ALBERT

Description: Abstract 4496 Purpose: To investigate the impact of pre-transplant CMV serostatus of donor or recipient on outcome of patients undergoing allogeneic hematopoietic stem cell transplantation (Allo-SCT) for Multiple Myeloma (MM). Patients and methods: We retrospectively followed 99 consecutive patients who underwent reduced-intensity conditioning (RIC) Allo-SCT for MM in our cancer centre at Marseille between January 2000 and January 2012. Based upon CMV serostatus, patients were classified as low risk (donor [D]-/recipient [R]-) 17 patients (17.1%), intermediate risk (D+/R) 14 patients (14.1%), or high risk – either (D-/R+) 31 patients (31.3%) or (D+/R+), 37 patients (37.3%). Results: Cumulative incidence of CMV reactivation was 39% with a median time of 61 days (26–318). Three patients (3%) developed CMV disease. Two factors were associated with CMV reactivation: CMV serostatus group (low: 0% vs intermediate: 29% vs high: 50%; p=0.001) and the presence of grade II–IV acute GvHD (Hazard Ratio: HR=2.1 [1.1–3.9]). Thirty-six of the 39 patients (92%) with CMV reactivation did not present positive detection of CMV after a 21-day median duration preemptive treatment with ganciclovir. Cumulative incidence of day 100 grade II–IV acute GvHD, 1-year chronic GvHD and day 100 transplantation related mortality (TRM) were 37%, 36% and 9%, respectively. CMV reactivation and serostatus were not associated with increased GvHD and TRM or short survival. Only the presence of acute GvHD as a time dependent variable was significantly associated with increased TRM (p=0.005). Two-year overall and progression free survival were 56% and 34%, respectively. Conclusion: Donor and recipient CMV serostatus and acute GvHD are independent factors for increased CMV reactivation in high-risk MM patients undergoing RIC Allo-SCT. However, we did not find any influence of CMV reactivation on post transplantation outcome. CMV monitoring and pre-emptive treatment strategy could in part explain these results. Novel prophylactic measures such as immunotherapy and drug prophylaxis need to be considered in this specific group of patients, warranting further prospective studies. Legend: CR, complete remission; VGPR, very good partial remission; PR, partial remission, PD, progressive disease; Flu, fludarabine; Bu, busulfan; ATG, antithymocyte globulin; CR, complete remission; VGPR, very good partial remission; PR, partial remission, PD, progressive disease; MRD, matched related donor; URD, unrelated donor; GVHD, graft versus host disease; CSA, cyclosporine A; MMF, mycophenolate mofetyl. Disclosures: No relevant conflicts of interest to declare.

Description: Hematopoietic stem cells are defined by their ability both to self-renew and to differentiate into cells that repopulate all hematopoietic lineages. A common lymphoid progenitor (CLP) from mouse marrow has been phenotypically purified and shown to only transiently repopulate all lymphoid lineages (T, B, and NK) but not myeloid lineages when transplanted into lethally irradiated recipients (Kondo et al, 1997). Using the rhesus macaque as a model for human hematopoiesis, we asked whether lineage-restricted repopulating cells contribute to hematopoietic output and for how long following engraftment. In order to follow the progeny of progenitor or stem cell clones in vivo, retroviral vectors were used to mark primitive hematopoietic cells before reinfusion into lethally irradiated autologous recipients. The conditions utilized result in high level of stable retroviral marking in all lineages. We have previously reported use of the sensitive Linear Amplification Mediated - Polymerase Chain Reaction (LAM-PCR) showing that a highly polyclonal set of stable clones accounts for myelopoiesis (Schmidt et al, 2002). In the current study, detailed characterization of the full array of clones contributing to granulocytes, T-lymphocytes, and B-lymphocytes post-engraftment was performed, via sequence analysis of individual clones delineated by individual insertion site sequences at various time points following transplantation of CD34+ cells. Thus far, we have identified 59 granulocyte and 148 T-lymphocyte clones at 1 month following transplantation. Most clones detected at this time point uniquely contribute to only the lineage from which they were identified, only three clones were common to both lineages (1.5% overlap, 95%CI=(0–3.1%)), suggesting independent cells are responsible for hematopoietic reconstitution at this early time point. Six-months following transplantation fewer clones were detected to contribute to hematopoiesis. Interestingly, of the 22 granulocyte and 46 T-lymphocyte clones identified, only two were shared between both lineages (3.0% overlap, 95%CI= (0–7.2%)), further supporting the hypothesis that lineage committed progenitors are responsible for both early and potentially more stable hematopoiesis in this model. To our knowledge, no other study has provided such an extensive characterization of clones contributing to early or more stable in vivo hematopoiesis in the primate model. Preliminary sequence specific tracking experiments reveal that the clones contributing at six-months remain lineage specific over time. Further tracking of clones is being conducted to fully assess the role of such lineage specific progenitor cells in B-lymphopoiesis and long-term hematopoiesis.

