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As part of a phase 1/2 study, this single-arm expansion cohort established the efficacy and safety of mosunetuzumab monotherapy in patients with relapsed/refractory (R/R) diffuse large B-cell lymphoma (DLBCL) (received >=2 prior lines of therapy). Intravenous mosunetuzumab was administered with cycle (C)1 step-up dosing for cytokine release syndrome (CRS) mitigation: C1 day (D) 1: 1 mg; C1D8 2 mg; C1D15 and C2D1: 60 mg; C3 + D1: 30 mg. Hospitalization was not mandatory. Patients with complete response (CR) completed treatment after C8; those with partial response or stable disease continued treatment for a total of 17 cycles. The primary endpoint was CR rate (best response) by Independent Review Facility, assessed against a historical control CR rate (20%). Eighty-eight patients (73.9% de-novo DLBCL; 26.1% transformed follicular lymphoma) were enrolled; all had received prior anthracycline and anti-CD20 therapy. Overall response and CR rates were 42.0% (95% confidence interval [CI], 31.6-53.1) and 23.9% (95% CI, 15.4-34.1, respectively; CR rate did not reach statistical significance versus the historical control [P = 0.36]). Median time to first response was 1.4 months. Median progression-free survival was 3.2 months (95% CI: 2.2, 5.3). The CR rate in 26 patients who received prior CAR-T therapy was 12%. CRS was one of the most common adverse events (26.1% of patients); predominantly grade 1 to 2 and primarily in C1. Four patients (4.5%) discontinued mosunetuzumab due to adverse events. Mosunetuzumab demonstrated notable efficacy and a manageable safety profile in patients with R/R DLBCL, including those previously treated with CAR-Ts.

Supplementary Methods, Supplementary References, Supplementary Figure 1 - in vitro analysis of various BET inhibitors against Eu-myc lymphoma cells and effect of JQ1 on OPM2 and OPM2/BCL2 cells; Supplementary Figure 2 - In vitro effects of JQ1 on OPM2 and OPM2/BCL2 cells; Supplementary Figure 3 - In vivo effects of JQ1 showing lack of toxicity; Supplementary Figure 4 - induction of Bim in JQ1-sensitive and JQ1-resistant Eu-myc lymphomas; Supplementary Figure 5 - Activated Ras confers resistance to JAK inhibitor and JQ1.

Purpose:Targeting Bcl-2 family members upregulated in multiple cancers has emerged as an important area of cancer therapeutics. While venetoclax, a Bcl-2–selective inhibitor, has had success in the clinic, another family member, Bcl-xL, has also emerged as an important target and as a mechanism of resistance. Therefore, we developed a dual Bcl-2/Bcl-xL inhibitor that broadens the therapeutic activity while minimizing Bcl-xL–mediated thrombocytopenia.Experimental Design:We used structure-based chemistry to design a small-molecule inhibitor of Bcl-2 and Bcl-xL and assessed the activity against in vitro cell lines, patient samples, and in vivo models. We applied pharmacokinetic/pharmacodynamic (PK/PD) modeling to integrate our understanding of on-target activity of the dual inhibitor in tumors and platelets across dose levels and over time.Results:We discovered AZD4320, which has nanomolar affinity for Bcl-2 and Bcl-xL, and mechanistically drives cell death through the mitochondrial apoptotic pathway. AZD4320 demonstrates activity in both Bcl-2– and Bcl-xL–dependent hematologic cancer cell lines and enhanced activity in acute myeloid leukemia (AML) patient samples compared with the Bcl-2–selective agent venetoclax. A single intravenous bolus dose of AZD4320 induces tumor regression with transient thrombocytopenia, which recovers in less than a week, suggesting a clinical weekly schedule would enable targeting of Bcl-2/Bcl-xL–dependent tumors without incurring dose-limiting thrombocytopenia. AZD4320 demonstrates monotherapy activity in patient-derived AML and venetoclax-resistant xenograft models.Conclusions:AZD4320 is a potent molecule with manageable thrombocytopenia risk to explore the utility of a dual Bcl-2/Bcl-xL inhibitor across a broad range of tumor types with dysregulation of Bcl-2 prosurvival proteins.

Figure S6

contains methods.

Translocations of the mixed lineage leukemia (MLL) gene occur in 60% to 80% of all infant acute leukemias and are markers of poor prognosis. MLL-AF9 and other MLL fusion proteins aberrantly recruit epigenetic regulatory proteins, including histone deacetylases (HDAC), histone methyltransferases, bromodomain-containing proteins, and transcription elongation factors to mediate chromatin remodeling and regulate tumorigenic gene expression programs. We conducted a small-molecule inhibitor screen to test the ability of candidate pharmacologic agents targeting epigenetic and transcriptional regulatory proteins to induce apoptosis in leukemic cells derived from genetically engineered mouse models of MLL-AF9–driven acute myeloid leukemia (AML). We found that the CDK inhibitor dinaciclib and HDAC inhibitor panobinostat were the most potent inducers of apoptosis in short-term in vitro assays. Treatment of MLL-rearranged leukemic cells with dinaciclib resulted in rapidly decreased expression of the prosurvival protein Mcl-1, and accordingly, overexpression of Mcl-1 protected AML cells from dinaciclib-induced apoptosis. Administration of dinaciclib to mice bearing MLL-AF9–driven human and mouse leukemias elicited potent antitumor responses and significantly prolonged survival. Collectively, these studies highlight a new therapeutic approach to potentially overcome the resistance of MLL-rearranged AML to conventional chemotherapies and prompt further clinical evaluation of CDK inhibitors in AML patients harboring MLL fusion proteins. Cancer Res; 76(5); 1158–69. ©2015 AACR.

Utilising tissue whole exome sequencing (WES) and circulating tumor cell-free DNA (ctDNA), this Australasian Leukaemia & Lymphoma Group (ALLG) translational study sought to characterise primary and acquired molecular determinants of response and resistance of MZL to zanubrutinib for patients treated on the MAGNOLIA clinical trial. WES was performed on baseline tumor samples obtained from 18 patients. For seven patients, ctDNA was interrogated using a bespoke hybrid-capture next-generation sequencing (NGS) assay for 48 targeted genes. Somatic mutations were correlated with objective response data and survival analysis using Fisher's exact test and Kaplan-Meier (log-rank) method respectively. Baseline WES identified mutations in 33/48 (69%) prioritised genes. NFkB, NOTCH or BCR pathway genes were implicated in samples for 16/18 (89%) patients. KMT2D mutations (n=11) were most common followed by FAT1 (n=9), NOTCH1, NOTCH2, TNFAIP3 (n=5) and MYD88 (n=4). MYD88 or TNFAIP3 mutations correlated with improved PFS (not reached (NR) vs 11.1 months, p: 0.008, HR: 0.09, 95% CI: 0.01-0.52); KMT2D mutations trended to worse PFS (PFS: 13.40 months vs NR, p: 0.05, HR 6.5, 95%CI: 1.00-37.78). Acquired resistance mutations PLCG2 (R665W/R742P) and BTK (C481Y/C481F) were detected in two patients whose disease progressed. A BTK E41K non-catalytic activating mutation was identified prior to treatment in one zanubrutinib-refractory patient. MYD88, TNFAIP3 and KMT2D mutations correlate with PFS in patients with rrMZL treated with zanubrutinib. Detection of acquired BTK and PLCG2 mutations in ctDNA while on therapy is feasible and may herald clinical disease progression. This trial was registered at https://anzctr.org.au/ as ACTRN12619000024145.

BH3 mimetics like venetoclax target prosurvival Bcl-2 family proteins and are important therapeutics in the treatment of hematological malignancies. We demonstrate that endogenous Bfl-1 expression can render preclinical lymphoma tumor models insensitive to Mcl-1 and Bcl-2 inhibitors. However, suppression of Bfl-1 alone was insufficient to fully induce apoptosis in Bfl-1–expressing lymphomas, highlighting the need for targeting additional prosurvival proteins in this context. Importantly, we demonstrated that cyclin-dependent kinase 9 (CDK9) inhibitors rapidly downregulate both Bfl-1 and Mcl-1, inducing apoptosis in BH3-mimetic–resistant lymphoma cell lines in vitro and driving in vivo tumor regressions in diffuse large B-cell lymphoma patient-derived xenograft models expressing Bfl-1. These data underscore the need to clinically develop CDK9 inhibitors, like AZD4573, for the treatment of lymphomas using Bfl-1 as a selection biomarker.

