Antitumor Activity Of Combination Research Articles

E7386, a Selective Inhibitor of the Interaction between β-Catenin and CBP, Exerts Antitumor Activity in Tumor Models with Activated Canonical Wnt Signaling.

The Wnt/β-catenin signaling pathway plays crucial roles in embryonic development and the development of multiple types of cancer, and its aberrant activation provides cancer cells with escape mechanisms from immune checkpoint inhibitors. E7386, an orally active selective inhibitor of the interaction between β-catenin and CREB binding protein, which is part of the Wnt/β-catenin signaling pathway, disrupts the Wnt/β-catenin signaling pathway in HEK293 and adenomatous polyposis coli (APC)-mutated human gastric cancer ECC10 cells. It also inhibited tumor growth in an ECC10 xenograft model and suppressed polyp formation in the intestinal tract of ApcMin /+ mice, in which mutation of Apc activates the Wnt/β-catenin signaling pathway. E7386 demonstrated antitumor activity against mouse mammary tumors developed in mouse mammary tumor virus (MMTV)-Wnt1 transgenic mice. Gene expression profiling using RNA sequencing data of MMTV-Wnt1 tumor tissue from mice treated with E7386 showed that E7386 downregulated genes in the hypoxia signaling pathway and immune responses related to the CCL2, and IHC analysis showed that E7386 induced infiltration of CD8+ cells into tumor tissues. Furthermore, E7386 showed synergistic antitumor activity against MMTV-Wnt1 tumor in combination with anti-PD-1 antibody. In conclusion, E7386 demonstrates clear antitumor activity via modulation of the Wnt/β-catenin signaling pathway and alteration of the tumor and immune microenvironments, and its antitumor activity can be enhanced in combination with anti-PD-1 antibody. SIGNIFICANCE: These findings demonstrate that the novel anticancer agent, E7386, modulates Wnt/β-catenin signaling, altering the tumor immune microenvironment and exhibiting synergistic antitumor activity in combination with anti-PD-1 antibody.

Abstract OT-03-04: Trastuzumab deruxtecan (T-DXd; DS-8201) combinations in patients with HER2-positive advanced or metastatic breast cancer: A phase 1b/2 open-label, multicenter, dose-finding and dose-expansion study (DESTINY-Breast07)

Abstract Background HER2-targeted therapies have substantially improved survival in patients with HER2-positive (immunohistochemistry [IHC] 3+ or IHC2+/in situ hybridization-positive) advanced or metastatic breast cancer. Despite significant advancements, patients ultimately develop resistance to standard-of-care HER2-targeted therapies. Therefore, a need remains for regimens that prolong disease control and survival in these patients. T-DXd is a HER2-targeted antibody-drug conjugate containing a linker selectively cleaved in tumor cells and a topoisomerase I inhibitor payload with high cell-membrane permeability. T-DXd has been approved by the FDA for use in adult patients with unresectable or metastatic HER2-positive breast cancer who have received ≥ 2 prior anti-HER2-based regimens in the metastatic setting and by Japan’s Ministry of Health, Labour and Welfare for use in patients with HER2-positive unresectable or recurrent breast cancer after prior chemotherapy (use limited to patients refractory to or intolerant of standard treatments). Results from the phase 2 DESTINY-Breast01 trial demonstrated an objective response rate (ORR) of 60.9% per independent central review and a median progression-free survival (PFS) of 16.4 months in a heavily pretreated population (median of 6 prior lines of therapy) of patients with HER2-positive advanced or metastatic breast cancer treated with T-DXd (Modi S, et al. N Engl J Med. 2020;382:610-621). Here, we describe a phase 1b/2 trial evaluating the safety and preliminary antitumor activity of T-DXd combinations in patients with HER2-positive advanced or metastatic breast cancer. Study Description DESTINY-Breast07 is a global, multicenter, open-label, phase 1b/2 dose-finding and dose-expansion trial designed to evaluate the safety, tolerability, and preliminary antitumor activity of T-DXd in combination with other therapies in patients with HER2-positive advanced or metastatic breast cancer. Patients will be enrolled globally at ≈ 110 sites in ≈ 10 countries. The study will initially consist of 4 combination modules, each with 2 parts: dose finding (part 1) and dose expansion (part 2), and a T-DXd monotherapy module (part 2 only). The 4 combination modules will enroll patients for treatment with (1) T-DXd + durvalumab, (2) T-DXd + pertuzumab, (3) T-DXd + paclitaxel, or (4) T-DXd + durvalumab + paclitaxel. New combination treatment modules may be added via protocol amendment. Part 1 of each combination module will enroll patients who have had disease progression on ≥ 1 prior line of therapy in the metastatic setting. In part 2, patients who have received no prior therapy for metastatic disease will be randomized to receive a combination regimen or T-DXd monotherapy. Antitumor activity will be evaluated based on investigator assessment according to RECIST 1.1. The primary endpoint is to assess the safety and tolerability of T-DXd combinations and determine the recommended phase 2 doses. Secondary endpoints include ORR, PFS, duration of response, overall survival, pharmacokinetics, and immunogenicity. Citation Format: Fabrice Andre, Erika Hamilton, Sherene Loi, Peter Schmid, Tinghui Yu, Shiyao Lu, Sarice Boston, Celina D'Cruz, Pia Herbolsheimer, Komal Jhaveri. Trastuzumab deruxtecan (T-DXd; DS-8201) combinations in patients with HER2-positive advanced or metastatic breast cancer: A phase 1b/2 open-label, multicenter, dose-finding and dose-expansion study (DESTINY-Breast07) [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr OT-03-04.

Co-delivery of 5-fluorodeoxyuridine and doxorubicin via gold nanoparticle equipped with affibody-DNA hybrid strands for targeted synergistic chemotherapy of HER2 overexpressing breast cancer

Combination chemotherapy is still of great importance as part of the standard clinical care for patients with HER2 positive breast cancer. As an attractive component, gold nanoparticles (AuNPs) have been extensively studied as biosafety nanomaterials, but they are rarely explored as drug nanocarriers for targeted co-delivery of multiple chemotherapeutics. Herein, a novel affibody-DNA hybrid strands modified AuNPs were fabricated for co-loading nucleoside analogue (5-fluorodeoxyuridine, FUdR) and anthracycline (doxorubicin, Dox). FUdRs were integrated into DNA hybrid strands decorated on AuNPs by DNA solid phase synthesis, and Dox molecules were intercalated into their duplex regions. Affibody molecules coupled to the DNA hybrid strands were distributed the surface of AuNPs, giving them targeting for HER2. The new dual-drug-containing affibody-DNA-AuNPs (Dox@affi-F/AuNPs) owned compact and stable spherical nanostructures, and precise drug loading. Cytotoxicity tests demonstrated that these nanoparticles caused a higher inhibition in HER2 overexpressing breast cancer cells, and showed better synergistic antitumor activity than simple mixture of the two drugs. The related mechanistic studies proved that Dox@affi-F/AuNPs achieved a remarkable combined antitumor activity of Dox and FUdR by promoting more cells to enter apoptosis pathway. Our work provided a nanomedicine platform for targeted co-delivery of nucleoside analog therapeutics and anthracycline anticancer drugs to achieve synergistic treatment of HER2+ cancer.

