Antibody-drug Conjugate Targeting Research Articles

Preclinical Evaluation of STI-8811, a Novel Antibody Drug Conjugate Targeting BCMA for the Treatment of Multiple Myeloma.

Treatment for patients with Multiple Myeloma (MM) has experienced rapid development and improvement in recent years, however, patients continue to experience relapse and MM remains largely incurable. B cell maturation antigen (BCMA) has been widely recognized as a promising target for treatment of MM due to its exclusive expression in B cell linage cells and its critical role in the growth and survival of malignant plasma cells. Here, we introduce STI-8811, a BCMA-targeting antibody drug conjugate linked to an auristatin-derived duostatin payload via an enzymatically cleavable peptide linker, using our proprietary C-lock technology. STI-8811 exhibits target specific binding activity and rapid internalization, leading to G2/M cell cycle arrest, caspase 3/7 activation and apoptosis in BCMA-expressing tumor cells in vitro. Soluble BCMA (sBCMA) is shed by MM cells into the blood and increases with disease progression, competing for ADC binding and reducing its efficacy. We report enhanced cytotoxic activity in the presence of high levels of sBCMA compared to a belantamab mafodotin biosimilar (J6M0-mcMMAF). STI-8811 demonstrated greater in vivo activity than J6M0-mcMMAF in solid and disseminated multiple myeloma models, including tumor models with low BCMA expression and/or in large solid tumors representing soft tissue plasmacytomas. In Cynomolgus monkeys, STI-8811 was well tolerated, with toxicities consistent with other BCMA targeting ADCs with auristatin payloads in clinical studies. STI-8811 has the potential to outperform current clinical candidates with lower toxicity and higher activity under conditions found in patients with advanced disease.

Tuning Responses to Polatuzumab Vedotin in B-cell Lymphoma.

Polatuzumab vedotin, an antibody-drug conjugate targeting CD79B, is the first new drug approved for first-line therapy of diffuse large B-cell lymphoma in more than two decades, although factors determining treatment responses to polatuzumab vedotin remain unknown. Two new studies identified central mechanisms of lower sensitivity, namely reduced accessibility of the CD79B epitope through N-linked glycosylation of CD79B and lower CD79B surface expression levels due to the activity of the KLHL6 E3 ligase. See related article by Corcoran et al., p. 1653 (6) See related article by Meriranta et al. (7).

Enhancing antitumor efficacy of CLDN18.2-directed antibody-drug conjugates through autophagy inhibition in gastric cancer

Claudin18.2 (CLDN18.2) is overexpressed in cancers of the digestive system, rendering it an ideal drug target for antibody-drug conjugates (ADCs). Despite many CLDN18.2-directed ADCs undergoing clinical trials, the inconclusive underlying mechanisms pose a hurdle to extending the utility of these agents. In our study, αCLDN18.2-MMAE, an ADC composed of an anti-CLDN18.2 monoclonal antibody and the tubulin inhibitor MMAE, induced a dose-dependent apoptosis via the cleavage of caspase-9/PARP proteins in CLDN18.2-positive gastric cancer cells. It was worth noting that autophagy was remarkably activated during the αCLDN18.2-MMAE treatment, which was characterized by the accumulation of autophagosomes, the conversion of autophagy marker LC3 from its form I to II, and the complete autophagic flux. Inhibiting autophagy by autophagy inhibitor LY294002 remarkably enhanced αCLDN18.2-MMAE-induced cytotoxicity and caspase-mediated apoptosis, indicating the cytoprotective role of autophagy in CLDN18.2-directed ADC-treated gastric cancer cells. Combination with an autophagy inhibitor significantly potentiated the in vivo antitumoral efficacy of αCLDN18.2-MMAE. Besides, the Akt/mTOR pathway inactivation was demonstrated to be implicated in the autophagy initiation in αCLDN18.2-MMAE-treated gastric cancer cells. In conclusion, our study highlighted a groundbreaking investigation into the mechanism of the CLDN18.2-directed ADC, focusing on the crucial role of autophagy, providing a novel insight to treat gastric cancer by the combination of CLDN18.2-directed ADC and autophagy inhibitor.

