Cytotoxic Payload Research Articles

Abstract 1767: A next generation site-specific ADC targeting breast and gastric cancer

Abstract Antibody drug conjugates are entering a renaissance period as a promising treatment option for a variety of cancers. Despite some success in the past few decades, developing effective ADCs remains a challenge due to extensive inefficiencies of industry standard conjugation technologies. Industry available methods can be limited by lack of site-specificity, inflexibility on the site of conjugation, and poor overall biophysical characteristics which can alter the efficacy, safety, and bioavailability of these therapeutics. BrickBio’s unique bioconjugation methodology enables precise (site-specific), flexible (offering numerous options for conjugation site and chemistry), efficient, and scalable generation of antibody-drug conjugates which overcome these limitations and achieve the full potential of this highly promising class of therapeutics. In this work, we incorporate an azide-containing UAAs (unnatural amino acid) into full-length antibodies targeting receptors overexpressed in breast and gastric cancer. Specifically, we have engineered variants of IgG1 antibodies to contain the aforementioned UAA, enabling site-specific attachment of cytotoxic payloads, such as auristatins, via click chemistry to generate ADCs with homogeneous DARs and at different conjugation sites. The resulting BrickADCs exhibit high therapeutic efficacy against receptor-positive cell lines, particularly lines expressing low levels of HER2, in vitro as well as in mouse xenograft models. Not only are the BrickADCs 100x more potent in demonstrated cell lines, but current research indicate that they have an improved safety profile over T-DM1. In other efforts, the BrickADC platform is leveraging a proprietary Modular Multisite Platform (MMP) to address the unmet need of eventual ADC resistance by conjugating multiple distinct payloads in a homogenous fashion. Continued preclinical work is underway for these pipeline candidates as well as investigation into other target areas. Citation Format: James Sebastian Italia, Nikos Biris, Zhi Li, Myer Hussain, John Boyce, Audrey Warner. A next generation site-specific ADC targeting breast and 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 1767.

Abstract 5331: Biological assessment of the virus-like drug conjugate AU-011 to specifically target a breadth of human cancer types

Abstract Introduction: AU-011 is a virus-like drug conjugate based on a human papillomavirus (HPV) derived virus-like particle (VLP) conjugated to a light-activated cytotoxic payload (IRDye700DX) currently in Phase II clinical trials for the treatment of primary choroidal melanoma. When activated by near-infrared light, AU-011 has a dual mechanism of action inducing rapid, tumor necrosis resulting in pro-immunogenic cell death and long-term anti-tumor immunity. HPV-derived VLPs bind a wide variety of tumor types via modified heparan sulfate proteoglycans (HSPG) found on the tumor surface. This study explores the breadth of tumor types that could benefit from a targeted treatment intervention with AU-011 and surveys genes and biological pathways that are positively and negatively associated with this targeting. Methods: AU-011 binding, cytotoxicity and HSPG specificity was surveyed in 127 tumor cell lines representing breast, cervical, CNS (glioblastoma, astrocytoma), colon, esophageal, gastric, hematopoietic, lung, liver, melanoma (cutaneous or choroidal), oropharyngeal, ovarian, pancreas, prostate, renal, urothelial and skin cancers, and sarcomas (osteosarcomas, mesotheliomas, retinoblastomas). Publicly available gene expression data for 101 of these cell lines was cross-referenced to identify gene signatures that correlated (either positively or negatively) with AU-011 binding and cytotoxicity. Results: AU-011 activity was observed for every tumor type examined, with some variation across several of the types. HSPG-specific binding was well-conserved across all tumor types tested except for most cells of lymphoid origin which are known to have HSPG deficiency. Collectively the tumor-derived cell lines exhibiting average binding EC50s < 100 pM were ocular cancers (choroidal melanomas and retinoblastomas) and solid tumors including urothelial, bone, breast, cervical, CNS, colon, cutaneous melanoma, esophageal, gastric, liver, lung, skin, oropharyngeal, ovarian, and renal. Urothelial, bone, breast, cervical, CNS, esophageal, gastric, liver, lung, melanoma, skin, ovarian, renal and retinoblastoma all exhibited AU-011 mediated cytotoxicity with an average potency of < 100pM. Correlative gene expression analysis demonstrated a strong association between AU-011 activity and genes involved in epithelial-to-mesenchymal transition, glycosaminoglycan biosynthesis/metabolism, and extracellular matrix interactions. Expression signatures for ribosomal activity and protein translation were negatively associated with AU-011 binding and activity. Conclusions: Collectively these data demonstrate the wide potential applicability of AU-011 to target a number of tumor types, particularly those derived from neural or epithelial lineages. Importantly, a large portion of these tumors are accessible making their AU-011 targeting clinically translatable. Citation Format: Rhonda C. Kines, Nathan R. Fons, Elisabet de los Pinos, John T. Schiller. Biological assessment of the virus-like drug conjugate AU-011 to specifically target a breadth of human cancer types [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 5331.

