Abstract: Toxicities have limited the use of allogeneic hematopoietic cell transplantation (HCT) to younger, medically fit patients. In a canine HCT model, a combination of postgrafting mycophenolate mofetil (MMF) and cyclosporine (CSP) allowed stable allogeneic engraftment after minimally toxic conditioning with low-dose (200 cGy) total-body irradiation (TBI). These findings, together with the known antitumor effects of donor leukocyte infusions (DLIs), led to the design of this trial. Forty-five patients (median age 56 years) with hematologic malignancies, HLA-identical sibling donors, and relative contraindications to conventional HCT were treated. Immunosuppression involved TBI of 200 cGy before and CSP/MMF after HCT. DLIs were given after HCT for persistent malignancy, mixed chimerism, or both. Regimen toxicities and myelosuppression were mild, allowing 53% of eligible patients to have entirely outpatient transplantations. Nonfatal graft rejection occurred in 20% of patients. Grades II to III acute graft-versus-host disease (GVHD) occurred in 47% of patients with sustained engraftment. With median follow-up of 417 days, survival was 66.7%, nonrelapse mortality 6.7%, and relapse mortality 26.7%. Fifty-three percent of patients with sustained engraftment were in complete remission, including 8 with molecular remissions. This novel allografting approach, based on the use of postgrafting immunosuppression to control graft rejection and GVHD, has dramatically reduced the acute toxicities of allografting. HCT with the induction of potent graft-versus-tumor effects can be performed in previously ineligible patients, largely in an outpatient setting. Future protocol modifications should reduce rejection and GVHD, thereby facilitating studies of allogeneic immunotherapy for a variety of malignancies.

Abstract: Stable mixed chimerism can be established in dogs given a sublethal dose of 200 cGy total body irradiation (TBI) before and immunosuppression with mycophenolate mofetil (MMF) and cyclosporine (CSP) for 28 and 35 days, respectively, after dog leukocyte antigen-identical marrow transplantation. Most likely, the role of pretransplant TBI was to provide host immunosuppression, since stable mixed chimerism was also achieved in MMF/CSP-treated dogs when 450 cGy irradiation, targeted to cervical, thoracic, and upper abdominal lymph nodes, was substituted for TBI. When TBI was reduced from 200 to 100 cGy, all grafts were rejected within 3 to 12 weeks. Here, we asked whether stable engraftment after 100 cGy TBI could be accomplished by first reducing the intensity of host immune responsiveness with help of the fusion peptide CTLA4Ig, which blocks T-cell costimulation through the B7-CD28 signal pathway. Accordingly, recipient T cells were activated with intravenous (IV) injections of 106 donor peripheral blood mononuclear cells (PBMC)/kg per day on days −7 to −1 before 100 cGy TBI, with concurrent administration of CTLA4Ig 4 mg/kg/d IV. All 7 dogs so treated showed initial mixed chimerism. Two rejected their allografts after 8 and 20 weeks, respectively, and survived with autologous marrow recovery; 1 mixed chimera was unevaluable because of death at 3 weeks from intussusception; and 4 showed persisting mixed chimerism, including unirradiated marrow and lymph node spaces, for now more than 46 to 70 weeks after transplant. Data support the hypothesis that stable marrow allografts can be established by combining nonmyeloablative pretransplant host immunosuppression with posttransplant host and donor cell immunosuppression using MMF/CSP.