721MO Phase I, two-part, multicenter first-in-human (FIH) study of TORL-1-23: A novel claudin 6 (CLDN6) targeting antibody drug conjugate (ADC) in patient with advanced solid tumors

721MO Phase I, two-part, multicenter first-in-human (FIH) study of TORL-1-23: A novel claudin 6 (CLDN6) targeting antibody drug conjugate (ADC) in patient with advanced solid tumors

437TiP An open-label, multicenter, phase II study to evaluate the safety and efficacy of BB-1701, a novel antibody drug conjugate (ADC) targeting HER2, in previously treated patients (pts) with HER2+ or HER2-low unresectable or metastatic (M) breast cancer (BC)

437TiP An open-label, multicenter, phase II study to evaluate the safety and efficacy of BB-1701, a novel antibody drug conjugate (ADC) targeting HER2, in previously treated patients (pts) with HER2+ or HER2-low unresectable or metastatic (M) breast cancer (BC)

795TiP A first-in-human phase I study of LY4170156, an antibody-drug conjugate targeting folate receptor α (FRα)-expressing advanced solid tumors

795TiP A first-in-human phase I study of LY4170156, an antibody-drug conjugate targeting folate receptor α (FRα)-expressing advanced solid tumors

1439P ABBV-400, a c-Met protein–targeting antibody-drug conjugate (ADC), in patients (pts) with advanced gastric/gastroesophageal junction adenocarcinoma (GEA): Results from a phase I study

1439P ABBV-400, a c-Met protein–targeting antibody-drug conjugate (ADC), in patients (pts) with advanced gastric/gastroesophageal junction adenocarcinoma (GEA): Results from a phase I study

DB-1314, a novel DLL3-targeting ADC with DNA topoisomerase I inhibitor, exhibits promising safety profile and therapeutic efficacy in preclinical small cell lung cancer models

BackgroundDelta-like ligand 3 (DLL3) is highly expressed on the cell surface of small cell lung cancer (SCLC), one of the most lethal malignancies, but minimally or not in normal tissues, making it an attractive target for SCLC. However, none of the DLL3-targeting antibody-drug conjugates (ADCs) have been approved for SCLC therapy yet. We developed DB-1314, the new anti-DLL3 ADC composed of a novel humanized anti-DLL3 monoclonal antibody (DB131401) conjugated with eight molecules of P1021 (topoisomerase I inhibitor), and described its preclinical profiles.MethodsThe binding epitope for DB131401 and Rovalpituzumab was tested by biolayer interferometry. The binding affinity and specificity of DB-1314 to DLL3 and other homologous proteins were respectively measured by surface plasmon resonance and enzyme-linked immunosorbent assay. Internalization, bystander effects, and antibody-dependent cell-mediated cytotoxicity (ADCC) were assessed by respective assay. DLL3 was quantified by antibodies bound per cell assay and immunohistochemistry. In vitro and in vivo growth inhibition studies were evaluated in SCLC cell lines, and cell line/patient-derived xenograft models. The safety profile was measured in cynomolgus monkeys.ResultsDB-1314 induces potent, durable, and dose-dependent antitumor effects in cells in vitro and in cell/patient-derived xenograft models in vivo. The killing activity of DB-1314 mechanically arises from P1021-induced DNA damage, whereby P1021 is delivered and released within tumor cells through DLL3-specific binding and efficient internalization. Bystander effects and ADCC also contribute to the antitumor activity of DB-1314. DB-1314 displays favorable pharmacokinetic and toxicokinetic profiles in rats and cynomolgus monkeys; besides, DB-1314 is well-tolerated at a dose of up to 60 mg/kg in monkeys.ConclusionsThese results suggest that DB-1314 may be a candidate ADC targeting DLL3 for the treatment of DLL3-positive SCLC, supporting further evaluation in the clinical setting.

A DXd/TLR7-agonist dual-conjugate anti-HER2 ADC exerts robust anti-tumor activity through tumor cell killing and immune activation.

