Abstract: Purpose: Colony-stimulating factor 3 receptor (CSF3R) mutations have been identified in the majority of chronic neutrophilic leukemia (CNL) and a smaller percentage of atypical chronic myeloid leukemia (aCML) cases. Although CSF3R point mutations (e.g., T618I) are emerging as key players in CNL/aCML, the significance of rarer CSF3R mutations is unknown. In this study, we assess the importance of the CSF3R T640N mutation as a marker of CNL/aCML and potential therapeutic target. Experimental Design: Sanger sequencing of leukemia samples was performed to identify CSF3R mutations in CNL and aCML. The oncogenicity of the CSF3R T640N mutation relative to the T618I mutation was assessed by cytokine independent growth assays and by mouse bone marrow transplant. Receptor dimerization and O-glycosylation of the mutants was assessed by Western blot, and JAK inhibitor sensitivity was assessed by colony assay. Results: Here, we identify a CSF3R T640N mutation in two patients with CNL/aCML, one of whom was originally diagnosed with MDS and acquired the T640N mutation upon evolution of disease to aCML. The T640N mutation is oncogenic in cellular transformation assays and an in vivo mouse bone marrow transplantation model. It exhibits many similar phenotypic features to T618I, including ligand independence and altered patterns of O-glycosylation—despite the transmembrane location of T640 preventing access by GalNAc transferase enzymes. Cells transformed by the T640N mutation are sensitive to JAK kinase inhibition to a similar degree as cells transformed by CSF3R T618I. Conclusions: Because of its similarities to CSF3R T618I, the T640N mutation likely has diagnostic and therapeutic relevance in CNL/aCML. Clin Cancer Res; 22(3); 757–64. ©2015 AACR.

Abstract: Deficient anti-tumor immunity often results from an immunosuppressive tumor microenvironment (TME) that renders antigen presenting cells (APCs) unable to effectively stimulate T cells. Recent studies indicate that local delivery of immunostimulatory adjuvants can activate tumor resident APCs, driving uptake, processing and presentation of tumor neoantigens to T cells that mediate anti-tumor immunity. To overcome challenges associated with intratumoral delivery of such adjuvants, we developed a novel class of TLR immune-stimulating antibody conjugates (TAC) that comprise a TLR7/8 agonist conjugated to tumor-targeting monoclonal antibodies. In vitro co-cultures with human cancer cell lines and leukocytes revealed that TACs potently activate primary APCs, leading to increased co-stimulatory molecule expression (e.g. CD40, CD86) and secretion of pro-inflammatory cytokines (e.g. TNFα). The TACs also enhanced antibody-mediated effector functions such as ADCC and ADCP. Surprisingly, these constructs also induced dendritic cell (DC) differentiation from monocytes, as measured by changes in cellular morphology and DC surface markers (e.g. CD14 downregulation). CyTOF-based analysis of intracellular signaling in human leukocytes revealed a unique signaling signature of the conjugate compared to a mixture of its components, suggesting a novel biological mechanism by which the conjugate stimulates APCs. Finally, we demonstrated in vivo efficacy in syngeneic tumor models in which TAC treatment led to tumor clearance and development of immunologic memory. These results provide a strong rationale for this technology as a platform for cancer immunotherapy. Citation Format: Shelley E. Ackerman, Joseph C. Gonzalez, Josh D. Gregorio, Jason C. Paik, Felix J. Hartmann, Justin A. Kenkel, Arthur Lee, Angela Luo, Cecelia I. Pearson, Murray L. Nguyen, Benjamin Ackerman, Lauren Y. Sheu, Richard P. Laura, Steven J. Chapin, Brian S. Safina, Sean C. Bendall, David Dornan, Edgar G. Engleman, Michael N. Alonso. TLR7/8 immune-stimulating antibody conjugates elicit robust myeloid activation leading to enhanced effector function and anti-tumor immunity in pre-clinical models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1559.