ALX148, a CD47 Blocker, in Combination with Rituximab in Patients with Non-Hodgkin Lymphoma

Background: CD47 is a myeloid checkpoint upregulated by tumor cells to evade the host's immune response. The high affinity CD47 blocker fusion protein, ALX148, is linked to an inactive immunoglobulin Fc region to minimize toxicity. ALX148 is half the size of an antibody, has been well tolerated, and enhances the innate and adaptive immune response against cancer in combination with anticancer therapeutics across solid and hematologic tumors (ASCO 2020 #3056, EHA 2020 #EP1247). Characterization of ALX148's tolerability profile and antitumor activity in combination with rituximab are reported in patients (pts) with non-Hodgkin Lymphoma (NHL). Methods: Patients with relapsed or refractory CD20-positive B-cell NHL for which no curative therapy was available received ALX148 (10 mg/kg QW or 15 mg/kg QW) in combination with rituximab (375 mg/m2 weekly for 4 doses followed by once monthly for 8 doses). The primary endpoint for the safety population was dose limiting toxicity (DLT). Tumor response, pharmacokinetic (PK), and pharmacodynamic (PD) markers were assessed in all pts. Data are reported as of 30Jun2020 in these fully enrolled cohorts with final data to be updated at the time of presentation. Results: A total of 33 patients with NHL were administered ALX148 in combination with rituximab. Twenty-two pts with median age of 66 years (range 32-80) were administered ALX148, 10 mg/kg QW (ALX10), in combination with rituximab [DLBCL, n=11; mantle cell lymphoma (MCL), n=4; follicular lymphoma (FL), n=5; and marginal zone lymphoma (MZL), n=2]. Eleven pts with median age of 64 years (range 53-78) were administered ALX148, 15 mg/kg QW (ALX15), in combination with rituximab (DLBCL, n=6; MCL, n=1; FL, n=3; and MZL, n=1). There have been no DLTs reported in the fully enrolled safety cohorts, and the MTD of ALX148 in combination with rituximab has not been reached. The maximum ALX148 administered dose is 15 mg/kg QW. Twenty-eight pts experienced any AE, while 16 pts reported mostly low grade treatment-related adverse events (TRAE). The most common TRAEs were rash (21%, n=7), fatigue (9%, n=3), anemia, nausea, neutropenia, and pruritus (6%, n=2 each). With a median follow up of 14 months, objective responses were observed across all histologies in response-evaluable ALX10 pts: 40.9% ORR (4CR,5PR, 6SD, n=22 total) and with a median follow up of 9 months in ALX15 pts: 63.6% ORR (3CR, 4PR, 1SD, n=11 total). Preliminary results indicate favorable ALX148 PK and near complete CD47 receptor occupancy across the dosing interval. Final results will be updated at time of presentation. Conclusions: ALX148 demonstrates excellent tolerability with durable responses in combination with rituximab in patients with relapsed/refractory NHL. The MTD of ALX148 in combination with rituximab was not reached. Encouraging preliminary activity and favorable PK/PD characteristics in combination with rituximab were observed at all dose levels with greater objective response rates reported at the MAD of 15 mg/kg QW. Disclosures Kim: Boryung: Consultancy; Voronoi: Consultancy; F. Hoffmann-La Roche Ltd/Genentech, Inc.: Consultancy; Sanofi: Consultancy; Novartis: Consultancy; Takeda: Consultancy; AstraZeneca and Korea Health Industry Development Institute: Research Funding; AstraZeneca: Consultancy. Lakhani:incyte: Research Funding; merck: Research Funding; mersana: Research Funding; northern biologics: Research Funding; odonate: Research Funding; pfizer: Research Funding; ikena: Research Funding; symphogen: Research Funding; taiRx: Research Funding; tesaro: Research Funding; livzon: Research Funding; loxo: Research Funding; macrogenics: Research Funding; inhibRx: Research Funding; cytomx: Research Funding; formation biologics: Research Funding; forty seven inc: Research Funding; alexion Pharmaceuticals: Research Funding; Alpine Biosciences: Research Funding; ALX Oncology Inc.: Research Funding; Apexian: Research Funding; asana biosciences: Research Funding; ascentage pharma: Research Funding; beigene: Research Funding; celgene: Research Funding; cerulean pharma: Research Funding; constellation pharma: Research Funding; coordination therapeutics: Research Funding; regeneron: Research Funding; sapience therapeutics: Research Funding; shattuck labs: Research Funding; innovent bio: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; jounce therapeutics: Research Funding. Gainor:theravance: Consultancy; adaptimmune: Research Funding; ariad: Research Funding; astrazeneka: Research Funding; blueprint medicines: Research Funding; lily: Consultancy; gilead sciences: Consultancy; merck: Consultancy, Research Funding; moderna therapeutics: Consultancy, Research Funding; tesaro: Research Funding; blueprint medicines: Consultancy; novartis: Research Funding; oncorus: Consultancy; regeneron: Consultancy; bristol-myers Squibb: Consultancy, Research Funding; amgen: Consultancy; array biopharma: Consultancy, Research Funding; agios: Consultancy; ironwood pharmaceuticals: Consultancy; takeda: Consultancy; genentech: Consultancy, Research Funding; jounce therapeutics: Consultancy, Research Funding. Kamdar:Roche: Research Funding. Fanning:ALX Oncology Inc.: Current Employment, Current equity holder in publicly-traded company. Squifflet:ALX Oncology Inc.: Consultancy; IDDI: Current Employment. Jin:ALX Oncology Inc.: Current Employment. Forgie:ALX Oncology Inc.: Current Employment, Current equity holder in publicly-traded company; Pfizer Inc.: Ended employment in the past 24 months. Wan:Tallac Therapeutics: Current Employment, Current equity holder in private company; ALX Oncology Inc.: Consultancy, Current equity holder in publicly-traded company. Pons:ALX Oncology Inc.: Current Employment, Current equity holder in publicly-traded company. Randolph:ALX Oncology Inc.: Current Employment, Current equity holder in publicly-traded company. Kim:F. Hoffmann-La Roche: Research Funding; Pfizer: Research Funding; JJ: Research Funding; Celltrion: Research Funding; Kyowa Kirn: Research Funding; Donga: Research Funding; Mundipharma: Research Funding.

Antitumor efficacy of combined CTLA4/PD-1 blockade without intestinal inflammation is achieved by elimination of FcγR interactions

BackgroundProgrammed cell death protein 1 (PD-1) and CTLA4 combination blockade enhances clinical efficacy in melanoma compared with targeting either checkpoint alone; however, clinical response improvement is coupled with increased risk...

