Studies In Cynomolgus Monkeys Research Articles

Determination of starting dose of the T cell-redirecting bispecific antibody ERY974 targeting glypican-3 in first-in-human clinical trial

Currently, ERY974, a humanized IgG4 bispecific T cell-redirecting antibody recognizing glypican-3 and CD3, is in phase I clinical trials. After a first-in-human clinical trial of an anti-CD28 agonist monoclonal antibody resulting in severe life-threatening adverse events, the minimal anticipated biological effect level approach has been considered for determining the first-in-human dose of high-risk drugs. Accordingly, we aimed to determine the first-in-human dose of ERY974 using both the minimal anticipated biological effect level and no observed adverse effect level approaches. In the former, we used the 10% effective concentration value from a cytotoxicity assay using the huH-1 cell line with the highest sensitivity to ERY974 to calculate the first-in-human dose of 4.9 ng/kg, at which maximum drug concentration after 4 h of intravenous ERY974 infusion was equal to the 10% effective concentration value. To determine the no observed adverse effect level, we conducted a single-dose study in cynomolgus monkeys that were intravenously infused with ERY974 (0.1, 1, and 10 μg/kg). The lowest dose of 0.1 μg/kg was determined as the no observed adverse effect level, and the first-in-human dose of 3.2 ng/kg was calculated, considering body surface area and species difference. For the phase I clinical trial, we selected 3.0 ng/kg as a starting dose, which was lower than the first-in-human dose calculated from both the no observed adverse effect level and minimal anticipated biological effect level. Combining these two methods to determine the first-in-human dose of strong immune modulators such as T cell-redirecting antibodies would be a suitable approach from safety and efficacy perspectives.Clinical trial registration: JapicCTI-194805/NCT05022927.

Lymphocyte subsets and immunoglobulin levels in peripheral blood from cynomolgus monkeys (Macaca fascicularis) of different age groups.

Immunotoxicity assessment is an important part of non-clinical safety evaluation of biotechnology-derived pharmaceuticals. The reference ranges of evaluated parameters, which depend on the sex, age and geographical origin of animals, play a significant role in interpreting the study results. The aim of this study was to determine the reference ranges of parameters commonly used for non-clinical immunotoxicity studies in cynomolgus monkeys (Macaca fascicularis) of different ages. The percentages of CD3+, CD4+, CD8+, CD20+, CD16/56+ lymphocytes, and the serum levels of immunoglobulins A, M, G and E in clinically healthy cynomolgus monkeys of both sexes and different ages (37-104 months) were analysed. The lymphocyte subsets were assessed by flow cytometry and serum immunoglobulin levels were determined by enzyme-linked immunosorbent assay. Statistical analysis showed a weak rank correlation of CD3+, CD20+ lymphocyte levels with the ages of female and male cynomolgus monkeys, and no significant correlation with age for the combined data of both sexes. The serum levels of immunoglobulins A, M, G and E did not have a significant rank correlation with age for the combined data of both sexes, whereas IgA levels in females and IgG levels in males were weakly correlated with age. Overall, these results justify the use of animals aged three to eight years for non-clinical immunotoxicity evaluation of biotechnology-derived pharmaceuticals. It is important to avoid the formation of animal groups with extreme ages (three years or eight years) in one group during randomization.

Abstract CT209: A first-in-human phase 1 trial of IO-108, an antagonist antibody targeting LILRB2 (ILT4), as monotherapy and in combination with pembrolizumab in adult patients with advanced relapsed or refractory solid tumors (NCT05054348)

Abstract Cancer immunotherapy has entered the mainstream with approval of T-cell checkpoint inhibitors. However, most patients with advanced solid tumors do not derive benefits, or relapse after T-cell checkpoint blockade. Myeloid checkpoint inhibition is a new approach to cancer immunotherapy. LILRB2 is primarily expressed by myeloid cells and its expression in tumors is associated with high macrophage infiltration. Several LILRB2 ligands (HLA-G, ANGPTL2, and SEMA4A) are known to contribute to the immune suppressive microenvironment of solid tumors. Blockade of the LILRB2 pathway has the potential to reactivate or enhance anti-tumor T cell immune responses. IO-108 is a IgG4 monoclonal antibody that specifically binds LILRB2 to block ligands interaction and activation of LILRB2. In vitro, IO-108 treatment of primary immune cells results increased pro-inflammatory responses and an enhanced antigen presenting cell phenotypes. A Good Laboratory Practice repeat-dose, 15-day toxicology study in Cynomolgus monkeys at 0 (control), 1, 10, or 100 mg/kg/dose administered intravenously once weekly for a total of 3 doses showed that IO-108 was well-tolerated at all dose levels, with only non-statistically significant reduction of thyroid glands weight. No-observed-adverse-effect-level (NOAEL) of 100 mg/kg provides a sufficient safety margin for the IO-108 starting dose of 60 mg, which was derived using a MABEL (minimum anticipated biological effect level) approach. This clinical trial is a first-in-human, Phase 1, multicenter, open-label, dose-escalation, safety, pharmacokinetic (PK), and pharmacodynamic evaluation of intravenously administered IO-108, both as monotherapy and in combination with pembrolizumab, in adult patients with solid tumors that have failed standard of care therapies (NCT05054348). It is estimated that up to 36 patients will be enrolled in the study. IO-108 will be administered every 21 days, with a dose-limiting toxicity (DLT) evaluation period of 21 days. Patients will be enrolled into sequential cohorts and treated with increasing doses of IO-108 using mTPI (modified Toxicity Probability Interval) method. Safety, PK, and clinical activity will be evaluated on an ongoing basis. The primary objective of the study is to assess safety and tolerability at increasing dose levels of IO-108 in successive cohorts of adult patients (treated with or without with pembrolizumab) with advanced relapsed or refractory solid tumors, to estimate the maximal tolerated dose (MTD) or maximum administered dose (MAD) and select the recommended phase 2 dose (RP2D). Secondary objectives include characterizing PK, immunogenicity, and preliminary anti-tumor activity. Biomarker evaluation will include changes in myeloid cell markers and T-cells, LILRB2 expression level and receptor occupancy. Statistical analyses will be primarily descriptive in nature. Tabulations will be produced for appropriate disposition, demographic, baseline disease characteristics, safety, PK, pharmacodynamic, and clinical activity parameters. Response to treatment as assessed by RECIST v1.1 will be tabulated. To date, five patients have been dosed without DLT. Citation Format: John Powderly, Manish Patel, Paul Woodard, Luke Chung, Hongyu Tian, Elizabeth Wieland, Kyu Hong, Maria Jose Costa, X. Charlene Liao, Matthew Taylor. A first-in-human phase 1 trial of IO-108, an antagonist antibody targeting LILRB2 (ILT4), as monotherapy and in combination with pembrolizumab in adult patients with advanced relapsed or refractory solid tumors (NCT05054348) [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 CT209.

