scholarly journals 474 Phase 1 study of SEA-TGT, a human, nonfucosylated anti-TIGIT monoclonal antibody with enhanced immune-effector function, in patients with advanced malignancies (SGNTGT-001, trial in progress)

2021 ◽  
Vol 9 (Suppl 3) ◽  
pp. A503-A503
Author(s):  
Diwakar Davar ◽  
Vincent Ribrag ◽  
Clementine Sarkozy ◽  
Elena Garralda ◽  
Honey Kumar Oberoi ◽  
...  

BackgroundT-cell immunoreceptor with immunoglobulin and immunoreceptor tyrosine-based inhibitory domains (TIGIT), and costimulatory receptor CD226 competitively bind 2 ligands, CD155 and CD112, which are expressed by tumor cells and antigen-presenting cells in the tumor microenvironment.1 2 Dual TIGIT/programmed cell death protein-1 (PD-1) blockade increased tumor antigen-specific CD8+ T-cell expansion and function in vitro and promoted potent antitumor response in vivo.3 4 TIGIT/PD-1 dual blockade using a TIGIT monoclonal antibody (mAb) with intact Fc produced clinical responses in advanced cancer.5 SEA-TGT is an investigational, human, nonfucosylated mAb directed against TIGIT. SEA-TGT binds to TIGIT, blocking inhibitory checkpoint signals directed at T cells. SEA-TGT enhances binding to activating FcγRIIIa and decreases binding to inhibitory FcγRIIb; this depletes immunosuppressive regulatory T cells and amplifies naive and memory T cells, potentially augmenting PD-1 inhibition effects. Preclinically, at suboptimal doses, SEA-TGT plus anti-PD-1 mAbs had superior antitumor activity than either agent alone.6MethodsSafety and antitumor activity of SEA TGT in ~377 adults (≥18 years) will be evaluated in this phase 1, multicenter, open-label, dose-escalation/expansion study. Part A will assess the safety/tolerability of SEA TGT to determine maximum tolerated and recommended doses. Part B will assess the safety and antitumor activity of the recommended dose in disease-specific expansion cohorts. Part C will assess SEA-TGT plus sasanlimab in dose-expansion cohorts after an initial safety run-in. Patients with histologically/cytologically confirmed relapsed/refractory/progressive metastatic solid tumors including non-small cell lung cancer (NSCLC), head and neck squamous cell carcinoma (HNSCC), gastric/gastroesophageal junction carcinoma, cutaneous melanoma, bladder, cervical, ovarian or triple-negative breast cancer, or selected lymphomas will be eligible for Parts A and B. Part C will enroll patients with histologically confirmed advanced NSCLC (high [tumor proportion score (TPS) ≥50%] and low [TPS=1–49%] PD ligand 1 [PD-L1] expression), cutaneous melanoma, and HNSCC without previous anti–PD-1/PD-L1 therapy exposure. SEA TGT will be administered on Day 1 of 21-day cycles.Laboratory abnormalities, adverse events, dose-limiting toxicities, and dose-level safety and activity are primary endpoints. Secondary endpoints are objective response (OR) and complete response (CR) rates, duration of OR/CR, progression-free survival, overall survival, pharmacokinetics (PK), and antidrug antibodies. Exploratory analysis will include pharmacodynamics (PD), PK/PD relationships, biomarkers, and resistance to SEA-TGT. This trial is recruiting in Europe and North America.Trial RegistrationNCT04254107ReferencesBlake SJ, Dougall WC, Miles JJ, et al. Molecular pathways: Targeting CD96 and TIGIT for cancer immunotherapy. Clin Cancer Res 2016;22(21):5183–5188.Chauvin JM, Zarour HM. TIGIT in cancer immunotherapy. J ImmunoTher Cancer 2020;8:e000957.Johnston RJ, Comps-Agrar L, Hackney J, et al. The immunoreceptor TIGIT regulates antitumor and antiviral CD8+ T cell effector function. Cancer Cell 2014;26(6):923–937.Chauvin JM, Pagliano O, Fourcade J, et al. TIGIT and PD-1 impair tumor antigen-specific CD8+ T cells in melanoma patients. J Clin Invest 2015;125(5):2046–2058.Rodriguez-Abreu D, Johnson ML, Hussein MA, et al. Primary analysis of a randomized, double-blind, phase 2 study of the anti-TIGIT antibody tiragolumab (tira) plus atezolizumab (atezo) versus placebo plus atezo as first-line (1L) treatment in patients with PD-L1-selected NSCLC (CITYSCAPE). J Clin Oncol 2020;38(15 suppl):9503.Smith A, Zeng W, Lucas S, et al. Poster 1583. SEA-TGT is an empowered anti-TIGIT antibody that displays superior combinatorial activity with several therapeutic agents. Presented at: American Association for Cancer Research Annual Meeting; April 9–14, 2021; Virtual Meeting.Ethics ApprovalInstitutional review boards or independent ethics committees of participating sites approved the trial, which will be conducted in compliance with the Declaration of Helsinki and International Conference on Harmonisation Guidelines for Good Clinical Practice. All patients will provide written informed consent.