Abstract 5203: MGC018, a duocarmycin-based antibody-drug conjugate targeting B7-H3, exhibits immunomodulatory activity and enhanced antitumor activity in combination with checkpoint inhibitors

Abstract Introduction: B7-H3, a member of the B7 family of immunomodulatory molecules, is overexpressed in a wide range of solid tumors. B7-H3 tumor overexpression has been correlated with disease severity and poor outcome. MGC018 is a duocarmycin-based antibody-drug conjugate (ADC) targeting B7-H3. MGC018 exhibits a favorable preclinical profile, with strong reactivity toward tumor cells and tumor-associated vasculature, limited normal tissue reactivity, and potent antitumor activity toward B7-H3-expressing tumor xenografts. With the emergence of immune-checkpoint blockade as a promising treatment for cancer, interest has grown in understanding the potential of cytotoxic agents to promote immune surveillance or stimulate immune responses to dying cancer cells, leading to immunological memory. ADCs bearing tubulin and DNA modifying cytotoxic payloads have been reported to induce immunological cell death (ICD), mediate antitumor immunity in immunocompetent mouse models, and synergistically combine with checkpoint inhibitors to deliver enhanced antitumor responses. Based on those results, we investigated the immunomodulatory potential of MGC018 and the prospect to combine with checkpoint blockade to enhance antitumor responses. Methods: Syngeneic mouse models expressing human B7-H3 were employed to investigate the antitumor activity of MGC018 in an immune competent setting. Studies were conducted to assess the role of the immune system in the MGC018-mediated antitumor responses, whether MGC018 could impart antitumor memory responses in vivo, and the potential to enhance antitumor responses by combining MGC018 with PD-1 blockade. Results: MGC018 demonstrated specific, dose-dependent in vivo antitumor activity toward human B7-H3-bearing tumors in immunocompetent syngeneic mouse models. Depletion of CD8+ T cells led to reduced antitumor responses, indicating that CD8+ T cells contributed to MGC018-mediated antitumor activity. Antitumor activity in these models was enhanced when MGC018 was combined with anti-PD-1. Treatment with MGC018 alone, or in combination with anti-PD-1, led to complete antitumor responses, and the majority of mice rejected subsequent tumor rechallenge. Conclusion: MGC018, a clinical-stage therapeutic comprised of a humanized antibody targeting B7-H3, conjugated to a duocarmycin-based DNA alkylating payload, exhibits a favorable preclinical profile. Results from these syngeneic model studies support the hypothesis that the antitumor activity of the duocarmycin-based MGC018 ADC (1) mediates immunomodulatory activity, (2) is enhanced by combination with checkpoint blockade, and (3) induces immunological memory. Our findings support a clinical strategy that combines MGC018 with checkpoint blockade for the treatment of B7-H3-expressing solid cancers. Citation Format: Juniper A. Scribner, Michael Chiechi, Pam Li, Thomas Son, Jeff Hooley, Ying Li, Anushka De Costa, Peter Lung, Nicholas Yee-Toy, Francine Chen, Bhaswati Barat, Christina Wolff, Valentina Ciccarone, James Tamura, Scott Koenig, Chet Bohac, Jon Wigginton, Paul A. Moore, Ezio Bonvini, Deryk Loo. MGC018, a duocarmycin-based antibody-drug conjugate targeting B7-H3, exhibits immunomodulatory activity and enhanced antitumor activity in combination with checkpoint inhibitors [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5203.

Abstract 692: Discovery of novel metformin derivatives with potent antitumor activity in combination with immunotherapy for treatment of triple-negative breast cancer

Abstract Triple negative breast cancer (TNBC) occurs in about 15% of breast cancer (BC) patients, yet it accounts for almost 50% of all BC deaths. TNBC is characterized by lack of expression of estrogen, progesterone and HER2 receptors, and it cannot be treated with current targeted therapies. TNBCs are heterogeneous and occur often in younger and African American women. Although initially responsive to some chemotherapies, TNBCs tend to relapse early and metastasize, leading to poor survival. Development of new therapeutic approaches for clinical translation is a high priority. Emerging evidence from epidemiologic and preclinical work suggests that metformin, the most widely used drug to treat type 2 diabetes mellitus, exerts anticancer activity in BC. Diabetic patients treated with metformin have a reduced incidence and better survival from BC. Moreover, TNBC cells are reported to be uniquely sensitive to metformin in vitro, but strong antitumor effects require relatively high metformin doses in vivo. To address this challenge, we used a structure-activity strategy to develop metformin analogues with more potent anticancer action and safety at lower doses in vivo. Using TNBC cell proliferation in vitro to screen drug candidates, selected new metformin analogues were identified that exerted dose-dependent inhibition of cell proliferation at significantly lower concentrations than that of parental metformin (P<0.01). As antitumor effects of metformin are attributed in part to activation of the LKB1-AMPK pathway, we find that metformin analogues also strongly induced phosphorylation of AMPK by Western blot assays and significantly reduced phosphorylation of mTOR downstream signaling pathway components (p70S6K, S6 ribosomal protein, 4E-BP1). Analogues also induced TNBC cell apoptosis at lower doses than metformin. In vivo, metformin analogues were more effective at lower doses given by oral gavage than metformin in suppressing TNBC human tumor xenograft progression in nude mouse models (P<0.001). It is notable that data from clinical trials with immune checkpoint inhibitors (ICI) indicate that TNBCs are susceptible to immunotherapy, but only a minority of patients to date have had clinical benefit. Importantly, our studies indicate that metformin analogues modulate the activity and trafficking of myeloid-derived suppressor cells (MDSC) and tumor infiltrating lymphocytes (TIL) that may significantly impact TNBC responses to ICIs. Thus, combination therapy with metformin analogues and anti-PD-L1 antibodies was more effective at blocking tumor growth in vivo than either treatment given alone using murine 4T1 TNBC implants in syngeneic, immune-competent BALB/C mouse models. In the TNBC microenvironment, analogue treatment with ICIs elicited significant infiltration of predominantly effector T-cells, increased populations of tissue-resident memory T-cells, and a reduction of exhausted T-cells as compared to controls (P<0.01). Moreover, MDSC were significantly decreased after combination therapy as compared to appropriate controls (P<0.05). Since there are currently no specific treatments for TNBC, identification of a new targeted therapeutic approach could ultimately be beneficial for managing patients afflicted with this deadly disease. Funding by California BC RP, NCI U54 CA143930. Citation Format: Diana C. Márquez-Garban, Gang Deng, Begonya Comin-Anduix, Vishaka Muhunthan, Gaoyuan Ma, Jennifer Murphy, Alejandro J. Garcia, Cristian D. Yanes, Lorena R. Burton, Nalo Hamilton, David Shackelford, Michael E. Jung, Richard J. Pietras. Discovery of novel metformin derivatives with potent antitumor activity in combination with immunotherapy for treatment of triple-negative breast cancer [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 692.