Background: Recent advances in the treatment of non-Hodgkin lymphoma (NHL) have transformed the landscape and provided significant benefits to patients. Novel agents that target CD19 and CD20 on B cells, such as bispecific T-cell engagers and chimeric antigen receptor T-cell (CAR-T) therapy, have demonstrated benefit for patients in the relapsed and refractory setting. However, these agents can often be associated with significant toxicity and there is a need for new therapies that can provide clinical benefit with a superior safety profile. Imvotamab is a novel CD20 x CD3 bispecific antibody utilizing an IgM backbone. This allows targeting of up to 10 CD20 binding sites for every CD3 site. In preclinical models, imvotamab demonstrated encouraging antitumor activity and stimulated T-cells in a more physiologic manner than IgG-based antibodies, which may reduce adverse events typically associated with T-cell engagers and CAR-T, such as CRS and neurotoxicity. Loncastuximab tesirine is a CD19-targeting antibody-drug conjugate approved by the US FDA and EMA for relapsed DLBCL after 2 lines of systemic therapy. Loncastuximab tesirine has shown activity in both DLBCL and FL. Combining therapies such as loncastuximab tesirine, which targets CD19 and induce apoptosis of cancer cells, with imvotamab’s ability to eliminate CD20+ tumor cells by engagement with T-cells, may improve treatment outcomes among patients with NHL via synergistic mechanisms of action. Methods: This study is a Phase 1/2, multicenter, single-arm clinical trial of imvotamab as monotherapy and in combination with loncastuximab tesirine for patients with relapsed/refractory NHL. Phase 1a Dose Escalation is complete with no DLTs or neurotoxicity AEs up to 1000mg dose titration. Phase 1b Combination will evaluate imvotamab and loncastuximab tesirine in patients with R/R 2nd line or later NHL. Phase 2 monotherapy Dose Selection is currently ongoing. The Phase 2 component randomizes patients at two different dose levels (100 mg and 300 mg plateau dose) in two separate indications (R/R DLBCL and R/R FL). Patients receive weekly dosing on Day 1, 8, and 15 of each 21- day cycle. Dosing begins at 15 mg and is increased weekly for 3-4 weeks to reach the plateau dose. Patients then stay at the plateau dose until disease progression or unacceptable toxicity. Patients who achieve a response by Week 12 may switch to a less frequent dosing interval of every 3 weeks. Primary endpoints include frequency and severity of adverse events and objective response rate (ORR) based on Lugano criteria. Correlative biomarker studies will evaluate the relationship of clinical benefit with blood and tissue biomarkers. The study is currently open with patients enrolling in Phase 2 at time of submission. Phase 1b Combination is expected to begin enrollment in the first quarter of 2023. Clinical trial information: NCT04082936. Citation Format: Catherine Diefenbach, Won Seog Kim, Chan Cheah, Ajay K. Gopal, Philippe Armand, Ian Flinn, Gareth P. Gregory, Sung-Soo Yoon, Loretta Nastoupil, Jennifer Lue, Vincent Ribrag, Javier Briones, Antonio Salar-Silvestre, Anna Sureda-Balari, Matthew Ku, Hans Cruz, Paul Thaler, Ibrahim Qazi, Rachel Wei, Maya Leabman, Genevive Hernandez, Iris Sison, Elizabeth Budde. A phase 1/2 randomized study of imvotamab monotherapy and in combination with loncastuximab tesirine in relapsed/refractory non-Hodgkin lymphomas [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr CT052.

Purpose: Targeting Bcl-2 family members upregulated in multiple cancers has emerged as an important area of cancer therapeutics. While venetoclax, a Bcl-2–selective inhibitor, has had success in the clinic, another family member, Bcl-xL, has also emerged as an important target and as a mechanism of resistance. Therefore, we developed a dual Bcl-2/Bcl-xL inhibitor that broadens the therapeutic activity while minimizing Bcl-xL–mediated thrombocytopenia. Experimental Design: We used structure-based chemistry to design a small-molecule inhibitor of Bcl-2 and Bcl-xL and assessed the activity against in vitro cell lines, patient samples, and in vivo models. We applied pharmacokinetic/pharmacodynamic (PK/PD) modeling to integrate our understanding of on-target activity of the dual inhibitor in tumors and platelets across dose levels and over time. Results: We discovered AZD4320, which has nanomolar affinity for Bcl-2 and Bcl-xL, and mechanistically drives cell death through the mitochondrial apoptotic pathway. AZD4320 demonstrates activity in both Bcl-2– and Bcl-xL–dependent hematologic cancer cell lines and enhanced activity in acute myeloid leukemia (AML) patient samples compared with the Bcl-2–selective agent venetoclax. A single intravenous bolus dose of AZD4320 induces tumor regression with transient thrombocytopenia, which recovers in less than a week, suggesting a clinical weekly schedule would enable targeting of Bcl-2/Bcl-xL–dependent tumors without incurring dose-limiting thrombocytopenia. AZD4320 demonstrates monotherapy activity in patient-derived AML and venetoclax-resistant xenograft models. Conclusions: AZD4320 is a potent molecule with manageable thrombocytopenia risk to explore the utility of a dual Bcl-2/Bcl-xL inhibitor across a broad range of tumor types with dysregulation of Bcl-2 prosurvival proteins.

Primary CNS lymphoma (PCNSL) in immunocompetent patients is a disease of older adults who are often unsuitable for the high dose therapy or experience substantial morbidity from whole brain radiotherapy. As therapeutic studies in older patients are limited, there is a need for real world data to guide patient care. Here we report a series of 38 consecutive immunocompetent patients with PCNSL treated with curative intent using R-MPV/Ara-C with omission of consolidative radiotherapy in older patients. Outcomes for patients aged60 years and60 years were similar with overall response rates of 100% vs 85%, (

Background In primary central nervous system lymphoma (PCNSL), venous thromboembolism (VTE) can cause significant morbidity and hinder chemotherapy delivery. Objectives To assess VTE incidence, timing and adequacy of inpatient and outpatient VTE prophylaxis in patients with PCNSL receiving chemoimmunotherapy with curative intent. Patients/Methods We reviewed patients diagnosed with PCNSL between 1997 and 2018 who received methotrexate, procarbazine, and vincristine ± Rituximab. Patient demographics, VTE prophylaxis and incidence, adverse events of anticoagulation, and survival outcomes were collected. Results Fifty‐one PCNSL patients were included (median 67 years [range, 32‐87], 30 males [59%]). Thirteen patients (25%, 95% confidence interval [CI], 14‐40) developed VTE at a median of 1.6 months from diagnosis (range, 0‐4). Patients with Khorana Risk Score ≥2 were more likely to have VTE than those with a KRS

Despite their availability for over a decade, the exact nature of biosimilar medicines is still poorly understood with paucity of clear treatment guidelines for their use in clinical practice in Australia. Although hematologists have had experience with biosimilars in the setting of supportive care, with the approval of the first biosimilar rituximab in hematological malignancies, it is important to revisit this topic. To inform the use of biosimilar medicines in clinical practice, we have developed a consensus statement from an Expert Panel of Australian hematologists, oncologists, and cancer pharmacists. These recommendations address the approach to use of biosimilar products in place of the corresponding reference medicine in a number of different clinical contexts. Our recommendations are based on the premise that biosimilar medicines can be considered therapeutically equivalent to their reference brand and used in a similar way to the reference product in any approved indication. We advocate for local approaches to the provision of patient information, dispensing of the intended brand and pharmacovigilance, to be developed in consultation with local hematologists and aim to improve confidence in the appropriate use of biosimilar medicines and their expected outcomes among hematologists.

Peripheral T-cell lymphoma (PTCL) is a rare, heterogenous malignancy with dismal outcomes at relapse. Hypomethylating agents (HMA) have an emerging role in PTCL, supported by shared mutations with myelodysplasia (MDS). Response rates to azacitidine in PTCL of follicular helper cell origin are promising. Guadecitabine is a decitabine analogue with efficacy in MDS. In this phase II, single-arm trial, PTCL patients received guadecitabine on days 1–5 of 28-day cycles. Primary end points were overall response rate (ORR) and safety. Translational sub-studies included cell free plasma DNA sequencing and functional genomic screening using an epigenetically-targeted CRISPR/Cas9 library to identify response predictors. Among 20 predominantly relapsed/refractory patients, the ORR was 40% (10% complete responses). Most frequent grade 3-4 adverse events were neutropenia and thrombocytopenia. At 10 months median follow-up, median progression free survival (PFS) and overall survival (OS) were 2.9 and 10.4 months respectively. RHOAG17V mutations associated with improved PFS (median 5.47 vs. 1.35 months; Wilcoxon p = 0.02, Log-Rank p = 0.06). 4/7 patients with TP53 variants responded. Deletion of the histone methyltransferase SETD2 sensitised to HMA but TET2 deletion did not. Guadecitabine conveyed an acceptable ORR and toxicity profile; decitabine analogues may provide a backbone for future combinatorial regimens co-targeting histone methyltransferases.

Primary central nervous system lymphoma is a clinicopathological disease entity that accounts for 1% of all non-Hodgkin lymphoma (NHL). Advanced patient age, adverse disease biology and complexities of diagnosis and treatment render outcomes markedly inferior to systemic NHL. Despite this, an increasing evidence base, including limited randomised controlled clinical trial data, is informing optimal therapeutic strategies with methotrexate-based induction chemotherapy schedules and intensified consolidation in selected patients. This practice statement represents an evidence-based review of the literature and has been devised to assist healthcare professionals in the diagnosis and management of this disease.

