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Activating BRAF mutations are found in a small subset of patients with newly diagnosed multiple myeloma, but prevalence increases in late-stage, refractory disease, and the mutations are associated with adverse outcome. This prospective single-arm, open-label, multicenter phase 2 trial assessed the efficacy and safety of combined BRAF/MEK inhibition, using encorafenib and binimetinib, in patients with relapsed/refractory multiple myeloma (RRMM) carrying a BRAFV600E mutation. Patients received 450 mg encorafenib once daily and binimetinib 45 mg twice daily. The primary end point was the overall response rate achieved within the first year after start of treatment according to International Myeloma Working Group criteria. Twelve RRMM patients with a median of 5 prior lines of therapy were enrolled. The overall response rate was 83.3%, with 10 patients achieving at least a partial response. The median progression-free survival was 5.6 months, and overall survival was 55% at 24 months. Emerging resistance to therapy was driven by RAS mutations and structural variants involving the BRAF locus. This is the first prospective clinical trial to demonstrate that combined BRAF/MEK inhibition is highly effective in patients with BRAFV600E-mutated RRMM, and it represents a successful targeted precision medicine approach in this disease. This trial was registered at www.clinicaltrials.gov as #NCT02834364.

The novel coronavirus SARS-CoV-2 and the associated infectious disease COVID-19 pose a significant challenge to healthcare systems worldwide. Patients with cancer have been identified as a high-risk population for severe infections, rendering prophylaxis and treatment strategies for these patients particularly important. Rapidly evolving clinical research, resulting in the recent advent of various vaccines and therapeutic agents against COVID-19, offers new options to improve care and protection of cancer patients. However, ongoing epidemiological changes and rise of new virus variants require repeated revisions and adaptations of prophylaxis and treatment strategies to meet these new challenges. Therefore, this guideline provides an update on evidence-based recommendations with regard to vaccination, pharmacological prophylaxis and treatment of COVID-19 in cancer patients in light of the currently dominant omicron variants. It was developed by an expert panel of the Infectious Diseases Working Party (AGIHO) of the German Society for Hematology and Medical Oncology (DGHO) based on a critical review of the most recent available data.

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Activating BRAF mutations are found in a small subset of patients with newly diagnosed multiple myeloma but prevalence increases in late stage, refractory disease, and are associated with adverse outcome. This prospective single-arm, open-label, multicenter phase II trial assessed the efficacy and safety of combined BRAF/MEK inhibition, using encorafenib and binimetinib, in patients with relapsed/refractory multiple myeloma (RRMM) carrying a BRAFV600E mutation (ClinicalTrials.gov identifier: NCT02834364). Patients received 450 mg encorafenib once daily and binimetinib 45 mg twice daily. The primary end point was the overall response rate achieved within the first year after start of treatment according to IMWG criteria. Twelve RRMM patients with a median of 5 prior lines of therapy were enrolled. The overall response rate was 83.3% with 10 patients achieving at least a partial response. The median progression-free survival (PFS) was 5.6 months and overall survival was 55% at 24 months. Emerging resistance to therapy was driven by RAS mutations and structural variants involving the BRAF locus. This is the first prospective clinical trial to demonstrate that combined BRAF/MEK inhibition is highly effective in patients with BRAFV600E mutated RRMM and represents a successful targeted precision medicine approach in this disease.

ZusammenfassungPatient*innen mit Krebserkrankungen haben ein erhöhtes Risiko, schwere Verläufe einer COVID-19-Erkrankung zu erleiden. Spezifische Schutzmaßnahmen inkl. der COVID-19-Impfungen sind daher hier von besonderer Bedeutung. Eine durch Therapie und Grunderkrankung oftmals bedingte Abwehrschwäche kann jedoch eine Herausforderung für Impfstrategien bei diesen Patient*innen darstellen. Aktuell sind in Deutschland vier COVID-19-Impfstoffe zugelassen, zwei mRNA- und zwei vektorbasierte Impfstoffe, die alle eine sehr gute Wirksamkeit gegen schwere Krankheitsverläufe zeigen. Hinsichtlich des Wirkmechanismus ist allen vier Impfstoffen die Induktion einer Produktion virusspezifischer Proteine in menschlichen Zellen gemeinsam mit nachfolgender Aktivierung einer adaptiven Immunantwort. Für Krebspatient*innen und medizinisches Personal wird die Impfung priorisiert empfohlen. Ein optimaler Zeitpunkt für die Impfung bei Neuerkrankten scheint vor Beginn einer Tumortherapie zu sein. Aufgrund des erhöhten Risikos von Krebspatient*innen für schwere Verläufe von COVID-19 wird die Impfung jedoch auch unter laufender Tumortherapie empfohlen. Die Impfantwort ist hier allerdings möglicherweise reduziert. In den besonderen Konstellationen einer vorherigen Stammzelltransplantation oder einer B‑Zell-depletierenden Therapie wird nach Möglichkeit ein mehrmonatiger Abstand zwischen Therapie und Impfung empfohlen, da hier ansonsten mit einer deutlich reduzierten Impfantwort gerechnet werden muss. Wenn sich erste Hinweise auf nur eine geringe Serokonversion bei Krebspatient*innen nach einmaliger Impfung bestätigen, können zukünftige Empfehlungen in Richtung mehrfacher Impfungen bei diesen Patient*innen gehen.

Despite major treatment advances in recent years, patients with multiple myeloma inevitably relapse. The RNA polymerase II complex has been identified as a promising therapeutic target in both proliferating and dormant cancer cells. Alpha-amanitin, a toxin so far without clinical application due to high liver toxicity, specifically inhibits this complex. Here, we describe the development of HDP-101, an anti–B-cell maturation antigen (BCMA) antibody conjugated with an amanitin derivative. HDP-101 displayed high efficacy against both proliferating and resting myeloma cells in vitro, sparing BCMA-negative cells. In subcutaneous and disseminated murine xenograft models, HDP-101 induced tumor regression at low doses, including durable complete remissions after a single intravenous dose. In cynomolgus monkeys, HDP-101 was well tolerated with a promising therapeutic index. In conclusion, HDP-101 safely and selectively delivers amanitin to myeloma cells and provides a novel therapeutic approach to overcome drug resistance in this disease.

Since its first detection in China in late 2019 the novel coronavirus SARS-CoV-2 and the associated infectious disease COVID-19 continue to have a major impact on global health care and clinical practice. Cancer patients, in particular those with haematological malignancies, seem to be at an increased risk for a severe course of infection. Deliberations to avoid or defer potentially immunosuppressive therapies in these patients need to be balanced against the overarching goal of providing optimal antineoplastic treatment. This poses a unique challenge to treating physicians. This guideline provides evidence-based recommendations regarding prevention, diagnostics and treatment of SARS-CoV-2 infection and COVID-19 as well as strategies towards safe antineoplastic care during the COVID-19 pandemic. It was prepared by the Infectious Diseases Working Party (AGIHO) of the German Society for Haematology and Medical Oncology (DGHO) by critically reviewing the currently available data on SARS-CoV-2 and COVID-19 in cancer patients applying evidence-based medicine criteria., Highlights • Cancer patients are vulnerable to SARS-CoV-2 infection and severe COVID-19. • Comprehensive management strategies are required in care for cancer patients. • Evidence-based recommendations help clinicians make informed treatment decisions. • Providing state-of-the-art cancer care is possible during COVID-19 pandemic.

Die Identifikation von BRAFV600E-Mutationen beim multiplen Myelom (MM) macht Hoffnung fur den Einsatz von BRAF-Inhibitoren bei der fortgeschrittenen Erkrankung mit klonaler Mutationsfrequenz. Aktuelle Behandlungsstrategien basieren auf Kombinationstherapien aus Proteasomenhemmern, Immunmodulatoren und monoklonalen Antikorpern sowie Chemotherapie mit autologer Stammzelltransplantation. Fur spezielle Patientengruppen konnte die personalisierte tumorspezifische Therapie von Bedeutung sein. Hierfur sind gerade bei genetisch heterogenen Erkrankungen wie dem MM fundierte Kenntnisse uber das Genom (Treibermutationen) und Transkriptom (Aktivitatsstatus) in den betroffenen Signalwegen erforderlich. Die verfugbaren Publikationen wurden zusammenfassend dargestellt. Die Wirkung von BRAF-Inhibitoren wurde bisher nur in einigen Fallberichten beschrieben, auserhalb der Zulassung („off-label use“). Diese Berichte geben jedoch Aufschluss uber das Verhalten der BRAF-mutierten Myelomzellen unter Inhibition, wie Resistenzen entstehen konnen und wie man diesen entgegenwirken kann. Die Kombination aus Inhibitoren des RAS/RAF-Signalwegs untereinander sowie mit Proteasomenhemmern zeigten Erfolge. Grosere Patientenzahlen sind notwendig, um statistische Aussagen treffen zu konnen. Das molekulare Screening der Myelompatienten ermoglicht bei Risikopatienten den fruhen Einsatz neuer Therapieoptionen mit BRAF-Inhibitoren. Analog zum Melanom sollte auch hier eine Kombination von BRAF-Inhibitoren mit einem MEK-Inhibitor erfolgen. In der Behandlung der komplexen genetischen Erkrankung des MM stellt die personalisierte Therapie eine vielversprechende Option dar, v. a. in Kombination mit konventionellen Strategien.

