive 2 years after HI-HSCT. Disclosures Flomenberg: Tevogen: Consultancy, Honoraria.

Use of Peripherally Inserted Central Catheter (PICC) for the Infusion of Peripheral Blood Stem Cell Products Is Safe and Effective

Introduction: Cryopreserved peripheral blood stem cell (PBSC) products are thawed at bedside and infused by gravity through a large bore central venous line (CVL). Peripherally inserted central venous catheters (PICC) are routinely used for infusion of blood products and medications but are rarely used to administer hematopoietic progenitor cells (HPC). The rationale for this practice is not well established but the general assumption is that the smaller gauge sizes of the PICC and resultant decreased infusion rates would damage the HPCs. The use of PICC to infuse HPCs can have many benefits, such as patient comfort, cost effectiveness, and reducing potential line-related complications from the insertion of a large bore, and often additional, CVL. These line-related complications include infections, pneumothorax, haematomas, etc. The aim of this prospective observational study is to present the experience of using PICC in lymphoma patients receiving autologous PBSC transplantation in terms of the safety and efficacy. Methodology: From September 2019 to June 2020, a prospective observational study involving 16 patients with lymphoma undergoing autologous PBSC transplantation was conducted in National University Cancer Institute, Singapore (NCIS). The patients were divided into 2 groups - the first group included 9 lymphoma patients who received their autologous PBSC transplant via PICC, while the second/control group included 7 lymphoma patients who received the treatment via a large bore CVL. The types of PICC and CVL inserted for the patients were standardized - 19G dual lumen PICC and 7Fr triple lumen non-tunnelled CVL respectively. All the CVLs were inserted in the right internal jugular vein, while the PICC were inserted in either the brachial or basilic veins. All patients in both groups underwent BEAM conditioning transplantation regime prior to autologous PBSC transplantation. The duration of the catheter-in-situ, catheter-associated complications, PBSC infusion rate, CD34 cell dose, total nucleated cell dose infused, and the time for absolute neutrophil and platelet count engraftment were analysed for the study. Results: The baseline characteristics and results for both groups are shown in Table 1. It is important to highlight that for the first group using PICC, none of them had any adverse event from PBSC transplantation. 44.4% of the patients had only minor issues during the PBSC infusion, mainly due to slower infusion rate and sediments were seen in the tubing of the PICC. These issues were quickly overcome by manual flushing of the PICC with normal saline fluid boluses. Only 1 out of 9 had a mild skin irritation at the insertion site of the PICC. For the second/control group using CVL, 43% of them had both PICC and CVL in-situ at one point of their treatment. These patients underwent an additional procedure for CVL insertion and the CVL was removed within 2 weeks of insertion. Only 1 out of 7 patients had minor issue of severe nausea during the PBSC infusion. There was no adverse event during the PBSC infusion or catheter associated complication. Conclusion: Our study showed that the use of PICC is safe and effective for patients receiving autologous PBSC transplantation, compared to the conventional large bore central venous catheters. Despite having longer PBSC infusion rate for PICC, the time taken for neutrophil and platelet recovery between both groups were comparable and there were no serious complications. Table Disclosures Chng: Celgene: Honoraria, Research Funding; Janssen: Honoraria, Research Funding; Amgen: Honoraria, Research Funding; Abbvie: Honoraria; Novartis: Honoraria.

Fresh Versus Cryopreserved Peripheral Stem Cell for Autologous Transplantation in Multiple Myeloma: An Analysis of Short-Term Outcomes