Description: Until recently, the risk of insertional mutagenesis using retroviral vectors for gene therapy has been estimated to be low. Owing to reports of proto-oncogenes activation in mice and humans, this estimation is being re-evaluated in regards to the nature of susceptible loci and the number of genetic hits needed for oncogenesis. Separating the impact of overexpressing a growth-altering transgene from the insertional events themselves is particularly important to address in long-term repopulating hematopoietic stem cells. We here report a high frequency of proviral insertions at the MDS1-EVI1 locus in the engrafted gene-modified hematopoiesis of non-human primates. We have recovered vector-genome junction sequences from mature granulocytes and mononuclear cells of 22 rhesus macaques that were transplanted 6 months to 6 years previously with autologous mobilized CD34+ peripheral blood stem cells transduced with an amphotropic Moloney murine leukemia virus-derived vector containing a neomycin-resistance marker gene. Using a modified LAM-PCR method, we have retrieved and analyzed 702 independent integration sites that mapped to a unique genomic location. While several transcription units harbor two or three proviral insertions, we have identified, in 9 animals, an unexpected 13 unique integration events within the two first introns of the MDS1 gene. MDS1 is adjacent to EVI1, a well-known retrovirally-activated zinc finger transcription factor in a number of murine leukemogenesis studies. We used insertion-specific primers to confirm that the fusion sequences between the MDS1 locus and the 5′-LTR of the vector were detectable in four of the animals for which we had the longest follow-up (4 to 6 years). The fusion sequence was present both in purified granulocytes and lymphocytes of one of the animal, and only in granulocytes in the other three animals. In order to determine if the cells carrying proviral insertions at the MDS1-EVI1 locus have a selective growth advantage, we performed quantitative PCR experiments with neomycin and MDS1/5′-LTR-specific probes. The two animals analyzed to date do not have any evidence of clonal expansion of the MDS1-targeted granulocyte population, and the number of retrovirally-transduced circulating cells remains stable 5 and 6 years after transplantation. As retroviral insertion upstream of a proto-oncogene may lead to its activation, we investigated MDS1-EVI1 expression by RT-PCR in neo+ CFU that harbor a proviral insertion at the MDS1 locus. The 8 colonies screened from two animals do not express any of the various MDS1-EVI1 transcripts, suggesting that the transcriptional regulation of the locus has not been altered. Our study suggest that the MDS1-EVI1 locus is particularly susceptible to retroviral integration but the competing hypothesis that proviral insertion within this region favors engraftment and long-term contributions to hematopoiesis will be difficult to eliminate, since specific insertions may have favored engraftment of such clones. It is however important to mention that the long-term follow-up of these primates has revealed completely normal hematopoiesis and lack of any progression towards neoplasia. Systematic analysis of proviral insegration sites in this appropriate pre-clinical model is essential as it provides decisive information for risk assessment in the development of integrating vectors, as well as offering further insights into the mechanisms of retroviral insertion.