Abstract: Background: T cells can be activated and expanded ex vivo using the Xcellerate™ Process, in which peripheral blood mononuclear cells (PBMC) are incubated with anti-CD3 and anti-CD28 antibody-coated magnetic beads (Xcyte™-Dynabeads®). In an ongoing trial of Xcellerated T Cells in subjects with chronic lymphocytic leukemia, marked and sustained reductions in lymphadenopathy and splenomegaly were observed (Wierda et al., ASCO 2004). Increases in neutrophil, platelet and NK cell counts were also documented. This study is designed to determine if similar effects can be observed in subjects with indolent non-Hodgkin’s lymphoma (NHL). Methods: Subjects must have indolent NHL (follicular, small lymphocytic, marginal zone, or mantle cell lymphoma), have relapsed or refractory disease, and have received at least 1 but not more than 4 prior treatment regimens. PBMC are collected by leukapheresis for the Xcellerate Process, and subjects subsequently receive two infusions of 20–60 x 109 Xcellerated T Cells separated by 6–8 weeks. Approximately 40 subjects will be treated. Results: Seven subjects have been enrolled and Xcellerated T Cells have been manufactured in 5 subjects to date. T cells expanded 181.8 ± 88.5 fold and the final product was & gt;99.0 ± 0.0% T cells (mean + SD). One subject with small lymphocytic lymphoma has been treated with two infusions of 38.6 x 109 Xcellerated T Cells. There have been no serious adverse events to date. Following the first treatment, the lymphocyte count increased from 1.8 x 109/L to 2.9 x 109/L on Day 28. The neutrophil count also increased from 2.9 x 109/L to 5.5 x 109/L six weeks following infusion. The subject had a significant reduction in cervical lymphadenopathy and a slight decrease in bulky mesenteric lymphadenopathy six weeks following the first infusion. Conclusions: Xcellerated T Cells can be manufactured in subjects with indolent NHL. Treatment leads to significant increases in T cell and neutrophil counts. Preliminary data suggest a reduction in peripheral lymphadenopathy. Data on additional subjects will be presented.

Abstract: Stable mixed donor/host hematopoietic chimerism can be accomplished in dog leukocyte antigen (DLA)-identical littermate dogs given sublethal (200 cGy) total-body irradiation (TBI) before and immunosuppression with mycophenolate mofetil (MMF) and cyclosporine (CSP) after transplant (Blood 89:3048, 1997). Studies were based on the hypothesis that drugs that prevent graft-versus-host disease (GVHD) after transplant also suppress host-versus-graft (HVG) reactions and thereby enhance engraftment. Here, we asked whether pretransplant TBI provided marrow space for the graft to home or caused host immunosuppression. To address the questions, recipients were given pretransplant irradiation to cervical, thoracic, and abdominal lymph nodes (except pelvis), DLA-identical littermate marrow grafts, and MMF/CSP posttransplant. Six dogs that received 450 cGy irradiation showed initial engraftment. Two rejected their grafts after 8 and 18 weeks, 1 died with GVHD and engraftment, and 3 are alive as mixed chimeras after 57 to 97 weeks. Four dogs given 200 cGy irradiation also showed initial engraftment, but rejected their grafts after 10 to 18 weeks. Mixed chimerism was present in nonirradiated marrow and lymph node spaces and involved granulocytes, T cells, and monocytes. While other explanations are possible, results seem consistent with the hypothesis that pretransplant radiation provides host immunosuppression, and grafts can create their own marrow space. These data set the stage for the development of novel transplant regimens that substitute immunosuppressive for cytotoxic agents.

Abstract: A competitive repopulation assay in the dog was used to develop improved gene transfer protocols for hematopoietic stem cell gene therapy. Using this assay, we previously showed improved gene transfer into canine hematopoietic repopulating cells when CD34-enriched marrow cells were cocultivated on gibbon ape leukemia virus (GALV)–based retrovirus vector-producing cells. In the present study, we have investigated the use of fibronectin fragment CH-296 and 2 growth factor combinations to further improve gene transfer efficiency. CD34-enriched marrow cells from each dog were prestimulated for 24 hours and then divided into 3 equal fractions. Two fractions were placed into flasks coated with either CH-296 or bovine serum albumin (BSA) and virus-containing medium supplemented with growth factors, and protamine sulfate was replaced 4 times over a 48-hour period. One fraction was cocultivated on irradiated PG13 (GALV-pseudotype) packaging cells for 48 hours. In 2 animals, cells of the different fractions were transduced in the presence of human FLT-3 ligand (FLT3L), canine stem cell factor (cSCF), and human megakaryocyte growth and development factor (MGDF), and in 2 other dogs, transduction was performed in the presence of FLT3L, cSCF, and canine granulocyte-colony stimulating factor (cG-CSF). The vectors used contained small sequence differences, allowing differentiation of cells genetically marked by the different vectors. After transduction, nonadherent and adherent cells from all 3 fractions were pooled and infused into lethally irradiated dogs. Polymerase chain reaction and Southern blot analysis were used to determine the persistence of the transferred vectors in the peripheral blood and marrow cells after transplantation. The highest levels of gene transfer were obtained when cells were transduced in the presence of FLT3L, cSCF, and cG-CSF (gene transfer levels of more than 10% for more than 8 months so far). Compared with the 2 animals that received cells transduced with FLT3L, cSCF, and MGDF, gene transfer levels were significantly higher when dogs received cells that were transduced in the presence of cG-CSF. Transduction on CH-296 resulted in gene transfer levels that were at least as high as transduction by cocultivation. In summary, the overall levels of gene transfer obtained with these conditions should be sufficiently high to allow stem cell gene therapy studies aimed at correcting genetic diseases in dogs as a model for human gene therapy.

