Santoro, Armando

Background. Study of myeloid neoplasms (MN) has been rapidly transformed by genome characterization. Gene mutations have been reported to influence disease phenotype and risk of disease progression, and the evaluation of mutational status can provide valuable insights to improve the decision-making process. In this international study, we evaluated the clinical impact of mutational screening in patients with CMML, which is characterized by significant clinical and genomic heterogeneity, including a substantial proportion of patients with poor outcomes and unmet needs. Currently, only limited molecular information has been incorporated into CMML classification and prognostication. Methods. We retrospectively collected 3182 CMML patients. We used MOSAIC, an AI-based framework for multimodal analysis in rare cancers (PMID: 38875514) to develop innovative, molecular-based tools for classification and prognostication. An independent validation of the results on 516 prospectively collected patients was performed. Results. Bayesian Networs and Hierarchical Dirichlet Processes were used to identify genomic associations and define a CMML molecular classification. We identified 11 clusters with distinct clinical and genomic features, including splicing machinery, signal transduction and tyrosine kinase pathways aberrations, and high-risk molecular signatures (i.e., AML-like and TP53 mutations). Up to 15% of patients showed clear genomic overlap with other MN. Importantly, extensive multi-color flow cytometry on T lymphocytes, NK and myeloid cells (BD FACSymphony A5 Cell Analyzer) revealed specific immunologic and inflammation signatures associated with molecular subgroups. We then integrated molecular and clinical information to build an international CMML Prognostic Scoring System (iCPSS). We assessed the performance of different statistical and AI-based methods; L1-penalized Cox Model resulted as the best performing method. Selected features included hematological parameters (WBC, Hb, PLT and marrow blasts), cytogenetic abnormalities, and mutations in 10 genes (ASXL1, DNMT3A, EZH2, NRAS, RUNX1, SETBP1, STAG2, TET2, TP53, U2AF1). By Bayesian thresholds optimization, we identified 5 risk classes (i.e., very-low, low, intermediate, high and very-high) with median overall survival (OS) ranging from 99 to 9 months (P<.001), and median leukemia-free survival (LFS) ranging from 210 to 18 months (P<.001). iCPSS provided better patient discrimination across all clinical endpoints compared to currently available prognostic tools, with a Concordance Index (CI) for OS of 0.75 versus 0.62-0.64, respectively. Notably, compared to available scoring systems, up to 40% of patients were reassigned to higher or lower risk classes by the iCPSS. External validation on an independent prospective cohort confirmed that the performance of iCPSS is superior to existing prognostic models (CI for OS 0.71 vs 0.54-0.61, respectively) To demonstrate the clinical utility of iCPSS, we focused on 753 patients who underwent allogeneic stem cell transplantation (HSCT). In multivariable analysis, iCPSS stratified the probability of OS post-HSCT (P<.001) and identified groups of patients with different probabilities of disease relapse, ranging from 9% to 62% (P<.001). We employed a clinical- and genomic-based decision support system (PMID: 38723212) to determine the optimal timing of HSCT. Preliminary analyses indicated that higher-risk patients according to iCPSS (i.e., intermediate, high, and very high) benefit from an immediate HSCT strategy. Lower-risk patients (i.e., very low and low) had life expectancy maximized with delayed HSCT. Modeling decision analysis using iCPSS compared to conventional scores, resulted in a change in transplantation policy for a significant proportion of patients (up to 25%). Conclusion. Molecular information significantly improves the classification of CMML patients, providing a basis for refining diagnostic boundaries with other MN and for a more rational inclusion of patients in clinical trials. The iCPSS demonstrated superior performance over currently available scoring systems and improved HSCT decision making process.

Abstract Patients with relapsed/refractory (R/R) classical Hodgkin lymphoma (cHL) for whom autologous hematopoietic cell transplantation (auto-HCT) had failed experienced frequent and durable responses to nivolumab in the phase 2 CheckMate 205 trial. We present updated results (median follow-up, ∼5 years). Patients with R/R cHL who were brentuximab vedotin (BV)–naive (cohort A), received BV after auto-HCT (cohort B), or received BV before and/or after auto-HCT (cohort C) were administered with nivolumab 3 mg/kg IV every 2 weeks until progression or unacceptable toxicity. Patients in cohort C with complete remission (CR) for 1 year could discontinue nivolumab and resume upon relapse. Among 243 patients (cohort A, n = 63; B, n = 80; and C, n = 100), the objective response rate (ORR) was 71.2% (95% confidence interval [CI], 65.1-76.8); the CR rate was 21.4% (95% CI, 16.4-27.1). Median duration of response, CR, and partial remission were 18.2 (95% CI, 14.7-26.1), 30.3, and 13.5 months, respectively. Median progression-free survival was 15.1 months (95% CI, 11.3-18.5). Median overall survival (OS) was not reached; OS at 5 years was 71.4% (95% CI, 64.8-77.1). In cohort C, all 3 patients who discontinued in CR and were subsequently re-treated achieved objective response. No new or unexpected safety signals were identified. This 5-year follow-up of CheckMate 205 demonstrated favorable OS and confirmed efficacy and safety of nivolumab in R/R cHL after auto-HCT failure. Results suggest patients may discontinue treatment after persistent CR and reinitiate upon progression. This trial was registered at www.clinicaltrials.gov as #NCT02181713.