Abstract 1281: SGN-B7H4V shows immunomodulatory activity through induction of immunogenic cell death

Abstract SGN-B7H4V is a novel investigational antibody-drug conjugate composed of a B7-H4-directed human monoclonal antibody conjugated to the validated vedotin drug linker, which incorporates the microtubule disrupting agent monomethyl auristatin E (MMAE) via a protease-cleavable peptide linkage. This vedotin drug linker system has been clinically validated by multiple ADC programs, including brentuximab vedotin, enfortumab vedotin, tisotumab vedotin, and polatuzumab vedotin. B7-H4 is an immune checkpoint ligand with elevated expression on a variety of solid tumor types, including breast, ovarian, and endometrial tumors. SGN-B7H4V is designed to bind and internalize the B7-H4/ADC complex from the surface of malignant cells and release the cytotoxic payload MMAE. The antitumor activity of SGN-B7H4V may be multimodal as SGN-B7H4V can induce tumor cell death through several mechanisms, including MMAE-mediated direct cytotoxicity and bystander killing as well as antibody-mediated functions including antibody-dependent cellular cytotoxicity (ADCC) and phagocytosis (ADCP). Previously, vedotin ADCs have been described to elicit antitumor immune responses in part through induction of immunogenic cell death (ICD) mediated by the MMAE payload. These immunomodulatory effects potentially position vedotin ADCs to uniquely synergize with checkpoint inhibitors, supported by recent clinical activity observed when vedotin ADCs are paired with anti-PD1 agents. Here, we characterize SGN-B7H4V-mediated ICD and subsequent immunomodulatory activity. We also evaluate the contribution of SGN-B7H4V-induced immune activation to antitumor activity in combination with an anti-PD1 agent in an immunocompetent mouse model. In vitro, tumor cells treated with SGN-B7H4V showed several hallmarks of immunogenic cell death, including calreticulin exposure and release of ATP. In vivo, treatment of B7-H4-expressing tumors with SGN-B7H4V led to immune changes in the tumor microenvironment, including recruitment of macrophages and T cells. Finally, SGN-B7H4V drove robust, curative activity in an immunocompetent tumor model as a monotherapy and paired well with an anti-PD1 agent. Altogether, these data support the evaluation of SGN-B7H4V as a monotherapy in a first-in-human phase 1 clinical study and potential future clinical combinations with immunotherapies. Citation Format: Elizabeth E. Gray, Michelle Ulrich, Angela Epp, Patrick Younan, Kelly Hensley, Sean Allred, Julie Hahn, Kristen Gahnberg, Piper M. Treuting, John J. Gosink, Robert Thurman, Alyson J. Smith, Jason Schrum, Natalya Nazarenko, Shyra J. Gardai. SGN-B7H4V shows immunomodulatory activity through induction of immunogenic cell death [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 1281.

Abstract 5616: Tumor-targeted immune activation via a site-specific TLR7-agonist antibody-drug conjugate

Abstract Traditional antibody-drug conjugates (ADCs) selectively deliver cytotoxic payloads to tumor-associated antigen (TAA)-expressing tumor cells, thereby limiting healthy cell damage and toxicities associated with systemic administration. Analogously, a novel class of immune-stimulating antibody conjugates (ISACs) has recently emerged to achieve tumor-targeted activation of anti-tumor immune responses, avoiding dose-limiting immunotoxicities seen with the systemic immune agonist delivery. Most of the ADC or ISAC to date utilize random payload conjugation to native surface-exposed lysines or cysteines, and relatively labile linkage chemistries, leading to conjugation site and drug-to-antibody ratio (DAR) heterogeneity, and ADC/ISAC instability in systemic circulation. In particular, the presence of high-DAR species and linker instability can lead to off-tumor toxicity, thus limiting the therapeutic window. Here we describe the generation and preclinical characterization of a site-specific TLR7-agonist (TLR7a) ISAC targeting an undisclosed TAA1. To specify the conjugation site and DAR, a non-natural amino acid (nnAA), para-acetyl-L-phenylalanine (pAF) was genetically incorporated at defined sites within the anti-TAA1 antibody, providing an orthogonal chemical handle for covalent TLR7 agonist payload conjugation through a highly stable oxime bond. Using this site-specific, homogenous ISAC platform, we systematically screened different conjugate sites and TLR7 agonist payloads to obtain an optimized TAA1-TLR7a ISAC drug candidate. ISAC platform stability, homogeneity, and flexibility were critical, because conjugation site and payload structure dramatically influenced ISAC in vitro activity, PK profile and in vivo efficacy. Using in vitro co-culture assays with human immune cells and tumor cell lines, we showed that the optimized TAA1 ISAC can induce multiple anti-tumor immune mechanisms, including proinflammatory cytokine production, the myeloid cell activation markers induction and enhanced ADCC mediated tumor cell killing. The TAA1 ISAC is 100-fold more active than the free, unconjugated TLR7 agonist, and all activity is conditional on the presence of TAA1-expressing tumor cells. Finally, we demonstrated in vivo efficacy in both xenograft and syngeneic tumor models. In a syngeneic MC38-tumor model expressing human TAA1, ISAC treatment led to complete tumor regression and formation of immunologic memory. These results provide a strong rationale for site-specific TLR7 agonist ISAC as a next generation platform for tumor-targeted, innate immune agonist immunotherapy. Citation Format: Mingchao Kang, Sung-Ju Moon, Ji Young Kim, Andy Beck, Molly Allen, Jay Nelson, Keith Tatsukawa, Hon Tran, Manoj Pal, Michael Gray, Nick Knudsen, Lillian Skidmore, David Mills, Yingchun Lu, Ying Buechler, Sukumar Sakamuri, Shawn Zhang, Feng Tian. Tumor-targeted immune activation via a site-specific TLR7-agonist antibody-drug conjugate [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 5616.

