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Acute graft-versus-host disease (GVHD) is treated with systemic corticosteroid immunosuppression. Clinical response after 1 week of therapy often guides further treatment decisions, but long-term outcomes vary widely among centers, and more accurate predictive tests are urgently needed. We analyzed clinical data and blood samples taken 1 week after systemic treatment of GVHD from 507 patients from 17 centers of the Mount Sinai Acute GVHD International Consortium (MAGIC), dividing them into a test cohort (n = 236) and 2 validation cohorts separated in time (n = 142 and n = 129). Initial response to systemic steroids correlated with response at 4 weeks, 1-year nonrelapse mortality (NRM), and overall survival (OS). A previously validated algorithm of 2 MAGIC biomarkers (ST2 and REG3α) consistently separated steroid-resistant patients into 2 groups with dramatically different NRM and OS (P < .001 for all 3 cohorts). High biomarker probability, resistance to steroids, and GVHD severity (Minnesota risk) were all significant predictors of NRM in multivariate analysis. A direct comparison of receiver operating characteristic curves showed that the area under the curve for biomarker probability (0.82) was significantly greater than that for steroid response (0.68, P = .004) and for Minnesota risk (0.72, P = .005). In conclusion, MAGIC biomarker probabilities generated after 1 week of systemic treatment of GVHD predict long-term outcomes in steroid-resistant GVHD better than clinical criteria and should prove useful in developing better treatment strategies.

Late acute (LA) graft-versus-host disease (GVHD) is persistent, recurrent, or new-onset acute GVHD symptoms occurring >100 days after allogeneic hematopoietic cell transplantation (HCT). The aim of this analysis is to describe the onset, course, morbidity, and mortality of and examine angiogenic factors associated with LA GVHD. A prospective cohort of patients (n = 909) was enrolled as part of an observational study within the Chronic GVHD Consortium. Eighty-three patients (11%) developed LA GVHD at a median of 160 (interquartile range, 128-204) days after HCT. Although 51 out of 83 (61%) achieved complete or partial response to initial therapy by 28 days, median failure-free survival was only 7.1 months (95% confidence interval, 3.4-19.1 months), and estimated overall survival (OS) at 2 years was 56%. Given recently described alterations of circulating angiogenic factors in classic acute GVHD, we examined whether alterations in such factors could be identified in LA GVHD. We first tested cases (n = 55) and controls (n = 50) from the Chronic GVHD Consortium and then validated the findings in 37 cases from Mount Sinai Acute GVHD International Consortium. Plasma amphiregulin (AREG; an epidermal growth factor [EGF] receptor ligand) was elevated, and an AREG/EGF ratio at or above the median was associated with inferior OS and increased nonrelapse mortality in both cohorts. Elevation of AREG was detected in classic acute GVHD, but not chronic GVHD. These prospective data characterize the clinical course of LA GVHD and demonstrate alterations in angiogenic factors that make LA GVHD biologically distinct from chronic GVHD.

Background Subjects with lower gastrointestinal (GI) acute graft-versus-host disease (aGvHD) generally respond poorly to therapy, and therefore have increased morbidity and mortality. Vedolizumab, a gut-selective antibody targeting α4β7 integrin, is approved for the treatment of inflammatory bowel diseases. Vedolizumab interferes with gut-trafficking of immunocompetent donor T-lymphocytes and may have a role in preventing GI aGvHD. Here we present the 6-month results of a phase 1b study of the safety, tolerability and clinical activity of vedolizumab combined with standard graft-versus-host disease (GvHD) prophylaxis. Methods This is an open-label, dose-finding study of the addition of vedolizumab to standard GvHD prophylaxis in adults undergoing hematopoietic stem cell transplantation (HCT). Cohort 1 comprised subjects aged 18-60 years with a hematologic malignancy undergoing human leukocyte antigen (HLA)-matched or 1 locus-mismatched, unrelated-donor myeloablative transplantation. These subjects received intravenous (IV) vedolizumab (75 mg, on days -1, +13 and +42 of HCT). If subjects in cohort 1 experienced no engraftment failures or dose-limiting toxicities (DLTs), then subsequent subjects were enrolled into a dose-expansion cohort of IV vedolizumab 300 mg (cohort 2), following the same schedule. Key inclusion criteria for cohort 2 were myeloablative regimens (subjects aged 18-60 years) or reduced-intensity conditioning regimens (subjects aged 18-75 years), donor-recipient pairs who were HLA-matched or 1-locus mismatched, and subjects receiving peripheral blood- or bone-marrow-derived stem cells. All subjects received standard GvHD prophylaxis (tacrolimus and methotrexate). The primary objective was to identify an efficacious vedolizumab dose with an acceptable safety profile for future studies, using the following primary safety endpoints: frequency of DLTs from day -1 to day 28, and the number of patients experiencing treatment-emergent adverse events (TEAEs) and serious adverse events from administration of the first dose of vedolizumab until 18 weeks after the final dose. Secondary endpoints included time to neutrophil engraftment, cumulative incidence of grade II-IV aGvHD and frequency by maximum severity of aGvHD by modified Glucksberg criteria. Exploratory endpoints included overall survival (OS) and aGvHD-free survival. Results In total, 24 subjects were enrolled at 5 centers (3 in cohort 1, then 21 in cohort 2). The median age was 55 years (range 18-72 years). Most subjects underwent an unrelated donor HCT (83%), and all except 1 were HLA-matched (Table 1). At 6 months after HCT, no DLTs were observed in either cohort. All subjects engrafted within 28 days; the median time to neutrophil engraftment was 14 days in cohort 2. All subjects experienced at least 1 TEAE, which was serious in 13 subjects (2 in cohort 1, 11 in cohort 2). TEAEs were considered vedolizumab-related in 2 subjects in cohort 1 and 6 in cohort 2, including 1 subject in cohort 2 who experienced 2 serious TEAEs: hypotension and febrile neutropenia. The most frequent infections were cytomegalovirus (4 cases) and Clostridium difficile colitis (3 cases). No adverse events led to discontinuation of vedolizumab. There were no cases of grade II-IV aGvHD at 6 months after HCT in cohort 1. In cohort 2, 4 subjects (19%) developed grade II-IV aGvHD at 6 months after HCT; 3 (14%) grade II (1 skin only involvement, 2 skin and lower GI involvement) and 1 (5%) grade III (liver, skin and lower GI involvement). All cases of lower GI aGvHD were limited to stage 1 disease. At 6 months after HCT, 1 subject died from disease relapse in cohort 1, and 2 subjects died in cohort 2; 1 from disease relapse and 1 from aGvHD-related complications. Among subjects in cohort 2, 6-month OS and non-relapse mortality were 90% and 5%, respectively, and grade II-IV and grade III-IV aGvHD-free survival were 76% and 90%, respectively (Table 2). Conclusions In subjects receiving vedolizumab in addition to standard GvHD prophylaxis, there were no DLTs or engraftment failures at 6 months after HCT, and the TEAEs observed have been as expected in this population. The low cumulative incidences of grade II-IV and grade III-IV aGvHD are promising; there were no cases of lower GI aGvHD greater than stage 1. Intravenous vedolizumab 300 mg added to standard GvHD prophylaxis for the prevention of GI aGvHD merits further study. Disclosures Chen: Takeda Pharmaceuticals: Consultancy; Incyte: Consultancy, Membership on an entity's Board of Directors or advisory committees; Magenta Therapeutics: Consultancy; REGiMMUNE: Consultancy. Shah:Lentigen Technology: Research Funding; Oncosec: Equity Ownership; Exelexis: Equity Ownership; Miltenyi: Other: Travel funding, Research Funding; Juno Pharmaceuticals: Honoraria; Geron: Equity Ownership. Jansson:Takeda Pharmaceuticals: Employment. Akbari:Takeda Pharmaceuticals: Employment. Chen:Takeda Pharmaceuticals: Employment. Quadri:Takeda Pharmaceuticals: Employment. Parfionovas:Takeda Pharmaceuticals: Employment. Devine:Kiadis Pharma: Consultancy.