Abstract: Background: Standard of care (SOC) for second-line (2L) therapy (tx) of relapsed/refractory aggressive B-cell non-Hodgkin lymphomas (R/R aNHL) includes platinum-based chemotherapy (PCT) followed by autologous hematopoietic cell transplantation (aHCT) in responders. Outcomes are poor for patients (pts) with R/R aNHL who experience progression during or within 12 months (mo) of 1L tx. Tisagenlecleucel (tisa-cel) is an autologous chimeric antigen receptor (CAR) T-cell tx targeting CD19 approved for pts with large B-cell lymphoma (LBCL; US) and diffuse LBCL (non-US) after ≥2 lines of tx. BELINDA (NCT03570892) is a Phase III, randomized, global (18 countries) study of tisa-cel vs SOC as 2L tx for R/R aNHL. Methods: Adults with confirmed R/R aNHL within 12 mo after 1L chemo-immunotherapy were eligible. All pts underwent leukapheresis for tisa-cel production and were randomized 1:1 to receive tisa-cel (Arm A) or SOC (Arm B) and stratified by 1L duration of response, International Prognostic Index (IPI), and geographic region. Arm A received optional bridging tx (investigator choice of protocol-defined PCT regimens) followed by lymphodepletion (LD; generally, fludarabine 25 mg/m 2/day [d] + cyclophosphamide 250 mg/m 2/d for 3 d) and followed by a single tisa-cel infusion (0.6-6×10 8 CAR-T cells). Arm B received investigator choice of PCT regimen followed by aHCT in responders or a second PCT in nonresponders. Disease assessments were performed at 6 and 12 weeks (wk), then planned every 3 mo for year (y) 1 and every 6 mo for y 2. The primary endpoint was event-free survival (EFS), defined as time from randomization to stable disease (SD) or progressive disease (PD) at or after wk 12 assessment or death at any time. SD/PD at wk 6 was not considered an event on either Arm. Arm A's wk 6 assessment evaluated disease burden before tisa-cel infusion and after bridging if administered. Arm B's wk 6 assessment determined if response was sufficient for aHCT or if a second PCT regimen was needed prior to aHCT. Results: As of May 6, 2021, 322 pts were randomized: 162 to Arm A and 160 to Arm B. In Arms A and B, 33% and 29% were ≥65 y, and 66% and 67% had primary refractory disease, respectively. Baseline characteristics indicated imbalances with more high-grade B-cell lymphomas (24% vs 17%) and IPI ≥2 (65% vs 58%) in Arm A vs B. In Arm A, 47% received ≥2 cycles of bridging PCT, 36% received 1 cycle, and 17% received 0. In Arm A, 96% received tisa-cel; the median dose was 2.9×10 8 cells. In Arm B, 96% received ≥2 PCT cycles and 54% received ≥2 different PCT regimens; 33% received aHCT, including 10% requiring ≥2 different PCT regimens before aHCT. Median time from randomization to aHCT was 92 d (range, 61-158 d). Median follow-up was 10 mo (range, 2.9-23.2 mo). At wk 6 assessment, 26% had PD in Arm A vs 14% in Arm B. Median EFS in Arms A and B was 3 mo (HR 1.07; 95% CI, 0.82-1.40; P=0.69); Arm A pts with PD at wk 6 had shorter EFS. Overall response rate (ORR) at wk 12 in Arm A was 46% vs 43% in Arm B; complete response rate in both arms was 28%. Some pts responded to tisa-cel after SD/PD at wk 12 without additional tx but were counted as an event in EFS analysis. In Arm B, 81 pts (51%) crossed over to receive tisa-cel, 71 without receiving aHCT. Of 72 crossover pts with response assessment, ORR to tisa-cel was 40%. Overall survival was immature at data cutoff. In Arm A, 84% had a grade ≥3 adverse event (AE; vs 90% in Arm B), including grade ≥3 cytokine release syndrome in 5% (CRS; Lee 2014) and grade ≥3 neurologic events (NE) in 3% (CTCAE v5.0), with no grade 5 CRS/NE. Median times to CRS and NE onset were 4 and 5 d, respectively; median time to resolution was 5 and 9 d. Fifty-two (32%) and 45 (28%) pts in Arms A and B died on study, including 42 (26%) and 32 (20%) deaths due to PD, respectively. Ten pts in Arm A and 13 in Arm B died of AEs. Conclusions: Tisa-cel as 2L tx in R/R aNHL pts did not have a higher EFS vs SOC. Possible contributing factors include study design elements, such as optional PCT bridging tx in Arm