Preclinical Efficacy Research Articles

Preclinical Efficacy of a PSMA-Targeted Actinium-225 Conjugate (225Ac-Macropa-Pelgifatamab): A Targeted Alpha Therapy for Prostate Cancer.

Initially, prostate cancer responds to hormone therapy, but eventually resistance develops. Beta emitter-based prostate-specific membrane antigen (PSMA)-targeted radionuclide therapy is approved for the treatment of metastatic castration-resistant prostate cancer. Here we introduce a targeted alpha therapy (TAT) consisting of the PSMA antibody pelgifatamab covalently linked to a macropa chelator and labeled with actinium-225 and compare its efficacy and tolerability with other TATs. The in vitro characteristics and in vivo biodistribution, antitumor efficacy, and tolerability of 225Ac-macropa-pelgifatamab (225Ac-pelgi) and other TATs were investigated in cell line- and patient-derived prostate cancer xenograft models. The antitumor efficacy of 225Ac-pelgi was also investigated in combination with the androgen receptor inhibitor darolutamide. Actinium-225-labeling of 225Ac-pelgi was efficient already at room temperature. Potent in vitro cytotoxicity was seen in PSMA-expressing (LNCaP, MDA-PCa-2b, and C4-2) but not in PSMA-negative (PC-3 and DU-145) cell lines. High tumor accumulation was seen for both 225Ac-pelgi and 225Ac-DOTA-pelgi in the MDA-PCa-2b xenograft model. In the C4-2 xenograft model, 225Ac-pelgi showed enhanced antitumor efficacy with a T/Cvolume (treatment/control) ratio of 0.10 compared with 225Ac-DOTA-pelgi, 225Ac-DOTA-J591, and 227Th-HOPO-pelgifatamab (227Th-pelgi; all at 300 kBq/kg) with T/Cvolume ratios of 0.37, 0.39, and 0.33, respectively. 225Ac-pelgi was less myelosuppressive than 227Th-pelgi. 225Ac-pelgi showed dose-dependent treatment efficacy in the patient-derived KuCaP-1 model and strong combination potential with darolutamide in both cell line- (22Rv1) and patient-derived (ST1273) xenograft models. These results provide a strong rationale to investigate 225Ac-pelgi in patients with prostate cancer. A clinical phase I study has been initiated (NCT06052306).

Autologous Blood-Derived Products (ABDPs) for the Treatment of Chronic Wounds.

Autologous blood-derived therapies have emerged as a unique and promising treatment option for chronic wounds. From whole blood clots to spun-down clot constituents, these therapies are highly versatile and tend to have a lower cost profile, allow for point-of-service preparation, and inherently carry minimal to no risk of rejection or allergic reaction when compared to many alternative cellular and matrix-like products. Subsequently, a diversity of processing systems, devices, and kits have surfaced on the market for preparing autologous blood-derived products (ABDPs) and many have demonstrated preclinical and clinical efficacy in facilitating chronic wound healing. However, not all ABDPs are created equal, and the lack of standardization among product formulations and cell concentrations as well as varying complexities in preparation protocols has led to unreliable substrate viabilities and overall inconsistent conclusions on efficacy. Additionally, external factors, such as the ease of drawing blood, the health of a patient's blood, and the reimbursement landscape have dissuaded some practitioners from incorporating ABDPs into an algorithm of care for recalcitrant wounds. Here, we attempt to categorize ABDPs into "classes" and examine their efficacy, advantages, and limitations when used as both a primary therapy and an adjunct for treating chronic wounds as well as comment on some potential considerations that may help gear future product development and application.

Abstract LB363: A novel humanized NKP46 mouse model to support xenograft studies evaluating NK cell-based cancer immunotherapies

Abstract The NKP46 receptor is expressed by all NK cells, and plays a key role in the recognition and activation of NK cells against tumor cells. Cross-linking of NKp46 by monoclonal antibodies triggers both NK cell cytotoxic activity and cytokine release. As the only NCR present in mice, NKP46 is well conserved, but differences between the murine and human NKP46 protein necessitate use of humanized mice for evaluating preclinical efficacy of novel NKP46-targeting antibodies. Previously, we established humanized NKP46 mice on immunocompetent backgrounds for evaluating antibody efficacy in preventing growth of syngeneic tumor models. However, xenograft models in immunodeficient mice have also been widely employed as important in vivo models. Here, we describe a novel humanized NKP46 mouse on the CB-17-SCID background in order to inoculate human tumor cells for therapeutic efficacy testing. In this model, using gene editing technology, the portion of the mouse NKp46 gene encoding the extracellular domain was replaced by the corresponding human NKP46 coding sequences. Human NKP46 protein expression was confirmed on NK cells derived from splenocytes and bone marrow of B-hNKP46 mice(CB17-SCID) by flow cytometry. Subsequently, assessment of leukocyte populations in the humanized model indicated no significant alterations in the percentages of NK cells, dendritic cells, granulocytes, monocytes and macrophages in the spleen, bone marrow or blood of the humanized mice compared with wild-type CB17-SCID mice. Finally, tumor efficacy studies demonstrate that treatment with an anti-human NKP46 antibody significantly reduced BxPC-3 tumor growth at a range of doses in homozygous hNKP46 mice compared to PBS-injected controls. In summary, humanized B-hBKP46 mice(CB17-SCID) provide a suitable model for evaluating the efficacy of anti-human NKP46 antibody candidates. Citation Format: Zhenlan Niu, Yongshun Li, Xiaofei Zhou, Jiawei Yao, Qingcong Lin, Meiqi Zhang, Qingqing Xu. A novel humanized NKP46 mouse model to support xenograft studies evaluating NK cell-based cancer immunotherapies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr LB363.

