HLA-allele Match Research Articles

Selection of Cord Blood Unit by CD34+ Cell and GM-CFU Numbers and Allele-Level HLA Matching in Single Cord Blood Transplantation

In Japan, only single-unit cord blood transplantations (CBTs) are typically performed, and their number has increased over the last 23 years, with ongoing improvement in results. In most cases, CBTs with multiple HLA mismatches are used, owing to a low HLA barrier, and lower engraftment rate is a problem that must be overcome. Here, as part of an effort to improve guidelines for the selection and processing of CB units for transplantation, we sought to assess the present status of CBT in Japan and to elucidate factors contributing to the favorable outcomes, focusing in particular on selection by cell components of CB unit and HLA allele matching. We conducted a nationwide study analyzing 13,443 patients who underwent first CBT between in Japan between December 1997 and December 2019 using multivariate regression analysis. Both patient- and transplantation-related variables, such as age and Hematopoietic Cell Transplantation Comorbidity Index, as well as selected CB unit characteristics, were included in the analysis. The interaction analysis elucidated that CB unit selection favoring higher counts of CD34+ cells and granulocyte macrophage colony-forming units (GM-CFU)/kg, but not of total nucleated cells, contributed to improved engraftment after transplantation. Moreover, a higher CD34+ cell dose was associated with improved overall survival (OS). Distinctive HLA allele matching was observed. A 0 or 1 HLA allele mismatch between patient and donor had favorable engraftment and carried significantly lower risks of acute GVHD and chronic GVHD but had a significantly higher leukemia relapse rate, compared with a 3-HLA allele mismatch. HLA-DRB1 mismatches were associated with reduced risk of leukemia relapse. Notably, the number of HLA allele mismatches had no incremental effect on engraftment, acute and chronic GVHD, or relapse incidence. As a result, 5-year overall survival did not differ significantly among patients receiving CB units with 0 to 7 HLA allele mismatches. The main points of CB unit selection are as follows. First, selection according to a higher number of CD34+ cells/kg and then of CFU-GM/kg is recommended to obtain favorable engraftment. A unit with .5 × 105 CD34+ cells/kg is minimally acceptable. For units with a CD34+ cell dose of .5 to 1.0 × 105 cells/kg, applying the parameter of ≥20 to 50 × 103 GM-CFU/kg (66.5% of transplanted CB units in this cohort) is associated with a neutrophil engraftment rate of approximately 90%. A unit with ≥1.0 × 105 CD34+ cells/kg can achieve a ≥90% mean neutrophil engraftment rate. Subsequently, HLA allele matching of HLA-A, -B, -C, and -DRB1 at the 2-field level should be searched for units with 0 or 1 HLA allele mismatch in the host-versus-graft direction for favorable engraftment. Units with 2 to 6 HLA allele mismatches are acceptable in patients age ≥15 years and units with 2 to 4 HLA allele mismatches are acceptable in patients age ≤14 years. Units with HLA-DRB1 and/or -B allele mismatch(es) might not be preferable owing to an increased GVHD risk. Our analysis demonstrates that single-unit CBT with the selection of adequate CD34+/kg and GM-CFU/kg and HLA allele matching showed favorable outcomes in both pediatric and adult patients.

Long-Term Follow-up of Adult Double Unit Cord Blood (CB) Transplantation (dCBT) Recipients Reveals High Rates of Progression-Free Survival after a Novel Cy/ Flu/ Thio/ TBI 400 Intermediate Intensity Conditioning Regimen

Background: CB transplantation (CBT) can be associated with the advantages of low rates of chronic GVHD & relapse. These benefits, however, can be offset by early post-transplant transplant-related mortality (TRM). Therefore, we have investigated CBT after a novel intermediate intensity, reduced toxicity myeloablative cyclophosphamide 50 mg/kg, fludarabine 150 mg/m2, thiotepa 5-10 mg/kg, 400 cGy TBI regimen in an effort to reduce early organ toxicity while also maximizing engraftment & disease control.Methods: We analyzed CBT outcomes, including patient (pt) & graft characteristics associated with TRM, relapse and progression-free survival (PFS), in adult CBT recipients transplanted with this approach. Eligible pts were first allograft recipients </= 65 yrs transplanted for acute leukemia/ MDS/ MPD (</= 10% blasts pre-CBT), B-cell NHL or Hodgkin lymphoma. Graft-versus-host disease (GVHD) prophylaxis was with cyclosporine-A/ mycophenolate mofetil (no ATG).Results: 139 consecutive pts [74 (53%) non-European, 84 (60%) CMV seropositive, median age 51 yrs (range 23-65), median weight 83 kg (range 49-136)] were transplanted 10/2007-12/2016. Diagnoses included 102 acute leukemia, 22 MDS/ MPD, 15 B-cell NHL/ HL. All received double unit grafts [median donor recipient 8-allele HLA-match 5/8 (range 2-8), median infused CD34+ dose 1.0 x 105/kg/unit (range 0.2-8.6)]. 54 (39%) CB grafts were supplemented with haplo-identical CD34+ cells as a myeloid bridge. The incidence of CB engraftment was 96% (95%CI: 91-99). Day 180 incidence of grades II-IV & III-IV aGVHD was 78% (95%CI: 70-84) & 21% (95%CI: 15-28), respectively. 1-yr cGVHD was 8% (95%CI: 4-14). Cumulative incidence of day 180 TRM was 12% (95%CI: 7-17) & 21% (95%CI: 14-29) at 3 yrs. 11% (95%CI: 6-18) of pts relapsed by 3 yrs post-CBT. With a median survivor follow-up of 2.7 yrs (range 6.5 months-9.5 yrs), the 3-yr overall survival is 71% (95%CI: 63-80) & PFS is 67% (95%CI: 59-76). 3-yr PFS in 75 acute leukemia CR1 pts is 66% versus 74% in 27 other disease status pts (p = 0.574). 3-yr PFS in 23 FLT-3 mutated AML pts is 83%. The 3-yr PFS is 62% in 22 MDS/ MPD pts & 67% in 15 NHL/ HD pts. The revised disease risk index (rDRI) was not associated with TRM, relapse or PFS (Figure, Table). By contrast, pts with an age adjusted hematopoietic cell transplant-comorbidity index (aaHCT-CI) 0-2 (n = 54) had very low day 180 TRM [4% (95%CI: 1-11)] & high PFS [81% (95%CI: 71-94)] whereas the 85 pts with high aaHCT-CI (median 4, range 3-9) had a day 180 TRM of 17% (95%CI: 10-25) & 3-yr PFS of 58% (95%CI: 48-71). In multivariate analysis of TRM, aaHCT-CI had a HR of 4 (95%CI: 1.4-11.6, p = 0.01) whereas age alone was not significant [HR 1.9 (95%CI: 0.8-4.5), p = 0.12]. In multivariate analysis of PFS, aaHCT-CI HR was 2.4 (95%CI: 1.2-4.7, p = 0.01) whereas for recent pts (CBT 2014-2016) HR was 0.6 (95%CI: 0.3-1.2) although this was not significant (p = 0.17)Conclusions: The 3-yr PFS in this older (median 51 yrs) intermediate intensity dCBT population is very promising. The incidences of cGVHD & relapse are low & DRI was not associated with TRM, relapse or PFS. Notably, addition of haplo-identical cells & better CB HLA-match was not associated with better PFS, & older age (51-65 yrs), CMV sero-positivity & non-European ancestry did not adversely affect PFS. Notably, day 180 TRM in recent pts is 9%. While high aaHCT-CI pts require additional strategies to reduce early post-CBT complications, given PFS is excellent in low aaHCT-CI CBT recipients (39% of pts in this analysis), survival comparisons of intermediate intensity dCBT in this population versus all other HSC sources is warranted. CB can also be attractive in pts with high risk disease given its rapid availability. [Display omitted] Disclosuresvan den Brink:Seres: Research Funding; Therakos Institute: Other: Speaking engagement; PureTech Health: Consultancy; Jazz Pharmaceuticals: Consultancy.