Abstract 3510: SOT201 is a novel targeted IL-15Rbg agonist to alleviate PD-1-mediated immune cell suppression and potentiate anti-tumor efficacy

Abstract SOT201 is a novel immunocytokine consisting of a monoclonal humanized, Fc silenced antibody against PD-1 fused to a covalent RLI-15 complex of a human IL-15 mutein linked to the high-affinity binding site of the IL-15Rα, the sushi+ domain. SOT201 is developed for immunotherapeutic treatment of various types of cancers. The activity of SOT201 is based on spatiotemporal reinvigorating of anti-tumor immune responses by disrupting co-inhibitory T-cell signaling by blocking PD-1 and synergistically activating adaptive as well as innate immunity by IL-15-mediated signaling via the IL-2/IL-15βγ receptor on T cells, NK, NKT, and γδ T cells. SOT201 showed a superior potentiation of T cell stimulation over pembrolizumab in mixed lymphocyte reaction in vitro. Studies in cynomolgus monkeys showed that decreased affinity of IL-15 mutein in SOT201 for its IL-15Rβγ is well optimized to ensure favorable pharmacokinetic properties while inducing strong CD8+ T cell and NK cell activation and expansion. Synergistic action on CD8+ T cell activation of both anti-PD-1 and RLI-15 moieties was confirmed using mouse surrogate SOT201 molecules in vivo. Strong anti-tumor efficacy after SOT201 treatment was achieved in a human PD-1 transgenic mouse model implanted with the MC38-hPD-L1 cell line. These data represent a promising therapeutic candidate molecule leveraging the synergistic concerted action of anti-PD-1 blockage and simultaneous immune cell activation directed preferentially to the high PD-1+ T cell tumor environment. The therapeutic potential of SOT201 is currently being prepared for evaluation in a Phase I clinical study in metastatic advanced cancer patients as well as for PD-1 resistant/refractory patients as our clinical stage IL-2/IL-15Rβγ agonist SOT101 already showed a clinical benefit in these patients in its ongoing Phase I study. Citation Format: Irena Adkins, Zuzana Antosova, Klara Danova, Kamila Hladikova, Katerina Augustynkova, Katerina Sajnerova, Nada Podzimkova, Pavel Marasek, Guy de Martynoff, David Bechard, Ulrich Moebius, Radek Spisek. SOT201 is a novel targeted IL-15Rbg agonist to alleviate PD-1-mediated immune cell suppression and potentiate anti-tumor efficacy [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 3510.

Abstract 2869: ADG138, a novel HER2×CD3 POWERbody™ integrating bispecific TCE with precision masking to control cytokine release syndrome and on-target off-tumor toxicity for single agent and combination therapies in HER2-expressing solid tumors

Abstract Bispecific T-cell engagers (TCEs) have shown therapeutic promise in treating hematologic cancers. However, their utility in treating solid tumors has yet to be effectively demonstrated due to on-target off-tumor toxicity and systemic cytokine release syndrome (CRS). To explore the full potential of TCEs as a powerful modality of immunotherapy for solid tumors, we developed ADG138, a novel HER2×CD3 POWERbody™ TCE by applying our SAFEbody® precision masking technology to double mask the binding interfaces in both ADG138 arms using covalently linked designer peptides in order to limit on-target off-tumor toxicities in normal tissues and to avert systemic CRS. In the tumor microenvironment (TME), the double masked ADG138 prodrug can be activated for concomitant in situ binding to the targeted cancer cells by the HER2 arm and to T cells by the CD3 arm to selectively enhance T cell responses against tumor cells specifically. Nonclinical studies demonstrated that when activated, ADG138 was highly potent in inducing T cell mediated cytotoxicity of both high and low HER2-expressing tumor cells in vitro, whereas in its double masked prodrug form ADG138 exhibited high masking efficiency with greatly reduced HER2 binding, T cell activation, and T cell mediated cytotoxicity. In in vivo human PBMC-engrafted tumor xenograft models, ADG138 induced robust tumor regression of both high and low HER2-expressing tumors in mice. Furthermore, combination of ADG138 with our species cross-reactive immuno-oncology therapeutics mediated strong synergistic antitumor activities in HER2 positive syngeneic solid tumor models in human CD3e knock-in mice. The double masked ADG138 prodrug also exhibited excellent safety profiles and normal pharmacokinetics in exploratory toxicology studies in cynomolgus monkeys, achieving over a 300-fold higher tolerated dose in striking contrast with its parental TCE that lacks masking. These nonclinical studies demonstrated that ADG138, a novel double masked HER2×CD3 POWERbody TCE, exhibited an impressively high therapeutic index relative to its parental non-masked TCE in HER2 high and low expressing solid tumors. This provides strong support for advancing the ADG138 prodrug into clinical development for treating HER2-expressing solid tumors as a single agent and in combination with other immune stimulatory agents. Citation Format: Guizhong Liu, Yan Li, Zhengxi Dai, Jiagui Qu, Jianfeng Shi, Qi Zhao, Linhai Qu, Aaron N. Nguyen, Songmao Zheng, Jiangchun Xu, Felix Du, Peter Luo. ADG138, a novel HER2×CD3 POWERbody™ integrating bispecific TCE with precision masking to control cytokine release syndrome and on-target off-tumor toxicity for single agent and combination therapies in HER2-expressing solid tumors [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 2869.

