3498 Introduction: Oral mucositis is a complication of conditioning treatment that produces pain and morbidity in allogeneic hematopoietic stem cell transplant (allo-HSCT) recipients. The rationale of this study was to evaluate the efficacy of a calcium phosphate mouth rinse (Caphosol) vs standard regimen in 40 adult patients undergoing allo-HSCT. Patients and Methods: 40 patients treated with allo-HSCT (31 from unrelated donors, 9 from siblings) performed in Hematology and BMT center in Katowice in 2009 were randomized and stratified by the conditioning regimen (busulfan-, treosulfan- or TBI- based), type of transplant (unrelated or related) and age into two equal groups. Treatment group received Caphosol washes 4 times daily from first day of conditioning until reaching ANC 0.2 G/l. Control group received standard topical mouth care with salvia, antibacterial and antifungal solutions. During the trial patients subjectively assessed level of pain in mouth and in pharynx using 0–10 scale and swallowing problems using 0–5 scale. Mucositis was judged by experienced physician. Nonparametric Mann-Whitney U-tests were used for statistical analysis. Results: Average oral toxicity in WHO scale in Caphosol vs control group was 0.9 vs 1.8 (p=0.02), duration of mucositis was 3.2 vs 7.1 days (p=0.02). Total parenteral nutrition (TPN) due to mucosits was required in Caphosol vs control group in 0 vs 6 pts, average duration of TPN was 0 vs 1.9 days (p=0.009). Analgetics were required, respectively, in 3 vs 9 pts and analgesy lasted for 1.1 vs 3.4 days (p=0.047). Average subjective peak pain in mouth was 0.85 vs 1.75 (p=0.005) and in pharynx 1.95 vs 2.2 (NS) in Caphosol vs control group, average pain intensity was lower in Caphosol group throughout the whole period of mucositis. Intensity of swallowing problems tended to be lower in Caphosol group (NS). Acute GVHD was observed in 7 vs 9 pts in Caphosol vs control group and its average degree was 0.5 vs 0.9 (NS). Conclusions: Caphosol mouth rinse in the allo-HSCT recipients is associated with decrease of oral toxicity, lower peak pain due to mucositis and its shorter duration. In consequence, comfort of life is improved and the incidence of acute GVHD is reduced, as well as the requirement of TPN and analgetics. Disclosures: No relevant conflicts of interest to declare.

Objective: Oral mucositis occurs in 75% to 100% of allogeneic HSCT recipients can cause pain, facilitate infections, delay discharge, and threaten life. The aim of the study was to evaluate prophylaxis with the remineralizing mouthwash solution of supersaturated calcium phosphate rinse (SCPR) with Fomukal on measures of severity of mucositis and consequent interventions and complications, in comparison to Caphosol, already evaluated post-transplant. Materials/Methods: In this prospective, randomized, non-inferiority trial, 46 patients undergoing allogeneic HSCT were equally randomized to Fomukal or Caphosol, each administered four times daily from initiation of conditioning until the granulocyte count ≥0.2 G/L. Hematologist measured the daily severity of mucositis according to a WHO scale and patients self-assessed its symptoms. Need for analgesics, anti-infectious drugs, total parenteral nutrition (TPN) and incidence of complications were also assessed. Results: Fomukal vs. Caphosol groups had the same all following indicators: median measures of WHO oral mucositis reduction (0 vs. 2; P = NS), length of disease course (0 vs. 6 days; P = NS), peak and mean mouth (1 vs. 2; P = NS and 0.06 vs. 1; P = NS) and throat pain (1 vs. 1; P = NS and 0.22 vs. 0.31; P = NS), and peak and mean swallowing problems (1 vs. 1; P = NS and 0.19 vs. 0.25; P = NS). Analgesics need (7 vs. 10 patients; 0 vs. 0 days; P = NS) and the need for antifungals (1 vs. 2 drugs; P = NS) were not different, while the need for antibiotics and antivirals (3.5 vs. 5 drugs; P = 0.011 and 1 vs. 2 drugs; P = 0.023) were lower in the Fomukal group. Measures of complications: infections (7 vs. 12 patients, P = NS) and a GVHD (13 vs. 14 patients, P = NS, grade 1 vs. 1, P = NS) did not differ. Discussion: Both SCPR mouth rinses, Fomukal and Caphosol, were associated with similar effectiveness in reducing severity of oral mucositis.