Abstract 5355: MSLN-targeted thorium-227 conjugate demonstrates increased antitumor activity in combination with bevacizumab and regorafenib

Abstract Mesothelin-targeted thorium-227 conjugate (MSLN-TTC) is a targeted alpha therapeutic consisting of a MSLN-targeting antibody anetumab covalently attached to a 3,2-HOPO chelator complexed with the alpha emitter thorium-227. It has potent in vivo activity in cell and patient-derived xenograft (PDX) models in monotherapy and in combination with DNA damage repair inhibitors. We evaluated the antitumor efficacy of MSLN-TTC in a mesothelin overexpressing ovarian PDX model (ST206B) in monotherapy and in combination bevacizumab or the multikinase inhibitor regorafenib which both have anti-angiogenic activity. The biodistribution of MSLN-TTC was studied in parallel. Athymic mice were transplanted s.c. with ST206B-derived tumor fragments and treated with MSLN-TTC (250 kBq/kg, Q7Dx2, 0.43 mg/kg) alone or in combination with bevacizumab (1.25 or 5 mg/kg, i.p., Q5D; or 5 mg/kg, single dose) or regorafenib (7.5, 15, or 30 mg/kg, QD, p.o. for 28 days). The biodistribution of the respective treatment groups was analyzed using a germanium detector. For molecular analyses, tumors were stained for γ-H2AX, Ki67, CD31 and α-SMA. MSLN-TTC monotherapy showed high in vivo potency at 2 × 250 kBq/kg with a Treated/Control (T/C) ratio of 0.28 (n=5) on day 29. Monotherapy treatment with bevacizumab and regorafenib showed dose-dependent antitumor activity with T/C ratios ranging from 0.31 (regorafenib 30 mg/kg) to 0.33 (bevacizumab 5 mg/kg, single dose). The in vivo efficacy of MSLN-TTC was further enhanced by combination therapy with bevacizumab (T/C 0.21; n=5) or regorafenib (T/C 0.15; n=5). Combination of MSLN-TTC and regorafenib (30 mg/kg) resulted in more complete and partial responses (3/4 CRs; 1/4 PR) as compared to MSLN-TTC (2/3 PRs; 1/3 PD) at day 141. All treatments were well-tolerated based on body weight assessment; a reversible myelosuppression of white blood cells was observed for MSLN-TTC monotherapy and combination with bevacizumab or regorafenib did not worsen it. In the biodistribution study, tumor-specific accumulation of MSLN-TTC was observed over 336 h (14 days) with lower accumulation in the MSLN-TTC + bevacizumab group (1.25 mg/kg, Q5D, p<0.05; 5 mg/kg, single dose, p<0.05). On the molecular level, MSLN-TTC- and MSLN-TTC/ regorafenib (15 and 30 mg/kg) -treated tumors showed an increase in the DNA damage marker γ-H2AX compared to vehicle. The endothelial cell marker CD31 was decreased in tumors treated with MSLN-TTC and bevacizumab (1.25 mg/kg, Q5D; 5 mg/kg, single dose), but not in MSLN-TTC monotherapy (p<0.05). In summary, MSLN-TTC effectively reduced the growth of primary tumors in the ST206B ovarian cancer model which was further enhanced by addition of bevacizumab and regorafenib. Further studies are needed to investigate the underlying molecular mechanisms. Citation Format: Urs B. Hagemann, Christine Ellingsen, Claudia Kamfenkel, Dieter Zopf, Jesper Fonslet, Carsten Nielsen, Hartwig Hennekes, Alan S. Cuthbertson, Dominik Mumberg. MSLN-targeted thorium-227 conjugate demonstrates increased antitumor activity in combination with bevacizumab and regorafenib [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5355.

Abstract 4538: A safe and potent agonist ADG106 targeting a unique epitope of CD137 with novel mechanism of actions

Abstract Antagonist antibodies targeting immune checkpoint co-inhibitory receptor such as PD-1/PD-L1 have achieved great clinical success in cancer immunotherapy. However, agonistic antibodies targeting the co-stimulatory T cell receptors in the TNFR superfamily, and CD137 in particular, has suffered significant setback due to either dose-dependent severe liver toxicity by Urelumab, or modest clinical anti-tumor activity by Utomilumab. ADG106, a safe and potent antibody targeting a unique epitope of CD137, is shown to hold the great promise to achieve much better efficacy and safety profile for immunotherapy in preclinical and phase 1 studies. ADG106, a fully human agonistic anti-CD137 IgG4 mAb, binds to a unique and conserved epitope with multiple cross-species reactivity, and overlaps with CD137 ligand binding site. This unique antibody acts in a novel mechanism with the following attributes: 1) it agonizes CD137 in a natural ligand-like fashion; 2) it blocks ligand to disable its reverse signaling; 3) it exhibits strong but specific Fc receptor mediated crosslinking in comparison with Utomilumab. ADG106 shows robust dose-dependent single agent anti-tumor activity in multiple syngeneic mouse tumor models and induces durable antigen-specific memory immunity that protects animals from the same re-challenged tumor cells. Consistent with the preclinical observations, ongoing phase I trial shows that the same antibody, ADG106, is well-tolerated in cancer patients in dose escalation from 0.03 to 3 mg/kg; and it also shows single agent activity on circulating T cell activation and clonal expansion in anti-tumor activity. Furthermore, ADG106 has also induced complete remission of the liver metastatic lesion in a lymphoma patient at 1mg/kg dose. Preclinical studies demonstrate that ADG106 enhances activation and inflammatory cytokine release of primed T cells alone or together with other immunomodulatory agents in vitro, as well as exhibits synergistic in vivo anti-tumor activity in combination with variety of other cancer therapies, including checkpoint inhibitors, chemotherapies and targeted agents. Mechanistic analyses suggest that ADG106 stimulates tumor infiltration and expansion of CD4+ and CD8+ T cells, thereby promoting the antitumor responses. These findings support that ADG106-boosted immune response could offer an effective but alternative solution for cancer immunotherapy in single and combination therapies, especially for non-responders to current PD-1/PD-L1 based immunotherapies. Citation Format: Guizhong Liu, Felix Du, Xiaohong She, Yi Zhu, Anthony W. Tolcher, Peter Luo. A safe and potent agonist ADG106 targeting a unique epitope of CD137 with novel mechanism of actions [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 4538.

Abstract 2196: SRF231, a fully human CD47 antibody, potentiates the effects of opsonizing antibodies and cytotoxic chemotherapies in preclinical cancer models

Abstract CD47 is widely expressed on tumor cells and is an important checkpoint of the innate immune response. SRF231, an investigational fully human IgG4 anti-CD47 antibody, blocks CD47-SIRPα interaction and exerts anti-tumor activity via phagocytosis and cell death in a manner dependent on Fc-engagement with CD32a, leading to enhanced myeloid activity. Human IgG1 Fc-containing antibodies that target cancer antigens (opsonizing antibodies) can stimulate macrophage-mediated antibody-dependent cellular phagocytosis (ADCP) in addition to NK cell-mediated antibody-dependent cellular cytotoxicity (ADCC). Also, several chemotherapies trigger cell death response pathways that generate additional “eat-me” signals on tumor cells, rendering them more susceptible to SRF231. Given the dual mechanism of action of SRF231, combination therapies that induce ADCP or cell death were evaluated for their ability to potentiate SRF231-mediated anti-tumor responses in hematologic and solid tumor models. The effect of SRF231 alone and in combination with opsonizing antibodies was evaluated in multiple myeloma (MM) models. In vitro, SRF231 induced phagocytosis of MM cells by human monocyte-derived macrophages. Enhanced ADCP was observed with SRF231 in combination with opsonizing antibodies elotuzumab (anti-SLAMF7) and daratumumab (anti-CD38). In vivo, SRF231 monotherapy following single- and repeat-dosing regimens resulted in 50-80% tumor growth inhibition and significantly increased median survival time in the preclinical MM xenograft models OPM2 and MM1.S. Furthermore, SRF231 strongly synergized with a sub-optimal dose of elotuzumab leading to increased complete response (CR) rates in both models. The effect of SRF231 alone and in combination with chemotherapies was also assessed in non-small cell lung cancer (NSCLC) models. In vivo, SRF231 monotherapy induced anti-tumor activity and significantly increased median survival time in preclinical EGFR mutant (H1975) and EGFR wildtype (A549) NSCLC xenograft models. Cisplatin monotherapy induced modest H1975 anti-tumor activity; however, combination with SRF231 potentiated the effect of cisplatin in this model. Additionally, combination of SRF231 with docetaxel resulted in a 45% CR rate and a significant delay in H1975 tumor regrowth, as compared to a 100% regrowth rate with docetaxel monotherapy. In summary, SRF231 demonstrated significant anti-tumor activity in combination with the anti-SLAMF7 opsonizing antibody, elotuzumab, in preclinical MM xenograft models. Moreover, SRF231 potentiated the effects of taxane and platinum-based standard of care chemotherapies in preclinical NSCLC xenograft models. These results offer further guidance on the clinical development of anti-CD47 modalities in cancer treatment. Citation Format: Kshama A. Doshi, Matthew Rausch, Caroline M. Armet, Li Zhang, Alison M. Paterson, Benjamin H. Lee, Vito J. Palombella, Pamela Holland, Marisa O. Peluso. SRF231, a fully human CD47 antibody, potentiates the effects of opsonizing antibodies and cytotoxic chemotherapies in preclinical cancer models [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2196.