2010 ◽  
Vol 2010 ◽  
pp. 1-12 ◽  
Author(s):  
Philippe Fournier ◽  
Volker Schirrmacher

New approaches of therapeutic cancer vaccination are needed to improve the antitumor activity of T cells from cancer patients. We studied over the last years the activation of human T cells for tumor attack. To this end, we combined the personalized therapeutic tumor vaccine ATV-NDV—which is obtained by isolation, shortin vitroculture, irradiation, and infection of patient's tumor cells by Newcastle Disease Virus (NDV)—with bispecific antibodies (bsAbs) binding to this vaccine and introducing anti-CD3 (signal 1) and anti-CD28 (signal 2) antibody activities. This vaccine called ATV-NDV/bsAb showed the unique ability to reactivate a preexisting potentially anergized antitumor memory T cell repertoire. But it also activated naive T cells to have antitumor propertiesin vitroandin vivo. This innovative concept of direct activation of cancer patients' T cells via cognate and noncognate interactions provides potential for inducing strong antitumor activities aiming at overriding T cell anergy and tumor immune escape mechanisms.


2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Chen Zou ◽  
Siyuan Wu ◽  
Haigang Wei ◽  
Hailing Luo ◽  
Zhe Tang ◽  
...  

LINC01355 has been demonstrated to be dysregulated in several cancers. However, the exact molecular function of LINC01355 in the pathogenesis of OSCC remains unstudied. Here, we reported the effect of LINC01355 in OSCC and investigated the mechanisms. Firstly, we found that the results indicated LINC01355 was increased in OSCC cells. Knockdown of LINC01355 repressed OSCC cell proliferation, migration, and invasion. Recently, immunotherapy is a significant method for the treatment of cancers, in which CD8+ T cells exhibit a significant role. The influence of LINC01355 on the antitumor activity of CD8+ T cells was also focused in this study. As shown, the silence of LINC01355 could repress OSCC tumor growth via inducing CD8+ T cell immune responses. In addition, we found that downregulation of LINC01355 significantly restrained CD8+ T cell apoptosis, induced CD8+ T cell percentage, and enhanced the cytolysis activity when cocultured with OSCC cells. It has been reported that the Notch pathway represses CD8+ T cell activity in cancer patients. In our present study, we displayed that lack of LINC01355 suppressed OSCC malignant behaviors and enhanced the antitumor activity of CD8+ T cells via inactivating Notch signaling. We showed that decreased LINC01355 significantly restrained the Notch signal via a decrease of Notch-1, JAG-1, and HES-1. Repression of Notch1 reversed the effect of LINC01355 in OSCC cells. In conclusion, it was implied that LINC01355 might induce the development of OSCC via modulating the Notch signal pathway, which could provide a candidate therapeutic target for OSCC.


Blood ◽  
2019 ◽  
Vol 134 (Supplement_1) ◽  
pp. 244-244
Author(s):  
Javier Munoz ◽  
Samantha Jaglowski ◽  
Matthew S. McKinney ◽  
Iris Isufi ◽  
Patrick J. Stiff ◽  
...  

