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TPS1123 Background: TTK (Threonine Tyrosine Kinase also known as Monopolar spindle 1 [Mps1]), is a dual-specificity serine-threonine kinase critical for anaphase promoting complex/cyclosome inhibition at the spindle assembly checkpoint, and is required for chromosome alignment and error correction. Inhibition of TTK causes cells to prematurely exit mitosis with unattached chromosomes, resulting in aneuploidy and cell death. Higher TTK tumor levels correlate with worse prognosis and may contribute to the survival and proliferation of aneuploid cells. CFI-402257, a potent and selective inhibitor of TTK inhibits the growth of a variety of human cancer-derived cell lines with IC50 of 8-40 nM. A first-in-human phase 1 study of CFI-402257 administered orally as a single agent, demonstrated a tolerable safety profile and evidence of clinical activity in patients with advanced solid tumors. The MTD was 168 mg daily, and the study expanded to 3 cohorts: solid tumors, HER2-negative breast cancer, and hormone receptor positive (HR+/HER2-) breast cancer in combination with fulvestrant. The dose limiting toxicity was manageable and reversible dose-dependent neutropenia. Investigator-confirmed partial responses (cPR) were observed in 5 patients (10.6%) with 25 (53.2%) exhibiting disease control. In the HR+/HER2- breast cancer population previously treated with cyclin dependent kinase 4/6 inhibitors (CDK4/6i) and aromatase inhibitors, there were 4 cPR’s with a median duration of response of 256 days, with responses emerging after 2 cycles of therapy. Responses were observed with CFI-402257 as a single agent and in combination with fulvestrant. Based on these data, study TWT-203 will focus on advanced solid tumors and advanced HR+/HER2- breast cancers in combination with an approved endocrine therapy. Methods: Safety and clinical activity of CFI-402257 monotherapy will be evaluated in patients with advanced solid tumors (Part A) or in combination with fulvestrant in patients with HR+/HER2- advanced breast cancer (Part B). Part A will confirm the RP2D using a 3+3 design with a starting dose of 126 mg daily. Part B evaluates CFI-402257 in combination with fulvestrant in patients with HR+/HER2- advanced breast cancer following progression on prior CDK4/6i and endocrine therapy. Initially 6 patients will be treated with CFI-402257 and fulvestrant, and safety, tolerability, and PK evaluated, with further expansion to confirm the RP2D and characterize CFI-402257 activity. Efficacy endpoints include overall response rate and disease control rate. Safety endpoints include incidence of treatment emergent adverse events. Exploratory objectives include characterization of protein and molecular alterations relevant to the cell cycle and CFI-402257 response.

Background: CFI-400945 is a potent, selective, orally administered, first-in-class inhibitor of the serine/threonine kinase, Polo-like kinase 4 (PLK4). PLK4 is a highly conserved master upstream regulator of centriole duplication and is critical for maintenance of genomic integrity. Aberrant expression of PLK4 results in a number of effects including the centrosome amplification often seen in aneuploid cancers, pointing to a potentially causative role for PLK4 in genome instability and cancer progression. A Phase 1 study has been completed evaluating CFI-400945 as a monotherapy in solid tumors, showing a tolerable safety profile and promising signs of activity. Given acute myeloid leukemia (AML) is characterized by genomic instability, CFI-400945 has been evaluated in pre-clinical and clinical studies in AML. In pre-clinical studies, CFI-400945 showed potent activity towards leukemia cell lines and primary human samples in vitro, as well as marked efficacy in two subcutaneous models of leukemia. A prior Phase 1 trial in AML was initiated at the Princess Margaret Cancer Center (PMCC), and of six patients evaluable for response, two (33%) achieved complete remission (CR) at 96 mg and 128 mg, and 3 patients (50%) had stable disease (with one patient having a 78% reduction in marrow blast count) at 64 mg (2 patients) and 96 mg [re: Murphy et al, ASH 2020]. Responses were seen in patients with adverse cytogenetics. The optimal dosing of CFI-400945 and its potential role as a combination agent are not yet clinically defined. Study Design and Methods: The study (TWT-202) has 4 parts, Part 1A (1A): a single agent dose escalation portion, Part 1B (1B): a food effect portion once the MTD of 1A is determined, and combinations with azacitidine (2A), and decitabine (2B). TWT-202 uses an updated version of investigational product which is identical in formulation to the drug used in the PMCC study, but which may result in higher exposures at a given dose. This study will therefore refine the dose through escalation cohorts. For parts 1A and 1B, patients with relapsed and/or refractory AML, MDS, or CMML after >1 prior therapy will be included. Patients with MDS or CMML must have progressed or had a lack of response after at least 4 cycles of hypomethylating agents. For parts 2A and 2B, patients should have relapsed and/or refractory AML or untreated MDS or CMML. Untreated patients who decline or are ineligible for intensive therapy may be included. The study will use a standard 3 + 3 design. The maximum tolerated dose (MTD) will be defined as the dose level where the number of dose limiting toxicities (DLTs) is Results: As of June 21, 2021, 2 patients had been enrolled into the study, one of the patients (50%) received >3 prior therapies (including venetoclax). Neither patient had had stem cell transplant at study entry. Both patients had secondary AML (one with antecedent MDS with excess blasts and the other with CMML). Both patients received 32 mg of CFI-400945 for 21 days followed by a 7-day rest. Both patients completed cycle 1 and neither experienced a DLT. Both patients experienced a single serious treatment emergent adverse event (SAE) of febrile neutropenia each, with neither event considered related to CFI-400945. There were 13 Grade 3 or greater TEAE's, including anemia, thrombocytopenia (3 events each), febrile neutropenia (2 events), agitation, angioinvasive fungal sinusitis, acute kidney injury, hypotension and neutropenia (1 event each). None of the grade 3 or greater TEAE's were considered related to CFI-400945. Neither patient responded to therapy at 32 mg and both came off treatment after one cycle due to progressive disease. PK and PD studies are pending. Conclusion: CFI-400945 has been generally well tolerated and TWT-202 continues to enroll in the Part 1A and Part 1B monotherapy cohorts. Updated safety, efficacy, PK, and PD data for the study will be presented at the time of the meeting. Disclosures Borthakur: University of Texas MD Anderson Cancer Center: Current Employment; ArgenX: Membership on an entity's Board of Directors or advisory committees; Protagonist: Consultancy; Astex: Research Funding; Ryvu: Research Funding; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees; GSK: Consultancy; Takeda: Membership on an entity's Board of Directors or advisory committees. Jonas: 47, AbbVie, Accelerated Medical Diagnostics, Amgen, AROG, Celgene, Daiichi Sankyo, F. Hoffmann-La Roche, Forma, Genentech/Roche, Gilead, GlycoMimetics, Hanmi, Immune-Onc, Incyte, Jazz, Loxo Oncology, Pfizer, Pharmacyclics, Sigma Tau, Treadwell: Research Funding; AbbVie: Other: Travel reimbursement; AbbVie, BMS, Genentech, GlycoMimetics, Jazz, Pfizer, Takeda, Treadwell: Consultancy. Roberts-Thomson: Treadwell Therapeutics: Current Employment. Michelson: Treadwell Therapeutics: Consultancy. Bray: Treadwell Therapeutics: Current Employment.

