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Introduction : Glofitamab (RG6026) is a novel T-cell-engaging, bispecific, full-length antibody with a 2:1 molecular configuration that facilitates bivalent binding to CD20 on B-cells, and monovalent binding to CD3 on T-cells. Preclinically, glofitamab had superior potency compared with other tested bispecifics with 1:1 formats (Bacac, et al. Clin Cancer Res 2018). NP30179 (NCT03075696) is an ongoing multicenter, Phase I/Ib, dose-escalation and dose-expansion trial evaluating the safety, tolerability, pharmacokinetics, biomarker responses, and efficacy of glofitamab in patients (pts) with relapsed or refractory (R/R) non-Hodgkin lymphoma (NHL). Clinical data from NP30179 demonstrated that fixed dosing of glofitamab (0.6-25mg) induced high and durable complete responses with a manageable safety profile in pts with heavily pre-treated R/R NHL (Dickinson, et al. EHA 2020). Obinutuzumab pretreatment (Gpt) was shown to be effective in mitigating the risk of cytokine release syndrome (CRS), allowing for rapid escalation of glofitamab to clinically active doses (Dickinson, et al. EHA 2020). Step-up dosing of glofitamab was used in addition to Gpt to further reduce the risk of CRS. For the first time, we present clinical data of glofitamab step-up dosing with Gpt in pts with R/R NHL. Methods: Pts received 1000mg obinutuzumab 7 days prior to first glofitamab administration. Glofitamab was given intravenously with step-up dosing on Cycle (C) 1 Day (D) 1 and 8 and then at the target dose from C2D1, every 3 weeks for up to 12 cycles (2.5/10/16mg or 2.5/10/30mg). Response rates reported are based on the Lugano criteria (Cheson, et al. J Clin Oncol 2014). Results: As of April 17, 2020, 38 pts received step-up doses of glofitamab; 17 pts received 2.5/10/16mg, and 21 pts received 2.5/10/30mg. Twenty-eight pts (73.7%) had aggressive NHL (aNHL) histologies and ten pts had indolent NHL (iNHL; Table). The median age was 68 years (range 52-85) and median number of prior lines of therapy was 3 (range 1-12). Twenty-seven (71.1%) pts were refractory to their last therapy, and 28 (73.7%) pts were refractory to prior CD20 therapy. After a median follow-up of 2.8 months, across all efficacy-evaluable pts (n=32) the overall response rate (ORR) and complete metabolic response (CMR) rate was 62.5% and 40.6%, respectively. For pts with aNHL (n=24), the ORR was 50.0% with CMR rates of 29.2%. As of the data cut-off date, 17 pts with aNHL (70.8%) had reached the first response assessment only (C3) and remain on treatment; four pts (16.7%) had reached the second response assessment (C6). For pts with iNHL (n=8), the ORR was 100.0% with 75.0% of pts achieving CMR. Across the safety-evaluable population (n=38), the most common AEs were CRS (57.9%), pyrexia (31.6%), neutropenia, thrombocytopenia and hypophosphatemia (28.9% each). No AEs led to treatment discontinuation. Of 22 patients who experienced CRS events, the CRS events only occurred in C1 and C2; 15 had CRS after the 2.5mg dose, 12 after the 10mg dose, and 5 during C2 (16 or 30mg dose; Figure). Eight pts (21.1%) and 13 pts (34.2%) experienced Grade (Gr) 1 and 2 CRS, respectively; none experienced Gr 3 CRS. One pt (2.6%) experienced Gr 4 CRS after the 30mg dose. No CRS events occurred after C2. Tocilizumab was used to manage CRS in six (15.8%) pts: n=2 for 2.5/10/16mg and n=4 for 2.5/10/30mg cohorts. CRS events were manageable and resolved for 21 pts (95.4%) at data cut-off. No Gr ≥3 neurologic adverse events were reported. Consistent with prior biomarker data from fixed-dose regimens (Bröske, et al. EHA 2020), glofitamab administered with step-up dosing induced a transient T-cell redistribution. Conclusions: Step-up dosing of glofitamab allowed escalation up to 30mg to maximize