Abstract LB028: Discovery and characterization of selective heterobifunctional degraders of EP300 in hematopoietic malignancies

Abstract The paralogous histone acetyltransferases EP300 and CREBBP are two of the master regulators of transcription by controlling both enhancer and promoter activity through histone and non-histone acetylation. EP300 and CREBBP activity is primarily driven by their acetylation of K27 and K18 on histone H3 leading to open and active chromatin state. Targeting the EP300/CREBBP axis of chromatin regulation may be a way to disrupt the signaling pathways downstream of key oncogenic signaling networks like MYC/IRF4 in hematopoietic cancers. Successful development of dual EP300/CREBBP BRDi and HATi has led to promising pre-clinical efficacy, but due to observed tolerability issues may potentially limit their utility in the clinic. We hypothesized, based upon published mouse KO phenotypes, that a selective EP300 compound may improve tolerability. Due to the high sequence homology between EP300 and CREBBP in both the BRD and HAT domains, developing selective inhibitors has proven to be challenging. To combat this, we have utilized heterobifunctional protein degrader technology (ProDegs, also known as PROTACS) to develop EP300 selective ProDegs with greater than 100-fold selectivity over CREBBP. We observe rapid targeted degradation of EP300 with maximal degradation occurring within the first 2-4 hours after treatment. Concomitant with the loss of EP300, we see modulation of the associated H3K27ac and H3K18ac biomarkers as well as alterations in key oncogenic transcription networks. In both in vitro and in vivo assays looking at impact to platelet maturation, we observed that selective loss of EP300 largely abrogated observed thrombocytopenia compared to dual EP300/CREBBP inhibitors. Upon treatment, MM and NHL models show strong downregulation of MYC/IRF4 oncogenic signaling pathways, both of which culminate in a loss of cellular viability and cell death. Additionally, we observe in vivo dose responsive tumor growth inhibition in OPM2 and Pfeiffer xenograft models. Together, the data demonstrate the potential utility of EP300 selective ProDegs for the treatment of hematopoietic malignancies. Citation Format: Frederick A. Derheimer, Ninvita Givarkes, Natalie Miller, Rita Grantner, Casey Quinlan, Sonja Brun, Thomas Paul, Astrid Ruefli-Brasse, Stefan Steyn, Derek Bartlett, Matthew Hayward, Matthew Brown, Daniel Uccello, Benjamin J. Burke, Kris Borzilleri, Adam Gilbert, Michelle Hemkens. Discovery and characterization of selective heterobifunctional degraders of EP300 in hematopoietic malignancies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr LB028.

Abstract CT194: N-myristoylation inhibitor zelenirstat: New mechanistic insights and efficacy signals from a first in human phase I study

Abstract Introduction. Zelenirstat (PCLX-001) is a small molecule inhibitor of N-myristoylation, a process that involves addition of the fatty acid myristate to over 200 proteins by two N-myristoyltransferases (NMT1 and 2). These include Src family kinases and c-Abl. Inhibition of N-myristoylation by zelenirstat leads to the degradation of non-myristoylated proteins and cancer cell death. We conducted a phase I trial to evaluate the safety, tolerability, and maximally tolerated dose (MTD) of zelenirstat in patients with refractory cancer. Methods. Differential mass spectrometry was performed in NMT1 and NMT2 CRISPR/Cas9 KOs or zelenirstat-treated HAP1 cells to identify N-myristoylation-regulated proteins. Fully consented patients with advanced solid malignancies or refractory B-cell lymphomas were administered escalating doses of zelenirstat in 28-day cycles until progression or dose-limiting toxicity (DLT). Results. Proteomic analysis of cells with genetic or pharmacological NMT inhibition was performed to gain insights into NMT substrates and function. In addition to the rapid degradation of SFKs, which disrupts the pro-survival signaling of RTKs, we identified multiple respiratory complex I proteins as the most degraded, including NDUFAF4. NMT1 KO and zelenirstat treatment disrupted complex I leading to oxidative phosphorylation (OXPHOS) inhibition, which is essential for both cancer stem cell survival and metastasis. Continuous once-daily zelenirstat at 20 mg to 210 mg was well tolerated, with no dose-limiting toxicities in 24 patients up to and including 210 mg. Gastrointestinal DLTs were observed in the 280 mg cohort, establishing 210 mg as the MTD. Oral absorption was rapid, and pharmacokinetics were suitable for once daily dosing. Seven patients had stable disease as best response, including pancreatic, ovarian and colon cancer patients; one colon cancer patient with 5 prior lines of therapy continues 210 mg beyond 11 cycles with reduction in carcinoembryonic antigen (CEA) and tumor dimensions. Kaplan-Meier analysis revealed longer progression-free survival (log-rank p=0.033) and overall survival (p=0.026) in the patients treated at 210 mg (n=7) when compared with patients treated in lower dose cohorts (n=17). Conclusion. Zelenirstat has a unique dual impact on growth signaling and OXPHOS. Having previously demonstrated pre-clinical efficacy in hematologic cancers in vitro and in vivo, we now demonstrate the therapeutic potential of zelenirstat in patients with refractory advanced solid malignancies, warranting further clinical evaluation in these indications. Citation Format: Luc Gerard Berthiaume, Erwan Beauchamp, Jay Gamma, Rony Pain, Morris A. Kostiuk, Christopher R. Cromwell, Eman W. Moussa, Olivier Julien, Basil P. Hubbard, John Kuruvilla, Laurie H. Sehn, Jennifer Spratlin, Rahima Jamal, Randeep Sangha, John R. Mackey. N-myristoylation inhibitor zelenirstat: New mechanistic insights and efficacy signals from a first in human phase I study [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr CT194.

Abstract LB056: IBI334, a novel ADCC-enhanced B7-H3/EGFR bispecific antibody, demonstrated potent pre-clinical efficacy in solid tumors