PURPOSE This randomized, open-label trial compared the efficacy and safety of adjuvant nab-paclitaxel + gemcitabine with those of gemcitabine for resected pancreatic ductal adenocarcinoma (ClinicalTrials.gov identifier: NCT01964430 ). METHODS We assigned 866 treatment-naive patients with pancreatic ductal adenocarcinoma to nab-paclitaxel (125 mg/m 2 ) + gemcitabine (1,000 mg/m 2 ) or gemcitabine alone to one 30-40 infusion on days 1, 8, and 15 of six 28-day cycles. The primary end point was independently assessed disease-free survival (DFS). Additional end points included investigator-assessed DFS, overall survival (OS), and safety. RESULTS Two hundred eighty-seven of 432 patients and 310 of 434 patients completed nab-paclitaxel + gemcitabine and gemcitabine treatment, respectively. At primary data cutoff (December 31, 2018; median follow-up, 38.5 [interquartile range [IQR], 33.8-43 months), the median independently assessed DFS was 19.4 ( nab-paclitaxel + gemcitabine) versus 18.8 months (gemcitabine; hazard ratio [HR], 0.88; 95% CI, 0.729 to 1.063; P = .18). The median investigator-assessed DFS was 16.6 (IQR, 8.4-47.0) and 13.7 (IQR, 8.3-44.1) months, respectively (HR, 0.82; 95% CI, 0.694 to 0.965; P = .02). The median OS (427 events; 68% mature) was 40.5 (IQR, 20.7 to not reached) and 36.2 (IQR, 17.7-53.3) months, respectively (HR, 0.82; 95% CI, 0.680 to 0.996; P = .045). At a 16-month follow-up (cutoff, April 3, 2020; median follow-up, 51.4 months [IQR, 47.0-57.0]), the median OS (511 events; 81% mature) was 41.8 ( nab-paclitaxel + gemcitabine) versus 37.7 months (gemcitabine; HR, 0.82; 95% CI, 0.687 to 0.973; P = .0232). At the 5-year follow-up (cutoff, April 9, 2021; median follow-up, 63.2 months [IQR, 60.1-68.7]), the median OS (555 events; 88% mature) was 41.8 versus 37.7 months, respectively (HR, 0.80; 95% CI, 0.678 to 0.947; P = .0091). Eighty-six percent ( nab-paclitaxel + gemcitabine) and 68% (gemcitabine) of patients experienced grade ≥ 3 treatment-emergent adverse events. Two patients per study arm died of treatment-emergent adverse events. CONCLUSION The primary end point (independently assessed DFS) was not met despite favorable OS seen with nab-paclitaxel + gemcitabine.

AbstractBackgroundStudies suggest that immune checkpoint inhibitors may represent a promising strategy for boosting immune responses and improving the antitumor activity of standard therapies in patients with relapsed/refractory hematologic malignancies.AimsPhase 1/2 FUSION NHL 001 was designed to determine the safety and efficacy of durvalumab, an anti‐programmed death ligand 1 (PD‐L1) antibody, combined with standard‐of‐care therapies for lymphoma or chronic lymphocytic leukemia (CLL).Methods and ResultsThe primary endpoints were to determine the recommended phase 2 dose of the drugs used in combination with durvalumab (durvalumab was administered at the previously recommended dose of 1500 mg every 4 weeks) and to assess safety and tolerability. Patients were enrolled into one of four arms: durvalumab monotherapy (Arm D) or durvalumab in combination with lenalidomide ± rituximab (Arm A), ibrutinib (Arm B), or rituximab ± bendamustine (Arm C). A total of 106 patients with relapsed/refractory lymphoma were enrolled. All but two patients experienced at least one treatment‐emergent adverse event (TEAE); those not experiencing a TEAE were in Arm C (diffuse large B‐cell lymphoma [DLBCL]) and Arm D (DLBCL during the durvalumab monotherapy treatment period). No new safety signals were identified, and TEAEs were consistent with the respective safety profiles for each study treatment. Across the study, patients with follicular lymphoma (FL; n = 23) had an overall response rate (ORR) of 59%; ORR among DLBCL patients (n = 37) was 18%. Exploratory biomarker analysis showed that response to durvalumab monotherapy or combination therapy was associated with higher interferon‐γ signature scores in patients with FL (p = .02).ConclusionDurvalumab as monotherapy or in combination is tolerable but requires close monitoring. The high rate of TEAEs during this study may reflect on the difficulty in combining durvalumab with full doses of other agents. Durvalumab alone or in combination appeared to add limited benefit to therapy.