The emergence of trastuzumab deruxtecan (T-DXd), a new-generation antibody-drug conjugate (ADC), has profoundly altered the therapeutic paradigm for HER2-positive solid tumors, demonstrating remarkable clinical benefits. However, the combined outcomes of T-DXd with immunotherapy agents remain ambiguous. In this study, we introduce Tras-DXd-MTL1, an innovative HER2 targeting ADC that integrates the topoisomerase inhibitor DXd and a toll-like receptor 7 (TLR7) agonist MTT-5, linked to trastuzumab via a GGFG tetrapeptide linker. Mechanistically, Tras-DXd-MTL1 retains the DNA-damaging and cell-killing properties of topoisomerase inhibitors while simultaneously enhancing the immune response within the tumor microenvironment (TME). This is achieved by promoting immune cell infiltration and activating dendritic cells and CD8+T cells via MTT-5. In vivo evaluation of Tras-DXd-MTL1's anti-tumor potency revealed a notably superior performance compared to the T-DXd (Tras-DXd) or Tras-MTL1 in immunocompetent mice with trastuzumab-resistant EMT6-HER2 tumor and immunodeficient mice with JIMT-1 tumor. This improved efficacy is primarily attributed to its dual functions of immune stimulation and cytotoxicity. Our findings highlight the potential of incorporating immunostimulatory agents into ADC design to potentiate antitumor effects and establish durable immune memory, thereby reducing tumor recurrence risks. Therefore, our study offers a novel strategy for the design of immune-activating ADCs and provides a potential approach for targeting solid tumors with different levels of HER2 expression.

Antitumor Activity of a Pyrrolobenzodiazepine Antibody-Drug Conjugate Targeting LGR5 in Preclinical Models of Neuroblastoma.

Neuroblastoma (NB) is a cancer of the peripheral nervous system found in children under 15 years of age. It is the most frequently diagnosed cancer during infancy, accounting for ~12% of all cancer-related deaths in children. Leucine-rich repeat-containing G-protein-coupled receptor 5 (LGR5) is a membrane receptor that is associated with the primary tumor formation and metastasis of cancers in the gastrointestinal system. Remarkably, high levels of LGR5 are found in NB tumor cells, and high LGR5 expression is strongly correlated with poor survival. Antibody-drug conjugates (ADCs) are monoclonal antibodies that are covalently linked to cell-killing cytotoxins to deliver the payloads into cancer cells. We generated an ADC with an anti-LGR5 antibody and pyrrolobenzodiazepine (PBD) dimer-based payload SG3199 using a chemoenzymatic conjugation method. The resulting anti-LGR5 ADC was able to inhibit the growth of NB cells expressing LGR5 with high potency and specificity. Importantly, the ADC was able to completely inhibit the growth of NB xenograft tumors in vivo at a clinically relevant dose for the PBD class of ADCs. The findings support the potential of targeting LGR5 using the PBD class of payload for the treatment of high-risk NBs.

Trastuzumab-Deruxtecan: Redefining HER2 as a Tumor Agnostic Biomarker.

Trastuzumab deruxtecan (T-DXd) is an antibody-drug conjugate (ADC) targeting HER2-positive malignancies across various tumor types. Through its unique composition, T-DXd achieves selective payload delivery, inducing cell death and halting tumor progression. Clinical trials initially investigated T-DXd's efficacy in HER2-positive advanced or metastatic breast, gastric, lung, and colorectal cancers; however, recent results from the DESTINY-PanTumor02 trial further underscore T-DXd's versatility, prompting T-DXd's US FDA approval for HER2-positive (immunohistochemistry [IHC] 3+) solid tumors. Moreover, in addition to T-DXd's efficacy against brain metastasis, T-DXd is showing promising results in HER2-low and HER2-ultra-low metastatic breast cancer, indicating a broader population of patients who may benefit.

Therapeutic Targeting Tongue Squamous Cell Carcinoma via ICAM1 Antibody‐Drug Conjugates in Preclinical Models

AbstractTo date, the treatment options for metastatic and recurrent tongue squamous cell carcinoma (TSCC) remain limited due to the lack of effective drug targets and therapeutics. Here the identification of ICAM1 is reported as a TSCC target candidate for the development of antibody‐drug conjugate (ADC), an emerging class of targeted therapeutics. An unbiased and quantitative screening of a panel of 69 TSCC cell surface antigens is first performed that identifies ICAM1 as the most abundant hit. The overexpression level of ICAM1 is validated in 26 TSCC clinical specimens and four cell lines along with genomic information of 127 TSCC patients from the TCGA database. Based on this new target, the anti‐TSCC efficacy of ICAM1‐targeted ADCs featuring two payloads is evaluated of different mechanisms of action: MMAE and DXd. Both ADCs selectively and potently ablate TSCC tumors in the established SAS cell line and patient‐derived xenograft (PDX) models. The findings strongly support ICAM1 as a promising ADC target candidate for TSCC therapy.