The MM5 trial aimed at demonstrating a progression-free survival (PFS) difference in continued vs. response-adapted (in case of complete response, CR) lenalidomide (LEN) maintenance therapy (MT) in newly diagnosed, transplant-eligible multiple myeloma (MM). Patients were equally randomized to receive induction therapy with PAd (bortezomib/doxorubicin/dexamethasone) or VCD (bortezomib/cyclophosphamide/dexamethasone), high-dose melphalan and autologous blood stem cell transplantation, and LEN consolidation, followed by either LEN MT for a fixed duration of 2 years (LEN-2Y) or until achievement of CR (LEN-CR, intention-to-treat population n = 502): arms A1:PAd + LEN-2Y (n = 125), B1:PAd + LEN-CR (n = 126), A2:VCD + LEN-2Y (n = 126), B2:VCD + LEN-CR (n = 125). In the LEN-CR group (B1 + B2), n = 88/17.5% patients did not start or discontinued LEN MT due to CR. There was no PFS (p = 0.60, primary endpoint) nor overall survival (OS) (p = 0.15) difference between the four study arms. On pooled LEN MT strategies, OS (hazard ratio, hazard ratio [HR] = 1.42, p = 0.03) but not PFS (HR = 1.15, p = 0.20) was shorter in LEN-CR (B1 + B2) vs. LEN-2Y (A1 + A2) groups. PFS was shortened on landmark analyses from the start of LEN MT in patients being in CR in the LEN-CR group (LEN-CR vs. LEN-2Y, HR = 1.84, p = 0.02). OS from first progression was shortened in the LEN-CR vs. LEN-2Y group (HR = 1.60, p = 0.01). LEN MT should be applied beyond CR for at least 2 years.

BACKGROUND Chronic graft-versus-host disease (cGVHD) represents a double-edged sword. In its nonsevere form, cGVHD associates with better control of the malignant disease, thus highlighting graft-versus-leukemia effects. However, severe cGVHD leads to debilitating morbidity and increased nonrelapse mortality. The prediction of severe cGVHD, in particular at disease onset, is therefore of high importance for ensuing clinical decisions and overall success of allogeneic stem cell transplantations. CXC-chemokine ligand 9 (CXCL9) is an interferon-inducible chemokine of the CXC family and is increased in cGVHD. Endothelial activation and stress index (EASIX) was shown to predict death after acute graft-versus-host disease. We explored CXCL9 and EASIX as predictors of severe cGVHD. METHODS Sera and clinical data of 480 patients were available who survived at least 6 months following allogeneic stem cell transplantation without steroid-refractory acute graft-versus-host disease and without early relapse. CXCL9 and EASIX were measured on day +100 and onset of cGVHD. RESULTS Development of nonsevere cGVHD was significantly associated with improved overall survival (hazard ratio 0.53, P < 0.001). CXCL9 serum levels at the onset of cGVHD predicted the development of severe cGVHD later on (hazard ratio 1.33, P = 0.02). In contrast, EASIX at the onset of cGVHD was not associated with cGVHD severity but was a significant independent risk factor for overall mortality and nonrelapse mortality. CONCLUSIONS CXCL9 levels at the onset of cGVHD can help to predict severe courses of the disease and have potential for optimizing tailored administration of immunosuppressive therapy.

Patients with cancer are at particular risk for infection but also have diminished vaccine responses, usually quantified by the level of specific antibodies. Nonetheless, vaccines are specifically recommended in this vulnerable patient group. Here, we discuss the cellular part of the vaccine response in patients with cancer. We summarize the experience with vaccines prior to and during the SARS-CoV-2 pandemic in different subgroups, and we discuss why, especially in patients with cancer, T cells may be the more reliable correlate of protection. Finally, we provide a brief outlook on options to improve the cellular response to vaccines.

To assess morbidity and mortality of parainfluenza virus (PIV) infections in immunocompromised patients, we analysed PIV infections in a hematology and stem cell transplantation (SCT) unit over the course of three years. Isolated PIV strains were characterized by sequence analysis and nosocomial transmission was assessed including phylogenetic analysis of viral strains. 109 cases of PIV infection were identified, 75 in the setting of SCT. PIV type 3 (n = 68) was the most frequent subtype. PIV lower respiratory tract infection (LRTI) was observed in 47 patients (43%) with a mortality of 19%. Severe leukopenia, prior steroid therapy and presence of co-infections were significant risk factors for development of PIV-LRTI in multivariate analysis. Prolonged viral shedding was frequently observed with a median duration of 14 days and up to 79 days, especially in patients after allogeneic SCT and with LRTI. Nosocomial transmission occurred in 47 patients. Phylogenetic analysis of isolated PIV strains and combination with clinical data enabled the identification of seven separate clusters of nosocomial transmission. In conclusion, we observed significant morbidity and mortality of PIV infection in hematology and transplant patients. The clinical impact of co-infections, the possibility of long-term viral shedding and frequent nosocomial transmission should be taken into account when designing infection control strategies.

Simple Summary High-dose chemotherapy and autologous stem cell transplantation (HDCT/ASCT) is a standard treatment in patients with newly diagnosed multiple myeloma (MM). At relapse, salvage HDCT/ASCT is a treatment option in patients with sufficient benefit from frontline HDCT/ASCT, but no evidence is currently available regarding its role in the era of triplet regimens combining the most active drug classes for relapsed MM. To evaluate the outcome after salvage HDCT/ASCT following re-induction treatment with carfilzomib/lenalidomide/dexamethasone (KRD) and to identify prognostic factors, we conducted a retrospective analysis of patients that had previously undergone frontline HDCT/ASCT. We found that deep remissions achieved with KRd followed by salvage autologous transplantation were associated with favorable PFS and were enhanced by maintenance treatment. Salvage autologous transplantation after state-of-the-art triplet re-induction was a safe and effective strategy for RRMM patients that may offer the chance to avoid refractoriness to multiple novel agents at the next relapse. Abstract Salvage high-dose chemotherapy and autologous stem cell transplantation (HDCT/ASCT) is a treatment option for relapsed and/or refractory multiple myeloma (RRMM). No data are available on salvage HDCT/ASCT following re-induction treatment with state-of-the-art triplet regimens. We retrospectively report on 44 patients receiving salvage HDCT/ASCT following re-induction with carfilzomib/lenalidomide/dexamethasone (KRd). All patients received frontline HDCT/ASCT with median time to progression (TTP1) of 2.9 (1.2–13.5) years, enabling paired comparison of frontline and salvage HDCT/ASCT. After re-induction and before salvage transplant, 25/44 patients (57%) attained ≥ very good partial response (VGPR), which increased to 34/44 (77%) at best response after salvage HDCT/ASCT. Median progression-free survival (PFS) was 23.3 months from salvage HDCT/ASCT. Patients with ≥ VGPR at the time of salvage HDCT/ASCT and those receiving maintenance treatment post salvage HDCT/ASCT had significantly superior PFS (hazard ratio (HR) 0.19, p = 0.001 and HR 0.20, p = 0.009). In patients achieving at least an equal depth of response before salvage HDCT/ASCT as before frontline HDCT/ASCT, PFS after salvage HDCT/ASCT was comparable to the frontline situation (p = 0.3). This is the first report of state-of-the-art triplet re-induction and salvage HDCT/ASCT for RRMM after frontline transplantation. Deep remissions achieved with KRd translate into prolonged PFS following salvage HDCT/ASCT and are enhanced by maintenance treatment.

Patient*innen mit Krebserkrankungen haben ein erhöhtes Risiko, schwere Verläufe einer COVID-19-Erkrankung zu erleiden. Spezifische Schutzmaßnahmen inkl. der COVID-19-Impfungen sind daher hier von besonderer Bedeutung. Eine durch Therapie und Grunderkrankung oftmals bedingte Abwehrschwäche kann jedoch eine Herausforderung für Impfstrategien bei diesen Patient*innen darstellen. Aktuell sind in Deutschland vier COVID-19-Impfstoffe zugelassen, zwei mRNA- und zwei vektorbasierte Impfstoffe, die alle eine sehr gute Wirksamkeit gegen schwere Krankheitsverläufe zeigen. Hinsichtlich des Wirkmechanismus ist allen vier Impfstoffen die Induktion einer Produktion virusspezifischer Proteine in menschlichen Zellen gemeinsam mit nachfolgender Aktivierung einer adaptiven Immunantwort. Für Krebspatient*innen und medizinisches Personal wird die Impfung priorisiert empfohlen. Ein optimaler Zeitpunkt für die Impfung bei Neuerkrankten scheint vor Beginn einer Tumortherapie zu sein. Aufgrund des erhöhten Risikos von Krebspatient*innen für schwere Verläufe von COVID-19 wird die Impfung jedoch auch unter laufender Tumortherapie empfohlen. Die Impfantwort ist hier allerdings möglicherweise reduziert. In den besonderen Konstellationen einer vorherigen Stammzelltransplantation oder einer B‑Zell-depletierenden Therapie wird nach Möglichkeit ein mehrmonatiger Abstand zwischen Therapie und Impfung empfohlen, da hier ansonsten mit einer deutlich reduzierten Impfantwort gerechnet werden muss. Wenn sich erste Hinweise auf nur eine geringe Serokonversion bei Krebspatient*innen nach einmaliger Impfung bestätigen, können zukünftige Empfehlungen in Richtung mehrfacher Impfungen bei diesen Patient*innen gehen.