Background Relapsed/refractory (R/R) diffuse large B-cell lymphoma (DLBCL) is associated with a poor prognosis despite the availability of multiple treatment options. Preliminary evidence suggests that DLBCL may be responsive to programmed death ligand 1 (PD-L1)/programmed death 1 inhibitors. Objective The JAVELIN DLBCL study was conducted to assess whether a combination of agents could augment and sustain the antitumor immunity of avelumab, an anti-PD-L1 antibody, in R/R DLBCL. Methods This was a multicenter, randomized, open-label, parallel-arm study with a phase Ib and a phase III component. Reported here are the results from the phase Ib study, wherein 29 adult patients with DLBCL were randomized 1:1:1 to receive avelumab in combination with utomilumab (an immunoglobulin G2 4-1BB agonist) and rituximab (arm A), avelumab in combination with utomilumab and azacitidine (arm B), or avelumab in combination with bendamustine and rituximab (arm C). The primary endpoints were dose-limiting toxicities and objective response as assessed by the investigator per Lugano Response Classification criteria. Results Of the seven patients in arm A, one (14.3%) experienced two grade 3 dose-limiting toxicities (herpes zoster and ophthalmic herpes zoster); no dose-limiting toxicities were reported in arms B or C. No new safety concerns emerged for avelumab. One partial response was reported in arm A, three complete responses in arm C, and no responses in arm B. Given the insufficient antitumor activity in arms A and B and the infeasibility of expanding arm C, the study was discontinued before initiation of the phase III component. Conclusions The low level of clinical activity suggests that PD-L1 inhibitor activity may be limited in R/R DLBCL. ClinicalTrials.gov Identifier NCT02951156. Supplementary Information The online version contains supplementary material available at 10.1007/s11523-021-00849-8.

Preclinical data demonstrated that combining an anti–programmed cell death 1 (PD-1) inhibitor with a cyclin-dependent kinase 9 (CDK9) inhibitor provided enhanced antitumor activity with no significant toxicities, suggesting this combination may be a potential therapeutic option. The multicohort, phase 1 KEYNOTE-155 study evaluated the safety and antitumor activity of the PD-1 inhibitor pembrolizumab plus the CDK9 inhibitor dinaciclib in patients with relapsed or refractory (rr) chronic lymphocytic leukemia (CLL), diffuse large B-cell lymphoma (DLBCL) and multiple myeloma (MM). Patients enrolled were ≥18 years of age with a confirmed diagnosis of CLL, DLBCL, or MM. The study included 2 phases: a dose-evaluation phase to determine dose-limiting toxicities and a signal-detection phase. Patients received pembrolizumab 200 mg every 3 weeks plus dinaciclib 7 mg/m2 on day 1 and 10 mg/m2 on day 8 of cycle 1 and 14 mg/m2 on days 1 and 8 of cycles 2 and later. Primary endpoint was safety, and a key secondary endpoint was objective response rate (ORR). Seventy-two patients were enrolled and received ≥1 dose of study treatment (CLL, n = 17; DLBCL, n = 38; MM, n = 17). Pembrolizumab plus dinaciclib was generally well tolerated and produced no unexpected toxicities. The ORRs were 29.4% (5/17, rrCLL), 21.1% (8/38, rrDLBCL), and 0% (0/17, rrMM), respectively. At data cutoff, all 72 patients had discontinued treatment, 38 (52.8%) because of progressive disease. These findings demonstrate activity with combination pembrolizumab plus dinaciclib and suggest that a careful and comprehensive approach to explore anti–PD-1 and CDK9 inhibitor combinations is warranted. This trial was registered at www.clinicaltrials.gov as NCT02684617.

Sarit Assouline and Won Seog Kim contributed equally. Introduction: Follicular lymphoma (FL) is considered an indolent yet incurable disease characterized by recurrent relapses: disease-free intervals shorten, and refractoriness increases with each relapse. Patients (pts) with FL who have received at least two prior systemic therapies typically have a poor prognosis. This is particularly true for those who have progression of disease within 24 months of front-line treatment (POD24), or are refractory to multiple agent classes; such patients are left with limited treatment options. Mosunetuzumab is a full-length, fully humanized immunoglobulin G1 CD20/CD3 bispecific antibody that redirects T cells to engage and eliminate malignant B cells. GO29781 (NCT02500407) is an ongoing open-label, multicenter, Phase I/Ib, dose-escalation and expansion study evaluating the safety, efficacy and pharmacokinetics of mosunetuzumab in pts with relapsed/refractory (R/R) B-cell lymphoma. Here, we present updated clinical data from pts with R/R FL treated with mosunetuzumab after at least two prior systemic therapies. Methods: Data are presented from Group B, in which pts received intravenous mosunetuzumab monotherapy as step-up doses in Cycle 1 on Days 1 and 8 and the target dose administered on Day 15. Mosunetuzumab was given on Day 1 of each subsequent 21-day cycle for 8 cycles in pts with a complete response (CR), and up to 17 cycles in those with a partial response (PR) or stable disease (SD). Results: As of January 21, 2020, 62 pts with FL (with at least two prior systemic therapies), received mosunetuzumab at dose levels between 0.4/1.0/2.8mg and 1/2/13.5mg (Cycle 1 Day 1/8/15 dose levels). The median age was 59 (range 27-85) years, and median number of prior therapies was 3 (range 2-11). Thirty-three pts (53%) were refractory to both a prior anti-CD20 antibody and an alkylating agent (double refractory), 30 (48%) had POD24, and four (6%) had received prior chimeric antigen receptor T-cell (CAR-T) therapy. The overall response rate (ORR) was 68% (42/62), with 31 pts (50%) achieving CR (Figure). Consistent CR rates were observed in high-risk pt populations, including those with double refractory disease (18/33 [55%]), POD24 (16/30 [53%]), PI3Ki refractory (7/9 [78%]), and those who received prior CAR-T therapy (2/4 [50%]). With a median time on study of 14.4 months, 26 pts (62% of all responders; including 74% of pts who achieved CR) remained in remission at the data cut-off. The median duration of response (DOR) was 20.4 months (95% CI: 11.7 months, upper limit not reached) for all 42 responders. The median PFS was 11.8 months (95% CI: 7.3-21.9 months). Adverse events (AEs) were reported in 60 pts (97%); serious adverse events (SAE) were reported in 22 pts (35%). The most frequently reported (>10% of pts) grade (Gr) 3 or higher AEs included hypophosphatemia (23%; transient and clinically asymptomatic) and neutropenia (21%; with a low rate of febrile neutropenia [2%]). Overall, 14 pts (23%) experienced CRS; in four pts, CRS was classified as a SAE. CRS events were reversible, mostly of Gr 1 or 2 (Gr 1, n=11; Gr 2, n=2; Gr 3, n=1; Lee, et al. Blood 2014), and predominantly occurred during Cycle 1. No patient required tocilizumab, intensive care unit admission or use of vasopressors for CRS management. Neurologic AEs (NAEs; defined by any AEs reported as Preferred Terms in SOC Nervous System Disorders and SOC Psychiatric Disorders) were observed in 28 pts (45%); all were Gr 1 (n=18) or 2 (n=10). The most commonly reported NAEs were headache (24%), insomnia (15%) and dizziness (11%). No Gr ≥3 NAEs or serious NAEs were reported. Conclusions: Fixed-duration mosunetuzumab monotherapy results in high response rates and durable disease control with a tolerable safety profile in heavily pretreated patients with FL, including known high-risk subgroups. Updated pharmacodynamics and biomarker data will be presented at the meeting. Disclosures Assouline: BeiGene: Consultancy, Honoraria, Research Funding; AbbVie: Consultancy, Honoraria, Speakers Bureau; Janssen: Consultancy, Honoraria, Speakers Bureau; Takeda: Research Funding; Pfizer: Consultancy, Honoraria; F. Hoffmann-La Roche Ltd: Consultancy, Honoraria, Research Funding; AstraZeneca: Consultancy, Honoraria, Speakers Bureau. Kim:Mundipharma: Research Funding; Donga: Research Funding; Kyowa Kirn: Research Funding; Celltrion: Research Funding; JJ: Research Funding; Pfizer: Research Funding; F. Hoffmann-La Roche: Research Funding. Sehn:Genentech, Inc.: Consultancy, Honoraria, Research Funding; AstraZeneca: Consultancy, Honoraria; F. Hoffmann-La Roche Ltd: Consultancy, Honoraria, Research Funding; Seattle Genetics: Consultancy, Honoraria; Teva: Consultancy, Honoraria, Research Funding; Takeda: Consultancy, Honoraria; Servier: Consultancy, Honoraria; Chugai: Consultancy, Honoraria; Amgen: Consultancy, Honoraria; AbbVie: Consultancy, Honoraria; Apobiologix: Consultancy, Honoraria; Acerta: Consultancy, Honoraria; Merck: Consultancy, Honoraria; Janssen: Consultancy, Honoraria; Kite: Consultancy, Honoraria; Gilead: Consultancy, Honoraria; Karyopharm: Consultancy, Honoraria; Lundbeck: Consultancy, Honoraria; TG therapeutics: Consultancy, Honoraria; Verastem Oncology: Consultancy, Honoraria; Celgene: Consultancy, Honoraria; MorphoSys: Consultancy, Honoraria. Schuster:AlloGene, AstraZeneca, BeiGene, Genentech, Inc./ F. Hoffmann-La Roche, Juno/Celgene, Loxo Oncology, Nordic Nanovector, Novartis, Tessa Therapeutics: Consultancy, Honoraria; Novartis, Genentech, Inc./ F. Hoffmann-La Roche: Research Funding. Cheah:Celgene, F. Hoffmann-La Roche, Abbvie, MSD: Research Funding; Celgene, F. Hoffmann-La Roche, MSD, Janssen, Gilead, Ascentage Pharma, Acerta, Loxo Oncology, TG therapeutics: Honoraria. Nastoupil:Karus Therapeutics: Research Funding; Gilead/KITE: Honoraria; TG Therapeutics: Honoraria, Research Funding; Merck: Research Funding; Novartis: Honoraria, Research Funding; Gamida Cell: Honoraria; Bayer: Honoraria; Pfizer: Honoraria, Research Funding; LAM Therapeutics: Research Funding; Janssen: Honoraria, Research Funding; Celgene: Honoraria, Research Funding; Genentech, Inc.: Honoraria, Research Funding. Shadman:Fred Hutchinson / University of Washington: Current Employment; Abbvie, Genentech, Inc., AstraZeneca, Sound Biologics , Pharmacyclics, Verastem, ADC therapeutics, Beigene, Cellectar, BMS, Mophosys and Atara Biotherapeutics: Consultancy; Mustang Bio, Celgene, Pharmacyclics, Gilead, Genentech, Inc., Abbvie, TG therapeutics, Beigene, AstraZeneca, Sunesis: Research Funding. Yoon:Amgen: Consultancy, Honoraria; Novartis: Consultancy, Honoraria; Kyowahako Kirin: Research Funding; Janssen: Consultancy; F. Hoffmann-La Roche: Other: All authors received support for third-party writing assistance, furnished by Scott Battle, PhD, provided by F. Hoffmann-La Roche, Basel, Switzerland., Research Funding; YuhanPharma: Research Funding. Matasar:Daiichi Sankyo: Consultancy; IGM Biosciences: Research Funding; Immunovaccine Technologies: Honoraria, Research Funding; F. Hoffmann-La Roche Ltd: Consultancy, Honoraria, Research Funding; Teva: Consultancy; Rocket Medical: Consultancy, Research Funding; Seattle Genetics: Consultancy, Honoraria, Research Funding; GlaxoSmithKline: Honoraria, Research Funding; Janssen: Honoraria, Research Funding; Pharmacyclics: Honoraria, Research Funding; Juno Therapeutics: Consultancy; Takeda: Consultancy, Honoraria; Genentech, Inc.: Consultancy, Honoraria, Research Funding; Merck: Consultancy; Bayer: Consultancy, Honoraria, Research Funding. Diefenbach:Trillium: Research Funding; Millenium/Takeda: Research Funding; Merck: Consultancy, Research Funding; MEI: Research Funding; LAM Therapeutics: Research Funding; Incyte: Research Funding; Genentech, Inc.: Consultancy, Research Funding; Denovo: Research Funding; Bristol-Myers Squibb: Consultancy, Research Funding; Seattle Genetics: Consultancy, Research Funding. Gregory:Janssen: Consultancy; F. Hoffmann-La Roche, Genentech, Inc., MSD, AbbVie, BeiGene, AstraZeneca, Celgene, BMS: Research Funding; F. Hoffmann-La Roche, Novartis, AbbVie: Speakers Bureau; F. Hoffmann-La Roche, Novartis, Sandoz, Gilead, AbbVie, MSD: Honoraria; F. Hoffmann-La Roche, Novartis, Sandoz, Gilead: Membership on an entity's Board of Directors or advisory committees. Bartlett:BMS/Celgene: Research Funding; Merck: Research Funding; Kite, a Gilead Company: Research Funding; Immune Design: Research Funding; Janssen: Research Funding; Pfizer: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Millennium: Research Funding; Pharmacyclics: Research Funding; Seattle Genetics: Consultancy, Research Funding; Affimed Therapeutics: Research Funding; Autolus: Research Funding; Acerta: Consultancy; Roche/Genentech: Consultancy, Research Funding; Seattle Genetics: Membership on an entity's Board of Directors or advisory committees, Research Funding; BTG: Consultancy; ADC Therapeutics: Consultancy; Forty Seven: Research Funding. Wei:Genentech, Inc.: Current Employment; F. Hoffmann-La Roche: Current equity holder in publicly-traded company. Doral:Genentech, Inc.: Current Employment; F. Hoffmann-La Roche: Current equity holder in publicly-traded company. Yin:Genentech, Inc.: Current Employment, Current equity holder in publicly-traded company. Negricea:F. Hoffmann-La Roche: Current Employment. Li:F. Hoffmann-La Roche: Current Employment, Current equity holder in publicly-traded company; Genentech, Inc.: Current Employment. Penuel:Genentech, Inc./ F. Hoffmann-La Roche: Current Employment; F. Hoffmann-La Roche: Current equity holder in publicly-traded company. Huang:F. Hoffmann-La Roche: Current Employment. Budde:AstraZeneca: Speakers Bureau; Merck, Amgen, AstraZeneca, Mustang Therapeutics: Research Funding; F. Hoffmann-La Roche, Kite Pharma: Consultancy. OffLabel Disclosure: Mosunetuzumab (RG7828) is a full-length, fully humanized immunoglobulin G1 (IgG1) bispecific antibody targeting both CD3 (on the surface of T cells) and CD20 (on the surface of B cells). Mosunetuzumab redirects T cells to engage and eliminate malignant B cells. Mosunetuzumab is an investigational agent.