efficacy, while minimizing the risk of increased CRS. High ORR and CMR rates were observed in pts with NHL who had failed several lines of treatment. Toxicity was manageable with the main safety signal being low-grade CRS observed in early cycles. Updated results will be presented at the congress which will include data from at least 50 pts receiving glofitamab step-up dosing with Gpt. Disclosures Hutchings: Genmab, F. Hoffmann-La Roche, Takeda: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene, Genmab, Janssen, Novartis, F. Hoffmann-La Roche, Takeda: Research Funding. Carlo-Stella:Servier, Novartis, Genenta Science srl, ADC Therapeutics, F. Hoffmann-La Roche, Karyopharm, Jazz Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; ADC Therapeutics and Rhizen Pharmaceuticals: Research Funding; Bristol-Myers Squibb, Merck Sharp & Dohme, Janssen Oncology, AstraZeneca: Honoraria; Boehringer Ingelheim and Sanofi: Consultancy. Bachy:Roche, Gilead: Consultancy; Amgen: Research Funding; Roche, Celgene, Amgen, Janssen, Gilead, Novartis, Sanofi: Honoraria; Beigene: Membership on an entity's Board of Directors or advisory committees. Morschhauser:F. Hoffmann-La Roche: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Epizyme: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; Gilead: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Abbvie: Membership on an entity's Board of Directors or advisory committees; Janssen: Honoraria; Servier: Consultancy; Genentech, Inc.: Consultancy. Crump:Kite/Gilead: Consultancy; Roche: Consultancy; Servier: Consultancy. Iacoboni:Novartis, Gilead, Celgene, Roche: Honoraria. Sureda Balari:BMS: Speakers Bureau; Roche: Honoraria; Janssen: Consultancy, Honoraria; Takeda: Consultancy, Honoraria, Speakers Bureau; Incyte: Consultancy; Gilead/Kite: Consultancy, Honoraria; Novartis: Consultancy, Honoraria; Sanofi: Consultancy, Honoraria; Merck Sharpe and Dohme: Consultancy, Honoraria, Speakers Bureau; Celgene: Consultancy, Honoraria; Celgene/Bristol-Myers Squibb: Consultancy, Honoraria. Martinez-Lopez:Novartis: Consultancy; Janssen: Consultancy, Honoraria; BMS: Consultancy, Research Funding; Incyte: Consultancy, Research Funding; Janssen-cilag: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees. Lundberg:F. Hoffmann-La Roche: Current Employment, Current equity holder in publicly-traded company. Dixon:Roche Products Limited: Current Employment; F. Hoffmann-La Roche: Current equity holder in publicly-traded company, Divested equity in a private or publicly-traded company in the past 24 months. Perez Callejo:F. Hoffmann-La Roche: Current Employment, Current equity holder in publicly-traded company. Relf:Roche Products Ltd: Current Employment. Carlile:AstraZeneca: Current equity holder in publicly-traded company, Ended employment in the past 24 months; F. Hoffmann-La Roche: Current Employment, Current equity holder in publicly-traded company. Piccione:Genentech, Inc.: Current Employment; F. Hoffmann-La Roche: Current equity holder in publicly-traded company. Humphrey:F. Hoffmann-La Roche: Current Employment, Current equity holder in private company, Current equity holder in publicly-traded company. Dickinson:Novartis: Consultancy, Honoraria, Research Funding, Speakers Bureau; Janssen: Consultancy, Honoraria, Speakers Bureau; Roche: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Gilead: Consultancy, Honoraria, Research Funding, Speakers Bureau; Merck Sharp & Dohme: Consultancy. OffLabel Disclosure: Glofitamab (RG6026; CD20-TCB) is a full-length, fully humanized immunoglobulin G1 (IgG1) bispecific antibody with a 2:1 molecular format that facilitates bivalent binding to CD20 on B-cells, and monovalent binding to CD3 on T-cells. Glofitamab redirects T cells to engage and eliminate malignant B cells. Glofitamab is an investigational agent.

