ALBERT

Description: Key Points In contrast to their suppressive effects on T cells, src-kinase inhibitors strongly enhance IL-12 production in human myeloid cells. This effect is synergistic to TLR2 or TLR4 signaling, whereas inhibition of src-kinases alone does not trigger DC activation.

Description: Unrelated donors are commonly used for hematopoietic stem cell transplants, but graft-versus-host disease (GVHD) is a major problem. We investigated whether transplantation of CD34+ or CD133+ enriched stem cells with add-back of ten million T-cells per kg from unrelated donors would prevent acute GVHD in pediatric patients in combination with pharmacologic immunosuppression. Eighteen patients (1 CML in second chronic phase, 2 MDS, 4 ALL in CR1, 4 ALL in CR2, 1 JMML, 1 AML in CR1, 3 AML in CR2, 1 Wiskott-Aldrich syndrome and 1 NHL in CR2) were transplanted with G-CSF mobilized peripheral blood stem cells (PBSC) from HLA-matched unrelated donors (n = 18). Median of age was 8.9 years (0.5 to 18 years). Conditioning regimens were performed according to national therapy protocol guidelines. On the day of transplant patients received a median of 13.5 (4.5 to 30.0 x 106) CD34+ or CD133+ enriched stem cells and an aliquot of unmanipulated PBSC containing 10 x 106 T-cells per kg. GVHD prophylaxis consisted of cyclosporine A (CSA) and short course methotrexate (MTX) on day +1, +3 and +6. Engraftment was rapid with a median of 19.6 days in sixteen patients. Two patients failed to engraft at first. However, full donor chimerism and stable engraftment was achieved in both patients after cessation of CSA treatment and an additional stem cell boost without any reconditioning. One patient with ALL developed acute GVHD grade III (skin and gut) after cessation of CSA treatment, but responded well to treatment with CSA and steroids. None of the other 17 patients developed acute GVHD 〉 grade I. Thirteen are alive and well with a median follow-up of 578 days (101 to 1095 days). Three patients died of severe infectious complications and two due to relapse (JMML, AML). Compared to a historical control group of patients transplanted with highly purified CD34+ selected cells, the group with add-back of 10 x 106 T-cells per kg showed significantly higher T-cell counts (p=0.008, Wilcoxon Rank sum test) on day 90 after transplantation with a median number of six T-cells/μl in the control group and a median number of 294 T-cells/μl in the study group. We conclude that add-back of 10 x 106 T-cells per kg in combination with CSA and short course MTX improves T-cell recovery and appears to be a safe T-cell dosage regarding acute GVHD in the setting of allogeneic peripheral blood stem cell transplantation from unrelated donors.

Description: Graft failure is a rare but life-threatening complication after transplantation of hematopoietic stem cells. Treatment comprises immunoablative reconditioning regimens and a second stem cell donation from the same or from a different donor as soon as possible to minimize the time of pancytopenia and its sequelae. We report a cohort of 11 pediatric patients with leukemias (acute lymphatic n=4, acute or chronic myeloic/MDS n=4) and severe aplastic anemia (n=3) who experienced graft rejection after TBI, busulphan or melphalan based myeloablative transplantation from mismatched related donors (MMRD) (n=6) or after cord blood/matched unrelated donor (MUD) transplantation (n=5) between 2000 and 2006. In the latter the original donor was not available a second time. Thus, all patients were re-transplanted with CD34+ positive selected or CD3/CD19 depleted stem cells from a second, haploidentical parental donor (MACS method, Miltenyi Biotec). Median time span from diagnosis of graft rejection to second donation was 16 days. The reconditioning regimens consisted of total lymphoid irradiation or cyclophosphamide, thiotepa (5mg/kg), fludarabine (120 mg/m2) and ATG/OKT3. A median number of 25×106/kg of body weight stem cells with 60.000/kg residual T cells were infused. Mofetilmycophenolat was given as GvHD prophylaxis, if residual T cells exceeded 25 000/kg bw. Sustained engraftment was achieved in all patients (ANC〉500/μl: 9 (11–32) days). No GvHD 〉 grade II was observed. T cell recovery was delayed, however no lethal viral infection occurred. Severe organ toxicity was observed in 2 patients (BOOP, hemorrhagic cystits) and moderate mucositis in 11 patients. 8/11 patients are disease free (median follow up 1.5 (0.3–6.6) years; 1 year EFS=73%). Causes of death were: BOOP (n=1), infection (n=1); only one patient with refractory AML relapsed. Thus, transplantation of stem cells from haploidentical donors represents a realistic option to rescue patients with graft failure within a short time span and for whom a second donation of the original donor is not available. The use of a different donor may help to avoid a second rejection.