Abstract Many solid tumors, such as colorectal cancer (CRC) and lung cancer, are dependent on epidermal growth factor receptor (EGFR) pathway for tumor growth. Antibodies that inhibit EGFR signaling, such as Cetuximab, show clinical efficacy but are associated with on-target toxicities that potentially limit the drug efficacy. To enhance the EGFR signaling inhibition and reduce on-target toxicities, we performed bioinformatics analysis for EGFR/TAA co-expression. We found that B7-H3, a member of the B7 family of immune checkpoint proteins, is broadly expressed in many solid tumors and their expression correlates with EGFR expression in multiple cancers, including lung cancer, head and neck cancer, pancreatic cancer and esophageal cancer. Using Innovent’s proprietary Innobody platform, we developed a bispecific antibody, IBI334, against B7-H3 and EGFR. IBI334 has an EGFR arm for signal blockage and is coupled with a fine-tuned B7-H3 arm with optimal affinity and binding domain. With the aid of B7-H3, IBI334 showed enhanced EGFR signal inhibition than Zalutumumab (EGFR mAb) and Amivantamab (c-met/EGFR bsAb). In addition, IBI334 is afucosylated to enhance its antibody-mediated cell cytotoxicity (ADCC) effects as compared to wild type antibody. IBI334 showed significantly better in vivo efficacy than Amivantamab in NCI-H358 (bronchioalveolar carcinoma with KRAS-G12C mutation), NCI-H292 (lymph node metastasis of a pulmonary mucoepidermoid carcinoma), SK-MES1 (lung cancer) and SK-MES1-LTC (lung cancer with EGFR L858R, T790M and C797S mutations) xenograft models and comparable efficacy in NCI-H322-EGFRexon20ins (lung cancer) model. Cetuximab, an EGFR monoclonal antibody, had high on-target toxicity with 50% early mortalities in cynomolgus monkeys at 120/75 mg/kg/week. With the careful design of B7-H3/EGFR bispecific antibody, IBI334 ameliorated the on-target toxicities and showed only slight hardening of the skin at the injection site at 120 mg/kg/week. As a result, IBI334 has a large therapeutic window of >200 folds. In conclusion, IBI334 is a potent B7-H3/EGFR bispecific antibody with broad application in many EGFR-driven solid tumors. The large therapeutic window enables safe and effective cancer treatment at high exposure levels. Citation Format: Jian Guan, Shuaixiang Zhou, Weiwei Wu, Tianyu Zhu, Lei Cao, Ming Wu, Ninghuan Li, Fenggen Fu, Zhengguan Liao, Shuming Lin, Zeyu Liu, Mengjia Zhu, Nana Luo, Ying Zhang, Tiong Sun Chia, Bingliang Chen, Kaijie He. IBI334, a novel ADCC-enhanced B7-H3/EGFR bispecific antibody, demonstrated potent pre-clinical efficacy in solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr LB056.

Abstract CT142: Phase 1 study of BPI-23314, a novel BET inhibitor and degrader, in advanced myeloid leukemia (AML)

Abstract Background: The novel small-molecule inhibitor and degrader, BPI-23314, targeting of the bromodomain and extra-terminal domain (BET) family proteins, BPI-23314, has been showndemonstrated promising preclinical efficacy in hematologic malignancies. This Phase 1 study aims to evaluate the safety, pharmacokinetics, and preliminary efficacy of BPI-23314 monotherapy in patients with relapsed or refractory acute myeloid leukemia (R/R AML). Methods: This ongoing phase 1 study of BPI-23314 enrolled adult patients with R/R AML. Dose escalation was conducted using a standard 3+3 design, followed by additional expansion cohorts to further assess safety and preliminary efficacy. BPI-23314 tablets were administered orally once daily (QD) or twice daily (BID) in consecutive 21-day cycles. The key endpoints included determining the recommended Phase 2 dose (RP2D), safety, pharmacokinetics, and preliminary efficacy. Results: As of July 31, 2022, a total of 22 patients diagnosed with R/R AML were treated with BPI-23314 at seven different dose levels, ranging from 5 to 60 mg QD or 40 to 50 mg BID. The median age of the patients was 48 years (range: 19-68 years), and the median treatment duration was 6 weeks (range: 2-9 weeks). The median number of prior therapy lines was 3 (range: 1-4), with 15 (68.2%) being refractory to last line of therapy. Due to the high incidence of grade≥3 anemia, thrombocytopenia, and neutropenia among the patients at baseline, most treatment-emergent adverse events (TEAE) of hematologic toxicities were mainly correlated with disease progression. Only one patient experienced grade 3 treatment-related adverse events (TRAE) comprising anemia (4.5%) and neutropenia (4.5%). Non-hematologic TRAEs were predominantly of grade 1-2. The most common TRAEs (≥10%) were gastrointestinal reactions (10/22, 45.5%), hypertriglyceridemia (6/22, 27.3%), hyperbilirubinemia (4/22, 18.2%), elevated alanine aminotransferase levels (3/22, 13.6%), and increased gamma-glutamyl transferase levels (3/22, 13.6%). Gastrointestinal reactions characterized by nausea and/or diarrhea were the most commonly reported toxicities. The most common TEAEs associated with disease progression were infection and bleeding. No dose-limiting toxicity or treatment-related deaths were reported during the study period, and the maximum tolerated dose was not reached. Among the evaluable responses in all dose levels for R/R AML patients (n=21), one patient achieved complete response (CR) at a dosage of 40 mg BID while three patients maintained stable disease (SD) across various dosages, including QD at 60 mg and BID at both 40 mg and 50 mg. Furthermore, BPI-23314 demonstrated moderate elimination kinetics, with a plasma half-life ranging from 8.6 to 23.3 hours, while exhibiting dose-proportional exposure. Conclusion: BPI-23314 monotherapy exhibited preliminary clinical efficacy with manageable adverse events in patients with R/R AML. The study is ongoing. The satisfactory pharmacokinetic attribute and outstanding safety profile of BPI-23314 provide compelling rationales for further exploration of its therapeutic potential. Citation Format: Mingyuan Sun, Xiangyu Jin, Jing Guo, Xiaoyun Liu, Yan Xu, Hong Lan, Jiabing Wang, Jiangnan Zhen, Jing Yang, Lieming Ding, Junyuan Qi. Phase 1 study of BPI-23314, a novel BET inhibitor and degrader, in advanced myeloid leukemia (AML) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr CT142.

Abstract LB438: Preclinical characterization of ONM-412, an ultra-pH sensitive nanoparticle encapsulated IL-12 fusion protein