Abstract 5202: AMG 794, a Claudin 6-targeted half-life extended (HLE) bispecific T cell engager (BITE®) molecule for non-small cell lung cancer and epithelial ovarian cancer

Abstract AMG 794 is a half-life extended BiTE® immune therapy targeting the oncofetal antigen Claudin 6 (CLDN6). AMG 794 redirects T cells to kill CLDN6-expressing tumor cells and is being developed for the treatment of non-small cell lung cancer (NSCLC) and epithelial ovarian cancer (EOC). CLDN6 is a compelling tumor antigen that is expressed during embryonic and fetal development, transcriptionally silenced in adult tissues, and re-expressed on the surface of NSCLC and EOC cells. By immunohistochemistry, CLDN6 staining of the cell membrane was observed in 27% of non-squamous NSCLC (n = 63) and 69% of EOC (n = 92) samples, the majority of which were of the high-grade serous ovarian cancer subtype. Expression of CLDN6 protein was not detected in most normal adult tissues, with rare CLDN6 immunostaining limited to individual cells in the pituitary, pancreas, small intestine, kidney, and female reproductive organs. AMG 794 is a fully human BiTE® molecule that binds both human and cynomolgus monkey CLDN6 and CD3. AMG 794 binds human CLDN6 and CD3 with equilibrium dissociation constant (KD) of 13 nM and 36 nM, respectively. In vitro, AMG 794 redirects human T cells to kill CLDN6-expressing cancer cells with a half-maximal lysis concentration (EC50) of 2.6 ± 1.1 pM to 127.4 ± 53.4 pM. Consistent with the mechanism of action of BiTE® immune therapy, AMG 794 induces T cell activation and transient production of cytokines in co-cultures of T cells and CLDN6-expressing tumor cells. Remarkably, AMG 794 binding and cytotoxic activity is selective for CLDN6 over other claudin family proteins, despite high homology in the extracellular loops with CLDN9. Weekly dosing of AMG 794 significantly inhibited the growth of established lung and ovarian xenograft tumors in immunocompromised mice injected with human T cells. Anti-tumor activity was associated with an increase in tumor-infiltrating T cells. AMG 794 was well tolerated in a one-month repeat-dose toxicology study in cynomolgus monkey, with evidence for target engagement. The potent, selective activity of AMG 794 for CLDN6-expressing NSCLC and EOC cells, together with an acceptable nonclinical safety profile, supported the advancement of AMG 794 into clinical development. A first-in-human study to explore the safety, tolerability, pharmacokinetics, and anti-tumor activity of AMG 794 in patients with CLDN6-positive advanced/metastatic non-squamous NSCLC or EOC will be enrolling patients in March 2022. Citation Format: Elizabeth Pham, Anja Henn, Beate Sable, Joachim Wahl, Kip Conner, Katja Matthes, Shivani Gupta, Rodolfo Yabut, Famke Aeffner, Kristin Lewis Wilson, Jonas Anlahr, Christoph Dahlhoff, Vijay Kale, Matthias Friedrich, Tobias Raum, Peter Kufer, Angela Coxon, Sabine Stienen, Julie M. Bailis. AMG 794, a Claudin 6-targeted half-life extended (HLE) bispecific T cell engager (BITE®) molecule for non-small cell lung cancer and epithelial ovarian cancer [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 5202.

Abstract 5551: QLS31905, an anti-claudin 18.2/CD3 bispecific antibody for claudin 18.2-positive gastric cancer

Abstract Claudin 18.2 is a quadruple transmembrane protein with a complex structure and highly specific expression in gastric and pancreatic cancers. It is suggested that claudin 18.2 is an ideal target for cancer therapy. Anti-claudin 18.2 antibody IMAB362 has achieved remarkable success in the latest clinical trials. Multiple anti-claudin 18.2 monoclonal antibodies and chimeric antigen receptor T-cell therapy targeting claudin 18.2 have also entered phase I clinical trials. CD3 is a receptor that is present on the surface of T cells and is involved in the antigen recognition by T cells as well as in signal transduction. Anti-claudin 18.2/CD3 bispecific antibody can recruit T cells to tumor sites, activating T cells to kill tumor cells with high claudin 18.2 expression to improve efficacy. Here, we describe a new T cell-redirecting antibody (QLS31905) that is bispecific for claudin 18.2 and CD3. QLS31905 showed a potent in vitro cytotoxic activity against claudin 18.2-positive engineered cell lines HEK293-hCLDN18.2 and NCI-N87 CLDN18.2 as well as superior in vivo efficacy in humanized NCI-N87 CLDN18.2 model. Furthermore, QLS31905 was safe and well tolerated in a 4-week repeated dose (up to 10 mg/kg) toxicity study in cynomolgus monkeys. In vitro cytokine release was lower in the QLS31905 group than that in the AMG 910 (another anti-claudin18.2/CD3 bispecific antibody) group. Overall, these data suggested that QLS31905 has similar efficacy to AMG 910 and is safer. QLS31905 may be an effective and clinically valuable treatment for patients with claudin 18.2-positive gastric cancer. Citation Format: Jiahua Jiang, Meimei Si, Xiao Luo, Yun Wu, Yongjun Li, Xiaodan Yan. QLS31905, an anti-claudin 18.2/CD3 bispecific antibody for claudin 18.2-positive gastric cancer [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 5551.

Abstract 4257: ADG153-G1, a highly differentiated anti-CD47 IgG1 SAFEbody, demonstrates potent in vivo anti-tumor activities with enhanced ADCC/ADCP effects and significantly reduced RBC-related and antigen sink liabilities