Abstract 3315: Activating innate immune response as strategy for endometrial cancer treatment

Abstract Background: Uterine cancer is the 6th most common cause of death for women in the USA, and about 10,000 women will die from this disease every year. A better understanding of the disease biology has opened the door for more individualized treatment approaches. In the present study we focused on new strategies to potentiate the innate immune response against endometrial cancer. To direct NK cell activity, we used the monoclonal antibody NEO-201, which targets a tumor specific variant of CEACAM-5 and -6, in combination with human recombinant IL-15. NEO-201 is a humanized monoclonal antibody developed through vaccine, and is currently being evaluated in a first-in-human Phase I study currently ongoing at the NCI (NCT03476681). This antibody exerts anti-tumor activity via NK-mediated ADCC. We hypothesized that the expression of tumor associated antigen for NEO-201 correlates with specific tumor biological characteristics, with a goal of designing new rational combinations to potentiate the anti-tumor immune response. Method: To establish the biological relevance of this antigen, we screened a Tissue Microarray (TMA) of endometrial cancer patient tissues by IHC. To identify relevant cell line models, we screened 11 endometrial cancer cell lines for the expression of the antigen recognized by NEO-201 by IHC, WB and FACS and studied the biological characteristics of the same cell lines by whole exome and RNA sequencing. Next, we evaluated NEO-201 anti-tumor activity in combination with IL-15 using ADCC assay in vitro. Result: The expression of the antigen recognized by NEO-201 was confirmed in the patient TMA, where the antigen was detected predominantly on cells membrane and apical surface in 10% of samples. ACI-158 cell line was strongly positive for NEO-201 antigen by WB, FACS and IHC. To evaluate ADCC, NK were isolated from healthy donor PBMCs and incubated with IL15 for 48hours, before performing a chromium release assay. The stimulation with IL-15 increased NK mediated ADCC by 2.5 fold, regardless of the donor genotype. Addition of NEO-201 to facilitate NK mediated ADCC further increased activation by 1.5 to 6 fold. Preliminary sequencing data showed that 5 cell lines express MMR gene mutations, 3 NRAS/KRAS/ERK1-2 mutations, 1 AKT and 1 CTNNB1 mutation, and 2 cell lines carry HER2+ amplification. Conclusion: NEO-201 in combination with IL15 showed promising results in activating NK cells against endometrial cancer cells in vitro. Additional in vitro and in vivo studies are ongoing to optimize the combination and to correlate its activity with cells' biological characteristics. Citation Format: Maria Pia Morelli, Massimo Fanitni, Alexandra Diggs, Kwong Yok Tsang, Philip Arlen, Christina Annunziata. Activating innate immune response as strategy for endometrial cancer treatment [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3315.

A Prospective Phase II Single-arm Study of Niraparib Plus Dostarlimab in Patients With Advanced Non–small-cell Lung Cancer and/or Malignant Pleural Mesothelioma, Positive for PD-L1 Expression and Germline or Somatic Mutations in the DNA Repair Genes: Rationale and Study Design

Treatment with poly ADP ribose polymerase (PARP)1/2 inhibitors represents a novel opportunity to selectively kill a subset of cancer cell types by exploiting their deficiencies in DNA repair, thus leading to synthetic lethality. Treatment of homologous recombination deficient (HRD)-tumors with PARP inhibitors generates significant levels of DNA damage, which has the potential to further increasing tumor mutational burden, promoting neoantigen release, and upregulating both interferons and programmed death ligand-1 (PD-L1) expression, suggesting a potential complementary and synergistic role with immune checkpoint inhibitors in cancer treatment. Here we present the design and rationale of a prospective, phase II, single-arm study aiming to investigate the safety and antitumor activity of the combination of niraparib and dostarlimab in patients with HRD-positive and PD-L1 ≥ 1% advanced non–small-cell lung cancer (NSCLC) and/or malignant pleural mesothelioma (MPM).Considering the prevalence of pathogenetic germline mutations in DNA repair genes, reported to be around 5% to 10% in patients with MPM and NSCLC, a total of 700 to 1000 cases will be screened to identify 70 patients who are HRD-positive/PD-L1 ≥ 1% (N = 35 NSCLC; N = 35 MPM) to be included. Patients will receive the combination of niraparib orally once daily and dostarlimab intravenously. The primary endpoint is progression-free survival. Secondary endpoints are objective response, duration of response, overall survival, and safety.The results of this study will provide evidence on the safety and antitumor activity of niraparib and dostarlimab combination in patients with advanced, HRD-positive and PD-L1 ≥ 1% NSCLC and/or MPM.

A Novel Bifunctional Fusion Protein Comprising of TGF-βRII trap and IL15/IL-15Rα as an Immunotherapeutic against Cancer

Abstract Interleukin-15 (IL-15) is a promising cytokine for cancer therapy. However, it has shown limited antitumor efficacy as monotherapy in clinical trials to date. Removal of immunosuppression of the tumor microenvironment is considered a promising approach to enhance IL-15-mediated immune responses. TGF-β is a key component for creating an immunosuppressive tumor microenvironment. Therefore, we constructed a novel bifunctional fusion protein complex, designated HCW9218, comprising a soluble fusion of two TGFβRII, human tissue factor, and human IL-15, and a second soluble fusion of two TGFβRII and a sushi domain of IL-15Rα. HCW9218 activates IL-15R signaling and the dimeric TGFβRII functions as “trap” for all the three TGF-β isoforms. In healthy and tumor-bearing C57/BL6 mice, subcutaneously administrated HCW9218 was well tolerated with a long serum half-life and was able to stimulate and induce proliferation of CD8+ T cells and NK cells. Splenocytes from HCW9218-treated mice showed enhanced metabolic activity and cytotoxicity against Yac-1 target cells compared to untreated mouse splenocytes. In the syngeneic B16F10 melanoma mouse model, a single-dose of HCW9218 exhibited strong antitumor activity in combination with chemotherapy and TA99 antibody. HCW9218 also significantly increased immune cell infiltration into tumors. Mutagenesis studies demonstrated that both the TGFβRII and IL-15/IL-15Rα domains are essential for antitumor efficacy of HCW9218. Collectively, our preclinical data demonstrate that HCW9218 elicits potent immune responses with a remarkable safety profile and serves as a novel immunotherapeutic against cancer alone or in combination with therapeutic antibodies.