Abstract 2016: Preclinical evaluation of uPARAP (MRC2) antibody-drug conjugates (ADCE-003,010,011) in osteosarcoma pdx models

Abstract Introduction: Antibody-drug Conjugates (ADCs) targeting differentially expressed tumor cell-surface antigens show robust clinical activity in several solid tumor cancers, but none is yet available for osteosarcoma. Due to the high unmet medical need in this indication, there is an urgent requirement to identify respective osteosarcoma cell-surface antigens and evaluate the antitumor activity of an ADC that can deliver tailored cytotoxic payloads to osteosarcoma tumors expressing these targets. Methods: We used an integrated proteomic and transcriptomic surfaceome profiling approach to identify cell-surface proteins that are highly expressed in osteosarcoma but minimally expressed on normal tissues. uPARAP (MRC2) was found to be enriched in osteosarcoma at both protein and mRNA levels. The cell-surface expression of uPARAP (MRC2) was further validated by IHC and flow cytometry with osteosarcoma cell lines, PDX models, and patient tumor tissue microarray. As a proof of concept, three MRC2 targeted ADCs with different Microtubulin- and alkylating agent types of payloads were tested in 8 osteosarcoma PDX models. uPARAP (MRC2) ADC, control ADC, or vehicle control was administered IV to mice harboring flank tumors at a dose of 3mg/kg, weekly X 3 (ADCE-003), 2mg/kg on Day 1 (ADCE-010), and 10mg/kg weekly X 2 (ADCE-011). EFS for treatment (T) and control (C) groups, minimum relative tumor volume (minRTV), and objective response measures were analyzed. Results: Western blotting confirmed the expression of uPARAP (MRC2) in 8 osteosarcoma cell lines and 8 PDX models. Flow cytometry further validated cell-surface localization and expression levels of uPARAP (MRC2) in 7 osteosarcoma cell lines. We then performed immunohistochemistry (IHC) staining using an osteosarcoma tissue microarray from 37 patients and 19 PDX models. uPARAP (MRC2) was expressed in 97% of the patient samples and 95% of the PDXs. 51% of the patient samples and 39% of the PDXs had an overall H-score of 100 or higher. Mice tolerated ADCs well with minimal toxicity. All 3 ADCs significantly prolonged EFS in 6/8 osteosarcoma models. Complete response (CR) or maintained CR were observed in 2 models in ADCE-010 and ADCE-011 groups, respectively. Conclusions: uPARAP (MRC2) is highly expressed in most osteosarcoma samples, which makes it a viable target for respective antigen targeting ADC therapies. Three uPARAP (MRC2) targeting ADCs showed antitumor activities in osteosarcoma preclinical models which warrant further investigation of uPARAP targeting ADC therapies for osteosarcoma. Citation Format: Yifei Wang, Wendong Zhang, Zhongting Zhang, Xiangjun Tian, Rossana Lazcano, Pooja Hingorani, Michael Roth, Jonathan Gill, Douglas Harrison, Zhaohui Xu, Jing Wang, Niels Behrendt, Christoffer F. Nielsen, Lars H. Engelholm, Richard Gorlick. Preclinical evaluation of uPARAP (MRC2) antibody-drug conjugates (ADCE-003,010,011) in osteosarcoma pdx models [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 2016.

Abstract 5284: M1231 is a bispecific anti-MUC1xEGFR antibody-drug conjugate designed to treat solid tumors with MUC1 and EGFR co-expression

Abstract Mucin 1 (MUC1) and epidermal growth factor receptor (EGFR) are co-expressed at high prevalence in multiple cancer indications such as non-small cell lung cancer (NSCLC), esophageal squamous cell carcinoma (ESCC), head and neck squamous cell carcinoma, triple negative breast cancer and ovarian cancer. Tumor-associated MUC1 is hypoglycosylated and exposes peptide epitopes within its extracellular domain, which are not accessible to antibodies in normal epithelial tissue. MUC1 co-localizes with EGFR as a result of loss of cell polarity in tumor cells. M1231 is a bispecific antibody-drug conjugate (ADC) based on a SEED (strand-exchange engineered domain)-antibody scaffold targeting tumor-associated MUC1 and EGFR. Sutro Biopharma’s cell free expression system Xpress CF+™ enables incorporation of non-natural amino acids at precise positions in the SEED-antibody for site-specific linker-payload conjugation. The cytotoxic payload of M1231 (SC209) is a hemiasterlin-related microtubule inhibitor. The cleavable linker (ValCit-PABA) maintained ADC stability in human plasma in vitro, ensuring low systemic payload release. Pre-clinical activity of M1231 was assessed in vitro in cancer cell lines and in vivo in NSCLC and ESCC patient-derived xenograft (PDX) models. M1231 inhibited tumor cell viability in vitro at sub-nanomolar IC50 values. The bispecific MUC1xEGFR antibody has demonstrated superior internalization and lysosomal trafficking compared to monospecific bivalent antibodies. Efficient ADC uptake resulted in superior antitumor activity of M1231 in PDX models compared to monospecific bivalent ADCs. M1231 demonstrated durable and dose-dependent antitumor activity in PDX models. Strong antitumor activity with complete regression was observed in NSCLC and ESCC PDX models following a single treatment of M1231. M1231 antitumor activity was associated with high target expression in NSCLC PDX models and was observed across a range of target expression levels in ESCC models. In summary, efficient payload delivery to tumor cells and strong antitumor activity of M1231 indicate that M1231 may have the potential to deliver an efficacy benefit to patients with tumors co-expressing MUC1 and EGFR. Citation Format: Christine Knuehl, Lars Toleikis, Julia Dotterweich, Jianguo Ma, Seema Kumar, Edith Ross, Claudia Wilm, Martina Schmitt, Hans Juergen Grote, Christiane Amendt. M1231 is a bispecific anti-MUC1xEGFR antibody-drug conjugate designed to treat solid tumors with MUC1 and EGFR co-expression [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 5284.