MCL-1 is one of the most frequently amplified genes in cancer, facilitating tumor initiation and maintenance and enabling resistance to anti-tumorigenic agents including the BCL-2 selective inhibitor venetoclax. The expression of MCL-1 is maintained via P-TEFb-mediated transcription, where the kinase CDK9 is a critical component. Consequently, we developed a series of potent small-molecule inhibitors of CDK9, exemplified by the orally active A-1592668, with CDK selectivity profiles that are distinct from related molecules that have been extensively studied clinically. Short-term treatment with A-1592668 rapidly downregulates RNA pol-II (Ser 2) phosphorylation resulting in the loss of MCL-1 protein and apoptosis in MCL-1-dependent hematologic tumor cell lines. This cell death could be attenuated by either inhibiting caspases or overexpressing BCL-2 protein. Synergistic cell killing was also observed between A-1592668 or the related analog A-1467729, and venetoclax in a number of hematologic cell lines and primary NHL patient samples. Importantly, the CDK9 inhibitor plus venetoclax combination was well tolerated in vivo and demonstrated efficacy superior to either agent alone in mouse models of lymphoma and AML. These data indicate that CDK9 inhibitors could be highly efficacious in tumors that depend on MCL-1 for survival or when used in combination with venetoclax in malignancies dependent on MCL-1 and BCL-2.

The BCL6 Corepressor (BCOR) is a component of a variant Polycomb repressive complex 1 (PRC1) that is essential for normal development. Recurrent mutations in the BCOR gene have been identified in acute myeloid leukaemia and myelodysplastic syndrome among other cancers; however, its function remains poorly understood. Here we examine the role of BCOR in haematopoiesis in vivo using a conditional mouse model that mimics the mutations observed in haematological malignancies. Inactivation of Bcor in haematopoietic stem cells (HSCs) results in expansion of myeloid progenitors and co-operates with oncogenic KrasG12D in the initiation of an aggressive and fully transplantable acute leukaemia. Gene expression analysis and chromatin immunoprecipitation sequencing reveals differential regulation of a subset of PRC1-target genes including HSC-associated transcription factors such as Hoxa7/9. This study provides mechanistic understanding of how BCOR regulates cell fate decisions and how loss of function contributes to the development of leukaemia., BCL6 corepressor (BCOR) is recurrently mutated in acute myeloid leukaemia and myelodysplastic syndrome. Here, the authors use mouse models to show the mechanism of how inactivation of BCOR in haematopoietic stem cells contributes to the development of leukaemia.

Acute promyelocytic leukemia (APL) is a hematological emergency requiring rapid initiation of therapy due to potentially fatal complications including disseminated intravascular coagulopathy. Clini...

Gene expression by RNA polymerase II (RNAPII) is tightly controlled by cyclin-dependent kinases (CDKs) at discrete checkpoints during the transcription cycle. The pausing checkpoint following transcription initiation is primarily controlled by CDK9. We discovered that CDK9-mediated, RNAPII-driven transcription is functionally opposed by a protein phosphatase 2A (PP2A) complex that is recruited to transcription sites by the Integrator complex subunit INTS6. PP2A dynamically antagonizes phosphorylation of key CDK9 substrates including DSIF and RNAPII-CTD. Loss of INTS6 results in resistance to tumor cell death mediated by CDK9 inhibition, decreased turnover of CDK9 phospho-substrates, and amplification of acute oncogenic transcriptional responses. Pharmacological PP2A activation synergizes with CDK9 inhibition to kill both leukemic and solid tumor cells, providing therapeutic benefit in vivo. These data demonstrate that fine control of gene expression relies on the balance between kinase and phosphatase activity throughout the transcription cycle, a process dysregulated in cancer that can be exploited therapeutically.

The treatment landscape of B-cell lymphomas is evolving with the advent of novel agents including immune and cellular therapies. Bispecific antibodies (bsAbs) are molecules that recognise two different antigens and are used to engage effector cells, such as T-cells, to kill malignant B-cells. Several bispecific antibodies have entered early phase clinical development since the approval of the CD19/CD3 bispecific antibody, blinatumomab, for relapsed/refractory acute lymphoblastic leukaemia. Novel bsAbs include CD20/CD3 antibodies that are being investigated in both aggressive and indolent non-Hodgkin lymphoma with encouraging overall response rates including complete remissions. These results are seen even in heavily pre-treated patient populations such as those who have relapsed after chimeric antigen receptor T-cell therapy. Potential toxicities include cytokine release syndrome, neurotoxicity and tumour flare, with a number of strategies existing to mitigate these risks. Here, we review the development of bsAbs, their mechanism of action and the different types of bsAbs and how they differ in structure. We will present the currently available data from clinical trials regarding response rates, progression free survival and outcomes across a range of non-Hodgkin lymphoma subtypes. Finally, we will discuss the key toxicities of bsAbs, their rates and management of these adverse events.