146P Safety and metabolic effects of fasting-mimicking diet in breast cancer patients

Cycles of calorie-restricted, low-carbohydrate, low-protein diets, collectively referred to as fasting-mimicking diets (FMDs), have demonstrated synergistic antitumor activity in combination with cytotoxic chemotherapy (ChT) or endocrine therapies (ETs) in murine models of breast cancer (BC). These effects are mainly mediated through FMD-induced reduction of blood glucose, insulin and insulin-like growth factor 1 (IGF-1) levels. However, the safety and metabolic activity of the FMD in BC patients remain poorly investigated.

Discovery of (2R)-N-[3-[2-[(3-Methoxy-1-methyl-pyrazol-4-yl)amino]pyrimidin-4-yl]-1H-indol-7-yl]-2-(4-methylpiperazin-1-yl)propenamide (AZD4205) as a Potent and Selective Janus Kinase 1 Inhibitor.

JAK1, JAK2, JAK3, and TYK2 belong to the JAK (Janus kinase) family. They play critical roles in cytokine signaling. Constitutive activation of JAK/STAT pathways is associated with a wide variety of diseases. Particularly, pSTAT3 is observed in response to the treatment with inhibitors of oncogenic signaling pathways such as EGFR, MAPK, and AKT and is associated with resistance or poorer response to agents targeting these pathways. Among the JAK family kinases, JAK1 has been shown to be the primary driver of STAT3 phosphorylation and signaling; therefore, selective JAK1 inhibition can be a viable means to overcome such treatment resistances. Herein, an account of the medicinal chemistry optimization from the promiscuous kinase screening hit 3 to the candidate drug 21 (AZD4205), a highly selective JAK1 kinase inhibitor, is reported. Compound 21 has good preclinical pharmacokinetics. Compound 21 displayed an enhanced antitumor activity in combination with an approved EGFR inhibitor, osimertinib, in a preclinical non-small-cell lung cancer (NSCLC) xenograft NCI-H1975 model.

Preclinical Activity of HER2-Selective Tyrosine Kinase Inhibitor Tucatinib as a Single Agent or in Combination with Trastuzumab or Docetaxel in Solid Tumor Models.

HER2 is a transmembrane tyrosine kinase receptor that mediates cell growth, differentiation, and survival. HER2 is overexpressed in approximately 20% of breast cancers and in subsets of gastric, colorectal, and esophageal cancers. Both antibody and small-molecule drugs that target HER2 and block its tyrosine kinase activity are effective in treating HER2-driven cancers. In this article, we describe the preclinical properties of tucatinib, an orally available, reversible HER2-targeted small-molecule tyrosine kinase inhibitor. In both biochemical and cell signaling experiments, tucatinib inhibits HER2 kinase activity with single-digit nanomolar potency and provides exceptional selectivity for HER2 compared with the related receptor tyrosine kinase EGFR, with a >1,000-fold enhancement in potency for HER2 in cell signaling assays. Tucatinib potently inhibits signal transduction downstream of HER2 and HER3 through the MAPK and PI3K/AKT pathways and is selectively cytotoxic in HER2-amplified breast cancer cell lines in vitro. In vivo, tucatinib is active in multiple HER2+ tumor models as a single agent and shows enhanced antitumor activity in combination with trastuzumab or docetaxel, resulting in improved rates of partial and complete tumor regression. These preclinical data, taken together with the phase-I tucatinib clinical trial results demonstrating preliminary safety and activity, establish the unique pharmacologic properties of tucatinib and underscore the rationale for investigating its utility in HER2+ cancers. GRAPHICAL ABSTRACT: http://mct.aacrjournals.org/content/molcanther/19/4/976/F1.large.jpg.

Synergistic antitumor effect of 5-fluorouracil with the novel LSD1 inhibitor ZY0511 in colorectal cancer.

Background:Lysine-specific histone demethylase 1 (LSD1) is a potential target of cancer therapy. In the present study, we aimed to investigate the combined antitumor activity of a novel LSD1 inhibitor (ZY0511) with 5-fluorouracil (5-FU) and elucidate the underlying mechanism in colorectal cancer (CRC).Methods:We evaluated LSD1 expression in CRC tissues from patients who received 5-FU treatment. The synergistic antitumor effect of 5-FU with ZY0511 against human CRC cells was detected both in vitro and in vivo. The underlying mechanism was explored based on mRNA sequencing (mRNA-seq) technology.Results:Overexpression of LSD1 was observed in human CRC tissues, and correlated with CRC development and 5-FU resistance. ZY0511, a novel LSD1 inhibitor, effectively inhibited CRC cells proliferation, both in vitro and in vivo. Notably, the combination of ZY0511 and 5-FU synergistically reduced CRC cells viability and migration in vitro. It also suppressed Wnt/β-catenin signaling and DNA synthesis pathways, which finally induced apoptosis of CRC cells. In addition, the combination of ZY0511 with 5-FU significantly reduced CRC xenograft tumor growth, along with lung and liver metastases in vivo.Conclusions:Our findings identify LSD1 as a potential marker for 5-FU resistance in CRC. ZY0511 is a promising candidate for CRC therapy as it potentiates 5-FU anticancer effects, thereby providing a new combinatorial strategy for treating CRC.

Abstract B100: AO-176, a highly differentiated humanized anti-CD47 antibody, exhibits single-agent and combination antitumor efficacy with chemotherapy and targeted antibodies