Abstract: TPS7572 Background: Inhibition of Bruton tyrosine kinase (BTK) has emerged as a strategy for targeting B-cell malignancies including CLL/SLL. Zanubrutinib, an investigational inhibitor of BTK, was specifically engineered to optimize selectivity, half-life and solubility in an effort to decrease toxicities and better penetrate tumor tissue. Early clinical data suggested that zanubrutinib treatment in patients with treatment-naïve (TN; n = 16) or R/R (n = 50) CLL/SLL induced deep responses: 94% overall response rate (ORR), including 6% and 2% complete response rates in TN and R/R CLL/SLL, respectively (ICML 2017). This study is designed to evaluate whether zanubrutinib monotherapy exhibits non-inferior and potentially superior efficacy based on the ORR vs ibrutinib monotherapy in patients with R/R CLL/SLL. Methods: This ongoing phase 3, randomized, open-label, global study (NCT03734016, BGB-3111-305) is comparing the efficacy and safety of zanubrutinib vs ibrutinib in adult patients with R/R CLL/SLL. Approximately 400 patients will be randomized, 1:1 to each arm and stratified by age ( 〈 65 vs ≥ 65 years), refractory status (yes vs no), geographic region, and del(17p)/ TP53 mutation status (present vs absent). Key inclusion criteria include R/R CLL/SLL requiring treatment per iwCLL criteria, ECOG PS 0-2, and adequate hematologic function. The primary endpoint is ORR as determined by an independent review committee according to iwCLL guidelines, with modification for treatment-related lymphocytosis for patients with CLL and per 2014 Lugano Classification for patients with SLL. The study is powered to test the non-inferiority and superiority of the ORR for zanubrutinib vs ibrutinib. Secondary endpoints include progression-free survival, safety, duration of response, and overall survival. Recruitment is ongoing. Clinical trial information: NCT03734016.

Abstract: Somatic mutations in UBA1 cause vacuoles, E1 ubiquitin-activating enzyme, X-linked, autoinflammatory somatic (VEXAS) syndrome, an adult-onset inflammatory disease with an overlap of hematologic manifestations. VEXAS syndrome is characterized by a high mortality rate and significant clinical heterogeneity. We sought to determine independent predictors of survival in VEXAS and to understand the mechanistic basis for these factors. We analyzed 83 patients with somatic pathogenic variants in UBA1 at p.Met41 (p.Met41Leu/Thr/Val), the start codon for translation of the cytoplasmic isoform of UBA1 (UBA1b). Patients with the p.Met41Val genotype were most likely to have an undifferentiated inflammatory syndrome. Multivariate analysis showed ear chondritis was associated with increased survival, whereas transfusion dependence and the p.Met41Val variant were independently associated with decreased survival. Using in vitro models and patient-derived cells, we demonstrate that p.Met41Val variant supports less UBA1b translation than either p.Met41Leu or p.Met41Thr, providing a molecular rationale for decreased survival. In addition, we show that these 3 canonical VEXAS variants produce more UBA1b than any of the 6 other possible single-nucleotide variants within this codon. Finally, we report a patient, clinically diagnosed with VEXAS syndrome, with 2 novel mutations in UBA1 occurring in cis on the same allele. One mutation (c.121 A & gt;T; p.Met41Leu) caused severely reduced translation of UBA1b in a reporter assay, but coexpression with the second mutation (c.119 G & gt;C; p.Gly40Ala) rescued UBA1b levels to those of canonical mutations. We conclude that regulation of residual UBA1b translation is fundamental to the pathogenesis of VEXAS syndrome and contributes to disease prognosis.

Abstract: Background: Zanubrutinib is a highly selective, next-generation Bruton tyrosine kinase (BTK) inhibitor designed to maximize BTK occupancy and minimize off-target effects. Zanubrutinib has been associated with improved specificity and durable clinical responses in patients with chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL; Tam, Blood 2019;134:851-9). Early clinical data from Arm C of the SEQUOIA trial suggested that zanubrutinib was active and well-tolerated in treatment-naïve (TN) CLL/SLL patients with the high-risk characteristic deletion of chromosome 17p13.1 [del(17p)] (Tam ASH 2019 #499). In that cohort, an overall response rate (ORR) of 92.7% was reported, and the most common adverse events (AEs; 20.1% contusion, 15.6% upper respiratory tract infection, 13.8% rash) and most common grade ≥3 AEs (10.1% neutropenia, 3.7% pneumonia, 2.8% hypertension) were consistent with those in previous reports of zanubrutinib treatment in patients with various B-cell malignancies. Venetoclax is a B-cell lymphoma 2 protein (BCL-2) inhibitor approved for