We present a case of late symptom onset of COVID-19 infection 72 days after initial diagnosis in an immunocompromised 53-year-old man. SARS-CoV-2 was cultured from his sputum sample at this time, and genomic sequencing suggested reinfection was unlikely. After receipt of convalescent plasma, SARS-CoV-2 became undetectable by PCR 111 days after diagnosis, although SARS-CoV-2 antibodies remained not detectable. This case posed difficult public health management issues in a low prevalence COVID-19 setting as the person required extended home isolation given his prolonged SARS-CoV-2 PCR detection.

Australia and New Zealand have achieved excellent community control of COVID-19 infection. In light of the imminent COVID-19 vaccination roll out in both countries, representatives from the Haematology Society of Australia and New Zealand and infectious diseases specialists have collaborated on this consensus position statement regarding COVID-19 vaccination in patients with haematological disorders. It is our recommendation that patients with haematological malignancies, and some benign haematological disorders, should have expedited access to high-efficacy COVID-19 vaccines, given that these patients are at high risk of morbidity and mortality from COVID-19 infection. Vaccination should not replace other public health measures in these patients, given that the effectiveness of COVID-19 vaccination, specifically in patients with haematological malignancies, is not known. Given the limited available data, prospective collection of safety and efficacy data of COVID-19 vaccination in this patient group is a priority. Refereed/Peer-reviewed

Context Follicular lymphoma (FL) often presents with recurrent relapses. Treatment options for patients (pts) with FL who have received ≥2 prior lines of therapy are limited, and prognosis is poor. The safety and efficacy of mosunetuzumab, a full-length, fully humanized IgG1 CD20/CD3 bispecific antibody is currently being investigated in an ongoing open-label, multicenter, Phase I/Ib, dose-escalation and expansion trial in relapsed/refractory (R/R) B-cell lymphoma (GO29781; NCT02500407). Objective To present updated data from the R/R FL cohort. Methods Pts received intravenous mosunetuzumab step-up doses in cycle (C) 1, days (D) 1 and 8, then the target dose on D15 and D1 of each subsequent 21-day cycle (Group B); treatment continued for ≤17 cycles. Results As of January 21, 2020, mosunetuzumab 0.4/1.0/2.8 mg to 1/2/13.5 mg (C1D1/8/15 dose levels) was given to 62 pts with FL who received ≥2 prior systemic therapies. Pts had a median age of 59 (27–85) years, median number of 3 (2–11) prior therapies; 33 pts (53%) were double refractory, 30 (48%) had progression of disease within 24 months of first-line treatment (POD24), and four (6%) received prior chimeric antigen receptor T-cell (CAR-T) therapy. Overall response rate (ORR) and CR rate were 68% and 50%, respectively. In high-risk pts, consistent CR rates were observed: 55% (18/33) in pts with double refractory disease, 53% (16/30) in pts who had POD24, 78% (7/9) in pts with PI3Ki refractory FL, and 50% (2/4) in those who received prior CAR-T therapy. Twenty-six pts with a CR (74%) remained in remission (median time on study: 14.4 months). In responders (n=42), median duration of response was 20.4 months (95% CI: 11.7–not reached), and median progression-free survival was 11.8 months (95% CI: 7.3–21.9). Adverse events (AEs) and serious AEs were reported in 60 (97%) and 22 pts (35%), respectively. The most common grade (Gr) ≥3 AEs included hypophosphatemia (23%) and neutropenia (21%). Fourteen pts (23%) experienced CRS1; events were mostly Gr 1 or 2, reversible, and occurred largely during C1. Conclusions A high CR rate, durable responses, and a manageable safety profile were observed with mosunetuzumab monotherapy in heavily pre-treated pts with FL, including high-risk pts.

SUMMARYGene expression is tightly controlled by Cyclin-dependent kinases (CDKs) which regulate the RNA Polymerase II (RNAPII) transcription cycle at discrete checkpoints. RNAPII pausing is a CDK9-controlled rate-limiting process that occurs shortly after initiation and is required for spatio-temporal control of transcription in multicellular organisms. We discovered that CDK9-mediated RNAPII pause-release is functionally opposed by a protein phosphatase 2A (PP2A) complex. PP2A dynamically competes for key CDK9 substrates, DSIF and RNAPII, and is recruited to transcription pausing sites by INTS6, a subunit of the Integrator complex. INTS6 depletion disrupts the Integrator-PP2A association and confers resistance to CDK9 inhibition. This results in unrestrained activity of CDK9 and dysregulation of acute transcriptional responses. Pharmacological PP2A activation amplifies RNAPII pausing mediated by CDK9 inhibitors and synergizes therapeutically in a model of MLL-rearranged leukemia. These data demonstrate that finely-tuned gene expression relies on the delicate balance of kinase and phosphatase activity throughout the transcription cycle.HIGHLIGHTSLoss of INTS6 confers resistance to CDK9 inhibitionINTS6 recruits PP2A to Integrator and chromatinPP2A/INTS6 complexes functionally oppose CDK9PP2A/INTS6 fine-tune acute transcriptional responsesSynergistic anti-cancer activity between PP2A activators and CDK9 inhibitors

Activating FMS-like tyrosine kinase 3 (FLT3) mutations occur in approximately 30% of all acute myeloid leukaemias (AMLs) and are associated with poor prognosis. The limited clinical efficacy of FLT3 inhibitor monotherapy has highlighted the need for alternative therapeutic targets and treatments for FLT3-mutant AML. Using human and murine models of MLL-rearranged AML harbouring FLT3 internal tandem duplication (FLT3-ITD) and primary patient samples, we have demonstrated that FLT3-ITD promotes serine uptake and serine synthesis via transcriptional regulation of neutral amino acid transporters (SLC1A4 and SLC1A5) and genes in the de novo serine synthesis pathway (PHGDH and PSAT1). Mechanistically, dysregulation of serine metabolism in FLT3-mutant AML is dependent on the mTORC1-ATF4 axis, that drives RNA-Pol II occupancy at PHGDH, PSAT1, SLC1A4 and SLC1A5. Genetic or pharmacological inhibition of the de novo serine synthesis pathway selectively inhibited the proliferation of FLT3-ITD AML cells, and this was potentiated by withdrawal of exogenous serine. Purine supplementation effectively rescued the antiproliferative effect of inhibiting de novo serine synthesis, consistent with the idea that serine fuels purine nucleotide synthesis in FLT3-mutant AML. Pharmacological inhibition of the de novo serine synthesis pathway, using the PHGDH inhibitor WQ-2101, sensitises FLT3-mutant AML cells to the standard of care chemotherapy agent cytarabine via exacerbation of DNA damage. Collectively, these data reveal new insights as to how FLT3 mutations reprogram metabolism in AML, and reveal a combination therapy strategy to improve the treatment of FLT3-mutant AML.Statement of SignificanceFLT3 mutations are common in AML and are associated with poor prognosis. We show that FLT3-ITD stimulates serine metabolism, thereby rendering FLT3-ITD leukemias dependent on serine for proliferation and survival. This metabolic dependency can be exploited pharmacologically to sensitize FLT3-mutant AML to chemotherapy.

Internal tandem duplication of the FMS-like tyrosine kinase 3 gene (FLT3-ITD) occurs in 30% of all acute myeloid leukemias (AML). Limited clinical efficacy of FLT3 inhibitors highlights the need for alternative therapeutic modalities in this subset of disease. Using human and murine models of FLT3-ITD–driven AML, we demonstrate that FLT3-ITD promotes serine synthesis and uptake via ATF4-dependent transcriptional regulation of genes in the de novo serine biosynthesis pathway and neutral amino acid transport. Genetic or pharmacologic inhibition of PHGDH, the rate-limiting enzyme of de novo serine biosynthesis, selectively inhibited proliferation of FLT3-ITD AMLs in vitro and in vivo. Moreover, pharmacologic inhibition of PHGDH sensitized FLT3-ITD AMLs to the standard-of-care chemotherapeutic cytarabine. Collectively, these data reveal novel insights into FLT3-ITD–induced metabolic reprogramming and reveal a targetable vulnerability in FLT3-ITD AML. Significance: FLT3-ITD mutations are common in AML and are associated with poor prognosis. We show that FLT3-ITD stimulates serine biosynthesis, thereby rendering FLT3-ITD–driven leukemias dependent upon serine for proliferation and survival. This metabolic dependency can be exploited pharmacologically to sensitize FLT3-ITD–driven AMLs to chemotherapy. This article is highlighted in the In This Issue feature, p. 1307

CDK12 and CDK13 regulate POLII elongation rate and processivity and influence the selection of transcription termination sites., The RNA polymerase II (POLII)–driven transcription cycle is tightly regulated at distinct checkpoints by cyclin-dependent kinases (CDKs) and their cognate cyclins. The molecular events underpinning transcriptional elongation, processivity, and the CDK-cyclin pair(s) involved remain poorly understood. Using CRISPR-Cas9 homology-directed repair, we generated analog-sensitive kinase variants of CDK12 and CDK13 to probe their individual and shared biological and molecular roles. Single inhibition of CDK12 or CDK13 induced transcriptional responses associated with cellular growth signaling pathways and/or DNA damage, with minimal effects on cell viability. In contrast, dual kinase inhibition potently induced cell death, which was associated with extensive genome-wide transcriptional changes including widespread use of alternative 3′ polyadenylation sites. At the molecular level, dual kinase inhibition resulted in the loss of POLII CTD phosphorylation and greatly reduced POLII elongation rates and processivity. These data define substantial redundancy between CDK12 and CDK13 and identify both as fundamental regulators of global POLII processivity and transcription elongation.