A with potential delay of tisa-cel infusion until after wk 6 assessment, allowance of a different PCT regimen to reach aHCT in Arm B after inadequate response to first PCT, and imbalances in relevant pt characteristics. Insights from this randomized Phase III study will inform use of cellular tx in the 2L R/R aNHL setting and the design of future CAR-T trials. Figure 1 Figure 1. Disclosures Bishop: Arcellx, Autolus, Bristol-Myers Squibb, CRISPR, Kite/Gilead, and Novartis: Consultancy, Research Funding; Bristol-Myers Squibb and Kite/Gilead: Other: fees for non-CME/CE services . Dickinson: Novartis: Consultancy, Honoraria, Research Funding, Speakers Bureau; Roche: Consultancy, Honoraria, Other: travel, accommodation, expenses, Research Funding, Speakers Bureau; Gilead Sciences: Consultancy, Honoraria, Speakers Bureau; MSD: Consultancy, Honoraria, Research Funding, Speakers Bureau; Janssen: Consultancy, Honoraria; Bristol-Myers Squibb: Consultancy, Honoraria; Takeda: Research Funding; Celgene: Research Funding; Amgen: Honoraria. Purtill: Novartis: Honoraria; Gilead: Honoraria; BMS Celgene: Honoraria. Barba: Amgen, Celgene, Gilead, Incyte, Jazz Pharmaceuticals, MSD, Novartis, Pfizer and Roche, Jazz Phar,aceuticals: Honoraria; Cqrlos III heqlth Institute, aSOCIACION espanola contra el cancer, PERIS: Research Funding. Santoro: Arqule: Consultancy, Speakers Bureau; Sanofi: Consultancy; Takeda: Speakers Bureau; BMS: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Roche: Speakers Bureau; AbbVie: Speakers Bureau; Amgen: Speakers Bureau; Celgene: Speakers Bureau; Servier: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Gilead: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; AstraZeneca: Speakers Bureau; Pfizer: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Eli-Lilly: Speakers Bureau; Sandoz: Speakers Bureau; Eisai: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Novartis: Speakers Bureau; Bayer: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; MSD: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Hamad: Novartis: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Kato: Abbvie: Consultancy, Research Funding; AstraZeneca: Consultancy; Bristol-Myers Squibb: Honoraria, Research Funding; Celgene: Consultancy, Honoraria, Research Funding; Chugai: Consultancy, Honoraria, Research Funding; Daiichi Sankyo: Consultancy, Research Funding; Dainippon-Sumitomo: Honoraria; Eisai: Consultancy, Research Funding; Janssen: Consultancy, Honoraria, Research Funding; Kyowa Kirin: Honoraria, Research Funding; MSD: Honoraria; Mundi: Honoraria; Novartis: Consultancy, Research Funding; Ono: Honoraria, Research Funding. Sureda: Takeda: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Support for attending meetings and/or travel, Research Funding, Speakers Bureau; BMS/Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Support for attending meetings and/or travel, Speakers Bureau; MSD: Consultancy, Honoraria, Speakers Bureau; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Kite, a Gilead Company: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Amgen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Sanofi: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; GSK: Consultancy, Honoraria, Speakers Bureau; Roche: Other: Support for attending meetings and/or travel; Bluebird: Membership on an entity's Board of Directors or advisory committees; Mundipharma: Consultancy. Greil: Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Accommodations, Expenses, Research Funding; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Accommodations, Expenses, Research Funding; F. Hoffmann-La Roche Ltd: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Accommodations, Expenses, Research Funding; Bristol-Myers Squibb: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Accommodations, Expenses, Research Funding; Takeda: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; AbbVie: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Accommodations, Expenses, Research