BackgroundCFI-402411 is an orally available small molecule potent inhibitor of HPK1 (Hematopoietic progenitor kinase 1). T-cells are negatively-regulated at different junctures of cancer-immunity cycle by this regulatory kinase. HPK1, (also mitogen activated protein kinase kinase kinase kinase 1 (MAP4K1)) is a protein serine/threonine kinase predominantly expressed in hematopoietic cells. In T-cells, following T-cell receptor activation, HPK1 is recruited to the plasma membrane where it phosphorylates the adapter protein SH2 domain-containing leukocyte protein of 76 kDa (SLP-76), down-regulating signaling events required for T cell activation and proliferation. Selected for development based on its pharmacologic properties and preclinical activity in a variety of syngeneic cancer models and assays, with an IC50 = 4.0±1.3 nM, CFI-402411 is expected to relieve HPK1-mediated inhibition of T and B cells, facilitating an anti-tumor immune response.MethodsPhase 1, 3 + 3 design in patients. Patients have acceptable laboratory, other parameters for study entry. Single agent dose daily oral escalation cohort (A1) in advanced tumors, then dose expansion (A3) with biomarker backfill (A2) in select advanced tumors; combination with PD-1 Inhibitor (pembrolizumab) (B1, pembrolizumab eligible tumors with no prior grade >=3 related to CPI)) and expansion (B2, PD-1/PD-L1 naïve pembrolizumab eligible tumors). DLT defined as any grade >=3 toxicity in first cycle of therapy (21d cycles). Standard assessments for response per RECIST v1.1 or iRECIST. The starting dose level was 80mg.ResultsAt 10 June 2021 data is available for 12 patients from A1. Median age 61.5 years (range 33–73), 8 patients female, and 10 white. Diagnoses were pancreatic cancer, colorectal (3 pts), ovarian, basal cell, cholangiocarcinoma, sigmoid, salivary and breast cancer (1 pt). Six patients (50%) had 4 prior therapies, 1 patient (basal cell) had prior treatment with immune checkpoint inhibitor, pembrolizumab. Four doses studied: 80, 120, 180 and 270mg. TEAEs across all CTCAE grades, (in >2 patients) were diarrhea (6 patients), nausea (4 patients), dyspepsia (3 patients), fatigue (3 patients). No related grade 3–5 events, one immune related event (grade 1, weight loss). 3 grade 3 events all unrelated to study drug - pleural effusion, rash, thromboembolic event. Discontinuation due to disease progression was main reason (7 patients). PK and PD assessments will be updated at time of presentation.ConclusionsCFI-402411 is a potent inhibitor of HPK1 that is well tolerated with a manageable adverse event profile and dose escalations continue. Further safety and efficacy results will be presented at the meeting including additional cohorts if available.AcknowledgementsTreadwell Therapeutics thanks all sites, importantly their patients and their families.Trial RegistrationClinicalTrials.gov Identifier: NCT04521413Ethics ApprovalThis study obtained has obtained ethics approvals at multiple institutions globally including;USAWCG IRB - Western Institutional Review Board - MOD00002618 (Submission ID)IntegReview Institutional Review Board - N/AAdvarra Central IRB - SSU00130103IntegReview Institutional Review Board N/AAdvarra Central IRB - SSU00137751Advarra Central IRB - SSU00143275The University of Texas MD Anderson Cancer Center Institutional Review Board - 2020–0678 (IRB ID Number)Hong KongJoint Chinese University of Hong Kong - New Territories East Cluster Clinical Research Ethics Committee - 2020.367 (Ref Number)CanadaOntario Cancer Research Ethics Board - 3320 (Project ID)Health Research Ethics Board of Alberta, HREBA Cancer Committee - HREBA.CC-20–0504 (Ethics ID Number)South KoreaimCORE - Seoul National University Hospital Institutional Review Board - H-2012-094-1182 (IRB Number)National Cancer Institute Review Board - 2020–0525–0001 (Receipt Number)All participants gave informed consent before taking part in this clinical trial.

Background: CFI-400945 is a potent, selective, orally administered, first-in-class inhibitor of the serine/threonine kinase, Polo-like kinase 4 (PLK4). PLK4 is a highly conserved master regulator of centriole duplication, and is critical for maintenance of genomic integrity. Aberrant expression of PLK4 results in a number of effects including the centrosome amplification often seen in aneuploid cancers, pointing to a potentially causative role for PLK4 in genome instability and cancer progression. A Phase 1 study has been completed evaluating CFI-400945 as a monotherapy in solid tumors, showing a tolerable safety profile and promising signs of activity. As acute myeloid leukemia (AML) is a disease characterized by genomic instability, it is of significant interest as a potential indication for the clinical evaluation of CFI-400945. pre-clinical studies, CFI-400945 showed potent activity towards leukemia cell lines and primary human samples in vitro, as well as marked efficacy in two subcutaneous models of leukemia, specifically the MV4-11 FLT3-ITD AML. A Phase 1 trial in AML was initiated at the Princess Margaret Cancer Center in 2018, and of six patients evaluable for response, two (33%) achieved complete remission (CR), and 3 patients (50%) had stable disease (with one patient having a 78% reduction in marrow blast count) [re: Murphy et al, ASH 2020]. These promising results have led to a plan for an expanded trial examining CFI-400945 in AML, particularly focused on complex karyotype (CK). Study Design and Methods: The study will have 4 parts, Part 1A (1A): a single agent dose escalation portion, Part 1B (1B): a food effect portion once the MTD of 1A is determined, and combinations with azacitidine (2A), and decitabine (2B). For parts 1A and 1B, patients with relapsed and/or refractory AML, MDS, or CMML after >1 prior therapy will be included. Patients with MDS or CMML must have progressed or had a lack of response after at least 4 cycles of hypomethylating agents. For parts 2A and 2B, patients should have relapsed and/or refractory AML or untreated MDS or CMML. Untreated patients who decline or are ineligible for intensive therapy may be included. The study will use a standard 3 + 3 design. The maximum tolerated dose (MTD) will be defined as the dose level where the number of dose limiting toxicities (DLTs) is Biomarker Selection and companion Diagnostics: No biomarker based pre-selection of patients. PD evaluations will include blast reduction and markers of mitosis. Study Treatment and Endpoints: Part 1: Each cycle will be 28 days (21 days on/7 days off). Starting does of CFI-400945 will be 32mg po. Once the MTD of 1A is determined, 1B will explore the food effect of a high fat meal on the PK of CFI-400945 at the MTD. 2A and 2B will explore the combination of CFI-400945 with standard dose of either azacitidine (2A) or decitabine (2B). The starting dose of CFI-400945 will be 32mg po for 21 days on/7 off. The DLTs will be defined as NCI CTCAE V5.0 Grade >3 related non-hematologic event(s) occurring during cycle 1 or prolonged pancytopenia in the presence of a hypocellular bone marrow > day 42 without evidence of disease. The efficacy endpoints for AML, MDS, and CMML include the overall response rate, and the CR rate per standard criteria. The aim of the food effect part of the study is the asses the effect of high fat food on the PK of CFI-400945. The safety endpoint is the incidence of treatment emergent adverse events. PK endpoints include evaluations of parameters such as half-life, AUC, etc. Exploratory endpoints include eval of minimal residual disease, genomic alterations and other molecular features associated with response and biological effects of PLK4 inhibition. Disclosures Jonas: Amgen: Consultancy, Other: TRAVEL, ACCOMMODATIONS, EXPENSES (paid by any for-profit health care company), Research Funding; AbbVie: Consultancy, Other: TRAVEL, ACCOMMODATIONS, EXPENSES (paid by any for-profit health care company), Research Funding; GlycoMimetics: Consultancy, Other: TRAVEL, ACCOMMODATIONS, EXPENSES (paid by any for-profit health care company), Research Funding; Sigma Tau: Research Funding; Jazz: Consultancy, Research Funding; Celgene: Consultancy, Research Funding; Takeda: Consultancy; Tolero: Consultancy; Treadwell: Consultancy; Forty Seven: Research Funding; Accelerated Medical Diagnostics: Research Funding; AROG: Research Funding; Daiichi Sankyo: Research Funding; F. Hoffmann-La Roche: Research Funding; Forma: Research Funding; Genentech/Roche: Research Funding; Hanmi: Research Funding; Incyte: Research Funding; LP Therapeutics: Research Funding; Pfizer: Research Funding; Pharmacyclics: Research Funding. Bixby:GlycoMimetics: Research Funding. Brandwein:Pfizer: Honoraria; Amgen: Honoraria; Celgene: Honoraria; Astellas: Honoraria; Taiho: Honoraria; Roche: Honoraria; Jazz Pharmaceuticals: Honoraria. Michelson:Treadwell Therapeutics: Consultancy. Bray:TIO Discovery: Current Employment; Treadwell Therapeutics: Current Employment. Roberts-Thomson:Treadwell Therapeutics: Current Employment. Borthakur:BioTherix: Consultancy; FTC Therapeutics: Consultancy; Nkarta Therapeutics: Consultancy; Treadwell Therapeutics: Consultancy; PTC Therapeutics: Consultancy; Argenx: Consultancy; Oncoceutics: Research Funding; Xbiotech USA: Research Funding; Polaris: Research Funding; AstraZeneca: Research Funding; BMS: Research Funding; BioLine Rx: Research Funding; Jannsen: Research Funding; Abbvie: Research Funding; Novartis: Research Funding; Incyte: Research Funding; BioLine Rx: Consultancy; PTC Therapeutics: Research Funding; Curio Science LLC: Consultancy; Cyclacel: Research Funding; GSK: Research Funding.