Abstract Purpose of study: To determine whether AO-176, a highly differentiated, humanized antibody targeting CD47, shows efficacy alone or in combination with a variety of approved anti-cancer drugs in solid tumors. Methods: We investigated AO-176 as a single agent and in combination with chemotherapies and targeted antibodies, utilizing standard in vitro phagocytosis assays, tumor cell killing assays, and in vivo xenograft models. Results: AO-176 is a highly-differentiated anti-CD47 antibody that not only blocks the CD47/SIRPα interaction to stimulate phagocytosis of tumor cells, but also exerts direct killing activity on tumor cells (non-ADCC), induces immunogenic cell death, and exhibits preferential binding to tumor cells compared to normal cells. In addition, tumor-specific CD47 binding by AO-176 increases in the acidic tumor microenvironment. As a single agent, AO-176 induced cell killing (14-52% Annexin V positivity, EC50 = 1-30 μg/ml) and phagocytosis (10-34%, EC50 = 0.8-3.3 μg/ml) in ovarian, gastric, non-small cell lung, head and neck, colorectal, thyroid, pancreatic and endometrial solid tumor cell lines. When combined with tumor-targeted antibodies (i.e. cetuximab against head and neck and colorectal cancer cell lines, or the checkpoint inhibitor avelumab against ovarian cancer cell lines), AO-176 significantly enhanced phagocytosis of the tumor cells in vitro. In combination with the chemotherapeutics paclitaxel and cisplatin, AO-176 also potentiated direct tumor killing of gastric cancer cells in vitro. In vivo, AO-176 showed potent single-agent anti-tumor activity against ovarian and gastric tumor xenografts. These data add to the previous pre-clinical anti-tumor activity of AO-176 reported in breast cancer, multiple myeloma, and non-Hodgkin’s lymphoma xenografts. When cisplatin or paclitaxel was added to the AO-176 treatment regimen against xenografted ovarian tumors in vivo, significant combination anti-tumor activity was observed. We then sought to extend our promising in-vitro findings from combining AO-176 with a checkpoint inhibitor to in-vivo models. As AO-176 is human CD47-specific, we utilized an in-house murine reactive anti-CD47 blocking antibody and combined it with a murine-reactive anti-PDL1 antibody to treat MC38 murine tumors established in syngeneic mice. Combination of the two antibodies significantly improved anti-tumor efficacy compared to either single agent. Conclusions: AO-176 has demonstrated broad in vitro phagocytosis/killing as well as in vivo efficacy that supports its development, both as a single agent and in combination with other anti-cancer drugs. With a highly differentiated mechanism of action and binding profile, AO-176 may have the potential to improve upon the safety and efficacy profiles relative to other agents in this class. AO-176 is currently being evaluated in a Phase 1 clinical trial (NCT03834948) for the treatment of patients with select solid tumors. Citation Format: Casey Wilson, Myriam Bouchlaka, Robyn Puro, Ben Capoccia, Ronald Hiebsch, Prabir Chakraborty, Michael Donio, Vicki Sung, Daniel Pereira. AO-176, a highly differentiated humanized anti-CD47 antibody, exhibits single-agent and combination antitumor efficacy with chemotherapy and targeted antibodies [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics; 2019 Oct 26-30; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2019;18(12 Suppl):Abstract nr B100. doi:10.1158/1535-7163.TARG-19-B100

First-in-Human Study of Abbv-621, a TRAIL Receptor Agonist Fusion Protein, in Patients (Pts) with Relapsed/Refractory (RR) Acute Myeloid Leukemia (AML) and Diffuse Large B-Cell Lymphoma (DLBCL)

Background: Apoptotic cell death can be triggered by activation of extrinsic and intrinsic signaling pathways. Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL), a member of the TNF superfamily, binds to its death receptors TRAIL-R1 (DR4) and TRAIL-R2 (DR5) to selectively activate the extrinsic apoptotic pathway in cancer cells. ABBV-621 is a second-generation TRAIL receptor agonist with antitumor activity as monotherapy (621-mono) in preclinical models of AML and DLBCL. The intrinsic apoptotic pathway is regulated by the BCL2 protein family, commonly overexpressed in hematologic malignancies. Venetoclax (VEN), a highly selective small-molecule BCL2 inhibitor, has shown antitumor activity in combination therapy in AML and DLBCL. In preclinical and xenograft models of AML and DLBCL, the ABBV-621 and VEN combination (621-VEN) had antitumor activity superior to either agent alone. This first-in-human study evaluated ABBV-621 as single agent and in combination in pts with advanced solid tumors and hematologic malignancies (NCT03082209). Safety and tolerability of ABBV-621 in advanced solid tumors have previously been presented (Ratain et al. J Clin Oncol 2019;37[suppl]: abstr 3013). Here, we report preliminary data for 621-mono in pts with RR AML and for 621-VEN in pts with RR AML and DLBCL. Methods: Adult pts with RR AML or DLBCL (ECOG 0-2) were enrolled. Pts with AML received ABBV-621 at 1.25-, 3.75-, 7.5-mg/kg doses in the 621-mono and at 3.75-mg/kg dose in the 621-VEN arms. Pts in the DLBCL 621-VEN arm received ABBV-621 at 3.75- and 7.5-mg/kg doses. ABBV-621 was administered intravenously on D1, 8, and 15 of a 21-D cycle; in 621-VEN cohorts pts received 400 mg oral VEN daily, and could be escalated to 800 mg. The primary endpoint was safety. In addition, preliminary antitumor efficacy and ABBV-621 binding to decoy receptors on neutrophils from peripheral blood were assessed. Results: As of Jun 2019, 17 pts were enrolled. Pts in AML 621-mono arm (1.25 [1], 3.75 [1], 7.5 [2] mg/kg): 1 male; median (med) age, 75 yr (range 71-82); med prior treatments, 2.5 (range 1-4); med time on treatment, 15 D (range 1-70). Pts in AML 621-VEN arm (3.75 mg/kg [7]): 5 male; med age, 71 yr (60-79); med prior treatments, 2 (1-2); med time on treatment, 26 D (1-77). Pts in DLBCL 621-VEN arm (3.75 [3], 7.5 [3] mg/kg): 4 male; med age, 57 yr (40-75); stage 4 (3); med prior treatments, 2.5 (1 to ≥5); med time on treatment, 26 D (8-36). One pt in the AML 621-VEN 3.75-mg/kg dose cohort had increases in alanine aminotransferase, aspartate aminotransferase and bilirubin as dose-limiting toxicities. Sixteen pts experienced adverse events (AEs) irrespective of causality. A summary of AEs is shown in Table. One pt in the AML 621-mono 7.5-mg/kg dose cohort died due to AML progression, unrelated to ABBV-621. Antitumor activity was observed in 1 pt in the AML 621-VEN arm (with complex cytogenetics and TP53 mutation) who reached complete remission (CR). One pt in the DLBCL 621-VEN 3.75-mg/kg cohort had stable disease, 2 with AML had resistant disease (1 in 621-mono [7.5 mg/kg] and 1 in 621-VEN), and 7 had progressive disease (PD; 1 in AML 621-mono [1.25 mg/kg], 2 in AML 621-VEN, and 4 in DLBCL 621-VEN [2 each in 3.75- and 7.5-mg/kg] cohorts). Using flow cytometry, saturation of ABBV-621 binding to decoy receptors on neutrophils was observed at 2 h postdosing, followed by dose-dependent desaturation of receptors in pts with DLBCL at 48-168 h. In AML 621-VEN pts, ABBV-621 remained bound to decoy receptors for up to 168 h; in DLBCL 621-VEN pts, the duration of binding was higher at ABBV-621 7.5 mg/kg compared with 3.75 mg/kg. In AML, the baseline frequency of myeloblasts was higher in pts with PD than CR, while that of myelomonocytes was higher in the pt with CR. The frequency of myeloblasts and myelomonocytes expressing DR4 and DR5 at baseline was highest in the pt with CR (Figure). Conclusions: ABBV-621 was tolerated and showed antitumor activity in combination with VEN in pts with RR AML. Disclosures de Jonge: Faron Pharmaceuticals Ltd.: Consultancy. Carneiro:Actuate Therapeutics: Research Funding; Bayer: Research Funding; Pfizer: Research Funding; AstraZeneca: Research Funding; Medimmune: Research Funding; Astellas: Research Funding; AbbVie: Research Funding. Devriese:MSD: Consultancy. Penugonda:AbbVie: Employment, Other: Stock/stock options. Petrich:Abbvie: Employment, Equity Ownership. Nuthalapati:AbbVie: Employment, Other: Stock/stock options. Motwani:AbbVie: Employment, Other: Stock/stock options. Modi:AbbVie: Employment, Other: Stock/stock options. Chang:AbbVie: Employment, Other: Stock/stock options. Calvo:Celgene: Consultancy; Roche/Genentech: Consultancy, Other: travel/accommodations/expenses; Seattle Genetics: Consultancy; AstraZeneca: Consultancy, Research Funding; PsiOxus: Consultancy; Amcure: Consultancy; START: Other: stock/ownership interests, Research Funding; Janssen-Cilag: Consultancy; EUSA Pharma: Consultancy; Novartis: Consultancy, Research Funding, Speakers Bureau; Oncoart Associated: Other: stock/ownership interests; Guidepoint Global: Consultancy; Nanobiotix: Consultancy; HM Hospitales Group: Honoraria; AbbVie: Consultancy; BeiGene: Research Funding; Servier: Consultancy; International Cancer Consultants: Other: stock/ownership interests; Foundation INTHEOS: Other: president and founder; Gerson Lehrman Group: Consultancy; Pfizer: Consultancy. Moreno:Puma Biotechnology: Consultancy; Sanofi/Regeneron: Other: travel/accommodations/expenses.