Background The outcomes of older adults with acute lymphoblastic leukemia (ALL) remain poor when compared to younger ALL patients [PMID 19897583, 28419558, 22409379, 10653870]. Asparaginase (Asp) induces death of human lymphoblasts, and effective asparagine depletion is associated with improved outcomes in ALL. PEG-Asparaginase (PEG-Asp), which has a longer half-life than Asp, is a key component of the intensive chemotherapeutic regimens utilized for treatment of pediatric and younger adult ALL [PMID 29450465]. Frequently, older patients with Ph-negative ALL are not offered PEG-Asp containing pediatric chemotherapy regimen because of concerns related to tolerability and safety in this population [PMID 28355969]. Methods The Adult Leukemia Program at Mount Sinai Hospital developed an age-based, dose-adjusted, CALGB 10403 based intensive chemotherapy regimen for adults (≥40 years) with a diagnosis of Ph-negative ALL. For patients up to 60 years, prednisone (PRD) dose was reduced from 60 to 40 mg/m2/day from D1 to D28, and PEG-Asp reduced from 2500 to 1000 units/m2 (D4). For patients aged 61 years and above, PRD was further reduced to 25 mg/m2/day, and PEG-Asp to 1000 units/m2 on D4. In CD20+ ALL, rituximab x 8 doses were added to the regimen. CNS-prophylaxis consisted of intrathecal methotrexate at D1, D8 and D29 during induction, and during subsequent courses of chemotherapy based on the CALGB 10403 protocol. A PEG-Asp oriented supportive care plan was developed to prevent and treat Asp-related adverse effects. After the administration of PEG-Asp, Antithrombin III (ATIII) and fibrinogen levels were monitored on the same day, twice a week, for at least two weeks. If ATIII levels were < 70% and/or fibrinogen levels < 120 mg/dL, levels were corrected with the administration of ATIII concentrate and/or cryoprecipitate, respectively. Results Twelve patients with a median age of 58 years (45 - 76) were evaluable, and three patients were ≥ 70 years. Nine patients had B-cell ALL and three T-cell ALL. Three patients had a white blood cell count > 30 x103/µL at diagnosis. An ECOG status ≤ 2 at diagnosis was described in all patients, and all of them had multiple complex cytogenetic and molecular abnormalities. Ten patients had significant co-morbidities at diagnosis, including diabetes, hypertension, previous history of cancer, coronary artery disease, obesity, alcohol related chronic pancreatitis, and chronic diarrhea. Nine out of the twelve patients (75%) attained a bone marrow morphological complete remission (CR) at the end of induction (EOI), three of them with detectable minimal residual disease (MRD) that became undetectable after completing course II. Of the three patients who had ≥5% bone marrow blasts at EOI, one attained a CR with undetectable MRD at the end of course IA and another when switched to blinatumomab, and the third one died of progressive disease. No patient experienced early death. Five patients underwent allogeneic hematopoietic stem cell transplantation (HCT) while in CR (age range 46 to 60 years) and four remain in CR at last follow up (median 489 days, range 181 - 841), and one died of relapsed disease 67 days post-HCT. The other six patients who are receiving chemotherapy are alive and in remission at last follow up (median 272 days, range 52 - 639). The common adverse effects associated with PEG-Asp administration in this older group of patients were asymptomatic hypofibrinogenemia and depleted ATIII levels requiring supplementation (n=8), severe hyperbilirubinemia (n=1), and non-life-threatening venous thrombosis (n=1). Severe allergic reaction, clinical pancreatitis and cognitive impairment were not observed. Conclusion This age-based dose-adjusted PEG-Asp containing regimen was associated with an encouraging CR rate and a tolerable and manageable adverse event profile in this older patient population with significant co-morbidities. Treatment related mortality was 0%. Ten of 12 patients are currently in sustained remission, either with chemotherapy alone or following allogeneic HCT (median follow up 422 days, range 52 to 841 days). Treatment optimization for older patients with ALL utilizing an intensified, age-adjusted PEG-Asp containing induction and consolidation therapy regimen is associated with favorable outcomes and provides an effective bridge to potentially curative therapies such as HCT. Further prospective evaluation is under way. Table. Table. Disclosures Kremyanskaya: Incyte: Research Funding. Mascarenhas:Incyte: Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Research Funding; Promedior: Research Funding; Janssen: Research Funding; Celgene: Membership on an entity's Board of Directors or advisory committees; Merck: Research Funding; CTI Biopharma: Membership on an entity's Board of Directors or advisory committees, Research Funding; Roche: Research Funding.