Description: Murine leukemia virus (MLV) vectors have been studied extensively in animal models and utilized for over a decade in clinical trials of gene therapy directed at hematopoietic stem and progenitor cells MLV have a number of limitations, including inefficient transduction of quiescent cells and difficulty in maintaining stable high-level expression. More recently concerns have arisen regarding their safety regarding activation of adjacent proto-oncogenes and resultant leukemogenesis. We have previously reported that lentiviral vectors derived from the simian immunodeficiency virus (SIV) were efficient at transducing rhesus CD34+ cells, resulting in high-level in vivo marking with transduced progeny cells up to one year post-transplantation.(Hanawa et al, 2004) A comparison of vector integration sites in these animals compared to animals receiving MLV-transduced cells revealed different patterns, showing that SIV integrants strongly favored entire transcription units and gene-dense regions of the genome, compared to MLV that favored regions surrounding transcription start sites.(Hematti et al, 2004). Animals receiving MLV-transduced cells had highly non-random engraftment with integrants in or near the the MDS1/EVI1 gene complex. To evaluate long-term safety implications of the SIV vector-mediated CD34+ cell gene transfer, we analyzed the insertional sites in granulocytes, T cell, and B cells from 3 rhesus macaques which were transplanted three years ago with transduced, autologous cytokine-mobilized peripheral blood CD34+ cells. All three animals continued to show significant marking and expression levels in T cells, B cells and granulocytes, with mean GFP + levels of 6.7% (range, 3.3–13.0%), 7.4% (4.2–13.4%) and 5.6% (3.1–10.5%), respectively. Vector insertion site analysis by linear amplification-mediated PCR method at three years continued to show highly polyclonal reconstitution. Subsequent cloning and sequencing data confirmed long-term polyclonality with vector-containing cells and there was no evidence for any worrisome common integration sites, with no integrants detected in the MDS1/EVI1 region, in contrast to results with the MLV vector. These results indicate that the SIV vector system can result in stable and efficient long-term expression in progeny of transduced CD34+ cells, without the worrisome integration profile previously reported in our model with MLV vectors.

Description: Allogeneic Hematopoietic Stem Cell Transplantation (HSCT) is the only curative treatment for many patients with hematologic disease. Unfortunately, the transplanted immune system can reacts against the patient, inducing Graft-versus-Host Disease (GvHD). GvHD is the leading cause of treatment related mortality and morbidity following HSCT and is expected to increase in the forthcoming years. Pathophysiology and long-term determinants of GvHD are still largely unknown. The French Society for Stem Cell Transplantation and Cell Therapy (SFGM-TC) launched the CryoStem project in 2011 with the goal of establishing a national biobank on GvHD. CryoStem has been selected and funded to the extent of 5,5 millions € over a period of 9 years by the French Government’s Investissements d’Avenir program. As of today, CryoStem brings together 33 HSCT Units and 23 Biological Resources Centers that actively contribute to a networked, prospective, longitudinal and standardized peripheral blood samples collection with concomitant well documented clinical data. Patients sampling is scheduled before and after HSCT, depending on the occurrence or not of acute and/or chronic GvHD. Three types of pre-analytical products are processed and stored, according to standardized techniques: viable cells in DMSO, dried cell pellets and plasma. Samples and clinical data are anonymized and centralized in CryoStem-dedicated web-based database application. Recruitment started in July 2012: currently, about 1,590 patients and 690 related donors have been included. So far, 3,820 blood samples have been processed, corresponding to 48,400 frozen pre-analytical samples. In order to guarantee the quality of frozen samples, an ISO9001 certification of the network is ongoing. National projects are the only way to acquire the large number of samples needed for statistically significant results in a reasonable time. The collection is on embargo until further notice and the first call for scientific projects is expected to be launched in December 2014. CryoStem is a crucial step toward progress in human GvHD research: it will allow collaborative studies between leading French and international research organizations and foster technology transfer with potential industrial players whenever possible to eventually improve the translational research on GvHD. Disclosures No relevant conflicts of interest to declare.