Background: The Antibody-Coupled T-cell Receptor (ACTR) platform is an autologous engineered T-cell therapy that combines the cell-killing ability of T cells and the tumor-targeting ability of co-administered antibodies to exert potent antitumor immune responses. ACTR087 comprises the extracellular domain of CD16 linked to a CD3ζ-signaling domain and a 4-1BB co-stimulatory domain. Here we present the clinical experience from Study ATTCK-20-2 (NCT02776813), a multicenter, phase 1 study of ACTR087 in combination with rituximab in subjects with relapsed or refractory (R/R) CD20+ NHL. Methods: The main objectives of this first-in-human study were to evaluate the safety and antitumor activity of ACTR087+rituximab. Other objectives included evaluating ACTR T-cell persistence and other correlative biomarkers. Subjects must have had CD20+ NHL that was R/R after prior treatments, which must have included anti-CD20 antibody-containing chemotherapy. Subjects received lymphodepleting chemotherapy (cyclophosphamide and fludarabine) for 3 days, followed by rituximab and a single dose of ACTR087. Additional doses of rituximab were administered q3w until disease progression, unacceptable toxicity, or Investigator decision. The study included a dose escalation phase (increasing doses of ACTR087) and an expansion phase (ACTR087 at the preliminary recommended phase 2 dose [RP2D]); all subjects received rituximab at a fixed dose of 375 mg/m2 q3w. Results: Two dose levels (DL) of ACTR087 were evaluated during dose escalation (n=17). The MTD was exceeded at DL2, with severe cases of cytokine release syndrome (CRS) and neurotoxicity. Statistical analysis of the relationship between non-hematologic toxicity and ACTR+ T-cell doses was retrospectively performed (two-parameter Bayesian logistic regression model) to estimate an RP2D of 35×106 ACTR+ T cells. Nine subjects enrolled in an expansion cohort and received ACTR087 at this RP2D in combination with rituximab. Among all subjects treated (n=26), the majority (69%) were diagnosed with DLBCL. Subjects had received a median of 3 (range 1-9) prior lines of therapy, with 77% having received ≥3 prior lines. ACTR087 showed dose-dependent expansion with peak levels generally observed 7 to 14 days post administration. In subjects with ongoing clinical response (CR), ACTR remained detectable through the last timepoint evaluated. Across all cohorts, Grade ≥3 TEAEs reported in >3 subjects regardless of causality were limited to hematologic events. Potential T cell-mediated toxicities were observed, including 4 serious cases of CRS (Gr 4 in 2 subjects, both with fatal sepsis) and 2 serious cases of neurotoxicity (1 Gr 5, 1 Gr 4 in a subject with fatal septic shock). Elevated baseline inflammatory markers (eg, ferritin, CRP) were observed in patients who developed Gr ≥3 CRS and neurotoxicity post ACTR087. Of note, severe CRS presented without fever and events occurred >7 days post ACTR087. Clinical activity was reported with an ORR of 50% in all dose levels tested, including durable complete responses, with one subject in CR for 869+ days (Table 1). Conclusions: ACTR087+rituximab demonstrated antitumor activity, with observed safety events that are expected with other autologous T-cell products. The time to onset and clinical presentation of severe CRS and neurotoxicity events in this study informed the safety monitoring and adverse reaction management guidance across clinical studies of ACTR T-cell products. Data from this first-in-human study of ACTR087+rituximab confirm the proof of concept and will be used to guide further development for the ACTR platform. Updated clinical data, as well as expanded biomarker correlations to efficacy and safety, will be presented. Disclosures Munoz: Pharmacyclics /Janssen: Consultancy, Research Funding, Speakers Bureau; Pfizer: Consultancy; Fosunkite: Speakers Bureau; AstraZeneca: Speakers Bureau; Kyowa: Consultancy, Honoraria, Speakers Bureau; Seattle Genetics: Consultancy, Honoraria, Research Funding, Speakers Bureau; Celgene/Juno: Consultancy, Research Funding; Genentech: Consultancy, Research Funding, Speakers Bureau; Kite/Gilead: Consultancy, Research Funding, Speakers Bureau; Bristol-Myers Squibb: Consultancy; Alexion: Consultancy; Portola: Research Funding; Incyte: Research Funding; Bayer: Consultancy, Speakers Bureau; Merck: Consultancy. Jaglowski:Kite: Consultancy, Other: advisory board, Research Funding; Novartis: Consultancy, Other: advisory board, Research Funding; Unum Therapeutics Inc.: Research Funding; Juno: Consultancy, Other: advisory board. Isufi:Celgene: Consultancy; Novartis: Consultancy; Astra Zeneca: Consultancy. Stiff:Gamida-Cell: Research Funding; Incyte: Research Funding; Cellectar: Research Funding; Unum: Research Funding; Gilead/Kite Pharma: Consultancy, Honoraria, Research Funding; Amgen: Research Funding. Sachs:Unum Therapeutics Inc.: Employment. Ranger:Unum Therapeutics Inc.: Employment. Harris:Unum Therapeutics Inc.: Employment. Payumo:Unum Therapeutics Inc.: Employment. Akard:Bristol-Myers Squibb: Speakers Bureau; Gilead: Speakers Bureau; Takeda: Speakers Bureau; Novartis: Speakers Bureau; Celgene: Speakers Bureau.