[Figure][1] A 25-year-old woman with FLT3-ITD positive acute myeloid leukemia underwent cord blood transplantation with fludarabine, cyclophosphamide, and total body irradiation conditioning. Despite prophylaxis with mycophenolate and tacrolimus, she suffered from grade 4 gastrointestinal

Introduction: Amphiregulin (AREG) is an epidermal growth factor receptor (EGFR) ligand that can restore integrity to damaged intestinal mucosa in murine models of acute graft-versus-host disease (aGVHD). We previously described AREG as a circulating biomarker of late-onset aGVHD, but its relevance combined with clinical risk factors has not yet been tested in a large cohort of patients with aGVHD occurring prior to day 100 post-transplant. We therefore tested samples from two aGVHD first-line treatment trials, Blood and Marrow Transplant Clinical Trials Network (BMT CTN) 0302 and 0802, and identified a clinically relevant threshold level of circulating AREG at aGVHD onset. We then investigated whether incorporating AREG into the refined Minnesota Risk Score could further risk-stratify patients. Patients and Methods: Blood samples were obtained at the onset of systemic aGVHD treatment within BMT CTN 0302 (serum) and BMT CTN 0802 (plasma). All patients with response data and samples for analysis from both trials were included (N=251). We determined the association of AREG with clinical outcomes, including risk stratification by the refined Minnesota criteria, day 28 complete/partial response (CR/PR) to first-line therapy, 2-year overall survival (OS) and 6-month and 2-year non-relapse mortality (NRM). We investigated the effect of AREG on clinical endpoints per a doubling in the value of AREG, defined a clinically relevant threshold level in the AREG values using two-fold cross-validation, and confirmed the clinical relevance of this cut-point in independent samples (N=92) from pooled from drawn from the Chronic GVHD Consortium and the Mount Sinai Acute GVHD International Consortium (MAGIC). Results: In patients enrolled in BMT CTN 0302/0802, AREG levels were 1.7-fold higher in patients with Minnesota high-risk (HR) compared to standard-risk (SR) aGVHD (HR median 53.4 vs SR 31 pg/ml, p Conclusion: AREG is elevated in patients with poor aGVHD outcomes and adds to the accuracy of risk stratification when combined with the refined Minnesota Risk Score. AREG ≥33 pg/mL at aGVHD onset is associated with lower day 28 CR/PR and higher mortality in samples from 4 multicenter cohorts. The mechanism of elevated circulating AREG in severe aGVHD is not yet known, although we hypothesize the degree of AREG elevation reflects the intensity of immune-mediated tissue injury resulting in AREG release. With accumulating evidence of altered EGFR ligands in aGVHD, further investigation into epithelial repair pathways involving AREG may lead to new adjunctive therapies to overcome poor steroid response in high-risk aGVHD. Disclosures Holtan: Incyte: Other: One-time advisory board member. Khera: Novartis: Consultancy. Lee: Mallinckrodt: Honoraria; Amgen: Other: One-time advisory board member; Bristol-Myers-Squibb: Other: One-time advisory board member; Kadmon: Other: One-time advisory board member. Chen: Immudex: Research Funding. Arora: Takeda Oncology: Consultancy. Flowers: Pharmacyclics: Consultancy. Cutler: Pfizer: Consultancy; Kite: Consultancy; Incyte: Consultancy; Bristol-Myers Squibb: Consultancy; Pharmacyclics: Consultancy; Astellas: Consultancy. Jagasia: Janssen: Consultancy, Research Funding; Therakos: Consultancy, Research Funding; Mallinckrodt: Consultancy. Hexner: Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding. Levine: Novartis Pharmaceuticals Corporation: Membership on an entity's Board of Directors or advisory committees. MacMillan: Magenta Therapeutics: Research Funding.