Purpose: Preclinical studies suggest SYK and JAK contribute to tumor-intrinsic and microenvironment-derived survival signals. The pharmacodynamics of cerdulatinib, a dual SYK/JAK inhibitor, and associations with tumor response were investigated. Patients and Methods: In a phase I dose-escalation study in adults with relapsed/refractory B-cell malignancies, cerdulatinib was administered orally to sequential dose-escalation cohorts using once-daily or twice-daily schedules. The study enrolled 8 patients with chronic lymphocytic leukemia (CLL)/small lymphocytic lymphoma (SLL), 13 with follicular lymphoma, 16 with diffuse large B-cell lymphoma (DLBCL), and 6 with mantle cell lymphoma. Correlation of tumor response with pharmacodynamic markers was determined in patients with meaningful clinical responses. Results: Following cerdulatinib administration, complete SYK and JAK pathway inhibition was achieved in whole blood of patients at tolerated exposures. Target inhibition correlated with serum cerdulatinib concentration, and IC50 values against B-cell antigen receptor (BCR), IL2, IL4, and IL6 signaling pathways were 0.27 to 1.11 μmol/L, depending on the phosphorylation event. Significant correlations were observed between SYK and JAK pathway inhibition and tumor response. Serum inflammation markers were reduced by cerdulatinib, and several significantly correlated with tumor response. Diminished expression of CD69 and CD86 (B-cell activation markers), CD5 (negative regulator of BCR signaling), and enhanced expression of CXCR4 were observed in 2 patients with CLL, consistent with BCR and IL4 suppression and loss of proliferative capacity. Conclusions: Cerdulatinib potently and selectively inhibited SYK/JAK signaling at tolerated exposures in patients with relapsed/refractory B-cell malignancies. The extent of target inhibition in whole-blood assays and suppression of inflammation correlated with tumor response. (ClinicalTrials.gov ID:NCT01994382).

Background: Despite recent advances, follicular lymphoma (FL) remains incurable for most patients. Relapsed/refractory (r/r) FL is associated with decremental treatment responses, accumulating toxicity, and poor survival among early failures of 1st line chemoimmunotherapy. Underscored by the recent approvals of idelalisib, copanlisib, and duvelisib, targeting B-cell receptor (BCR) signaling produces ORR of ~50% in r/r patients; however, new agents with a better therapeutic index over long-term administration are needed. SYK is a key regulator of BCR signaling (upstream of BTK and PI3K), and its inhibition results in clinical activity in FL. Compared with unaffected nodes, lymph nodes from FL patients have greater numbers of follicular helper T cells that express high levels of IL-4, which may support the tumor via the JAK1/3 pathway. Cerdulatinib, an oral, reversible inhibitor of SYK and JAK kinases (JAK1, JAK3, TYK2), previously reported a ~45% overall response rate (ORR) in r/r FL as a single agent. Xenograft studies suggest cerdulatinib may combine with rituximab to enhance antitumor activity. We report updated results from a phase 2a study of single-agent cerdulatinib and initial results in combination with rituximab in r/r FL. Methods: This phase 2a study confirmed the safety and efficacy of cerdulatinib 30 mg BID in r/r B- and T-cell lymphoma patients. Dose reductions were permitted to 15 mg BID. Response was assessed by Lugano criteria. Results: A planned interim analysis was performed on July 18, 2019, in which enrollment was 40 patients in the single-agent cohort and 19 patients in the rituximab combination cohort. For the single-agent cohort, median age (range) was 64 (42-81) years and median prior therapies (range) was 3 (1-9). Ninety-five percent of patients had prior anti-CD20 therapy, and 25% had prior therapy with BCR pathway inhibitors. For the combination cohort, median age (range) was 67 (47-85) years and median prior therapies (range) was 3 (1-10). Eighty-eight percent of patients had prior anti-CD20 therapy, and 32% had prior therapy with BCR pathway inhibitors. The safety profile appeared similar in both cohorts. The most common treatment-emergent grade 3+ adverse events in ≥5% of patients for both cohorts were lipase increase (27%), neutropenia (18%), diarrhea (12%), amylase increase (10%), hypertension (8%), nausea (7%), and pneumonia (5%). Grade 3+ infections occurred in 17.5% of single-agent cohort patients and 15.8% of combination cohort patients. Amylase and lipase increases generally were not associated with abdominal pain or pancreatitis. In addition, to date there has been no evidence of cumulative toxicity. The ORR was 45% as a single agent (12.5% complete response [CR], 32.5% partial response [PR], with 25% stable disease [SD] and 5% progressive disease [PD] in 40 evaluable patients) and 59% in the combination cohort (11.7% CR, 47% PR, with 27.8% SD and no PD in 17 evaluable patients). Responses typically occurred after 2 cycles, generally improved over time, and were durable in the single-agent cohort, with 10 patients on drug for >1 year. Enrollment in the combination cohort is ongoing. Updated safety and efficacy will be presented. Conclusion: The recommended cerdulatinib phase 2 dose of 30 mg BID was tolerable and efficacious in heavily pretreated r/r FL. The cerdulatinib + rituximab combination appears to be well tolerated, with tumor reductions in all evaluable patients. The safety profile and unique mechanism of action of cerdulatinib support further combination studies in FL. Disclosures Smith: Pharmacyclics: Research Funding; Denovo Biopharma: Research Funding; Portola Pharmaceuticals: Research Funding; Seattle Genetics: Research Funding; Acerta Pharma BV: Research Funding; AstraZeneca: Membership on an entity's Board of Directors or advisory committees, Research Funding; Incyte Corporation: Research Funding; Genentech: Research Funding; Bristol-Myers Squibb (spouse): Research Funding; Ignyta (spouse): Research Funding; Ayala (spouse): Research Funding; Merck Sharp & Dohme Corp: Consultancy, Research Funding. Munoz:AstraZeneca: Speakers Bureau; Pharmacyclics LLC an AbbVie Company: Consultancy, Research Funding, Speakers Bureau; Kite Pharma: Consultancy, Research Funding, Speakers Bureau; Gilead: Consultancy, Speakers Bureau; Fosunkite: Speakers Bureau; Kyowa: Consultancy, Honoraria, Speakers Bureau; Bayer: Consultancy, Speakers Bureau; Seattle Genetics: Consultancy, Honoraria, Research Funding; Celgene: Research Funding; Portola: Research Funding; Incyte: Research Funding. Stevens:Astellas: Consultancy. Smith:Portola Pharmaceuticals: Research Funding. Feldman:Kite Pharma: Honoraria, Other: Travel expenses, Speakers Bureau; Janssen: Honoraria, Speakers Bureau; Takeda: Honoraria, Speakers Bureau; Bayer: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Seattle Genetics: Consultancy, Honoraria, Other: Travel expenses, Speakers Bureau; Pharmacyclics: Honoraria, Other: Travel expenses, Speakers Bureau; AbbVie: Honoraria, Other: Travel expenses, Speakers Bureau; Viracta: Research Funding; Trillium: Research Funding; Roche: Research Funding; Amgen: Research Funding; Cell Medica: Research Funding; Roche: Research Funding; Corvus: Research Funding; Eisai: Research Funding; Kyowa Hakko Kirin: Research Funding; Pfizer: Research Funding; Portola Pharma: Research Funding; Celgene: Honoraria, Research Funding, Speakers Bureau. Ye:MingSight: Research Funding; Janssen: Research Funding; Karyopharm: Research Funding; Sanofi: Research Funding; Onyx: Research Funding; Celgene: Research Funding; Takeda: Research Funding; AbbVie: Research Funding; Portola Pharmaceuticals: Research Funding. de Vos:Verastem: Consultancy; Portola Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; Bayer: Consultancy. Miller:Verastem: Consultancy, Honoraria, Research Funding, Speakers Bureau; Incyte: Consultancy, Honoraria, Research Funding, Speakers Bureau; Novartis: Honoraria, Research Funding, Speakers Bureau; Takeda: Honoraria, Research Funding, Speakers Bureau. Birrell:Portola Pharmaceuticals: Employment, Equity Ownership. Leeds:Portola Pharmaceuticals: Employment, Equity Ownership. Coffey:Portola Pharmaceuticals: Employment, Equity Ownership, Research Funding. Conley:Portola Pharmaceuticals: Employment, Equity Ownership. Michelson:Portola Pharmaceuticals: Employment, Equity Ownership. Curnutte:Portola Pharmaceuticals: Employment, Equity Ownership.

Background: SYK and JAK signaling pathways may be critical mediators in the pathogenesis of peripheral T-cell lymphoma (PTCL) and cutaneous T-cell lymphoma (CTCL). SYK expression is observed in these malignant cells, and pre-clinical data suggest it acts as an oncogenic driver possibly by mediating chronic T-cell antigen receptor-independent signaling. Consistently, transgenic expression of constitutively active SYK in CD4+ T cells in mice results in a lethal T-cell proliferative disease, while its expression in B cells did not result in clonal expansion. Moreover, evidence for JAK/STAT pathway involvement in these diseases has been demonstrated by gene expression profiling, and frequent activating mutations to common γ chain, JAK1, JAK3, or STAT5b are observed in PTCL. Malignant T-cell clones from CTCL patients secrete a host of Th2 cytokines (IL-3, IL-4, IL-5, IL-6, IL-10, and IL-13) and exhibit deregulation of the IL-2 receptor signaling pathway. These cytokines induce JAK/STAT signaling, which may promote T-cell proliferation and survival. Overall, the data suggest that dual inhibition of SYK and JAK may perturb multiple and independent survival mechanisms implicated in PTCL and CTCL. Cerdulatinib is a small-molecule reversible ATP competitive inhibitor of SYK and JAK family members. Results of cerdulatinib single-agent 30 mg BID in a phase 2a dose expansion study in patients with PTCL and CTCL are reported here. Methods: Patients with relapsed/refractory PTCL or CTCL who received at least 1 prior systemic therapy were eligible to be treated with cerdulatinib at 30 mg orally BID. These expansion cohorts were enrolled in 2 stages: initially 20 patients accrued and, if ≥3 responses were observed, the cohort was expanded. The primary endpoint is response according to either the Lugano criteria (PTCL) or Global Assessment (CTCL). Patients are treated until progression, intolerance, or response adequate to allow stem cell transplantation. All patients receive antimicrobial prophylaxis (typically sulfamethoxazole and trimethoprim [Bactrim]). Results: An interim analysis of 61 patients with PTCL and 37 with CTCL who received cerdulatinib as a single agent was performed on July 18, 2019. Patient characteristics: median (range) age: PTCL: 65 (21-85) years and CTCL: 62 (24-80) years; median prior systemic therapies: PTCL: 2 (1-12) and CTCL: 5 (1-16); refractory to last therapy: PTCL: 48% and CTCL: 62%. For PTCL and CTCL combined, 41% of patients received prior romidepsin, 5% received prior belinostat, 12% received prior pralatrexate, and 32% received prior brentuximab. In the PTCL cohort, 60 patients were evaluable for response (overall response rate [ORR] of 35%). Responses were primarily seen in AITL/TFH subtype (ORR of 55% [12 of 22], of which 41% of patients achieved a complete response [CR]). Responses have additionally been observed in patients with PTCL-NOS, ATLL, ALCL, and gamma-delta TCL. The ORR in CTCL patients was 35%, with the greatest activity observed in mycosis fungoides (ORR of 45%, of which 9% of patients achieved CR) versus Sezary syndrome (ORR of 17%, with no CR). Rapid improvements in pruritus have been observed in CTCL patients, independent of tumor response. Median duration of response is pending for both cohorts, but several patients have been in response for over a year. Among all patients, the most common (>5% incidence) treatment-emergent grade 3+ adverse events were lipase increase (21%) and amylase increase (18%), diarrhea (8%), neutropenia (8%), anemia (7%), and fatigue (6%). Grade 3+ infections occurred in 29% of patients, which were generally managed by standard care. The amylase and lipase increases occurred without clinical pancreatitis and resolved irrespective of dose modification. Conclusion: Cerdulatinib has shown good tolerability and clinical activity in PTCL and CTCL. Complete and durable responses across a spectrum of PTCL and CTCL subtypes were observed. Correlative studies are aimed at identifying predictors of response and resistance. This phase 2a study will inform the design of a pivotal trial in T-cell lymphoma. Disclosures Horwitz: Aileron: Research Funding; Infinity/Verastem: Consultancy, Research Funding; Kyowa Hakko Kirin: Consultancy; Millennium/Takeda: Consultancy, Research Funding; Mundipharma: Consultancy; Corvus Pharmaceuticals: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Astex: Consultancy; Innate Pharma: Consultancy; ADCT Therapeutics: Research Funding; Miragen: Consultancy; Seattle Genetics: Consultancy, Research Funding; Kura: Consultancy; Millennium/Takeda: Consultancy, Research Funding; Affimed: Consultancy; Affimed: Consultancy; Celgene: Consultancy, Research Funding; Celgene: Consultancy, Research Funding; Kura: Consultancy; Trillium: Research Funding; Astex: Consultancy; Aileron: Research Funding; Forty-Seven: Research Funding; Forty-Seven: Research Funding; Trillium: Research Funding; Infinity/Verastem: Consultancy, Research Funding; Mundipharma: Consultancy; Seattle Genetics: Consultancy, Research Funding; Corvus Pharmaceuticals: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Millennium/Takeda: Consultancy, Research Funding; Miragen: Consultancy; Miragen: Consultancy; Mundipharma: Consultancy; Seattle Genetics: Consultancy, Research