Factors contributing to relapses and GVHD following allogeneic Hematopoietic Stem Cell Transplantations (HSCT) from HLA-matched unrelated donors are not well established. We analyzed 35 patients (pts) transplanted from HLA 10/10 alleles (A, B, C, DRB1, DQB1) matched unrelated donors (URD) in the Dept. of Hematology and BMT, Katowice, Poland, with use of the same standard operating procedure from January 2004 until March 2006. Indication for HSCT was AML (13 pts), ALL (8), CML (7), MDS (2), PNH (3), CLL (1), myeloid sarcoma (1). Preparative regimen was Treosulfan+Fludarabine (23 pts), TBI+Cy (9) and Bu+Cy (3). Alleles encoding 11 minor Histocompatibility Antigens (mHA: HA-1, HA-2, HA-3, HA-8, HB-1, ACC-1, ACC-2, HwA-9, HwA-10, UGT2B17, HY) were analyzed for each donor-recipient pair with use of Dynal AllSet mHA typing kit and PCR-SSP method. Only immunogenic mHA mismatches were analyzed. Information on whether mHA mismatches might result in Host-versus-Graft or Graft-versus-Host responses was established with use of the minor Histocompatibility Knowledge Database of Leiden University Medical Center’s minor Histocompatibility Workshop. Patients transplanted from donors with mHA mismatched in HVG direction had significantly higher probability of relapse (64+/− 8% versus 10+/− 9%, p=0.003) when compared to pairs without mHA HVG immonogenicity. Patients transplanted from donors with mHA mismatched in GVH direction had higher probability of aGVHD (88+/− 8% versus 53+/− 11%, p=0.14) and cGVHD (41+/− 16% versus 37+/− 17%, p=0.65) when compared to pairs without GVH immunogenicity. GVHD was also observed more often on day +100 (33% versus 6%, p=0.06) when mHA mismatch in GVH direction was present. Observed influence of HVG and GVH immonogenicity on probability of relapse and GVHD did not lead to significantly different survival in observed groups of pts. These results indicate that mHA immunogenic mismatches in HVG and GVH direction may be responsible for relapse and GVHD, respectively, in HSCT recipients from HLA-matched unrelated donors. The study is being continued to confirm these primary observations and to establish the associations of specific mHA mismatches with HSCT outcomes. Impact of mHA mismatch on probability of relapse and GVHD Immunogenicity of mHA mismatches HVG no HVG p # of patients 18 17 Relapse at 1 year 64%+/−8 10%+/−9 0.003 Immunogenicity of mHA mismatches GVH no GVH p # of patients 16 19 aGVHD 88%+/− 8 53%+/−11 0.14 cGVHD at 1 year 41%+/−16 37%+/−17 0.65 Impact of mHA mismatch on probability of survival Immunogenicity of mHA mismatches HVG GVH only HVG only GVH no HVG no GVH p # of patients 9 9 7 10 Survival at 9 months 63%+/−17 57%+/−25 83%+/−15 69%+/−15 0.86

Introduction Failure to respond to steroid therapy for intestinal acute graft-versus-host disease (aGvHD) is associated with limited further therapeutic options. Fecal microbiotherapy is defined as the perfusion of treated stool from one or several healthy donors via the upper or lower gastrointestinal (GI) route aiming at improving microbial diversity and functionality. Here we report clinical outcomes from a 76-patient cohort with steroid refractory (SR) GI-aGvHD treated with the pooled allogenic fecal microbiotherapeutic MaaT013. Twenty-four patients were treated in the prospective, single-arm, phase IIa, HERACLES study (NCT03359980) while 52 patients were treated in an expanded access program (EAP). Patients and methods For HERACLES, 24 patients with grade III-IV SR-GI-aGvHD were treated with MaaT013 in 26 European sites, as a 2 nd line therapy after SR diagnosis and evaluable for treatment response. In EAP, 52 patients with steroid-dependent or SR-GI-aGvHD (classical n=41, late onset n=3, overlap syndrome n=8) were treated. These patients had previously received and failed 1 to 6 lines (median 3; 40/52 received ruxolitinib) of GvHD systemic treatments. GI-GvHD response was evaluated weekly and 28 days after day (D) 0 (inclusion for HERACLES or 1st dose for EAP). For all patients, GI-overall response rate (ORR) at D28 was defined as the proportion of patients achieving complete response (CR), very good partial response (VGPR) or partial response (PR), compared to D0, without the use of additional systemic therapy. Other endpoints included the best overall response (BOR) achieved at any time, and overall survival (OS). Prepared under GMP, MaaT013 is characterized by a highly consistent richness of 455 ±3% OTUs and an Inverse Simpson index > 20. Treatment comprised 3 MaaT013 doses, each composed of 30 g of feces in 150 mL volume of inoculum (total 90 g of feces from 4 to 8 healthy donors) administered by enema (except for 2 EAP patients by nasogastric tube). All patients received at least 1 MaaT013 dose, 92% (HERACLES) and 87% (EAP) at least 2 doses, and 50% (HERACLES) and 71% (EAP) the full treatment course. In HERACLES, the reasons for