Graft-versus-host disease (GVHD), the primary cause of non-relapse mortality (NRM) following allogeneic hematopoietic stem cell transplantation, does not always respond to treatment with high dose systemic corticosteroids. We have recently shown that a combination of three biomarkers (TNFR1, ST2, and REG3α) measured at onset of GVHD can predict day 28 response to treatment and 6-month NRM (Levine, Lancet Haem, 2015). Our goal in the current study was to determine if the same biomarker-based Ann Arbor GVHD algorithm can alsopredict treatment response andmortality whenapplied after one week of systemic corticosteroid treatment. The study population consisted of 378 patients (pts) with acute GVHD from 11 centers in the Mount Sinai Acute GVHD International Consortium. All pts were treated with systemic steroids and provided a plasma or serum sample obtained after one week of treatment (±3 days). The median starting dose of systemic steroids for Grade II-IV GVHD was 2.0 mg/kg/day and for Grade I was 1.0 mg/kg/day, after which treatment varied. Patients were divided into test (n=236) and validation (n=142) cohorts. We applied the Ann Arbor GVHD algorithm to concentrations of TNFR1, ST2, and REG3α measured after one week of treatment to generate a predicted probability of 6-month NRM, which we term the treatment score (TS). We employed unsupervised k-medoidclustering to partition TS values from the test cohort into two groups (high and low). This unbiased approach identified a high score group made up of 25% of pts (n=58) in the test cohort. We observed that the day 28 response rate (complete, CR + partial, PR) was significantly lower in pts with high scores compared to low scores in the test cohort (24% vs 65%, p Approximately half of the pts in each cohort (test: 48%; validation: 44%) responded (CR+PR) to the first week of steroids and these ptshad significantly lower 6-month NRM than non-responders (NR) (test: 17% vs 36%, p=0.0002; validation: 13% vs 36%, p=0.0014). Yet the TS continued to stratify mortality risk independently of clinical response. In the test cohort, pts with a high score comprised 16% of all early responders and experienced more than twice the NRM of early responders with a low score (33% vs 13%, p=0.022) (Fig 2A). Conversely, test cohort pts who did not respond by day 7, but had a low score, fared much better than non-responders with a high score (NRM 21% vs 68%, p In conclusion, a treatment score based on three GVHD biomarkers measured after one week of steroids stratifies pts into two groups with distinct risks for treatment failure and 6-month NRM. It is particularly noteworthy that the TS identifies two subsets of pts with steroid refractory (SR) GVHD who have highly different outcomes (Fig 2B/D). The much larger group, approximately two thirds of all SR pts, may not need the same degree of treatment escalation as is traditional for clinical non-response, and thus overtreatment might be avoided. Because the TSis measured at a common decision making time point, it may prove useful to guide risk-adapted therapy. Disclosures Mielke: Novartis: Consultancy; MSD: Consultancy, Other: Travel grants; Celgene: Other: Travel grants, Speakers Bureau; Gilead: Other: Travel grants; JAZZ Pharma: Speakers Bureau. Kroeger:Novartis: Honoraria, Research Funding. Chen:Incyte Corporation: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Research Funding. Jagasia:Therakos: Consultancy. Kitko:Therakos: Honoraria, Speakers Bureau. Ferrara:Viracor: Patents & Royalties: GVHD biomarker patent. Levine:Viracor: Patents & Royalties: GVHD biomarker patent.

No laboratory test can predict non-relapse mortality (NRM) after hematopoietic cellular transplantation (HCT) prior to the onset graft-versus-host disease (GVHD). Recently, we have shown that a signature of three GVHD plasma biomarkers (TNFR1, ST2, and REG3α) can predict response to GVHD therapy and NRM at the onset of clinical GVHD (Levine, Lancet Haem, 2015). Our goal in the current study was to identify a blood biomarker signature that could predict lethal GVHD and six-month NRM well in advance of the onset of GVHD symptoms. Patient samples on day +7 after HCT were obtained from 1,287 patients from 11 HCT centers in the Mount Sinai Acute GVHD International Consortium (MAGIC). Samples from two large centers (n = 929) were combined and randomly assigned to a training set (n = 620) and test set (n = 309). 358 patients from nine others centers constituted an independent validation set. The overall cumulative incidences of 6-month NRM were 11%, 12%, and 13% for the training, test, and validation sets respectively. The incidence of lethal GVHD, defined as death without preceding relapse while under steroid treatment for acute GVHD, were 18%, 24%, and 14% in the same groups, respectively. The median day of GVHD onset was 28 days in the training set and 29 days in the test and validation sets. We measured four GVHD related biomarkers [ST2, REG3α, TNFR1, and IL2Rα] in all samples and used the training set alone to develop competing risks regression models that used all 13 possible combinations of one to four biomarkers to predict 6-month NRM. The best algorithm, which we rigorously confirmed through Monte Carlo cross-validation of 75 different combinations of training sets, included ST2 and REG3α. No combination of one, three, or four biomarkers was superior to the combination of these two biomarkers. The day 7 algorithm identified high risk (HR) and low risk (LR) groups with 6-month NRMs of 28% and 7%, respectively (p In conclusion, we have developed a blood biomarker algorithm that predicts the development of lethal GVHD seven days after HCT, which performed successfully in large multicenter validation sets. The GVH reaction is already in progress by day +7, even though clinical symptoms may not occur until days or weeks later. We speculate that the blood biomarker concentrations at this early time point reflect subclinical GI pathology, a notion that is reinforced by the fact that ST2 and REG3α, the two biomarkers in the algorithm, are closely associated with GI GVHD. The algorithm identified HR and LR strata in several patient groups with different overall risk for lethal GVHD (donor, HLA match, conditioning regimen intensity, age). This day +7 algorithm should prove useful in clinical BMT research by identifying patients at high risk for lethal GVHD who might benefit from aggressive preemptive treatment strategies. Disclosures Chen: Novartis: Research Funding; Incyte Corporation: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding. Jagasia:Therakos: Consultancy. Kitko:Therakos: Honoraria, Speakers Bureau. Kroeger:Novartis: Honoraria, Research Funding. Levine:Viracor: Patents & Royalties: GVHD biomarkers patent. Ferrara:Viracor: Patents & Royalties: GVHD biomarkers patent.