Abstract Anti-CD47 antibodies of the IgG4 isotype have shown promising activities in clinical trials for hematologic malignancies, mainly in the combination setting. To overcome the fundamental challenge of developing an anti-CD47 antibody of an active Fc isotype for strong anti-tumor activities without the safety (e.g., anemia) and pharmacokinetic (e.g., antigen sink) liabilities, we set out to design anti-CD47 antibodies of active isotypes that allow us to decouple efficacy from safety and PK liabilities. Our NEObody࣪ technology enables us first to identify an anti-CD47 antibody targeting a novel epitope on CD47. Next, our SAFEbody® technology for precision masking enables us to mask the CD47 binding sites to create the masked antibody in active IgG1 isotype called ADG153-G1 SAFEbody, which can be conditionally activated to bind and inhibit CD47 on tumor cells for potent tumor killing with much improved safety and pharmacokinetic profiles. In vitro studies showed that the activated ADG153-G1 SAFEbody blocked CD47 binding to SIRPα, bound to the CD47 protein, CD47+ tumor cell lines, and human RBCs, and induced strong ADCC/ADCP activities. In contrast, the unactivated ADG153-G1 SAFEbody demonstrated high masking efficiency (ME) with significantly reduced activities (>110-1300× ME) in the same assays. While anti-CD47 antibodies such as the Hu5F9 analog caused in vitro human RBC hemagglutination, the ADG153-G1 SAFEbody in activated and unactivated forms did not show this effect at comparable concentrations. Consistent with its enhanced ADCC/ADCP potential in IgG1 isotype, in the CD47+ Raji tumor model in SCID mice (with functional NK cells and macrophages), the unmasked ADG153-G1 and masked SAFEbody demonstrated better anti-tumor activities than their IgG4 unmasked and masked SAFEbody counterparts. In exploratory single-dose toxicology studies in cynomolgus monkeys, the ADG153-G1 SAFEbody showed significantly less reduction than the Hu5F9 analog in RBCs and hemoglobin. The Hu5F9 analog at 10 mg/kg caused an ~49% maximum decrease in RBCs, while the ADG153-G1 SAFEbody at 10 and 30 mg/kg showed only 8% and 40% maximum reductions, respectively. Consistent with a reduced antigen sink effect due to lower RBC binding, the ADG153-G1 SAFEbody had more favorable pharmacokinetic properties than the Hu5F9 analog (~8× longer t1/2 and ~5× higher AUC) at 10 mg/kg. Taken together, these results indicate that the ADG153-G1 SAFEbody is a differentiated anti-CD47 IgG1 antibody prodrug with strong ADCC/ADCP potential and significantly reduced anemia-related and antigen sink liabilities, supporting its advancement into clinical development. Citation Format: Bin Cai, Aaron N. Nguyen, Songmao Zheng, Jianfeng Shi, Guizhong Liu, Yan Li, Felix Du, Peter Luo, Jiangchun Xu. ADG153-G1, a highly differentiated anti-CD47 IgG1 SAFEbody, demonstrates potent in vivo anti-tumor activities with enhanced ADCC/ADCP effects and significantly reduced RBC-related and antigen sink liabilities [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 4257.

A novel next‐generation FVIIIa mimetic, Mim8, has a favorable safety profile and displays potent pharmacodynamic effects: Results from safety studies in cynomolgus monkeys

BackgroundMim8 is a novel, next‐generation factor VIIIa mimetic in development for subcutaneous prophylactic treatment of patients with hemophilia A with and without inhibitors. In vitro and in vivo models indicate that Mim8 has a distinct hemostatic potential. ObjectivesTo test the nonclinical safety and pharmacodynamics of Mim8. MethodsThe Mim8 nonclinical safety program in cynomolgus monkeys consisted of three studies of 4–26 weeks in duration with Mim8 doses ranging from 0.3–60 mg/kg/week intravenously or subcutaneously. After sacrifice, macroscopic and microscopic pathological examinations were performed. ResultsMim8 was well tolerated with no noteworthy clinical observations. No signs of excessive coagulation or pathological macroscopic or microscopic findings were observed at doses 0.3–3 mg/kg/week subcutaneous. Thrombosis‐related findings were detected during histopathological examination in a small proportion of animals (16%) receiving doses ranging 6–20 mg/kg/week. Dose‐dependent increases in factor X (FX) and factor IX (FIX) concentrations were observed. Shortening of activated partial thromboplastin time (APTT) and increased thrombin generation under ex vivo hemophilia A‐like conditions were observed at all Mim8 dose levels. ConclusionsThrombosis‐related findings observed at doses above 6 mg/kg/week Mim8 may have been exaggerated pharmacological reactions to a procoagulant compound in normocoagulant animals. Increases in FX and FIX concentrations could be because of a half‐life prolongation due to binding to Mim8, but were limited at clinically relevant exposure levels. Subcutaneous administration of up to 3 mg/kg/week (several fold greater than expected clinical exposure) for 26 weeks resulted in relevant pharmacodynamic effects, observed in thrombin generation and APTT, with no signs of thrombi or excessive coagulation activation.

Heat pre-treatment can abolish anti-drug antibody interference in ligand binding pharmacokinetic assays

Anti-drug antibodies (ADAs) can interfere with ligand binding assays (LBAs) by binding to epitopes recognized by the assay antibodies or by preventing assay antibody binding through steric hindrance. This can lead to underestimation of total drug concentration in pharmacokinetic (PK) samples which can confound decisions during drug development. We hypothesized that ADA interference in LBAs can be removed by sample heat pre-treatment. We heat pre-treated ADA-spiked samples by incubating them in a shallow water bath at 56–100 °C for 5–30 min prior to measuring the samples by a traditional electrochemiluminescence (ECL) assay. Heat pre-treatment at minimum 85 °C for 5 min completely removed the ADA interference. We then compared the analyte concentrations measured with and without heat pre-treatment of blood samples from toxicology studies performed for two different analytes in 60 cynomolgus monkeys and 29 minipigs, respectively. The overall difference in measured concentration of ADA-positive samples was significantly different from the overall difference in measured concentration of ADA-negative samples. For the cynomolgus monkey study samples, the ADA titer was determined, and the difference in measured concentration, when comparing heat pre-treatment to no heat pre-treatment, was significantly correlated to the ADA titer. Additionally, heat pre-treatment removed parallelism issues observed in a subset of study samples. Our data suggest that sample heat pre-treatment can abolish ADA interference in an LBA and could serve as a tool to assess the degree of ADA interference and the total drug concentration in a PK sample. Of note, before utilizing this strategy on a new analyte, it is necessary to assess whether heat pre-treatment negatively affects the detection of the analyte by the assay antibodies.

Preclinical characterization of the novel anti-SIRPα antibody BR105 that targets the myeloid immune checkpoint

BackgroundThe CD47-SIRPα pathway acts as an important myeloid cell immune checkpoint and targeting the CD47/SIRPα axis represents a promising strategy to promote antitumor immunity. Several CD47-targeting agents show encouraging early...