Abstract Background: Interleukin-12 is a potent pleiotropic cytokine, but its clinical translation has been hindered by toxicities. To deliver IL-12 to tumors with high spatial and temporal precision while minimizing off-tumor effects, we have developed an ultra-pH sensitive nanoparticle platform - ON-BOARD - that shields payloads from systemic exposure and targets solid tumors by responding to tumor acidity. Herein, we report the preclinical efficacy and safety characterization of ONM-412, an ON-BOARD nanoparticle encapsulated IL-12Fc fusion protein, and muONM-412, an encapsulated murine IL-12Fc. Methods: Properties and stability profiles of ONM-412 were characterized. pH-specific bioactivity was determined in cell-based reporter and IFNγ induction assays while the activation of ONM-412 was compared to a protease-cleavable IL-12 prodrug. Efficacy and tolerability of muONM-412 were studied in vivo after intravenous injection in mice. Pharmacodynamic response was evaluated by measuring cytokine levels in plasma and tissue, and the changes in tumor immune microenvironment were characterized. Toxicity was measured by body weight loss, systemic cytokine levels and clinical chemistry. Anti-tumor efficacy of muONM-412 was evaluated in MC38 tumor-bearing mice. The safety and tolerability of ONM-412 is also undergoing evaluation in a toxicology study with cynomolgus monkeys. Body weight, hematology, clinical chemistry and urine analysis were performed. Results: ONM-412 showed high encapsulation efficiency (>85%) in uniformly distributed particles (Dh<50nm) with 6-month on-going shelf-life stability. pH-specific release was confirmed in vitro with a >100-fold activation window between the acid-activated and intact formulations by an HEK reporter assay and an IFNγ induction assay. ONM-412 showed rapid and complete recovery of IL-12 bioactivity in <10 minutes after acid-activation while MMP demasking of a prodrug required overnight incubation and compromised potency. In vivo, mice treated with muONM-412 demonstrated significantly improved tolerability compared to unencapsulated IL-12Fc: body weight loss was reduced, no liver toxicity was observed, and plasma IFNγ levels were >1,000-fold lower. muONM-412 induced tumor immune remodeling, with increased infiltration by IFNγ+ and GzmB+ CD8 T and NK cells, and demonstrated strong dose-responsive anti-tumor efficacy in MC38 tumor-bearing animals. Preliminary results from an on-going study in cynomolgus monkeys suggest ONM-412 is well-tolerated at equivalent doses to those that induced maximum antitumor response in mice. Conclusions: ONM-412 significantly improved tolerability over unencapsulated IL-12Fc and showed potent anti-tumor efficacy in mice. It was well-tolerated in mice and non-human primates, showing potential for clinical translation. Citation Format: Qingtai Su, Stephen Gutowski, Austin Burcham, Bhargavi Allu, Zirong Chen, Fiona Stavros, Ruolan Han, Jason B. Miller, Tian Zhao. Preclinical characterization of ONM-412, an ultra-pH sensitive nanoparticle encapsulated IL-12 fusion protein [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr LB438.

Abstract LB063: Anti-tumor activity in preclinical models utilizing a conditional bispecific redirected activation molecule (COBRA) targeting Her2

Abstract Among strategies to recruit cytotoxic T-cells into the tumor micro-environment (TME) are the use of T-cell engager molecules. One such therapeutic modality are molecules that recognize specific tumor associated antigens (TAA) but are activated preferentially in the TME. Conditional Bispecific Redirected Activation molecules (COBRA) are designed to be administered as a prodrug, and cleaved via matrix metalloproteinase to engage with both a tumor TAA and CD3 (Panachi, et.al. MAbs 2020 12(1) 1792130). In this study, we sought to determine the preclinical efficacy of a COBRA molecule targeting the Her2 receptor. Sub-cutaneous xenograft models (SCID mice using adoptive T-cell transfer) were utilized representing various levels of the TAA (HT-55, SNU-16, JIMT-1, and HCC827) to measure both efficacy and mechanism of action (T-cell extravasation). The COBRA molecule was dosed at 0.03, 0.1, 0.3, and 1 mg/kg using a Q3dx7 schedule. A non-cleavable COBRA molecule with the Her2 TAA was included as a control at 1 mg/kg. Efficacy was determined by caliper measurements of sub-cutaneous tumor size twice per week after dosing, and T-cell extravasation into the TME was measured by immunohistochemistry (IHC) at days 10, 19, and termination. IHC data was quantified using HALO imaging software. In our study, we measured dose-dependent tumor regression and/or stasis in all models tested. No anti-tumor activity was measured after dosing with the non-cleavable COBRA molecule. T-cell extravasation as measured by IHC and Halo analysis followed a dose and time dependent course. Comparison of Day 19 T-cell extravasation (one day after the last dose) showed a linear relationship to TAA expression. Our data indicate that treatment with a COBRA molecule in preclinical models with a Her2 TAA results in anti-tumor activity as measured by tumor stasis/regression, and exhibit the expected mechanism of action as evaluated by T-cell extravasation into the TME. Citation Format: Bradley Stringer, Johara Chouitar, Jacqualine Cerbone, Sarah Fortin, Alina Ainbinder, Cassie Kysilovsky, Brittany Scott, Antara Banerjee. Anti-tumor activity in preclinical models utilizing a conditional bispecific redirected activation molecule (COBRA) targeting Her2 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr LB063.

Assessment of the Artemia salina toxicity assay as a substitute of the mouse lethality assay in the determination of venom-induced toxicity and preclinical efficacy of antivenom

Mice are routinely used in snake venom research but are costly and subject to pain and suffering. The crustacean Artemia salina could be an alternative to mice, but data to support its adoption in snake venom research is limited. The aim of the present study was to evaluate the suitability of A. salina as a surrogate of mice in assessing the toxicity of venoms and the preclinical efficacy of antivenoms. The toxicity of venoms from 22 snakes of medical importance in sub–Saharan Africa was evaluated in mice (intraperitoneally; i.p. and intravenously; i.v.) and in A. salina. Subsequently, the capacity of a commercial antivenom to neutralize the toxicity of these venoms in mice and A. salina was investigated. There was a positive correlation between the i.v. median lethal doses (LD50s) and the i.p. LD50s in mice (r = 0.804; p < 0.0001), a moderate correlation between the i.v. LD50s in mice and the median lethal concentrations (LC50s) in A. salina (r = 0.606; p = 0.003), and a moderate correlation between the i.p. LD50s in mice and the LC50s in A. salina (r = 0.426; p = 0.048). Moreover, there was a strong correlation between the i.p. median effective doses (ED50s) and the i.v. ED50s in mice (r = 0.941, p < 0.0001), between the i.p. ED50s in mice and the ED50s in A. salina (r = 0.818, p < 0.0001), and between the i.v. ED50s in mice and the ED50s in A. salina (r = 0.972, p < 0.0001). These findings present A. salina as a promising candidate for reducing reliance on mice in snake venom research. Future investigations should build upon these findings, addressing potential limitations and expanding the scope of A. salina in venom research and antivenom development.

A measles-vectored vaccine candidate expressing prefusion-stabilized SARS-CoV-2 spike protein brought to phase I/II clinical trials: candidate selection in a preclinical murine model.