A real-world pharmacovigilance study of polatuzumab vedotin based on the FDA adverse event reporting system (FAERS).

Polatuzumab vedotin, the first FDA-approved antibody-drug conjugate (ADC) targeting CD79b, is utilized in the treatment of previously untreated diffuse large B-cell lymphoma (DLBCL) or high-grade B-cell lymphoma (HGBL), as well as relapsed or refractory (R/R) DLBCL. Despite its approval, concerns persist regarding the long-term safety profile of polatuzumab vedotin. This study aims to evaluate the adverse events (AEs) associated with polatuzumab vedotin since its approval in 2019, utilizing data mining strategies applied to the FDA Adverse Event Reporting System (FAERS). Signal detection employed four methodologies, including reporting odds ratio (ROR), proportional reporting ratio (PRR), bayesian confidence propagation neural network (BCPNN), and multi-item gamma poisson shrinker (MGPS), to evaluate and quantify the signals of polatuzumab vedotin-associated AEs. Additionally, subgroup analyses based on patients age, gender, and fatal cases were conducted to investigate AEs occurrences in specific subpopulations. A total of 1,521 reports listing polatuzumab vedotin as a "principal suspect (PS)" drug were collected from the FAERS database. Through concurrent compliance with four algorithms, 19 significant Standardized MedDRA Query (SMQ) AEs and 92 significant Preferred Term (PT) AEs were detected. Subgroup analyses revealed a higher incidence of PTs in male patients compared to female patients, increased likelihood of polatuzumab vedotin-associated AEs in elder patients (>65years), and AEs with a high risk of fatal cases include: blood lactate dehydrogenase increased, cytopenia, and hydronephrosis. The median time to AEs occurrence following polatuzumab vedotin initiation was 18.5 (5∼57.75) days, with 95% of AEs occurred within 162days. This study identified various AEs associated with polatuzumab vedotin, offering critical insights for clinical monitoring and risk identification in patients receiving polatuzumab vedotin therapy.

Mechanistic Characterization of Cancer-associated Fibroblast Depletion via an Antibody-Drug Conjugate Targeting Fibroblast Activation Protein.

The direct elimination of FAP-expressing CAFs disrupts the cross-talk with cancer cells leading to a proinflammatory response and alterations in the immune microenvironment and antitumor immune response.

MYTX-011: a pH-dependent anti-cMET antibody-drug conjugate designed for enhanced payload delivery to cMET expressing tumor cells.

Advances in linker payload technology and target selection have been at the forefront of recent improvements in antibody-drug conjugate (ADC) design, leading to several approvals over the last decade. In contrast, the potential of novel ADC technologies to enhance payload delivery to tumors is relatively underexplored. We demonstrate that incorporation of pH-dependent binding in the antibody component of a cMET targeting ADC (MYTX-011) can overcome the requirement for high cMET expression on tumors, an innovation that has the potential to benefit a broader population of patients with lower cMET levels. MYTX-011 drove four-fold higher net internalization than a non-pH engineered parent ADC in non-small cell lung cancer (NSCLC) cells and showed increased cytotoxicity against a panel of cell lines from various solid tumors. A single dose of MYTX-011 showed at least three-fold higher efficacy than a benchmark ADC in mouse xenograft models of NSCLC ranging from low to high cMET expression. Moreover, MYTX-011 showed improved pharmacokinetics over parent and benchmark ADCs. In a repeat dose toxicology study, MYTX-011 exhibited a toxicity profile similar to other MMAE-based ADCs. These results highlight the potential of MYTX-011 for treating a broader range of NSCLC patients with cMET expression than other cMET targeting ADCs. A first in human study is ongoing to determine the safety, tolerability, and preliminary efficacy of MYTX-011 in patients with NSCLC (NCT05652868).