Structure dependence and species sensitivity of in vivo hepatobiliary toxicity with lysophosphatidic acid receptor 1 (LPA1) antagonists

BMS-986020, BMS-986234 and BMS-986278, are three lysophosphatidic acid receptor 1 (LPA1) antagonists that were or are being investigated for treatment of idiopathic pulmonary fibrosis (IPF). Hepatobiliary toxicity (elevated serum AST, ALT, and ALP, plasma bile acids [BAs], and cholecystitis) was observed in a Phase 2 clinical trial with BMS-986020, and development was discontinued. In dogs and rats, the species used for the pivotal toxicology studies, there was no evidence of hepatobiliary toxicity in the dog while findings in the rat were limited to increased plasma BAs levels (6.1× control), ALT (2.9×) and bilirubin (3.4×) with no histopathologic correlates. Since neither rats nor dogs predicted clinical toxicity, follow-up studies in cynomolgus monkeys revealed hepatobiliary toxicity that included increased ALT (2.0× control) and GLDH (4.9×), bile duct hyperplasia, cholangitis, cholestasis, and cholecystitis at clinically relevant BMS-986020 exposures with no changes in plasma or liver BAs. This confirmed monkey as a relevant species for identifying hepatobiliary toxicity with BMS-986020. In order to assess whether the toxicity was compound-specific or related to LPA1 antagonism, two structurally distinct LPA1 antagonists (BMS-986234 and BMS-986278), were evaluated in rat and monkey. There were no clinical or anatomic pathology changes indicative of hepatobiliary toxicity. Mixed effects on plasma BAs in both rat and monkey has made this biomarker not a useful predictor of the hepatobiliary toxicity. In conclusion, the nonclinical data indicate the hepatobiliary toxicity observed clinically and in monkeys administered BMS-986020 is compound specific and not mediated via antagonism of LPA1.

Treating Iron Overload Disorders with a Novel Therapeutic Antibody Targeting TMPRSS6

Iron is an essential element for almost all living organisms as it participates in a wide variety of metabolic processes. Disorders of iron metabolism are among the most prevalent human diseases, ranging from anemia to hemochromatosis. Excessive iron accumulations in major organs of iron overload patients can lead to high mortality. Hepcidin, a HAMP-encoded liver hormone, is the master regulator of iron homeostasis. By binding to the sole iron exporter ferroportin and causing internalization and degradation of the complex, hepcidin inhibits cellular iron efflux, thereby lowers plasma iron levels. Inappropriately suppressed/low hepcidin production is central to iron overload. Transmembrane protease serine-6 (TMPRSS6), a type II transmembrane serine protease primarily expressed in liver, downregulates hepcidin expression through BMP-SMAD pathway. TMPRSS6 deficiencies have been shown to cause hepcidin overexpression in both TMPRSS6-mutant mice and in patients with iron-refractory iron deficiency anemia (IRIDA). Therefore, TMPRSS6 is a viable therapeutic target for iron overload disorders.Here we report the generation of an anti-TMPRSS6 antibody through a hybridoma campaign using a DNA-based immunization approach, followed by humanization and sequence optimization. Lead antibody, hzMWTx-003 selectively binds human TMPRSS6 with low nanomolar affinity (KD: 7.6nM), and is cross-reactive to rodent (mouse and rat) and monkey (cynomolgus and rhesus) TMPRSS6. Single-dose injection of hzMWTx-003 was able to significantly elevate serum hepcidin and liver HAMP RNA levels in wildtype mice, resulting in significantly reduced serum iron level. The Hbb th3/+ mouse model of β-thalassemia, like its human counterpart, is characterized by iron overload, ineffective erythropoiesis and splenomegaly. Treatment of Hbb th3/+mice with MWTx-003 effectively increased hepcidin expression at both protein and RNA levels, leading to significantly reduced serum iron and liver non-heme iron content. MWTx-003 also dramatically improved anemia and ineffective erythropoiesis, and alleviated splenomegaly in these mice.CMC development of hzMWTx-003 confirms outstanding biophysical properties. Preliminary studies in cynomolgus monkey using GLP-grade material demonstrated good pharmacokinetics of hzMWTx-003 and expected pharmacodynamic response where reduction of serum iron could be sustained for 21 days after single dose administration. A single dose toxicology study in cynomolgus monkey revealed no safety concerns, and no production of anti-idiotype antibodies was detected. In summary, anti-TMPRSS6 antibody MWTx-003 represents a promising therapy for iron overload disorders such as β-thalassemia, and potentially other diseases where iron restriction is beneficial. DisclosuresChen: Mabwell Therapeutics Inc: Current Employment. Wang: Mabwell Therapeutics Inc: Current Employment. Zheng: Mabwell (Shanghai) Bioscience Co. Ltd: Current Employment. Huang: Mabwell Therapeutics Inc: Current Employment. Mao: Mabwell (Shanghai) Bioscience Co. Ltd.: Current Employment. Ouyang: Mabwell (Shanghai) Bioscience Co. Ltd.: Current Employment. Du: Mabwell Therapeutics Inc: Current Employment.

ADG152, a Novel CD20xCD3 T Cell Engager Prodrug with Enhanced Therapeutic Index, Demonstrates Strong Anti-Tumor Activity with Improved Safety