2020 ◽  
Vol 4 (18) ◽  
pp. 4483-4493
Author(s):  
Iosifina P. Foskolou ◽  
Laura Barbieri ◽  
Aude Vernet ◽  
David Bargiela ◽  
Pedro P. Cunha ◽  
...  

Abstract Cancer immunotherapy is advancing rapidly and gene-modified T cells expressing chimeric antigen receptors (CARs) show particular promise. A challenge of CAR-T cell therapy is that the ex vivo–generated CAR-T cells become exhausted during expansion in culture, and do not persist when transferred back to patients. It has become clear that naive and memory CD8 T cells perform better than the total CD8 T-cell populations in CAR-T immunotherapy because of better expansion, antitumor activity, and persistence, which are necessary features for therapeutic success and prevention of disease relapse. However, memory CAR-T cells are rarely used in the clinic due to generation challenges. We previously reported that mouse CD8 T cells cultured with the S enantiomer of the immunometabolite 2-hydroxyglutarate (S-2HG) exhibit enhanced antitumor activity. Here, we show that clinical-grade human donor CAR-T cells can be generated from naive precursors after culture with S-2HG. S-2HG–treated CAR-T cells establish long-term memory cells in vivo and show superior antitumor responses when compared with CAR-T cells generated with standard clinical protocols. This study provides the basis for a phase 1 clinical trial evaluating the activity of S-2HG–treated CD19-CAR-T cells in patients with B-cell malignancies.


2002 ◽  
Vol 195 (11) ◽  
pp. 1407-1418 ◽  
Author(s):  
Claes Öhlén ◽  
Michael Kalos ◽  
Laurence E. Cheng ◽  
Aaron C. Shur ◽  
Doley J. Hong ◽  
...  

CD8+ T cell tolerance to self-proteins prevents autoimmunity but represents an obstacle to generating T cell responses to tumor-associated antigens. We have made a T cell receptor (TCR) transgenic mouse specific for a tumor antigen and crossed TCR-TG mice to transgenic mice expressing the tumor antigen in hepatocytes (gag-TG). TCRxgag mice showed no signs of autoimmunity despite persistence of high avidity transgenic CD8+ T cells in the periphery. Peripheral CD8+ T cells expressed phenotypic markers consistent with antigen encounter in vivo and had upregulated the antiapoptotic molecule Bcl-2. TCRxgag cells failed to proliferate in response to antigen but demonstrated cytolytic activity and the ability to produce interferon γ. This split tolerance was accompanied by inhibition of Ca2+ flux, ERK1/2, and Jun kinasephosphorylation, and a block in both interleukin 2 production and response to exogenous interleukin 2. The data suggest that proliferation and expression of specific effector functions characteristic of reactive cells are not necessarily linked in CD8+ T cell tolerance.


2020 ◽  
Vol 8 (Suppl 3) ◽  
pp. A417-A417
Author(s):  
Elizabeth Martinez ◽  
Jason Faris ◽  
Reinhard Von Roemeling ◽  
Steven Angelides ◽  
Melissa Johnson

BackgroundVISTA (V-domain Ig suppressor of T cell activation) is a key negative immune checkpoint regulator, locking T cells in a quiescent state, unlike PD1 and CTLA4, which are expressed on activated T cells. Preclinically, VISTA monoclonal antibody treatment increased the number of tumor-specific T cells in the periphery, and enhanced the infiltration, proliferation and effector function of tumor-reactive T cells within the tumor microenvironment (TME). VISTA blockade alters the suppressive feature of the TME by decreasing the presence of monocytic myeloid-derived suppressor cells and increasing the presence of activated dendritic cells (DCs) within the TME leading to enhanced T cell mediated immunity. VISTA monoclonal antibody administration as a monotherapy has been shown to suppress the growth of both transplantable and inducible melanoma in preclinical models. CI-8993 is a first-in-class, fully human immunoglobulin (Ig) G1κ monoclonal antibody (mAb) against the VISTA ligand. Prior human clinical evaluation of CI-8993 demonstrated target-related clinical findings and pharmacodynamic activity at 0.15 mg/kg.MethodsThis phase 1 study is being conducted in the USA (NCT04475523) and is designed as a 3+3 dose escalation study beginning at 0.15 mg/kg. Patients with solid tumor malignancy (non-lymphoma) that is metastatic or unresectable and considered relapsed and/or refractory to prior therapy will be included, excluding prior CAR-T therapy or allogenic transplant. Patients will be treated with an initial step-dose of CI-8993 by IV infusion, followed by every 2 weeks of a full dose, until disease progression or toxicity. Efficacy, pharmacokinetics, pharmacodynamic and safety endpoints will be monitored and reported.ResultsN/AConclusionsN/AEthics ApprovalThe study was approved by Dartmouth-Hitchcock, Norris Cotton Cancer Center Ethics Board, approval number IRB00012031The study was approved Sarah Cannon Caner Research Institute, approval number IORG0000689