Funding; Portola: Consultancy; Forty-Seven: Research Funding; Trillium: Research Funding; Forty-Seven: Research Funding; Kyowa Hakko Kirin: Consultancy; Millennium/Takeda: Consultancy, Research Funding; Astex: Consultancy; ADCT Therapeutics: Research Funding; Innate Pharma: Consultancy; Innate Pharma: Consultancy; Mundipharma: Consultancy; Portola: Consultancy; ADCT Therapeutics: Research Funding; ADCT Therapeutics: Research Funding; Kyowa Hakko Kirin: Consultancy; Aileron: Research Funding; Aileron: Research Funding; Astex: Consultancy; Kyowa Hakko Kirin: Consultancy; Corvus Pharmaceuticals: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Innate Pharma: Consultancy; Corvus Pharmaceuticals: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Miragen: Consultancy; Infinity/Verastem: Consultancy, Research Funding; Portola: Consultancy; Seattle Genetics: Consultancy, Research Funding; Affimed: Consultancy; Trillium: Research Funding; Kura: Consultancy; Celgene: Consultancy, Research Funding; Celgene: Consultancy, Research Funding; Infinity/Verastem: Consultancy, Research Funding; Kura: Consultancy; Portola: Consultancy; Affimed: Consultancy. Feldman:Pharmacyclics: Honoraria, Other: Travel expenses, Speakers Bureau; Janssen: Honoraria, Speakers Bureau; AbbVie: Honoraria, Other: Travel expenses, Speakers Bureau; Takeda: Honoraria, Speakers Bureau; Celgene: Honoraria, Research Funding, Speakers Bureau; Seattle Genetics: Consultancy, Honoraria, Other: Travel expenses, Speakers Bureau; Viracta: Research Funding; Trillium: Research Funding; Roche: Research Funding; Portola Pharma: Research Funding; Pfizer: Research Funding; Kite Pharma: Honoraria, Other: Travel expenses, Speakers Bureau; Bayer: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Amgen: Research Funding; Cell Medica: Research Funding; Roche: Research Funding; Corvus: Research Funding; Eisai: Research Funding; Kyowa Hakko Kirin: Research Funding. Khodadoust:Corvus Pharmaceuticals: Research Funding. Kim:Eisai: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Innate Pharma: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Neumedicine: Research Funding; Elorac: Research Funding; Merck: Research Funding; Galderma: Research Funding; Corvus: Honoraria, Membership on an entity's Board of Directors or advisory committees; miRagen: Research Funding; Medivir: Honoraria, Membership on an entity's Board of Directors or advisory committees; Soligenix: Research Funding; Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Forty Seven Inc: Research Funding; Trillium: Research Funding; Seattle Genetics: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Horizon: Research Funding; Portola Pharmaceuticals: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Kyowa Hakko Kirin: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding. Munoz:AstraZeneca: Speakers Bureau; Kite Pharma: Consultancy, Research Funding, Speakers Bureau; Pharmacyclics LLC an AbbVie Company: Consultancy, Research Funding, Speakers Bureau; Incyte: Research Funding; Portola: Research Funding; Celgene: Research Funding; Seattle Genetics: Consultancy, Honoraria, Research Funding; Bayer: Consultancy, Speakers Bureau; Kyowa: Consultancy, Honoraria, Speakers Bureau; Fosunkite: Speakers Bureau; Gilead: Consultancy, Speakers Bureau. Patel:Pfizer: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Celgene: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Janssen: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Pharmacyclics: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Exelixis: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Genentech: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Phillips:Celgene: Membership on an entity's Board of Directors or advisory committees; Bayer: Consultancy; Abbvie: Research Funding; Pharmacyclics: Consultancy, Research Funding; Genentech: Consultancy; Seattle Genetics: Consultancy; Gilead: Consultancy; Incyte: Membership on an entity's Board of Directors or advisory committees. Smith:Acerta Pharma BV: Research Funding; AstraZeneca: Membership on an entity's Board of Directors or advisory committees, Research Funding; Bristol-Myers Squibb (spouse): Research Funding; Denovo Biopharma: Research Funding; Genentech: Research Funding; Incyte Corporation: Research Funding; Pharmacyclics: Research Funding; Seattle Genetics: Research Funding; Portola Pharmaceuticals: Research Funding; Ignyta (spouse): Research Funding; Ayala (spouse): Research Funding; Merck Sharp & Dohme Corp: Consultancy, Research Funding. Smith:Portola Pharmaceuticals: Research Funding. Wilcox:Millenium/Takeda: Research Funding; Bristol-Myers Squibb: Research Funding; CTI Biopharma: Research Funding; Incyte: Research Funding. Birrell:Portola Pharmaceuticals: Employment, Equity Ownership. Leeds:Portola Pharmaceuticals: Employment, Equity Ownership. Conley:Portola Pharmaceuticals: Employment, Equity Ownership. Michelson:Portola Pharmaceuticals: Employment, Equity Ownership. Coffey:Portola Pharmaceuticals: Employment, Equity Ownership, Research Funding. Curnutte:Portola Pharmaceuticals: Employment, Equity Ownership.

Purpose: To determine the maximum tolerated dose (MTD) dose-limiting toxicity, and pharmacokinetic and pharmacodynamic profile of TKI258 (formerly CHIR-258). Experimental Design: A phase I dose escalating trial in patients with advanced solid tumors was performed. Treatment was initially as single daily doses on an intermittent 7-day on/7-day off schedule. Following a protocol amendment, a second schedule comprised, during cycle 1, 7-day on/7-day off treatment followed by 14 days of continuous daily dosing; subsequent cycles comprised 28 days of daily dosing. Pharmacokinetics and evaluation of phosphorylated extracellular signal-regulated kinase (ERK) in peripheral blood mononuclear cells were done during the first 28 days of each schedule. Results: Thirty-five patients were treated in four intermittent (25-100 mg/d) and three continuous (100-175 mg/d) dosing cohorts. Observed drug-related toxicities were nausea and vomiting, fatigue, headache, anorexia, and diarrhea. Dose-limiting toxicities were grade 3 hypertension in one patient at 100 mg continuous dosing, grade 3 anorexia in a second patient at 175 mg, and grade 3 alkaline phosphatase elevation in a third patient at 175 mg. One patient had a partial response (melanoma) and two patients had stable disease >6 months. TKI258 pharmacokinetics were linear over the dose range of 25 to 175 mg. Five of 14 evaluable patients had modulation of phosphorylated ERK levels. Conclusions: The MTD was defined as 125 mg/d. Evidence of antitumor activity in melanoma and gastrointestinal stromal tumors warrants further investigation, and other phase I studies are ongoing. Further pharmacodynamic evaluation is required in these studies to evaluate the biological effects of TKI258.