Glofitamab is a novel CD20-targeted bispecific T cell-engaging antibody that has demonstrated significant clinical efficacy in aggressive forms of Non-Hodgkin Lymphoma (aNHL). Despite significant clinical efficacy in aNHL (Hutchings et al. JCO 2021), some patients only achieve a partial response or progress upon treatment. To investigate the cellular and molecular factors that correlate with clinical activity of glofitamab, we applied CyTOF, single cell RNA and TCR sequencing to study PBMCs collected at baseline and at cycle 2 of treatment from patients with aNHL. Our cohort included 9 patients with complete response (CR) and 9 patients with progressive disease (PD) status (response assessed at cycle 3) recruited during dose escalation of glofitamab in a Ph1 clinical trial (NP30179). We identified a higher proportion of CD4 T cells and a lower proportion of monocytes in CR versus PD patients. Complementary to changes in cell proportions, we explored the covariation of genes across single cells to isolate co-regulated processes and identified several gene expression programs associated with the response status, of which some were shared between two or more cell types while others were cell type-specific. Focusing on the T cell compartment, we further identified subtypes of CD8 and CD4 T cells enriched in either CR or PD patients, and used topic modeling, a computational approach that excels in settings of continuous phenotypes, to contrast the transcriptional state of T cells in CR patients compared to PD patients at baseline and on treatment. Interestingly, we found CR patients to exhibit a less exhausted CD8 T cell population at baseline, confirming our previous observations using tumor bulk RNA sequencing data. Moreover, we observed that hyper-expanded clonotypes were generally enriched in the CD8 T cell compartment, and that the clonal cells had a stronger cytotoxic phenotype compared to non-clonal T cells. This observation was further corroborated when looking at TCR diversity. Indeed, we observed that distinct T cell populations exhibited differences in TCR diversity, with exhausted CD8 T cells showing decreased clonal diversity. Finally, to better understand the changes in CD8 T cells, we performed trajectory inference and observed that the position of individual cells along the pseudotime varied largely according to timepoint and response status. This analysis further allowed us to identify the expression dynamic of numerous markers of T cell exhaustion, as well as transcription factors associated with progenitor and self-renewing state. Notwithstanding the limited sample size and patient heterogeneity, our analysis provides a deep characterization of the cellular and molecular features associated with response to glofitamab using peripheral biomarkers. As glofitamab is being evaluated in a number of clinical trials either as a single agent or in combination, our dataset and findings can help broaden the understanding of its mode of action, and might be relevant for patient enrichment and monitoring response. Citation Format: Sina Nassiri, Lucas Habegger, Petra Gerber, Vinko Tosevski, Tamara Hüsser, Emilio Yanguez, Sylvia Herter, Martin Weisser, Koorosh Korfi, Pablo Umana, Emily Piccione, Ann-Marie Bröske, Marina Bacac. Single cell profiling of PBMCs reveals correlates of clinical response to glofitamab [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr LB558.

COVID-19 is a global pandemic that has resulted in over 800,000 deaths. Robust humoral anti-viral immune responses have the potential to generate a diverse set of neutralizing antibodies to eliminate viruses and protect against re-infection, transmission, and the evolution of mutations that escape targeted therapeutics. CD73 is present on the majority of human B cells and a subset of T cells where it plays a role in lymphocyte activation and migration. CD73 also functions as an ectoenzyme that converts AMP into adenosine, which can be immunosuppressive. Here we report on CPI-006, a humanized FcγR binding-deficient IgG1 anti-CD73 antibody that blocks CD73 enzymatic activity and directly activates CD73POS B cells, inducing differentiation into plasmablasts, immunoglobulin class switching, and antibody secretion independent of adenosine. Immunophenotypic analysis of peripheral blood from advanced cancer patients receiving CPI-006 revealed evidence of B cell activation, clonal expansion, and development of memory B cells. These immune effects suggested that CPI-006 may be effective at enhancing the magnitude, diversity, and duration of humoral and cellular responses to viruses such as SARS-CoV-2. We have therefore initiated a Phase 1, single-dose, dose-escalation trial in hospitalized patients with mild to moderate COVID-19. The objectives of this trial are to evaluate the safety of CPI-006 in COVID-19 patients and to determine effects of CPI-006 on anti-SARS-CoV-2 antibody responses and the development of memory B cell and T cells. Ten patients have been enrolled in the trial receiving doses of 0.3 mg/kg or 1.0 mg/kg. All evaluable patients had low pre-treatment serum levels of anti-viral antibodies to the SARS-CoV-2 trimeric spike protein and its receptor binding domain, independent of the duration of their COVID-19 related symptoms prior to enrollment. Anti-viral antibody responses were induced 7 days after CPI-006 treatment and titers continued to rise past Day 56. Increases in the frequency of memory B cells and effector/memory T cells were observed 28 days after treatment. These preliminary results suggest that CPI-006 activates B cells and may enhance and prolong anti-SARS-CoV-2 antibody responses in patients with COVID-19. This approach may be useful for treating COVID-19 or as an adjuvant to enhance the efficacy of vaccines.