Funding; AstraZeneca: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Accommodations, Expenses, Research Funding; Janssen: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Accommodations, Expenses; Merck Sharp & Dohme: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Accommodations, Expenses, Research Funding; Gilead: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Accommodations, Expenses, Research Funding; Daiichi Sankyo: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Accommodations, Expenses, Research Funding; Sankyo: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Accommodations, Expenses, Research Funding; Sanofi: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Amgen: Honoraria, Other: Travel, Accommodations, Expenses, Research Funding; Sandoz: Honoraria, Research Funding. Thieblemont: Gilead Sciences: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Accommodations, Expenses ; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Accommodations, Expenses ; Bristol Myers Squibb/Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Accommodations, Expenses ; Roche: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Accommodations, Expenses , Research Funding; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees; Kyte: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Accommodations, Expenses ; Incyte: Honoraria, Membership on an entity's Board of Directors or advisory committees; Abbvie: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Accommodations, Expenses ; Cellectis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Accommodations, Expenses ; Hospira: Research Funding; Bayer: Honoraria; Amgen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Accommodations, Expenses . Morschhauser: F. Hoffmann-La Roche Ltd: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Celgene: Membership on an entity's Board of Directors or advisory committees; Bristol-Myers Squibb: Consultancy, Membership on an entity's Board of Directors or advisory committees; Epizyme: Consultancy, Membership on an entity's Board of Directors or advisory committees; Gilead: Consultancy, Membership on an entity's Board of Directors or advisory committees; Chugai: Honoraria; Janssen: Honoraria; Genmab: Membership on an entity's Board of Directors or advisory committees; AbbVie: Consultancy, Membership on an entity's Board of Directors or advisory committees; Genentech, Inc.: Consultancy; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees; AstraZenenca: Membership on an entity's Board of Directors or advisory committees; Servier: Consultancy; Incyte: Membership on an entity's Board of Directors or advisory committees. Janz: Janssen: Honoraria, Other: Meeting Fees; Novartis: Honoraria; Takeda: Honoraria, Other: Travel Accommodations, Expenses, Meeting fees; Roche: Honoraria; Gilead: Other: Travel Accommodations, Expenses, Meeting fees. Flinn: Servier Pharmaceuticals: Consultancy, Other: All consultancy payments made to Sarah Cannon Research Institute; Yingli Pharmaceuticals: Consultancy, Other: All consultancy payments made to Sarah Cannon Research Institute; Seagen: Consultancy, Other: All consultancy payments made to Sarah Cannon Research Institute; Servier Pharmaceuticals: Consultancy, Other: All consultancy payments made to Sarah Cannon Research Institute; Unum Therapeutics: Consultancy, Other: All consultancy payments made to Sarah Cannon Research Institute, Research Funding; Johnson & Johnson: Current equity holder in publicly-traded company; Seattle Genetics: Research Funding; Sarah Cannon Research Institute: Current Employment; Vincerx Pharma: Consultancy, Other: All consultancy payments made to Sarah Cannon Research Institute; Hutchison MediPharma: Consultancy, Other: All consultancy payments made to Sarah Cannon Research Institute; Century Therapeutics: Consultancy, Other: All consultancy payments made to Sarah Cannon Research Institute; Triphase Research & Development Corp.: Other: All research funding payments made to Sarah Cannon Research Institute, Research Funding; Trillium Therapeutics: Other: All research funding payments made to Sarah