Purpose: The incidence of non-Hodgkin's lymphoma (NHL), the fifth most common malignancy in the United States, has increased over 70% in the last 30 years. Fifty percent to 75% of patients with low-grade or follicular NHL respond to rituximab therapy. However, responses are generally of limited duration, and complete responses are rare. Preclinical work suggests that human recombinant interleukin-2 (rIL-2; aldesleukin, Proleukin) enhances rituximab efficacy. Antibody-dependent cellular cytotoxicity (ADCC) is an important mechanism of action of rituximab. rIL-2 induces expansion and activation of Fc receptor (FcR)–bearing cells, thereby enhancing ADCC. Therefore, a large, multicenter phase 2 trial to assess the effects of rIL-2 on rituximab therapy in patients with rituxumab-refractory low-grade NHL was conducted. Experimental Design: The combination of rituximab and rIL-2 was studied in 57 patients with rituximab-refractory low-grade NHL (i.e., patients must have received a single-agent course of rituximab and showed no tumor response, or had a response lasting Results: Rituximab plus rIL-2 combination therapy was safe and generally well tolerated, but responses were low. Fifty-seven patients were enrolled with 54 evaluable for response; however, only five responses (one complete and four partial) were observed. Correlative data indicate that rIL-2 expanded FcR-bearing cells and enhanced ADCC. However, other factors, such as FcγR polymorphisms in patients refractory to single-agent rituxumab and heterogeneous tumor biology, may have influenced the lack of clinical efficacy seen with this combination therapy. Conclusions: rIL-2 expands FcR-bearing cellular subsets in vivo and enhances in vitro ADCC of rituxumab. However, these findings do not directly translate into meaningful clinical benefit for patients with rituxumab-refractory NHL.

A subgroup of patients with refractory Hodgkin's (HD) or non-Hodgkin's (NHL) lymphoma may be cured with high-dose chemotherapy and peripheral blood progenitor cell rescue. To investigate the relationship of adequate leukapheresis yield and time course of platelet recovery after mobilization chemotherapy, we retrospectively analyzed the leukapheresis yields in seven patients with Hodgkin's disease and fifteen patients with non-Hodgkin's lymphoma undergoing high-dose chemotherapy. Our goal was to develop a rule to determine when to initiate leukapheresis and then to prospectively validate this rule. All patients were mobilized with cyclophosphamide and G-CSF (granulocyte-colony stimulating factor). A total of 144 leukaphereses were completed and analyzed. Based on the CD34 content in the initial harvest product, fifteen patients were defined as poor mobilizers (CD34 < 0.15 × 106/kg) and seven were good mobilizers. The platelet count on the first day of harvesting was significantly associated with the poor mobilizers (P = .03). Age, sex, marrow involvement, disease (HD vs. NHL), prior radiation, time since last chemotherapy, and total number of cycles of prior chemotherapy were not predictive of poor mobilizers. By using a platelet count cut off of 35 × 109/L, we retrospectively analyzed 144 individual leukapheresis products, to test whether CD34 yield was predicted by the peripheral blood platelet count on the day of leukapheresis. This rule had an excellent sensitivity, 91%, and a specificity of 67%. Subsequently, we validated this rule with the next twenty-four patients undergoing leukapheresis of which there were 143 leukaphereses. The prediction rule exhibited a sensitivity of 72% and a specificity of 68% in the validation set. There does appear to be utility in using the platelet count to guide the initiation of leukapheresis after chemotherapy and G-CSF mobilization. J. Clin. Apheresis 14:31–34, 1999.© 1999 Wiley-Liss, Inc.

Abnormal upregulation of NFκB activity is observed in a variety of B cell malignancies, resulting in proliferative and survival signals that contribute to tumor progression. Under normal resting conditions, NFκB is negatively regulated principally via its physical association with IκB (inhibitor of NFκB) family members, thereby inhibiting nuclear transport or access to DNA. In B cells, NFκB is typically activated via various external stimuli (e.g., ligation of the B cell antigen receptor (BCR), toll-like receptors, cytokine receptors, CD40), leading to IκB kinase complex-dependent phosphorylation of IκB members and targeting them for ubiquitination and degradation. In some cases, the need for external stimuli is diminished or completely circumvented by mutations to critical regulators of NFκB, as has been described in the context of activating mutations to CD79A/B, MYD88, and CARD11, as well as inactivation of negative regulators such as A20 and IκB family members (reviewed by Staudt, 2010). Each of these mutations has been observed clinically in patients with B cell malignancies (Wilson et al, 2012; Norenberg et al, 2015; Mansouri et al, 2015), and can impact the anti-tumor activity of selective BCR pathway inhibition (Davis et al, 2010; Wilson et al, 2012) in part via induction of autocrine cytokine stimulation leading to JAK/STAT-dependent up-regulation of MCL1 (Lam et al, 2008). We previously reported that cerdulatinib, a small molecule kinase inhibitor that dually targets SYK and the JAK family members JAK1, JAK3, and TYK2, maintained anti-tumor activity in DLBCL cell lines bearing mutations to CARD11, MYD88, and A20 (Ma et al, 2015). The majority of DLBCL cell lines exhibit various degrees of reliance on SYK and JAK signaling for survival, however in a screen of 15 DLBCL cell lines we found 3 that were completely resistant to cerdulatinib and are described here. In one of the cerdulatinib-resistant cell lines, RCK8, next generation sequencing revealed bi-allelic inactivation of the IκBα gene. One allele carries a frameshift mutation in exon 1 resulting in the generation of a premature stop codon, and the second allele is a nonsense mutation in exon 3 at Gln154, also leading to a stop codon. In accord with a previous report (Kalaitzidis et al, 2002), the cell line lacks IκBα protein expression. We therefore proceeded to explore the possibility that loss of IκBα was responsible for resistance to cerdulatinib. Consistent with the loss of IκBα, the RCK8 cell line exhibited enhanced basal NFκB activity. Genetic re-introduction of wild type IκBα led to rapid suppression of NFκB, and ultimately cell cycle arrest and cell death, indicating that the cell line was dependent upon loss of this gene for survival. Associated with suppression of NFκB was decreased phosphorylation of cellular pAKT S473 and pERK Y202, but not of pSTAT3 Y705. We then attempted to knock down IκBα in cerdulatinib-sensitive cell lines using siRNA to determine if resistance to SYK/JAK inhibition could be generated. None of the DLBCL cell lines tested (n=4) could tolerate IκBα gene knock down, suggesting an additional mutation in RCK8 enables survival under conditions of homozygous loss of IκBα. Ligation of CD40 leads to a transient down-regulation of IκBα at the protein level (Oeckinghaus and Ghosh, 2009). We therefore examined the effect of CD40L on multiple DLBCL cell lines and found that IκBα was maximally suppressed within 30-60 minutes post CD40 stimulation, returning to pre-treatment levels by 2-4 hours. In contrast, the impact on NFκB activation was much longer, and 5 of 7 cerdulatinib-sensitive cell lines tested were made resistant by incubation with CD40L. Associated with this resistance was not only induction of NFκB, but also pERK Y204, pAKT S473, and pSTAT3 Y705. Interestingly, whereas the CD40L-induced NFκB activation was not inhibited by cerdulatinib, the other signaling events were, despite the generation of resistance. Loss of IkB family members has been described in the context of Hodgkin's lymphoma, non-Hodgkin's lymphoma, and chronic lymphocytic leukemia (Cabannes et al, 1999; Norenberg et al, 2015; Mansouri et al, 2015). Here we demonstrate that loss of IκBα in multiple DLBCL cell lines generates resistance to cerdulatinib. We will be exploring the clinical relevance of these in vitro observations in cell lines as part of an ongoing phase II trial of cerdulatinib in patients with relapsed/refractory B cell malignancies. Disclosures Coffey: Portola Pharmaceuticals: Employment, Equity Ownership, Patents & Royalties, Research Funding. Feng:Portola Pharmaceuticals: Employment, Equity Ownership, Research Funding. Wang:Portola Pharmaceuticals: Honoraria, Research Funding. Michelson:Portola Pharmaceuticals: Employment, Equity Ownership, Patents & Royalties, Research Funding. Pandey:Portola Pharmaceuticals: Employment, Equity Ownership, Patents & Royalties, Research Funding. Curnutte:3-V Biosciences: Equity Ownership; Portola Pharmaceuticals: Employment, Equity Ownership, Patents & Royalties, Research Funding; Sea Lane Biotechnologies: Consultancy. Conley:Portola Pharmaceuticals: Employment, Equity Ownership, Patents & Royalties, Research Funding.