Purpose Feeding challenges in children are common, at times reaching a severity that requires the placement and long-term use of enteral feedings. A significant barrier to advancing the oral eating of some tube-dependent children is the presence of oral aversion. Although some research exists regarding the treatment of tube-dependent children who are averse to food or the process of eating, specifically, there has yet to be an examination of children who are truly “orally” averse—resisting not just the presentation of food or liquid but also nonnutritive stimuli presented extra- or intra-orally. Method Using a retrospective chart review, the current study aimed to examine the treatment outcomes of 18 feeding tube-dependent children with significant oral aversion (nine boys, nine girls; M age = 46.7 months, SD = 20.0 months, range: 11.4–89.3 months) as compared to 29 tube-dependent, but nonorally averse, clinical controls. Children completed approximately 6–8 weeks of intensive interdisciplinary feeding treatment. Results Analyses revealed significant improvements in all measured treatment outcomes for both patient groups, including children's rates of acceptance and maladaptive mealtime behavior. Significant reductions in tube use were also observed across both groups, with tube utilization decreasing, on average, by 76.2% for orally averse and by 64.3% for nonorally averse children by program discharge. Conclusion Results demonstrate the therapeutic benefits of intensive interdisciplinary intervention for both groups of tube-dependent children, highlighting that orally averse children, believed to be an especially challenging subset of pediatric feeding patients, demonstrate similarly positive treatment responses. Interestingly, in this preliminary examination, orally averse children demonstrated significantly greater reductions in tube utilization following discharge when compared with their nonorally averse clinical peers.

Adenosine signaling through A2A receptors (A2AR) expressed on immune cells suppresses antitumor immunity. CPI-444 is a potent, selective, oral A2AR antagonist. Blockade of A2AR with CPI-444 restored T-cell signaling, IL2, and IFNγ production that were suppressed by adenosine analogues in vitro. CPI-444 treatment led to dose-dependent inhibition of tumor growth in multiple syngeneic mouse tumor models. Concentrations of extracellular adenosine in the tumor microenvironment, measured using microdialysis, were approximately 100–150 nmol/L and were higher than corresponding subcutaneous tissue. Combining CPI-444 with anti–PD-L1 or anti–CTLA-4 treatment eliminated tumors in up to 90% of treated mice, including restoration of immune responses in models that incompletely responded to anti–PD-L1 or anti–CTLA-4 monotherapy. Tumor growth was fully inhibited when mice with cleared tumors were later rechallenged, indicating that CPI-444 induced systemic antitumor immune memory. CD8+ T-cell depletion abrogated the efficacy of CPI-444 with and without anti–PD-L1 treatment, demonstrating a role for CD8+ T cells in mediating primary and secondary immune responses. The antitumor efficacy of CPI-444 with and without anti–PD-L1 was associated with increased T-cell activation, a compensatory increase in CD73 expression, and induction of a Th1 gene expression signature consistent with immune activation. These results suggest a broad role for adenosine-mediated immunosuppression in tumors and justify the further evaluation of CPI-444 as a therapeutic agent in patients with solid tumors. Cancer Immunol Res; 6(10); 1136–49. ©2018 AACR.

Background: Cytokine release syndrome (CRS) is a potentially life-threatening toxicity caused by immune activation. CRS can be triggered non-specifically by T-cell engaging therapies. Risk factors for CRS are expected to be disease-specific and prediction of an individual patient's CRS risk is not currently possible. Glofitamab is a T-cell engaging bispecific antibody targeting CD20 and CD3 with a novel 2:1 format that has shown promising efficacy with a manageable safety profile in NP30179 (NCT03075696), an ongoing Phase I/II dose finding study evaluating glofitamab in patients with relapsed or refractory non-Hodgkin lymphoma (NHL). While CRS is observed with glofitamab, cases typically occur with grade 1/2 severity (per ASTCT, Lee et al 2019) with most occurrences confined to the first cycle of therapy. Data from NP30179 were used to develop a model to predict the occurrence of Grade ≥ 2 CRS after the first glofitamab dose to enable stratification of patients according to risk of CRS with possible future implications for intensity of monitoring for those at low risk. Methods: Glofitamab was administered intravenously over 4 