Blood ◽  
2021 ◽  
Vol 138 (Supplement 1) ◽  
pp. 1720-1720
Author(s):  
Yongxia Wu ◽  
Linlu Tian ◽  
Corey Mealer ◽  
Hee-Jin Choi ◽  
Xue-Zhong Yu

Abstract The Provirus Integration sites for Moloney murine leukemia virus (Pim) kinases are a highly conserved family of serine/threonine kinases. The Pim kinase family is composed of three different isoforms, Pim1, Pim2, and Pim3, which have been studied extensively in tumorigenesis and as a potential therapeutic target in various cancers. We previously reported an unexpected role of Pim2 in negatively regulates T-cell responses to alloantigen and tumor (JCI, 2015, PMID: 29781812). However, the mechanisms by which Pim2 modulates T-cell responses remain largely undefined. In the current study, using genetic Pim2-deficient mouse, we demonstrated a key role of Pim2 in regulating T-cell hemostatic and anti-tumor responses in aging, hematopoietic cell transplantation (HCT), and antigen-specific adoptive T-cell therapy (ACT). We observed that Pim2 was critical for T cells to retain quiescent in aged mice, as thymic Treg development was impaired while effector T-cell differentiation in lymphoid organs, including Tc1/Th1, Tc17/Th17 and follicular helper T cells, was increased in Pim2-deficient mice, but not in Pim1/Pim3-deficient mice. Furthermore, Pim2-deficient mice were capable to completely eradicate syngeneic breast cancer (NT2.5) growth (Figure A). During antigen specific anti-tumor response, adoptively transferred Pim2 -/- CD8 T cells showed enhanced ability for controlling established NT2.5 breast cancer and B16 melanoma (Figure B, C). Mechanistically, loss of Pim2 promoted G1 to S phase cell-cycle progression while reduced apoptosis in CD8 T cells. Pim2 -/- CD8 T cells exhibited elevated effector cytokine production while maintained higher levels of CD62L expression, leading to superior effector function, persistence and anti-tumor activity. Reduced differentiation of exhausted and suppressive subsets were observed in Pim2 -/- CD8 T cells after being adoptively transferred in tumor-bearing mice. In addition, Pim2 deficiency was associated with a higher metabolic potential, reflected by increased glycolysis and oxidative phosphorylation, which was at least partially attributed to a decreased level of autophagy in Pim2 -/- CD8 T cells. To further evaluate the clinical translation potential, we applied a Pim2-specific inhibitor (JP11646) and found that blocking Pim2 improved graft-versus-leukemia activity after autologous HCT and also enhanced CD8 T-cell mediated anti-melanoma effects after ACT in mice (Figure B, C). Furthermore, blocking Pim2 using JP11646 promoted human CD8 T-cell response during polyclonal stimulation and enhanced expansion, effector function and tumor killing ability of human melanoma antigen-specific CD8 T cells (data not shown) and CD19 CAR-T cells (Figure D). Our work demonstrated that Pim2 is a potent and distinct regulator of differentiation and maintenance of T effector cells through modulating metabolism and autophagy. Specifically target Pim2 can serve as a novel strategy for improving cancer immunotherapy. Figure 1 Figure 1. Disclosures No relevant conflicts of interest to declare.


2020 ◽  
Vol 38 (15_suppl) ◽  
pp. TPS9080-TPS9080
Author(s):  
Taofeek Kunle Owonikoko ◽  
Hossein Borghaei ◽  
Stéphane Champiat ◽  
Luis G. Paz-Ares ◽  
Ramaswamy Govindan ◽  
...  