Background. Subsets of B cell lymphomas appear to rely on B-cell receptor (BCR) and/or cytokine JAK/STAT signaling for survival. SYK is upstream of BTK, PI3Kδ, and PLCγ2 on the BCR signaling pathway, and thus a potential therapeutic target. Additional survival support appears to be mediated by cytokine-induced JAK/STAT pathways. Cerdulatinib is a dual SYK/JAK inhibitor being evaluated in patients with relapsed/refractory B cell malignancies in a dose escalation study. Patient PK and PD parameters indicated nonlinearity at doses above 30 mg QD. Exposure at the 45 mg dose was 3-fold higher than at 30 mg QD. As the dose was further increased up to 100 mg QD, the Cssmax and AUC values plateaued. PD results also appeared to plateau achieving approximately 50-90% target inhibition in peripheral blood assays at steady-state Cmin to Cmax, respectively. The target therapeutic exposure for oncology, based on pre-clinical models, is a Cssmin >1.5uM which would lead to >90% SYK/JAK inhibition at the trough concentration Objective. Pre-clinical and clinical PK/PD relationships and correlations between SYK/JAK inhibition and tumor response will be presented. A physiological-based PK (PBPK) model was developed to elucidate the relationship between dose, dosing schedule, and exposure. The goal of developing a PBPK model was to provide a strategy to increase exposure in patients to therapeutic target levels. Methods. This is a 3+3 dose escalation study with 28-day cycles and doses studied from 15 mg to 100 mg QD, and up to 45 mg BID. PK, PD, and safety were monitored. SYK and JAK inhibition was determined by multiple whole blood assays measuring signaling via the B cell antigen receptor, IL2, IL4, IL6, and GM-CSF. Serum markers of tumor burden - CCL3, CCL4, and other markers of inflammation, were also measured. Physiochemical parameters and in vitro ADME parameters were used to construct a PBPK model. Results. Exposure correlated well with PD and tumor responses in the dose escalation study. Low pH dependent solubility was identified as the rate-limiting factor in increasing plasma concentrations. The PBPK model predicted BID dosing would result in significantly higher plasma levels. The Cssmin concentration of QD doses from 40 to 100 mg QD was ∼0.70 uM while for the 45 mg BID dose for the first 3 patients the Cssmin was ∼1.5 uM. Complete target inhibition at this Cssmin was achieved with good tolerability. Conclusions. The preliminary PBPK model identified the pH dependent low solubility of cerdulabinib as the rate-limiting factor of absorption with increasing doses. Subsequent evaluation of 45 mg BID doses in patients provided higher Cmin, Cmax, and AUC values for all patients treated at this dose level and PD markers indicated complete inhibition of both pathways. We are now enrolling additional patients at this dose, in preparation for selecting our final phase II dose. Citation Format: Janet M. Leeds, Greg Coffey, Anjali Pandey, Pam B. Conley, Karen Rowland Yeo, Alice B. Ke, John T. Curnutte, Glenn Michelson. Preclinical and clinical studies and modeling and simulation to identify phase II dose for cerdulatinib: a dual SYK/JAK inhibitor for the treatment of B-cell malignancies. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr CT144.

Background: Preclinical data and early clinical studies demonstrate a reliance on B cell antigen receptor (BCR) signaling and/or cytokine-induced JAK/STAT signaling for survival of subsets of B cell malignancies. Increased serum concentrations of several cytokines are observed in CLL and NHL and predict a more aggressive disease progression (Yan, X. J., et al, 2011; Mahadevan, D., et al, 2009; el Far. M., et al, 2004; Lai, R., et al, 2002; Fayed, L., et al, 2001). The source of these cytokines may be derived from the tumor itself in an autocrine stimulation fashion, or from non-tumor leukocytes which have mounted an ineffective immune response within the tumor microenvironment. Experimentally, IL4 has been shown to promote the survival of CLL B cells in culture and protect them from death by treatment with fludarabine and chlorambucil (Steele, A.J., et al, 2010). The mechanism underlying this survival support appears to be cytokine-induced up-regulation of BCL2 family members (Castejon, R., et al, 1999; Jewell, A.P., et al, 1994; Panayiotidis, P., et al, 1993; Dancescu, M., et al, 1992). Combined SYK/JAK inhibition may therefore represent a powerful strategy to treat B cell malignancies. Cerdulatinib is a reversible ATP competitive inhibitor of SYK, JAK1, JAK3, and TYK2 that is currently in clinical development for the treatment of relapsed/refractory B cell lymphoma and leukemia. We review here cerdulatinib preclinical and clinical pharmacodynamic/pharmacokinetic relationships to tumor response in treated patients. Methods: Inhibition of SYK- and JAK-dependent and independent signaling was determined by intracellular phospho-flow following stimulation of human whole blood with various agonists against BCR and cytokine receptors. Anti-tumor activities of cerdulatinib and other selective inhibitors of BCR and JAK/STAT pathways were evaluated in fourteen DLBCL cell lines by CellTiter Glo, caspase 3 induction, and cell cycle arrest. In vivo anti-inflammatory activity of cerdulatinib was determined using the rat collagen induced arthritis model. The effective concentrations pre-clinically were compared to cerdulatinib-induced SYK and JAK inhibition, anti-inflammatory activity, and anti-tumor activity following oral dosing in relapsed/refractory CLL and NHL patients. Results: Cerdulatinib demonstrated broad anti-tumor activity in DLBCL cell lines, relative to other targeted agents. In a panel of 14 cell lines representing both ABC and GCB subtypes, 9 underwent apoptosis and an additional 2 underwent cell cycle arrest. Cooperative effects of SYK and JAK inhibition were observed in 4 of the cell lines, whereas 3 cell lines were sensitive to SYK but not JAK inhibition, and 1 cell line was sensitive to JAK but not SYK inhibition. Three of the 14 cell lines were resistant to cerdulatinib. Apoptosis was induced in the majority of DLBCL cell lines at 2 µM (achieved at clinical doses ≥40 mg). In healthy whole blood ex vivo spiking experiments, cerdulatinib selectively inhibited BCR/SYK and cytokine (IL2, IL4, IL6) JAK/STAT signaling with IC50's ranging from 0.2-0.9 µM (achieved at clinical doses of 15 mg-40 mg). Inflammation and joint destruction in the rat collagen-induced arthritis model was arrested at 0.3 µM average plasma concentration (achieved at clinical doses ≥30 mg). In cancer patients receiving cerdulatinib once daily, plasma concentrations above 2 µM have been