The role of TROP-2 in the progression and target therapy in penile squamous cell carcinoma.

e17023 Background: Penile squamous cell carcinoma(PSCC) is a devastating malignancy of urogenitary system. However, current chemotherapy treatments including TIP regimen has showed limited effects but strong side effects in advanced PSCC. Trophoblast cell-surface antigen-2 (Trop-2) is a novel target for Antibody-drug conjugates (ADC) drugs and is proved to be effective in several human cancers, but its role in PSCC has not been clearly certified. Methods: 198 PSCC tumor tissue specimens and clinicopathological data were collected. TROP-2 expression was detected by IHC experiments and the correlation between TROP-2 expression and clinicopathological data of patients was analyzed through statistical methods. Then a series of in vivo and in vitro experiments were conducted to investigate the mechanism that how TROP-2 promote PSCC cell proliferation. Results: IHC results showed that TROP-2 was highly expressed in 60.2% of tumor specimens, and statistical analysis revealed a positive association of TROP-2 expression with advanced pT, pN stages and extranodal extension (ENE), as well as poor prognosis. Knockdown of TROP-2 expression inhibited the proliferation of PSCC cells both in vivo and in vitro. Further experiments identified that TROP-2 promoted PSCC cell proliferation via AKT-mediated PKCα signaling pathway. TROP-2 ADC drugs could inhibited PSCC cell proliferation both in vitro and in vivo. Conclusions: TROP-2 promotes PSCC cell proliferation, and TROP-2 targeted ADC-drug is a promising agent for PSCC treatment in future.

Population pharmacokinetics of trastuzumab deruxtecan (T-DXd) in subjects with HER2-mutant and HER2-overexpressing non-small cell lung cancer (NSCLC).

e20537 Background: T-DXd is a novel human epidermal growth factor receptor 2 (HER2) targeting antibody drug conjugate, approved globally at the dose of 5.4 mg/kg in HER2-positive or HER2-low breast cancer (BC) and HER2-mutant (HER2m) NSCLC1,2. The aim of the analysis was to characterize the populaton pharmacokinetics (PopPK) of T-DXd and its released payload, deruxtecan (DXd), in HER2m or HER2-overexpressing (HER2-OE) NSCLC subjects using data across tumor types (BC, NSCLC and others) from 12 Phase 1 to 3 studies with T-DXd doses ranging from 0.8-8.0 mg/kg. Methods: Analysis wasperformed using nonlinear mixed-effects modeling methods in NONMEM (version 7.4.3), similar to the previous analysis in HER2-positive BC1. Covariate effects were explored on the PK parameters of T-DXd and DXd. Results: Analysis included data across 1822 subjects, including 346, 1128, and 348 subjects with NSCLC, BC, and other cancers, respectively. The PK of T-DXd and DXd were adequately described by a PopPK model, judging by standard model diagnostics3. Covariate effects on T-DXd and DXd steady-state area under the concentration-time curve (AUC) were not clinically meaningful (within 0.8 to 1.25 AUC ratio interval for tested covariate level versus reference), except for subjects with high body weight (e.g., 90 kg; 95th percentile) showing a 31% and 37% higher T-DXd and DXd AUC, respectively, relative to typical subject with 58 kg body weight (median).The T-DXd and DXd AUC were also similar across subjects with BC, HER2m or HER2-OE NSCLC, with the same T-DXd dose. T-DXd and DXd AUC in NSCLC subjects were similar across subjects with mild hepatic or mild or moderate renal impairment (vs. normal counterparts), region (Asia, North America, Europe, and rest of the world), and race-country (Asian-Japan, Asian-Non-Japan, and Non-Asian) groups. Conclusions: T-DXd and DXd exposures were similar across subjects with BC and HER2m or HER2-OE NSCLC, as well as across hepatic function, renal function, region, and race-country groups within NSCLC supporting the use of 5.4 mg/kg dose (approved dose in BC) in HER2m or HER2-OE NSCLC from PK perspective. Reference: Enhertu [package insert]. Basking Ridge, NJ: Daiichi Sankyo, Inc.; 2022. Enhertu [summary of product characteristics]. Daiichi Sankyo Europe GmbH, Munich; 2022 Yin O et al. Clin Pharmacol Ther. 2021;109(5):1314-1325. Clinical trial information: NCT04644237 , NCT03505710 .