Abstract 388: AI/ML-driven discovery of a novel proteoglycan for precision targeting of ADCs for disruption of stromal barriers and direct anti-tumor activity

Abstract Background: While checkpoint inhibitors (CPIs) such as anti-CTLA-4 and anti-PD-1/L1 have demonstrated efficacy in a number of solid tumor indications, those with high stromal presence have been difficult to treat with minimal response observed. We aimed to use a proprietary machine learning/artificial intelligence platform to identify novel stromal targets to relieve this immunosuppressive barrier and increase CPI responsiveness in difficult to treat indications. Methods: Based on bioinformatic analysis using our single cell RNA atlas, we assessed cancer-associated fibroblasts (CAFs)/fibroblastic cells in cancer tissue for identification of novel targets, including proteoglycans. Antibodies were generated by immunization of humanized mice, and lead antibodies were tested for activity in inhibiting cell adhesion and were further characterized for staining of both CAFs as well as tumor cells. ADCs were developed and tested in vitro for selective tumor cell killing. Results: Bioinformatic analysis identified a unique subset of cancer-associated fibroblasts, termed ecmCAFs, which demonstrated selective expression of Collagen Triple Helix Repeat Containing 1 (CTHRC1). This highly-selective expression pattern suggests it may be ideal as a target for alternative modalities, including ADC targeting or specific T cell activation. In addition, we identified that in certain tumor types, such a triple negative breast cancer and pancreatic ductal adenocarcinoma (PDAC), CTHRC1 is also highly expressed by cancer cells within the tumor and shows a more favorable expression profile for ADC targeting when compared to other stromal proteins such as FAP and LRRC15. We have confirmed surface expression and binding of CTHRC1 by our lead antibodies and have observed robust internalization on both human and mouse cancer cell lines. In vitro killing of tumor cells by ADCs and in vivo PD and efficacy will be presented on both ADCs and naked antibodies. Conclusions: We have identified CTHRC1 as a novel proteoglycan expressed by both ecmCAFs and tumor cells that appears to be an ideal target for both direct inhibition of stromal barrier function as well as targeting of cytotoxic payloads as an ADC. CTHRC1 expression is more selective than the classical markers FAP and LRRC15, both of which have been previously developed as ADCs. Citation Format: Elizabeth Koch, Max London, Amy Berkley, Allison Nixon, Sean Phippen, Kerry White, Amanda Hanson, Samuel Cooper, Christopher Harvey, Michael Briskin. AI/ML-driven discovery of a novel proteoglycan for precision targeting of ADCs for disruption of stromal barriers and direct anti-tumor activity [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 388.

Joint Disposition Properties and Comprehensive Pharmacokinetic Characterization of Antibody–Drug Conjugates

Antibody–drug conjugates (ADCs) comprise 3 distinct parts: a specific antibody carrier (mAb), a linker, and a cytotoxic payload. Typical pharmacokinetic (PK) characterization of ADCs remains fragmented using separate noncompartmental analyses (NCA) of individual analytes, offering little insight into the dynamic relationships among the ADC components, and the safety and efficacy implications. As a result, it is exceedingly difficult to compare ADCs in terms of favorable PK characteristics. Therefore, there is a need for characterizing ADCs using the joint disposition properties critical for understanding the fate of an ADC complex and clinical implications. In this communication, we describe 3 joint disposition metrics (JDMs) for integrated NCA of ADCs based on a combination of common analytes of ADC, payload, conjugated payload, and total mAb. These JDMs were derived, each in a simple form of a ratio between appropriate PK parameters of two analytes, from the presumed drug delivery scheme behind typical ADC designs, in terms of (1) linker stability, (2) therapeutic exposure ratio, and (3) effective drug-to-antibody ratio in vivo. The validity of the JDM-based PK characterization was examined against model-based analyses via their applications to 3 clinical candidates: PF-06650808, PF-06647020, and PF-06664178. For instance, the linker stability estimates for PF-06650808, PF-06647020, and PF-06664178 were 0.31, 0.14, and 0.096, respectively, from the JDM-based analyses vs. 0.23, 0.11, and 0.086 by the model-based approach. Additionally, the JDMs were estimated for a number of FDA-approved or otherwise well-documented ADCs, showing their utilities in comparing ADCs in terms of favorable PK characteristics.Graphical

EVOKE-01: A phase 3 study of sacituzumab govitecan (SG) versus docetaxel in patients with non–small cell lung cancer (NSCLC) progressing on or after platinum-based chemotherapy and checkpoint inhibitors.

TPS9149 Background: Single-agent chemotherapy, such as docetaxel, is the standard of care in patients with metastatic NSCLC who progressed on platinum-based therapy and checkpoint inhibitors. However, docetaxel is associated with poor survival (median overall survival [OS] of < 1 year); thus, novel agents are needed to further improve outcomes in this setting. SG is an antibody-drug conjugate composed of an anti–Trop-2 antibody coupled to the cytotoxic SN-38 payload via a proprietary, hydrolyzable linker. In a single-arm expansion of the phase 1/2 IMMU-132-01 basket study of advanced epithelial cancers (NCT01631552), SG demonstrated an objective response rate (ORR) of 17% and median OS of 9.5 months, with a manageable safety profile in 54 patients with metastatic NSCLC who had multiple prior therapies (Heist RS, et al. J Clin Oncol. 2017). EVOKE-01 randomized phase 3 study was designed to further evaluate SG in patients with metastatic NSCLC. Methods: EVOKE-01 (NCT05089734) is an open-label, global, multicenter, randomized, phase 3 study comparing the efficacy and safety of SG vs docetaxel in patients with metastatic NSCLC. Key eligibility criteria include age ≥18 years, pathologically documented stage IV NSCLC at time of study entry, and progression after platinum-based chemotherapy and anti-PD(L)1 therapy given either in combination or sequentially. Patients with EGFR, ALK, or other known actionable genomic alterations must have also received treatment with ≥1 approved appropriate TKI. Other inclusion criteria are ECOG performance status 0-1 and adequate hematologic, hepatic, and renal function. Patients with prior treatment with topoisomerase inhibitors are excluded. Patients are randomized 1:1 to receive intravenous SG (10 mg/kg on day 1 and 8) or docetaxel (75 mg/m2 on day 1) in 21-day cycles until progressive disease or unacceptable toxicity. Stratification is based on predominant histology (squamous vs nonsquamous), best response to prior immune therapy (PD/SD vs CR/PR), and prior therapy for actionable genomic alteration (yes vs no). The primary endpoint is OS. Key secondary endpoints include progression-free survival, ORR, duration of response, and disease control rate, as assessed by investigator RECIST v1.1, mean change from baseline in NSCLC-SAQ total score and shortness of breath, and safety. This study plans to enroll ̃520 patients globally and is open for recruitment. Clinical trial information: NCT05089734.