the treatment of adult patients with CLL or SLL. Results of several phase 2 CLL trials of BCL-2 inhibitor and BTK inhibitor combinations have suggested that combination treatment is tolerable and may have synergistic activity (Hillmen JCO 2019;37:2722-9. Jain, NEJM 2019;380:2095-103. Siddiqi, EHA 2020 #S158.). Combination treatment given for a finite duration as determined by undetectable minimal residual disease (uMRD) is of significant interest and has the potential to alter the CLL/SLL treatment landscape if shown to induce deeper responses with a fixed duration of therapy. In the BOVen study, zanubrutinib was given in combination with venetoclax and obinutuzumab to TN CLL patients, and uMRD in the peripheral blood and bone marrow was used to determine treatment discontinuation (Soumerai, ASCO 2020 #8006.) Preliminary data showed that 62% of patients met the uMRD endpoint and successfully discontinued treatment after a median of 8 months (6 months of triplet therapy), and 100% of patients had a best response of partial response or higher (43% complete response/complete response with incomplete marrow recovery). The most common grade ≥3 AEs (15.4% neutropenia, 5.1% thrombocytopenia, 5.1% lung infection, 2.6% infusion-related reaction, 2.6% rash, 2.6% bleeding) were consistent with those previously reported in combination treatment studies, and no events of tumor lysis syndrome (TLS) were reported. Study Design and Methods : The SEQUOIA trial (NCT03336333) is an open-label, global, multicenter, phase 3 study that includes a nonrandomized cohort (Arm D) of up to 50 TN patients with del(17p) CLL/SLL. Arm D is designed to provide combination treatment of zanubrutinib and venetoclax and use serial monitoring of uMRD to determine treatment discontinuation. Patients are treated with zanubrutinib (160 mg twice daily) for 3 months followed by the combination of zanubrutinib (same dosing) and venetoclax (ramp-up cycle followed by 400 mg once daily). Combination treatment is given for 12-24 cycles until disease progression, unacceptable toxicity, or requirements for uMRD at & lt;10−4 sensitivity (uMRD4) by flow cytometry are met (Figure). Adult patients with CLL/SLL who met International Workshop on CLL (iwCLL) criteria for treatment (Hallek, Blood 2008;111:5446-56) are eligible if they have central verification of del(17p) by fluorescence in situ hybridization with & gt;7% aberrant nuclei present. Initial safety and tolerability of zanubrutinib and venetoclax combination therapy will be assessed, including the risk of TLS at baseline and before initiation of venetoclax. Responses will be assessed by investigator for CLL per modified iwCLL criteria (Hallek, Blood 2008;111:5446-56. Cheson, JCO 2012;30:2820-2) and for SLL per Lugano criteria (Cheson, JCO 2014;32:3059-68). Secondary endpoints include ORR, progression-free survival, duration of response, rate of uMRD4 at various time points, safety, and pharmacokinetics of zanubrutinib and venetoclax. Exploratory endpoints include overall survival, patient-reported outcomes, and time to recurrence of detectable MRD after discontinuation of zanubrutinib and/or venetoclax. Recruitment began in November 2019 and is ongoing in 8 countries. Figure 1 Disclosures Tam: Janssen: Honoraria, Research Funding; AbbVie: Honoraria, Research Funding; BeiGene: Honoraria. Flinn:Novartis: Research Funding; Nurix Therapeutics: Consultancy; Portola Pharmaceuticals: Research Funding; Gilead Sciences: Consultancy, Research Funding; Forty Seven: Research Funding; Trillium Therapeutics: Research Funding; TG Therapeutics: Consultancy, Research Funding; F. Hoffmann-La Roche: Research Funding; Incyte: Research Funding; Curis: Research Funding; Calithera Biosciences: Research Funding; Karyopharm Therapeutics: Research Funding; Juno Therapeutics: Consultancy, Research Funding; Acerta Pharma: Research Funding; Great Point Partners: Consultancy; Genentech, Inc.: Research Funding; Loxo: Research Funding; Celgene: Research Funding; MorphoSys: Consultancy, Research Funding; Curio Science: Consultancy; Merck: Research Funding; Constellation Pharmaceuticals: Research Funding; Forma Therapeutics: Research Funding; Verastem: Consultancy, Research Funding; Yingli Pharmaceuticals ≠: Consultancy, Research Funding; Rhizen Pharmaceuticals: Research Funding; Johnson & Johnson: Other; Roche: Consultancy, Research Funding; Vincera Pharma: Consultancy; ArQule: Research Funding; Agios: Research Funding; AstraZeneca: Consultancy, Research Funding; BeiGene: Consultancy, Research Funding; Kite Pharma: Consultancy, Research Funding; IGM Biosciences: Research Funding; Takeda: Consultancy, Research Funding; Infinity Pharmaceuticals: Research Funding; Unum Therapeutics: Consultancy, Research Funding; Triphase