AbstractThe multicenter, phase Ib CC‐122‐DLBCL‐001 dose‐expansion study (NCT02031419) explored the cereblon E3 ligase modulator (CELMoD) agent avadomide (CC‐122) plus rituximab in patients with relapsed/refractory (R/R) diffuse large B‐cell lymphoma (DLBCL) or follicular lymphoma (FL). Patients received avadomide 3 mg/day 5 days on/2 days off plus rituximab 375 mg/m2 on day 8 of cycle 1, day 1 of cycles 2 through 6, and day 1 of every third subsequent cycle for 2 years. Primary endpoints were safety and tolerability; preliminary efficacy was a secondary endpoint. A total of 68 patients were enrolled (DLBCL [n = 27], FL [n = 41; 31 lenalidomide‐naïve, 10 lenalidomide‐treated]). Median age was 62 years (range, 33–84 years), and patients had received a median of 3 (range, 1–8) prior regimens. Among patients with DLBCL, 66.7% had primary refractory disease (partial response or less to initial therapy). Among patients with FL, 65.9% were rituximab‐refractory at study entry and 10.0% were lenalidomide‐refractory. The most common any‐grade avadomide‐related adverse events (AEs) were neutropenia (63.2%), infections/infestations (23.5%), fatigue (22.1%), and diarrhea (19.1%). The most common grade 3/4 avadomide‐related AEs were neutropenia (55.9%) infections/infestations (8.8%), and febrile neutropenia (7.4%). In patients with DLBCL, overall response rate (ORR) was 40.7% and median duration of response (mDOR) was 8.0 months. In patients with FL, ORR was 80.5% and mDOR was 27.6 months; response rates were similar in lenalidomide‐naïve and ‐treated patients. Avadomide plus rituximab was well tolerated, and preliminary antitumor activity was observed in patients with R/R DLBCL and FL, including subgroups with typically poor outcomes. These results support further investigation of novel CELMoD agents in combination with rituximab in R/R DLBCL and FL.

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

Abstract Introduction: The phase 2 CheckMate 205 study (NCT02181738) of nivolumab (nivo) has demonstrated high objective response rates, durable efficacy, and acceptable safety profiles in patients (pts) with relapsed/refractory classical Hodgkin lymphoma (R/R cHL) after failure of autologous hematopoietic cell transplantation (auto-HCT) regardless of prior brentuximab vedotin (BV) treatment (Younes A et al. Lancet Oncol 2016; Fanale M et al. ICML 2017 [Oral 125]). Recently proposed new response criteria aim to account for atypical patterns of response with checkpoint inhibitors which may not be fully captured by conventional response criteria (Cheson BD et al. Blood 2016; Younes A et al, Ann Oncol 2017). Studies in solid tumors have shown that pts may continue to derive clinical benefits from nivo beyond disease progression as defined by conventional criteria (George S et al, JAMA Oncol 2016; Long GV et al, JAMA Oncol 2017). Here we report outcomes among pts with R/R cHL treated beyond progression (TBP) in CheckMate 205. Methods: This single-arm, multicenter study enrolled pts (age ≥18 y) with R/R cHL after failure of auto-HCT into 3 independent cohorts (A: BV naïve, B: BV after auto-HCT, C: BV before and/or after auto-HCT). Nivo 3 mg/kg IV every 2 wk was given until disease progression or unacceptable toxicity. Response was assessed by 2007 International Working Group criteria. Best overall response (BOR) was assessed per investigator. A protocol amendment in July 2014 allowed pts to be TBP (investigator-assessed) if they met prespecified criteria, including deriving clinical benefit, stable performance status, and non-rapid progression. Pts TBP were required to discontinue in the event of further progression (≥10% increase in tumor burden). Tumor burden after initial progression was assessed in a prespecified analysis. Exploratory analyses assessed overall survival (OS) and time to next therapy (TTNT) in pts TBP. Results: In total, 70/243 (29%) pts were TBP: 19 in Cohort A, 23 in B, and 28 in C. Demographics were similar to the overall study population: 57% had stage IV disease at study entry, median (range) age was 37 (18-72) y, and median number of prior therapies was 3 (2-5). BOR prior to progression was complete remission (CR) in 5 (7%) pts, partial remission (PR) in 31 (44%), stable disease (SD) in 20 (29%), and progressive disease in 13 (19%) (BOR was non-evaluable in 1 pt). Among pts TBP, the initial cause of progression was a ≥50% increase in total tumor burden in 13 (19%) pts, non-target