not applying the 3 rd dose were death (n=5), physician decision to introduce salvage therapy (n=5), and ICU hospitalization (n=2)). Results In HERACLES, the GI-ORR was 38% including 5 CR, 2 VGPR and 2 PR. In EAP, positive GI-response was achieved in 31/52 patients (60% with 16 CR, 11 VGPR and 4 PR). Considering the GI-BOR, 13/24 (54%) and 35/52 (67%) achieved at least a PR in HERACLES and EAP respectively. In HERACLES, OS was 29% at month (M) 6 and 25% at M12. OS was significantly higher in responding (R) patients (achieving at least PR at D28) compared to non-responding (NR) (44% vs 20% at M6 and 44% vs 13% at M12, logrank p=0.047). In EAP, OS was 48% at M6 and 37% at M12, and significantly higher in R patients compared to NR (71% vs 17% at M6 and 62% vs 6% at M12, logrank p<0.0001). In HERACLES, treatment with MaaT013 was characterized by excellent tolerance: 252 Treatment-Emergent Adverse Events (TEAE) were reported for the 24 patients, the majority being infections (79%) and GI disorders (62%), as expected in GvHD patients. Of these 252 TEAE, only 2% (5 serious events in 2 patients) could not reasonably be excluded from being related to MaaT013 by the investigators. Shotgun sequencing in these 5 TEAE revealed that the causative infectious agents could not be detected in the administered MaaT013. In EAP, the safety profile of MaaT013 was considered satisfactory for all patients. 16S microbiome analyses were performed in the HERACLES population and showed that MaaT013 produced an early increase in α-diversity at genus level with a significant increase in Richness index at all evaluated timepoints (p <0.003). At D28, R patients had higher values of α-diversity indices (Shannon p=0.005 and Richness p=0.038) compared to NR patients, and higher proportions of MaaT013-derived species in the total composition of R microbiota (p=0.043). Conclusion We herein report the treatment of 76 SR-GI-aGvHD patients using a full ecosystem, pooled-donor, high-richness biotherapeutic. The D28 GI-ORR was 38% and 60% in HERACLES and EAP respectively and this clinical benefit positively and significantly impacted OS (44% and 62% M12 in HERACLES and EAP R patients respectively). MaaT013 was shown to be safe and effective in these heavily immunocompromised patients, warranting further exploration of this approach. Figure 1 Figure 1. Disclosures Malard: JAZZ pharmaceuticals: Honoraria; Sanofi: Honoraria; Astellas: Honoraria; Biocodex: Honoraria; Therakos/Mallinckrodt: Honoraria; Janssen: Honoraria. Loschi: CELGENE/BMS: Honoraria; AbbVie: Ended employment in the past 24 months, Honoraria; Gilead: Ended employment in the past 24 months, Honoraria; Novartis: Ended employment in the past 24 months, Honoraria; Servier: Ended employment in the past 24 months, Honoraria; MSD: Honoraria. Cluzeau: Agios: Honoraria; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: travel, accommodations, expenses, Speakers Bureau; Roche: Consultancy, Honoraria; BMS/Celgene: Consultancy, Honoraria, Speakers Bureau; Jazz Pharma: Consultancy, Honoraria; Abbvie: Consultancy, Honoraria, Speakers Bureau; Amgen: Speakers Bureau; Pfizer: Other: travel, accommodations, expenses; Astellas: Speakers Bureau; Takeda: Other: travel, accommodations, expenses. Huynh: Jazz Pharmaceuticals: Honoraria. Holler: MaaT Pharma: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees. Vehreschild: SocraTec R&D GmbH: Consultancy, Speakers Bureau; Pfizer: Consultancy, Speakers Bureau; Ferring: Consultancy, Speakers Bureau; Farmak International Holding GmbH: Consultancy, Honoraria, Speakers Bureau; Bio-Mérieux: Consultancy, Speakers Bureau; Basilea: Consultancy, Speakers Bureau; Arderypharm: Consultancy, Speakers Bureau; Alb Fils Kliniken GmbH: Consultancy, Speakers Bureau; Takeda Pharmaceutical: Research Funding; Seres Therapeutics: Research Funding; Roche: Consultancy, Research Funding, Speakers Bureau; Organobalance: Consultancy, Research Funding, Speakers Bureau; Merck/MSD: Consultancy, Research Funding, Speakers Bureau; MaaT Pharma: Consultancy, Research Funding; Immunic AG: Consultancy, Research Funding, Speakers Bureau; Glycom: Research Funding; Gilead Sciences: Consultancy, Research Funding, Speakers Bureau; Evonik: Research Funding; Da Volterra: Consultancy, Research Funding, Speakers Bureau; Biontech: Research Funding; Astellas Pharma: Consultancy, Research Funding, Speakers Bureau; 3M: Research Funding. Gasc: MaaT Pharma: Current Employment. Plantamura: MaaT Pharma: Current Employment. Mohty: Sanofi: Honoraria, Research Funding; Pfizer: Honoraria; Novartis: Honoraria; Takeda: Honoraria; Jazz: Honoraria, Research Funding; Janssen: Honoraria, Research Funding; Gilead: Honoraria; Celgene: Honoraria, Research Funding; Bristol Myers Squibb: Honoraria; Astellas: Honoraria; Amgen: Honoraria; Adaptive Biotechnologies: Honoraria.

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