Background Relapsed/refractory multiple myeloma (RRMM) is characterized by a high inter- and intratumor heterogeneity and a complex interplay of myeloma cells with the bone marrow microenvironment (BME). Accordingly, there is an urgent need to dissect subclone structure, transcriptional heterogeneity and cellular interactions to unravel the molecular mechanisms underlying drug resistance in RRMM. Methods Single cell RNA sequencing (scRNA-seq) of ~210,000 cells from bone marrow aspirates sorted into CD138+ and CD138– fractions was conducted for 20 heavily pretreated RRMM patients. RRMM subclones were called from the scRNA-seq data based on a copy number aberration (CNA) analysis that was confirmed by interphase fluorescence in situ hybridization and whole genome sequencing. From the scRNA-seq data the composition and abundance of immune cell types in the BME was determined. Interactions of myeloma cells with the BME were characterized by an analysis of the correlated expression of ligand-receptor pairs. Selected findings from the scRNA-seq analysis were validated by flow cytometry. Results Subclones with distinct chromosomal aberrations were reliably identified at the single cell level based on CNAs inferred from scRNA-seq data. The analysis revealed a subclonal 1q-gain (+1q) in 10/20 samples, for which a gene expression signature of recurrently upregulated genes was derived. These +1q subclones frequently expanded during treatment. Furthermore, RRMM cells shaped an immune suppressive BME by upregulation of inflammatory cytokines and close interplay with the myeloid compartment. RRMM cells appear to reprogram the BME by upregulation of inflammatory cytokines and ligands of inhibitory receptors expressed on T and NK-cells. Specifically, the immune cell compartment of RRMM patients displayed an accumulation of PD1+ γδ T-cells and myeloid populations compared to healthy donors or early disease. In addition, we observed a depletion of hematopoietic progenitors in patients with high expression of genes associated with inflammatory signaling in the BME. Upon treatment with immunomodulatory drugs, reprogrammed plasmacytoid dendritic cells expanded. Focusing on patients with +1q, we found an enrichment of a rare M2-like tumor associated macrophage population while GZMB+ NK effector cells were depleted in these patients, indicating that +1q has a distinct effect on the BME in RRMM. Conclusions Our study resolves transcriptional features of subclones in RRMM and mechanisms of microenvironmental reprogramming. The insight gained in our study on the evolution of RRMM heterogeneity and its bone marrow milieu will support the development of novel treatment approaches and potentially guide clinical decision making.

Background Salvage high dose chemotherapy followed by autologous stem cell transplantation (HDCT/ASCT) is a treatment option in patients with relapsed and/or refractory multiple myeloma (RRMM) after prolonged remissions with frontline transplantation. The role of salvage HDCT/ASCT following re-induction treatment with state-of-the-art triplet regimens has not been defined. The present analysis therefore aims to investigate the efficacy and toxicity of salvage HDCT/ASCT after carfilzomib (CFZ)/lenalidomide (LEN)/dexamethasone (KRd) re-induction with or without post-transplant maintenance treatment. Methods We retrospectively assessed efficacy and toxicity in 44 patients receiving salvage HDCT/ASCT following re-induction with carfilzomib/lenalidomide/dexamethasone (KRd). All patients had received frontline HDCT/ASCT with median time to progression (TTP1) of 2.9 (1.2-13.5) years, allowing for paired comparison of frontline and salvage HDCT/ASCT. Median age at time of re-induction was 58.9 years (range 40-71) and n=38/44 patients (86%) had only 1 prior line of therapy (range 1-3). Sixteen of 44 patients (36%) were LEN pretreated and all patients were CFZ-naive. Maintenance treatment was administered in n=22/44 patients (50%) after frontline HDCT/ASCT and in n=17/44 patients (39%) after salvage HDCT/ASCT. Results After a median of 3 re-induction cycles (range 3-9), 25/44 patients (57%) attained at least very good partial response (VGPR), which increased to 34/44 (77%) at best response after salvage HDCT/ASCT. Patients achieving deep remissions during frontline treatment were more likely to re-achieve deep remissions in the salvage setting at each individual timepoint: after (re-)induction (≥VGPR: odds ratio [OR] 6.22; 95% confidence interval [95%-CI] 1.33-29.01; p=0.02), after (salvage) HDCT/ASCT (≥nCR: OR 5.71; 95%-CI 1.44-22.62; p=0.01) and at best response (≥nCR: OR 4.50; 95%-CI 1.12-18.13; p=0.03). After a median follow up of 23.9 months, median progression-free survival (PFS) was 23.3 months from salvage HDCT/ASCT. Patients at least in VGPR at the time of salvage HDCT/ASCT and those receiving maintenance treatment post salvage HDCT/ASCT had significantly superior PFS (hazard ratio [HR] 0.19, p=0.001 and HR 0.20, p=0.009). In patients achieving at least an equal depth of response before salvage HDCT/ASCT as before frontline HDCT/ASCT, PFS after salvage HDCT/ASCT was comparable to the frontline situation (p=0.3). Conclusion Despite higher comorbidity scores at salvage HDCT/ASCT, no significant increase in relevant toxicity parameters including infections and intensive care unit admission was observed and no transplant-related mortality occurred after salvage HDCT/ASCT. This is the first report of state-of-the-art triplet re-induction and salvage HDCT/ASCT for RRMM after frontline transplantation. Deep remissions achieved with KRd translate into prolonged PFS following salvage HDCT/ASCT and are enhanced by maintenance treatment.

The work was supported by the Deutsche Forschungsgemeinschaft (KFO216), the IZKF, the BTHA and the CDW Stiftung (KMK). UM was supported by a grant of the German Excellence Initiative to the Graduate School of Life Sciences, University of Wurzburg.