Description: Abstract 4545 The monitoring of chimerism is a standard procedure for assessing hematopoietic engraftment and achievement of full donor lymphoid chimerism after RIC based Allo-SCT. Post graft donor lymphocyte infusions are often decided on this evaluation. These studies have however a cost issue, all the more no consensus presently exists on when and how often to perform them. We retrospectively analysed the impact of acute GvHD in the prediction of allograft chimerism in our RIC program where TCC was serially assessed at 30, 60 and 90 days after Allo-SCT. We selected patients with hematologic malignancies (with the exclusion of myelofibrosis) transplanted between 2001 and 2010 after Fludarabine-Busulfan-ATG RIC from a HLA identical donor. 115 patients fulfilled all criteria including at least one T cells chimerism (TCC) determination between day 30 and 120. Allo-SCT was performed from familial donor in 92 patients (80%) and from MUD in 23 patients (20%). The conditioning regimen consisted of fludarabine (90 to 180 mg / m2), Busulfan (8 mg / kg orally or 6.4 mg / kg IV) and rabbit anti-thymocyte globulin (ATG) (2.5 or 5 mg /kg). As for chimerism study, recipient peripheral blood T lymphocytes were positively sorted by a mix of anti-CD4 and CD8 immunomagnetic beads (Dynal, Compiègne, France). T-cell purity was controlled by flow cytometry and was always 〉 or =95%. Genomic DNA was amplified using fluorescent PCR primers for polymorphic variable number tandem repeats (VNTR) or short tandem repeats (STR). Mixed T-cell chimerism was defined as between 5 and 94% recipient cells, and full chimerism was defined as the presence of more than 95% donor cells. Full TCC was achieved in 94 patients (82%) at a median of 77 (30–120) days post transplant. Fifty eight patients (50.4%) developed acute GvHD. The cumulative incidence of Grade 2–4 GvHD in our population is 32% (95% CI 23–41). Overall the results showed that each of the 37 patients developing grade ≥ 2 AGVHD had a Full TCC prior day 120. On the other hand, all mixed chimerism were documented in patients not presenting Grade≥2 AGVHD (21 of the 78 patients (27%) without grade ≥ 2 AGVHD) (p=.002). No other parameter (ATG dose, Donor type…) achieved this level of individual prediction. These results, in a very homogenous population, are in line with the concept that full TCC is more likely to occur when patient develops significant aGVHD. Although they deserve further and deeper confirmation in different populations, they address the value of systematic routine chimerism surveillance (outside clinical studies) in patients presenting acute GvHD following RIC Allo-SCT. The modulation of TCC determination might represent an interesting cost and resources saving. Disclosures: No relevant conflicts of interest to declare.

Description: Acute myeloid leukemia (AML) is the most common acute leukemia diagnosed in adults, characterized by significant heterogeneity in terms of biology and clinical outcome. Improvements in sequencing technologies have led to the discovery of frequent somatic mutations in epigenetic modifiers, placing epigenetic deregulation in the center of AML. Yet, the global view and the impact of this deregulation on disease characteristics are under investigation. To gain a more comprehensive understanding of epigenetic deregulation in AML, particularly the heterogeneous subset with normal karyotype (CN-AML), associated with intermediate clinical prognosis, we performed H3K27me3 profiling on CN-AML patient samples. Primary bone marrow or peripheral blood samples containing more than 80% of blasts were selected from the Institut Paoli-Calmettes Biological Resources Center inventory for the purpose of genetic and epigenetic studies. We initially analyzed 35 CN-AML samples by ChIP coupled with hybridization on oligonucleotide promoter arrays (Chip-chip) for genomic H3K27me3 distribution. Clustering analysis revealed 586 highly H3K27me3-variable genomic regions across patients corresponding to 461 genes mostly involved in chromatin organization. The heterogeneity in the H3K27me3 profile was characterized by a remarkable H3K27me3 enrichment at the chromosome 6 p22.2-22 region that encompasses 70 kbp within the major HIST1 cluster. This striking H3K27me3 enrichment was covering 11 histone genes and was partially overlapping with the focal deletion at 6p22 found in acute lymphoblastic leukemia. The HIST1 H3K27me3 enrichment profile clearly distinguished 2 groups of CN-AML patients based on their HIST1 H3K27me3 level. In order to independently extend this observation, we analyzed the H3K27me3 status by using ChIP followed by qPCR (ChIP-qPCR) at the same HIST1 genomic locations, in an independent cohort of 51 CN-AML patients. This revealed the presence of this abnormal epigenetic profile in about 50% of the patients. CN-AML samples were split in two groups, according to the median H3K27me3 enrichment levels at the HIST1 cluster genes. These two groups were analyzed for clinical and molecular characteristics. Patients with high HIST1 H3K27me3 level had a markedly higher incidence of NPM1 