Cannon Research Institute, Research Funding; Teva: Other: All research funding payments made to Sarah Cannon Research Institute, Research Funding; Rhizen Pharmaceuticals: Other: All research funding payments made to Sarah Cannon Research Institute, Research Funding; Portola Pharmaceuticals: Other: All research funding payments made to Sarah Cannon Research Institute, Research Funding; Pfizer: Other: All research funding payments made to Sarah Cannon Research Institute, Research Funding; Novartis: Consultancy, Other: All consultancy and research funding payments made to Sarah Cannon Research Institute, Research Funding; Merck: Other: All research funding payments made to Sarah Cannon Research Institute, Research Funding; Loxo: Other: All research funding payments made to Sarah Cannon Research Institute, Research Funding; Karyopharm Therapeutics: Other: All research funding payments made to Sarah Cannon Research Institute, Research Funding; Infinity Pharmaceuticals: Other: All research funding payments made to Sarah Cannon Research Institute, Research Funding; Incyte: Other: All research funding payments made to Sarah Cannon Research Institute, Research Funding; IGM Biosciences: Other: All research funding payments made to Sarah Cannon Research Institute, Research Funding; Forty Seven: Other: All research funding payments made to Sarah Cannon Research Institute, Research Funding; Forma Therapeutics: Other: All research funding payments made to Sarah Cannon Research Institute, Research Funding; Curis: Other: All research funding payments made to Sarah Cannon Research Institute, Research Funding; Constellation Pharmaceuticals: Other: All research funding payments made to Sarah Cannon Research Institute, Research Funding; Celgene: Other: All research funding payments made to Sarah Cannon Research Institute, Research Funding; Calithera Biosciences: Other: All research funding payments made to Sarah Cannon Research Institute, Research Funding; ArQule: Other: All research funding payments made to Sarah Cannon Research Institute, Research Funding; Agios: Other: All research funding payments made to Sarah Cannon Research Institute, Research Funding; Acerta Pharma: Other: All research funding payments made to Sarah Cannon Research Institute, Research Funding; Yingli Pharmaceuticals: Consultancy, Other: All consultancy payments made to Sarah Cannon Research Institute; Verastem: Consultancy, Other: All consultancy and research funding payments made to Sarah Cannon Research Institute, Research Funding; Unum Therapeutics: Consultancy, Other: All consultancy and research funding payments made to Sarah Cannon Research Institute, Research Funding; TG Therapeutics: Consultancy, Other: All consultancy and research funding payments made to Sarah Cannon Research Institute, Research Funding; Takeda: Consultancy, Other: All consultancy and research funding payments made to Sarah Cannon Research Institute, Research Funding; Seagen: Consultancy, Other: All consultancy and research funding payments made to Sarah Cannon Research Institute, Research Funding; Roche: Consultancy, Other: All consultancy and research funding payments made to Sarah Cannon Research Institute, Research Funding; Pharmacyclics LLC, an AbbVie Company: Consultancy, Other: All consultancy and research funding payments made to Sarah Cannon Research Institute, Research Funding; Nurix Therapeutics: Consultancy, Other: All consultancy payments made to Sarah Cannon Research Institute; MorphoSys: Consultancy, Other: All consultancy and research funding payments made to Sarah Cannon Research Institute, Research Funding; Kite, a Gilead Company: Consultancy, Other: All consultancy and research funding payments made to Sarah Cannon Research Institute, Research Funding; Juno Therapeutics: Consultancy, Other: All consultancy and research funding payments made to Sarah Cannon Research Institute, Research Funding; Janssen: Consultancy, Other: All consultancy and research funding payments made to Sarah Cannon Research Institute, Research Funding; Iksuda Therapeutics: Consultancy, Other: All consultancy payments made to Sarah Cannon Research Institute; Great Point Partners: Consultancy, Other: All consultancy payments made to Sarah Cannon Research Institute; Gilead Sciences: Consultancy, Other: All consultancy and research funding payments made to Sarah Cannon Research Institute, Research Funding; Genentech: Consultancy, Other: All consultancy and research funding payments made to Sarah Cannon Research Institute, Research Funding; BeiGene: Consultancy, Other: All consultancy and research funding payments made to Sarah Cannon Research Institute, Research Funding; AstraZeneca: Consultancy, Other: All consultancy and research funding payments made to Sarah Cannon Research Institute, Research Funding; AbbVie: Consultancy, Other: All Consultancy and Research Funding payments made to Sarah Cannon Research Institute, Research Funding. Kwong: Novartis: Consultancy, Honoraria, Research Funding. Kersten: Novartis: Consultancy, Honoraria, Other: Travel support; Takeda: Research Funding; Kite, a Gilead Company: Consultancy, Honoraria, Other: Travel support, Research Funding; Celgene: Research Funding; Roche: Consultancy, Honoraria, Other: Travel support, Research Funding; Miltenyi Biotec: Consultancy, Honoraria, Other: Travel support; BMS/Celgene: Consultancy, Honoraria. Minnema: Janssen: Consultancy, Honoraria; Celgene: Other: Travel expenses; BMS: Consultancy; Kite/Gilead: Consultancy; Alnylam: Consultancy. Holte: Roche: Membership on an entity's Board of Directors or advisory committees; Takeda: Membership on an entity's Board of Directors or advisory committees; Nanovector: Membership on an entity's Board of Directors or advisory committees, Other: lectures honorarias; Novartis: Membership on an entity's Board of Directors or advisory committees; Gilead: Membership on an entity's Board of Directors or advisory committees; Nordic: Membership on an entity's Board of Directors or advisory committees. Martinez-Lopez: Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees; Bristol Myers Squibb: Honoraria, Membership on an entity's Board of Directors or advisory committees; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Sanofi: Honoraria, Membership on an entity's Board of Directors or advisory committees; GSK: Honoraria, Membership on an entity's Board of Directors or advisory committees; Incyte: Honoraria, Membership on an entity's Board of Directors or advisory committees; Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees; Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees; Adaptive Biotechnologies: Honoraria, Membership on an entity's Board of Directors or advisory committees. Maziarz: Novartis: Consultancy, Other: Data and Safety Monitoring board, Research Funding; Incyte Corporation: Consultancy, Honoraria; Bristol-Myers, Squibb/Celgene,, Intellia, Kite: Honoraria; Allovir: Consultancy, Research Funding; Artiva Therapeutics: Consultancy; CRISPR Therapeutics: Consultancy; Intellia: Honoraria; Omeros: Research Funding; Athersys: Other: Data and Safety Monitoring Board, Patents & Royalties; Vor Pharma: Other: Data and Safety Monitoring Board. McGuirk: Kite/ Gilead: Consultancy, Honoraria, Other: travel accommodations, expense, Kite a Gilead company, Research Funding, Speakers Bureau; Juno Therapeutics: Consultancy, Honoraria, Research Funding; Allovir: Consultancy, Honoraria, Research Funding; Magenta Therapeutics: Consultancy, Honoraria, Research Funding; EcoR1 Capital: Consultancy; Novartis: Research Funding; Fresenius Biotech: Research Funding; Astelllas Pharma: Research Funding; Bellicum Pharmaceuticals: Research Funding; Novartis: Research Funding; Gamida Cell: Research Funding; Pluristem Therapeutics: Research Funding. Bachy: Kite, a Gilead Company: Honoraria; Novartis: Honoraria; Daiishi: Research Funding; Roche: Consultancy; Takeda: Consultancy; Incyte: Consultancy. Dreyling: Amgen: Speakers Bureau; Astra Zeneca: Consultancy, Speakers Bureau; Bayer: Consultancy, Research Funding, Speakers Bureau; Celgene: Consultancy, Research Funding, Speakers Bureau; Gilead Kite: Consultancy, Research Funding, Speakers Bureau; Incyte: Consultancy, Speakers Bureau; Janssen: Consultancy, Research Funding, Speakers Bureau; Novartis: Consultancy, Speakers Bureau; Roche: Consultancy, Research Funding, Speakers Bureau; AbbVie: Research Funding; BeiGene: Consultancy, Speakers Bureau; Genmab: Consultancy; MorphoSys: Consultancy. Harigae: Bristol Myers Squibb: Honoraria; Novartis Pharma: Honoraria, Research Funding; Chugai Pharma: Honoraria; Janssen Pharma: Honoraria; Ono pharma: Honoraria, Other: Subsidies or Donations; Astellas Pharma: Other: Subsidies or Donations; Kyowakirin: Other: Subsidies or Donations. Bond: Kite/Gilead: Honoraria. Andreadis: Merck: Research Funding; BMS: Research Funding; CRISPR Therapeutics: Research Funding; GenMAB: Research Funding; Novartis: Research Funding; Roche: Current equity holder in publicly-traded company, Ended employment in the past 24 months; Epizyme: Honoraria; Incyte: Honoraria; TG Therapeutics: Honoraria; Kite: Honoraria; Karyopharm: Honoraria; Atara: Consultancy, Honoraria. McSweeney: Kite-Gilead: Consultancy, Honoraria, Research Funding, Speakers Bureau; Gamida: Consultancy, Honoraria; TG Theraputics: Consultancy, Honoraria; Autolous Limited: Research Funding; Novartis: Research Funding; NKARTA: Research Funding; Allovir: Research Funding. Newsome: Novartis: Current Employment. Degtyarev: Novartis: Current Employment, Current equity holder in publicly-traded company. Del Corral: Novartis: Current Employment. Andreola: Novartis: Current Employment, Current holder of stock options in a privately-held company. Masood: Novartis: Current Employment, Current holder of stock options in a privately-held company. Schuster: AbbVie, Acerta, Celgene/Juno, DTRM Bio, Genentech, Incyte, Merck, Novartis, Portola, and TG Therapeutics: Research Funding; Acerta, AlloGene, AstraZeneca, BeiGene, Celgene/Juno, Genentech/Roche, LoxoOncology, Novartis, and Tessa Therapeutics: Consultancy; Acerta, AlloGene, AstraZeneca, BeiGene, Celgene, Genentech/Roche, LoxoOncology, Novartis, Nordic Nanovector, Pfizer, and Tessa Therapeutics;: Honoraria; Novartis: Other: Personal fees, Patents & Royalties; AbbVie, Celgene, Novartis, Juno, Nordic Nanovector, and Pfizer: Other: Steering Committee Participation. Jaeger: BMS/Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees; Norvartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Gilead: Honoraria, Membership on an entity's Board of Directors or advisory committees; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees. Westin: Kite, a Gilead Company: Consultancy, Research Funding; Novartis: Consultancy, Research Funding; Bristol Myers Squibb: Consultancy, Research Funding; Genentech: Consultancy, Research Funding; MorphoSys: Consultancy, Research Funding; AstraZeneca: Consultancy, Research Funding; ADC Therapeutics: Consultancy, Research Funding; Umoja: Consultancy; Iksuda Therapeutics: Consultancy; Curis: Research Funding; Morphosys: Research Funding; 47 Inc: Research Funding.

Abstract: Donor-derived hematopoiesis was assessed in 17 patients who received allogeneic marrow grafts from HLA-matched siblings between 1971 and 1980. Complete blood counts were normal or near normal in all patients except one. Chimerism analyses, using either dual-color XY-chromosome fluorescence in situ hybridization (FISH) or analysis of variable number tandem repeat loci, indicated that 15 out of 16 patients had greater than 97% donor-derived hematopoiesis, whereas 1 patient had indeterminate chimerism. All 12 recipients of grafts from female donors exhibited polyclonal hematopoiesis by X-linked clonal analysis with the use of molecular probes. Of the 17 recipients, 9 exhibited a less than 1.0-kilobase shortening of granulocyte telomere length compared with their respective donors, according to terminal restriction fragment analysis or flow-FISH with a fluorescein-labeled peptide nucleic acid probe. These data suggest that under standard transplantation conditions, the stem cell proliferative potential is not compromised during hematopoietic reconstitution.