TPS9080 Background: SCLC is an aggressive neuroendocrine tumor with poor prognosis and few treatment options. Delta-like ligand 3 (DLL3) is an inhibitory Notch ligand that is highly expressed on the surface of most SCLC tumors but minimally expressed in normal tissues. As such, DLL3 may be a promising therapeutic target. AMG 757 is an HLE BiTE immune therapy designed to redirect cytotoxic T cells to cancer cells by binding to DLL3 on cancer cells and CD3 on T cells, resulting in T cell activation and expansion and T cell-dependent killing of tumor cells. In addition to its direct antitumor effect, BiTE immune therapy can inflame the tumor microenvironment. Combining AMG 757 with a PD-1 pathway inhibitor may lead to increased antitumor activity by enabling sustained T cell-dependent killing of tumor cells. Methods: NCT03319940 is an open-label, ascending, multiple-dose, phase 1 study evaluating AMG 757 as monotherapy; the protocol was recently amended to also evaluate AMG 757 in combination with pembrolizumab. The study will include a dose exploration (monotherapy and combination) followed by a dose expansion (monotherapy). Key eligibility criteria: adult patients with relapsed/refractory SCLC whose disease progressed or recurred after at least 1 platinum-based chemotherapy regimen, ECOG performance status 0–2, at least 2 measurable lesions per modified RECIST 1.1, no untreated or symptomatic brain metastases, and adequate organ function. Primary objectives are to evaluate safety/tolerability and determine the maximum tolerated dose or recommended phase 2 dose of AMG 757 as monotherapy and in combination with pembrolizumab. Secondary objectives are to characterize pharmacokinetics and evaluate preliminary antitumor activity; exploratory objectives are to assess immunogenicity and changes in biomarkers in blood and tumor tissue. In the dose exploration phase, dose escalation/de-escalation decisions will be guided by a Bayesian logistic regression model; backfill enrollment at dose levels deemed safe and tolerable will be allowed. The study is open and recruiting patients. Clinical trial information: NCT03319940.


2020 ◽  
Vol 8 (Suppl 1) ◽  
pp. A1.2-A2 ◽  
Author(s):  
Sarina Piha-Paul ◽  
Johanna Bendell ◽  
Anthony Tolcher ◽  
Sara Hurvitz ◽  
Amita Patnaik ◽  
...  

BackgroundAnticalin® proteins are recombinantly engineered human proteins based on lipocalins. PRS-343 is a first-in-class bispecific antibody-Anticalin fusion protein targeting the oncogenic tumor antigen HER2 and the costimulatory immune receptor 4-1BB on T and other immune cells. Here, we report the results of a phase 1 single-agent dose escalation trial in patients with HER2+ solid tumors.MethodsPRS-343 has been evaluated in sequential dose cohorts from 0.0005 to 8 mg/kg i.v. Doses were administered Q3W and the 8 mg/kg dose was also given Q2W. An accelerated titration design was utilized for the initial dose escalation followed by a modified 3+3 design and the option to back-fill cohorts. Dose-limiting toxicities (DLTs) were reported during the first cycle of each schedule. The primary study objectives include the safety profile and RP2D of PRS-343. Secondary objectives include ORR and DCR, PD biomarker response and PK profile. PD response was assessed in tumor biopsies (CD8+ T cell IHC) pre- and post- PRS-343 treatment.Results51 patients (median age 61.2 years, 61% female, 82% caucasian, 57% with more than three lines of prior therapy) with a variety of solid tumor indications [gastric/GEJ (n=19); BC (n=12); gynecological cancer (n=6); CRC (n=5); BTC (n=4); UC (n=2); melanoma, pancreatic and salivary duct (n=1 each)] have been treated with PRS-343. Based on pharmacokinetic analyses and observed kinetics of the CD8+ T cell expansion post-treatment, the low end of the active dose range is considered 2.5 mg/kg. 19 patients treated at active dose levels before the data cut-off on 09-06-2019 were evaluable for response [DCR 58% (11% confirmed PR) as per RECIST 1.1]. At the active doses, we observed significant and pronounced post-treatment expansion of CD8+ T cells particularly in the tumor nests, consistent with the MoA of PRS-343, while there was no increase in the doses below 2.5 mg/kg. The post-treatment expansion of CD8+ T cells was more pronounced in patients with a confirmed PR or prolonged SD. PRS-343 was very well tolerated, with no SAEs reported. The most frequent TRAEs were fatigue (9%), chills (6%) and diarrhea (5%) of mild to moderate severity. None qualified as a DLT.ConclusionsPRS-343 is the first molecule of its kind to demonstrate encouraging evidence of safety and clinical benefit with a correlative PD effect in a heavily pre-treated population. These initial data suggest that PRS-343, the first 4-1BB bispecific to enter clinical development, merits further investigation in clinical trials.Trial RegistrationNCT03330561


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