to 8 hours as a fixed or step-up dosing regimen, as previously described (Hutchings, et al JCO 2021). Non-overlapping training and validation data sets were defined; the training data set included patients with aggressive (n=165) or indolent NHL (n=31) who received a first dose of 0.6-25 mg, and the model validation data set (n=51; 35 aggressive NHL) included patients who received a 2.5mg first dose. The primary outcome was defined as Grade ≥2 CRS in the week after the first glofitamab dose, and included 65 events (n=58 training, n=7 validation). In the training data set we evaluated the association between the dose, putative risk factors (including demographics, medical history, disease characteristic variables, baseline laboratory values) and the occurrence of CRS. Univariate and multivariate models were applied in a stratified cross-validation setting to assess the most predictive and stable combination of risk factors. Baseline and on-treatment cytokine levels were analyzed via ELISA in a subset of patients (n=89). Results: The temporal pattern of CRS occurrences revealed that the vast majority of first CRS events occur after the first dose of glofitamab. To predict the occurrence of Grade ≥ 2 CRS after the first glofitamab dose, a multivariate model was developed to include glofitamab first dose and a combined risk score, termed the "CRS risk score" (CRSRS), which is the weighted sum of binarized risk factor values at baseline (Figure). The predictive ability was tested in the validation data set in which the incidence of Grade ≥ 2 CRS was 14% (7/51). A low risk group (CRSRS Induction of cytokines, including IL-6 and TNFα, was observed upon treatment with glofitamab and peak magnitude of cytokine induction was associated with CRS incidence and severity. Cytokine induction was evident by end of glofitamab infusion and peak levels of TNFα were observed by mid-infusion. CRSRS and TNFα induction were evaluated together for the subset of patients with cytokine data available to determine whether risk classification incorporating both metrics could refine the risk stratification of patients. Early TNFα changes were layered on top of CRSRS (at the cutoff of 5.0) such that patients with less than 1.5-fold induction were classified as low risk, and patients with more than 8-fold induction were classified as high risk. In the training data set, this decision tree approach improved the performance of prediction compared to CRSRS alone. Conclusions: A model based on 8 baseline factors allowed an accurate classification of risk for Grade ≥2 CRS upon treatment with glofitamab. Addition of TNFα induction may improve the predictive value. The predictive performance was confirmed in a separate validation data set with additional analyses in independent cohorts ongoing. The CRSRS, alone or in combination with cytokine induction, represents a tool to predict the occurrence of Grade ≥2 CRS after the first glofitamab dose to enable stratification of patients according to risk of CRS with possible future implications for the intensity of monitoring for those at low risk. K.V.K. and A.B. have contributed equally. Disclosures Belousov: F. Hoffmann-La Roche Ltd: Current Employment. Byrtek: Genentech, Inc.: Current Employment; F. Hoffmann-La Roche Ltd: Current holder of individual stocks in a privately-held company, Current holder of stock options in a privately-held company. Kwan: Genentech, Inc.: Current Employment, Current equity holder in publicly-traded company. Perez-Callejo: F. Hoffmann-La Roche Ltd: Current Employment, Current equity holder in publicly-traded company. Li: Genentech, Inc.: Current Employment, Current holder of individual stocks in a privately-held company. Carlile: AstraZeneca: Current equity holder in publicly-traded company, Ended employment in the past 24 months; F. Hoffmann-La Roche Ltd: Current Employment, Current equity holder in publicly-traded company. McCall: Genentech, Inc.: Current Employment; F. Hoffmann-La Roche Ltd: Current equity holder in publicly-traded company, Current holder of individual stocks in a privately-held company, Current holder of stock options in a privately-held company. Nielsen: F. Hoffmann-La Roche Ltd: Current Employment, Current equity holder in publicly-traded company. Piccione: Genentech, Inc.: Current Employment; F. Hoffmann-La Roche Ltd: Current equity holder in publicly-traded company. OffLabel Disclosure: Glofitamab is a full-length, humanized, immunoglobulin G1 bispecific antibody with a 2:1 molecular format that facilitates bivalent binding to CD20 on B-cells, and monovalent binding to CD3 on T-cells. Glofitamab redirects T cells to engage and eliminate malignant B cells. Glofitamab is an investigational agent.

Context Glofitamab, a T-cell-engaging, bispecific, full-length antibody, allows bivalent binding to CD20 (B-cells) and monovalent binding to CD3 (T-cells). In NP30179 (NCT03075696), an ongoing multicenter, phase I, dose-escalation and expansion study, glofitamab SUD, in addition to Gpt, allowed dose escalation ≤30 mg to maximize efficacy while mitigating cytokine release syndrome (CRS) (Hutchings et al. J Clin Oncol 2021). Objective To present updated efficacy data from glofitamab monotherapy SUD cohorts. Methods Gpt (1000 mg) was given 7 days pre-glofitamab initial dose. Intravenous glofitamab SUD was given on day (D) 1 and 8 of cycle (C) 1, then at target dose from C2D1 (2.5/10/16 mg or 2.5/10/30 mg); treatment continued for ≤12 cycles, every 21 days. Response rates were based on the Lugano criteria (Cheson et al. J Clin Oncol 2014). Results As of December 1, 2020, 52 pts received glofitamab SUD; 17 and 35 pts received 2.5/10/16 mg and 2.5/10/30 mg, respectively. Twenty-eight pts (53.8%) had aggressive NHL (aNHL) and 24 pts had indolent NHL (iNHL). Median age: 68 (44–85) years; median 3 (1–12) prior lines of therapy; 40 (76.9%) and 38 (73.1%) pts were refractory to their most recent and any prior CD20 therapy, respectively. Median follow-up duration: 6.3 months. Best overall response (OR) and complete metabolic response (CMR) rates for aNHL cohort: 64.3% and 57.1%, respectively. 4/5 pts (80%) with mantle cell lymphoma (2.5/10/16 mg, n=2; 2.5/10/30 mg, n=2) had CMR. For aNHL, 13/16 CMRs are ongoing, with 8 CMRs lasting >3 months. OR and CMR rates for pts with iNHL: 79.2% and 70.8%, respectively, with 14/17 CMRs ongoing and 10 CMRs lasting >3 months. As of August 3, 2020, common adverse events were CRS (63.5%), neutropenia (38.5%), and pyrexia (32.7%), with CRS mostly confined to C1. Grade (Gr) 1 and 2 CRS was reported in 18 (34.6%) and 12 (23%) pts, respectively; 3 pts had Gr 3 CRS; none had Gr 4/5 events (defined by ASTCT 2019 criteria). Conclusions Updated data for glofitamab monotherapy SUD show higher preliminary response rates than previously reported in pts with R/R NHL who have failed multiple lines of therapy. CRS was mostly manageable, low-grade, and confined to C1.

7519 Background: Glofitamab (RG6026), a T-cell-engaging, bispecific, full-length antibody, allows bivalent binding to CD20 (B-cells), and monovalent binding to CD3 (T-cells). In NP30179 (NCT03075696), an ongoing multicenter, Phase I dose-escalation and expansion study, 0.6–25mg glofitamab fixed-dosing with obinutuzumab pretreatment (Gpt), showed high, durable complete responses and manageable safety in heavily pretreated R/R NHL (Dickinson, et al. EHA 2020). Glofitamab SUD, in addition to Gpt, allowed dose escalation up to 30mg to maximize efficacy, while mitigating cytokine release syndrome (CRS) (Hutchings, et al. JCO 2021). We present updated efficacy data from glofitamab monotherapy SUD cohorts. Methods: Gpt (1000mg) was given to pts 7 days pre-glofitamab initial dose. Intravenous SUD of glofitamab was given on Day (D) 1 and 8 of Cycle (C) 1 and then at the target dose from C2D1 (2.5/10/16mg or 2.5/10/30mg); treatment continued for up to 12 cycles, every 21 days. Response rates were based on the Lugano criteria (Cheson, et al. JCO 2014). Results: Fifty-two pts received glofitamab SUD; 17 and 35 pts received 2.5/10/16mg and 2.5/10/30mg, respectively. Twenty-eight pts (53.8%) had aggressive NHL (aNHL) and 24 pts had indolent NHL (iNHL). Pts had a median age of 68 (44–85) years and received a median of 3 (1–12) prior lines of therapy. Forty (76.9%) and 38 (73.1%) pts were refractory to their most recent and any prior CD20 therapy, respectively. After a median follow-up of 6.3 months, an updated efficacy analysis was conducted on December 1, 2020. For pts with aNHL (N = 28), the best overall response (OR) and complete metabolic response (CMR) rates were 64.3% and 57.1%, respectively; a trend of improved response was observed with increased target dose, with a CMR rate of 71.4% at 2.5/10/30mg (N = 14). Notably, 4/5 pts (80%) with mantle cell lymphoma (2.5/10/16mg, n = 2; 2.5/10/30mg, n = 2) had CMR. For aNHL, 13/16 CMRs are ongoing, with 8 CMRs lasting > 3 months. For pts with iNHL (N = 24), OR and CMR rates were 79.2% and 70.8%, respectively; 14/17 CMRs are ongoing, with 10 CMRs lasting > 3 months. As of August 3, 2020, common adverse events (52 pts) were CRS (63.5%), neutropenia (38.5%), and pyrexia (32.7%). CRS was mostly confined to C1: 24/50 pts had CRS after 2.5mg; 20/49 pts after 10mg; 2/16 and 8/32 pts had CRS after 16 and 30mg (C2D1), respectively. Grade [Gr] 1 and 2 CRS was reported in 18 (34.6%) and 12 (23%) pts, respectively; 3 pts had Gr 3 CRS; none had Gr 4/5 events (ASTCT 2019). Updated data, including biomarker data on baseline CD20 expression and CD8 levels in the tumor, will be presented. Conclusions: Updated data for glofitamab monotherapy SUD show higher preliminary response rates than previously reported in pts with R/R NHL who have failed multiple lines of therapy. CRS was mostly manageable, of low grade, and confined to the first cycle of treatment. Clinical trial information: NCT03075696.