In the early COVID-19 pandemic with urgent need for countermeasures, we aimed at developing a replicating viral vaccine using the highly efficacious measles vaccine as vector, a promising technology with prior clinical proof of concept. Building on our successful pre-clinical development of a measles virus (MV)-based vaccine candidate against the related SARS-CoV, we evaluated several recombinant MV expressing codon-optimized SARS-CoV-2 spike glycoprotein. Candidate V591 expressing a prefusion-stabilized spike through introduction of two proline residues in HR1 hinge loop, together with deleted S1/S2 furin cleavage site and additional inactivation of the endoplasmic reticulum retrieval signal, was the most potent in eliciting neutralizing antibodies in mice. After single immunization, V591 induced similar neutralization titers as observed in sera of convalescent patients. The cellular immune response was confirmed to be Th1 skewed. V591 conferred long-lasting protection against SARS-CoV-2 challenge in a murine model with marked decrease in viral RNA load, absence of detectable infectious virus loads, and reduced lesions in the lungs. V591 was furthermore efficacious in an established non-human primate model of disease (see companion article [S. Nambulli, N. Escriou, L. J. Rennick, M. J. Demers, N. L. Tilston-Lunel et al., J Virol 98:e01762-23, 2024, https://doi.org/10.1128/jvi.01762-23]). Thus, V591 was taken forward into phase I/II clinical trials in August 2020. Unexpected low immunogenicity in humans (O. Launay, C. Artaud, M. Lachâtre, M. Ait-Ahmed, J. Klein et al., eBioMedicine 75:103810, 2022, https://doi.org/10.1016/j.ebiom.2021.103810) revealed that the underlying mechanisms for resistance or sensitivity to pre-existing anti-measles immunity are not yet understood. Different hypotheses are discussed here, which will be important to investigate for further development of the measles-vectored vaccine platform.IMPORTANCESARS-CoV-2 emerged at the end of 2019 and rapidly spread worldwide causing the COVID-19 pandemic that urgently called for vaccines. We developed a vaccine candidate using the highly efficacious measles vaccine as vector, a technology which has proved highly promising in clinical trials for other pathogens. We report here and in the companion article by Nambulli et al. (J Virol 98:e01762-23, 2024, https://doi.org/10.1128/jvi.01762-23) the design, selection, and preclinical efficacy of the V591 vaccine candidate that was moved into clinical development in August 2020, 7 months after the identification of SARS-CoV-2 in Wuhan. These unique in-human trials of a measles vector-based COVID-19 vaccine revealed insufficient immunogenicity, which may be the consequence of previous exposure to the pediatric measles vaccine. The three studies together in mice, primates, and humans provide a unique insight into the measles-vectored vaccine platform, raising potential limitations of surrogate preclinical models and calling for further refinement of the platform.

Cell-engineered virus-mimetic nanovesicles for vaccination against enveloped viruses.

Enveloped viruses pose a significant threat to human health, as evidenced by the recent COVID-19 pandemic. Although current vaccine strategies have proven effective in preventing viral infections, the development of innovative vaccine technologies is crucial to fortify our defences against future pandemics. In this study, we introduce a novel platform called cell-engineered virus-mimetic nanovesicles (VNVs) and demonstrate their potential as a vaccine for targeting enveloped viruses. VNVs are generated by extruding plasma membrane-derived blebs through nanoscale membrane filters. These VNVs closely resemble enveloped viruses and extracellular vesicles (EVs) in size and morphology, being densely packed with plasma membrane contents and devoid of materials from other membranous organelles. Due to these properties, VNVs express viral membrane antigens more extensively and homogeneously than EVs expressing the same antigen. In this study, we produced severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) VNVs expressing the SARS-CoV-2 Spike glycoprotein (S) on their surfaces and assessed their preclinical efficacy as a COVID-19 vaccine in experimental animals. The administration of VNVs successfully stimulated the production of S-specific antibodies both systemically and locally, and immune cells isolated from vaccinated mice displayed cytokine responses to S stimulation.

Age-related changes in species-typical behaviours in the 5xFAD mouse model of Alzheimer’s disease from 4 to 16 months of age

Alzheimer’s disease (AD) patients show age-related decreases in the ability to perform activities of daily living and the decline in these activities is related to the severity of neurobiological deterioration underlying the disease. The 5xFAD mouse model of AD shows age-related impairments in sensory- motor and cognitive function, but little is known about changes in species-typical behaviours that may model activities of daily living in AD patients. Therefore, we examined species-typical behaviours used as indices of exploration (rearing) and compulsivity (grooming) across six tests of anxiety-like behaviour or motor function in female 5xFAD mice from 3 to 16 months of age. Robust decreases in rearing were found in 5xFAD mice across all tests after 9 months of age, although few differences were observed in grooming. A fine-scale analysis of grooming, however, revealed a previously unresolved and spatially restricted pattern of grooming in 5xFAD mice at 13–16 months of age. We then examined changes in species-typical behaviours in the home-cage, and show impaired nest building in 5xFAD mice at all ages tested. Lastly, we examined the relationship between reduced species typical behaviours in 5xFAD mice and the presentation of freezing behaviour, a commonly used measure of memory for conditioned fear. These results showed that along with cognitive and sensory-motor behaviour, 5xFAD mice have robust age-related impairments in species-typical behaviours. Therefore, species typical behaviours in 5xFAD mice may help to model the decline in activities of daily living observed in AD patients, and may provide useful behavioural phenotypes for evaluating the pre-clinical efficacy of novel therapeutics for AD.

Abstract 2362: Preclinical efficacy and safety of M9140, a novel antibody-drug conjugate (ADC) with topoisomerase 1 (TOP1) inhibitor payload targeting carcinoembryonic antigen-related cell adhesion molecule 5 (CEACAM5)-expressing colorectal tumors