A Phase 1 Study of ALX148, a CD47 Blocker, in Combination with Rituximab in Patients with Non-Hodgkin Lymphoma

Background: CD47 is a myeloid checkpoint upregulated by tumor cells to evade the host's immune response. ALX148 is a fusion protein comprised of a high affinity CD47 blocker linked to an inactive human immunoglobulin Fc region. In combination with anti-tumor antibodies, ALX148 enhances the innate and adaptive immune response against cancer. ALX148 has previously been shown to be well tolerated both as a single agent and in combination with pembrolizumab or trastuzumab in a range of solid tumors with no maximum tolerated dose (MTD) identified (SITC 2018 #P335, ASCO 2019 #2514). Characterization of ALX148's safety profile and antitumor activity in combination with rituximab are reported in patients (pts) with both aggressive and indolent histologies of non-Hodgkin Lymphoma (NHL). Methods: Patients with relapsed or refractory CD20-positive B-cell NHL for which no curative therapy was available received ALX148 (10 mg/kg QW) in combination with rituximab (375 mg/m2 weekly for 4 doses followed by once monthly for 8 doses). The primary endpoint for the safety confirmation population was first cycle dose limiting toxicity (DLT). Tumor response, pharmacokinetic (PK), and pharmacodynamic (PD) markers were assessed in all pts. Preliminary clinical data from the fully enrolled cohort is reported as of July 15, 2019. Results: Twenty pts (15 males, 5 females) with NHL were administered ALX148 in combination with rituximab (DLBCL, n=11; mantle cell lymphoma, n=4; follicular lymphoma, n=3; and marginal zone lymphoma, n=2). The pts median age was 66 years (range 32-80) and ECOG PS 0/1 was 7/13. Patients had a median of 3 prior lines of therapy (range 1-7) with 50% having rituximab-refractory tumors. There were no dose limiting toxicities reported and the MTD of ALX148 in combination with rituximab was not reached. The maximum administered dose was 10 mg/kg QW. Sixteen pts experienced any AE, while 11 pts reported mostly low grade treatment-related adverse events (TRAE). The most common TRAEs were rash (20%, n=4); anemia, fatigue, nausea, neutropenia and decreased platelets (10%, n=2 each). One TRAE ≥ G3 of neutropenia occurred in more than 1 patient (1G3, 1G4). As of the data cut off with a median follow-up time of 3 (0.3-14) months, preliminary tumor response was assessed in 17 evaluable pts using the Lugano Classification, 2014. The ORR was 35% across all tumor histologies, with a 50% ORR reported in indolent (FL+MZL), and 31% ORR reported in aggressive (DLBCL+MCL) histologies. The overall DCR was 41%. Six pts achieved partial response [(2) follicular, (2) DLBCL, (2) mantle cell]. Four pts achieved SD [(1) each of follicular, marginal zone, DLBCL(>1yr), and mantle cell]. Preliminary results indicate favorable ALX148 PK and near complete CD47 receptor occupancy across the dosing interval. Results will be updated at time of presentation. Conclusions: ALX148 demonstrates excellent tolerability with favorable PK/PD characteristics in combination with rituximab in patients with relapsed/refractory NHL. The MTD of ALX148 in combination with rituximab was not reached. Encouraging preliminary activity in combination with rituximab was observed with objective responses reported in heavily pretreated and rituximab-refractory patients. Clinical trial information: NCT03013218 Disclosures Kim: AstraZeneca: Consultancy, Research Funding; Novartis: Consultancy; Sanofi: Consultancy; Bayer: Consultancy; Takeda: Consultancy. Lakhani:ALX Oncology Inc.: Research Funding; Ascentage Pharma: Research Funding; Asana Biosciences: Research Funding; BeiGene: Research Funding; Constellation Pharmaceuticals: Research Funding; Alexion Pharma: Research Funding; Cerulean Pharma: Research Funding; Forty Seven: Research Funding; Loxo: Research Funding; Macrogenics: Research Funding; Merck: Research Funding; Pfizer: Research Funding; Regeneron: Research Funding; TaiRx: Research Funding; Apexian: Research Funding; Formation Biologics: Research Funding; Coordination Therapeutics: Research Funding; Symphogen: Research Funding; CytomX: Research Funding; InhbRx: Research Funding; Incyte: Research Funding; Jounce Therapeutics: Research Funding; Livzon: Research Funding; Northern Biologics: Research Funding; Tesaro: Research Funding; Innovent Biologics: Research Funding. Gainor:BMS: Research Funding; Genentech/Roche: Other: grant; Takeda: Other: grant, personal fees; Blueprint: Research Funding; Loxo: Research Funding; Oncorus: Other: grant , personal fees; Regeneron: Other: grant,personal fees; Pfizer: Other: grant personal fees; Incyte: Other: grant personal fees; Novartis: Other: grant, personal fees; Merck: Other: grant personal fees; Agios: Other: personal fees; Amgen: Other: personal fees; Array: Research Funding; Tesaro: Research Funding; Moderna: Other: grant; Adaptimmune: Other: grant; ALX Oncology: Other: grant; Ironwood Pharma: Equity Ownership. Kamdar:AstraZeneca: Consultancy; Pharmacyclics: Consultancy; Genentech: Consultancy; Seattle Genetics: Speakers Bureau. Fanning:ALX Oncology Inc: Employment, Equity Ownership. Squifflet:IDDI: Employment; ALX Oncology Inc: Consultancy. Jin:ALX Oncology Inc.: Consultancy. Wan:ALX Oncology Inc.: Employment, Equity Ownership. Pons:ALX Oncology Inc.: Employment, Equity Ownership; venBio: Employment, Membership on an entity's Board of Directors or advisory committees. Randolph:ALX Oncology Inc: Employment, Equity Ownership; venVio: Consultancy; Carrick: Equity Ownership. Kim:Novartis: Research Funding; Donga: Research Funding; Kyowa-Kirin: Research Funding; Novartis: Research Funding; J + J: Research Funding; F. Hoffmann-La Roche Ltd: Research Funding; Celltrion: Research Funding.