2505 Background: CPI-006 inhibits CD73, a nucelotidase that converts AMP to adenosine and functions as a lymphocyte adhesion molecule. CPI-006 is a humanized IgG1 FcγR binding-deficient antibody that binds to CD73+ T and B lymphocytes leading to activation of B cells and expression of CD69. This study investigates the immunobiology, safety, and efficacy of CPI-006 monotherapy and in combination with CPI-444, an adenosine A2A receptor (A2AR) antagonist (NCT03454451). Methods: Patients with relapsed solid tumors were treated in a 3 + 3 escalation study with 1, 3, 6 or 12 mg/kg CPI-006 (Q3w IV infusion) monotherapy or in combination with CPI-444 (100 mg, PO, BID). Flow cytometry was performed on blood samples for lymphocyte subset analysis and receptor occupancy. Results: 17 patients were enrolled; 11 monotherapy and 6 combination. CPI-006 was associated with Grade 1 infusion reactions occuring within 30 minutes of the first infusion and were eliminated by premedication with non-steroidals. No DLTs with monotherapy or combination therapy were seen. Receptor occupancy on peripheral lymphocytes was maintained for the full dosing interval at 12 mg/kg. Pharmacodynamic effects suggesting immune modulation were observed within 1 hr of infusion at all dose levels and included a decrease in peripheral blood CD73pos B cells (mean reduction 86%, p < 0.05), increased CD73neg CD4 T cells (mean increase 37%, p < 0.01), and decreased CD8 T cells (mean reduction 20%, p < 0.01) compared to baseline. Overall, CD4:CD8 ratios were increased. Tumor regression was observed in a prostate cancer patient after 5 cycles of monotherapy at 6 mg/kg; peripheral B cells partially returned by the second cycle and reached a new homeostatic level through subsequent cycles. No change in serum immunoglobulins were observed. Conclusions: CPI-006 induces a rapid lymphocyte redistribution, including a transient reduction of circulating CD73pos B cells suggesting redistribution to lymphoid tissues, and an increased CD4:CD8 ratio, consistent with increased TH effector/memory cells in the blood. The treatment has been well-tolerated, and there is early evidence of anti-tumor activity of CPI-006 monotherapy. Clinical trial information: NCT03454451.

Adenosine is present at high concentrations in the tumor microenvironment and is immunosuppressive acting on multiple cell types, including suppression of effector T cells. CD73, an ectonucleotidase that converts AMP to adenosine, is expressed on a subset of B and T cells and is a major source of extracellular adenosine. Elevated CD73 expression has been observed in multiple tumor types and is prognostic in triple negative breast cancer supporting a role for CD73 in tumor progression1. Inhibiting catalytic activity of CD73 is an attractive therapeutic strategy to reduce adenosine-mediated suppression of tumor immunity. We developed two types of humanized monoclonal anti-CD73 antibodies. CPX-006 inhibits CD73 catalytic activity by competing directly with AMP for the active site with an affinity of 0.64 nM. CPX-016 is similar to anti-CD73 antibodies described by others2, and inhibits CD73 activity allosterically by binding to a distal site. This was demonstrated using CD73 expressing cells incubated with APCP, a non-hydrolyzable analog of AMP. APCP competes with CPX-006 for binding to CD73 in contrast to CPX-016. The CPX-016 mechanism requires higher order complexes and results in loss of inhibition at high CPX-016/CD73 ratios. In contrast, CPX-006 reduces catalytic activity completely in cell based assays to levels seen when CD73 gene is deleted using CRISPR technology and inhibition was unaffected at high CPX-006/CD73 ratios. In a functional assay, CPX-006 inhibited immune suppression of T cell function induced by exposure of human PBMCs to AMP through direct inhibition of catalytic activity with a mean EC50 of 137 nM (interferon gamma production) and 189 nM (T cell proliferation) (n=12 donors). We analyzed the prevalence of CD73 expression across tumor histologies by immunohistochemistry including renal cell carcinoma (RCC, n=62), non small cell