mutation (89% vs. 40%; p= 1.75x10-5) and a lower incidence of WT1 mutation (0% vs. 20%; p=0.028). No significant association was observed with FLT3 (ITD and TKD), IDH1/2, DNMT3A nor ASXL1 mutations. Patients with high HIST1 H3K27me3 level had a significant longer leukemia free survival at 5 years (allo-grafted patients censored, LFS-allo; 13.33 vs. 8.92 months p=0.0053). Moreover, multivariate analysis showed that HIST1 H3K27me3 status provided a more powerful prognostic indicator than the NPM1mut/FLT3-ITDneg and NPM1/FLT3-ITD genotypes. In conclusion,using epigenetic profiling, our analysis has enabled the discovery of a new epigenetic alteration that affects CN-AML and impacts prognosis. We demonstrate that the HIST1 cluster is targeted by epigenetic events that lead to high H3K27me3 level and predicts a good prognosis. This may help refine risk stratification in AML, identifying a further group of patients unlikely to benefit from allogeneic transplantation in first remission. Overall, our data provide a proof of concept that epigenetic profiling could be used to discover new biomarkers with prognostic value. Disclosures No relevant conflicts of interest to declare.

Description: Introduction: Allogenic hematopoietic stem cell transplantation (SCT) is often the only curative treatment for a part of patients with malignant or benign hematological disorders. The availability of a HLA matched related or unrelated donor remains a major obstacle which can be resolved by the presence of alternative donors, like umbilical cord blood, partially matched unrelated or haploidentical family donors. T cell repleted SCT using haploidentical donors (H-SCT) has considerably improved over the last years due to better control of Graft Versus Host Disease (GVHD) using post-transplantation cyclophosphamide (PTCY). Our study aims to shed light on the interest of chimerism evaluation after H-SCT and to elucidate the cause of graft failure (GF) in our H-SCT recipients. Patients and methods: We conducted a retrospective study of 179 patients (pts) who received a H-SCT in our center from august 2009 to march 2016. The pts characteristics are reported in Table 1 and 2. One hundred sixty pts received a Reduced Intensity (RIC) and 19 pts a MyeloAblative Conditioning (MAC) regimen. Twenty-eight pts had refractory or relapsed acute myeloid leukemia. All pts received PTCY on days 3 and 4 and Ciclosporine A and mycophenolate of mofetil since day 5 for GVHD prophylaxis. Twenty pts received H-SCT for relapse after a first SCT with a HLA identical donor. Stem cell sources were bone marrow (BM) for 19 pts, peripheral blood stem cells (PBSC) for 157 pts and BM+PBSC for 3 pts. The donors were children (79 daughters sons), parents (4 fathers, 14 mothers), family members (75 siblings, 1 cousin, 1 nephew) and 5 unknown. Chimerism analysis: The peripheral blood CD3 positive cells were selected using the kit Human CD3 Positive selection (Stemcell) and genotyping was performed with the PowerPlex 18D System (Promega), a multiplex STR system allowing the co-amplification of 18 loci. DSAs (donor-specific anti-HLA antibodies): The DSAs were identified with the use of highly sensitive solid-phase immunoassays. Desensitization therapy with Bortezomib, Rituxan and plasmapheresis was performed in two patients with a high level of DSAs. Results: Chimerism could be evaluated in 167 patients, where 162 had ≥ 98% of donor cells at a median time of 35 d post-transplant (range 15-170) without secondary GF. One patient suffering from sickle disease had stable mixed chimerism (82% donor). Only 4 pts had primary GF (2%), all of donor-recipient pairs were ABO compatible, all of them received a Baltimore conditioning whereas 2 pts had BM as SC source. Recipients with PBSC as SC source had poor CD34+ cells infused (1,2 and 2,3 x 106/kg). One of the 4 pts had a high level of DSAs. A patient with mycosis fungoide had secondary GF after relapse (PBSC/DSAs negative). One patient with a high level of DSAs (78%) had a primary graft failure. Two pts with a high level of DSAs who were desensitized by the described procedure. Forty-five patients had a positive anti-HLA antibody no specific to donor with a median level of 3% (range: 1-45%) with no impact on engraftment (Anti-HLA antibody class I in 30 pts, class II in 11 pts and mixed in 4 pts). The median number of CD34+ cell count was 5,2x 106/kg (range: 1,3-17) in 160 pts who had PBCS as SC source. With a median follow up of 532 d (range: 164-1587d), 123 pts are alive and 116 of them are in CR. Conclusion: Full donor chimerism is obtained in almost all pts after T cell repleted H-SCT with PTCY. Primary graft failure occurred principally in pts with high levels of DSAs and poor graft CD34+ cells. Chimerism analysis post H-SCT is not crucial and might focus on a small group of high-risk pts. Detection of DSAs is crucial in HLA mismatched transplants not only to select the most appropriate donor but also to include a pre-transplantation strategy of desensitization to minimize the risk of graft failure. Disclosures No relevant conflicts of interest to declare.