Recent clinical data illustrate the effectiveness of CD20xCD3 T cell engagers (TCEs) that redirect the patient's endogenous T cells to eliminate CD20-positive tumor cells. While several of these products have demonstrated promising clinical activities in B-cell malignancies, their potential therapeutic utility is limited by cytokine release syndrome (CRS), even after strategies such as step-up dosing are implemented.ADG152 is a novel CD20xCD3 TCE prodrug engineered using Adagene's SAFEbody technology to minimize or eliminate CRS and on-target/off-tumor toxicities. The anti-CD20 arm of ADG152 has been engineered for enhanced binding to CD20 compared to other clinical stage or approved antibodies, while its anti-CD3 arm has modulated affinity for CD3 and is also masked by a conditionally activable peptide. In normal tissues and in circulation, the masking moiety on the anti-CD3 arm can function to block the binding of ADG152 to T cells; however, in an activable condition such as the tumor microenvironment where protease activity has been reported to be elevated, the masked antibody can be activated, enabling the activated ADG152 to simultaneously engage T cells and neighboring CD20-expressing tumor cells.In vitro studies showed that ADG152 has enhanced binding to human B cells and CD20-positive Raji tumor cells compared with the benchmark CD20xCD3 TCE plamotamab. On the other hand, ADG152 has significantly reduced binding to the human CD3 δ/ε protein dimer and no binding to human CD3+, CD4+, and CD8+ T cells isolated from PBMCs of normal human donors. Consistent with these results, ADG152 shows significantly decreased ability (more than 100-fold) compared with the benchmark and the unmasked parental molecule to activate CD8+ T cells and to induce T cell-mediated killing in the presence of tumor cells in vitro.ADG152 demonstrated strong anti-tumor effects in vivo. In a human PBMC-engrafted Raji xenograft mouse tumor model, dosing with ADG152 resulted in almost complete tumor growth inhibition at 1.5 mg/kg. In exploratory toxicology studies in cynomolgus monkeys, ADG152 resulted in significantly less cytokine release in monkey blood compared with benchmark, giving ~100-fold safety margin for ADG152 for cytokine induction (Figure). In addition, ADG152 was as effective as the benchmark at inducing B cell depletion from peripheral blood of cynomolgus monkeys. In summary, the preclinical characterization of ADG152 demonstrates that our SAFEbody platform can be used to engineer safe and potent bispecific T cell engagers with increased therapeutic index by allowing for strong anti-tumor activities in mice at doses with minimal cytokine release in monkeys, thereby supporting its advancement to clinical development either as a single agent or in combination with other therapies for the treatment of CD20-expressing B cell malignancies. [Display omitted] DisclosuresCai: Adagene Inc.: Current Employment, Current equity holder in publicly-traded company. Nguyen: Sparcbio, LLC: Ended employment in the past 24 months; Adagene Inc.: Current Employment, Current equity holder in publicly-traded company. Zheng: Janssen Pharmaceuticals: Ended employment in the past 24 months; Adagene Inc.: Current Employment, Current equity holder in publicly-traded company. Shi: Adagene Inc.: Current Employment, Current equity holder in publicly-traded company. Liu: Adagene Inc.: Current Employment, Current equity holder in publicly-traded company. Li: Adagene Inc.: Current Employment, Current equity holder in publicly-traded company. Du: Adagene Inc.: Current Employment, Current equity holder in publicly-traded company. Frankel: Cytovia Therapeutics: Current Employment, Current holder of individual stocks in a privately-held company; Adagene Inc.: Consultancy, Current equity holder in publicly-traded company; Bristol Myers Squibb: Current equity holder in publicly-traded company, Ended employment in the past 24 months; IMV: Consultancy; Precision Biosciences: Current equity holder in publicly-traded company, Membership on an entity's Board of Directors or advisory committees; Sutro: Membership on an entity's Board of Directors or advisory committees; Immunai: Consultancy, Membership on an entity's Board of Directors or advisory committees; Minerva Therapeutics: Consultancy, Current holder of stock options in a privately-held company, Membership on an entity's Board of Directors or advisory committees; Myeloid Therapeutics: Consultancy; RAPT Therapeutics: Consultancy; Syros: Consultancy. Luo: Adagene Inc.: Current Employment, Current equity holder in publicly-traded company, Membership on an entity's Board of Directors or advisory committees. Xu: Bristol Myers Squibb: Current equity holder in publicly-traded company, Ended employment in the past 24 months; Adagene Inc.: Current Employment, Current equity holder in publicly-traded company.

ADG153, an Anti-CD47 Monoclonal Antibody Prodrug, Has Strong In Vivo Anti-Tumor Activity, Minimal RBC-Related and Antigen Sink Liabilities, and Extended Half Life in Comparison with Benchmark Clinical Antibodies of the Same IgG Subclass

Binding of the CD47 membrane protein, overexpressed on many tumor types, to the SIRPα inhibitory receptor on myeloid cells results in the inhibition of the activation of macrophages and other phagocytes against tumors. Therapies targeting the CD47/SIRPα axis have shown success in various preclinical models and are now in clinical trials for both solid and hematologic malignancies. Although anti-CD47 therapies have demonstrated promising clinical activities, the expression of CD47 on many different normal human cell types, including red blood cells (RBCs), serves as a large antigen sink for anti-CD47 antibodies. Blocking CD47 on RBCs, such as by magrolimab (Hu5F9), has led to transient anemia, requiring step-up dosing in the clinic.To circumvent these challenges, we developed ADG153, a fully human anti-CD47 SAFEbody masked by conditionally activable peptides. In normal tissues, the SAFEbody masking moiety can function to block ADG153 from binding to CD47; however, in an activable condition such as the tumor microenvironment where protease activity has been reported to be elevated, the masked antibody can be activated, enabling the activated ADG153 antibody to bind to and inhibit CD47 function on tumor cells.For head-to-head comparisons, in vitro studies were performed to compare the activity of Hu5F9 and unmasked ADG153 parental antibody of the IgG4 isotype. Both antibodies (1) blocked human SIRPα from binding to human CD47, (2) had similar potencies for binding to human CD47 protein, CD47-positive tumor cell lines, and human RBCs, and (3) induced macrophage phagocytosis. In contrast, the masked ADG153 SAFEbody demonstrated significantly reduced activities (>450-fold) in the same in vitro assays, showing strong masking efficiencies. Unlike Hu5F9, both the ADG153 parental and SAFEbody molecules did not cause in vitro human RBC hemagglutination.Although the ADG153 SAFEbody had significantly reduced binding to CD47 in vitro as expected, it demonstrated strong anti-tumor activity in in vivo mouse tumor models. In both the disseminated and subcutaneous CD47-positive Raji tumor models, the ADG153 SAFEbody of the IgG4 isotype showed similar anti-tumor activities to Hu5F9. However, in exploratory toxicology studies in cynomolgus monkeys, the ADG153 SAFEbody showed significantly less decreases than Hu5F9 in RBCs, hemoglobin, and hematocrit. Hu5F9 at 10 mg/kg caused ~49% maximum decrease in RBCs, while ADG153 SAFEbody at 60 mg/kg showed ~23% maximum decrease in RBCs (Panel A). Pharmacokinetic (PK) studies of single intravenous dose ADG153 SAFEbody compared to Hu5F9 in monkeys demonstrated ~8-fold longer apparent half-life and ~9-fold higher Area Under the Curve at 10 mg/kg (Panel B). Collectively, ADG153 SAFEbody is a differentiated anti-CD47 antibody that has strong in vivo anti-tumor activity with reduced RBC-related and antigen sink liabilities and favorable PK properties. This preclinical profile with an enhanced therapeutic index provides a strong rationale for advancing ADG153 SAFEbody into clinical development. [Display omitted] DisclosuresCai: Adagene Inc.: Current Employment, Current equity holder in publicly-traded company. Nguyen: Adagene Inc.: Current Employment, Current equity holder in publicly-traded company; Sparcbio, LLC: Ended employment in the past 24 months. Zheng: Adagene Inc.: Current Employment, Current equity holder in publicly-traded company; Janssen Pharmaceuticals: Ended employment in the past 24 months. Shi: Adagene Inc.: Current Employment, Current equity holder in publicly-traded company. Liu: Adagene Inc.: Current Employment, Current equity holder in publicly-traded company. Li: Adagene Inc.: Current Employment, Current equity holder in publicly-traded company. Du: Adagene Inc.: Current Employment, Current equity holder in publicly-traded company. Luo: Adagene Inc.: Current Employment, Current equity holder in publicly-traded company, Membership on an entity's Board of Directors or advisory committees. Xu: Adagene Inc.: Current Employment, Current equity holder in publicly-traded company; Bristol Myers Squibb: Current equity holder in publicly-traded company, Ended employment in the past 24 months.

Discovery and Preclinical Characterization of CC-95251, an Anti-SIRPα Antibody That Enhances Macrophage-Mediated Phagocytosis of Non-Hodgkin Lymphoma (NHL) Cells When Combined with Rituximab

Introduction: The transmembrane protein CD47 is ubiquitously expressed on normal cells and often overexpressed on cancer cells, including NHL. Binding of CD47 to signal regulatory protein-α (SIRPα) on macrophages induces an anti-phagocytic signal enabling tumor cells to escape the innate immune response. Macrophage antitumor activity can be restored by simultaneously blocking the CD47-SIRPα signaling axis and inducing a pro-phagocytic signal with the use of tumor-opsonizing antibodies. Targeting SIRPα on monocytes and macrophages rather than the ubiquitously expressed CD47 may overcome some toxicities associated with anti-CD47 therapies. Here, we report the discovery and characterization of a fully human anti-SIRPα antibody and its preclinical activity in combination with the opsonizing antibody rituximab in CD20+ diffuse large B-cell lymphoma (DLBCL) cell lines.Methods: A total of ~ 10 10 fully human immunoglobulin G antibodies were screened for binding to the extracellular domain of recombinant human SIRPα using a yeast display platform. Surface plasmon resonance was used to determine CC-95251 binding coverage across SIRPα haplotypes. The ability of CC-95251 to block CD47-SIRPα interaction was measured using Octet ® and Biacore™ assays. We determined the crystal structure of SIRPα in complex with the CC-95251 Fab to characterize its epitope and to define the structural basis for CD47-SIRPα interaction blockade. To identify tumor types likely susceptible to CD47-SIRPα axis disruption, expression levels of CD47-SIRPα and CD163 were assessed in bulk tumor samples using The Cancer Genome Atlas (TCGA) data. The antitumor effects of CC-95251 in combination with rituximab were examined by measuring the percentage of phagocytic macrophages in co-culture experiments of differentiated macrophages and CD20+ DLBCL cell lines (OCI-Ly3, RIVA, Pfeiffer, and Karpas 422). To confirm CC-95251 binding to monocytes, immunophenotyping of peripheral blood mononuclear cells from healthy donors and cynomolgus monkeys was performed using multiparameter flow cytometry. Lastly, pharmacokinetics and hematologic effects were analyzed in cynomolgus monkeys after treatment with 10, 30, or 100 mg/kg CC-95251.Results: Initial screening by yeast display yielded ~ 350 candidates. The top 24 clones were characterized fully and CC-95251 was selected as the lead monoclonal antibody exhibiting high binding affinity across the 6 most prevalent SIRPα human haplotypes. CC-95251 potently blocked CD47-SIRPα binding in a dose-dependent manner, with a concentration of 100 nM inhibiting CD47 binding almost completely. Co-crystallization modeling showed that CC-95251 engages SIRPα in a region overlapping the CD47 binding site, demonstrating a mechanism for CD47-SIRPα blockade.DLBCL was identified as a suitable tumor type for CC-95251 treatment based on CD47-SIRPα expression and macrophage infiltration. Co-culture experiments of donor macrophages and several DLBCL cell lines showed that CC-95251 monotherapy had weak-to-moderate antitumor activity. However, when combined with rituximab, the levels of phagocytic macrophages were markedly increased in a CC-95251 dose-dependent manner, suggesting that inhibition of the CD47-SIRPα anti-phagocytic axis with CC-95251 and activation of pro-phagocytic signaling with rituximab provide an enhanced antitumor effect in DLBCL cell lines.CC-95251 predominantly bound to cells of myeloid origin, including monocytes and, to a lesser extent, myeloid dendritic cells, whereas no binding to natural killer cells was observed. Toxicology studies in cynomolgus monkeys showed safe intravenous delivery of CC-95251 at therapeutic doses, with no evidence of white blood cell, monocyte, lymphocyte, or red blood cell depletion.Conclusions: CC-95251 is a novel, high-affinity, fully human monoclonal anti-SIRPα antibody that blocks the binding of CD47 to SIRPα. When combined with the therapeutic opsonizing antibody rituximab, CC-95251 enhances macrophage phagocytic activity against DLBCL cell lines in co-culture models. These results support the clinical evaluation of CC-95251 + rituximab for relapsed or refractory NHL. A phase 1 dose-escalation and -expansion study of CC-95251 for the treatment of advanced solid and hematologic malignancies is underway (NCT03783403). DisclosuresChan: Bristol Myers Squibb: Current Employment. Trout: Bristol Myers Squibb: Ended employment in the past 24 months. Mikolon: Bristol Myers Squibb: Current Employment. Adams: Bristol Myers Squibb: Current Employment. Guzman: Bristol Myers Squibb: Current Employment, Current equity holder in publicly-traded company. Fenalti: Bristol Myers Squibb: Current Employment. Mavrommatis: Bristol Myers Squibb: Current Employment, Current equity holder in publicly-traded company. Abbasian: Bristol Myers Squibb: Current equity holder in publicly-traded company, Ended employment in the past 24 months. Dearth: Bristol Myers Squibb: Current Employment. Fox: Bristol Myers Squibb: Current Employment, Current equity holder in publicly-traded company. Sivakumar: Bristol Myers Squibb: Current Employment, Current equity holder in publicly-traded company. Hariharan: Bristol Myers Squibb: Current Employment.