Clinical GVHD staging varies between centers and is not agreed upon by independent reviewers (Weisdorf, BBMT 2003). These inconsistencies help explain why promising GVHD treatments from single center studies have not reproduced in multicenter trials. To address this issue, our international GVHD research consortium has developed guidance that has been refined through consensus following case discussions, resulting in uniform and reproducible GVHD clinical symptom reporting. We record all raw target organ symptom data and apply staging based upon this data (Table 1). Only areas of erythema, bullae and desquamation are quantified because other skin changes are not typical of active GVHD rash. Upper GI symptoms must meet thresholds to diagnose GVHD: anorexia with associated weight loss, nausea and/or 2+ vomiting episodes/day lasting 3+ days. For lower GI GVHD we collect stool volumes excluding formed/mostly-formed stools. Unquantified episodes are counted at 200 ml per episode (3 ml/kg for children We classify biopsy report interpretation into four standardized categories: Positive (unequivocal presence of GVHD), Equivocal (findings suggestive of GVHD, but the pathologist cannot confirm the diagnosis), Non-diagnostic (no abnormalities or subtle findings insufficient to determine etiology), and Non-GVHD etiology (definitive evidence of another diagnosis without concomitant features suggestive of GVHD). We then combine the biopsy interpretation with clinical decision making to assign an overall confidence level to the diagnosis of GVHD in each target organ (Table 2): Confirmed (positive biopsy, regardless of clinician treatment decision), Probable (GVHD diagnosis is sufficiently favored that treatment is given without a positive biopsy), Possible (symptoms present without a positive biopsy; not treated as GVHD), Negative (no symptoms or symptoms are present but a GVHD diagnosis is not entertained and a non-GVHD etiology is identified). Uniform clinical data collection is essential for future GVHD trials and requires application of clear guidance. While still subject to refinement, these guidelines, in use for 2 years by an international research consortium, are designed to be clear, easy to apply, and for clinical trial use. Table 1. GVHD Target Organ Staging Stage Skin (active erythema only) Liver (bilirubin) Upper GI Lower GI (stool output/day) 0 No active (erythematous) GVHD rash < 2 mg/dl No or intermittent nausea, vomiting or anorexia Adult: < 500 ml/day or 50% BSA 6.1-15 mg/dl - Adult: >1500 ml/day or >7 episodes/day Child: > 30 ml/kg/day or >10 episodes/day 4 Generalized rash (>50% BSA) and bullous formation or desquamation > 5% BSA >15 mg/dl - Severe abdominal pain with or without ileus, or grossly bloody stool (volume independent) Table 2. Confidence Levels Pathologic evidence Clinician assessment Treatment for acute GVHD Comments Confirmed Unequivocal evidence of GVHD GVHD is the etiology for symptoms Not required GVHD is clearly present even if other etiologies co-exist simultaneously Probable Not required (includes equivocal and non-diagnostic biopsies) GVHD most likely etiology for symptoms Yes GVHD is most likely present but other etiologies may also explain the symptoms and there insufficient evidence to make a confirmed diagnosis Possible GVHD in differential diagnosis (but no treatment is being provided) No GVHD may be present, but other etiologies are favored Negative Unequivocal evidence of a diagnosis other than GVHD (e.g., drug rash) GVHD is not considered as an explanation for the symptoms No and the symptoms resolve without GVHD treatment A "negative" biopsy (e.g., normal skin) is not unequivocal evidence of a diagnosis other than GVHD Disclosures Devine: Genzyme: Research Funding. Chen:Bayer: Consultancy, Research Funding. Porter:Novartis: Patents & Royalties, Research Funding. Levine:Novartis: Consultancy.