Abstract Background: M9140 is the first clinical-stage TOP1 inhibitor payload ADC directed against CEACAM5, which is expressed in colorectal cancer (CRC) and other cancer indications. M9140 is composed of a CEACAM5-specific antibody conjugated to eight, highly stable and hydrophilic ß-glucuronide-exatecan linker-payloads. After linker cleavage, the highly potent and membrane permeable TOP1 inhibitor exatecan is released. Methods: M9140 potency was tested in viability assays using cancer cell lines with different levels of CEACAM5 expression. Potency shift viability assays were conducted using two CRC cell lines, with zosuquidar used as multidrug resistance-1 (MDR-1) inhibitor. The M9140 bystander effect was assessed in co-culture experiments with CEACAM5-negative and -positive cancer cells. Antitumor efficacy and safety were evaluated in patient-derived xenograft (PDX) mouse models and in cynomolgus monkeys, respectively. Results: M9140 demonstrated specific binding to CEACAM5 and selective killing of target-positive cancer cells with potencies between 0.09 nM and 0.62 nM. A potent bystander effect of M9140 was demonstrated in co-culture experiments indicating the potential to treat tumors with heterogeneous target expression. Unlike other ADC payloads such as monomethyl auristatin E (MMAE) and the maytansine derivative DM4, exatecan potency was not affected by MDR-1 inhibition, indicating that this drug efflux resistance mechanism may not be relevant for exatecan. A single treatment with 10 mg/kg M9140 caused strong antitumor effects in all 14 CRC PDX models tested, with tumor stasis in 10 models and tumor regression in four models as the best response. The TOP1 inhibitor-based ADC M9140 caused strong antitumor efficacy with a tumor volume reduction of 74% and 88% as best response in two CRC PDX models where a maytansine-based CEACAM5 ADC was not effective. In cynomolgus monkeys, M9140 showed dose-dependent hematolymphoid and intestinal effects, consistent with exatecan payload, with no indication of any other toxicities such as interstitial lung disease (ILD) or ocular toxicity. Conclusions: M9140 demonstrated high potency, strong antitumor activity, and bystander effect in preclinical models. The side effect profile in monkeys was favorable and in line with the expected toxicity of exatecan. Notably, ILD and ocular toxicity, which are known adverse effects of deruxtecan and maytansine-based ADCs respectively, were absent. A first-in-human study to evaluate the safety, tolerability, pharmacokinetics, and preliminary clinical activity of M9140 in advanced solid tumors is ongoing (NCT05464030). Citation Format: Sabine Raab-Westphal, Felix Hart, Willem Sloot, Min Shan, Nicolas Rasche, Christiane Amendt, Jan Anderl. Preclinical efficacy and safety of M9140, a novel antibody-drug conjugate (ADC) with topoisomerase 1 (TOP1) inhibitor payload targeting carcinoembryonic antigen-related cell adhesion molecule 5 (CEACAM5)-expressing colorectal tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2362.

Abstract 1900: TORL-3-600, a novel antibody drug conjugate directed against cadherin 17 (CDH17), has preclinical efficacy in colorectal, gastric, and pancreatic cancer

Abstract Cadherin 17 (CDH17) is a cell-to-cell adhesion protein that is a member of the cadherin superfamily. In normal tissues, expression of this single pass transmembrane protein is restricted to the lateral surfaces of intestinal and pancreatic ductal epithelial cells. However, in cancer, CDH17 is frequently overexpressed in tumors of the colon, stomach, and pancreas. The selective expression of this cell surface protein in these hard-to-treat cancer makes it an attractive target for the development of antibody-based therapeutics. Here, we describe the preclinical development of TORL-3-600, a novel CDH17-targeting antibody drug conjugate (ADC). CDH17 specific monoclonal antibodies were generated using traditional hybridoma technology and splenocytes isolated from mice immunized with cocktails of NIH3T3 cells overexpressing full length hCHD17 plus purified mammalian expressed hCDH17 extracellular domain protein (aa 23-787). Selective mAb binding was confirmed by flow cytometry and mAb internalization rate was assessed by immunofluorescence (IF). TORL-3-600 was generated from a fully humanized CDH17 mAb by MMAE conjugation with a cleavable linker. Cell membrane staining of CDH17 in patient tumor microarrays (TMAs), cell line (CDX) and patient derived xenografts (PDX) was evaluated by IHC assay. Selective binding of the TORL-3-600 to CDH17 was confirmed in human cancer cell lines and cells engineered to overexpress CDH17. Binding of TORL-3-600 to cell surface CDH17 induced Internalization and translocation to the lysosome of the protein-ADC complex for release of the MMAE payload. Treatment with TORL-3-600 induced significant regressions and tumor growth inhibition (TGI) in four CDH17-positive (CDH17+) human colorectal cancer (CRC) CDXs (103.6 - 140.4% TGI) and three CDH17+ CRC PDXs (63.3 - 102.2% TGI). Responses in these models were sustained for up to nine-weeks following cessation of treatment. Sustained inhibition of xenograft tumor progression was also observed in a cell line model of CDH17+ pancreatic cancer (85.8% TGI). In contrast, greatly reduced responses (37.3 - 58.2% TGI) to TORL-3-600 were observed in the CDH17- human colon cancer CDX and PDX models. Each of the doses tested in this study were well tolerated in mice with no dose-limiting toxicities observed. Analyses of large human patient TMAs by CDH17 IHC assay demonstrated detectable expression of CDH17 in 90.1% (173/193) of CRC, 51.8% (86/166) of gastric and 20.4% (69/331) of pancreatic cancers. These numbers suggest that an ADC directed against CDH17 could provide benefit to a significant number of patients diagnosed with these cancers. These data support the clinical development of TORL-3-600 for the treatment of CDH17+ cancers. TORL-3-600 has completed IND enabling toxicity studies with acceptable PK and toxicity profiles and is now in phase 1 clinical testing (NCT05948826). Citation Format: Neil A. O'Brien, Martina SJ McDermott, Jun Zhang, Ming Lu, Ke Wei Gong, Benjamin Hoffstrom, Wei Ping Jia, Tong Luo, Athena M. Madrid, Min Liang, John A. Glaspy, Dennis J. Slamon. TORL-3-600, a novel antibody drug conjugate directed against cadherin 17 (CDH17), has preclinical efficacy in colorectal, gastric, and pancreatic cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1900.

Abstract 6067: Identification of selective CBP degraders with robust preclinical PK, PD, efficacy and safety across solid tumor indications

Abstract CREB binding protein (CBP) and E1A binding protein (EP300) are paralog histone acetyltransferases involved in many cellular processes via their activity as transcription factor co-activators. Dysregulation of one or both proteins has been implicated in various cancer types, and functional genomic screens have revealed a bidirectional synthetic lethal relationship between these two paralogs in tumor cells. Due to the high homology between CBP and EP300, identifying selective chemical matter that selectively disrupts the activity of CBP has proven challenging. Small molecule inhibitors targeting the HAT or bromodomain of CBP/EP300 have been developed, however these agents exhibit hematopoietic toxicity resulting from dual inhibition, which limits their therapeutic window. Herein, we describe the PK, PD, and efficacy of selective, potent CBP degraders across various EP300-mutant cancer xenograft models. Our results show deep and sustained CBP degradation, leading to significant tumor growth inhibition in solid tumors. This anti-tumor activity was not associated with significant body weight loss or hematopoietic toxicity. Our CBP-selective protein degraders have the potential to be a first-in-class therapeutic option for patients with tumors harboring EP300 mutations. Citation Format: Darshan Sappal, Ammar Adam, Hafiz Ahmad, Benjamin Adams, Ketaki Adhikari, Wesley Austin, Breanna Bullock, Julie Di Bernardo, Thomas Dixon, Danette Daniels, Claudia Dominici, GiNell Elliot, Brian Ethell, Anais Gervais, Md Imran Hossain, David Huang, Dave Lahr, Mei Yun Lin, David Mayhew, Karolina Mizeracka, Solymar Negretti, Tyler Nguyen, Olga Prifti, Shawn Schiller, Brenna Sherbanee, David Terry, Nihan Ucisik, Elizabeth Wittenborn, Qianhe Zhou, Mark Zimmerman, Laura La Bonte. Identification of selective CBP degraders with robust preclinical PK, PD, efficacy and safety across solid tumor indications [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6067.

Abstract 3142: NN3201, a novel c-Kit targeting ADC, exhibits robust preclinical anti-tumor efficacy in SCLC and GIST models

Abstract c-Kit (CD117) is a type III receptor tyrosine kinase (RTK), which is known to be activated upon binding to its cognate ligand stem cell factor (SCF) to induce critical signaling pathways involved in cell proliferation, survival, and differentiation. Indicative of poor prognosis, overexpression and activating mutations of c-Kit have been implicated in a variety of human cancers including small cell lung cancer (SCLC), gastrointestinal stromal tumors (GIST), and acute myelogenous leukemia (AML). While imatinib, a small molecule c-Kit inhibitor, has been a beneficial treatment for GIST, resistance eventually develops to the drug, moreover, shows limited efficacy in c-Kit overexpressing tumors such as SCLC. Herein, we developed NN3201, a novel c-Kit targeting antibody-drug conjugate (ADC), comprised of fully human 2G4 antibody with a picomolar binding affinity to c-Kit and cytotoxic monomethyl auristatin E (MMAE) as the payload. NN3201 displayed potent in vitro cytotoxicity in various wild-type and mutant c-Kit positive SCLC and GIST cell lines with IC50 in the nanomolar range. In addition, NN3201 was rapidly internalized and inhibited c-Kit-mediated signaling., NN3201 treatment resulted in the increased proportions of the sub G1 and G2/M in the c-Kit positive cancer cell lines, indicating that release of MMAE induced cell cycle arrest. Moreover, bystander effect was confirmed by co-culturing c-Kit high and negative cell lines. Most importantly, in mouse xenograft models, NN3201 showed a remarkable tumor growth inhibition of several wild type, mutant c-Kit positive, and imatinib resistant SCLC and GIST cell lines. Enhanced anti-tumor activity and delayed tumor growth were observed in an SOC-treated (etoposide and carboplatin) SCLC xenograft model, by NN3201 in comparison to second line SOC (topotecan or irinotecan). In the GLP study, repeated intravenous administration of NN3201 was well tolerated at all doses (0.5, 1, 2 mg/kg Q3Wx3) without unscheduled death. Dose-dependent, yet transient, cytotoxicity of NN3201 was observed in the bone marrow. We confirmed HNSTD (Highest Non-Severely Toxic Dose) of NN3201 to be 2 mg/kg through exploratory and GLP repeat dose toxicity studies as no serious irreversible toxicity was observed. Accumulating data suggest that NN3201 is a promising therapeutic alternative for the treatment of SCLC and GIST regardless of wild-type or activating mutations in c-Kit. Citation Format: Chansik Kim, Jin Gu Cho, TaeMin Wi, Jiwoo Moon, Han-Jik Ko, Jina Lee, Jin Woo Park, Yeonjy Lee, Sanghee Kim, Jin-Ock Kim, Jaeyoung Song, Sun-Hwa Lee, Sang Gyu Park. NN3201, a novel c-Kit targeting ADC, exhibits robust preclinical anti-tumor efficacy in SCLC and GIST models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3142.

Abstract 2726: A novel trispecific antibody HC010 targeting PD-1/CTLA-4/VEGF for the potential treatment in anti-PD-1 antibody resistant NSCLC patients

Abstract Background and Aim: Immune checkpoint inhibitors (anti-PD-1/CTLA-4 antibody) have been approved and widely used for the first line treatment of non-small cell lung cancer (NSCLC). However, most patients are experiencing resistant to PD-1 blockade. In recent clinical trials, anti-VEGF antibody has shown to improve the clinical outcomes of anti-PD-1 antibodies and overcome resistance to checkpoint blockade. We developed a PD-1/CTLA-4/VEGF trispecific antibody (HC010) by site-specifically fusing anti-PD-1 scFv and anti-CTLA-4 nanobody to the defined site of anti-VEGF antibody. The aim of this study was to evaluate the potential use of HC010 for treatment of anti-PD-1 antibody resistant NSCLC patients. Method: Humanized mice were established in NCG mice by reconstituting human PBMC before inoculating the PDX tissue, which was derived from a NSCLC patient treated with two cycles of an anti-PD-1 antibody sintilimab. When tumors were approx. 170mm3, mice were dosed with HC010 twice weekly for 3 weeks. Pembrolizumab, sintilimab and a Standard of Care (SoC) agent docetaxel were included as reference. For IHC analysis, tumor samples were harvested 24h post final dose and fixed with 10% NFB overnight and subsequently stained with CD31 and CD8 to explore the change in tumor microenvironment after HC010 treatment. For preclinical toxicity assessment, HC010 was intravenously administered once weekly for four weeks in naïve cynomolgus monkeys and immunogenicity/local tolerance/clinical pathology were evaluated during the dosing and recovery phase. Results: HC010 showed a significant tumor inhibition (TGI=81%) when compared with the vehicle control. Pembrolizumab and sintilimab alone exhibited limited anti-tumor effect. Docetaxel only showed a partial response during the dosing phase. By analyzing tumor samples, there was a significant increase in CD8+ positive T cells in HC010 treated tumors in contrast to the vehicle group and pembrolizumab/sintilimab treated groups, suggesting that HC010 can significantly improve CD8+ T cell infiltration. Expression of CD31 as an angiogenic and vasculogenic marker, was significantly reduced in HC010 treated tumors. In the toxicity study, HC010 at selected doses showed no obvious toxicity in cynomolgus monkeys. Conclusion: Our trispecific antibody HC010 targeting PD-1/CTLA-4/VEGF showed a superior anti-tumor effect in a sintilimab resistant PDX animal model when compared with pembrolizumab and sintilimab as well as SoC. By analyzing tumor microenvironment, HC010 overcame acquired resistance by modulating tumor microenvironment such as increase in intra-tumoral cytotoxic T cell infiltration and normalization of blood vessels. Together with preclinical efficacy and safety data, HC010 showed potential benefits in treatment of anti-PD-1 antibody resistant NSCLC patients. Citation Format: Diandong Jiang, Yue Xi, Chen Xu, Xingding Wang, Qiaoshan Yin, Zhaohui Li, Teddy Yang. A novel trispecific antibody HC010 targeting PD-1/CTLA-4/VEGF for the potential treatment in anti-PD-1 antibody resistant NSCLC patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2726.

Abstract 1902: ADRX-0706 Nectin-4 antibody-drug conjugate PK/PD characterization elucidates its widened therapeutic window

Abstract Nectin-4 is a well validated tumor target, which is highly expressed in several solid cancers, while expression in normal tissues is limited. A first-generation antibody-drug conjugate targeting Nectin-4, called enfortumab vedotin-ejfv (EV), was granted accelerated FDA approval in 2019 for urothelial cancers, and is currently approved for frontline therapy in cisplatin-ineligible patients with locally advanced or metastatic urothelial carcinoma, providing groundbreaking improvement in patient survival. However, clinical use of EV has also revealed safety-driven limitations, which result in reduced and/or interrupted drug exposures impacting efficacy. To overcome these limitations in therapeutic window, Adcentrx has developed ADRX-0706, a Nectin-4-targeting next-generation ADC with a drug-antibody ratio (DAR) of 8. ADRX-0706 utilizes a novel tubulin inhibitor payload AP052 with a proprietary cleavable linker utilizing Adcentrx’ proprietary i-ConjugationTM technology, which results in excellent biophysical features. Most noteworthy, ADRX-0706 displays a very stable PK profile with overlapping curves for total antibody and ADC as well as full DAR retention in circulation as determined by mass spectrometry. This translates to superior efficacy of ADRX-0706 over EV in multiple in vivo cancer cell line- and patient-derived xenograft mouse models across indications. Detailed PK/PD characterization of ADRX-0706 validates the mechanism of action as an anti-mitotic agent inducing cell cycle arrest and apoptosis. In addition, ADRX-0706 treatment leads to increased PD-L1 expression in mouse pharmacology models, which is a consequence of immunogenic cell death as described for this payload class. These findings are in line with emerging data on EV and provide rationale for combination regimens with checkpoint inhibitors. Besides the improvement in efficacy, ADRX-0706 was also designed for superior safety. A payload distribution study in tumor-bearing mice reveals a preferential and increased delivery of payload to tumors and lower payload delivery to normal tissues as well as lower free payload levels in plasma for ADRX-0706 compared to EV. Taken together, these data provide association of the improved drug-linker stability of ADRX-0706 to an improved Nectin-4 directed delivery of AP052 payload to the tumor and lower exposure in normal tissues, which may translate to an improved therapeutic window. In summary, the preclinical efficacy and safety properties of ADRX-0706 support clinical evaluation of this next generation anti-Nectin-4 ADC. ADRX-0706 is currently in a phase 1a/b study (NCT06036121). Citation Format: Maria Shahmoradgoli, Andrew Hau, Dong Jun Lee, Anna Wang, Peter P. Challita, Oscar Betancourt, Wes Sisson, Mario M. Kuo, Kris Zhang, Albert Goldson, Sam Janssen, Paul Datta, Felipe Acosta, Alexander Chu-Kung, Hui Li, Pia M. Challita-Eid, Sabine Rottmann. ADRX-0706 Nectin-4 antibody-drug conjugate PK/PD characterization elucidates its widened therapeutic window [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1902.

Abstract 2616: BCG033, a novel bispecific antibody-drug conjugate targeting PTK7 and TROP2, demonstrates preclinical efficacy against triple-negative breast cancer and other solid tumor xenografts

Abstract Metastatic triple-negative breast cancer (TNBC) patients have poor overall survival, highlighting the need for novel treatments. Although the TROP2-targeting ADC sacituzumab govitecan recently received accelerated approval from the FDA for the treatment of patients with metastatic TNBC, the on-target toxicity of this single-target agent has limited clinical efficacy. We sought to improve the specificity and efficacy of future TNBC-targeted therapies by generating a bispecific antibody-drug conjugate (bsADC) targeting TROP2 and PTK7, another tumor-associated antigen (TAA) that is highly expressed in TNBC and correlates with poor prognosis and metastatic disease. We previously generated fully human antibodies targeting PTK7 and TROP2 from Biocytogen’s fully human, common light chain antibody transgenic RenLite® mice, which were selected such that their monovalent antibodies exhibited reduced internalization profiles for improved tumor selectivity. These antibodies were then constructed into a bispecific antibody targeting PTK7 × TROP2, which demonstrated reactivity to human and cynomolgus monkey antigens and binding to multiple cancer cell lines, including TNBC, with high affinity. PTK7 × TROP2 bsAb also showed enhanced internalization in vitro compared with parental monovalent antibodies. Next, the PTK7 x TROP2 bsAb was conjugated to vcMMAE with a drug-to-antibody ratio (DAR) of 4 to generate a bsADC (BCG033). BCG033-vcMMAE demonstrated superior activity to benchmark and parental ADCs in a cell line-derived xenograft (CDX) TNBC model with low PTK7 expression. Here, we demonstrate that BCG033-vcMMAE ADCs also exhibited superior efficacy to benchmark ADCs in PDX models, including TNBC xenografts and NSCLC xenografts. We next tested the efficacy of the PTK7 x TROP2 bsAb conjugated to BLD1102, Biocytogen’s novel, proprietary linker/payload composed of a DNA Topo I inhibitor payload and a highly hydrophilic protease-cleavable linker, with a DAR of 8. BCG033-BLD1102 showed potent activity in a colorectal cancer PDX model in which benchmark ADCs were inactive, even at high doses. In summary, BCG033 conjugates demonstrate promising preclinical efficacy in vivo, which ultimately could provide a new treatment option for TNBC and other solid tumors expressing PTK7 and TROP2. Citation Format: Sufei Yao, Chengzhang Shang, Gao An, Chaoshe Guo, W. Frk an, Yi Yang. BCG033, a novel bispecific antibody-drug conjugate targeting PTK7 and TROP2, demonstrates preclinical efficacy against triple-negative breast cancer and other solid tumor xenografts [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2616.