Preclinical pharmacology and toxicology evaluation of an anti-CD52 monoclonal antibody produced by perfusion fermentation process.

Anti-cluster of differentiation 52 (CD52) monoclonal antibody (mAb) has been employed in the treatment of chronic lymphoblastic leukemia and multiple sclerosis. Previously we developed a perfusion process to produce the biosimilar mAb named “Mab-TH.” A series of quality assessments was conducted in the fields of structural identification, purity analysis, and activity measurement. After these quality researches, this report laid emphasis on preclinical pharmacology and toxicology evaluation. Mab-TH was characterized in biological, pharmacological, and toxicological properties in comparison with the original drug, alemtuzumab. Binding activity and immune-dependent toxicity as in vitro activity were evaluated. Severe immunodeficient mice transplanted with a human leukemia cell line were also used as an in vivo pharmacological model and a 4-week repeated dosing study in cynomolgus monkeys was conducted to evaluate the safety differences. Our results demonstrated that Mab-TH, the anti-CD52 antibody generated by a perfusion process, had high similarity in in vitro and in vivo activities compared with alemtuzumab in relevant preclinical models. The results supported it as a biosimilar candidate for clinical evaluation.

Murine models of Duchenne muscular dystrophy: is there a best model?

Murine models of Duchenne muscular dystrophy: is there a best model?

Abstract 498: ZL-1201, a differentiated CD47 therapeutic antibody with improved hematological safety profile

Abstract The interaction between CD47 that is overexpressed on tumor cells and SIRPα on macrophages facilitates a “don't-eat-me” signal that inhibits macrophage-mediated phagocytosis of tumor cells. Blockade of the CD47/SIRPα interaction using antibodies against CD47 or SIRPα-Fc fusion proteins promotes phagocytosis and tumor cell destruction, which represents a promising strategy for tumor immunotherapy. However, CD47 is ubiquitously expressed on all cells including erythrocytes and platelets, which form a large antibody sink and lead to potential hematological toxicities. In fact, anemia and thrombocytopenia have been observed in non-human primates and tumor patients that are subjected to anti-CD47 treatment in preclinical and clinical studies. We have developed ZL-1201, a recombinant, humanized monoclonal antibody that specifically targets CD47. ZL-1201 was engineered to reduce Fc-mediated antibody effector function. Preclinical in vitro studies show that ZL-1201 displays potent binding to CD47 thereby blocking interaction with SIRPα and effectively facilitates macrophage-mediated phagocytosis of hematological and solid tumor cells. Importantly, ZL-1201 induces minimal red blood cell (RBC) phagocytosis and does not induce hemagglutination, though it does bind to human RBCs and platelets. In vivo studies demonstrate that ZL-1201 possesses potent antitumor efficacy in rodent xenograft tumor models, while displaying remarkably improved hematological safety profile as compared with the benchmark antibody in a toxicology study in cynomolgus monkeys. Thus, ZL-1201 treatment represents an effective CD47-targeting therapy with improved hematological safety consequences. A Ph1 dose escalation study to assess the safety of ZL-1201 is currently ongoing in patients with solid tumors, and future combination studies are planned for both hematologic and solid tumor indications. Citation Format: Bing Wan, Xu Fang, Shou Li, Wenhua Shi, Holly Li, David Bellovin, Lei Wang, Yusong Zhu, Yuan Lin, Shali Qi, Sophia Yin, Frank Tao, Lishan Kang, Omar Kabbarah, Haiying Zhou, Petter Veiby, James Yan, Karl Hsu. ZL-1201, a differentiated CD47 therapeutic antibody with improved hematological safety profile [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 498.

Abstract 925: Introduction to the preclinical profile of SYD1875, a novel site-specifically conjugated duocarmycin-based 5T4-targeting antibody-drug conjugate

Abstract 5T4 is an oncofetal antigen with low expression in healthy tissues which is frequently overexpressed in different tumor types. Despite its overexpression in various malignancies and its association with poor prognosis, there are currently no marketed drugs that target this tumor antigen. We developed a novel antibody-drug conjugate (ADC), named SYD1875, comprising a humanized, HC41-cysteine-engineered IgG1 monoclonal antibody directed against 5T4, site-specifically conjugated to a proprietary cleavable synthetic duocarmycin-based linker-drug (vc-seco-DUBA). SYD1875 showed sub-nanomolar binding affinity to human and cynomolgus 5T4, rapid internalization, and induction of both target- and bystander-mediated cell killing. SYD1875 showed superior in vitro cytotoxicity and in vivo activity compared to A1-mcMMAF -also known as PF-6263507-, a 5T4-targeting ADC that is no longer in clinical development. A single dose of SYD1875 induced strong anti-tumor activity in patient-derived xenograft models of multiple tumor types with low, moderate and high 5T4 expression. The GLP toxicity study in cynomolgus monkey showed an acceptable toxicity and PK profile. A first-in-human dose-finding trial was initiated to evaluate safety and explore efficacy (NCT04202705). Citation Format: Patrick Groothuis, Danielle Jacobs, Kim Berentsen, Monique van der Vleuten, Ruud Coumans, Ronald Elgersma, Marion Blomenrohr, Diels van den Dobbelsteen, Patrick Beusker, Ruud Ubink, Miranda van der Lee, Wim H.A. Dokter. Introduction to the preclinical profile of SYD1875, a novel site-specifically conjugated duocarmycin-based 5T4-targeting antibody-drug conjugate [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 925.