Description: Introduction: Transplantation of haematopoietic stem cell (HSCT) from human leucocyte antigen (HLA)-disparate parental donors presents an approach for the treatment of patients lacking an HLA-matched donor, but little is known about differences in immune reconstitution as compared to conventional BMT. We prospectively compared paediatric recipients of positively selected CD34+ peripheral blood stem cells from unrelated or HLA-mismatched donors vs. recipients of unmanipulated bone marrow from matched sibling donors. Patients: Immune reconstitution was studied in 20 children (20 transplants [5 sibling, vs. 8 UD, 7 haplo]; median age was 9,6 years; range 7m-26y; 7 female, 13 male). Blood samples were drawn before allo-HSCT, on days 14 (take), 30, 60, 100, 200 and 365 and 〉15months after SCT. Methods: We analyzed lymphocyte subpopulations using flow cytometry. Cytokines (IFNg, IL2, TNFa, IL4, IL5, IL10) were determined by FACS after in vitro stimulation with PMA, ionomycin and brefeldin for 24h. Additionally, we measured IL2, IL7, IL13, IL15, IFNg and TGFb in unstimulated sera by ELISA. Further more, we studied TREC values and did spectratype analysis by real time-PCR and gel electrophoresis. Results: After allo-HSCT, NK-cells were the cells, which regenerated first. In T-cells, decreased absolute counts could be detected as well as an inverted CD4-CD8-ratio during the first year after SCT. In CD4+ T-cells, the memory phenotype (CD45RO+) predominated. Sibling recipients show a faster T-cell regeneration than recipients of UD or mismatched family donors (MM). As to cytokine levels in unstimulated sera, IFNg levels remained stable, while we saw high level of IL4 shortly after allo-HSCT; IL4 levels decreased during the first year after SCT. TGFb showed increased levels post-transplantation for up to two years. In stimulated T-cells, we measured a rise in Th2-cytokines (IL4, IL5, IL10) until d60 and a decrease of IFNg/TNFa. Th2-cytokines returned to pre-transplantation levels until d200, whereas Th1-cytokines rise to higher level than before transplantation. We could find that IL2 was produced predominantly by CD4+ / IFNg+ cells and by CD8+cells. Patients who received T-cell depleted stem cell preparations show lower IFNg and TNFa values and higher Th2-cytokine levels than patients who received bone marrow. TREC counts appear earlier in sib HSCT (median d60) than in MM-transplant (median d200). As to spectratype values, we found a distribution of the 24Vb gene families of 4,18% per Vb-family with clonal expansion, especially in the first months after HSCT, of BV6b〉BV23〉BV1〉BV16.

Description: Introduction: Since the seminal paper of LeBlanc in 2008, despite several negative studies, the scientific community has retained optimism with respect to the usefulness of mesenchymal stroma cells (MSCs) in refractory acute graft-versus-host disease (GvHD). A prevailing theme of past studies was that, while pediatric GvHD responded to MSCs, adult GvHD did not. As reported, we developed proprietary protocols GMP-quality MSC production from bone marrow (BM) mononuclear cells expanded in platelet lysate-enriched media. Patients and Methods: We present treatment data with MSC-FFM for 61 children/adolescents and 31 adults with either "only" steroid-refractory (SR) GvHD (27%) or GvHD which had additionally proven refractory to up to five additional lines of therapy (MR-GvHD) (73%). Pediatric patients tended to have more MR-GvHD than adults. Patients from 23 centers in 6 countries were included. Most patients had severe GvHD (37% °III, 59% °IV, Glucksberg scale). 31 patients (34%) were female,61 male (66%). 69 have a malignant disease (75%), and 23 a non-malignant (25%) disease as indication for transplantation. Donors were MSD (n=21, 23%), MUD (n=56, 61%), haploidentical (n=14, 15%), and 1 MMUD (1%). Patients received myeloablative conditioning with TBI-, Treosulfan-, Busulfan- and Fludarabine-based regimen, with serotherapy, mostly ATG. 89% of patients had had immunosuppression for GvHD prophylaxis, 13% CSA alone, 49% CSA+MTX or MMF; or others (n=15, 16%). Median onset of aGvHD was at 40 days (range: 6-280 d), another 28 days (range: 5-380) until the first infusion of MSC-FFM. Recommended dose and interval is 4 weekly doses of 1-2M MSC/kg body weight; the average patient received only 3 doses, the interval approximately staggered as recommended, with a median dose of 1.4M MSC/kg. Any reduction in GvHD activity by at least one full grade was classified as a partial (PR), absence of any degree of GvHD as a complete response (CR). Results: Day-28 response rates were 84%/25%/59% overall (OR)/CR/PR for children and 80%/35%/45% for adults resulting in a day-28 response rate for the entire cohort: 82%/28%/54%). At last follow-up (LFU) many of the pediatric responders had continued to improve from partial to complete response to response rates of 84%/59%/25% OR/CR/PR, in adults responses were largely unchanged (77%/35%/42%; LFU for the entire cohort: 81%/51%/30%). GvHD °III and °IV were equally likely to respond or resolve. Looking at response rates of SR- vs. MR-GvHD, of the SR-GvHD 96% responded (MR-GvHD: 81%), as well as early and LFU responses in SR-GvHD were more likely to be complete responses (60% and 72% for SR-GvHD, 16% and 43% for MR-GvHD, day-28 and LFU, respectively). Day-28-response was highly predictive of long-term responsiveness, in that only one non-responder on day 28 achieved a response long term, and only two initial partial responders' GvHD relapsed to the same degree of severity as before MSC treatment. The historical expected survival probability for patients with steroid-refractory severe GvHD being in the order of 20% at 6 months. The patients reported here with °III or °IV aGVHD achieved 6-month overall survival probabilities of 65% and 61%, respectively. In total 6 patients relapsed and died (of note: only 69 patients were at risk), 28 deaths were treatment-related. 6-month overall survival rates for children and adults were 68% and 54%, respectively (n.s.). In terms of adverse reactions to MSC-FFM, one case each of spontaneously remitting headache and nausea/vomiting were reported shortly after infusion of the thawed cells. Both events occurred in children and were possibly related to the rapid infusion of DMSO-containing ice-cold fluid and not the active substance. Conclusion: MSC-FFM emanates as a highly efficacious treatment for severe pediatric and adult advanced GvHD, with OR in excess of 80% and survival rates approximating those of patients without GvHD. The very low relapse mortality may suggest that severe GvHD effectively suppresses leukemic recurrence. Better and faster responses of SR- vs. MR-GvHD make a case for early treatment with MSC-FFM. Disclosures Bader: Medac: Patents & Royalties, Research Funding; Cellgene: Consultancy; Neovii: Research Funding; Riemser: Research Funding; Novartis: Consultancy, Speakers Bureau. Kuci:Medac: Patents & Royalties. Kuci:Medac: Patents & Royalties. Bug:Amgen: Honoraria; Jazz Pharmaceuticals: Other: Travel Grant; Neovii: Other: Travel Grant; Astellas Pharma: Other: Travel Grant; Janssen: Other: Travel Grant; Celgene: Honoraria; Novartis Pharma: Honoraria, Research Funding. Lang:Miltenyi Biotec: Patents & Royalties, Research Funding. Sykora:Aventis-Behring: Research Funding; medac: Research Funding. Seifried:Medac: Other: BSD owns IP and is contract manufacturer; Uniqure BV: Research Funding. Bonig:Kiadis Pharma: Consultancy.

Description: Abstract: Here we report for the first time on long term follow-up data of a cohort of 60 patients who received TCRαβ and CD19 depleted peripheral blood stem cell grafts from haploidentical family donors within a prospective, multi-center, single-arm, phase I/II clinical study (EudraCT No.: 2011-005562-38). As planned, 30 pediatric and 30 adult patients were enrolled in this trial: All patients received a reduced-intensity conditioning regimen consisting of fludarabine (160 mg/m2), thiotepa (10 mg/kg), melphalan (140 mg/m2) and either antithymocyte globulin (Grafalon, 15 or 30 mg/kg, N=53) or 7 Gy total nodal irradiation (N=7). MMF (40 mg/kg/day) was administered as single-agent GVHD prophylaxis until Day 30. Results: Sixty patients with a median age of 18.5 years (range 1-63) were treated. Twenty-five patients had AML, 17 ALL, 6 MDS/MPS and 1 each had multiple myeloma and acute undifferentiated leukemia. Six patients had solid tumors (soft tissue sarcomas and neuroblastomas) and 4 non-malignant disorders (SCID, Wiskott-Aldrich syndrome, lysosomal storage disorder and sickle cell anemia). Of the 56 patients with malignant disease, 33 were transplanted in complete (CR), 11 in partial (PR) and 12 in non-remission (NR). Twenty of the 56 patients with malignant diseases received a 2nd or 3rd transplantation within this protocol. In total, 88 depletion procedures were performed with the CliniMACS plus System (Miltenyi Biotec, Germany) at 7 GMP laboratories and resulted in a median T and B cell log depletion of 4.7 (range 3.6-5.3) and 3.4 (range: 2.3-4.5), respectively. The median number of infused CD34+ cells and TCRαβ T cells was 12.4 × 106 /kg BW (range 4.0 - 54.9) and 1.4× 104 /kg BW (range 0.06-6.4), respectively. Engraftment was rapid with a median of 13 (range 9-41) and 15 (11-38) days to reach ANC 〉500 cell/µl and PLT 〉 20,000 cells/µl. Nine patients rejected the graft. Eight of them were successfully re-transplanted and 1 patient died. One patient received stem cell boosts from the original donor due to poor graft function. On day 100, peripheral T cell chimerism was completely donor-type in 44 of 47 evaluable patients, and mixed in 3. None of the patients developed grade III/IV aGVHD and only 6 patients (10%) had grade II aGVHD. Of 47 evaluable patients 4 had severe cGVHD (9%), and 6 (13%) and 5 (11%) had moderate and mild cGVHD, respectively. CMV reactivation was seen in 25 (42%) mainly adult patients, and only 1 (2%) patient developed disease. Twenty-one (35%) patients had ADV reactivation and 7 children and 1 adult (13%) developed disease. Only 1 case of EBV disease (encephalitis) occurred (2%). A median of 221 (range 8-1230) CD3+ cells/µl was reached on day 100. The median numbers of CD3/CD4+ and CD3/CD8+ cells at 1 year post transplant were 316 (range 1-1173) and 308 (range 0-2203) /µl. As of July 15 2018, 57 patients have completed the 2 year follow-up, died or discontinued the study resulting in a median follow-up of 706 days (range 18-800). 37 patients (62%) are alive and 23 (38%) died. Relapse was the major cause of death (N=12) followed by ADV infection (N=3), ARDS (N=3) and 1 case each of cardiac arrest, multi organ failure, sepsis due to graft failure and demyelinating neuropathy. Cause of death was not reported in 1 patient. Eight of the 20 patients who received the 2nd or 3rd transplantation are alive; 1 discontinued the study prematurely. Of the 23 patients transplanted in PR or NR, 13 are alive. The Kaplan-Meier estimated probabilities of overall survival, disease-free survival (DFS) were 62% and 53%, respectively. Cumulative incidences of relapse and NRM at 2 years were 34% and 20%, respectively. For those patients with leukemia receiving a first SCT in CR, the overall survival, DFS and relapse rate were 75%, 64% and 20%, respectively. Conclusion: The transplantation of TCRαβ and CD19 depleted haploidentical hematopoietic stem cell grafts was safe and feasible. Decentralized production using the CliniMACS System was feasible and reliably resulted in grafts containing sufficient numbers of stem cells with only minimal numbers of co-infused TCRαβ T cells. None of the patients developed grade III-IV aGVHD and incidence of cGVHD was acceptable. Given the heterogeneous patient cohort with respect to age, disease, remission status and number of previous transplants, the outcome of patients after 2 years follow-up is promising. Disclosures Lang: Miltenyi Biotec: Patents & Royalties, Research Funding. Handgretinger:Miltenyi Biotec: Patents & Royalties: Co-patent holder of TcR alpha/beta depletion technologies, Research Funding. Meisel:Amgen: Consultancy. Mielke:KIADIS Pharma: Speakers Bureau; Miltenyi Biotec: Speakers Bureau; DGHO: Speakers Bureau; EHA: Speakers Bureau; Celgene: Speakers Bureau. Niederwieser:Novartis: Research Funding; Miltenyi: Speakers Bureau. Bader:Neovii: Research Funding; Medac: Patents & Royalties, Research Funding; Riemser: Research Funding; Cellgene: Consultancy; Novartis: Consultancy, Speakers Bureau. Kuball:Gadeta (www.gadeta.nl): Consultancy, Equity Ownership, Patents & Royalties: on gd T cells and receptors and isolation strategies, Research Funding; Miltenyi Biotec: Research Funding; Novartis: Research Funding. Bonig:Miltenyi Biotec GmbH: Honoraria, Research Funding. Karitzky:Miltenyi Biotec GmbH: Employment. Holtkamp:Miltenyi Biotec GmbH: Employment. Malchow:Miltenyi Biotec GmbH: Employment. Siewert:Miltenyi Biotec GmbH: Employment. Biedermann:Miltenyi Biotec GmbH: Employment. Bethge:Neovii GmbH: Honoraria, Research Funding; Miltenyi Biotec GmbH: Consultancy, Honoraria, Research Funding.

Description: We report the first prospective, multi-center, open-label, single-arm phase I/II clinical trial that assesses the safety and feasibility of stem cell transplantation with TCRalpha/beta and CD19-depleted haploidentical grafts generated with the CliniMACS plus System (Miltenyi Biotec, Germany) in combination with a reduced-intensity conditioning in pediatric patients suffering from various malignant and non-malignant diseases (www.clinicaltrialsregister.org; 2011-005562-38). All patients received single agent MMF as short-term GVHD prophylaxis (40mg/kg/day for 30 days). The speed of immune reconstitution was measured in two core labs using standardized methods and the MACSQuant flow cytometry device (Miltenyi Biotec, Germany). Results: Thirty patients from six hospitals were treated (13 female, 17 male; median age 7 years, range 1 - 17 years). Of the 30 recipients, 10 had ALL, 8 had AML, 6 had solid tumors (soft tissue sarcomas and neuroblastomas), 3 had MDS/MPS, and 1 each with lysosomal storage disorder, SCID, and Wiskott Aldrich syndrome. Disease status in acute leukemias/MDS was: CR1 (n=4), relapsed/refractory (n=17). 5/6 patients with solid tumors had relapsed metastatic disease. The conditioning regimen consisted of 15 or 30 mg ATG (Fresenius/Grafalon) or 7 Gy total nodal irradiation, 160 mg/m2 fludarabine, 10 mg/kg thiotepa, and 140 mg/m2 melphalan. The median number of CD34+ cells, TCRalpha/beta+ cells and CD20+ cells infused was 14.6 x 106 (range, 4 - 54.9), 14 x 103 (range, 0.62 - 40.6) and 0.55 x 105 (range, 0.04 - 1.85), respectively. In addition, significant numbers of NK and TCRgd+ cells/kg were infused - 6.67 x 107 (median; range, 0.68 - 18.2) and 1.58 x 107 (median; range, 0.13 - 4.7), respectively. All 30 patients tolerated the infusion of haploidentical stem cell grafts well. Twenty-five patients had primary engraftment of ANC 〉 500 cells/µL at a median of 12 days (range, 10 - 18) and PLT 〉 20,000 cells/µL at a median of 15 days (range, 11 - 27). Peripheral T-cell chimerism at the time of engraftment was completely donor in 19/25 patients (76%), mixed in 3 (12%), and not measured in three. Five patients experienced primary graft failure and 2 had secondary graft failure. All except of one were successfully re-transplanted. None of the recipients developed severe acute GVHD grades III - IV. Only 1 patient had acute GVHD grade II that started on day 22. The vast majority of patients (96.7%) experienced no or only grade I acute GVHD despite minimal GVHD prophylaxis after transplantation. Samples from 24/25 patients with primary engraftment were evaluable for immune reconstitution (Figure 1). On day 28, the majority of WBC were NK cells (median 309 cells/µL; range, 64 - 1026). The second main type of cells were CD3+ cells (median 151 cells/µL; range, 9 - 953), mostly TCRgd+ (median 87 cells/µL; range, 7 - 891). At day 100, TCRab+ cells equalled TCgd+ cells (median 108 vs. 116 cells/µL). B cells recovered more slowly, with a median of 255.5 cells/µL (range, 1 - 1218) on day 63. ADV reactivation contributed most to infectious complications following transplantation. In total, 16/30 patients had ADV DNAemia or were positive in stool. Additionally, seven patients were tested positive for CMV (blood or urine). BK virus was present in 5 patients with 3 patients experiencing cystitis. No EBV reactivation was observed. Two patients had bacterial sepsis, 1 moderate, 1 fatal (due to non-engraftment).No fatal viral infection occurred within 100 days. One molecular relapse was observed within 100 days post transplantation that was treated with blinatumomab. Two of the 30 transplanted patients died within 100 days after transplantation: 1 patient due to sepsis following graft failure (non-relapse mortality) and 1 due to relapse. On day 100, chimerism was completely donor in 20 patients and mixed in two. Conclusions: The CliniMACS depletion system of TCRab+ and CD19+ cells yielded a large number of CD34+ cells, NK cells and TCRgd+ cells, that could be infused safely into pediatric patients with minimal risk of severe acute GVHD. The immune reconstitution was rapid and there was no TRM associated with viral or fungal infections. Coupled with a reduced-intensity regimen, the overall TRM was low. Longer follow up will provide essential information on chronic GVHD and survival outcomes. Figure 1 Immune Reconstitution after transplantation of TCR-alpha/beta and CD19 depleted haploidentical stem cell grafts Figure 1. Immune Reconstitution after transplantation of TCR-alpha/beta and CD19 depleted haploidentical stem cell grafts Disclosures Bader: Riemser: Research Funding; Neovii Biotech: Research Funding; Servier: Consultancy, Honoraria; Novartis: Consultancy, Honoraria; Medac: Consultancy, Research Funding. Karitzky:Miltenyi Biotec: Employment. Holtkamp:Miltenyi Biotec: Employment. Siewert:Miltenyi Biotec: Employment. Bönig:Miltenyi Biotec: Consultancy, Honoraria, Research Funding. Handgretinger:Miltenyi Biotec: Patents & Royalties: Co-Patentholder of TcRalpha/beta depletion technology.

Description: The CD31 monoclonal antibody, LYP21, binds to the CD31 domain 6 and inhibits the human mixed-lymphocyte reaction (MLR) in a specific and dose-dependent fashion. A synthetic CD31 peptide based on human CD31 epitope (amino acids 551 to 574) recognized by LYP21 is equally effective in inhibiting the MLR. In this study, we used the murine homolog of CD31 peptide 551 to 574 and a control peptide to study the role of CD31 molecule on T-cell activation. In vitro, CD31 peptide inhibited the MLR across several major and minor histocompatibility differences in a specific and dose-dependent fashion, similar to the results observed in the human system. Maximal inhibition was achieved at a dose of 200 μg/mL. In the cytotoxic T-lymphocyte (CTL) assay, CD31 peptide inhibited CTL responses by 97%. To study the in vivo effect of this peptide, graft-versus-host disease (GVHD) across minor histocompatibility barriers was induced in the B10.D2 (H-2d) → BALB/c (H-2d) model. BALB/c recipients received CD31 peptide (100 μg/d), or phosphate-buffered saline (PBS), or control peptide (100 μg/d) intraperitoneally (IP) for the first 5 weeks. CD31 peptide delayed onset of graft-versus-host disease and significantly increased long-term survival. Twelve of 14 mice receiving CD31 peptide survived more than 100 days after transplantation, as compared with none of 10 mice receiving PBS and none of five mice receiving control peptide (P = .0001). Long-term engraftment of allogeneic bone marrow was documented in all transplanted mice by polymerase chain reaction (PCR) analysis of microsatellite region in the interleukin (IL)-1β gene. Our data suggest that the CD31 molecule has an important functional role in T-cell activation in vitro and in vivo.

Description: PG27, an active fraction purified from an extract of a Chinese herb,Tripterygium wilfordii hook f, was used to prevent graft-versus-host disease (GVHD) in a murine model. Lethally irradiated BALB/c (H-2d) recipients of B10.D2 (H-2d) donor grafts were given daily intraperitoneal injections of PG27 (40 mg/kg per day) for the first 35 days after transplantation. Control mice were given daily injections of solvent vehicle (Ethanol and Cremophor EL). All the control recipients (15/15) died of GVHD within 90 days, but all the recipients given prophylactic treatment with PG27 (15/15) survived beyond 100 days without any signs of GVHD. Furthermore, the GVHD-free recipients were used as donors, and their bone marrow and spleen cells were transplanted into lethally irradiated normal BALB/c (same party) or lethally irradiated normal C3H (H-2k, third party) mice. Although 10 of 10 same-party recipients survived more than 100 days without any signs of GVHD, 10 of 10 third-party C3H recipients died of GVHD within 40 days. Further studies of PG27 in the murine BCL1 leukemia/lymphoma model demonstrated that animals treated with PG27 partially retained the graft-versus-leukemia (GVL) effect of the graft without GVHD. These results suggest that treatment with PG27 induces host-specific tolerance and retains the GVL effect of allogeneic marrow grafts.