BACKGROUND: The current standard practice in North America is to cryopreserve mobilized autologous stem cells for use after high dose chemotherapy for multiple myeloma. Fresh autologous stem cell infusions are used infrequently around the world for this same purpose with comparable efficacy. This study aims to compare short term outcomes after autologous transplant with fresh versus (vs) cryopreserved (cryo) stem cells. METHODS: Sixty-four (64) consecutive patients who underwent autologous stem cells for multiple myeloma at our center between June 2018 and December 2019 were grouped based on whether fresh or cryopreserved product was used for transplantation. The primary outcomes included the number of days until neutrophil and platelet recovery. The secondary outcome was length of hospital stay (LOS). After mobilization with G-CSF with or without plerixafor, peripheral blood stem cells were harvested over 1 day. For the fresh group, the collected cells were stored at 4 °C in the cell therapy laboratory for up to 48 hours. Meanwhile, the patient underwent high-dose melphalan treatment, 24 hours following which, the autologous stem cells were infused. In the cryopreserved group, the cells were cryopreserved for variable lengths of time until their infusion 48 hours after high-dose melphalan therapy. RESULTS: Thirty-two (32) patients received fresh product and 32 received cryopreserved product. Baseline characteristics were similar between the groups and summarized in Table 1. Median CD34 count at infusion was 3.90 (range 2.83 to 5.68) million/kg in the fresh group and 4.32 (range 2.46 to 7.41) million/kg in the cryopreserved group, which was not statistically different (p= 0.07). Thirty patients in the fresh group and 27 in the cryo group received plerixafor. All the patients engrafted. The median time to neutrophil engraftment was 11 days (range 10-13 days) in the fresh group compared to 12 days (range 10-18 days) in the cryopreserved group (10.71±0.77 vs 12.18±1.71 days. P= 0.90). ANC &amp;lt;500 developed earlier in the fresh group vs cryopreserved group at median of 5 vs 8 days respectively (5.46±0.8 vs 7.78±1.07 days. P = &amp;lt;0.0001) and the duration of neutropenia was not significantly longer (6.25±1.04 vs 6.4±1.96 days. P = 0.70). The median time to platelet engraftment was 18 days (range 14-21 days) in the fresh group versus 23 days (range 16-50 days) in the cryopreserved group (16.25±4.72 vs 23±6.53 days. P &amp;lt; 0.0001). The median LOS was 13 days (range 10-21 days) in the fresh group versus 17 days (range 13-30) in the cryopreserved group (13.25±2.83 vs 16.59±4.18 days. P = 0.0004). CONCLUSIONS: Time to platelet engraftment and length of stay in the hospital were significantly shorter with use of fresh autologous stem cells compared to cryopreserved cell for transplantation for multiple myeloma. Despite earlier development of neutropenia in the fresh group, time to engraftment and duration of neutropenia were not significantly longer. CD34 cell dose was actually lower in the fresh group, with the difference approaching statistical significance. The use of fresh autologous product is both feasible and safe. Early hematologic recovery, particularly in terms of platelet engraftment with use of fresh product has further helped with early discharge from the transplant clinic to the referring oncologists. It has also led to subsequent utilization of this approach in performing outpatient autologous transplants at our center. Table Disclosures Randolph: Bristol Myers Squibb, Celgene: Speakers Bureau. Khaled:Celgene, Seattle Genetics, Jazz, Takeda: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau.

Clinical Impact of Cytokine Release Syndrome on Outcomes of Peripheral Blood Stem Cell Haploidentical Hematopoietic Cell Transplantation with Post-Transplant Cyclophosphamide

Peripheral blood stem cell (PBSC) as a graft source compared to bone marrow has been reported to result in lower risk of relapse after haploidentical hematopoietic cell transplantation (haplo-HCT) with use of post-transplant cyclophosphamide (PTCy) as a graft-versus-host-disease (GvHD) prophylaxis. However, cytokine release syndrome (CRS) is a common complication of this platform that can affect the outcomes of patients after PBSC haplo-HCT. CRS occurs due to rapid activation and proliferation of alloreactive donor T cells resulting in the elevated secretion of inflammatory cytokines. In this study, we sought to examine the risk factors for CRS and the effect of CRS severity on outcomes of PBSC haplo-HCT. We identified total of 271 consecutive patients with hematological malignancies who received their first PBSC haplo-HCT with PTCy-based GVHD prophylaxis at City of Hope (n=157) or Moffitt (n=114) Cancer Centers between 2014 and 2019. The median patient age at HCT was 54 years (INQ range, 37-64) for the entire cohort and 48% of the patients had HCT-CI ³3. Close to 70% of the study cohort had acute leukemia and 33% of all patients had high/very high-risk disease risk index. Myeloablative conditioning was used in 52% of the cases and 81% of all HCT recipients were CMV seropositive. The median donor age at HCT was 33 years (INQ range, 26-43). The HLA -A, -B, -C, -DRB1, -DQB1, or -DPB1 mismatch between the recipient and the donor in the GVH direction was 5/10 in 51%, 4/10 in 29% and £3/10 in 20% of cases. Offspring donors were used in 54% of the patients, sibling donors in 35%, and parent/other relative donors in 11%. Female donors to male recipients were used in only 22% of patients. The median infused CD34 dose was 5.25 x106 cells/kg (range, 2.3-22.4x106) and the CD3 dose was 2.48x108 cells/kg (range, 0.002-8.88 x108). CRS of any grade by ASTCT criteria was observed in 92% of study patients within first 7 days of HCT: 54% had grade 1, 39% grade 2, and 5.2% grade 3-4. Infused cell doses of CD34 &amp;gt;5x106 cells/kg and of CD3 &amp;gt;2.5x108 cells/kg had no significant effect on grade 3-4 CRS. On multivariable analysis, the use of reduced-intensity conditioning (RIC) was associated with increased grade 2-4 CRS (HR = 1.6, 95% CI: 1.11.-2.33, p=0.01) and grade 3-4 CRS (HR = 14.7, 95% CI: 1.97-109.5, p=0.009) compared with the myeloablative conditioning. Donor 5/10 HLA-mismatch was also associated with increased grade 2-4 CRS (HR = 1.5, 95% CI: 1.05-2.18; p=0.03) and grade 3-4 CRS (HR = 3.50, 95% CI: 1.00-12.32; p=0.05) compared with £4/10 HLA-mismatch. Non-relapse mortality (NRM) at day 100, and 1-year overall survival (OS) by CRS severity is shown in Figure. Comparing with the grade 0-1 CRS in multivariable analysis (Table), increase in CRS severity was associated with lower probability of neutrophil engraftment (HR = 0.9 for grade 2 and HR = 0.4 for grade 3-4; p=0.03). Increased CRS severity as compared to the grade 0-1 was also predictive of higher risks of NRM (HR = 1.6, 95% CI: 0.95-2.79 for grade 2 and HR = 6.6, 95% CI: 3.12-13.78 for grade 3-4; p&amp;lt;0.001), lower disease-free survival (DFS; HR = 1.3 for grade 2 and HR = 4.5 for grade 3-4; p&amp;lt;0.001) and lower OS (HR = 1.2 for grade 2 and HR = 4.1 for grade 3-4; p&amp;lt;0.001) after HCT. We observed no association between CRS severity and risk of relapse or the incidence and severity of acute GvHD after transplant. We conclude that CRS is a common complication after PB haplo-HCT/PTCy. CRS severity is associated with post-HCT outcomes with grade 3-4 CRS associated with the highest risk of NRM and overall mortality after HCT. Infused CD34 or CD3 cell doses effect on CRS is unclear. RIC and higher degree of HLA-mismatch are predictive of higher-grade CRS. Identification of modifiable risk factors can help to mitigate the risk for serious CRS and subsequent mortality after PB haplo-HCT/PTCy. Figure 1 Disclosures Nishihori: Karyopharm: Other: Research support to institution; Novartis: Other: Research support to institution. Pidala:CTI Biopharma: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Amgen: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Research Funding; Takeda: Research Funding; Janssen: Research Funding; Johnson and Johnson: Research Funding; Pharmacyclics: Research Funding; Abbvie: Research Funding; BMS: Research Funding; Syndax: Consultancy, Membership on an entity's Board of Directors or advisory committees. Nakamura:Merck: Other: advisory board meeting; Alexion: Other: Support on a meeting presentation; Kyowa-Kirin: Other: Support on a meeting presentation; Celgene: Other: Support on seminar; Magenta Therapeutics: Other: Advisory board meeting; Viracor: Consultancy; Kadmon Corporation: Other: Advisory board meeting; NapaJen Pharma: Consultancy. Al Malki:Rigel Pharma: Consultancy; Jazz Pharmacuticals, Inc: Consultancy; Neximmune: Consultancy. Bejanyan:Kiadis Pharma: Membership on an entity's Board of Directors or advisory committees.

Evaluating Gvhd Outcomes Using Post-Transplant Cyclophosphamide/Tacrolimus/Mycophenolate Mofetil As Gvhd Prophylaxis Compared with Methotrexate/Tacrolimus in Matched-Related and Matched-Unrelated Hematopoietic Stem Cell Transplant in Relation to the Haplo-Identical Setting: A Single Center Experience

Background: The use of post-transplant cyclophosphamide (PTCy)/tacrolimus/mycophenolate mofetil (MMF) for GVHD prophylaxis has improved outcomes in haploidentical hematopoietic cell transplantation (haplo-HCT). PTCy is now being evaluated in matched-related (MRD) and matched-unrelated (MUD) allo-HCT. Previous studies demonstrated improved GVHD-free/relapse-free survival (GRFS) when PTCy was combined with two immunosuppressive agents and PTCy has also been associated with better relapse-free survival (RFS) as demonstrated in De Jong et al 2019, though only one immunosuppressive agent was used. Currently, there is limited published data comparing outcomes using PTCy/tacrolimus/MMF to standard MRD/MUD GVHD prophylaxis of methotrexate (MTX)/tacrolimus. The importance of studying this comparison may help to improve GVHD outcomes in MRD and MUD allo-HCT. Methods: We retrospectively analyzed adult patients at USC Norris Cancer Hospital (age ≥ 19) who received allo-HCT from 2018 to 2020. The primary end-points assessed were incidence and severity of 1-year aGVHD and cGVHD. Secondary end-points included day+100 mortality, 1-year overall survival (OS), 1-year RFS, 1-year transplant-related mortality (TRM), and 1-year GRFS, defined as grade 3-4 acute GVHD, systemic therapy-requiring chronic GVHD, relapse, or death in the 1-year post-HCT period. Results: A total of 65 adult MRD and MUD allo-HCT recipients and 53 haplo-HCT patients were reviewed. Of the MRD/MUD patients evaluated, approximately 51% (n = 33) were female and 49% (n = 32) were male. The age range was 20-69 years old (median = 46), and the most common diseases included ALL (46%), AML (31%), MDS (11%), and others (i.e. lymphoma, aplastic anemia (AA), myelofibrosis) (12%). 34% (n = 22) of patients received PTCy on D+3 and D+4 with tacrolimus/MMF/ on D+5 as GVHD prophylaxis and 66% (n = 43) of patients received MTX/tacrolimus on D+1, +3, +6, and +11 as GVHD prophylaxis. All haplo-HCT patients received standard PTCy/tacrolimus/MMF. Stem cell source was primarily PBSC except in HLH and AA patients. The PTCy group had more MUD allo-HCT (64%), degree of antigen mismatch (56%), and median age of 50.5 years compared with the MTX group at 44%, 47%, and 44 years respectively. 70% in the MTX group received MAC compared with 45% in the PTCy group. The haplo group had similar demographics to the MTX group. The mean CD34 cell doses in the PTCy, MTX, and haplo groups were 4.87, 5.36, and 7.24x106 cells/kg respectively. Incidences of total GVHD, aGVHD, and aGVHD grade 3 or 4 in the PTCy group were 55%, 50%, and 4.5% respectively compared with 65%, 35%, and 7% in the MTX group, though not significant. The haplo group had 68%, 55%, and 1.9% respectively. Incidence of total cGVHD and cGVHD requiring systemic therapy in the PTCy group was 4.5% and 0% respectively compared with 30% (p = .02) and 23% (p =.01). The haplo group had 13% and 1.9% respectively. Day+100 mortality, 1-year OS, 1-year RFS, 1-year TRM, and 1-year GRFS in the PTCy group were 0%, 80%, 60%, 0%, and 64% respectively compared with 7%, 88%, 90%, 7.3%, and 59%. The haplo group had 3.8%, 86%, 89%, 14%, and 66%. In a univariate analysis, factors significantly associated with GVHD were disease status (p = .0.12) and CD34 dose (p = 0.015) and antigen mismatch (p = 0.04) was associated with increased mortality. Discussion: Our results demonstrate improved overall and extensive cGVHD outcomes in the PTCy group and thus an improvement in 1-year GRFS. Furthermore, incidence and severity of 1-year cGVHD in this group are improved when compared with previously reported outcomes. 1-year GRFS reported in De Jong et al 2019 was 45% and 1-year GRFS reported for all groups in our study is higher at 66%, 64%, and 59% for the haplo, PTCy, and MTX groups respectively. Although this was not significant, it may be clinically meaningful given the significant improvement in extensive GVHD and improvement in all other secondary end-points except 1-year OS and RFS. Furthermore, the PTCy group had a higher percentage of mismatched antigens yet demonstrated superior outcomes. 1-year OS and RFS were superior in the MTX group however this is likely due to sample size differences. The improved extensive cGVHD and GRFS outcomes observed using PTCy/tacrolimus/MMF in the MRD/MUD setting should continue to be evaluated and currently there is an ongoing prospective, randomized study to further investigate. Disclosures Yaghmour: Jazz: Consultancy, Speakers Bureau; Takeda: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Astellas: Consultancy, Speakers Bureau; Alexion: Consultancy, Speakers Bureau; Agios: Consultancy, Membership on an entity's Board of Directors or advisory committees; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees.