Exposure-response analyses of sacituzumab govitecan (SG) efficacy and safety in patients (pts) with metastatic triple-negative breast cancer (mTNBC).

1076 Background: SG is an antibody-drug conjugate composed of an anti–Trop-2 antibody coupled to the cytotoxic SN-38 payload via a proprietary, hydrolyzable linker. SG is approved for pts with mTNBC who received ≥2 prior chemotherapies (> 1 in the metastatic setting). The relationships between exposure of SG, free SN-38, and total antibody (tAB) following SG administration and its efficacy and safety outcomes were evaluated in pts with mTNBC. Methods: Available exposure efficacy and safety outcomes from the mTNBC cohort of the phase 1/2 IMMU-132-01 study (relapsed/refractory pts; n = 24) and mTNBC pts from the phase 3 ASCENT study who had received ≥2 prior therapies (> 1 in the metastatic setting; n = 253) were analyzed. Pts in IMMU-132-01 received 8 or 10 mg/kg SG and pts in ASCENT received 10 mg/kg SG on d1 and d8, of every 21d cycle. Effect of exposure on CR, ORR and the evaluated adverse events (AEs) of vomiting, diarrhea, hypersensitivity reactions, nausea, and neutropenia were analyzed using logistic (CR, ORR) or ordinal logistic (AE) regression models while OS, PFS, time to first dose reduction and time to first dose delay were analyzed using Cox PH models. Several exposure metrics related to the PK of SG, free SN-38, and tAB were evaluated as predictors of SG efficacy and safety and the most statistically significant exposure metric was retained in the model; effect of other covariates was characterized within the modeling framework. Results: Higher values of the average exposure over the treatment duration (CAVG) for SG (CAVGSG) were significantly associated with an increase in the probability of CR and ORR and higher CAVG values for tAB (CAVGtAB) were significantly associated with longer OS and PFS. The probability of Grade ≥1 evaluated AEs, the risk of dose reductions and dose delays were found to increase significantly with increasing CAVGSG. Neutropenia was the only AE where the effect of exposure was significantly associated with the probability of Grade ≥3 evaluated AEs. No statistically significant associations between exposure and the probability of Grade 4 AEs were observed for any of the evaluated endpoints. The developed models were used to estimate the efficacy and safety outcomes for the 8 mg/kg vs 10 mg/kg SG dose levels and the results indicated a more favorable risk/benefit profile for the 10 mg/kg dose level driven by the higher estimated efficacy. Baseline Trop-2 expression level was not statistically correlated with magnitude of clinical response based on the limited available Trop-2 data. Conclusions: Exposure-response relationships were observed for all evaluated efficacy and safety endpoints for SG in patients with mTNBC, and the higher efficacy (as assessed by CR, ORR, OS and PFS) achieved with the exposures associated with the 10 mg/kg SG dose regimen and its manageable safety profile support the appropriateness of the approved regimen of SG. Clinical trial information: NCT02574455, NCT01631552.

EVOKE-02: A phase 2 study of sacituzumab govitecan (SG) plus pembrolizumab (pembro) with or without platinum chemotherapy in first-line metastatic non–small cell lung cancer (NSCLC).

TPS9146 Background: Most patients (pts) with advanced NSCLC do not harbor genomic alterations associated with approved first-line targeted therapies. The standard of care for these pts is a programmed death (ligand)-1 (PD-[L]1) inhibitor alone, if the tumor highly expresses PD-L1, or in combination with platinum doublet chemotherapy, independent of PD-L1 expression. However, most pts do not respond to these therapies or achieve only a transient response, highlighting an unmet need. SG is an antibody-drug conjugate composed of an anti–Trop-2 antibody coupled to the cytotoxic SN-38 payload via a proprietary, hydrolyzable linker. In the phase 1/2 IMMU-132-01 basket study (NCT01631552), SG demonstrated an objective response rate (ORR) of 17% and median overall survival (OS) of 9.5 mo, with a manageable safety profile in 54 pts with metastatic NSCLC after multiple prior therapies (Heist RS, et al. J Clin Oncol. 2017). We hypothesize that combining SG with pembro or with pembro + platinum chemotherapy will improve outcomes for pts with advanced NSCLC. Methods: EVOKE-02 (NCT05186974) is an open-label, multicenter, multicohort, global phase 2 study evaluating SG plus pembro with or without carboplatin (carbo) or cisplatin (cis) in advanced NSCLC. Key eligibility criteria include age ≥18 y, stage IV NSCLC at enrollment, measurable disease by RECIST v1.1, ECOG performance status of 0 or 1, and adequate organ function. Pts must not have actionable genomic alterations and must not have received prior systemic therapy for metastatic NSCLC. Up to 164 pts will be enrolled. SG plus pembro will be assessed in squamous/nonsquamous NSCLC with Tumor Proportion Score (TPS) ≥50% (cohort A, ̃30 pts) and TPS < 50% (cohort B, ̃30 pts), and SG plus pembro with carbo/cis in nonsquamous (cohort C, ̃40 pts) and squamous (cohort D, ̃40 pts) NSCLC regardless of PD-L1 expression. Pts are randomly assigned if cohorts enrolling concurrently have overlapping eligibility. SG will be administered intravenously (IV) at 10 mg/kg on d 1 and 8 until disease progression or unacceptable toxicity, pembro 200 mg IV on d 1 for up to 35 cycles, carbo AUC 5 or cis 75 mg/m2 on d 1 for up to 4 cycles in 21-d cycles. A safety run-in will be conducted for cohorts C and D (up to 24 pts each) to determine the optimal SG dose by dose de-escalation. Choice of platinum will be based on preliminary efficacy in safety run-in. The primary endpoints are ORR assessed by independent review per RECIST v1.1 and the incidence of dose-limiting toxicities per dose for the first 21 d of the safety run-in to determine the recommended phase 2 dose of SG in combination with pembro and a platinum. Key secondary endpoints include progression-free survival by independent review, OS, duration of response, disease control rate, and safety. This study is open for recruitment and is enrolling globally. Clinical trial information: NCT05186974.