Targeting Bcl-2 family members upregulated in multiple cancers has emerged as an important area of cancer therapeutics. While venetoclax, a Bcl-2-selective inhibitor, has had success in the clinic, another family member, Bcl-xWe used structure-based chemistry to design a small-molecule inhibitor of Bcl-2 and Bcl-xWe discovered AZD4320, which has nanomolar affinity for Bcl-2 and Bcl-xAZD4320 is a potent molecule with manageable thrombocytopenia risk to explore the utility of a dual Bcl-2/Bcl-x

To separate causal effects of histone acetylation on chromatin accessibility and transcriptional output, we used integrated epigenomic and transcriptomic analyses following acute inhibition of major cellular lysine acetyltransferases P300 and CBP in hematological malignancies. We found that catalytic P300/CBP inhibition dynamically perturbs steady-state acetylation kinetics and suppresses oncogenic transcriptional networks in the absence of changes to chromatin accessibility. CRISPR-Cas9 screening identified NCOR1 and HDAC3 transcriptional co-repressors as the principal antagonists of P300/CBP by counteracting acetylation turnover kinetics. Finally, deacetylation of H3K27 provides nucleation sites for reciprocal methylation switching, a feature that can be exploited therapeutically by concomitant KDM6A and P300/CBP inhibition. Overall, this study indicates that the steady-state histone acetylation-methylation equilibrium functions as a molecular rheostat governing cellular transcription that is amenable to therapeutic exploitation as an anti-cancer regimen.

The COVID-19 pandemic poses a unique challenge to the care of patients with haematological malignancies. Viral pneumonia is known to cause disproportionately severe disease in patients with cancer, and patients with lymphoma, myeloma and chronic lymphocytic leukaemia are likely to be at particular risk of severe disease related to COVID-19. This statement has been developed by consensus among authors from Australia and New Zealand. We aim to provide supportive guidance to clinicians making individual patient decisions during the COVID-19 pandemic, in particular during periods that access to healthcare resources may be limited. General recommendations include those to minimise patient exposure to COVID-19, including the use of telehealth, avoidance of non-essential visits and minimisation of time spent by patients in infusion suites and other clinical areas. This statement also provides recommendations where appropriate in assessing indications for therapy, reducing therapy-associated immunosuppression and reducing healthcare utilisation in patients with specific haematological malignancies during the COVID-19 pandemic. Specific decisions regarding therapy of haematological malignancies will need to be individualised, based on disease risk, risks of immunosuppression, rates of community transmission of COVID-19 and available local healthcare resources.

Mcl-1 is a member of the Bcl-2 family of proteins that promotes cell survival by preventing induction of apoptosis in many cancers. High expression of Mcl-1 causes tumorigenesis and resistance to anticancer therapies highlighting the potential of Mcl-1 inhibitors as anticancer drugs. Here, we describe AZD5991, a rationally designed macrocyclic molecule with high selectivity and affinity for Mcl-1 currently in clinical development. Our studies demonstrate that AZD5991 binds directly to Mcl-1 and induces rapid apoptosis in cancer cells, most notably myeloma and acute myeloid leukemia, by activating the Bak-dependent mitochondrial apoptotic pathway. AZD5991 shows potent antitumor activity in vivo with complete tumor regression in several models of multiple myeloma and acute myeloid leukemia after a single tolerated dose as monotherapy or in combination with bortezomib or venetoclax. Based on these promising data, a Phase I clinical trial has been launched for evaluation of AZD5991 in patients with hematological malignancies (NCT03218683)., High expression of Mcl-1 promotes tumorigenesis and resistance to anticancer therapies. Here they report a macrocyclic molecule with high selectivity and affinity for Mcl-1 that exhibits potent anti-tumor effects as single agent and in combination with bortezomib or venetoclax in preclinical models of multiple myeloma and acute myeloid leukemia.

Aim: Primary Central Nervous System Lymphoma (PCNSL) [i.e. diffuse large B-cell lymphoma of the CNS] is a rare and poor-prognosis disease occurring predominantly in older patients (median age >60 years old). Prospective studies of two commonly used chemoimmunotherapy (CIT) protocols, MATRix and MPV/Ara-C (± rituximab), have reported 2-year PFS and OS of 57-61% and 69-81% respectively. Our aim was to evaluate registry-reported outcomes of frontline CIT strategies employed at Australasian sites. Method: A retrospective study of consecutive, immunocompetent, adult PCNSL patients (WHO criteria: 2017) treated with curative-intent CIT, from 10 sites (9 Australian, 1 Singaporean) between 1 st January 2009 and 31 st December 2018 (i.e. ten-year period). Overall survival (OS) and progression-free survival (PFS) were calculated using the Kaplan-Meier (log-rank) method. Univariate associations were derived using a Cox model with variables p Results: Data was collected on 207 patients, 189 of whom met WHO diagnostic criteria for PCNSL (i.e. diffuse large B-cell lymphoma of the CNS). We excluded patients with insufficient data (6), non-DLBCL histology (6), secondary PCNSL (3) and post-transplant lymphoproliferative disorder (3). Of these, 176 (93%) received curative-intent CIT. The majority (66%) were over 65 years of age (median: 65, range: 25-87); ECOG performance status was ≥ 2 in 31% (data not available for 14% of patients). The majority were male (55%) and had deep structure involvement (64%). International Extranodal Lymphoma Study Group (IELSG) risk criteria could not be calculated in many patients due to missing data (predominantly LDH and CSF protein). CSF involvement was rare (n=23, 13%) but data was only available for 60% of patients. Of the 159 with documented renal function, 26% had renal impairment (defined as Cockroft-Gault creatinine clearance Five CIT regimens were used: MATRix (n=16), MPV/Ara-C + rituximab (Rtx) (n=94), MBVP+- Rtx (n=11), MTX +-Rtx (n=31) and MTX/Ara-C +- Rtx (n=24). Intrathecal chemotherapy was used in only 29 patients (16%), and almost exclusively in combination with R-MPV. Median cumulative MTX dose was 17,500mg/m 2 (range: 1,000-64,000mg/m 2) and 69% received Ara-C (median dose: 12,000mg/m 2 [range: 1,000-44,000mg/m 2]). Eighty percent of patients achieved an overall response at the end of MTX therapy, with 52% achieving a complete response [data unavailable in n=29, 16%]. Estimated 2-year PFS and OS for the entire cohort were 54% (95%CI: 0.46-0.62) and 77% (95%CI: 0.70-0.83) respectively at a median follow-up of 2 years. Older patients (>60yo) had shorter PFS but similar OS compared to their younger counterparts (2-year PFS: 47% vs 68%, p: 0.015, HR: 1.73, 95%CI: 1.11-2.70; 2-year OS: 74% vs 80%, p: 0.145, HR: 1.38, 95%CI: 0.81-2.33). R-MPV achieved superior PFS compared to MATRix although comparison was limited by low numbers in the MATRix cohort (n=16 vs n=94), likely reflective of the census period [2-year PFS: 74% vs 44% p: 0.025, HR 0.41, 95%CI 0.13-1.28]. Neither WBRT (n=57, 32%) nor ASCT (n=13, 7%) conferred a survival advantage but addition of rituximab (n=153, 87%) was associated with improved PFS (p: 0.007, HR: 0.47, 95%CI: 0.19-0.75). On multivariate analysis, type of induction CIT (p: 0.004, HR: 1.42, 95%CI: 1.23-1.42), cumulative MTX dose (p: 0.022, HR: 0.88, 95%CI: 0.83-0.94) and cumulative Ara-C dose (p: 0.016, HR: 0.76, 95%CI: 0.64-0.87) were associated with improved PFS. Cumulative MTX dose (p: 0.02, HR: 0.85, 95%CI: 0.78-0.92) and cumulative Ara-C dose (p: 0.007, HR: 0.67, 95%CI: 0.51-082) were also associated with improved OS. Conclusion: Registry-reported outcomes of contemporary CIT induction for PCNSL are favourable when compared to published trials and historical regimens. PCNSL with contemporary treatment should no longer be considered an invariably poor-prognostic disease. Data supports recent literature highlighting prognostic significance associated with maintenance of chemotherapy dose intensity (Martinez-Calle et al., Br J Haematol. 2020 Aug; 190(3):394-404. doi. 10.1111/bjh.16592). Figure 1 Figure 1. Disclosures Lewis: AstraZeneca: Consultancy, Honoraria; Janssen: Honoraria, Patents & Royalties: Conference attendance; Novartis: Patents & Royalties: Conference attendance; Roche: Consultancy, Honoraria. Gunjur: Myers Squibb: Honoraria. Ku: Roche: Consultancy; Antegene: Consultancy; Genor Biopharma: Consultancy. Wight: Jannsen: Honoraria, Other: Travel subsidies; Abbvie: Honoraria, Other: Travel subsidies. Shortt: Amgen: Research Funding; Astex: Research Funding; BMS: Research Funding; Novartis: Membership on an entity's Board of Directors or advisory committees; Astellas: Membership on an entity's Board of Directors or advisory committees. Talaulikar: Roche: Honoraria, Research Funding; Jansenn: Honoraria, Research Funding; Amgen: Honoraria, Research Funding; Takeda: Honoraria, Research Funding; EUSA Pharma: Honoraria, Research Funding. Hawkes: Gilead: Membership on an entity's Board of Directors or advisory committees; Roche: Membership on an entity's Board of Directors or advisory committees, Other: Travel and accommodation expenses, Research Funding, Speakers Bureau; Regeneron: Speakers Bureau; Novartis: Membership on an entity's Board of Directors or advisory committees; Merck Sharpe Dohme: Membership on an entity's Board of Directors or advisory committees; Janssen: Speakers Bureau; Astra Zeneca: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Merck KgA: Research Funding; Bristol Myers Squib/Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding; Specialised Therapeutics: Consultancy; Antigene: Membership on an entity's Board of Directors or advisory committees. Cheah: MSD: Consultancy, Honoraria, Other: advisory, Research Funding; Janssen: Consultancy, Honoraria, Other: advisory; TG Therapeutics: Consultancy, Honoraria, Other: advisory; Roche: Consultancy, Honoraria, Other: advisory and travel expenses, Research Funding; Loxo/Lilly: Consultancy, Honoraria, Other: advisory; AstraZeneca: Consultancy, Honoraria, Other: advisory; Celgene: Research Funding; AbbVie: Research Funding; Beigene: Consultancy, Honoraria, Other: advisory; Ascentage pharma: Consultancy, Honoraria, Other: advisory; Gilead: Consultancy, Honoraria, Other: advisory. Opat: Merck: 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, Research Funding; Astra Zeneca: Consultancy, 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, Research Funding; Roche: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; BeiGene: 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, Research Funding; Pharmacyclics: Research Funding; Sandoz: Research Funding; Takeda: 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; CSL Behring: Honoraria, Membership on an entity's Board of Directors or advisory committees; Monash Health: Current Employment. Gregory: Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel fees, Speakers Bureau; Janssen: Consultancy; Novartis: Consultancy.