lesion progression in 17 (24%), and new lesions in 47 (67%) (pts could have multiple findings as reasons for progression). The median time to initial progression in pts TBP was 6 mo; 11 mo in pts with initial BOR of CR and 7 mo in pts with initial PR or SD. At December 2016 database lock, median (range) doses of nivo beyond progression were 8 (1-43), and median duration of treatment beyond progression was 5 (0-19) mo. Overall, 21 (30%) pts TBP remained on treatment; the most common reason for discontinuation was further disease progression (80%). The majority of pts TBP demonstrated stable reductions in tumor burden with continued treatment. Median (95% CI) TTNT from first study dose of nivo was 17 (14, not estimable) mo (Figure). Median OS from date of initial progression was not reached in pts TBP and OS was 84% (95% CI 70, 92) at 1 y. Treatment-related adverse events (TRAEs) occurred in 46% of pts (13% grade [G] 3-4) after progression, vs 64% (9% G3-4) prior to progression. Serious TRAEs after progression were aspartate aminotransferase increase (n=1) and hypercalcemia (n=1), both G3-4. Ten deaths occurred in pts TBP; 7 were due to disease progression and none were considered related to study drug. Conclusions: In total, 29% of pts from CheckMate 205 Cohort A/B/C were TBP. New lesions were the most common reason for initial progression in pts TBP. Stable reductions in tumor burden were seen with continued treatment in pts TBP, and median TTNT and OS remained high. Proposed updates to response criteria may help to better assess the long-term efficacy of checkpoint inhibitors. These data suggest that pts considered to show stable performance status, non-rapid progression, and clinical benefits despite progression according to conventional response criteria may derive long-term benefits from continued nivo treatment. Study funding: BMS. Writing support: Simon Wigfield, Caudex, funded by BMS. Disclosures Cohen: Bioinvent: Consultancy, Membership on an entity's Board of Directors or advisory committees; Genentech: Consultancy, Membership on an entity's Board of Directors or advisory committees; Takada: Research Funding; Bristol Myers Squibb: Research Funding; Abbvie: Consultancy, Membership on an entity's Board of Directors or advisory committees; Infinity: Consultancy, Membership on an entity's Board of Directors or advisory committees; Janssen: Consultancy, Membership on an entity's Board of Directors or advisory committees; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; LAM Therapeutics, Inc: Research Funding. Engert: Amgen: Honoraria, Research Funding; Bristol-Myers Squibb: Consultancy, Honoraria, Research Funding; Takeda: Consultancy, Honoraria, Research Funding; Affimed: Consultancy, Honoraria, Research Funding. Ansell: Merck: Research Funding; Celldex: Research Funding; Seattle Genetics: Research Funding; Bristol-Myers Squibb: Research Funding; Affimed: Research Funding. Younes: Roche: Consultancy, Honoraria, Other: Third-party medical writing assistance, under the direction of Anas Younes, was provided by Scott Malkin of Gardiner-Caldwell Communications, and was funded by F. Hoffmann-La Roche Ltd.; Bayer: Honoraria; Bristol-Myers Squibb: Honoraria; Novartis: Research Funding; Janssen: Honoraria; Merck: Honoraria; Curis: Research Funding; Sanofi: Honoraria; Takeda Millenium: Honoraria; Johnson & Johnson: Research Funding; Seattle Genetics: Honoraria; Incyte: Honoraria; Celgene: Honoraria. Trneny: Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Gilead: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Roche: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Takeda: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees. Savage: Roche: Research Funding; Seattle Genetics: Consultancy, Honoraria; Bristol-Myers Squibb: Honoraria; Merck: Honoraria; Celgene: Consultancy. Ramchandren: Seattle Genetics: Consultancy; Janssen: Research Funding; Merck: Research Funding; Pharmacyclics: Research Funding. Collins: ADC Therapeutics: Research Funding; Roche: Consultancy, Honoraria, Speakers Bureau; Pfizer: Consultancy, Honoraria; Celgene: Research Funding; Celleron: Consultancy; MSD: Consultancy, Honoraria; Takeda: Consultancy, Honoraria, Speakers Bureau; Bristol-Myers Squibb: Research Funding; Amgen: Research Funding. Fanale: AMGEN: Membership on an entity's Board of Directors or advisory committees; CELGENE: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; TAKEDA: Honoraria, Research Funding; ONYX: Research Funding; SEATTLE GENETICS: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; MOLECULAR TEMPLATES: Research Funding; MERCK: Membership on an entity's Board of Directors or advisory committees, Research Funding; BMS: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; GENENTECH: Research Funding; ADC THERAPEUTICS: Research Funding. Armand: Bristol-Myers Squibb: Consultancy, Other: research funding (institutional); Merck: Consultancy, Other: research funding (institutional); Infinity: Consultancy; Pfizer: Consultancy, Other: research funding (institutional); Affimed: Other: research funding (institutional); Otsuka: Other: research funding (institutional); Sequenta: Other: research funding (institutional); Sigma Tau: Other: research funding (institutional); Roche: Other: research funding (institutional); Tensha: Other: research funding (institutional). Zinzani: Bayer: Honoraria, Membership on an entity's Board of Directors or advisory committees; Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees; Gilead: Honoraria, Membership on an entity's Board of Directors or advisory committees; Johnson & Johnson: Honoraria, Membership on an entity's Board of Directors or advisory committees; Bristol-Myers Squibb: Honoraria, Membership on an entity's Board of Directors or advisory committees; Karyopharm Therapeutics: Honoraria, Membership on an entity's Board of Directors or advisory committees; Verastem: Honoraria, Membership on an entity's Board of Directors or advisory committees; Merck: Honoraria, Membership on an entity's Board of Directors or advisory committees; Servier: Honoraria, Membership on an entity's Board of Directors or advisory committees; Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees. De Boer: Bristol-Myers Squibb: Membership on an entity's Board of Directors or advisory committees; MSD: Membership on an entity's Board of Directors or advisory committees; Merck: Membership on an entity's Board of Directors or advisory committees, Other: Non-restricted grant for research in head and neck cancer; Eisai: Membership on an entity's Board of Directors or advisory committees; Astellas: Other: member of Independent Data Monitoring Committee. Shipp: Cell Signaling: Honoraria; Bristol-Myers Squibb: Membership on an entity's Board of Directors or advisory committees, Research Funding; Bayer: Research Funding; Takeda: Other: Scientific Advisory Board; Merck: Other: Scientific Advisory Board; Gilead: Other: Scientific Advisory Board; AstraZeneca: Honoraria. Santoro: Merck: Membership on an entity's Board of Directors or advisory committees; Bristol-Myers Squibb: Membership on an entity's Board of Directors or advisory committees. Timmerman: Seattle Genetics: Consultancy; Celgene: Consultancy; Bristol-Myers Squibb: Consultancy, Honoraria, Other: Travel expenses, Research Funding; Genmab: Consultancy, Equity Ownership; Kite Pharma: Research Funding; ImmuneGene: Research Funding. Sacchi: Bristol-Myers Squibb: Employment. Sy: Bristol-Myers Squibb: Employment. Kuruvilla: BMS: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Gilead: Consultancy, Honoraria; Janssen: Consultancy; Hoffman LaRoche: Consultancy; Seattle Genetics: Consultancy, Honoraria; Amgen: Honoraria; Roche: Honoraria; Janssen: Honoraria; Lundbeck: Honoraria; Merck: Honoraria; Karyopharm: Research Funding; Roche: Research Funding; Celgene: Honoraria, Research Funding.

Introduction: Anti-PD-1 monoclonal antibodies (mAbs) are highly active in relapsed/refractory classical Hodgkin lymphoma (cHL), but most patients (pts) will still relapse. Given this, allogeneic stem cell transplantation (alloHSCT) remains an important option for pts after PD-1 blockade, as it offers the possibility of cure. Prior reports have suggested that alloHSCT after PD-1 mAbs may be associated with severe immune-related complications including acute graft-versus-host disease (GVHD), veno-occlusive disease (VOD) and cytokine release/febrile non-infectious syndrome (CRS). Prior studies of alloHSCT after PD-1 blockade in cHL have been limited by the small number of pts and short follow-up, preventing an accurate assessment of long-term outcomes and complications, risk factors for early toxicity, and the impact of transplant strategies such as choice of GVHD prophylaxis. We therefore assembled a large retrospective international cohort of cHL pts who underwent alloHSCT after PD-(L)1 blockade to better