lung cancer (NSCLC, n=68), melanoma (n= 68) and breast cancer (n=94). CD73 was found to be heterogeneously expressed on tumor cells, immune cells and other stromal elements within each of the histologies examined. Expression on tumor cell only was found in 15% of melanoma and 14% of squamous NSCLC cases. In contrast, tumor cell staining was found in a significant fraction of the adenocarcinoma sub-type of NSCLC (55%). Stromal cell staining to varying degrees was seen in all tumor tissues. In summary, we have a generated a therapeutic antibody, CPX-006, that utilizes a novel mechanism of binding to the CD73 active site to completely inhibit CD73 enzymatic activity and restore T cell function. The finding of CD73 expression on tumor cells and stromal cells in a variety of tumors suggest this as a potential new target for immunotherapy of these malignancies. 1. Loi et al., Proc Natl Acad Sci USA 2013; 110: 11091-11096. 2. Geoghegan et al., mAbs 2016; 8: 454-467. Citation Format: Emily C. Piccione, Glen Mikesell, Barbara Daine-Matsuoka, Kimberly Walter, Richard Miller, Ian McCaffery. A novel CD73-blocking antibody reduces production of immunosuppressive adenosine and restores T cell function [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5577. doi:10.1158/1538-7445.AM2017-5577

Elevated levels of extracellular adenosine within the tumor microenvironment create an immunosuppressive niche that promotes tumor growth and metastasis. Adenosine signaling via the A2A receptor (A2AR) on immune cells suppresses anti-tumor immunity and limits the efficacy of immunotherapies such as anti-PD-L1 or anti-PD-1 monoclonal antibodies (mAbs). CPI-444 is an oral A2AR antagonist that has been evaluated previously in phase 1 clinical trials for non-oncology indications. CPI-444 demonstrates binding to A2AR with a Ki of 3.5 nM and > 50-fold selectivity over other adenosine receptor subtypes. We examined the immune activating and anti-tumor properties of CPI-444 alone and in combination with anti-PD-1/PDL-1 mAbs. In vitro studies using activated primary human T cells demonstrated that CPI-444 fully inhibited the production of intracellular cAMP following incubation of the cells with 5’-N-ethylcarboxamidoadenosine (NECA), a stable analog of adenosine. A2AR agonists suppressed rapid TCR-mediated ERK phosphorylation and, subsequently, production of IL-2 and IFNγ by activated T cells; blockade of A2AR with CPI-444 restored T cell signaling and function. The efficacy of CPI-444 was evaluated in MC38 and CT26 syngeneic mouse tumor models. In the MC38 model, daily treatment of mice with CPI-444 (1, 10, 100 mg/kg) led to a dose-dependent reduction in tumor growth, leading to full tumor elimination in 9/30 treated mice. New tumors failed to establish when the cured mice were re-challenged with MC38 cells, indicating that CPI-444 induced systemic anti-tumor immune memory. Combining CPI-444 with anti-PD-L1 mAb treatment in the MC38 model synergistically inhibited tumor growth and led to elimination of tumors in 9/10 treated mice. In the CT26 model, CPI-444 alone or anti-PD-1 alone led to non-significant reductions in tumor growth; however the combination of CPI-444 and anti-PD-1 led to a synergistic inhibition of tumor growth and prolonged survival compared to either agent alone. These results, and others, suggest that adenosine signaling may be an important resistance mechanism in tumors that incompletely respond to anti-PD-1/PD-L1 mAb therapy. Based on these results and others, we plan to initiate a Phase 1b clinical trial to examine safety, tolerability, biomarkers, and preliminary efficacy of CPI-444 as a single agent and in combination with anti-PD-L1 (atezolizumab) in patients with solid tumors. Citation Format: Stephen Willingham, Po Ho, Robert Leone, Emily Piccione, Carmen Choy, Andrew Hotson, Joseph Buggy, Jonathan Powell, Richard Miller. The adenosine A2A receptor antagonist CPI-444 blocks adenosine-mediated T-cell suppression and exhibits antitumor activity alone and in combination with anti-PD-1 and anti-PD-L1. [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 2337.