Sacituzumab govitecan (SG) versus treatment of physician’s choice (TPC) in patients (pts) with previously treated, metastatic triple-negative breast cancer (mTNBC): Final results from the phase 3 ASCENT study.

1071 Background: Treatment goals for pts with metastatic breast cancer include extended survival and improved quality of life (QoL). SG is an antibody-drug conjugate composed of an anti–Trop-2 antibody coupled to the cytotoxic SN-38 payload via a proprietary, hydrolyzable linker. SG received FDA approval for pts with mTNBC who received ≥2 prior chemotherapies (at least 1 in the metastatic setting). In the pivotal phase 3 ASCENT study (NCT02574455), SG demonstrated a significant survival benefit over single-agent chemotherapy TPC in the primary analysis population of pts with second line or greater (2L+) mTNBC without known brain metastases at baseline (Bardia A et al. NEJM 2021) and QoL (Loibl S. et al. ESMO 2021). With additional follow up, we present the final data on efficacy, including overall survival (OS), safety, and QoL. Methods: Pts with mTNBC refractory or relapsing after ≥2 prior chemotherapies with at least 1 in the metastatic setting were randomized 1:1 to receive SG (10 mg/kg IV on days 1 and 8, every 21 days) or TPC (capecitabine, eribulin, vinorelbine, or gemcitabine) until disease progression or unacceptable toxicity. Primary endpoint was progression-free survival (PFS) per RECIST 1.1 by independent review in pts without known brain metastases at baseline. Key secondary endpoints included OS, safety, and health-related QoL. Safety was analyzed in pts who received ≥1 dose of study drug. Results: Of 529 pts enrolled, 468 did not have known brain metastases at baseline (median age: 54 y [range, 27-82]; median prior lines: 4 [range, 2-17]). As of Feb 25, 2021 (final database lock), SG (n = 235) vs TPC (n = 233) significantly improved median PFS (5.6 vs 1.7 mo; HR: 0.39; P< 0.0001) and median OS (12.1 vs 6.7 mo; HR: 0.48; P< 0.0001). The OS rate at 24 months was 22.4% (95% CI, 16.8-28.5) in the SG arm and 5.2% (95% CI, 2.5-9.4) in the TPC arm. In the safety population (n = 482), key treatment-related grade ≥3 adverse events with SG (n = 258) vs TPC (n = 224) were diarrhea (11% vs 0.4%), neutropenia (52% vs 33%), anemia (8% vs 5%), and febrile neutropenia (6% vs 2%). There was no grade ≥3 neuropathy and 1 case of grade 3 interstitial lung disease reported with SG. No patient experienced a treatment-related death with SG, and there was 1 treatment-related death with TPC due to neutropenic sepsis. Treatment discontinuations due to AEs were ≤3% in both arms. SG arm showed clinically meaningful and statistically significant improvements than the TPC arm in scores for all five primary focus health-related QoL domains. Conclusions: The analysis based on the final database lock of ASCENT confirms the superior survival outcomes of SG over single-agent chemotherapy, with a manageable safety profile and improvement in QoL for pts with mTNBC in the 2L+ setting. These findings reinforce SG as an effective treatment option for this pt population. Clinical trial information: NCT02574455.

Caspase-3 mediated switch therapy of self-triggered and long-acting prodrugs for metastatic TNBC.

Triple-negative breast cancer (TNBC) is characterized by its highly heterogeneous microenvironment and propensity for aggressive behavior, both of which represent, along with poor prognosis and high incidence of relapse, the main challenges of curing the disease. Although recent progress in targeted chemotherapy combinations has shown promising outcomes, conventional targeted chemotherapeutic approaches have relied on exploiting the expression of certain molecules or proteins overexpressed on cancer cells as drug targets, which have demonstrated limited clinical benefit against metastatic cancers. Here, we describe a tumoral caspase-3 mediated peptide-doxorubicin conjugates (PDC) switch therapy that adopts two different caspase-3 cleavable PDCs, RGDEVD-DOX (TPD1) and EMC-KGDEVD-DOX (MPD1), for targeting metastatic triple-negative breast cancer (mTNBC). First, using TPD1, an integrin αVβ3 based targeted strategy was utilized to target tumor cells or tumor vasculature associated with the highly malignant progression of mTNBC. TPD1 triggered the tumor cell-specific initial apoptosis and the induction of caspase-3 expression in the target tumor site. Then MPD1 was administered sequentially, which is an albumin-binding prodrug, and activated by induced caspase-3 in order to maintain the tumoral caspase-3 level and release the cytotoxic payload. The PDC switch therapy markedly accumulated doxorubicin in the tumor site and augmented tumor-specific in situ amplification of apoptosis. Importantly, the PDC switch therapy exerted a bystander killing effect on the neighboring cancer cells thus demonstrating potent therapeutic efficacy against both local and metastatic cancers. Given the limited therapeutic outcomes with conventional targeted therapies, our strategy of regulating the expression of caspase-3 level as a drug target could provide as a more durable and effective alternative in the treatment of highly heterogeneous mTNBC.