answer these questions, including an assessment of the impact of post-transplant cyclophosphamide (PTCy) on efficacy and toxicity. Methods: Medical records and databases were reviewed at 26 European and United States transplant centers to identify pts with cHL who underwent an alloHSCT any time after receiving a PD-1 or PD-L1 mAb. Response assessment was performed by local investigators according to Lugano 2014 criteria. Overall survival (OS), progression-free survival (PFS), cumulative incidence (CumInc) of relapse (CIR), non-relapse mortality (NRM), acute (a) and chronic (c) GVHD were estimated, as was the association between baseline variables and these outcomes. Results: Between 2014 and 2019, 150 pts were identified who underwent alloHSCT after a median of 10 (range, 1-74) doses of nivolumab (n=118), pembrolizumab (n=31), or avelumab (n=1). The median age was 31 (range 17-68) and pts had received a median of 4 (range, 2-11) lines of therapy prior to PD-(L)1 blockade. 138 pts (92%) had failed BV and 111 (74%) autologous HSCT. The best overall response to PD-(L)1 mAbs was CR for 62 pts (41%), PR for 55 (37%), SD for 17 (11%), PD for 15 (10%) and unknown for 1 (1%). Median time from last dose of PD-(L)1 mAb to alloHSCT was 80 days (range, 17-756) with 70 pts (47%) receiving intervening systemic therapy. At alloHSCT, 90 pts were in CR (60%), 45 in PR (30%), 5 in SD (3%), and 10 in PD (7%). Donors were haploidentical (n=71, 47%), matched sibling (n=29, 19%), matched unrelated (n=39, 26%), mismatched unrelated (n=7, 5%), cord blood (n=2, 1%), or unknown (n=2, 1%). Stem cell source was bone marrow (n=38, 25%), peripheral blood (n=110, 73%), or cord blood (n=2, 1%). GVHD prophylaxis included PTCy in 88 pts (59%) (69/71 (97%) with haploidentical donors; 19/79 (24%) with other donors). With a median post-alloHSCT follow-up for survivors of 23.8 months (range, 1-67), the 2y OS and PFS were 79% (95CI 71-86%) and 65% (95CI 55-73%), respectively, while the 2y CumIncs of relapse and NRM were 21% (95CI 13-29%) and 14%, (95CI, 8-22%), respectively (Fig. 1A-B). 27 pts have died, 3 due to disease and 24 to NRM, including aGVHD (n=7) and VOD (n=2). Veno-occlusive disease (VOD) occurred in 5 pts (day 100 CumInc 4%) and 29 pts (19%) developed CRS (grade 1 n=16; grade 2 n=7; grade 3 n=4; grade 4 n=2). The 6-month CumIncs of grade 2-4, grade 3-4 and grade 4 aGVHD were 39%, 16% and 8%, respectively. Hyperacute GVHD (onset ≤ 14 days after alloHSCT) occurred in 4% of pts and was fatal in 2 pts. The 2y CumInc of cGVHD was 45%. Neither receipt of > 10 doses (median) of anti-PD-(L)1 mAb nor undergoing alloHSCT ≤80 days (median) after last dose of PD-(L)1 mAb were associated with PFS or OS. However, pts with a shorter time to transplant (≤80 days) appeared to have a higher risk of severe (grade 3-4) aGVHD (6m CumInc 24% vs 9%, p=0.006). Recipients of PTCy in this cohort had lower 2y CumIncs of cGVHD (34% vs 58%, p=0.01) and relapse (12% vs 31%, p=0.02), superior 2y PFS (76% vs 54%, p=0.015), and similar rates of severe aGVHD (15% vs 18%, p=0.5), 2y NRM (12% vs 16%, p=0.5), and 2y OS (82% vs 78%, p=0.6). Conclusions: With extended follow-up of a large international cohort, our results argue that alloSCT performed after PD-(L)1 mAbs is a feasible strategy associated with an excellent PFS and a very low CIR for this disease. The use of PT-Cy appears to be associated with improved outcomes and may at present represent the optimal transplant strategy in this pt population. Figure Disclosures Corradini: kite: Honoraria; Abbvie: Honoraria; Servier: Honoraria; Sanofi: Honoraria; Takeda: Honoraria; Roche: Honoraria; Novartis: Honoraria; KiowaKirin: Honoraria; Janssen: Honoraria; Gilead: Honoraria; Daiichi Sankyo: Honoraria; Celgene: Honoraria; Amgen: Honoraria. Ho:Jazz Pharmaceuticals: Research Funding; Jazz Pharmaceuticals: Consultancy; Omeros Corporation: Membership on an entity's Board of Directors or advisory committees. Jaglowski:Kite: Consultancy, Other: advisory board, Research Funding; Novartis: Consultancy, Other: advisory board, Research Funding; Juno: Consultancy, Other: advisory board; Unum Therapeutics Inc.: Research Funding. Herrera:Adaptive Biotechnologies: Consultancy; Bristol-Myers Squibb: Consultancy, Research Funding; Gilead Sciences: Consultancy, Research Funding; Seattle Genetics: Consultancy, Research Funding; AstraZeneca: Research Funding; Merck: Consultancy, Research Funding; Genentech, Inc.: Consultancy, Research Funding; Pharmacyclics: Research Funding; Immune Design: Research Funding; Kite Pharma: Consultancy, Research Funding. Blaise:Jazz Pharmaceuticals: Honoraria; Sanofi: Honoraria; Pierre Fabre medicaments: Honoraria; Molmed: Consultancy, Honoraria. Hamadani:Pharmacyclics: Consultancy; Sanofi Genzyme: Research Funding, Speakers Bureau; Merck: Research Funding; Otsuka: Research Funding; Janssen: Consultancy; Medimmune: Consultancy, Research Funding; ADC Therapeutics: Consultancy, Research Funding; Takeda: Research Funding; Celgene: Consultancy. Ansell:LAM Therapeutics: Research Funding; Affimed: Research Funding; Affimed: Research Funding; Trillium: Research Funding; Trillium: Research Funding; Seattle Genetics: Research Funding; Mayo Clinic Rochester: Employment; Mayo Clinic Rochester: Employment; Bristol-Myers Squibb: Research Funding; Affimed: Research Funding; Mayo Clinic Rochester: Employment; Seattle Genetics: Research Funding; Seattle Genetics: Research Funding; Affimed: Research Funding; LAM Therapeutics: Research Funding; Mayo Clinic Rochester: Employment; Seattle Genetics: Research Funding; LAM Therapeutics: Research Funding; Bristol-Myers Squibb: Research Funding; Mayo Clinic Rochester: Employment; Affimed: Research Funding; Trillium: Research Funding; Trillium: Research Funding; Bristol-Myers Squibb: Research Funding; Regeneron: Research Funding; Affimed: Research Funding; Mayo Clinic Rochester: Employment; Bristol-Myers Squibb: Research Funding; Regeneron: Research Funding; Regeneron: Research Funding; Regeneron: Research Funding; Seattle Genetics: Research Funding; Regeneron: Research Funding; Bristol-Myers Squibb: Research Funding; Seattle Genetics: Research Funding; Seattle Genetics: Research Funding; Seattle Genetics: Research Funding; LAM Therapeutics: Research Funding; Regeneron: Research Funding; Affimed: Research Funding; Regeneron: Research Funding; Bristol-Myers Squibb: Research Funding; Trillium: Research Funding; LAM Therapeutics: Research Funding; Bristol-Myers Squibb: Research Funding; Mayo Clinic Rochester: Employment; Mayo Clinic Rochester: Employment; Regeneron: Research Funding; Trillium: Research Funding; Bristol-Myers Squibb: Research Funding; Mayo Clinic Rochester: Employment; LAM Therapeutics: Research Funding; LAM Therapeutics: Research Funding; LAM Therapeutics: Research Funding; Regeneron: Research Funding; LAM Therapeutics: Research Funding; Trillium: Research Funding; Trillium: Research Funding; Affimed: Research Funding; Bristol-Myers Squibb: Research Funding; Seattle Genetics: Research Funding; Trillium: Research Funding; Affimed: Research Funding. Nieto:Astra-Zeneca: Research Funding; Affimed: Consultancy; Affimed: Research Funding; Novartis: Research Funding. Feldman:Celgene: Honoraria, Research Funding, Speakers Bureau; Seattle Genetics: Consultancy, Honoraria, Other: Travel expenses, Speakers Bureau; Pfizer: Research Funding; AbbVie: Honoraria, Other: Travel expenses, Speakers Bureau; Portola Pharma: Research Funding; Kite Pharma: Honoraria, Other: Travel expenses, Speakers Bureau; Janssen: Honoraria, Speakers Bureau; Pharmacyclics: Honoraria, Other: Travel expenses, Speakers Bureau; Kyowa Hakko Kirin: Research Funding; Eisai: Research Funding; Bayer: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Amgen: Research Funding; Cell Medica: Research Funding; Roche: Research Funding; Corvus: Research Funding; Viracta: Research Funding; Trillium: Research Funding; Roche: Research Funding; Takeda: Honoraria, Speakers Bureau. McGuirk:ArticulateScience LLC: Other: Assistance with manuscript preparation; Bellicum Pharmaceuticals: Research Funding; Kite Pharmaceuticals: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Gamida Cell: Research Funding; Pluristem Ltd: Research Funding; Juno Therapeutics: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Astellas: Research Funding; Novartis: Research Funding; Fresenius Biotech: Research Funding. Mohty:Jazz Pharmaceuticals: Honoraria, Research Funding. Stamatoulas Bastard:Celgene: Honoraria; Takeda: Consultancy. Houot:Bristol Myers Squibb: Honoraria; Merck Sharp Dohme: Honoraria. Manson:Bristol Myers Squibb: Honoraria. Orvain:Incyte: Honoraria; Novartis: Honoraria; Jazz Pharmaceuticals: Other: Travel & accommodations; Pfizer: Other: Travel & accommodations. Bouabdallah:Roche: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Takeda: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Frigault:Novartis: Consultancy; Kite/Gilead: Honoraria; Nkarta: Consultancy; Incyte: Consultancy; Juno/Celgene: Consultancy; Foundation Medicine: Consultancy; Xenetic: Consultancy. Chen:Takeda: Consultancy; Kiadis: Consultancy; Magenta: Consultancy; Abbvie: Consultancy; Incyte: Consultancy. Lynch:T.G. Therapeutics: Research Funding; Rhizen Pharmaceuticals S.A: Research Funding; Takeda Pharmaceuticals: Research Funding; Juno Therapeutics: Research Funding; Incyte Corporation: Research Funding; Johnson Graffe Keay Moniz & Wick LLP: Consultancy. Smith:AstraZeneca: Membership on an entity's Board of Directors or advisory committees, Research Funding; Merck Sharp & Dohme Corp: Consultancy, Research Funding; Acerta Pharma BV: Research Funding; Portola Pharmaceuticals: Research Funding; Pharmacyclics: Research Funding; Bristol-Myers Squibb (spouse): Research Funding; Denovo Biopharma: Research Funding; Genentech: Research Funding; Ignyta (spouse): Research Funding; Incyte Corporation: Research Funding; Ayala (spouse): Research Funding; Seattle Genetics: Research Funding. Byrne:Karyopharm: Research Funding. Cohen:Hutchison: Research Funding; Astra Zeneca: Research Funding; Janssen Pharmaceuticals: Consultancy; Seattle Genetics, Inc.: Consultancy, Research Funding; Bristol-Meyers Squibb Company: Research Funding; Takeda Pharmaceuticals North America, Inc.: Research Funding; Gilead/Kite: Consultancy; Genentech, Inc.: Consultancy, Research Funding; UNUM: Research Funding; ASH: Research Funding; LAM Therapeutics: Research Funding; Lymphoma Research Foundation: Research Funding. Svoboda:AstraZeneca: Consultancy; Celgene: Research Funding; Incyte: Research Funding; Pharmacyclics: Consultancy, Research Funding; Kyowa: Consultancy; Merck: Research Funding; BMS: Consultancy, Research Funding; Seattle Genetics: Consultancy, Research Funding. Santoro:Bayer: Consultancy, Speakers Bureau; MSD: Speakers Bureau; Arqule: Consultancy, Speakers Bureau; Pfizer: Consultancy, Speakers Bureau; AstraZeneca: Speakers Bureau; Gilead: Consultancy, Speakers Bureau; Servier: Consultancy, Speakers Bureau; Takeda: Speakers Bureau; BMS: Speakers Bureau; Roche: Speakers Bureau; Abb-Vie: Speakers Bureau; Amgen: Speakers Bureau; Celgene: Speakers Bureau; Novartis: Speakers Bureau; BMS: Consultancy; Lilly: Speakers Bureau; Sandoz: Speakers Bureau; Eisai: Consultancy, Speakers Bureau. Armand:Sigma Tau: Research Funding; Otsuka: Research Funding; Pfizer: Consultancy; ADC Therapeutics: Consultancy; Tensha: Research Funding; Affimed: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Roche: Research Funding; Adaptive: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Bristol-Myers Squibb: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Merck: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Infinity: Consultancy; Genentech: Research Funding. Zinzani:Roche: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Portola: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Celgene: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Immune Design: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Sandoz: Membership on an entity's Board of Directors or advisory committees; Servier: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; BMS: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Janssen-Cilag: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Gilead: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Celltrion: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Sanofi: Consultancy; Eusapharma: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Verastem: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; MSD: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Kyowa Kirin: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; TG Therapeutics: Honoraria, Speakers Bureau. Carlo-Stella:Servier: Consultancy, Honoraria, Other: Travel, accommodations; Genenta Science srl: Consultancy; Boehringer Ingelheim: Consultancy; F. Hoffmann-La Roche Ltd: Honoraria, Other: Travel, accommodations, Research Funding; Novartis: Consultancy, Research Funding; ADC Therapeutics: Consultancy, Other: Travel, accommodations, Research Funding; Sanofi: Consultancy, Research Funding; Rhizen Pharmaceuticals: Research Funding; Celgene: Research Funding; Amgen: Honoraria; AstraZeneca: Honoraria; Janssen Oncology: Honoraria; MSD: Honoraria; BMS: Honoraria; Janssen: Other: Travel, accommodations; Takeda: Other: Travel, accommodations.