Exposure-response (ER) analyses of efficacy and safety of trastuzumab deruxtecan (T-DXd) to inform dosing recommendation in HER2-mutant non-small cell lung cancer (NSCLC).

e20545 Background: T-DXd, a novel human epidermal growth factor receptor 2 (HER2) targeting antibody drug conjugate, was evaluated at doses of 5.4 and 6.4 mg/kg every three weeks in Phase 1 or 2 trials in HER2 mutant (HER2m) NSCLC subjects, including Destiny-Lung01 (DL-01) and DL-02 trials1,2. ER analyses of key efficacy and safety endpoints were conducted to support the dosing recommendation of T-DXd in HER2m NSCLC. Methods: Exposure-efficacy (EE) analysis was performed using confirmed objective response (cORR) data from HER2m NSCLC in Phase 1-2 trials (N = 181). The dataset included primary analysis data cut from DL-011 and interim analysis data cut from DL-02. Exposure-safety (ES) analyses of T-DXd were performed, using pooled data from 11 Phase 1-3 trials (N = 1850) across tumor types, including DL-01 and DL-02, for safety endpoints of adverse events (AEs) associated with dose reduction or discontinuation, Grade3+ (G3+) AEs, serious AEs, G3+Anemia, G3+neutropenia, G3+thrombocytopenia, adjudicated any grade interstitial lung disease (ILD), and G3+ ILD. cORR and all safety endpoints, except ILD were analyzed by logistic regression; any grade ILD was analyzed by parametric time-to-event analysis. The T-DXd or DXd exposure metric and numerous patient-specific covariates were tested in the analysis. Results: T-DXd exposure had a positive but shallow relationship with cORR. The predicted cORR varied from 57% (95% credible interval (CrI): [36, 77]) to 65% (95% CrI: [41, 84]) across 5th and 95th percentile of T-DXd exposure respectively. No clinically meaningful difference in cORR was estimated across 5.4 and 6.4 mg/kg doses with predicted cORR values of 53% (95% CrI: [44, 60]) and 55% (95% CrI: [47, 62]) at T-DXd doses of 5.4 mg/kg and 6.4 mg/kg, respectively. ES relationships were consistent with previous T-DXd ES analyses in breast cancer (BC). Model-predicted AE rates were lower (up to 9%) in 5.4 mg/kg compared to the 6.4 mg/kg dose. Model-predicted safety at 5.4 mg/kg dose in HER2m NSCLC was similar to the approved dose of 5.4 mg/kg in BC. Conclusions: The ER analyses showed no clinically meaningful difference in efficacy between 5.4 and 6.4 mg/kg doses of T-DXd; and safety events were lower in 5.4 mg/kg, thus supporting the 5.4 mg/kg recommended dose for HER2m NSCLC. These findings were later confirmed based on primary analysis in DL-022 and support the utility of ER analyses in dosing recommendation. Reference: Li BT et al. N Engl J Med 2022;386:241-51 Goto K et al. J Clin Oncol 41:4852-4863. Clinical trial information: NCT03505710 , NCT04644237 .

Increased risk of hyperglycemia in patients with advanced urothelial cancer treated with enfortumab vedotin: A systematic review and meta-analysis.

e15001 Background: Enfortumab vedotin (EV), an antibody-drug conjugate targeting anti-nectin-4, which is highly expressed in urothelial cancers, has emerged as an effective therapy in the management of previously treated advanced urothelial cancer. urothelial cancer. Severe hyperglycemia has been recognized as an unexpectedly adverse effect, and can lead to discontinuation of EV or fatal event. To assess the overall risk of hyperglycemia associated with the use of EV, a systematic review and meta-analysis of published clinical trials was performed. Methods: A comprehensive review through 2023 of PubMed and American Society of Clinical Oncology conferences was performed to identify relevant clinical trials and abstracts. Eligible studies were clinical trials of patients with urothelial cancer receiving EV at the standard dose with data on hyperglycemia available. Incidence rates, relative risks, and 95% confidence intervals were calculated using random-effects or fixed-effects models. Results: Our search culminated in the inclusion of 1,150 patients from four trials, with 859 of them receiving EV. The summary incidences for all-grade and high-grade hyperglycemia were 9.9% (95% CI: 7.8-12.5%) and 6.0% (95% CI: 4.6-7.8%) respectively. Patients treated with EV had an increased risk of developing hyperglycemia in comparison with chemotherapy with an RR of 19.66 (95% CI: 2.66-145.55, P=0.004) for all-grade and 26.54 (95% CI: 1.59-444.48, P=0.023). In comparison with single-agent EV, its combination with pembrolizumab did not significantly increase the risk of all-grade hyperglycemia (P=0.148). Conclusions: EV is associated with a significantly increased risk of all-grade and high-grade hyperglycemia.