safely achieved, while maintaining steady-state Cmin of ~1 µM. Following oral dosing in patients, SYK and JAK pathways were inhibited with similar potency as was observed in healthy volunteer ex vivo spiking experiments with >90% inhibition of SYK and JAK safely achieved for multiple cycles of therapy. Tumor response as measured by CT scan strongly correlated with percent inhibition of SYK and JAK signaling in patient-derived whole blood, and percent inhibition of serum markers of inflammation (e.g., β2M, CRP, IL10, VCAM1, sTNFR, CCL3). Conclusion: Once daily oral dosing of cerdulatinib at 40-65 mg achieves steady-state plasma concentrations in the 1-2µM range (trough to peak), which is sufficient to block SYK/JAK signaling, inflammatory mechanisms, and affect tumor viability both in DLBCL cell lines and in patients. We conclude that these exposure levels are sufficient to begin testing the clinical potential of cerdulatinib. We will begin enrolling phase Ib/IIa expansion cohorts this year. Disclosures Coffey: Portola Pharmaceuticals Inc: Employment, Equity Ownership, Research Funding. Feng:Portola Pharmaceuticals: Employment, Equity Ownership, Research Funding. Michelson:Portola Pharmaceuticals Inc: Employment, Equity Ownership, Research Funding. Leads:Portola Pharmaceuticals: Employment, Equity Ownership, Research Funding. Curnutte:Portola Pharmaceuticals, Inc.: Employment; 3-V Biosciences: Equity Ownership; Sea Lane Biotechnologies: Consultancy. Pandey:Portola Pharmaceuticals Inc: Employment. Conley:Portola Pharmaceuticals, Inc.: Employment.

Background: Background: Subsets of B cell lymphomas demonstrate a reliance on B-cell receptor (BCR) and/or cytokine JAK/STAT signaling for survival. SYK is positioned upstream of BTK, PI3Kδ, and PLCγ2 on the BCR signaling pathway, making it a potential therapeutic target. Additional survival support appears to be mediated by cytokine-induced JAK/STAT pathways, which can be activated by tumor autocrine signaling loops or by pro-inflammatory cytokines originating from non-malignant infiltrating leukocytes present in the tumor microenvironment. Pre-clinical models demonstrate broad anti-tumor activity with combined SYK and JAK inhibition relative to selective inhibition of these targets alone. Methods: This is a 3+3 dose escalation study with 28-day cycles and doses studied ranging from 15mg to 65mg once daily. PK, PD, and safety were monitored. Clinial response was assessed by standard criteria. The level of inhibition of SYK and JAK was determined by multiple whole blood assays measuring signaling via BCR and receptors for the B-cell antigen, IL2, IL4, IL6, and GM-CSF. Serum markers of tumor burden - CCL3, CCL4, and other markers of inflammation, were also measured. Results: A total of 36 patients (pt) with CLL/SLL or B cell NHL were dosed. Median age was 67 years (range 23-85) and median prior therapies (tx) was 3 (range 1-8). Treatment emergent AEs of ≥ grade 3 observed deemed related to study drug were: neutropenia (n=2), anemia (n=1), and pneumocystis pneumonia (grade 5, n=1) at 30mg; anemia, AST increase, hypotension, thrombocytopenia (n=1 for each), and fatigue (n=2) at 45mg; anemia, neutropenia, abdominal pain, pneumonia, and fatigue (n=1 for each) at 50mg, and diarrhea and fatigue (n=1 for each) at 65mg. The patient with grade 3 AST had tumor progression to the liver. No dose-limiting toxicities (DLT) have been reported to date and cerdulatinib is generally well tolerated. Saturating inhibition of SYK and JAK in circulating lymphocytes (>80% inhibition) and serum inflammation markers (e.g., β2M,CRP, CCL4; 50-90% inhibition) occurs at plasma concentrations achieved at Cmin of the 40mg dose ( 0.6-1µM) at steady state. At the 65mg dose, these parameters were 80-90% inhibited on day 1 of cycle 1 indicating a more immediate effect compared to lower doses. At the 65mg dose, steady state Cmin and Cmax concentrations are approximately 1 and 2µM, respectively, sufficient to induce apoptosis in the majority of B cell lymphoma cell lines tested. PK is suitable for once daily dosing with a half-life of 12-16 hours and a 2:1 peak-trough ratio. Partial responses (n=4) were observed at 30mg in a pt with del 17p CLL who had relapsed after 6 prior tx; at 45mg a pt with CLL who had received 4 prior tx, and another pt with FL who had received 3 prior tx; and at 65mg in a pt with a transformed DLBCL (MYC, BCL2, and BCL6 expression by IHC) who had relapsed approximately 1 year after 1 prior tx. Responses occurred after 2 cycles of tx. Seven total patients have remained on cerdulatinib for over 200 days, including 2 who have been on for a year or more. Conclusions: Cerdulatinib continues to demonstrate a favorable PK profile and good tolerability at high levels of SYK and JAK inhibition. The clinical responses seen to date support further development and dose escalation continues to identify the MTD. Phase II expansion cohorts are open or planned for CLL, FL, aggressive NHL (DLBCL), and a combination with rituximab. Disclosures Michelson: Portola Pharmaceuticals Inc: Employment, Equity Ownership, Research Funding. Pandey:Portola Pharmaceuticals Inc: Employment. Birrell:Portola Pharmaceuticals Inc: Employment. Coffey:Portola Pharmaceuticals Inc: Employment, Equity Ownership, Research Funding. Leeds:Portola Pharmaceuticals Inc: Employment. Curnutte:Portola Pharmaceuticals Inc: Employment.

Background: Measurement of serum prostate-specific antigen (PSA) and digital rectal examination (DRE) are commonly used for prostate cancer screening. Clinicians have been advised to avoid measuring serum PSA after DRE because of the possibility of spurious elevation. However, studies in healthy volunteers have found no change. We sought to determine whether DRE performed by internists affects PSA levels in a primary care clinic population. Methods: Men older than 49 years enrolled in a Veterans Affairs internal medicine clinic were eligible for the study. For all patients, prostate size and nodularity were assessed by DRE. Blood for determination of PSA levels was drawn immediately before DRE and 30 minutes after DRE. All patients completed a questionnaire regarding voiding. Results: Two hundred two men aged 50 to 85 years (mean, 67 years) were enrolled and had complete data. The mean PSA level increased by 0.26 μg/L after DRE (P Conclusions: We conclude, in an elderly veteran population, that DRE causes a statistically significant but clinically insignificant increase in serum PSA level. Additionally, we found that symptoms and physical examination results cannot be used to select a population for whom PSA screening would likely be useful. (Arch Intern Med. 1995;155:389-392)