Combined impact of HLA-allele matching and the CD34-positive cell dose on optimal unit selection for single-unit cord blood transplantation in adults

The combined effects of HLA-allele matching at six-loci (HLA-A, -B, -C, -DRB1, -DQB1, and -DPB1) and CD34+ cell dose on clinical outcomes were analyzed in 1,226 adult cases with single-unit unrelated cord blood transplantation. In the six-loci analysis, low HLA-allele matches did not significantly increase the overall mortality compared to higher matches, whereas in the five-loci analysis excluding HLA-DPB1, they caused a higher overall mortality (HR 1.42, p = .002), possibly due to the graft-versus-leukemia effect of HLA-DPB1 mismatches. A lower CD34+ cell dose (<.50 × 105/kg) resulted in higher mortality and lower engraftment; these inferior outcomes were offset by high HLA-allele matches (7-10/10 match), while the inferior outcomes of low HLA-allele matches were improved by increasing the CD34+ cell dose. Consideration of the combined effects of the CD34+ cell dose and HLA matching may expand the options for transplantable units when HLA matching or the CD34+ cell dose is inadequate.

Frequencies and haplotype associations of non-expressed HLA alleles in ethnically diverse populations on the National Marrow Donor Program’s Be The Match Registry

HLA allele matching is critical to successful bone marrow transplantation between a patient and donor. Non-functional HLA alleles, so called ‘null alleles’, are not well described within a large population of well HLA-typed ethnically diverse individuals despite their impact on donor selection. A retrospective analysis was performed on 833,789 unrelated donors (URDs) in the National Marrow Donor Program’s Be The Match Registry® typed for HLA-A, -B, -C, -DRB1, -DQB1, and -DPB1 by next-generation DNA sequencing. Results showed that null alleles occur in low frequency (2.30E−04) compared to expressed alleles. Their overall frequency ranged from 6.00E−07 to 9.25E−04 with a median of 1.20E-06. The expected allele associations were commonly observed for HLA-A*24:09N, HLA-B*51:11N, and HLA-C*04:09N; however, associations outside of the expected were also observed. Notably, 82% of the National Marrow Donor Program Registry URDs carrying HLA-A*24:11N showed a different HLA-C allele association, HLA-C*05:01, compared to the allele described by prior published work characterizing German donor populations, HLA-C*04:01. The frequencies of these observed null alleles and linkage disequilibrium information could be invaluable and helpful in guiding the HLA testing decisions.

Addition of Tocilizumab to Cyclosporine-a/ Mycophenolate Mofetil (CSA/ MMF) Graft-Vs-Host Disease (GVHD) Prophylaxis Significantly Abrogates Pre-Engraftment Syndrome (PES) &amp; Severe Acute Gvhd after Adult Double Unit Cord Blood Transplantation (dCBT)

Background Anti-thymocyte globulin-free dCBT is associated with high rates of acute GVHD (aGVHD) especially involving the GI tract. Investigation of augmented aGVHD prophylaxis is indicated. Methods We are investigating the addition of a single dose of tocilizumab 8 mg/kg (day -1) to CSA/ MMF (starting day -3) aGVHD prophylaxis in adult patients (pts) with hematologic malignancies undergoing dCBT with intermediate intensity Cy 50/ Flu 150/ Thio 10/ TBI 400 conditioning (NCT03434730). Outcomes of the first 26 patients (with survivor follow-up of at least 100 days) were analyzed & compared to 54 dCBT historic controls transplanted with identical conditioning & only CSA/ MMF. All patients received letermovir if CMV seropositive. Results 26 pts [median age 47 years (range 26-60), median weight 82 kg (range 59-125), 11 AML, 8 ALL, 2 MPAL, 3 MDS/ CML, 2 NHL, median age-adjusted HCT-CI 2.5 (range 0-6)] received dCB grafts with a median CD34+ cell dose of 1.5 × 105/kg/unit (range 0.23-5.94) & median unit-recipient 8-allele HLA-match of 5/8 (range 3-6). One patient had graft failure in the setting of low graft viability/ disseminated adenovirus & a second pt had early transplant-related mortality (TRM) with incomplete count recovery. The remaining 24 patients engrafted at a median of 24 days (range 18-40) for a cumulative incidence of 92% (95%CI:67-98). 88% (95%CI:59-97) of pts engrafted platelets at a median of 43 days (range 32-78). Of evaluable pts, 68% & 83% had 100% single-unit donor chimerism in the blood at days 30 & 100, respectively; single-unit dominance was observed in the remaining cases. Six of 26 pts (23%) developed pre-engraftment syndrome (PES) at a median of 12.5 days, & only 3 of these (12%) required systemic corticosteroids. Additionally, 16 pts (62%) had no neutropenic fever prior to engraftment. The day 100 cumulative incidence of grade II-III & grade III aGVHD was 62% (95%CI:39-78) & 4% (95%CI: Conclusions Tocilizumab-based dCBT appears safe with reduced PES & grade III-IV aGVHD. While many pts developed upper GI aGVHD, the marked reduction in lower GI aGVHD supports preferential reduction of T-cell homing to the lower gut. Investigation of this approach including aGVHD treatment responses, immune recovery & correlative biomarker/ microbiota studies are ongoing.

Evaluation of Cord Blood Total Nucleated and CD34+ Cell Content, Cell Dose, and 8-Allele HLA Match by Patient Ancestry.

How cord blood (CB) CD34+ cell content and dose and 8-allele HLA match vary by patient ancestry is unknown. We analyzed cell content, dose, and high-resolution HLA-match of units selected for CB transplantation (CBT) by recipient ancestry. Of 544 units (286 infused, 258 next-best backups) chosen for 144 racially diverse adult patients (median weight, 81 kg), the median total nucleated cell (TNC) and CD34+cell +contents were higher for Europeans than for non-Europeans: 216 × 107versus 197×107 (P=.002) and 160 × 105 versus 132 × 105 (P=.007), respectively. There were marked cell content disparities among ancestry groups, with units selected for Africans having the lowest TNC (189×107) and CD34+ cell (122×105) contents. Units for non-Europeans were also more HLA-mismatched (P=.017). When only the 286 transplanted units were analyzed, the adverse effect of reduced cell content was exacerbated by the higher weights in some groups. For example, northwestern Europeans (high patient weight, high unit cell content) had the best-dosed units, and Africans (high weight, low unit cell content) had the lowest. In Asians, low cell content was partially compensated for by lower weight. Marked differences in 8-allele HLA-match distribution were also observed by ancestry group; for example, 23% of units for northwestern Europeans were 3/8 to 4/8 HLA-matched, compared with 40% for southern Europeans, 46% for white Hispanics, and 51% for Africans. During the study period, 20 additional patients (17 non-Europeans; median weight, 98 kg) did not undergo CBT owing to the lack of a suitable graft. CB extends transplantation access to most patients, but racial disparities exist in cell content, dose, and HLA match.

Impact of HLA Allele Mismatch at HLA-A, -B, -C, and -DRB1 in Single Cord Blood Transplantation.

The impact of allele-level HLA mismatch on outcomes of cord blood transplantation has not been well established. We retrospectively analyzed the effects of HLA allele matching at HLA-A, -B, -C, and -DRB1 in cord blood transplantation for acute myeloid leukemia, acute lymphoblastic leukemia, and myelodysplastic syndrome. In multivariate analysis, overall survival (OS) significantly deteriorated in the 4-allele or higher mismatch in pediatric cases (hazard ratio, 1.8 for 4/8 match [reference, 6/8 match] and 2.85 for 3-1/8 match) and the 5-allele or higher mismatch in adult cases (hazard ratio, 1.23 for 3-0/8 match). Incidence of grade Ⅲ to Ⅳ acute graft-versus-host disease was low in the 8/8 match and 1-allele mismatch in pediatric cases (hazard ratio, 0.19 for 8/8 match and 0.41 for 7/8 match) and the 8/8 match in adult cases (hazard ratio, 0.41 for 8/8 match). On the other hand, a higher incidence of relapse was noted in the 8/8 match in adults (hazard ratio, 1.53). The incidence of neutrophil and platelet engraftment decreased in the 3-allele or higher mismatch in adults. In subgroup analysis of graft-versus-host disease prophylaxis in adult cases, a deteriorating effect on OS of HLA 5-allele or higher mismatch was more significant in cases with calcineurin inhibitor with methotrexate than with mycophenolate mofetil. These results suggest that allele-level HLA mismatch affects the outcomes of cord blood transplantation. Information on HLA allele matching at HLA-A, -B, -C, and -DRB1 may be useful for cord blood unit selection.

Abstract A012: SV-BR-1-GM, a whole-cell targeted immunotherapy for advanced breast cancer: Pharmacodynamic markers of response

Abstract Background: SV-BR-1-GM is a GM-CSF-engineered breast cancer cell line employed – after irradiation – as a targeted immunotherapy for advanced breast cancer. Tumor regressions at metastatic sites have been observed, most notably in patients with HLA allele matches to the cell line. We are assessing SV-BR-1-GM in the phase IIa portion of a phase I/IIa clinical trial in metastatic and locally recurrent breast cancer (ClinicalTrials.gov identifier NCT03066947). Additionally, we are co-developing a companion diagnostic (BriaDX™) to identify patients likely to respond to SV-BR-1-GM. Currently, BriaDX™ consists of HLA typing; however, we have begun assessing biomarkers in sera, lymphocyte characteristics, circulating tumor cells (CTCs), and cancer-associated macrophage-like cells (CAMLs) from patients collected at baseline and after inoculation of SV-BR-1-GM to layer in additional components to improve accuracy, with the number/subtyping of CTCs and CAMLs being prognostic indicators. Methods: Subjects are pretreated with low-dose cyclophosphamide to reduce immune suppression. SV-BR-1-GM is inoculated intradermally with follow-up local injections of IFNα2. Cycles are every 2 weeks x 3, then monthly. HLA typing was conducted via LabType R-SSO Kits (One Lambda). Cytokines were measured via single- or multiplex assays. Anti-SV-BR-1 antibodies were determined by incubation of SV-BR-1 cells with diluted patient sera followed by staining with a fluorescently-labeled anti-IgG antibody and detection by flow cytometry. CTCs and CAMLs were evaluated by CellSieve™ at Creatv MicroTech. Results: To date, 16 clinical trial subjects have been inoculated with the SV-BR-1-GM regimen as rescue immunotherapy. All were treatment refractory and had received a median of 4.5 prior chemo/biologic therapy regimens (range 1-13). Two of the 16 patients remained on study for ≥3 months (5 cycles) with 4 patients currently on study not having reached the 3-month evaluation time point. Objective regression of tumor was seen in 2 subjects. One subject had virtually complete regression of 20 of 20 lung metastases noted at 3 and 6 months (but with progressive bone and liver metastases). Another subject had improvement of chest wall metastases and quality of life but expired due to nontreatment-related causes. Response appeared to correlate with HLA allele-matching to SV-BR-1-GM. Anti-SV-BR-1 antibody titers increased in several patients. Among the cytokines assessed, interleukin (IL)-8 levels increased in HLA-DRB3 allele-matched subjects after SV-BR-1-GM inoculation. Of 15 patients evaluated, CTCs were present in 6 patients at baseline while CAMLs were present in all 15. Five of 5 patients evaluated for PD-L1 expression had mostly low-to-medium expression of PD-L1 on their CTCs/CAMLs. In the patient who had regression of lung metastases but progression of liver metastases, PD-L1 expression and maximum CAML size increased, but the number of CAMLs decreased during treatment. CAML number also decreased in a patient who reached the 3-month evaluation visit without progression and in a patient with inflammatory breast cancer who dropped out due to worsening inflammation. Conclusions: In addition to the patients’ HLA types, several pharmacodynamic parameters correlated with tumor regression and/or HLA matching status. CTCs or CAMLs are frequently detectable in this population, and PD-L1 expression appears common on these cells. Both CAML number and size appear to correlate with response, though larger studies are needed. Future steps include evaluation of SV-BR-1-GM with checkpoint inhibitors. Citation Format: Markus D. Lacher, Sanne Graeve, Vivekananda (Vivek) Sunkari, Daniel L. Adams, Cha-Mei Tang, Pete Amstutz, Charles L. Wiseman, George E. Peoples, William V. Williams. SV-BR-1-GM, a whole-cell targeted immunotherapy for advanced breast cancer: Pharmacodynamic markers of response [abstract]. In: Proceedings of the Fourth CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; Sept 30-Oct 3, 2018; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2019;7(2 Suppl):Abstract nr A012.

Evaluation of Cord Blood (CB) TNC & CD34+ Cell Content, Cell Dose & Donor-Recipient 8-Allele HLA-Match By Patient Ancestry: An Analysis of 544 Units in a Racially & Ethnically Diverse Patient Population

Introduction Optimal CB unit selection incorporates TNC & CD34+ cell dose & 8-allele donor-recipient HLA-match. How graft characteristics for these parameters vary by patient (pt) race/ ethnicity, however, is unknown. Methods We analyzed cryopreserved TNC & CD34+ cell content, the cell dose incorporating pt weight, & HLA-match of infused & backup (reserved but not shipped) units by pt ancestry in CB transplant (CBT) recipients transplanted 7/2013-6/2018. Units were chosen based on banking practices, TNC & CD34+ dose & 4-6/6 & 8-allele HLA-match. Patient (pt) racial/ ethnic origins were prospectively obtained & grouped per Barker J. et al, BBMT 2010. Results The characteristics of 544 units chosen for 144 diverse CBT recipients by pt ancestry are shown (Table 1). 286 units were infused (142 doubles, 2 singles) & pts had a total of 258 backup units (0-2/pt). The median TNC content of units for Europeans was higher than for Non-Europeans (216 vs 197, p = 0.002). Units for NW Europeans had the highest median TNC content with lowest in units for Africans & White Hispanics. Units chosen for Europeans also had a higher median CD34+ cell content than Non-Europeans (160 vs 132, p = 0.007). Units for NW Europeans had the highest & units for Africans the lowest median CD34+ content. Median TNC/kg was similar in units for European & Non-European pts (2.7 vs 2.5, p = 0.11) & differences between groups were not marked. However, there was a trend for units for Europeans having a higher median CD34+ dose than units for Non-Europeans (1.9 vs 1.7, p = 0.057) with disparity between groups. Although the median 8 allele HLA-match was 5/8 for units chosen for both European & Non-European pts, units identified for non-Europeans were more mismatched (p = 0.017). When the 286 transplanted units (considered the best) were analyzed, the median TNC & CD34+ contents of units were higher for Europeans than non-Europeans (232 vs 216, p = 0.022, & 181 vs 152, p = 0.009). As shown in Table 2, while there were no overall differences in the median TNC & CD34+ doses of units for Europeans & non-Europeans, differences in cell content combined with differences in weights resulted in TNC & CD34+ dose disparities within ancestry groups. For example, NW Europeans (high weight, high CD34+ content) had the highest CD34+ doses; lower content in Asian pts was partially compensated for by low weight; African pts (high weight, low content) had the lowest doses. Finally, there was marked differences in HLA-match distribution by ancestry group: eg only 23% of units for NW Europeans were 3-4/8 vs 40% for S. Europeans, 46% for white Hispanics & 51% for Africans. Conclusions CB extends transplant access to minorities but differences in cellular content translates to many ancestry groups pts having access to only lower dosed units. There are also marked racial/ ethnic disparities in HLA-match. This data supports continued funding of banks to further increase the CB inventory.

Addition of Tocilizumab to Cyclosporine/ MMF for Acute Graft-Vs-Host Disease (aGVHD) Prophylaxis in Adult Double Unit Cord Blood Transplant (dCBT) Recipients: Promising Preliminary Results of a Phase II Clinical Trial.

Background Adult dCBT recipients are at significant risk for aGVHD especially involving the GI tract. Investigation of augmented prophylaxis is indicated. Methods Based on adult donor allograft data (Kennedy et al, Lancet 2015; Drobyski et al Haematologica 2018), we are investigating the addition of a single dose of tocilizumab 8 mg/kg (cap 800mg) on day -1 to standard cyclosporine/ MMF starting day -3 in adult patients (pts) with hematologic malignancies undergoing intermediate intensity Cy 50/ Flu 150/ Thio 10/ TBI 400 dCBT. We report an interim analysis of the first 16 pts of a 27 pt phase II trial (NCT03434730). All pts received standard bacterial/ fungal prophylaxis & Letermovir if CMV seropositive. Results 16 pts [median 50 years (range 27-59), median 85 kg (range 59-125), 6 AML, 5 ALL, 2 MPAL, 2 MDS, 1 CML, median aaHCT-CI of 3 (range 0-6)] received double-unit CB grafts with a median CD34+ cell dose of 1.33 × 105/kg/unit (range 0.24-3.83) & median unit-recipient 8-allele HLA-match of 5/8 (range 3-6). Pt outcomes are shown (Table). All (100%) pts engrafted with a median neutrophil recovery of 26 days (range 19-40). 94% of pts engrafted platelets (median 44 days, range 32-59). All pts had single unit dominance (median day 28 blood winning unit chimerism 100% (range 58-100). Prior to engraftment, 11/16 (69%) had no neutropenic fever, 3/16 (19%) pts had fever with bacteremia, 1 pt (6%) had febrile neutropenia (duration 2 days) responding to antibiotics, & 1 pt (6%) had initial fever due to bacteremia followed by fever/ rash attributed to pre-engraftment syndrome (PES). An additional 2 pts developed rash without fever prior to engraftment attributed to PES. Thus, a total of 3/16 (19%) pts had PES (onset ranging 12-14 days). Ten pts developed grade II aGVHD (median onset 45 days, range 26-81) for a cumulative incidence of 63% (95%CI: 33-82). This was limited primarily to skin &/or the upper gut with one pt having stage I lower GI. No pt has developed grade III-IV aGVHD & no pt has had stage II-IV lower GI aGVHD to date (Figure). With a median follow-up of 147 days (range 74-214), 15 pts are alive & disease-free (1 death due to HHV-6 pneumonitis). Conclusions Preliminary data suggests tocilizumab is safe with no adverse effects upon engraftment or unit dominance. Tocilizumab mitigates PES (expected incidence 65% in dCBT controls, Bhatt et al, ASBMT 2019). Expected days of febrile neutropenia were also reduced especially given the prolonged neutrophil recovery. Notably, lower gut aGVHD appears markedly reduced with no cases of grade III-IV aGVHD or aGVHD mortality to date. Our findings appear consistent with the published adult donor data. Overall, one tocilizumab dose has improved the early post-dCBT morbidity & investigation of this promising & potentially cost-effective approach is ongoing.

Engrafting Unit-Recipient HLA-Allele Mismatch Is Not Associated with an Increased Risk of Transplant-Related Mortality (TRM) or Inferior Progression-Free Survival (PFS) after Double Unit Cord Blood (CB) Transplantation (dCBT) in Adults with Hematologic Malignancies

Background The less stringent CB HLA-match requirement extends allograft access. The extent to which HLA-mismatch can adversely affect CBT outcomes & the maximum permitted HLA-mismatch, however, are not established. Methods We analyzed TRM, relapse & PFS after cyclophosphamide 50 mg/kg, fludarabine 150 mg/m2, thiotepa 5-10 mg/kg, 400 cGy TBI dCBT in adults with hematologic malignancies. Eligible patients (pts) were 1st allograft recipients ≤ 65 years transplanted 1/2014 - 12/2017. TNC & CD34+ dose were typically given priority over HLA-match in unit selection. Results 102 pts [51 (50%) non-European, median 50 years (range 21-65), median 80 kg (range 36-137), 71 acute leukemias & 17 CML/ MPD/ MDS (all ≤ 10% blasts pre-CBT), 14 NHLs] received double unit grafts. The majority of units [181 (89%)] were 4/6 matched. At high resolution the unit-recipient 8-allele HLA-match was a median of 5/8 (range 3-7). The median infused viable CD34+ dose was 1.3 × 105/kg/unit (range 0.2-8.6). 48 (47%) pts also received haplo-identical CD34+ cells as a myeloid bridge. 97% (95%CI 90-99) engrafted with CB. All pts had a dominant unit (1 early death excluded). Day 180 grade II-IV & III-IV aGVHD were 89% (95%CI 81-94) & 23% (95%CI 15-31), respectively. 1-yr cGVHD was 4% (95%CI 1-9). Day 180 TRM was 9% (95%CI 4-15) & 14% (95%CI 8-22) at 2 yrs. 11% (95%CI 6-19) of pts relapsed by 2 yrs. With a median survivor follow-up of 2 yrs 3 months (range 6 - 51), 2-yr OS is 82% (95%CI 75-90) & PFS is 74% (95%CI 66-84). Causes of death were transplant-related in 16 pts [6 aGVHD, 4 infection (2 viral, 1 bacterial, 1 fungal), 4 organ failure, 1 graft failure, 1 unknown] & relapse in 4 pts. By 2-yrs, engrafting unit-recipient HLA-allele match had no association with TRM or PFS ( Figure ). Analysis of the association between recipient/ graft variables & TRM/ relapse/ PFS are shown ( Table ). Pts In multivariate analysis, aaHCT-CI was associated with worse PFS [HR 2.82 (1.28-6.25) if score 4-9 vs 0-3, p = 0.01]; neither rDRI [HR 1.21 (0.54-2.69) if high-very high vs low-intermediate, p = 0.64] nor engrafting unit-recipient HLA-match [HR 2.06 (0.89-4.74) if 5-7/8 vs 3-4/8 matched (p = 0.09] were significant. Conclusions dCBT with mismatched units facilitates allograft access extension & has a high PFS. While further investigation of the CD34+ dose – HLA-mismatch interaction is required, this supports unit selection prioritizing quality & dose in adults to optimize engraftment. Finally, this data supports CBT in younger pts, those with low 0-3 aaHCT-CI, or high rDRI given the high 2-yr PFS in such pts.

Letermovir Prophylaxis Demonstrates High Efficacy in Adult Cytomegalovirus (CMV) Seropositive Cord Blood Transplant (CBT) Recipients: A Comparison with Pre-Letermovir Era CBT Controls

Background CMV seropositive CBT recipients have a high risk of CMV infection. Early pre-emptive therapy is required to avoid CMV disease but is associated with significant toxicities. Methods This analysis compares the day +100 incidence & severity of clinically significant CMV infection (viremia leading to pre-emptive treatment or disease) in CMV seropositive CBT adult patients (pts) who received letermovir prophylaxis transplanted 12/2017-6/2018 vs historic controls transplanted 3/2013-12/2017. Control pts received ganciclovir prophylaxis days -7 to -2 then standard dose acyclovir. Letermovir pts received standard dose acyclovir & started letermovir IV or PO on day +7 & continued beyond day +100. All pts received uniform intermediate intensity Cy 50 mg/kg / Flu 150 mg/m2/ Thio 5-10 mg/kg / TBI 400 cGy conditioning with CSA/ MMF. Pts were monitored by qPCR twice weekly from approximately day +14-60 & then 1-2 x/weekly days +60-100. Results 62 [median age 51 years (range 23-66), 46 leukemia, 7 MDS/ MPD, 9 NHL/ HL] historic control pts received double unit grafts with a median unit-recipient HLA-allele match of 5/8 (range 2-7). By day +100, 51 pts developed clinically significant CMV infection for a day +100 cumulative incidence of 82% (95%CI: 70-90). The median viremia onset was 34 days (range 5-74) & 5 pts developed CMV disease by day +100 (3 pulmonary, 2 GI). Initial therapy was with foscarnet in 28 pts & ganciclovir/ valganciclovir in 23. Clinically significant therapy toxicities (renal &/or myelosuppression) were observed in 38/51 (75%) pts (Table 1). By day +100, CMV caused or contributed to 3 pulmonary deaths. 10 pts [median age 48 years (range 24-59), 9 leukemia, 1 MDS/ MPD, median 5/8 (range 3-6) unit-recipient HLA-match] received letermovir prophylaxis (8 IV, 2 PO) (Table 2). All pts engrafted. The day +100 cumulative incidence of clinically significant CMV infection was 0% (p Conclusions This analysis suggests letermovir prophylaxis is highly effective at mitigating CMV disease, CMV-related mortality, & the need for toxic CMV therapies. Moreover, it has been well tolerated in CBT recipients. While further detailed investigation in a larger population is required, this data is very promising & the extent of the benefit suggests that letermovir could be a cost-effective new standard of care in adult CBT. The duration of needed prophylaxis beyond day +100 in CBT recipients also requires investigation.

An Analysis of the Correlation between Gastro-Intestinal (GI) Symptoms, Macroscopic Appearance, Histology & Acute Gvhd (aGVHD) Treatment Responses in Cord Blood Transplant (CBT) Recipients: Significant Implications for aGVHD Management

Background GI symptoms are common after CBT & GI aGVHD is frequent. The correlation between symptoms, macroscopic appearance (macro), histology, aGVHD severity & therapy response, however, is not established. Methods We analyzed 1st endoscopies done days +21-180 in engrafted adult double unit CBT recipients transplanted 10/2009-12/2017 with Cy 50/ Flu 150/ Thio 5-10/ TBI 400 & CSA/ MMF. All patients (pts) received fungal prophylaxis, early CMV pre-emptive therapy & C. difficile/ viral PCR stool assays (& blood for adenovirus) were routinely performed. Abnormal histology was defined as mild (grade 1-2) vs severe (grade 3-4). Results Of 156 pts, 88 pts (56%) [median 49 years (range 22-66), 65 leukemia, 5 MDS/ MPD, 18 NHL/ HL] were scoped. Their median donor-recipient HLA-allele match was 5/8 (range 3-7) & 36 (38%) pts also received haplo-CD34+ cells. Pts had 44 upper, 2 lower & 42 combined upper/ lower scopes at a median of 52 days (range 22-176) post-CBT. Of 86 pts who had upper scopes (Table 1), 67/86 (78%) were treated for upper GI aGVHD & only 3 had infection (Figure). The majority (51/67,76%) of aGVHD treated pts had normal macro appearance & the majority (49/67, 73%) had aGVHD compatible histology (typically apoptotic epithelial cells, mild in all but 2). Overall, the majority of treated pts (48/67, 72%) had a day 28 CR (37 budesonide, 11 high dose corticosteroids). Of 18 treated pts with normal macro & histology, 11 had CR & 7 PR. Nearly all (40/44, 91%) pts who had lower GI scopes (Table 2) were treated for aGVHD & none had infection (Figure). Most (33/40, 83%) were stage I-II ( Conclusions With pre-emptive CMV therapy, yeast prophylaxis, & stool PCR studies, the majority of CBT pts who required endoscopies had aGVHD & infection was very rare. This was especially true in pts with diarrhea. Normal mucosal appearance was frequent in aGVHD treated pts & nearly all pts with diarrhea & abnormal macro had aGVHD. Most had aGVHD compatible histology (usually mild). Notably, 9/23 treated pts with normal histology only had a PR supporting aGVHD is a clinical diagnosis. Moreover, pts with severe histologic abnormality were at high risk for PR/ refractory disease. This data supports early corticosteroid therapy if aGVHD compatible symptoms & not waiting for biopsy results. This is critical in pts with diarrhea. Correlation of this data with serum biomarkers & microbiota to improve the efficiency of diagnosis & risk stratification are needed.

Evaluation of Cord Blood (CB) Unit TNC & CD34+ Cell Content & Donor-Recipient High-Resolution 8 HLA-Allele Match By Patient Ancestry: An Evaluation of 513 CB Units in a Racially & Ethnically Diverse Population of Adults with Hematologic Malignancies

Introduction: Optimal CB unit selection guidelines recommend consideration of CD34+ cell dose & 8-allele donor-recipient HLA-match. How graft characteristics for these parameters vary by patient (pt) race/ ethnicity, however, is not known.Methods: We analyzed the infused graft & back-up unit cryopreserved total nucleated cell (TNC) x 107 & CD34+ x 105 cell content, the cell dose (incorporating pt weight), & 4-6/6 & 8-allele HLA-match by pt ancestry in CB transplant (CBT) recipients transplanted 1/2014-6/2018. Units were chosen based on banking practices (e.g. RBC depleted, standard cryo volumes), TNC & CD34+ dose & 4-6/6 & 8-allele HLA-match with dose usually taking priority over match given pt size at our center. The analysis included transplanted units (considered the best choice) & the next best high resolution typed back-up units (reserved but not shipped). Pt racial/ ethnic origins were prospectively obtained by detailed family history & grouped as previously described (Barker J. et al. BBMT 2010).Results: The characteristics of 513 units chosen for 136 CBT recipients by pt ancestry are shown (Table 1). Pts had highly diverse origins including 70 (51%) non-Europeans. The 513 units included 270 units infused as the graft (134 doubles & 2 singles) & 243 back-up units (109 pts had 2 back-ups, 25 pts had one & 2 had none). Thus, 4 best units were analyzed in 109 pts (all double unit recipients), 3 best in 25 pts (all doubles), & 1 unit in 2 pts (both singles). The median weight of the 136 pts was 81 kg. Asian pts (median 68 kg) had a lower weight than other groups. The median TNC content of units for the 66 European pts was higher than that for the 70 Non-Europeans (218 vs 196, p = 0.004). Units chosen for Northwestern (NW) Europeans had the highest median TNC content (235) with lower TNC content in units for Southern Europeans (202), Asian (193), African (191) & White Hispanic (189) pts. Units chosen for European pts also had a higher median CD34+ cell content (162) than Non-Europeans (138), p = 0.004. NW Europeans had units with a higher median CD34+ content (198) & the lowest CD34+ content were those for African (124) & Middle Eastern pts (124). When patient weight was considered, median TNC/kg dose per unit was similar in European and Non-European pts (2.7 vs 2.6, p = NS). Units for NW Europeans had the highest median TNC dose (3.0) whereas those for African pts had the lowest TNC dose (2.4). Units for Europeans had a higher median CD34+ dose (2.0) than Non-Europeans (1.7) although this difference was not significant (p = 0.15). Additionally, similar to TNC dose, median CD34+ dose was highest in units for NW European pts (2.2) & lowest in units chosen for African pts (1.5). 89% of chosen units were 4/6 HLA-matched with no differences between Europeans & non-Europeans. Furthermore, the median 8 allele HLA-match was 5/8 (range 2-8/8) with no overall differences between units for Europeans and Non-Europeans (p = NS).When only transplanted units were analyzed (Table 2), the median TNC & CD34+ contents were significantly lower in non-Europeans than Europeans (238 vs 216, p = 0.01 & 184 vs 160, p = 0.016). Overall, however, units received by Europeans vs non-European pts had similar TNC & CD34+ doses (p = NS). However, differences in the CD34+ content combined with differences in pt weights resulted in disparities in CD34+ doses by ancestry sub-group. NW Europeans (high weight, high CD34+ content) received the best CD34+ doses; lower CD34+ content in Asian pts was compensated for by their lower weight. African pts (high weight, low CD34+ content) received the lowest CD34+ doses. The median 8 allele HLA-match for all was 5/8 (range 3-8/8) with the exception of African pts [median 4/8 (range 3-7/8)]. Moreover, while 108 (40%) of transplanted units were 3-4/8 HLA-matched overall, there were marked differences between pt sub-groups with only 23% of units for NW Europeans being 3-4/8 vs 42% for southern Europeans, 46% for white Hispanics & 53% for Africans.Conclusions: While CB significantly extends transplant access to racial & ethnic minorities, differences in cellular content translates to many minority pts receiving lower dosed units. There are also marked racial/ ethnic differences in HLA-match grade with African pts the most likely to receive highly mismatched units. This data supports ongoing funding of public CB banks to further increase the inventory of high dosed & better matched units for all but especially racial & ethnic minority pts. [Display omitted] DisclosuresShah:Janssen: Research Funding; Amgen: Research Funding. Kernan:National Cancer Institute: Research Funding.

Impact of Homozygous Conserved Extended HLA Haplotypes on Cord Blood Transplantation: Implications for Induced Pluripotent Stem Cell Banking and Transplantation

Induced pluripotent stem cells (iPSC) have the capacity to generate various tissues/organs, and clinical application in autologous settingsin humans has just begun. However, autologous transplantation is hampered by the high time and cost required for the individual production of iPSC. To solve these issues, allogeneic iPSC transplantation (allo-iPS-T) from iPSC banking has been proposed. A candidate for this is iPSC induced from individuals with a homozygous HLA haplotype (HLA-homo), on the basis that HLA-homo iPSC might not be rejected by HLA haplotype-matched patients. Concerns have been raised over whether allo-iPS-T from HLA-homo iPSC induces immunogenicity in clinical settings. Cord blood transplantation (CBT) might be a suitable model for evaluating these concerns, because HLA mismatch CBT from donors with less than two HLA loci mismatches is common, and carries a high engraftment failure rate, with a range of 10% to 20%. Further, cord blood cells are reported to be good source for the production of iPSC. Here, we report an analysis of allogeneic immunogenicity which focuses on engraftment of unrelated transplantation from HLA-homo cord blood.Using Transplant Registry of Japanese Data Center for Hematopoietic Cell Transplantation, we could analyze 5017 Japanese CBT pairs who were typed as HLA-A, -B, -C, -DRB1 alleles at the field 1 and 2 level, and transplanted single unit of cord blood for the first time. Patient age was ranged from 0 to 80 years old (median 50), Patient with AML was 1,113, ALL 884, MDS 514, other hematological malignancy 1,007 and non-hematological malignancy 374. 20 patients were transplanted in 1999-2004, 1,484 in 2005-2010 and 3,513 in 2011-2016. Donor HLA homo and patient HLA hetero combination (homo-hetero) was found in 39 pairs, hetero-homo in 40, homo-homo in 21, hetero-hetero with HLA allele match in HVG vector in 236, hetero-hetero with one allele mismatch in 569 and hetero-hetero with more than 2 allele mismatch in 4112 pairs.Of note, all of 39 HLA homo-hetero pairs obtained neutrophil engraftment (500/μl) at 10-51 day (median 20) after transplantation except one early death pair. Platelet engraftment (20,000/μl) was also obtained in all evaluable 30 pairs. Acute GVHD with grade Ⅱ-Ⅳ and grade Ⅲ-Ⅳ occurred in 17 pairs and 3 pairs of 38 evaluable pairs respectively. Multivariate competing risk regression analysis including clinical factors revealed that homo-hetero pairs (n=39) showed a comparative neutrophil engraftment risk (HR=1.18 p=0.285) compared with HLA allele match hetero-hetero pairs (n=236), favorable risk compared with hetero-hetero pairs with HLA 1 allele mismatch (n=569) and favorable risk compared with hetero-hetero pairs with HLA more than 2 allele mismatch (n=4112). Also, these homo-hetero pairs showed comparative mortality (HR 0.95 P=0.85), platelet engraftment ((HR 1.10 p=0.597) and a tendency of higher risk of acute GVHD (grade 2-4) HR 1.63. p=0.065) compared with HLA allele match hetero-hetero pairs.Further, we obtained detailed information on HLA alleles and haplotypes of HLA-homo. 37 of 39 homo-hetero donors had conserved extended HLA haplotypes (HP-1 n=18, HP=2 n=8, HP=3 n=7, HP-4 n=5, HP-5 n=1) which were ethnicity specific and highly conserved through the entire HLA region, and one of two patient heterogeneous HPs invariably shared the same HP as donor HLA-homo HP, and another non-shared patient HP was mismatched with 1 to 4 HLA alleles of HLA-A, -B, -C and -DRB1 loci in the GVH direction in 33 of these 37 pairs. The KIR2DL1 epitope was donor C1/C1 and patient C1/C1 in all homo-hetero pairs, making the KIR2DL ligand match combination.In conclusion, CBTs from homo-hetero showed a favorable engraftment rate (100%), which confirmed our previous preliminary report for 6 homo-hetero CBTs. HLA alleles of HLA-homo donor were consisted of major conserved extended HLA haplotypes. Those results carry an important implication, namely the possibility that HLA-homo iPSC transplantation results in favorable engraftment, and banking of iPSC with major conserved extended HLA haplotypes is recommended, and patients possessing a single conserved common HLA haplotype have a higher chance of yielding HLA-homo iPSC and promising allo-iPS-T. DisclosuresIchinohe:Janssen Pharmaceutical K.K.: Honoraria; Taiho Pharmaceutical Co.: Research Funding; Bristol-Myers Squibb: Honoraria; MSD: Research Funding; Ono Pharmaceutical Co.: Research Funding; Zenyaku Kogyo Co.: Research Funding; Sumitomo Dainippon Pharma Co.: Research Funding; JCR Pharmaceuticals: Honoraria; Nippon Shinyaku Co.: Research Funding; Repertoire Genesis Inc.: Research Funding; Kyowa Hakko Kirin Co.: Research Funding; Alexion Pharmaceuticals: Honoraria; Celgene: Honoraria; Takeda Pharmaceutical Co.: Research Funding; Otsuka Pharmaceutical Co.: Research Funding; Pfizer: Research Funding; CSL Behring: Research Funding; Eisai Co.: Research Funding; Chugai Pharmaceutical Co.: Research Funding; Novartis.: Honoraria; Mundipharma: Honoraria; Astellas Pharma: Research Funding.

A High Degree of Engrafting Unit-Recipient HLA-Allele Mismatch Is Not Associated with an Increased Risk of Transplant-Related Mortality (TRM) or Inferior Progression-Free Survival (PFS) after Double Unit Cord Blood (CB) Transplantation (dCBT) in Adults with Hematologic Malignancies

Background: While incorporation of HLA-allele matching has highlighted high degrees of CB unit-recipient HLA-disparity, the less stringent HLA-match requirements extends allograft access to many patients without matched adult donors. The extent to which HLA-mismatch can adversely affect CBT outcomes, & the maximum permitted degree of HLA-mismatch, however, are not established.Methods: We analyzed TRM, relapse & PFS after intermediate intensity myeloablative cyclophosphamide 50 mg/kg, fludarabine 150 mg/m2, thiotepa 5-10 mg/kg, 400 cGy TBI double unit CBT in adults transplanted for hematologic malignancies. Eligible patients (pts) were first allograft recipients ≤ 65 years transplanted for acute leukemia/ MDS/ MPD (≤ 10% blasts pre-CBT), B-cell or T-cell lymphomas between 1/2014 - 12/2017. TNC & CD34+ dose were typically given priority over HLA-match in unit selection.Results: 102 pts [51 (50%) non-European, 59 (58%) CMV seropositive, median age 50 years (range 21-65), median weight 80 kg (range 36-137)] were transplanted. Diagnoses included 71 acute leukemias, 17 CML/ MPD/ MDS, 14 B- or T-cell NHLs. All received double unit grafts comprised of 2 (1%) 6/6 units, 21 (10%) 5/6, 181 (89%) 4/6 HLA-match, median unit-recipient 8-allele HLA-match 5/8 (range 3-7), & median infused viable CD34+ dose 1.3 x 105/kg/unit (range 0.2-8.6). Forty-eight (47%) CB grafts were supplemented with haplo-identical CD34+ cells as a myeloid bridge. The cumulative incidence of sustained CB engraftment was 97% (95%CI 90-99) with 2 pts having graft failure. A dominant (engrafting) unit was identified in all pts but 1 who died on day +14. Day 180 incidences of grades II-IV & III-IV aGVHD were 89% (95%CI 81-94) & 23% (95%CI 15-31), respectively. 1-yr cGVHD was 4% (95%CI 1-9). Cumulative incidence of TRM was 9% (95%CI 4-15) at day 180 & 14% (95%CI 8-22) at 2 yrs. 11% (95%CI 6-19) of pts relapsed by 2 yrs. With a median survivor follow-up of 2 yrs 3 months (range 6 - 51), the 2-yr overall survival is 82% (95%CI 75-90) & PFS is 74% (95%CI 66-84). Causes of death were transplant-related in 16 pts [6 aGVHD, 4 infection (2 viral, 1 bacterial, 1 fungal), 4 organ failure, 1 graft failure, 1 unknown] & due to relapse in 4 pts. By 2-yrs post-CBT, engrafting unit-recipient HLA-allele match had no association with TRM or PFS (Figure). Univariate analysis of the association between recipient variables [age, age adjusted hematopoietic cell transplant-comorbidity index (aaHCT-CI), revised disease risk index (rDRI)] & graft variables [engrafting unit-recipient HLA-allele match & infused CD34+ cell dose] & TRM, relapse & PFS are shown (Table). Age & aaHCT-CI were associated with 2-yr TRM with the 50 younger pts (< 50 years), & the 66 pts with aaHCT-CI 0-3, having especially low 2-yr TRM of 5% & 10%, respectively. Neither engrafting unit-recipient HLA-match nor CD34+ dose were associated with TRM. No pt or graft variable was associated with relapse. The only significant variable associated with 2-yr PFS was aaHCT-CI. The 66 pts with a lower aaHCT-CI score of 0-3 had a higher 2-year PFS [82% (95%CI 73-92)] than the 36 high score 4-9 pts [60% (95%CI 46-79)]. rDRI, engrafting unit-recipient 8-allele HLA-match & CD34+ cell dose had no effect. Multivariate analysis of TRM was precluded by too few events. Multivariate analysis of PFS including aaHCT-CI, rDRI & engrafting unit-recipient HLA-match showed high aaHCT-CI was associated with worse PFS [HR 2.82 (1.28-6.25) if score 4-9 vs 0-3, p = 0.01]; neither rDRI [HR 1.21 (0.54-2.69) if high-very high vs low-intermediate, p = 0.64] nor engrafting unit-recipient HLA-match [HR 2.06 (0.89-4.74) if 5-7/8 vs 3-4/8 matched (p = 0.09] were significant.Conclusions: Our finding that a high level of HLA-allele mismatch of the engrafting unit was not significantly associated with TRM or PFS in adult dCBT for hematologic malignancies has multiple implications. It supports the use of units with a relatively high degree of HLA-mismatch in the dCBT setting if needed in these pts. This facilitates extension of allograft access to the majority of pts including minorities. Moreover, the high PFS supports our centers unit selection strategy that gives unit quality & cell dose a priority in adults with malignancies to optimize engraftment. Finally, this data support CBT in many high-risk or urgent pts even if a well-matched CB graft cannot be identified. This is especially true in younger pts or those with a low 0-3 aaHCT-CI who had high 2-yr PFS. [Display omitted] DisclosuresPerales:Incyte: Membership on an entity's Board of Directors or advisory committees, Other: Personal fees and Clinical trial support; Novartis: Other: Personal fees; Abbvie: Other: Personal fees; Merck: Other: Personal fees; Takeda: Other: Personal fees. Sauter:Juno Therapeutics: Consultancy, Research Funding; Sanofi-Genzyme: Consultancy, Research Funding; Spectrum Pharmaceuticals: Consultancy; Novartis: Consultancy; Precision Biosciences: Consultancy; Kite: Consultancy. Shah:Janssen: Research Funding; Amgen: Research Funding.

Double-Unit Cord Blood (CB) Transplantation with Haplo-Identical CD34+ Cells (haplo-dCBT) May Speed Neutrophil Recovery Although Successful Bridging Is Contingent on Close Haplo-Winning CB Unit HLA-Match

Background: While dCBT is associated with high rates of sustained donor engraftment, delayed neutrophil recovery in adults is frequent and can contribute to extended hospitalization and early transplant-related mortality.Methods: We investigated engraftment after myeloablative dCBT supplemented with CD34+ selected haploidentical PBSC (haploCD34+) in patients (pts) with high risk hematologic malignancies or aplastic anemia in a phase II clinical trial. The aim was to abrogate neutropenia (ANC >/= 500 within 14 days) with a haplo myeloid bridge prior to CB engraftment. Pts did not receive ATG due to the increased mortality risk reported in adult CBT. Double unit CB grafts allowed comparison to dCBT controls without haploidentical graft supplementation.Results: 78 adult pts [median age 48.5 years (range 21-68), median weight 82 kgs (range 48-138), 44 (56%) CMV+, 3 with prior allografts] underwent haplo-dCBT between 9/2012-12/2017. Diagnoses included 54 (69%) acute leukemias, 10 (13%) MDS/ MPN (all ≤ 10% blasts at work-up), 10 (17%) NHL/ HD and 1 aplastic anemia. Conditioning was myeloablative (1 Cy 120/ Flu 75/ TBI 1375, 77 intermediate intensity Cy 50/ Flu 150/ Thio 5-10/ TBI 400) with CSA/ MMF. CB units had a median infused TNC of 2.3 (range 1-5.7) x 107/kg/unit & median infused viable CD34+ cell dose of 1.1 (range 0.1-3.1) x 105/kg/unit with a median 5/8 (range 2-7) unit-recipient HLA-allele match. Haplo CD34+ grafts [procured from children (46%), siblings (31%), parents (13%) or extended family (10%)] had a median infused CD34+ dose of 5.2 x 106/kg (range 1.1-16.8) and a median infused CD3+ dose of 1.6 x 103/kg (range 0.3-13.7). Sixty-one (78%) haplos were 4/8 and 17 (22%) were 5-7/8 HLA-matched to the pt. In 77 evaluable pts (1 pt died on day 14), 4 engraftment patterns were observed (Table 1). All but 2 pts had sustained CB engraftment with either an optimal haplo-bridge (Gp. 1, 34/77, 44%), a transient bridge with a second nadir preceding CB engraftment (Gp. 2, 20/77, 26%), or no bridge (Gp. 3, 21/77, 27%). The 2 remaining pts had CB/ haplo graft failure (Gp. 4, 2/77, 3%); both were successfully re-transplanted with single CB units. While there was no difference in the day 100 TRM in the 34 optimal bridge pts vs pts with transient or no bridge [9% (95%CI 2-21) vs 15% (95%CI 6-27), p = 0.388], optimal bridge pts had faster platelet recovery [19 (range 14-41) vs 44.5 days (range 14-67)] and earlier hospital discharge [28.5 (range 20-60) vs 36 days (range 28-98)]. Similar to dCBT alone, chimerism analysis revealed sustained engraftment in haplo-dCBT is mediated by a “winning” CB unit. This was heralded by winning unit-derived T-cells seen as early as day +28. Although universal, the speed of haplo rejection varied, and a high haplo chimerism percentage early post-transplant did not guarantee successful bridging. Analysis of factors potentially predicting an optimal bridge is shown in Table 2. The median winning CB unit-haplo 8-allele HLA-match was 3/8 (range 1-7/8). In univariate analysis, higher haplo CD34+ dose/kg, > 4/8 haplo-recipient HLA-match and ≥ 3/8 winning unit-haplo HLA-match were associated with a higher likelihood of bridging. Haplo CD34+ dose and winning unit-haplo HLA-match remained significant in multivariate analysis.Conclusions: While haplo-dCBT can be associated with enhanced neutrophil recovery, this platform does not guarantee a successful myeloid bridge due to early haplo rejection by the winning CB unit. This universal haplo rejection highlights the importance of the CB graft dose and quality with this ATG-free strategy as the CB will mediate sustained engraftment. Our findings have significance for strategies that combine unmanipulated CB with any third-party or ex vivo expanded T-cell depleted product given higher product CD34+ cell dose and better HLA-match to the unmanipulated CB unit could improve the likelihood of successful myeloid bridging. The data also support alternative approaches to improve myeloid recovery after CBT such as optimized unit selection and vivo expansion. [Display omitted] DisclosuresO'Reilly:Atara Biotherapeutics: Consultancy, Patents & Royalties, Research Funding. Perales:Takeda: Other: Personal fees; Novartis: Other: Personal fees; Incyte: Membership on an entity's Board of Directors or advisory committees, Other: Personal fees and Clinical trial support; Merck: Other: Personal fees; Abbvie: Other: Personal fees. Sauter:Juno Therapeutics: Consultancy, Research Funding; Sanofi-Genzyme: Consultancy, Research Funding; Spectrum Pharmaceuticals: Consultancy; Novartis: Consultancy; Precision Biosciences: Consultancy; Kite: Consultancy. Shah:Janssen: Research Funding; Amgen: Research Funding.

P071 Limited exon sequence mismatches outside the antigen recognition domain in a cohort of 4646 high resolution 10/10 HLA-matched donor and recipient

Aim In hematopoietic stem cell transplantation (HCT), HLA allele matching between donor and recipient has traditionally focused on the polymorphic antigen recognition domain (ARD). Mismatching at the ARD is known to influence outcomes. This study investigated the genetic differences in the non-ARD regions among ARD-matched donor-recipient pairs to determine possible association with the transplant outcomes. Methods We compared the full-length HLA Class I allele sequences (HLA-A, -B, -C) and partial-length (partial intron 1 through partial intron 3) Class II allele sequences (HLA-DRB1, DQB1) for 4646 high-resolution 10/10 HLA-matched HCT donor-recipient pairs. We developed a comprehensive HLA allele sequence comparison pipeline, which identifies and annotates the mismatched positions between two alleles by their functional region and their protein sequence differences using IMGT/HLA Database (v3.31.0). Results For HLA Class I alleles, 95.4% of the ARD matched alleles have identical sequences outside the ARD, including introns and non-ARD exons. 0.3% of the mismatches were synonymous variants from the ARD region while 0.2% and 0.1% of mismatches found from non-ARD exons were synonymous and nonsynonymous variants, respectively. The intronic variation accounted for 4.2% of the mismatches. Similarly, for HLA Class II alleles, 0.3% of mismatches were synonymous ARD variants, and the mismatches in the non-ARD exons were also very rare (synonymous: 0.3%; nonsynonymous: 0.2%). However, a high degree of polymorphism was observed in the intronic regions of the Class II genes with only 77.3% of the allele pairs having identical sequences. 0.2% and 4.6% of Class I and Class II allele pairs, respectively, showed both exonic and intronic mismatches. Conclusions HCT donor/recipient pairs matched at high resolution for HLA-A, B, C, DRB1 and DQB1 have limited coding variation outside of the ARD. Intronic variation was observed at a higher rate for HLA Class II in our study compared to prior publications (17.3% vs.

SV-BR-1-GM, a Clinically Effective GM-CSF-Secreting Breast Cancer Cell Line, Expresses an Immune Signature and Directly Activates CD4+ T Lymphocytes.

Targeted cancer immunotherapy with irradiated, granulocyte–macrophage colony-stimulating factor (GM-CSF)-secreting, allogeneic cancer cell lines has been an effective approach to reduce tumor burden in several patients. It is generally assumed that to be effective, these cell lines need to express immunogenic antigens coexpressed in patient tumor cells, and antigen-presenting cells need to take up such antigens then present them to patient T cells. We have previously reported that, in a phase I pilot study (ClinicalTrials.gov NCT00095862), a subject with stage IV breast cancer experienced substantial regression of breast, lung, and brain lesions following inoculation with clinical formulations of SV-BR-1-GM, a GM-CSF-secreting breast tumor cell line. To identify diagnostic features permitting the prospective identification of patients likely to benefit from SV-BR-1-GM, we conducted a molecular analysis of the SV-BR-1-GM cell line and of patient-derived blood, as well as a tumor specimen. Compared to normal human breast cells, SV-BR-1-GM cells overexpress genes encoding tumor-associated antigens (TAAs) such as PRAME, a cancer/testis antigen. Curiously, despite its presumptive breast epithelial origin, the cell line expresses major histocompatibility complex (MHC) class II genes (HLA-DRA, HLA-DRB3, HLA-DMA, HLA-DMB), in addition to several other factors known to play immunostimulatory roles. These factors include MHC class I components (B2M, HLA-A, HLA-B), ADA (encoding adenosine deaminase), ADGRE5 (CD97), CD58 (LFA3), CD74 (encoding invariant chain and CLIP), CD83, CXCL8 (IL8), CXCL16, HLA-F, IL6, IL18, and KITLG. Moreover, both SV-BR-1-GM cells and the responding study subject carried an HLA-DRB3*02:02 allele, raising the question of whether SV-BR-1-GM cells can directly present endogenous antigens to T cells, thereby inducing a tumor-directed immune response. In support of this, SV-BR-1-GM cells (which also carry the HLA-DRB3*01:01 allele) treated with yellow fever virus (YFV) envelope (Env) 43–59 peptides reactivated YFV-DRB3*01:01-specific CD4+ T cells. Thus, the partial HLA allele match between SV-BR-1-GM and the clinical responder might have enabled patient T lymphocytes to directly recognize SV-BR-1-GM TAAs as presented on SV-BR-1-GM MHCs. Taken together, our findings are consistent with a potentially unique mechanism of action by which SV-BR-1-GM cells can act as APCs for previously primed CD4+ T cells.

European Group for Blood and Marrow Transplantation Risk Score Predicts the Outcome of Patients with Acute Leukemia Receiving Single Umbilical Cord Blood Transplantation

The European Group for Blood and Marrow Transplantation (EBMT) risk score has been implemented as an important tool to predict patient outcomes after allogeneic hematopoietic stem cell transplantation. However, to our knowledge, this score has never been applied in cases of single umbilical cord blood transplantation (sUCBT). We retrospectively analyzed 207 consecutive patients with acute leukemia who received sUCBT at our center between February 2011 and December 2015. The probabilities of 3-year overall survival (OS) and leukemia-free survival (LFS) of the entire cohort were 65.0% and 59.8%, respectively, whereas the cumulative incidences of 3-year nonrelapse mortality (NRM) and relapse rate were 19.5% and 20.3%, respectively. In the univariate analysis, a higher EBMT risk score was associated with worse OS and LFS and higher NRM and relapse rate, ranging from 81.7%, 75.9%, 7.3%, and 15.3%, respectively, for patients with a score of 1 to 43.8%, 44.3%, 31.7%, and 23.9%, respectively, for patients with scores of 4 to 6. Hazard ratios of OS, LFS, and NRM all steadily increased for each additional score point. Importantly, the prognostic value of the EBMT risk score on OS, LFS, NRM, and relapse was maintained in the multivariate analysis. Moreover, considering the univariate analysis results of donor–recipient gender and mismatched allele-level HLA-A, -B, -C, and -DRB1 loci on patient outcomes and the fairly strong interaction between time from diagnosis to sUCBT and disease status, we developed a modified sUCBT-EBMT risk score by using degrees of 8-allele HLA match instead of donor type, donor–recipient gender combination, and time from diagnosis to sUCBT, and found that the modified score could also be used as a predictor for patient outcomes after sUCBT. The EBMT risk score is a good predictor of outcomes of patients with leukemia after sUCBT. The modified sUCBT-EBMT risk score can also be used as a pretransplant risk assessment, but this metric still requires further evaluation with a larger cohort.