A next generation site-specific ADC targeting breast and gastric cancer.

e15024 Background: Antibody drug conjugates are entering a renaissance period as a promising treatment option for a variety of cancers. Despite some success in the past few decades, developing effective ADCs remains a challenge due to extensive inefficiencies of industry standard conjugation technologies. Industry available methods can be limited by lack of site-specificity, inflexibility on the site of conjugation, and poor overall biophysical characteristics which can alter the efficacy, safety, and bioavailability of these therapeutics. BrickBio’s unique bioconjugation methodology enables precise (site-specific), flexible (offering numerous options for conjugation site and chemistry), efficient, and scalable generation of antibody-drug conjugates which overcome these limitations and achieve the full potential of this highly promising class of therapeutics. Methods: In this work, we incorporate an azide-containing UAA (unnatural amino acid) into full-length antibodies targeting receptors overexpressed in breast and gastric cancer. Specifically, we have engineered variants of IgG1 antibodies to contain the aforementioned UAA, enabling site-specific attachment of cytotoxic payloads, such as auristatins, via click chemistry to generate ADCs with homogeneous DARs. Results: The resulting BrickADCs exhibit high therapeutic efficacy against receptor-positive cell lines, particularly lines expressing low levels of HER2, in vitro as well as in mouse xenograft models. Not only are the BrickADCs 100x more potent in demonstrated cell lines, but current research indicate that they have an improved safety profile over T-DM1 and extended half-life. Conclusions: It is conclusive that the BrickADC platform enables an increased therapeutic window. In other efforts, the BrickADC platform is leveraging a new Modular Multisite Platform to address the unmet need of eventual ADC resistance by conjugating multiple distinct payloads in a homogenous fashion. Continued preclinical work is underway for these pipeline candidates as well as investigation into other target areas.

Phase 1/1b study of telisotuzumab vedotin (Teliso-V) + osimertinib (Osi), after failure on prior Osi, in patients with advanced, c-Met overexpressing, EGFR-mutated non-small cell lung cancer (NSCLC).

9013 Background: Osi (third-generation tyrosine kinase inhibitor) is a standard frontline treatment (Tx) for advanced/metastatic EGFR-mutated NSCLC. However, tumors invariably progress after an initial response, with c-Met protein overexpression (OE) often associated with acquired resistance. Second- and third-line Tx options are limited to chemotherapy-based regimens with limited efficacy and significant toxicities. Teliso-V (ABBV-399), an anti–c-Met antibody-drug conjugate, delivers a cytotoxic payload (monomethyl auristatin E) into c-Met OE tumor cells. In a phase 1/1b study (NCT02099058) in patients (pts) with c-Met OE NSCLC, Teliso-V alone or in combination with erlotinib demonstrated an acceptable safety profile and antitumor activity. Interim safety and efficacy data from the Teliso-V + Osi cohort (arm E) of this trial are presented. Methods: Pts (≥18 yr) with metastatic EGFR-mutated, c-Met OE (by central immunohistochemistry) NSCLC who had progressed on a prior Osi regimen were eligible. Pts received Teliso-V (IV Q2W) + Osi (oral; 80 mg QD). Teliso-V was evaluated at 1.6 mg/kg and, after review of safety data, escalated to 1.9 mg/kg (safety evaluation). An expansion cohort was opened at 1.9 mg/kg for pts who had received ≤2 prior lines of systemic therapy. Pharmacokinetics (PK) were assessed throughout the study. Pts received study Tx until disease progression, unacceptable toxicity, or for up to 24 months. Results: As of 20 Dec 2021, 25 pts received Teliso-V (1.6 mg/kg, n = 7; 1.9 mg/kg, n = 18) + Osi. Median age was 60.0 yr; 14 (58%) pts were on prior Tx with Osi for > 12 mo. No dose-limiting toxicities (grade [Gr] ≥3 non-hematologic or Gr 4 hematologic Tx-related adverse events [AEs]) were reported during the safety lead-in or evaluation phases. All-Gr AEs considered possibly related to Teliso-V occurred in 22/25 (88%) pts: the most common (≥20%) were peripheral sensory neuropathy (36%), nausea, and peripheral edema (20% each); Gr ≥3 AEs (> 5%) were anemia (12%) and peripheral motor neuropathy (8%). No Gr 5 events related to Tx were reported. PK of Teliso-V + Osi was similar to single-agent Teliso-V. Efficacy data (19/25 pts) are in the table. The overall objective response rate (ORR) was 58% (67% at 1.9 mg/kg). Conclusions: Teliso-V + Osi is well tolerated with an ORR of 58% (67% at 1.9 mg/kg) in pts with c-Met OE NSCLC who progressed on prior Osi. Clinical trial information: NCT02099058. [Table: see text]

Feedback amplification of senolysis using caspase-3-cleavable peptide-doxorubicin conjugate and 2DG.