Description: Introduction: allogeneic transplantation (allo-HSCT) is a curative treatment for patients with advanced lymphoma. Haploidentical (haplo-SCT) transplantation extended the accessibility to allo-HSCT, overcoming the issue of donor availability. However, alternative donor allo-HSCT is still considered at higher risk of non-relapse mortality due to the HLA disparity and thus an anticipated higher incidence of GVHD. In this context, the use of a non myeloablative conditioning (NMAC) regimen combined with post transplantation cyclophosphamide (PT-Cy) based GVHD prophylaxis may reduce procedure related toxicity. The aim was to evaluate the toxicity and efficacy of haplo-SCT using NMAC with PT-Cy in advanced lymphoma patients. Methods: We here report the retrospective experience of a bicentric transplantation program. We analyzed a cohort of lymphoma patients undergoing Haplo-SCT and homogeneously receiving NMAC and PT-Cy. Inclusion criteria were: 1) first allo-HSCT for advanced lymphoma between 2009 and 2018; 2) haploidentical donor; 3) NMAC (fludarabine cyclophosphamide and 2 gray TBI GVHD prophylaxis consisted of PT-Cy day+3 and +4 , cyclosporine A and MMF starting from day +5. Multivariate analyses included age, disease type (NHL vs HL), HCT-CI (〈 vs ≥ 3), graft source (PBSC vs BM), disease status at haplo-SCT (CR vs other). Results: One hundred forty seven patients (73 NHL; 74 HL) with a median age of 46 years (range: 19-71) were included. PBSC (peripheral blood stem cell) was used as graft source in 96 patients (65%). Patients received a median number of 3 conventional chemotherapy lines before haplo-SCT (1-8). Sixty-five (44%) had relapse after Auto-HCT. At the time of haplo-SCT, 96 patients (66%) were in complete remission. The cumulative incidences of day+100 grade 2-4 and 3-4 acute GVHD were 30% and 3%, respectively. The cumulative incidences of 2-year chronic and moderate or severe chronic GVHD were 13% and 8%, respectively. With a median follow up of 39 months (6-114), 2-year NRM was 14%, with a trend for higher risk in patients with HCT-CI ≥ 3 (HR 0.39, 95CI [0.15-1.04] p = 0.061) while age was not associated with an increased risk of NRM (HR 1.01, 95CI [0.98-1.05], p = 0.450). Two-year cumulative incidence of relapse (CIR) was 21% and 18% in HL and NHL patients, respectively. Disease status at the time of haplo-SCT was strongly associated with relapse (HR 2.99, 95CI [1.41-6.35], p = 0.004) In HL patients, 2-year PFS, OS and GRFS were 65%, 77% and 57%, respectively, while corresponding values in NHL patients were 65%, 69% and 55%, respectively. Two-year PFS and GRFS were significantly higher in patients who underwent haplo-SCT in CR (PFS: CR vs. no CR: 72% vs. 55%, p=0.045; GRFS: CR vs. no CR: 63% vs. 42%, p=0.010). There was a trend for better 2-year OS in CR (OS: CR vs. no CR: 78% vs. 63%, p=0.063. Conclusion: We confirm the feasibility of haplo-SCT using NMAC and PT-Cy with low incidence of GVHD (notably severe forms) and NRM. In addition, we observed a relatively low incidence of relapse (19%) in this cohort of heavily pretreated patients, underlining a potent graft-versus-lymphoma effect after haplo-SCT, leading to promising survivals, including high rate of GRFS (〉50%), suggesting a preserved long term quality of life in survivors. We conclude that NMAC haplo-SCT with PT-Cy should be considered as a valuable curative option for advanced lymphoma patients, with a favorable toxicity profile and promising long term survival. Figure Disclosures Stoppa: celgene: Other: travel fees, lecture fees; takeda: Other: travel fees. Carlo-Stella:MSD: Honoraria; BMS: Honoraria; Janssen: Other: Travel, accommodations; Boehringer Ingelheim: Consultancy; Genenta Science sr: Consultancy; Sanofi: Consultancy, Research Funding; ADC Therapeutics: Consultancy, Other: Travel, accommodations, Research Funding; Novartis: Consultancy, Research Funding; Servier: Consultancy, Honoraria, Other: Travel, accommodations; F. Hoffmann-La Roche Ltd: Honoraria, Other: Travel, accommodations, Research Funding; Rhizen Pharmaceuticals: Research Funding; Celgene: Research Funding; Amgen: Honoraria; Takeda: Other: Travel, accommodations; Janssen Oncology: Honoraria; AstraZeneca: Honoraria. Chabannon:EBMT: Other: Working Party Chair, Board member; Fresenius Kabi: Other: research support; Miltenyi Biotech: Other: research support; Terumo BCT: Other: speaker's fees; Celgene: Other: speaker's fees; Novartis: Other: speaker's fees; Gilead: Other: speaker's fees, hospitalities; Sanofi SA: Other: research support, speaker's fees, hospitalities. Santoro:Takeda: Speakers Bureau; BMS: Speakers Bureau; Roche: Speakers Bureau; Abb-Vie: Speakers Bureau; Amgen: Speakers Bureau; Celgene: Speakers Bureau; Servier: Consultancy, Speakers Bureau; Gilead: Consultancy, Speakers Bureau; AstraZeneca: Speakers Bureau; Pfizer: Consultancy, Speakers Bureau; Arqule: Consultancy, Speakers Bureau; Lilly: Speakers Bureau; Sandoz: Speakers Bureau; Eisai: Consultancy, Speakers Bureau; Novartis: Speakers Bureau; Bayer: Consultancy, Speakers Bureau; MSD: Speakers Bureau; BMS: Consultancy. Blaise:Sanofi: Honoraria; Jazz Pharmaceuticals: Honoraria; Molmed: Consultancy, Honoraria; Pierre Fabre medicaments: Honoraria.

Description: BACKGROUND Reduced intensity conditioning (RIC) combining fludarabine, busulfan and ATG is commonly used in patients with advanced age and/or comorbid conditions, thus deemed unfit for standard myeloablative conditioning (MAC) regimens (i.e. BuCy or CyTBI12). Although non-relapse mortality (NRM) is dramatically reduced with RIC, relapse remains a major concern. In younger patients, myeloablative doses of busulfan in combination with fludarabine (i.e. myeloablative reduced toxicity conditioning [MA-RTC] regimen) produce similar antitumor effect compared with standard MAC while keeping low NRM. The feasibility of such an approach for older patients is not known. We hypothesized that a pharmacokinetics (PK) guided strategy could improve the safety of busulfan administration, allowing the use of myeloablative doses in older patients. STUDY DESIGN AND METHODS We compared the outcome of patients older than 55 years with hematological malignancies included in a prospective monocentric single arm trial (BxPK: NCT02483325) evaluating the feasibility of PK-guided busulfan doses in myeloablative conditioning regimen (BxPK group: fludarabine 150 mg/m² + IV busulfan targeted AUC 5300 x 4 days + ATG 5 mg/kg) before matched sibling (MSD) or unrelated (URD) donor AlloSCT, with a retrospectively enrolled control cohort of patients with same inclusion criteria, treated during the same period but receiving fixed busulfan dose RIC regimen including fludarabine (150 mg/m²), IV busulfan (260 mg/m²) and ATG (5 mg/kg) [Bx2 group]. The primary objective was 2-year progression-free survival (PFS). Hazard ratio of BxPK vs. Bx2 were