Background: During the past decade, prognostic tools and outcomes of patients with newly-diagnosed multiple myeloma (NDMM) markedly improved. Data from clinical trials evaluating early morbidity and mortality including patients with transplant-eligible NDMM treated with novel agents are scarce. Thus, we aimed to analyze early morbidity and mortality in this patient cohort, devise and validate a predictive score to identify patients at risk. Patients and methods: Between July 2005 and January 2018, 1333 patients with transplant-eligible NDMM from three subsequent phase III trials, HD4, MM5 and HD6 from the German-speaking Myeloma Multicenter Group (GMMG), received a novel agent-based induction therapy with either bortezomib (BTZ) / doxorubicine / dexamethasone (DEX; PAD: n=192, HD4; PAd: n=296, MM5), BTZ / cyclophosphamide / DEX (VCD: n=300, MM5), BTZ / lenalidomide / DEX (VRD: n=272, HD6) or elotuzumab / VRD (ELO-VRD: n=273, HD6). Severe infections (SI) were defined as any infection grade ≥ 3 according to the Common Terminology Criteria for Adverse Events (CTCAE). SI and early deaths were counted on and up to 30 days post induction therapy. Uni-/multivariable logistic regression models were used to assess predictive factors for SI and early death and to account for trial effects. Data from the European Myeloma Network (EMN) 02 / Dutch-Belgian Cooperative Trial Group for Hematology Oncology Foundation (HOVON) 95 phase III trial including 1497 patients with transplant-eligible NDMM receiving induction therapy with VCD were used to validate a predictive score for SI and early mortality. Results: Overall, early mortality during induction therapy was low (n=24, 1.8%) in the GMMG cohort. SI were the most common cause for early deaths (n=15, 62.5%) as compared to MM progression-related death (n=5, 20.8%) and other causes (n=4, 16.7%). Rates of SI during induction therapy were 11.9% (n=159) and decreased in subsequent trial generations: HD4-PAD: 27.1%, MM5-PAd: 10.8%, MM5-VCD: 9.3%, HD6-VRD: 7.3% and HD6-ELO-VRD: 9.9% of patients. In the EMN02/HO95 trial, early mortality was 1.7% (n=25) and rates of SI were 6.8% (n=101). A multivariate model including patient and disease baseline characteristics identified four major risk factors for SI and/or early death on induction therapy in the GMMG cohort: age (>60 years; odds ratio [OR]=1.70, 95% confidence interval [95% CI]: 1.21-2.40, p=0.002), International Staging System (stage III; OR=1.92, 95% CI: 1.22-2.94, p=0.005), platelet count (1; OR=1.82, 95% CI: 1.10-3.06, p=0.022). A sum score based on these four risk factors (one risk factor = one point) was built and included 519 (39.5%), 550 (41.9%) and 245 (18.6%) patients with a score of 0, 1 and ≥2 points. A higher score gradually predicted an increasing risk for SI and/or death during induction therapy: 0 points=7.9%, 1 point=11.5% and ≥2 points=23.2% (p In the EMN02/HO95 cohort, 673 (45.6%), 587 (39.7%) and 217 (14.7%) patients had a score of 0, 1 and ≥2 points. The score was successfully validated in the EMN02/HO95 cohort: SI and/or death during induction therapy: 0 points=5.0%, 1 point=8.3% and ≥2 points=11.9% (p Conclusions: To date, this is the largest pooled analysis of individual patient data on early morbidity and mortality in patients with transplant-eligible NDMM treated with novel agent-based induction therapy. Our analysis highlights a decreasing incidence of SI and early mortality and proposes a validated, easy-to-use score to identify patients at excessive risk for SI and/or early death during induction therapy. This allows the implementation of intensive monitoring, preventive and supportive strategies for this subgroup of patients in further clinical trials and also routine care. Figure 1 Figure 1. Disclosures Mai: Celgene / BMS: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: travel accommodations and expenses, Research Funding; Glaxo Smith Kline: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: travel accommodations and expenses, Research Funding; Janssen-Cilag: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: travel accommodations and expenses, Research Funding; Takeda: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: travel accommodations and expenses, Research Funding. Salwender: AbbVie: Honoraria, Other: TRAVEL, ACCOMMODATIONS, EXPENSES; Amgen: Honoraria, Other: TRAVEL, ACCOMMODATIONS, EXPENSES; Takeda: Honoraria; Sanofi: Honoraria, Other: TRAVEL, ACCOMMODATIONS, EXPENSES; GlaxoSmithKline: Honoraria, Other: TRAVEL, ACCOMMODATIONS, EXPENSES; Janssen-Cilag: Honoraria, Other: TRAVEL, ACCOMMODATIONS, EXPENSES; Bristol-Myers Squibb/Celgene: Honoraria, Other: TRAVEL, ACCOMMODATIONS, EXPENSES; Oncopeptides: Honoraria; Chugai: Honoraria; Pfizer: Honoraria. Zweegman: Oncopeptides: Membership on an entity's Board of Directors or advisory committees; Sanofi: Membership on an entity's Board of Directors or advisory committees; BMS: Membership on an entity's Board of Directors or advisory committees; Takeda: Membership on an entity's Board of Directors or advisory committees, Research Funding; Janssen: Membership on an entity's Board of Directors or advisory committees, Research Funding. Munder: GSK: Consultancy; BMS: Consultancy, Honoraria; Abbvie: Consultancy; Takeda: Consultancy, Honoraria; Amgen: Honoraria; Sanofi: Consultancy; Janssen: Consultancy, Honoraria; Incyte: Research Funding. Pantani: Janssen: Honoraria; Amgen: Honoraria. Brossart: BMS: Consultancy, Honoraria, Research Funding; Amgen: Consultancy, Honoraria; MSD: Honoraria. Beksac: Amgen: Consultancy, Speakers Bureau; Janssen: Consultancy, Speakers Bureau; Celgene: Consultancy, Speakers Bureau; Sanofi: Consultancy, Speakers Bureau; Takeda: Consultancy, Speakers Bureau; Oncopeptides: Consultancy. Raab: BMS: Consultancy, Membership on an entity's Board of Directors or advisory committees; Roche: Consultancy; Abbvie: Consultancy, Honoraria; Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding; GSK: Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; Sanofi: Membership on an entity's Board of Directors or advisory committees, Research Funding; Amgen: Consultancy, Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees. Dürig: Celgene: Membership on an entity's Board of Directors or advisory committees, Other: Travel Support, Speakers Bureau; Janssen: Membership on an entity's Board of Directors or advisory committees, Other: Travel Support, Speakers Bureau; Takeda: Membership on an entity's Board of Directors or advisory committees; BMS: Membership on an entity's Board of Directors or advisory committees. Besemer: Takeda: Honoraria; Janssen: Honoraria; GSK: Honoraria. Fenk: GSK: Honoraria; Amgen: Honoraria; Janssen: Honoraria; BMS/Celgene: Honoraria; Takeda: Honoraria. Haenel: Bayer Vital: Honoraria; Jazz: Consultancy, Honoraria; GSK: Consultancy; Takeda: Consultancy, Honoraria; Roche: Consultancy, Honoraria; Novartis: Consultancy, Honoraria; Amgen: Consultancy; Celgene: Consultancy, Honoraria. Metzler: Takeda: Consultancy; BMS: Consultancy; GSK: Consultancy; Amgen: Consultancy; Janssen: Consultancy; AstraZeneca: Consultancy; Pfizer: Consultancy; Sanofi: Consultancy. Graeven: Amgen: Honoraria; Sanofi Aventis: Honoraria; Celgene: Honoraria, Research Funding; Johnson and Johnson: Honoraria; Astra Zeneca: Honoraria; MSD: Consultancy; Boehringer Ingelheim: Honoraria; BMS: Honoraria; Fujifilm: Honoraria; Roche: Research Funding; Gilead: Research Funding; Ipsen Bioscience: Research Funding; MacroGenics: Research Funding. Boccadoro: Janssen and GSK: Membership on an entity's Board of Directors or advisory committees; Sanofi, Celgene, Amgen, Janssen, Novartis, Bristol-Myers Squibb, and AbbVie: Honoraria; Sanofi, Celgene, Amgen, Janssen, Novartis, Bristol-Myers Squibb, and Mundipharma: Research Funding. Scheid: Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees; BMS: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Roche: Consultancy; Abbvie: Honoraria; Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Amgen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees. Dimopoulos: Janssen: Honoraria; BMS: Honoraria; Amgen: Honoraria; Takeda: Honoraria; Beigene: Honoraria. Weisel: Oncopeptides: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Bristol Myers Squibb: 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; Roche: Honoraria; Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Adaptive Biotechnologies: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; GSK: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Amgen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Karyopharm: 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, Research Funding; Sanofi: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Abbvie: Consultancy; Novartis: Honoraria; Pfizer: Honoraria. Cavo: Adaptive Biotechnologies: Consultancy, Honoraria; Novartis: Honoraria; GlaxoSmithKline: Consultancy, Honoraria; Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel Accommodations, Speakers Bureau; Takeda: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; AbbVie: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Amgen: 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, Other: TRAVEL, ACCOMMODATIONS, EXPENSES, Speakers Bureau; Sanofi: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Bristol-Myers Squib: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Sonneveld: SkylineDx: Honoraria, Research Funding; Karyopharm: Consultancy, Honoraria, Research Funding; Celgene/BMS: Consultancy, Honoraria, Research Funding; Janssen: Consultancy, Honoraria, Research Funding; Amgen: Consultancy, Honoraria, Research Funding; Takeda: Consultancy, Honoraria, Research Funding. Goldschmidt: Mundipharma: Research Funding; Incyte: Research Funding; Janssen: Consultancy, Honoraria, Other: Grants and/or Provision of Investigational Medicinal Product, Research Funding; Johns Hopkins University: Other: Grant; Molecular Partners: Research Funding; MSD: Research Funding; GSK: Honoraria; Chugai: Honoraria, Other: Grants and/or Provision of Investigational Medicinal Product, Research Funding; Celgene: Consultancy, Honoraria, Other: Grants and/or Provision of Investigational Medicinal Product, Research Funding; BMS: Consultancy, Honoraria, Other: Grants and/or Provision of Investigational Medicinal Product, Research Funding; Adaptive Biotechnology: Consultancy; Amgen: Consultancy, Honoraria, Other: Grants and/or Provision of Investigational Medicinal Product, Research Funding; Novartis: Honoraria, Research Funding; Dietmar-Hopp-Foundation: Other: Grant; Sanofi: Consultancy, Honoraria, Other: Grants and/or Provision of Investigational Medicinal Product, Research Funding; Takeda: Consultancy, Research Funding.

Introduction Despite new treatment approaches, in most patients with multiple myeloma (MM) resistant subclones expand, finally resulting in the development of relapsed/refractory disease (RRMM). Recent single-cell transcriptomic (scRNA-seq) studies have improved our understanding of tumor heterogeneity in MM, but our knowledge about the regulatory processes and gene expression signatures in resistant subclones is still limited. Thus, we performed single-cell assay for transposase-accessible chromatin using sequencing (scATAC-seq) as well as scRNA-seq from the same MM patient samples and developed a new approach for the analysis of the transcriptome and epigenome of competing subclones. Methods CD138+ bone marrow cells of 11 RRMM patients were longitudinally collected and profiled using 10X Genomics scRNA- and scATAC-seq platform. Pre-processing was performed with CellRanger and downstream analysis using Seurat and ArchR. To determine clones based on copy number variations (CNVs), we leveraged inferCNV for scRNA-seq and developed a sliding window approach adapted from a previously published method by Satpathy et al. for scATAC-seq data. Whole genome sequencing was available to confirm the identified CNV clones. Results We obtained chromatin accessibility profiles of >43000 cells after quality control, establishing the first epigenetic map of RRMM with clearly separated clusters for each patient. Samples from distinct MM subgroups, particularly t(4;14) and t(11;14), clustered together in a pseudo-bulk analysis based on transcription factor activity scores from scATAC. To investigate treatment-induced clonal dynamics we aligned sc chromatin accessibility profiles to clones inferred in scRNA-seq based on CNVs enabling us to track individual tumor subclones over time. An example for clonal adaptation is a patient with two subclones that both responded differently to pomalidomide plus anti-CD38 treatment: while clone 1 showed a higher activity for members of IRF family, ZEB1 and KLF family members were more active in clone 2. Branching evolution was e.g. observed in a patient treated with a MEK/BRAF inhibitor. This patient showed two subclones before treatment, achieved a complete remission and relapsed with one dominant clone. One of the initial subclones could be identified as the precursor of this dominant clone with both showing high activity of NFKB family members, while higher activity of SOX10/15 was only observed upon MEK/BRAF inhibition. An example for combined clonal adaptation and selection was observed in a patient with bi-allelic inactivation of TP53 in one of the two subclones before MCL1 inhibition. Interestingly, this clone was depleted at relapse. Conclusions In summary, our new approach to track individual tumor subclones over time indicates clonal adaptation or selection in virtually all RRMM patients and reveals new insights into regulatory mechanisms underlying treatment-resistance, opening potential avenues for new therapies.

We compare, in this manuscript, antibiotic prophylaxis versus granulocyte-colony stimulating factor (G-CSF) support as anti-infective strategies, in patients with multiple myeloma (MM), undergoing high-dose therapy followed by autologous stem cell transplantation (HDT/ASCT). At our institution, antibiotic prophylaxis after HDT/ASCT in MM was stopped in January 2017 and replaced by G-CSF support in March 2017. Consecutive MM patients who received HDT/ASCT between March 2016 and July 2018 were included in this single-center retrospective analysis. In total, 298 patients and 353 individual cases of HDT/ASCT were evaluated. In multivariate analyses, G-CSF support was associated with a significantly shortened duration of severe leukopenia &lt, 1/nL (p &lt, 0.001, hazard ratio (HR) = 16.22), and hospitalization (estimate = −0.19, p &lt, 0.001) compared to antibiotic prophylaxis. Rates of febrile neutropenia, need of antimicrobial therapy, transfer to intensive care unit, and death, were similar between the two groups. Furthermore, antibiotic prophylaxis was associated with a significantly increased risk for the development of multidrug resistant bacteria especially vancomycin-resistant Enterococcus faecium compared to G-CSF support (odds ratio (OR) = 17.38, p = 0.01). Stop of antibiotic prophylaxis as an anti-infective strategy was associated with a reduction in overall resistance rates of bacterial isolates. These results indicate that G-CSF support should be the preferred option in MM patients undergoing HDT/ASCT.

Introduction: The treatment of patients (pts) with rrMM remains challenging and response is often limited in depth and duration. In contrast to many other malignant diseases, targeted therapy in MM is hampered by the limited number of actionable targets. Activating mutations of BRAF have been found in 2-4% of newly diagnosed MM and in up to 8% of rrMM. Several case reports have reported clinical efficacy of downstream pathway inhibition in MM. This phase II trial is evaluating the safety and efficacy of combined BRAF/MEK inhibition in rrMM pts with BRAF V600E mutation. Aims: The primary objective of this study was to demonstrate the therapeutic efficacy of encorafenib in combination with binimetinib. The primary endpoint was the overall response rate (ORR), defined as best response within 1 year of treatment. Main secondary endpoints included progression-free survival (PFS) and duration of response. Safety analyses included all adverse events (AEs) with those of grade 1/2 only being assessed further if considered to be related to study medications by the investigator. Methods: A total of 15 pts with rrMM who have failed at least 2 prior lines of therapy, including a proteasome inhibitor (PI) and an immunomodulatory drug (IMID), were planned to be enrolled in this open-label phase II multicenter trial. Key inclusion criteria were presence of a BRAF V600E/K mutation confirmed by both mutation-specific immunohistochemistry (IHC) and next-generation sequencing in more than 50% of MM cells. Exclusion criteria included plasma cell leukemia, CNS involvement, cardiac dysfunction, or a history of retinal vein occlusion. Pts received encorafenib 450mg p.o. daily and binimetinib 45mg p.o. twice daily. Responses were assessed using IMWG 2016 criteria. The primary endpoint was analyzed by testing the one-sided null hypothesis of ORR Results: As of July 2020, 12 pts have been enrolled and were evaluable for safety and 11 pts were evaluable for response as 1 pt had just completed cycle 1 with confirmation of response pending at the time of data lock. Subtypes of MM were IgG in 6 pts, IgA in 2 pts, and Bence Jones in 4 pts. Pts had received a median of 5 prior lines of therapy (range 2-14). All pts had failed previous treatment with both a PI and an IMID and in addition carfilzomib, pomalidomid, and/or anti-CD38 antibodies in 8/4/6 pts, respectively. The study already reached its primary endpoint. The ORR was 82% (lower limit of the 95% CI 56.4%, one-sided exact binomial test, p Adverse events of all grades, assessed to be at least possibly related to a study drug, occurred in 9/12 pts and included blurred vision, macula edema, cramps, arthralgia, diarrhea, skin rash, and decreased left ventricular function. Grade 3 or 4 AEs irrespective of causality occurring in more than 1 pt were reported in 8 pts with anemia, hypertension and thrombocytopenia (3/ 3/ 2 pts, respectively). SAEs were reported in 2 pts, respiratory tract infection in both pts and tooth decay in 1 pt that was not related to the study medication. No deaths occurred while on treatment or within 30 days of the end of treatment. Preliminary results of biomarker assessments reveal new RAS mutations and amplification of the BRAF locus at the time of relapse while on study treatment as potential markers of resistance. Analysis of pharmacodynamic markers by phospho-IHC reveals suppression of BRAF/MEK signaling at cycle 1 / day 28 and restoration of expression at the time of relapse. Conclusion: Targeting activating BRAF mutations in rrMM by combining the BRAF inhibitor, encorafenib, and the MEK inhibitor, binimetinib, induces rapid and deep responses in the majority of pts. No new safety signal has been observed when compared to prior reports on these compounds. The study reached its primary endpoint with fewer pts than expected. The primary efficacy and safety analysis will be presented at the conference. Disclosures Raab: Janssen: Membership on an entity's Board of Directors or advisory committees; Takeda: Membership on an entity's Board of Directors or advisory committees; Heidelberg Pharma: Research Funding; Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Membership on an entity's Board of Directors or advisory committees; Sanofi: Membership on an entity's Board of Directors or advisory committees, Research Funding; Bristol-Myers Squibb: Membership on an entity's Board of Directors or advisory committees; Amgen: Membership on an entity's Board of Directors or advisory committees. Scheid:BMS: Honoraria; Amgen: Honoraria; Novartis: Honoraria, Research Funding; Takeda: Honoraria, Research Funding; Janssen: Honoraria, Research Funding. Besemer:GSK: Honoraria; Janssen: Honoraria. Metzler:Janssen: Consultancy; Amgen: Consultancy; Takeda: Consultancy; GSK: Consultancy; BMS: Consultancy. Khandanpour:Astra Zeneca: Research Funding; Sanofi: Consultancy; Janssen: Consultancy; Amgen: Consultancy; Celgene: Consultancy. Trautmann-Grill:Janssen: Consultancy; Celgene: Consultancy; Sanofi: Consultancy; Takeda: Consultancy, Honoraria; GSK: Consultancy; BMS: Honoraria. Goldschmidt:Mundipharma GmbH: Research Funding; Takeda: Membership on an entity's Board of Directors or advisory committees, Research Funding; Merck Sharp and Dohme (MSD): Research Funding; Chugai: Honoraria, Other: Grants and/or provision of Investigational Medicinal Product:, Research Funding; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Grants and/or provision of Investigational Medicinal Product:, Research Funding; BMS: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Grants and/or provision of Investigational Medicinal Product:, Research Funding; University Hospital Heidelberg, Internal Medicine V and National Center for Tumor Diseases (NCT), Heidelberg, Germany: Current Employment; GlaxoSmithKline (GSK): Honoraria; Adaptive Biotechnology: Membership on an entity's Board of Directors or advisory committees; Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Grants and/or provision of Investigational Medicinal Product, Research Funding; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Grants and/or provision of Investigational Medicinal Product:, Research Funding; Novartis: Honoraria, Research Funding; Molecular Partners: Research Funding; Incyte: Research Funding; Johns Hopkins University: Other: Grants and/or provision of Investigational Medicinal Product; Sanofi: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other, Research Funding; Dietmar-Hopp-Foundation: Other: Grants and/or provision of Investigational Medicinal Product:. Weisel:Abbvie: Consultancy, Honoraria; Adaptive: Consultancy, Honoraria; GlaxoSmithKline: Honoraria; Janssen: Consultancy, Honoraria, Research Funding; Roche: Consultancy, Honoraria; Sanofi: Consultancy, Honoraria, Research Funding; Bristol-Myers Squibb: Consultancy, Honoraria; Amgen: Consultancy, Honoraria, Research Funding; Celgene: Consultancy, Honoraria, Research Funding; Karyopharm: Consultancy, Honoraria; Takeda: Consultancy, Honoraria. OffLabel Disclosure: Encorafenib and Binimetinib in BRAF V600E mutant multiple myeloma

Despite major advances in the treatment of multiple myeloma (MM), it remains a largely incurable disease with long-term control often dependent on continuous therapy. More effective, better tolerated treatments are therefore required to achieve durable remissions and to improve the quality of life of MM patients. Adoptive immunotherapy employing T cells expressing chimeric antigen receptors (CAR) is currently among the most promising treatment approaches in cancer. Within the target portfolio for MM immunotherapy, B-cell maturation antigen (BCMA) is among the most widely studied target antigens. BCMA is consistently expressed on MM cells and, importantly, is not expressed in critical healthy tissue. For this reason, it is an ideal target for MM immunotherapy. Several clinical trials evaluating different BCMA-targeting CAR constructs have been initiated and early results are very promising. However, in this rapidly developing clinical landscape, the ultimate role of BCMA-specific CAR-T cell therapy remains unclear. In this review, we will summarize currently available clinical data on BCMA-directed CAR-T cells and discuss potential future perspective for this promising treatment approach in MM.

Introduction: Despite improvements in the prognosis of multiple myeloma (MM), most patients ultimately relapse and undergo multiple lines of therapy. Due to the immunocompromising effects of virtually all anti-myeloma agents as well as the disease itself, infections are a frequent complication during therapy and the most important cause of mortality in patients with MM. Establishment of clear predictors of infectious complications, especially under therapy with novel agents, is therefore of major clinical importance to identify patients at risk and to guide anti-infective prophylaxis. Methods: In this prospective, observational cohort study we examined the development of CD4+ T-cell numbers during anti-myeloma therapies which were based on the novel agents daratumumab, carfilzomib, elotuzumab, or pomalidomide and their impact on infectious complications in 96 patients with relapsed/refractory MM (median prior lines of therapy: 2 [1-13], median age: 70 years of age [42-90]). Data on infectious events including CTC-AE severity grading, antimicrobial prophylaxis strategies and vaccination status was collected before start of therapy, after 3 months and after 6 months of therapy. Flow cytometry was used to identify T-cell subsets at all three timepoints. Results: Before start of therapy, 25 patients (26%) had CD4+ cell counts < 200/µl, 75 patients (78%) had CD4+ cell counts < 500/µl. In a multivariate linear regression model the number of previous lines of therapy had a significant negative impact on CD4+-cell numbers at start of relapse therapy (p=0.03), whereas age and active therapy within in the last 6 months did not. With regard to relapse therapy, both pomalidomide and carfilzomib led to a significant reduction in CD4+ cell count after 3 months of therapy (p=0.03 and p= 0.04, resp.) in a multivariate linear regression model. This effect was not noticeable in treatments based on daratumumab. In a multivariate logistic regression analysis with regard to the occurrence of infections ≥ CTC II° within the first 3 cycles of therapy, CD4+ cell count at start of relapse therapy was the only predictor with borderline statistical significance (p=0.06). Conclusions: A significant proportion of patients with relapsed refractory MM show a severe reduction of CD4+ T-cells already at start of relapse therapy, especially after multiple lines of therapy. CD4+ cell count at start of relapse therapy might indicate an increased risk of infectious complications. Additional studies with a larger number of patients are warranted to further elucidate the impact of CD4+ cell count at start of relapse therapy as a predictor of infectious complications in MM and whether it might serve to better identify patients at risk of infectious complications and steer antimicrobial prophylaxis strategies. Disclosures John: Proteona: Research Funding. Mueller-Tidow:Pfizer: Membership on an entity's Board of Directors or advisory committees, Research Funding; Daiichi Sankyo: Research Funding; Jose-Carreras-Siftung: Research Funding; Bayer AG: Research Funding; BiolineRx: Research Funding; Wilhelm-Sander-Stiftung: Research Funding; BMBF: Research Funding; Deutsche Krebshilfe: Research Funding; Janssen-Cilag Gmbh: Membership on an entity's Board of Directors or advisory committees; Deutsche Forschungsgemeinschaft: Research Funding. Jordan:priME Oncology: Speakers Bureau; Shire: Membership on an entity's Board of Directors or advisory committees; G1 Therapeutics: Membership on an entity's Board of Directors or advisory committees; Pfizer: Membership on an entity's Board of Directors or advisory committees; Voluntis: Membership on an entity's Board of Directors or advisory committees; Pomme-med: Speakers Bureau; Hexal: Speakers Bureau; Merck: Membership on an entity's Board of Directors or advisory committees; Merck Sharp & Dome: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; medupdate: Speakers Bureau; Helsinn: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Tesaro: Membership on an entity's Board of Directors or advisory committees; ClinSolResearch: Membership on an entity's Board of Directors or advisory committees; Riemser: Research Funding, Speakers Bureau; Amgen: Speakers Bureau; Kreussler: Membership on an entity's Board of Directors or advisory committees; art-tempi: Speakers Bureau. Goldschmidt:Dietmar-Hopp-Foundation: Other: Grants and/or provision of Investigational Medicinal Product:; BMS: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Grants and/or provision of Investigational Medicinal Product:, Research Funding; Incyte: Research Funding; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Grants and/or provision of Investigational Medicinal Product:, Research Funding; Sanofi: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other, Research Funding; Johns Hopkins University: Other: Grants and/or provision of Investigational Medicinal Product; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Grants and/or provision of Investigational Medicinal Product:, Research Funding; Novartis: Honoraria, Research Funding; Mundipharma GmbH: Research Funding; Takeda: Membership on an entity's Board of Directors or advisory committees, Research Funding; Molecular Partners: Research Funding; Merck Sharp and Dohme (MSD): Research Funding; University Hospital Heidelberg, Internal Medicine V and National Center for Tumor Diseases (NCT), Heidelberg, Germany: Current Employment; GlaxoSmithKline (GSK): Honoraria; Adaptive Biotechnology: Membership on an entity's Board of Directors or advisory committees; Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Grants and/or provision of Investigational Medicinal Product, Research Funding; Chugai: Honoraria, Other: Grants and/or provision of Investigational Medicinal Product:, Research Funding. Raab:Heidelberg Pharma: Research Funding; Amgen: Membership on an entity's Board of Directors or advisory committees; Takeda: 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; Janssen: Membership on an entity's Board of Directors or advisory committees; Sanofi: Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding.

Introduction: Treatments incorporating autologous transplantation (ASCT), proteasome inhibitors (PIs), and immunomodulatory drugs (IMIDs) induce deep and durable remissions in most multiple myeloma (MM) patients, resulting in prolonged survival. Yet, patients who suffer from early relapse within 2 years of treatment initiation or become refractory to PIs and IMIDs still have a dismal outcome. The mutational landscape in early relapsed MM (ERMM) and relapsed/refractory MM (RRMM) has been comprehensively described. Several aberrations are associated with these two types of high-risk disease but little is known about the biological difference between them. To this end, we have comparatively and sequentially analyzed whole genome and RNA sequencing data from ERMM and RRMM patients. Methods: We included 32 patients who had relapsed within 2 years of first-line therapy (ERMM group, 30 after ASCT). Samples were collected at first relapse. Paired baseline samples were available from 17 patients. For the RRMM group, we included 43 patients with a median of 5 prior lines of therapy (range 2 - 13; 88% with ASCT), who had relapsed after PIs and IMiDs. For 22 of them consecutive tumor samples were available. Sequencing data were pre-processed using in-house pipelines. Mutations, indels, translocations, and copy number variants were called using Platypus, SOPHIA and ACESeq. Mutational signatures were identified with MMSig and subclonal structures with SciClone. Differential gene expression was assessed using DESeq, gene set enrichment analysis was performed with hypeR, and gene fusions were detected with Arriba. Results: Nonsynonymous mutations occurred more frequently in RRMM (median=180) compared to ERMM at first relapse (median=62, p Conclusions: According to our results ERMM and RRMM are biologically distinct entities of MM. While ERMM is characterized by inactivation of tumor suppressors and upregulation of gene sets associated with hypoxia and glycolysis, RRMM shows mutations in multiple gene networks, upregulation of ribosomal protein pseudogenes with unknown function and a signature linked to defective DNA repair, suggesting multifactorial mechanisms that lead from first relapse to end-stage relapsed refractory disease. Comparing paired samples, we did not observe major difference in evolution patterns between ERMM and RRMM. Yet, the low prevalence of the melphalan MM1 signature in ERMM suggests selection of pre-existing clones in this entity. In contrast, single tumor cells exposed to melphalan are often the precursors of clones dominating at the RRMM stage, indicating that first-line ASCT has a long-term effect on MM evolution. Disclosures John: Proteona: Research Funding. Mueller-Tidow:Janssen-Cilag Gmbh: Membership on an entity's Board of Directors or advisory committees; Deutsche Forschungsgemeinschaft: Research Funding; Deutsche Krebshilfe: Research Funding; Daiichi Sankyo: Research Funding; Pfizer: Membership on an entity's Board of Directors or advisory committees, Research Funding; BiolineRx: Research Funding; Bayer AG: Research Funding; Jose-Carreras-Siftung: Research Funding; Wilhelm-Sander-Stiftung: Research Funding; BMBF: Research Funding. Goldschmidt:Johns Hopkins University: Other: Grants and/or provision of Investigational Medicinal Product; Sanofi: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other, Research Funding; Incyte: Research Funding; Molecular Partners: Research Funding; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Grants and/or provision of Investigational Medicinal Product:, Research Funding; Novartis: Honoraria, Research Funding; Takeda: Membership on an entity's Board of Directors or advisory committees, Research Funding; Mundipharma GmbH: Research Funding; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Grants and/or provision of Investigational Medicinal Product:, Research Funding; BMS: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Grants and/or provision of Investigational Medicinal Product:, Research Funding; University Hospital Heidelberg, Internal Medicine V and National Center for Tumor Diseases (NCT), Heidelberg, Germany: Current Employment; GlaxoSmithKline (GSK): Honoraria; Adaptive Biotechnology: Membership on an entity's Board of Directors or advisory committees; Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Grants and/or provision of Investigational Medicinal Product, Research Funding; Chugai: Honoraria, Other: Grants and/or provision of Investigational Medicinal Product:, Research Funding; Dietmar-Hopp-Foundation: Other: Grants and/or provision of Investigational Medicinal Product:; Merck Sharp and Dohme (MSD): Research Funding. Raab:Bristol-Myers Squibb: Membership on an entity's Board of Directors or advisory committees; Takeda: Membership on an entity's Board of Directors or advisory committees; Heidelberg Pharma: Research Funding; Sanofi: Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding; Janssen: Membership on an entity's Board of Directors or advisory committees; Amgen: Membership on an entity's Board of Directors or advisory committees.

Introduction: Multiple myeloma (MM) is a heterogeneous malignancy of clonal plasma cells that accumulate in the bone marrow (BM). Despite new treatment approaches, in most patients resistant subclones are selected by therapy, resulting in the development of refractory disease. While the subclonal architecture in newly diagnosed patients has been investigated in great detail, intra-tumor heterogeneity in relapsed/refractory (RR) MM is poorly characterized. Recent technological and computational advances provide the opportunity to systematically analyze tumor samples at single-cell (sc) level with high accuracy and througput. Here, we present a pilot study for an integrative analysis of sc Assay for Transposase-Accessible Chromatin with high-throughput sequencing (scATAC-seq) and scRNA-seq with the aim to comprehensively study the regulatory landscape, gene expression, and evolution of individual subclones in RRMM patients. Methods: We have included 20 RRMM patients with longitudinally collected paired BM samples. scATAC- and scRNA-seq data were generated using the 10X Genomics platform. Pre-processing of the sc-seq data was performed with the CellRanger software (reference genome GRCh38). For downstream analyses the R-packages Seurat and Signac (Satija Lab) as well as Cicero (Trapnell Lab) were used. For all patients bulk whole genome sequencing (WGS) data was available, which we used for confirmatory studies of intra-tumor heterogeneity. Results: A comprehensive study at the sc level requires extensive quality controls (QC). All scATAC-seq files passed the QC, including the detected number of cells, number of fragments in peaks or the ratio of mononucleosomal to nucleosome-free fragments. Yet, unsupervised clustering of the differentially accessible regions resulted in two main clusters, strongly associated with sample processing time. Delay of sample processing by 1-2 days, e.g. due to shipment from participating centers, resulted in global change of chromatin accessibility with more than 10,000 regions showing differences compared to directly processed samples. The corresponding scRNA-seq files also consistently failed QC, including detectable genes per cell and the percentage of mitochondrial RNA. We excluded these samples from the study. Analysing scATAC-seq data, we observed distinct clusters before and after treatment of RRMM, indicating clonal adaptation or selection in all samples. Treatment with carfilzomib resulted in highly increased co-accessibility and >100 genes were differentially accessible upon treatment. These genes are related to the activation of immune cells (including T-, and B-cells), cell-cell adhesion, apoptosis and signaling pathways (e.g. NFκB) and include several chaperone proteins (e.g. HSPH1) which were upregulated in the scRNA-seq data upon proteasome inhibition. The power of our comprehensive approach for detection of individual subclones and their evolution is exemplarily illustrated in a patient who was treated with a MEK inhibitor and achieved complete remission. This patient showed two main clusters in the scATAC-seq data before treatment, suggesting presence of two subclones. Using copy number profiles based on WGS and scRNA-seq data and performing a trajectory analysis based on scATAC-seq data, we could confirm two different subclones. At relapse, a seemingly independent dominant clone emerged. Upon comprehensive integration of the datasets, one of the initial subclones could be identified as the precursor of this dominant clone. We observed increased accessibility for 108 regions (e.g. JUND, HSPA5, EGR1, FOSB, ETS1, FOXP2) upon MEK inhibition. The most significant differentially accessible region in this clone and its precursor included the gene coding for krüppel-like factor 2 (KLF2). scRNA-seq data showed overexpression of KLF2 in the MEK-inhibitor resistant clone, confirming KLF2 scATAC-seq data. KLF2 has been reported to play an essential role together with KDM3A and IRF1 for MM cell survival and adhesion to stromal cells in the BM. Conclusions: Our data strongly suggest to use only immediately processed samples for single cell technologies. Integrating scATAC- and scRNA-seq together with bulk WGS data showed that detection of individual clones and longitudinal changes in the activity of cis-regulatory regions and gene expression is feasible and informative in RRMM. Disclosures Goldschmidt: John-Hopkins University: Research Funding; Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding; John-Hopkins University: Research Funding; Bristol-Myers Squibb: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Mundipharma: Research Funding; Takeda: Membership on an entity's Board of Directors or advisory committees, Research Funding; MSD: Research Funding; Molecular Partners: Research Funding; Dietmar-Hopp-Stiftung: Research Funding; Janssen: Consultancy, Research Funding; Chugai: Honoraria, Research Funding; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Sanofi: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Amgen: Consultancy, Research Funding; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Adaptive Biotechnology: Membership on an entity's Board of Directors or advisory committees.

Background: Various treatment regimen in multiple myeloma (MM) are based on proteasome inhibition (PI). Although effective at therapy start, most patients relapse and develop drug resistance over time. To better understand the molecular underpinnings associated with PI resistance, we studied genetic and epigenetic alterations of the 26S proteasome genes in PI exposed patients. Methods: We performed a meta-analysis comprised of M3P targeted sequencing datasets and other publicly available WGS/WES sets. A selection of most frequently found mutations was tested in vitro regarding their impact on PI response. DNA promoter methylation of a subset of proteasome genes was determined by targeted Deep Bisulfite Sequencing (DBS), followed up on expression (Taqman qPCR) and validated at functional level (dual-luciferase reporter assay system). Results: The meta-analysis was conducted for a total of 1,752 MM cases, with 1,241 newly diagnosed (NDMM) and 511 progressed MM (PMM) samples. We identified mutations in 32 proteasome genes, with increased incidence from NDMM (6.1% of the patients had mutations in one or more genes) to 10.2% at PMM. Besides PSMB5 encoding for the inhibitor binding site, mainly 19S subunit genes were mutated in areas that impact the recognition of ubiquitinated proteins (PSMD1 and PSMD2), are involved in protein unfolding or gate opening (PSMC1-6). We stably expressed proteasome subunit components bearing frequently observed patient-derived mutations in RPMI-8226 MM cells. All mutants (PSMC6 R242Q, PSMD1 E824K, PSMD1 A887T, PSMD2 M646I, PSMC2 Y429S) displayed an impaired PI response towards Bortezomib (Figure A), Carfilzomib and Ixazomib. Of note, in a fluorescent based, in house clonal competition assay, Bortezomib resistant PSMB5 A20T mutants were outcompeted by WT cells when the drug was removed from co-culture, demonstrating a survival disadvantage through the mutation itself, when no selective pressure of proteasome inhibition was applied. In general, somatic mutations on single gene level were relatively rare, PSMD1, our best candidate gene, was mutated in only 2% of the analyzed MM patients, the remaining genes even to an lower extent, but the proteasome as a whole structure, was frequently affected by mutations. Therefore, we hypothesized that clonal evolution might also act by selecting epigenetic alterations. To address this, we analyzed promoter methylation of PSMC2, PSMC5, PSMC6, PSMD1 and PSMD5 in 42 MM patients by DBS. For PSMD5, NDMM patients and PBMCs were nearly unmethylated (mean methylation: 2.0%±0.020 and 2.0%±0.026), but PMM displayed noticeably increased hypermethylation (6%±0.099). We demonstrated epigenetic silencing by promoter hypermethylation (methylation degree ≥15%) in 20% of PI resistant patients. Moreover, at RNA level we confirmed that patients with high methylation had low expression of PSMD5 and vice versa. To explore the regulatory impact of PSMD5 promoter methylation on gene regulation, we now cloned our amplicon into the backbone of a CpG-free vector (pCpGL). The reporter vector with either the methylated or the unmethylated insert was co-transfected with a Renilla control vector into L363 cells. Luciferase activity of the unmethylated PSMD5 construct was 8 times increased compared to the methylated vector and the controls (vector without insert and non-transfected cells) (Figure B), confirming gene regulation through methylation of this gene. PSMD5, encodes a chaperon recently characterized as the main regulator of 19S proteasome assembly. Gene silencing may represent an adaptive way of cancer cells to bypass proteasome inhibition and escape PI induced proteolytic toxicity by increasing their protein turnover capacity. Conclusion: Altogether our data give evidence that after PI exposition, MM patients harbor acquired regulatory DNA mutations as well as epimutations that affect different proteasomal subunits and, by different modes of action, compromise proteasome activity to escape PI therapy. Figure Disclosures Bittrich: German Research Foundation (DFG): Other: N/A; University of Würzburg: Other: N/A; Bristol Myers Squibb: Research Funding; Otsuka Pharmaceuticals Europe: Other: N/A; Pfizer: Other: Travel Funding; Wilhelm Sander Foundation: Research Funding; Else Kröner Fresenius Foundation: Research Funding; Celgene: Other: Travel Funding, Research Funding; JAZZ Pharmaceuticals: Other: Travel Funding; AMGEN: Other: Travel Funding; University Hospital Wuerzburg: Employment; SANOFI Aventis: Membership on an entity's Board of Directors or advisory committees, N/A, Research Funding.

Introduction: Despite significant improvements in therapy during the last decade, most multiple myeloma (MM) patients develop refractory disease over time. Treatment of refractory MM is a major challenge, likely due to the still poorly characterized inter- and intratumor heterogeneity at this stage of the disease, and the complex interplay of MM cells with the microenvironment (ME). In particular, there is an urgent need to unravel how these features of MM are linked to molecular mechanisms of drug resistance. Methods: We resolved the cellular composition, underlying transcriptional inter- and intra-patient heterogeneity and molecular treatment response of relapsed/refractory MM by single cell RNA sequencing (scRNA-seq). Using droplet-based microfluidics, ~230,000 single cell gene expression profiles from bone marrow (BM) aspirates of 21 patients sorted into CD138+and CD138- fractions were acquired, allowing for a comprehensive analysis of both MM cells as well as their ME. Patients had a median of 4 prior lines of therapy including both a proteasome inhibitor and an immunomodulator and were refractory to their immediate prior line of therapy at time of sampling. In addition, paired samples before either pomalidomide- or carfilzomib-based therapies were analyzed for 16/21 patients. Genomic aberrations in individual patients were mapped by interphase fluorescence in situ hybridization. Cells were clustered and CD138+ MM subtypes as well as immune cell-types of the ME were identified from their single cell transcriptomes and a copy number variation (CNV) analysis. As a reference for non-malignant cells and to construct a developmental B-cell trajectory the Human Cell Atlas BM scRNA-seq reference dataset was used. To characterize interactions of MM cells with their ME, the correlated expression of ligand-receptor pairs was exploited. Results: The analysis of inter- and intra-tumor heterogeneity of molecular MM subgroups revealed distinct transcriptome signatures with contributions that could be assigned to differences in heavy and light chain immunoglobulin expression as well as known genomic alterations, including t(11;14), t(4;14) and hyperdiploidy. MM cells from individual patients largely maintained a plasma cell specific gene expression profile but a partial loss of plasma cell identity was detected based on mapping to a developmental B-cell trajectory. It was characterized by the upregulation of subgroup transcriptome signatures associated with earlier stages of B-cell development in almost 50% of patients, such as a pre-B or mature B cell-like phenotype. Within individual samples, subclonal MM cell populations with specific gene expression programs were resolved based on the CNV analysis and included those characterized by expression of the immune-activator CD27 and the modulator of WNT signaling FRZB. The analysis of longitudinally collected samples revealed both changes in the cell subtype cluster structure as well as drug-specific adaptation of gene expression programs in distinct subpopulations persisting or emerging at relapse. These profile changes were characterized by e.g. downregulation of Myc target genes upon pomalidomide treatment or induction of heat shock proteins under carfilzomib. Within the ME of refractory MM patients, we observed that the fraction of B cells and CD4+ T cells was strongly reduced while CD14+ and CD16+ monocytes as well as dendritic cells expanded. Notably, the immune checkpoint protein PD-1H (aka VISTA) that inhibits T cell activation was highly expressed in cell types from the myeloid compartment in contrast to healthy donors. Further, a ligand-receptor analysis revealed that MM cells displayed the strongest interactions with monocytes, which were mediated by MIF, BAFF and other cytokines. Conclusions: Our study demonstrates the value of scRNA-seq analysis for identifying crucial transcriptome features that classify refractory MM subtypes and their evolution in response to treatment including regulation of drug resistance associated signaling pathways. Our data suggest that refractory MM cells shape the myeloid compartment in the BM to generate an immune suppressive ME. Understanding the evolution of MM cell heterogeneity and the bone marrow milieu in refractory disease will lead to novel treatment approaches and eventually improve patient outcome. Disclosures Müller-Tidow: MSD: Membership on an entity's Board of Directors or advisory committees. Goldschmidt:John-Hopkins University: Research Funding; Molecular Partners: Research Funding; Amgen: Consultancy, Research Funding; Sanofi: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; MSD: Research Funding; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding; Dietmar-Hopp-Stiftung: Research Funding; Janssen: Consultancy, Research Funding; Takeda: Membership on an entity's Board of Directors or advisory committees, Research Funding; John-Hopkins University: Research Funding; Chugai: Honoraria, Research Funding; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Adaptive Biotechnology: 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, Research Funding; Mundipharma: Research Funding.

Introduction: Treatment strategies incorporating proteasome inhibitors, immunomodulators, and autologous transplantation induce durable remissions in most newly diagnosed multiple myeloma (NDMM) patients. However, for 20% of patients even the most intensive therapies have not resulted in satisfactory outcomes. Currently available risk scores do not fully appreciate the complex biology of MM and have limited sensitivity and/or specificity for identification of high risk (HR) disease. We therefore aimed to characterize the mutational landscape of transplant-eligible NDMM patients who relapsed within 2 years after treatment initiation, thereby defining true clinical HRMM. To elucidate the clonal structure and evolution in these patients, we performed deep whole genome sequencing (WGS, ~80x) and RNAseq of samples collected at baseline and first relapse. Methods: We included 34 transplanted NDMM patients who experienced early relapse during maintenance within 2 years after treatment initiation. Tumor samples were collected from 20 and 31 patients at baseline and first relapse, respectively. Paired samples taken at both time points were available from 17 patients. WGS and RNAseq data were pre-processed using in-house pipelines. Single nucleotide variants (SNVs), indels, translocations, and copy number variants (CNVs) were called using Platypus, SOPHIA and ACESeq. Subclones were identified using SciClone. RNAseq data was aligned using STAR. Fusion genes were called by Arriba. Differential gene expression was assessed using DESeq2. Results: At baseline, only 12/20 patients would have been classified as HR according to conventional markers, including presence of t(4;14), t(14;16), amp(1q), clonal del(17p) or ISS3. In 5 patients del(17p) was solely observed in a minor sublone, which was selected during treatment and became dominant at relapse in 3 of them. Selection of amp(1q)-positive subclones was seen in 2 patients, illustrating that subclonal amp(1q) or del(17p) are frequent events in HR patients, and - in contrast to recent results - could contribute to early relapse. Translocations involving MYC have also been reported to be of prognostic impact. At baseline 9 of 20 patients were positive for this event, with BMP6 and the lambda locus being the translocation partner in 2 patients each. At relapse we found an additional MYC-lambda, and two MYC-kappa translocations, supporting recent observations that MYC-light chain translocations are associated with aggressive disease. We identified a median of 40 (range: 17-233) nonsilent somatic SNVs per patient at baseline and 61 (range: 14-322) at relapse. Yet, comparing paired samples there was no significant increase in SNVs. In our HRMM set, 21 of 64 recently identified driver genes were mutated at baseline with KRAS (n = 6), TP53 (n = 6), NRAS (n = 2), and DIS3 (n = 2) being the most frequently affected genes. 6 of them - ACTG1, DIS3, FAM46C, NFKB2, RB1, and TRAF3 - were involved in fusion genes. At relapse the number of mutated driver genes increased to 29, and 10 of 31 patients presented with a clonal TP53 mutation. All patients with a TP53 mutation also showed deletion of the second allele or LOH. Including other tumor suppressor genes, such as RB1, CDKN2C, or TRAF3, 12/20 NDMM and 20/31 relapsed patients had at least one bi-allelic aberration, doubling the number of HR patients with such events compared to considering TP53 alone. Longitudinally, we observed all patterns of clonal evolution that were recently described for unselected patients. Stable evolution was primarily seen in patients achieving partial remission, supporting a model where some tumor cells survive in a protective microenvironment (ME). In deep responders, however, branching evolution was the dominant patterns. This observation rather supports strong cell-intrinsic mechanisms and rapid selection of aggressive minor subclones in clinically defined HRMM. Conclusions: Understanding the mutational landscape in HRMM and drivers of early relapse is crucial in order to improve treatment options. Our study highlights the importance of bi-allelic events in HR and suggests that focusing on TP53 is not sufficient, if all HR cases are to be identified. Of note, 3 patients in the entire cohort would have been classified as low risk by conventional risk scores and even at relapse did not carry any bi-allelic event, indicating the existence of unknown somatic HR aberrations or a protective ME. Disclosures Müller-Tidow: MSD: Membership on an entity's Board of Directors or advisory committees. Goldschmidt:MSD: Research Funding; Sanofi: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Chugai: Honoraria, Research Funding; Mundipharma: Research Funding; Takeda: Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding; Janssen: Consultancy, Research Funding; Amgen: Consultancy, Research Funding; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Molecular Partners: Research Funding; Dietmar-Hopp-Stiftung: Research Funding; John-Hopkins University: Research Funding; Adaptive Biotechnology: 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, Research Funding; John-Hopkins University: Research Funding.