Therapy-induced senescence (TIS), a common outcome of current cancer therapy, is a known cause of late recurrence and metastasis and thus its eradication is crucial for therapy success. In this study, we introduced a conceptually novel strategy combining radiation-induced apoptosis-targeted chemotherapy (RIATC) with an effective glycolysis inhibitor, 2-deoxy-d-glucose (2DG) to target TIS. RIATC releases cytotoxic payload by amplification, continually increasing TIS, and this can be targeted by 2DG that stimulates an intrinsic apoptotic pathway in senescent cells, the senolysis; the senolytic 2DG also sensitizes cancer cells to chemo/radiation treatment. Anti-tumor efficacy of RIATC was investigated in numerous tumor models, and various cancer types were screened for TIS. Furthermore, in vitro evaluations of molecular markers of senescence, such as senescence-associated β-galactosidase (SA-β-Gal) assay, were performed to confirm that TIS was induced by RIATC therapy in MCF-7 cells. The combination therapy with 2DG proved to be effective in MCF-7 tumor-bearing mice that demonstrated feedback amplification of senolysis and successful inhibition of tumor growth. Our findings suggest that RIATC, when given together with 2DG, can overcome therapy-induced senescence and this combination is a promising strategy that enhances the therapeutic benefit of anti-cancer cytotoxic therapy.

Enzymatic glycan remodeling–metal free click (GlycoConnect™) provides homogenous antibody-drug conjugates with improved stability and therapeutic index without sequence engineering

ABSTRACT Antibody-drug conjugates (ADCs) are increasingly powerful medicines for targeted cancer therapy. Inspired by the trend to further improve their therapeutic index by generation of homogenous ADCs, we report here how the clinical-stage GlycoConnect™ technology uses the globally conserved N-glycosylation site to generate stable and site-specific ADCs based on enzymatic remodeling and metal-free click chemistry. We demonstrate how an engineered endoglycosidase and a native glycosyl transferase enable highly efficient, one-pot glycan remodeling, incorporating a novel sugar substrate 6-azidoGalNAc. Metal-free click attachment of an array of cytotoxic payloads was highly optimized, in particular by inclusion of anionic surfactants. The therapeutic potential of GlycoConnect™, in combination with HydraSpace™ polar spacer technology, was compared to that of Kadcyla® (ado-trastuzumab emtansine), showing significantly improved efficacy and tolerability.

Selection of Payloads for Antibody-Drug Conjugates Targeting Ubiquitously Expressed Tumor-Associated Antigens: a Case Study.

The main objective of this work was to demonstrate which kind of payload is the suitable choice for antibody-drug conjugates directed to widely expressed tumor-associated antigen. Trop-2 is overexpressed in various solid tumors, but it is also present on the epithelium of several normal tissues. A well-designed anti-Trop-2 ADC demands a good balance of efficacy and toxicity. In this research, MMAE, SN-38, and DXd were selected as candidates for payloads of the anti-Trop-2 mAb SY02. The antitumor activities and safety profiles of these ADCs were investigated to compare the therapeutic windows. Robust in vitro cytotoxicity was observed on human pancreatic cancer cell CFPAC-1 and breast cancer cell MDA-MB-468 with IC50 generally in the subnanomolar range. Consistent with in vitro assay, SY02-DXd and SY02-SN-38 demonstrated superior efficacy in CFPAC-1 xenograft models with TGI rates of 98.2% and 87.3%, respectively. However, SY02-MMAE could hardly inhibit the tumor growth. Subsequently, antitumor activities of these ADCs were further compared in MDA-MB-468 xenograft model. Complete tumor regression was observed in SY02-DXd and SY02-MMAE groups, indicating their potent antitumor activities. In an exploratory safety and pharmacokinetic study, SY02-DXd demonstrated the best safety profile with minimal adverse events in cynomolgus monkeys, while SY02-MMAE exhibited severe on-target skin toxicity which caused death. In conclusion, SY02-DXd demonstrated superior efficacy and safety with the widest therapeutic window. Based on the efficacy and safety results, moderate cytotoxic payloads would be ideal choices for ADCs targeting ubiquitously expressed antigens.

Research Progress of Antibody-Drug Conjugate Therapy for Advanced Gastric Cancer.

Gastric cancer is an intractable malignant tumor that has the fifth highest morbidity and the third highest mortality in the world. Even though various treatment options did much to ameliorate the prognosis of advanced gastric cancer, the survival time remained unsatisfactory. It is significant to develop new therapeutic agents to improve the long-term outcome. Antibody–drug conjugate is an innovative and potent antineoplastic drug composed of a specifically targeted monoclonal antibody, a chemical linker, and a small molecule cytotoxic payload. Powerful therapeutic efficacy and moderate toxicity are its preponderant advantages, which imply the inevitable pharmaceutical developments to meet the demand for individualized precision therapy. Nevertheless, it is unavoidable that there is a phenomenon of drug resistance in this agent. This article systematically reviewed the recent progress of antibody–drug conjugates in advanced gastric cancer therapy.

Disitamab vedotin: a novel antibody-drug conjugates for cancer therapy

Human epidermal growth factor receptor 2 (HER2) regulates cell mitosis, proliferation, and apoptosis. Trastuzumab is a HER2-targeted monoclonal antibody (mAB), which can prolong the overall survival rate of patients with HER2 overexpression in later periods of gastric cancer and breast cancer. Although anti-HER2 monoclonal antibody has a curative effect, adjuvant chemotherapy is still necessary to upgrade the curative effect maximumly. Antibody-drug conjugate (ADC) is a kind of therapeutic drug that contains antigen-specific antibody and cytotoxic payload, which can improve the survival time of tumor patients. To date, there are several HER2-ADC products on the market, for which two anti-HER2 ADC (trastuzumab emtansine and trastuzumab deruxtecan) have been authorized by the FDA for distinct types of HER2-positive carcinoma in the breast. Disitamab vedotin (RC48) is a newly developed ADC drug targeting HER2 that is comprised of hertuzumab coupling monomethyl auristatin E (MMAE) via a cleavable linker. This paper aims to offer a general insight and summary of the mechanism of action and the currently completed and ongoing clinical studies of RC-48 in HER-2 positive solid tumors.