Research & Development Corp.: Research Funding; Teva: Research Funding; Seattle Genetics: Consultancy, Research Funding; Iksuda Therapeutics: Consultancy; Janssen: Consultancy, Research Funding; AbbVie: Consultancy, Research Funding; Pfizer: Research Funding; Pharmacyclics LLC, an AbbVie Company: Consultancy, Research Funding. Tedeschi:Department of Hematology Niguarda Hospital Milano: Current Employment; Janssen spa: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; AstraZeneca: Consultancy, Membership on an entity's Board of Directors or advisory committees; BeiGene: Consultancy, Membership on an entity's Board of Directors or advisory committees; AbbVie: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Sunesis: Consultancy. Ferrant:AbbVie: Honoraria, Membership on an entity's Board of Directors or advisory committees. Brown:BeiGene: Consultancy; Genentech: Consultancy; Gilead: Consultancy, Research Funding; Acerta: Consultancy; Sun: Research Funding; Loxo: Consultancy, Research Funding; Verastem: Consultancy, Research Funding; TG Therapeutics: Consultancy; Sunesis: Consultancy; Rigel Pharmaceuticals: Consultancy; Pfizer: Consultancy; Octapharma: Consultancy; Novartis: Consultancy; Nextcea: Consultancy; MEI Pharma: Consultancy; Invectys: Membership on an entity's Board of Directors or advisory committees, Other: DSMC; Astra-Zeneca: Consultancy; Janssen: Honoraria; Morphosys: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other; Catapult: Consultancy; Dynamo Therapeutics: Consultancy; Eli Lilly and Company: Consultancy; Juno/Celgene: Consultancy; Kite: Consultancy; AbbVie: Consultancy; Pharmacyclics: Consultancy. Robak:GSK: Research Funding; Bristol Meyers Squibb: Research Funding; Roche: Consultancy, Other: TRAVEL, ACCOMMODATIONS, EXPENSES (paid by any for-profit health care company), Research Funding; AstraZeneca: Honoraria, Research Funding; Acerta: Research Funding; Janssen: Consultancy, Honoraria, Other: TRAVEL, ACCOMMODATIONS, EXPENSES (paid by any for-profit health care company), Research Funding; BioGene: Honoraria, Research Funding; Pharmacyclics LLC, an AbbVie Company: Honoraria, Research Funding; UCB: Honoraria, Research Funding; Medical University of Lodz: Current Employment; Momenta: Consultancy; Takeda: Consultancy; Octapharma: Honoraria; Morphosys: Research Funding; Novartis: Honoraria, Research Funding; Sandoz: Consultancy, Honoraria; AbbVie: Consultancy, Honoraria, Other: TRAVEL, ACCOMMODATIONS, EXPENSES (paid by any for-profit health care company), Research Funding; UTX-TGR: Research Funding; Pfizer: Research Funding. Ghia:Gilead: Consultancy, Honoraria, Research Funding; ArQule: Consultancy, Honoraria; Acerta/AstraZeneca: Consultancy, Honoraria; BeiGene: Consultancy, Honoraria; Janssen: Consultancy, Honoraria, Other: TRAVEL, ACCOMMODATIONS, EXPENSES (paid by any for-profit health care company), Research Funding; Celgene/Juno: Consultancy, Honoraria; Lilly: Consultancy, Honoraria; MEI: Consultancy, Honoraria; Sunesis: Consultancy, Honoraria, Research Funding; Adaptive, Dynamo: Consultancy, Honoraria; Novartis: Research Funding; AbbVie: Consultancy, Honoraria, Other: TRAVEL, ACCOMMODATIONS, EXPENSES (paid by any for-profit health care company), Research Funding. Kuwahara:BeiGene: Current Employment, Current equity holder in publicly-traded company, Other: TRAVEL, ACCOMMODATIONS, EXPENSES (paid by any for-profit health care company). Paik:BeiGene: Current Employment, Current equity holder in publicly-traded company. Hua:BeiGene USA Ltd.: Current Employment, Current equity holder in publicly-traded company, Other: TRAVEL, ACCOMMODATIONS, EXPENSES (paid by any for-profit health care company); Agios Pharmaceuticals Inc.: Current equity holder in publicly-traded company, Ended employment in the past 24 months; Vertex: Current equity holder in publicly-traded company. Cohen:BeiGene: Current Employment, Current equity holder in publicly-traded company, Other: TRAVEL, ACCOMMODATIONS, EXPENSES (paid by any for-profit health care company). Huang:BeiGene: Current Employment, Current equity holder in publicly-traded company, Other: TRAVEL, ACCOMMODATIONS, EXPENSES (paid by any for-profit health care company). Hillmen:Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: TRAVEL, ACCOMMODATIONS, EXPENSES (paid by any for-profit health care company), Research Funding, Speakers Bureau; AbbVie: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: TRAVEL, ACCOMMODATIONS, EXPENSES (paid by any for-profit health care company), Research Funding, Speakers Bureau; Astra Zeneca: Honoraria; F. Hoffmann-La Roche: Honoraria, Research Funding; Pharmacyclics: Research Funding; Gilead: Research Funding. OffLabel Disclosure: Zanubrutinib has not been approved for TN CLL/SLL with del(17p) in the US