adjusted by age, disease risk index (DRI), donor type and hematopoietic cell transplantation comorbidity index (HCT-CI). RESULTS We analyzed 83 consecutive patients (BxPK: n=27; Bx2: n=56) without significant difference in baseline characteristics between both conditioning groups. In the BxPK and Bx2 groups: median age was 65 (range: 57-70) and 63 (range: 55-70) years, respectively (p = 0.552); 10/10 URDs were used for 15 (56%) and 37 (66%) patients, respectively (p = 0.493); HCT-CI was ≥ 3 in 18 (67%) and 28 (50%) patients , respectively (p = 0.232); and DRI was high in 5 (19%) and 5 (9%) patients, respectively (p = 0.369). Based on PK data from day-6 busulfan administration, 22 (81%) patients had dose adjustment (increased and decreased dose in 12 and 10 patients, respectively) in the BxPK group. Median busulfan AUC on day-2 (post adjustment) was 5287 µmol.min (range: 3326-7556). Four patients had AUC 〉 6000 µmol.min on day-2. Grade 3-4 mucositis (BxPK vs Bx2: 52% vs. 11%, p 〈 0.001) and nausea (BxPK vs Bx2: 11% vs 0%, p = 0.050) were more frequently observed in the BxPk group. No difference was observed between BxPK and Bx2 patients in grade 3-4 liver (BxPK vs Bx2: 15% vs 11%, p = 0.810), renal (BxPK vs Bx2: 0% vs 1.8%, p = 1) and gastrointestinal tract (BxPK vs Bx2: 11% vs 0%, p = 0.450) toxicities. There was a trend to higher cumulative incidence of grades 2-4 acute graft-versus-host disease (GVHD) at 100 days in the BxPK group (BxPK vs Bx2: 41% vs 29%, p = 0.058) while no difference was observed in 2-year chronic GVHD (BxPK vs Bx2: 41% vs. 36%, p = 0.547). Those trends were confirmed by multivariate analyses (acute GVHD: HR 2.22, 95Cl [1.10-4.48], p = 0.026; chronic GVHD: HR 1.30, 95Cl [0.60-2.80], p=0.502) With a median follow up of 33 months (range: 9-60), 2-year NRM was 19% and 18% (p=0.960) in the BxPK and Bx2 group, respectively. Multivariate analysis confirmed the absence of significant increase in the risk of NRM in the BxPK group (HR 1.11, 95CI [0.36-3.45], p = 0.859). The 2-year cumulative incidence of relapse was 19% and 31% (p=0.269) in the BxPK and Bx2 group, respectively (HR 0.55, 95IC [0.20-1.56], p = 0.264). No significant difference in 2-year PFS (BxPK vs Bx2: 62% vs. 51%, p = 0.391) and OS (BxPK vs Bx2: 70% vs. 61%, p = 0.667) was observed. CONCLUSION In patients older than 55 years who are usually candidates for RIC regimen, the use of PK-guided busulfan myeloablative dose allows delivering higher antitumor intensity without increasing NRM. Beyond the feasibility, we observed low incidence of relapse (19%) and promising OS (70%) suggesting that conditioning intensification may lead to long term disease control. These trends need to be confirmed in a larger comparative study for validating the optimal conditioning intensity in older and/or unfit patients. Disclosures Stoppa: takeda: Other: travel fees; celgene: Other: travel fees, lecture fees. Vey:Novartis: Consultancy, Honoraria; Janssen: Honoraria. Chabannon:Novartis: Other: speaker's fees; Celgene: Other: speaker's fees; Sanofi SA: Other: research support, speaker's fees, hospitalities; Gilead: Other: speaker's fees, hospitalities; EBMT: Other: Working Party Chair, Board member; Fresenius Kabi: Other: research support; Miltenyi Biotech: Other: research support; Terumo BCT: Other: speaker's fees. Blaise:Pierre Fabre medicaments: Honoraria; Sanofi: Honoraria; Molmed: Consultancy, Honoraria; Jazz Pharmaceuticals: Honoraria.