Introduction : IGM-2323 is the first engineered high-affinity, high-avidity bispecific IgM monoclonal antibody TCE to be tested in the clinic. It has 10 binding domains for CD20 and a single binding domain for CD3 and is designed to bind irreversibly to CD20-high and low-expressing cells with more physiologic stimulation to T cells, which may mitigate cytokine release syndrome (CRS)-related toxicity and broaden the therapeutic window. IGM-2323 may act by multiple mechanisms: T-cell dependent cytotoxicity, complement dependent cytotoxicity, and enhanced immune modulation via IFNγ-dominant cytokine stimulation. This phase 1 study is exploring the safety and activity of IGM-2323 using a dose titration schedule intended to optimize repeatable immune stimulation while minimizing toxicity. Methods : This first-in-human Phase 1 study is a global, multicenter, open-label, dose escalation evaluating safety, tolerability, PK, and preliminary efficacy (NCT04082936). Adults with relapsed or refractory CD20 + B-cell NHL with ≥ 2 prior systemic therapies, adequate organ function, and ECOG 0-1 are eligible. IGM-2323 is given IV on Days 1, 8, and 15 of 21-day cycles until disease progression or unacceptable toxicity. Treatment can continue beyond progression if the patient (pt) has benefitted from treatment and intra-patient dose escalation is allowed. This study also utilizes a dose titration scheme where a starting dose is given on Day 1, then higher subsequent doses are given up to a plateau dose. If a pt has symptoms of CRS, the same dose may be repeated, and a higher dose is not given until the dose is well tolerated. Results : As of April 30, 2021, 29 pts have been enrolled: 12 at 5 fixed dose levels (0.5, 2.5, 10, 30, 100 mg) and 17 at 5 dose titration levels (50/100, 50/200, 50/300, 50/600, 50/1000 mg)*. NHL subtypes include: 13 follicular (FL), 11 diffuse large B-cell (DLBCL), 3 mantle cell (MCL), and 2 marginal zone (MZL). Median age is 66 (range, 36-84) and median prior therapies is 3 (range, 2-7). 2 pts had prior autologous transplant and 7 had prior CAR-T. All 29 pts received at least one dose and are safety evaluable. There were no DLTs and no neurotoxicity AEs. No pts discontinued due to AE. There were 3 drug-related SAEs (1 each Gr1/2/3 CRS by ASTCT). 16 pts discontinued treatment: 2 pt/investigator decision and 14 PD. The 13 pts still on treatment have received a median of 9 doses (range, 1-42). At fixed dose levels, 5 of 12 pts had a CRS event, primarily grade 1 (fever). Only 1 of 17 titration pts had CRS (Gr3 in a pt with prior experimental CAR-T and baseline circulating B-cells). The most common drug-related AEs in titration pts were hypophosphatemia (29%), IRR (29%; the distinction between IRR and CRS was determined by the investigator), and nausea (24%). 23 pts were evaluable for efficacy; there were 8 responses (5 CR, 3 PR). 5 responses were in FL/MZL and 3 in DLBCL/MCL. Response kinetics varied, with some CRs at the first scan (Week 6) and others after biopsy-confirmed pseudo-progression or prolonged SD (up to 69 weeks). 7 of 8 responses were ongoing as of the data cut. 5 of 11 evaluable patients in dose titration cohorts responded (3 CR, 2 PR), with a median time to response of 6 weeks. In the titration cohort with the longest follow-up (50/100), there were 2 CR and 1 PR in 4 evaluable pts. Repeatable IFNγ stimulation is detectable in nearly all pts with measurable cytokine elevations, while polycytokine response was observed in CRS cases (Table). Preliminary IHC data in matched baseline and on-treatment biopsies (n=3) shows decrease of CD20 + tumor cells and increase of CD3 + T cells in tumor tissue upon treatment, regardless of clinical response. Conclusions : Preliminary results from this first-in-human study of IGM-2323 show an excellent safety and tolerability profile at up to 1000 mg, with reduced CRS when IGM-2323 was given using a dose titration scheme. Response patterns included rapid responses, deepening responses and pseudo-progression. IGM-2323 also has evidence of an IFNγ-dominant repeatable T-cell activation and preservation of T cell function over time. The MTD of IGM-2323 has not been reached. Clinical activity was observed across multiple histologies. Updated safety, PK, biomarker, and efficacy data, including complete dose escalation data, will be presented at the meeting. * starting and plateau dose referenced Figure 1 Figure 1. Disclosures Budde: Mustang Bio, Inc: Research Funding; Roche: Consultancy; BeiGene: Consultancy; Novartis: Consultancy; AstraZeneca: Research Funding; IGM Biosciences: Research Funding; Merck, Inc: Research Funding; Amgen: Research Funding; Gilead: Consultancy. Gopal: Agios: Research Funding; MorphoSys: Honoraria; Bristol Meyers Squibb: Research Funding; Incyte: Honoraria; Acrotech: Consultancy, Honoraria; Servier: Consultancy, Honoraria; IGM Biosciences: Research Funding; Nurix Inc: Consultancy, Honoraria; Beigene: Consultancy, Honoraria; Astra-Zeneca: Research Funding; Takeda: Research Funding; Teva: Research Funding; ADC Therapeutics: Consultancy, Honoraria; Kite: Consultancy, Honoraria; Cellectar: Consultancy, Honoraria; Genetech: Consultancy, Honoraria, Research Funding; Gilead: Consultancy, Honoraria, Research Funding; I-Mab bio: Consultancy, Honoraria, Research Funding; Epizyme: Consultancy, Honoraria; SeaGen: Consultancy, Honoraria, Research Funding; Janssen: Consultancy, Honoraria, Research Funding; Karyopharm: Consultancy, Honoraria; Merck: Consultancy, Honoraria, Research Funding. Kim: Dong-A Pharmaceutical: Research Funding; Eisai: Research Funding; Celltrion: Research Funding; Johnson & Johnson: Research Funding; Kyowa Kirin: Research Funding; Roche: Research Funding; Sanofi: Research Funding; IGM Biosciences: Research Funding. Flinn: Novartis: 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; Incyte: Other: All 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; 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; Forty Seven: 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; MorphoSys: Consultancy, Other: All consultancy and 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; 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; Calithera Biosciences: Other: All 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; Celgene: Other: All 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; Juno Therapeutics: 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; IGM Biosciences: Other: All 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; Roche: 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; Gilead Sciences: Consultancy, Other: All consultancy and 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; Acerta Pharma: 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; Loxo: Other: All 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; Rhizen Pharmaceuticals: 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; Agios: Other: All 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; Nurix Therapeutics: Consultancy, Other: All consultancy payments made to Sarah Cannon Research Institute; Pfizer: Other: All research funding payments made to Sarah Cannon Research Institute, Research Funding; Great Point Partners: Consultancy, Other: All consultancy payments made to Sarah Cannon Research Institute; Portola Pharmaceuticals: 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; Iksuda Therapeutics: Consultancy, Other: All consultancy payments made to Sarah Cannon Research Institute; 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; Triphase Research & Development Corp.: Other: All research funding payments made to Sarah Cannon Research Institute, Research Funding; Century Therapeutics: Consultancy, Other: All consultancy payments made to Sarah Cannon Research Institute; Hutchison MediPharma: Consultancy, Other: All consultancy payments made to Sarah Cannon Research Institute; Vincerx Pharma: Consultancy, Other: All consultancy payments made to Sarah Cannon Research Institute; Sarah Cannon Research Institute: Current Employment; 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 holder of individual stocks in a privately-held company; Seattle Genetics: Research Funding. Cheah: Ascentage Pharma: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; AstraZeneca: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; BMS: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Roche: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Accommodations, Expenses, Research Funding; Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Gilead: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Lilly: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; TG therapeutics: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; MSD: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Beigene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Abbvie: Research Funding. Nastoupil: Bayer: Honoraria; Denovo Pharma: Other: DSMC; Novartis: Honoraria, Research Funding; Genentech: Honoraria, Research Funding; Pfizer: Honoraria, Research Funding; TG Therapeutics: Honoraria, Research Funding; Takeda: Honoraria, Other: DSMC, Research Funding; IGM Biosciences: Research Funding; Caribou Biosciences: Research Funding; Gilead/Kite: Honoraria, Research Funding; Bristol Myers Squibb/Celgene: Honoraria, Research Funding; Epizyme: Honoraria, Research Funding; ADC Therapeutics: Honoraria; Janssen: Honoraria, Research Funding; MorphoSys: Honoraria. Matasar: Daiichi Sankyo: Consultancy; TG Therapeutics: Consultancy, Honoraria; Merck Sharp & Dohme: Current holder of individual stocks in a privately-held company; Juno Therapeutics: Consultancy; Rocket Medical: Consultancy, Research Funding; Genentech, Inc.: Consultancy, Honoraria, Research Funding; Teva: Consultancy; F. Hoffmann-La Roche Ltd: Consultancy, Honoraria, Research Funding; Memorial Sloan Kettering Cancer Center: Current Employment; Bayer: Consultancy, Honoraria, Research Funding; GlaxoSmithKline: Honoraria, Research Funding; Merck: Consultancy; IGM Biosciences: Research Funding; Pharmacyclics: Honoraria, Research Funding; ImmunoVaccine Technologies: Consultancy, Honoraria, Research Funding; Janssen: Honoraria, Research Funding; Seattle Genetics: Consultancy, Honoraria, Research Funding; Takeda: Consultancy, Honoraria. Diefenbach: Janssen: Consultancy, Honoraria, Research Funding; Morphosys: Consultancy, Honoraria, Research Funding; Merck Sharp & Dohme: Consultancy, Honoraria, Research Funding; Gilead: Current equity holder in publicly-traded company; Trillium: Research Funding; IGM Biosciences: Research Funding; Celgene: Research Funding; AbbVie: Research Funding; Perlmutter Cancer Center at NYU Langone Health: Current Employment; Incyte: Research Funding; MEI: Consultancy, Research Funding; Genentech, Inc./ F. Hoffmann-La Roche Ltd: Consultancy, Honoraria, Research Funding; Seattle Genetics: Consultancy, Honoraria, Research Funding; Bristol-Myers Squibb: Consultancy, Honoraria, Research Funding; IMab: Research Funding. Gregory: Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel fees, Speakers Bureau; Janssen: Consultancy; Novartis: Consultancy. Qazi: IGM Biosciences: Current Employment. Pang: IGM Biosciences: Consultancy. Leabman: IGM Biosciences: Current Employment. Hernandez: IGM Biosciences: Current Employment. Sison: IGM Biosciences: Current Employment. Keyt: IGM Biosciences: Current Employment. Chen: IGM Biosciences: Ended employment in the past 24 months. Armand: Enterome: Consultancy; C4: Consultancy; GenMab: Consultancy; Infinity: Consultancy; Otsuka: Research Funding; Regeneron: Consultancy; Pfizer: Consultancy; Morphosys: Consultancy; Daiichi Sankyo: Consultancy; Epizyme: Consultancy; Affimed: Consultancy, Research Funding; Adaptive: Consultancy, Research Funding; AstraZeneca: Consultancy; Genentech: Consultancy, Research Funding; Roche: Research Funding; Tensha: Research Funding; IGM: Research Funding; Kite: Research Funding; ADC Therapeutics: Consultancy; BMS: Consultancy, Honoraria, Research Funding; Sigma Tau: Research Funding; Merck: Consultancy, Honoraria, Research Funding; Celgene: Consultancy; Miltenyi: Consultancy; Tessa Therapeutics: Consultancy.