First-in-human study of ABBV-706, a seizure-related homolog protein 6 (SEZ6)–targeting antibody-drug conjugate (ADC), in patients (pts) with advanced solid tumors.

3001 Background: SEZ6 is a transmembrane protein expressed in small cell lung cancer (SCLC) and other neuroendocrine neoplasms (NENs), and central nervous system (CNS) tumors. These malignancies have a high unmet need for novel effective therapies. ABBV-706 is an ADC targeting SEZ6 conjugated to a topoisomerase 1 inhibitor payload at a drug-to-antibody ratio of 6, and is highly efficacious in preclinical models of SCLC, NENs, and CNS tumors. Here, results from ABBV-706 monotherapy dose escalation (DE) are presented. Methods: Phase 1, open-label, multicenter, DE and dose-expansion study (NCT05599984) of ABBV-706 as monotherapy or in combination with budigalimab (a programmed cell death 1 inhibitor), carboplatin, or cisplatin. Primary objectives are to determine the safety, PK, preliminary efficacy, and recommended phase 2 dose of ABBV-706. Exploratory objectives are to assess SEZ6 expression retrospectively and its association with safety, PK, and efficacy. DE enrolled adults (≥18 yr) with relapsed/refractory SCLC, high-grade CNS tumors, and high-grade NENs, following the Bayesian optimal interval design. ABBV-706 was administered IV at 1.3–3.5 mg/kg doses Q3W in 21-d cycles. Results: As of data cutoff on Nov 15, 2023, 49 pts (SCLC: n=22 [45%]; CNS tumors: n=5 [10%]; NEN: n=22 [45%]) were enrolled and treated with ABBV-706 in DE and backfill cohorts. Median age was 64 yr (range 32–81) and median prior lines of therapy was 2.5 (range 1–6). 2 pts had a dose-limiting toxicity: 1 G4 leukopenia and neutropenia lasting >7 d at 3.0 mg/kg and 1 G4 thrombocytopenia at 3.5 mg/kg. TEAEs occurred in 45 (92%) pts, the most frequent being anemia (51%), fatigue (41%), neutropenia (31%), and leukopenia (31%). G≥3 TEAEs occurred in 28 (57%) pts and were mainly hematologic: neutropenia (29%), anemia (27%), and leukopenia (25%). No pneumonitis/interstitial lung disease was observed. Gastrointestinal TEAEs (all G1/2) were seen in 55% of pts, with the most common being nausea (27%) and vomiting (18%). There were no ABBV-706–related deaths. The maximum tolerated dose was 3 mg/kg IV Q3W. ABBV-706 ADC showed an approximate dose-proportional increase in exposure with an elimination half-life of approximately 7 d across doses. For 33 RECIST-evaluable pts, the confirmed (c) objective response rate was overall 21% (7 partial responses [PRs]); 40% (6/15) for SCLC and 6% (1/18) for NEN. The overall response (c and unconfirmed [u]) rate without confirmation was 45% (7 cPRs/8 uPRs); 73% (6 cPRs/5 uPRs) for SCLC, and 22% (1 cPR/3 uPRs) for NEN. 8 uPRs are pending confirmation and will be reported in the final presentation. The clinical benefit rate was 91% (7 PR, 23 stable disease). No activity was observed in 3/3 pts with high-grade gliomas. Conclusions: ABBV-706 demonstrated a manageable safety profile with promising efficacy in SCLC and NENs. Further evaluation of ABBV-706 is ongoing. Clinical trial information: NCT05599984 .