Impact of CD34 Cell Dose and Conditioning Regimen on Outcomes after Haploidentical Donor Hematopoietic Stem Cell Transplantation with Post-Transplantation Cyclophosphamide for Relapsed/Refractory Severe Aplastic Anemia

Severe aplastic anemia (SAA) is a life-threatening disease that can be cured with allogeneic cell transplantation (HCT). Haploidentical donor transplantation with post-transplantation cyclophosphamide (haplo-PTCy) is an option for patients lacking an HLA-matched donor. We analyzed 87 patients who underwent haplo-PTCy between 2010 and 2019. The median patient age was 14 years (range, 1 to 69 years), most were heavily transfused, and all received previous immunosuppression (25% without antithymocyte globulin). Almost two-thirds (63%) received standard fludarabine (Flu)/cyclophosphamide (Cy) 29/total body irradiation (TBI) 200 cGy conditioning, and the remaining patients received an augmented conditioning: Flu/Cy29/TBI 300-400 (16%), Flu/Cy50/TBI 200 (10%), or Flu/Cy50/TBI 400 (10%). All patients received PTCy-based graft-versus-host disease (GVHD) prophylaxis. Most grafts (93%) were bone marrow (BM). The median duration of follow-up was 2 years and 2 months. The median time to neutrophil recovery was 17 days. Primary graft failure occurred in 15% of the patients, and secondary or poor graft function occurred in 5%. The incidences of grade II-IV acute GVHD was 14%, and that of chronic GVHD was 9%. Two-year overall survival and event-free survival (EFS) were 79% and 70%, respectively. EFS was higher for patients who received augmented Flu/Cy/TBI (hazard ratio [HR], .28; P=.02), and those who received higher BM CD34 cell doses (>3.2×10E6/kg) (HR, .29; P=.004). The presence of donor-specific antibodies before HSCT was associated with lower EFS (HR, 3.92; P=.01). Graft failure (HR, 7.20; P < .0001) was associated with an elevated risk of death. Cytomegalovirus reactivation was frequent (62%). Haploidentical HCT for SAA is a feasible procedure; outcomes are improved with augmented conditioning regimens and BM grafts with higher CD34 cell doses.