Introduction Lymphoma complicates approximately 1/6000 pregnancies (Pereg, Haematologica 2007), and presents challenges for the patient, her family, and medical professionals. This rare event raises unique therapeutic, social and ethical issues, with the welfare of both mother and unborn child to consider. There are challenges regarding symptom obfuscation, diagnosis delays and treatment delivery. In this retrospective study, we aimed to describe the experience, treatment patterns and outcomes of lymphoma in pregnancy in Australia and New Zealand. Methods We identified patients aged ≥18 diagnosed with lymphoma in pregnancy between 1 January 2009 and 31 December 2020 , across 11 institutions in Australia and New Zealand. We defined "lymphoma in pregnancy" as diagnoses occurring during pregnancy (antenatal cases) or the first 12 months after delivery (postpartum cases). Postpartum cases were included to account for the phenomenon of diagnostic delay during gestation due to deferral of diagnostic investigations and symptom obfuscation (de Haan, Lancet Oncol 2018). Overall survival was calculated by Kaplan-Meier methods from the date of diagnosis to death, with patients alive and lost to follow-up censored on the last day of follow-up. Results We identified 63 patients, 34 diagnosed antepartum and 29 diagnosed postpartum (Table 1). The most common diagnoses were classical Hodgkin lymphoma (HL) (35), followed by diffuse large B cell lymphoma (11) and primary mediastinal B cell lymphoma (6). The median age was 32 (range 23-42) years. Women diagnosed antepartum were more likely to be nulliparous (p=0.004). Of the postpartum cases, symptoms of malignancy first appeared during pregnancy in 24%. At diagnosis, 44% had advanced stage disease. 60% of women had PET as part of baseline staging, however only 8% underwent PET whilst pregnant, all during the second or third trimester. 83% of HL patients had adverse risk factors (mediastinal bulk >1/3 diameter, ESR>50mm/hr, >2 sites). ESR alone, which may be elevated physiologically in pregnancy, was the sole adverse risk factor for 9% of HL patients. Median days between diagnosis and treatment initiation were 14 (IQR 8-30) for antenatal patients and 21 (IQR 7-40) for postnatal. 19% of the antenatal cohort with aggressive lymphoma had treatment deferred/delayed explicitly due to pregnancy. The majority (89%) of antenatal patients were treated with ABVD (HL) or (R)CHOP/(R)EPOCH (NHL) whilst pregnant. 3 patients received first-line treatment divergent from standard (vinblastine for HL, interferon for indolent B-NHL and surgery for primary cutaneous ALCL). 37% received radiotherapy, although only 1 patient received it antenatally. Median follow up was 34 months. 5 year OS for HL was 83% (95%CI 54%-95%) and for DLBCL 74% (95%CI 30%-93%)(Figure 1). Seven patients died (4 from lymphoma, 2 treatment-related infection, 1 unknown). Discussion of elective termination of pregnancy was documented in 24 of 34 antenatal diagnoses, advised in 3 and performed in 2, both in the first trimester. Only 31 (49%) of 63 women had documented evidence of counselling regarding future fertility strategies. Of the 48 patients with available data, there were 45 live births, 2 elective terminations and 1 spontaneous abortion in the first trimester. The mean gestation at birth was significantly earlier and marginally preterm for antenatal diagnoses (mean 35.6wk v 38.2wk, p=0.002). 6 neonates (11%) were small for gestational age, 5 of whom were born to mothers diagnosed antenatally. 29% of neonates were admitted to neonatal intensive care or special care units. There were no cases of neonatal neutropenia, one case of sepsis of prematurity and one case of PJP infection in a term baby. Conclusion Lymphoma in pregnancy is rare and lacks a harmonised approach. We present a large multicentre cohort reflecting contemporary practice. Although standard therapy could be provided to most patients, delays in treatment and diagnosis were common, and most antenatally-diagnosed women did not receive optimal staging. Neonates in the antenatally-diagnosed group were more likely to be premature, however there are likely a number of confounders and causality cannot be presumed. There were no neonatal deaths. It is imperative to continue to report on data regarding lymphoma in pregnancy to inform optimal care in this setting. Figure 1 Figure 1. Disclosures Greenwood: Amgen: Membership on an entity's Board of Directors or advisory committees, Research Funding; Pfizer: Membership on an entity's Board of Directors or advisory committees; Servier: Membership on an entity's Board of Directors or advisory committees, Research Funding; Jazz Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees. Gregory: Janssen: Consultancy; Novartis: Consultancy; Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel fees, Speakers Bureau. Hamad: Novartis: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau.