Bispecific Antibody Research Articles

Striking the Balance with a PD-L1×4-1BB Bispecific Antibody.

Antibody-based immune checkpoint blockade therapy has revolutionized the field of cancer immunotherapy, yet its efficacy remains limited in immunologically cold tumors. Combining checkpoint inhibitors with costimulatory agonists improves tumoricidal activity of T cells but also can lead to off-target hepatotoxicity. Although bispecific antibodies confer tumor selectivity to alleviate undesirable adverse effects, toxicity concerns persist with increased dosing. In this issue of Cancer Research, Yuwen and colleagues introduce ATG-101, a tetravalent PD-L1×4-1BB bispecific antibody with high programmed death ligand 1 (PD-L1) affinity and low 4-1BB affinity, aiming to mitigate hepatotoxicity. ATG-101 demonstrates PD-L1-dependent 4-1BB activation, leading to selective T-cell activation within the tumor microenvironment. ATG-101 exhibits potent antitumor activity, even in large, immunologically cold, and monotherapy-resistant tumor models. Single-cell RNA sequencing reveals significant shifts of immune cell populations in the tumor microenvironment from protumor to antitumor phenotypes following ATG-101 treatment. In cynomolgus monkeys, no serious cytokine storm and hepatotoxicity are observed after ATG-101 treatment, indicating a broad therapeutic window for ATG-101 in cancer treatment. This study highlights the potential of tetravalent bispecific antibodies in cancer immunotherapy, with implications for various antibody-based treatment modalities across different fields. See related article by Yuwen et al., p. 1680.

French early nationwide idecabtagene vicleucel chimeric antigen receptor T-cell therapy experience in patients with relapsed/refractory multiple myeloma (FENIX): A real-world IFM study from the DESCAR-T registry.

Idecabtagene vicleucel (ide-cel), a chimeric antigen receptor T-cell therapy targeting B-cell maturation antigen (BCMA), received early access program (EAP) authorization in France in April 2021 for relapsed/refractory multiple myeloma (RRMM). We conducted a real-world registry-based multicentre observational study in 11 French hospitals to evaluate ide-cel outcomes. Data from 176 RRMM patients who underwent apheresis between June 2021 and November 2022 were collected from the French national DESCAR-T registry. Of these, 159 patients (90%) received ide-cel. Cytokine release syndrome occurred in 90% with 2% grade ≥3, and neurotoxicity occurred in 12% with 3% grade ≥3. Over the first 6 months, the best overall response and ≥complete response rates were 88% and 47% respectively. The median progression-free survival (PFS) from the ide-cel infusion was 12.5 months, the median overall survival (OS) was 20.8 months and the estimated OS rate at 12 months was 73.3%. Patients with extra-medullary disease (EMD) had impaired PFS (6.2 months vs. 14.8 months). On multivariable analysis, EMD and previous exposure to BCMA-targeted immunoconjugate or T-cell-redirecting GPRC5D bispecific antibody were associated with inferior PFS. Our study supports ide-cel's feasibility, safety and efficacy in real-life settings, emphasizing the importance of screening for EMD and considering prior treatments to optimize patient selection.

Anti-4-1BB×PD-L1 Bispecific Antibody Reinvigorates Tumor-Specific Exhausted CD8+ T Cells and Enhances the Efficacy of Anti-PD-1 Blockade.

To overcome the limited efficacy of immune checkpoint blockade, there is a need to find novel cancer immunotherapeutic strategies for the optimal treatment of cancer. The novel anti-4-1BB×PD-L1 bispecific antibody-ABL503 (also known as TJ-L14B)-was designed to simultaneously target PD-L1 and 4-1BB, and demonstrated strong antitumor T-cell responses without considerable toxicity. Here, we investigated how the combination of ABL503 and anti-PD-1 blockade affected the reinvigoration of exhausted tumor-infiltrating CD8+ T cells (CD8+ TILs) and anti-tumor efficacy. Single cell suspensions of hepatocellular carcinoma and ovarian cancer from treatment-naive patients were used for immunophenotyping of CD8+ TILs and in vitro functional assays. Humanized hPD-1/hPD-L1/h4-1BB triple knock-in mice were used to evaluate the effects of ABL503 and anti-PD-1 blockade in vivo. We observed that ABL503 successfully restored the functions of 4-1BB+ exhausted CD8+ TILs, which were enriched for tumor-specific T cells but unresponsive to anti-PD-1 blockade. Importantly, compared to anti-PD-1 blockade alone, the combination of ABL503 and anti-PD-1 blockade further enhanced the functional restoration of human CD8+ TILs in vitro. Consistently, the combination of ABL503 with anti-PD-1 in vivo significantly alleviated tumor growth, and induced enhanced infiltration and activation of CD8+ TILs. ABL503-a PD-L1 and 4-1BB dual-targeting bispecific antibody-elicits pronounced additive tumor growth inhibition, with increased infiltration and functionality of exhausted CD8+ T cells, which in turn enhances the anti-cancer effects of anti-PD-1 blockade. These promising findings suggest that ABL503 (TJ-L14B) in combination with PD-1 inhibitors will likely further enhance therapeutic benefit in clinical trials.

Cancer therapy with antibodies.

The greatest challenge in cancer therapy is to eradicate cancer cells with minimal damage to normal cells. Targeted therapy has been developed to meet that challenge, showing a substantially increased therapeutic index compared with conventional cancer therapies. Antibodies are important members of the family of targeted therapeutic agents because of their extraordinarily high specificity to the target antigens. Therapeutic antibodies use a range of mechanisms that directly or indirectly kill the cancer cells. Early antibodies were developed to directly antagonize targets on cancer cells. This was followed by advancements in linker technologies that allowed the production of antibody-drug conjugates (ADCs) that guide cytotoxic payloads to the cancer cells. Improvement in our understanding of the biology of T cells led to the production of immune checkpoint-inhibiting antibodies that indirectly kill the cancer cells through activation of the T cells. Even more recently, bispecific antibodies were synthetically designed to redirect the T cells of a patient to kill the cancer cells. In this Review, we summarize the different approaches used by therapeutic antibodies to target cancer cells. We discuss their mechanisms of action, the structural basis for target specificity, clinical applications and the ongoing research to improve efficacy and reduce toxicity.

IL-15/IL-15Rα-Fc fusion protein XmAb24306 potentiates activity of CD3 bispecific antibodies through enhancing T cell expansion.

Insufficient quantity of functional T cells is a likely factor limiting clinical activity of T cell bispecific antibodies, especially in solid tumor indications. We hypothesized that XmAb24306 (efbalropendekin alfa), a lymphoproliferative interleukin (IL)-15/IL-15 receptor α (IL-15Rα) Fc-fusion protein, may potentiate the activity of T cell dependent (TDB) antibodies. Activation of human peripheral T cells by cevostamab, an anti-FcRH5/CD3 TDB, or anti-HER2/CD3 TDB resulted in upregulation of IL-2/15Rβ (CD122) receptor subunit in nearly all CD8+ and majority of CD4+ T cells, suggesting that TDB treatment may sensitize T cells to the IL-15. XmAb24306 enhanced T cell bispecific antibody induced CD8+ and CD4+ T cell proliferation and expansion. In vitro combination of XmAb24306 with cevostamab or anti-HER2/CD3 TDB resulted in significant enhancement of tumor cell killing, which was reversed when T cell numbers were normalized, suggesting that T cell expansion is the main mechanism for the observed benefit. Pre-treatment of immune competent mice with a mouse-reactive surrogate of XmAb24306 (mIL-15-Fc) resulted in significant increase of T cells in blood, spleen and in tumors and converted transient anti-HER2/CD3 TDB responses to complete durable responses. In summary, our results support the hypothesis where the number of tumor infiltrating T cells is rate limiting for the activity of solid tumor targeting TDBs. Upregulation of CD122 by TDB treatment and the observed synergy with XmAb24306 and T cell bispecific antibodies supports clinical evaluation of this novel immunotherapy combination.

Radiolabelling and preclinical characterisation of [89Zr]Zr-Df-ATG-101 bispecific to PD-L1/4-1BB.

ATG-101, a bispecific antibody that simultaneously targets the immune checkpoint PD-L1 and the costimulatory receptor 4-1BB, activates exhausted T cells upon PD-L1 crosslinking. Previous studies demonstrated promising anti-tumour efficacy of ATG-101 in preclinical models. Here, we labelled ATG-101 with 89Zr to confirm its tumour targeting effect and tissue biodistribution in a preclinical model. We also evaluated the use of immuno-PET to study tumour uptake of ATG-101 in vivo. ATG-101, anti-PD-L1, and an isotype control were conjugated with p-SCN-Deferoxamine (Df). The Df-conjugated antibodies were radiolabelled with 89Zr, and their radiochemical purity, immunoreactivity, and serum stability were assessed. We conducted PET/MRI and biodistribution studies on [89Zr]Zr-Df-ATG-101 in BALB/c nude mice bearing PD-L1-expressing MDA-MB-231 breast cancer xenografts for up to 10 days after intravenous administration of [89Zr]Zr-labelled antibodies. The specificity of [89Zr]Zr-Df-ATG-101 was evaluated through a competition study with unlabelled ATG-101 and anti-PD-L1 antibodies. The Df-conjugation and [89Zr]Zr -radiolabelling did not affect the target binding of ATG-101. Biodistribution and imaging studies demonstrated biological similarity of [89Zr]Zr-Df-ATG-101 and [89Zr]Zr-Df-anti-PD-L1. Tumour uptake of [89Zr]Zr-Df-ATG-101 was clearly visualised using small-animal PET imaging up to 7 days post-injection. Competition studies confirmed the specificity of PD-L1 targeting in vivo. [89Zr]Zr-Df-ATG-101 in vivo distribution is dependent on PD-L1 expression in the MDA-MB-231 xenograft model. Immuno-PET with [89Zr]Zr-Df-ATG-101 provides real-time information about ATG-101 distribution and tumour uptake in vivo. Our data support the use of [89Zr]Zr-Df-ATG-101 to assess tumour and tissue uptake of ATG-101.

Chondroitin sulfate proteoglycan 4: An attractive target for antibody-based immunotherapy.

Multifunctional molecules involved in tumor progression and metastasis have been identified as valuable targets for immunotherapy. Among these, chondroitin sulfate proteoglycan 4 (CSPG4), a significant tumor cell membrane-bound proteoglycan, has emerged as a promising target, especially in light of advances in chimeric antigen receptor (CAR) T-cell therapy. The profound bioactivity of CSPG4 and its role in pivotal processes such as tumor proliferation, migration, and neoangiogenesis underline its therapeutic potential. We reviewed the molecular intricacies of CSPG4, its functional attributes within tumor cells, and the latest clinical-translational advances targeting it. Strategies such as blocking monoclonal antibodies, conjugate therapies, bispecific antibodies, small-molecule inhibitors, CAR T-cell therapies, trispecific killer engagers, and ribonucleic acid vaccines against CSPG4 were assessed. CSPG4 overexpression in diverse tumors and its correlation with adverse prognostic outcomes emphasize its significance in cancer biology. These findings suggest that targeting CSPG4 offers a promising avenue for future cancer therapy, with potential synergistic effects when combined with existing treatments.

Antigen escape as a shared mechanism of resistance to BCMA-directed therapies in multiple myeloma

B-cell maturation antigen (BCMA)-targeting therapeutics have dramatically improved outcomes in relapsed/refractory multiple myeloma (RRMM). However, whether the mechanisms of resistance between these therapies are shared and how the identification of such mechanisms before therapy initiation could refine clinical decision-making remains undefined. We analyzed outcomes for 72 RRMM patients treated with teclistamab, a CD3 x BCMA bispecific antibody (BsAb), 42% (30/72) of whom had prior BCMA-directed therapy exposure. Malignant plasma cell BCMA expression was present in all BCMA therapy-naïve patients. Prior therapy-mediated loss of plasma cell BCMA expression before teclistamab treatment, measured by immunohistochemistry, was observed in 3 patients, none of whom responded to teclistamab, and one of whom also did not respond to ciltacabtagene autoleucel. Whole exome sequencing of tumor DNA from one patient revealed biallelic loss of TNFRSF17 following treatment with belantamab mafodotin. Low-to-undetectable peripheral blood soluble BCMA levels correlated with the absence of BCMA expression by bone marrow plasma cells. Thus, although rare, loss of BCMA expression following TNFRSF17 gene deletions can occur following any BCMA-directed therapy and prevents response to subsequent anti-BCMA-directed treatments, underscoring the importance of verifying the presence of a target antigen.

A novel anti-LAG-3/TIGIT bispecific antibody exhibits potent anti-tumor efficacy in mouse models as monotherapy or in combination with PD-1 antibody

We report the generation of a novel anti-LAG-3/TIGIT bispecific IgG4 antibody, ZGGS15, and evaluated its anti-tumor efficacy in mouse models as monotherapy or in combination with a PD-1 antibody. ZGGS15 exhibited strong affinities for human LAG-3 and TIGIT, with KDs of 3.05 nM and 2.65 nM, respectively. ZGGS15 has EC50s of 0.69 nM and 1.87 nM for binding to human LAG-3 and TIGIT on CHO-K1 cells, respectively. ZGGS15 competitively inhibited the binding of LAG-3 to MHC-II (IC50 = 0.77 nM) and the binding of TIGIT to CD155 (IC50 = 0.24 nM). ZGGS15 does not induce ADCC, CDC, or obvious cytokine production. In vivo results showed that ZGGS15 had better anti-tumor inhibition than single anti-LAG-3 or anti-TIGIT agents and demonstrated a synergistic effect when combined with nivolumab, with a significantly higher tumor growth inhibition of 95.80% (p = 0.001). The tumor volume inhibition rate for ZGGS15 at 2 mg/kg was 69.70%, and for ZGGS15 at 5 mg/kg plus nivolumab at 1 mg/kg, it was 94.03% (p < 0.001). Our data reveal that ZGGS15 exhibits potent anti-tumor efficacy without eliciting ADCC or CDC or causing cytokine production, therefore having a safe profile.

Beyond VEGF: Angiopoietin–Tie Signaling Pathway in Diabetic Retinopathy

Complications from diabetic retinopathy such as diabetic macular edema (DME) and proliferative diabetic retinopathy (PDR) constitute leading causes of preventable vision loss in working-age patients. Since vascular endothelial growth factor (VEGF) plays a major role in the pathogenesis of these complications, VEGF inhibitors have been the cornerstone of their treatment. Anti-VEGF monotherapy is an effective but burdensome treatment for DME. However, due to the intensive and burdensome treatment, most patients in routine clinical practice are undertreated, and therefore, their outcomes are compromised. Even in adequately treated patients, persistent DME is reported anywhere from 30% to 60% depending on the drug used. PDR is currently treated by anti-VEGF, panretinal photocoagulation (PRP) or a combination of both. Similarly, a number of eyes, despite these treatments, continue to progress to tractional retinal detachment and vitreous hemorrhage. Clearly there are other molecular pathways other than VEGF involved in the pathogenesis of DME and PDR. One of these pathways is the angiopoietin–Tie signaling pathway. Angiopoietin 1 (Ang1) plays a major role in maintaining vascular quiescence and stability. It acts as a molecular brake against vascular destabilization and inflammation that is usually promoted by angiopoietin 2 (Ang2). Several pathological conditions including chronic hyperglycemia lead to Ang2 upregulation. Recent regulatory approval of the bi-specific antibody, faricimab, may improve long term outcomes in DME. It targets both the Ang/Tie and VEGF pathways. The YOSEMITE and RHINE were multicenter, double-masked, randomized non-inferiority phase 3 clinical trials that compared faricimab to aflibercept in eyes with center-involved DME. At 12 months of follow-up, faricimab demonstrated non-inferior vision gains, improved anatomic outcomes and a potential for extended dosing when compared to aflibercept. The 2-year results of the YOSEMITE and RHINE trials demonstrated that the anatomic and functional results obtained at the 1 year follow-up were maintained. Short term outcomes of previously treated and treatment-naive eyes with DME that were treated with faricimab during routine clinical practice suggest a beneficial effect of faricimab over other agents. Targeting of Ang2 has been reported by several other means including VE-PTP inhibitors, integrin binding peptide and surrobodies.

A research center’s experience of T-cell redirecting therapies in triple-class refractory multiple myeloma

The efficacies of chimeric antigen receptor T (CAR-T) cells and bispecific monoclonal antibodies (BiAbs) for triple-class refractory (TCR) myeloma have not previously been compared, and clinical data on how to rescue patients after relapse from these immunotherapies are limited. A retrospective study of 73 TCR patients included in trials was conducted: 36 received CAR-T and 37 received BiAbs. CAR-T produced a higher overall response rate (ORR) than BiAbs (97.1% vs. 56.8%, P=0.002). After a median of follow-up of 18.7 months, no significant difference in progression-free survival (PFS) was observed between the CAR-T and BiAbs groups (16.6 vs. 10.8 months; P=0.090), whereas overall survival (OS) was significantly longer in the CAR-T than in the BiAbs group (49.2 vs. 22.6 months; P=0.021). BiAbs following CAR-T yielded a higher ORR and longer PFS2 than did non-redirecting T cell therapies after CAR-T (ORR: 87.5% vs. 50.0%, PFS2: 22.9 vs. 12.4 months). By contrast, BiAbs following BiAbs resulted in an ORR of 33% and PFS2 of 8.4 months, which was similar to that produced by the non-redirecting T cell therapies (ORR: 28.6%, PFS2: 8.1 months). Even though this is a pooled analysis of different trials with different products and the patient profile is different for CAR-T and BiAbs, both were effective therapies for TCR myeloma. However, in our experience, while the PFS was similar with the two approaches, CAR-T therapy resulted in better OS, mainly because of the efficacy of BiAbs as rescue therapy. Our results highlight the importance of treatment sequence in real-word experience.

Relapse after glofitamab has a poor prognosis and rates of CD20 loss are high.

We reviewed cases with aggressive B-cell non-Hodgkin lymphoma who relapsed or progressed following glofitamab. The prognosis was poor, with low rates of response to subsequent salvage therapies, and a median overall survival of 4.1 months from the time of progression. There were high rates of CD20 loss (59%) at the time of relapse. In a field where CD20 × CD3 bispecific antibodies are entering routine clinical use, our experience highlights a potential means of resistance. It illustrates both the need to further characterise mechanisms of CD20 loss, and to pursue clinical trials of novel non-CD20-directed treatments in this cohort.

Chemical Production of Cytotoxic Bispecific Antibodies Using the Ugi Multicomponent Reaction.

Bispecific antibodies (bsAbs) have recently emerged as a promising platform for the treatment of several conditions, most importantly cancer. Based on the combination of two different antigen-binding motifs in a single macromolecule; bsAbs can either display the combined characteristics of their parent antibodies, or new therapeutic features, inaccessible by the sole combination of two distinct antibodies. While bsAbs are traditionally produced by molecular biology techniques, the chemical development of bsAbs holds great promises and strategies have just begun to surface. In this context, we took advantage of a chemical strategy based on the use of the Ugi reaction for the site-selective conjugation of whole antibodies and coupled the resulting conjugates in a bioorthogonal manner with Fab fragments, derived from various antibodies. We thus managed to produce five different bsAbs with 2:1 valency, with yields ranging from 20% to 48%, and showed that the affinity of the parent antibody was preserved in all bsAbs. We further demonstrated the interest of our strategy by producing two other bsAbs behaving as cytotoxic T cell engagers with IC50 values in the picomolar range in vitro.

BiSpec Pairwise AI: guiding the selection of bispecific antibody target combinations with pairwise learning and GPT augmentation

PurposeBispecific antibodies (BsAbs), capable of targeting two antigens simultaneously, represent a significant advancement by employing dual mechanisms of action for tumor suppression. However, how to pair targets to develop effective and safe bispecific drugs is a major challenge for pharmaceutical companies.MethodsUsing machine learning models, we refined the biological characteristics of currently approved or in clinical development BsAbs and analyzed hundreds of membrane proteins as bispecific targets to predict the likelihood of successful drug development for various target combinations. Moreover, to enhance the interpretability of prediction results in bispecific target combination, we combined machine learning models with Large Language Models (LLMs). Through a Retrieval-Augmented Generation (RAG) approach, we supplement each pair of bispecific targets’ machine learning prediction with important features and rationales, generating interpretable analytical reports.ResultsIn this study, the XGBoost model with pairwise learning was employed to predict the druggability of BsAbs. By analyzing extensive data on BsAbs and designing features from perspectives such as target activity, safety, cell type specificity, pathway mechanism, and gene embedding representation, our model is able to predict target combinations of BsAbs with high market potential. Specifically, we integrated XGBoost with the GPT model to discuss the efficacy of each bispecific target pair, thereby aiding the decision-making for drug developers.ConclusionThe novelty of this study lies in the integration of machine learning and GPT techniques to provide a novel framework for the design of BsAbs drugs. This holistic approach not only improves prediction accuracy, but also enhances the interpretability and innovativeness of drug design.

Elranatamab treatment in a multiple myeloma patient undergoing renal dialysis

We present the case of a dialyzed patient with relapsed IgA and lambda free light chain multiple myeloma treated with elranatamab. Despite end-stage renal impairment, the treatment with anti-B cell maturation antigen (BCMA)xCD3 bispecific antibody proved to be feasible, without unexpected side effects. Increased attention to infectious risk is crucial for these doubly fragile patients.

Ultrapotent Broadly Neutralizing Human-llama Bispecific Antibodies against HIV-1.

Broadly neutralizing antibodies are proposed as therapeutic and prophylactic agents against HIV-1, but their potency and breadth are less than optimal. This study describes the immunization of a llama with the prefusion-stabilized HIV-1 envelope (Env) trimer, BG505 DS-SOSIP, and the identification and improvement of potent neutralizing nanobodies recognizing the CD4-binding site (CD4bs) of vulnerability. Two of the vaccine-elicited CD4bs-targeting nanobodies, G36 and R27, when engineered into a triple tandem format with llama IgG2a-hinge region and human IgG1-constant region (G36×3-IgG2a and R27×3-IgG2a), neutralized 96% of a multiclade 208-strain panel at geometric mean IC80s of 0.314 and 0.033µg mL-1, respectively. Cryo-EM structures of these nanobodies in complex with Env trimer revealed the two nanobodies to neutralize HIV-1 by mimicking the recognition of the CD4 receptor. To enhance their neutralizing potency and breadth, nanobodies are linked to the light chain of the V2-apex-targeting broadly neutralizing antibody, CAP256V2LS. The resultant human-llama bispecific antibody CAP256L-R27×3LS exhibited ultrapotent neutralization and breadth exceeding other published HIV-1 broadly neutralizing antibodies, with pharmacokinetics determined in FcRn-Fc mice similar to the parent CAP256V2LS. Vaccine-elicited llama nanobodies, when combined with V2-apex broadly neutralizing antibodies, may therefore be able to fulfill anti-HIV-1 therapeutic and prophylactic clinical goals.

The bispecific B7H3xCD3 antibody CC-3 induces T cell immunity against bone and soft tissue sarcomas

Sarcomas are rare and heterogeneous malignancies that are difficult to treat. Approximately 50% of patients diagnosed with sarcoma develop metastatic disease with so far very limited treatment options. The transmembrane protein B7-H3 reportedly is expressed in various malignancies, including different sarcoma subtypes. In several cancer entities B7-H3 expression is associated with poor prognosis. In turn, B7-H3 is considered a promising target for immunotherapeutic approaches. We here report on the preclinical characterization of a B7-H3xCD3 bispecific antibody in an IgG-based format, termed CC-3, for treatment of different sarcoma subtypes. We found B7-H3 to be expressed on all sarcoma cells tested and expression on sarcoma patients correlated with decreased progression-free and overall survival. CC-3 was found to elicit robust T cell responses against multiple sarcoma subtypes, resulting in significant activation, release of cytokines and effector molecules. In addition, CC-3 promoted T cell proliferation and differentiation, resulting in the generation of memory T cell subsets. Finally, CC-3 induced potent target cell lysis in a target cell restricted manner. Based on these results, a clinical trial evaluating CC-3 in soft tissue sarcoma is currently in preparation.

Comparison of CAR T-cell vs. bispecific antibody as third- or later-line large B-cell lymphoma therapy: A Meta-analysis

This meta-analysis evaluates the efficacy and safety of chimeric antigen receptor (CAR) T-cell therapy and bispecific antibodies for relapsed/refractory diffuse large B-cell lymphoma (R/R DLBCL). We searched MEDLINE, Embase, and Cochrane databases until July 2023 for trials assessing CAR T-cell therapies and CD20×CD3 bispecific antibodies as third- or subsequent-line in R/R DLBCL. Random effects models estimated the complete response (CR) rate and secondary outcomes, with meta-regressions adjusting for relevant covariates. Sixteen studies comprising 1,347 patients were included in the pooled analysis. The pooled CR rate for bispecific antibodies was 0.36 (95% CI, 0.29 to 0.43), compared to 0.51 (0.46 to 0.56) for CAR T-cell therapy (p<0.01). This superiority persisted when comparing the CAR-T naïve patients within the bispecific antibody group, CR rate of 0.37 (0.32 to 0.43). Multivariable meta-regression also revealed better efficacy of CAR-T with adjustment for the proportion of double-hit lymphoma. The pooled one-year progression-free survival rate mirrored these findings (0.32 [0.26 to 0.38] vs 0.44 [0.41 to 0.48], p<0.01). For adverse events of ≥ grade 3, the bispecific antibody had incidences of 0.02 (0.01 to 0.04) for cytokine release syndrome, 0.01 (0.00 to 0.01) for neurotoxicity, and 0.10 (0.03 to 0.16) for infections. The CAR-T cell had rates of 0.08 (0.03 to 0.12), 0.11 (0.06 to 0.17), and 0.17 (0.11 to 0.22), respectively, with significant differences observed in the first two categories. In summary, CAR-T cell therapy outperformed bispecific antibody in achieving higher CR rates, though with an increase in severe adverse events.

Abstract PS08-06: A Phase Ib/II Study to Assess the Safety and Efficacy of PM8002 (Anti-PD-L1 x VEGF-A Bispecific Antibody) in Combination with Nab-Paclitaxel for First Line Treatment of Locally Advanced or Metastatic Triple-Negative Breast Cancer

Abstract Background: PD-L1 and VEGF play important roles in immune evasion and pro-tumor angiogenesis promoting cancer growth and metastasis. PM8002 is a bispecific antibody targeting PD-L1 and VEGF-A for treating cancer. Here, we present results from a Phase Ib/II study of PM8002 in combination with nab-paclitaxel in patients with locally-advanced or metastatic triple-negative breast cancer (TNBC). Methods: 42 patients with locally-advanced or metastatic TNBC (without prior systemic treatment) were enrolled in this Phase Ib/II study to test the safety and efficacy of PM8002 in combination with nab-paclitaxel. The first 6 patients were enrolled during Phase Ib with safety as the primary endpoint, and the remaining patients were enrolled during Phase II with objective response rate (ORR) as the primary endpoint. Each treatment cycle lasts 28 days. All patients received PM8002 at 20 mg/kg (Q2W) and nab-paclitaxel at 100 mg/m2 on the 1st, 8th, and 15th days of each cycle until unacceptable toxicity or disease progression were observed. Tumor responses were evaluated every 8 weeks according to RECIST 1.1. Safety was evaluated according to CTCAE 5.0. Nab-paclitaxel dose was reduced according to toxicity, while PM8002 dose was kept consistent according to body weight. PD-L1 expression in tumors was tested, and subgroup analysis of ORR data stratified by PD-L1 expression was also included. Results: As of June 30, 2023, 42 patients were treated and evaluated at least once for treatment efficacy. The median duration of drug exposure was 4.6 months (min, max: 2.0, 7.6). The best overall ORR was 76.2% (32/42), including 1 complete response (CR) and 31 partial responses (PRs) with 29 objective responses occurring at the patient's first evaluation. The confirmed ORR was 57.2% (24/42) and the overall disease control rate (DCR) was 95.2% (40/42). The median time to response (TTR) was 1.9 months (95% CI:1.8~2.0) and the median best percentage change from baseline for target lesions was -47.2% (Q1, Q3: -56.9%, -33.5%). Among 13 patients with PD-L1 combined positive scores (CPS) &amp;lt; 1, the best ORR and DCR were 69.2% (9/13) and 100.0% (13/13), respectively. Among 25 patients with PD-L1 CPS ≥1, the best ORR and DCR were 80.0% (20/25) and 96.0% (24/25), respectively. Among 9 patients with PD-L1 CPS ≥10, the best ORR and DCR were both 100.0% (9/9). At the cut-off date of data analysis, 38 patients were still on treatment with a median progression-free survival (mPFS) of 7.4 months (95% CI: 7.4~NA); 38 patients were censored due to no disease progression or death. The incidence of treatment-related adverse events (TRAEs) was 95.2%, of which 26.2% were Grade 3 or 4; no Grade 5 TRAEs were observed. The incidence of drug-related TRAEs related to PM8002 was 92.9%, of which 23.8% were Grade 3 or 4. The incidence of drug-related TRAEs related to nab-paclitaxel was 95.2%, of which 26.2% were Grade 3 or 4. 1 patient (2.4%) reduced nab-paclitaxel dose due to diarrhea. 1 patient (2.4%) discontinued PM8002 and nab-paclitaxel treatment due to diarrhea. The most common TRAEs related to PM8002 and nab-paclitaxel included neutropenia (69.0%), leukocytopenia (59.5%), anemia (52.4%) and proteinuria (26.2%). The incidence of immune-related adverse events (irAEs) was 11.9%, which included hyperthyroidism, hypothyroidism, and rash. No ≥ Grade 3 irAEs were observed. AEs related to targeting VEGF were also analyzed, including hypertension 19.0% (4.8% at Grade 1, 11.9% at Grade 2, and 2.4% at Grade 3) and proteinuria 26.2% (9.5% at Grade 1, and 16.7% at Grade 2). Conclusions: Rapid, deep, and durable tumor responses were observed for the combination of PM8002 and nab-paclitaxel in patients with first line TNBC. PM8002 did not enhance toxicity that is typically observed for nab-paclitaxel. This Phase II study is still ongoing with plans for entering late-stage clinical development for solid tumors. Citation Format: Jiong Wu, Jian Zhang, Zhongsheng Tong, Qingyuan Zhang, Yong-Sheng Wang, Qiao Cheng, Xin Chen, Zhihua Li, Yongmei Yin. A Phase Ib/II Study to Assess the Safety and Efficacy of PM8002 (Anti-PD-L1 x VEGF-A Bispecific Antibody) in Combination with Nab-Paclitaxel for First Line Treatment of Locally Advanced or Metastatic Triple-Negative Breast Cancer [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PS08-06.

Abstract PO1-29-02: Two and a half years follow-up data of HER2-targeted bispecific antibody KN026 combined with docetaxel as first-line treatment for HER2-positive recurrent/metastatic breast cancer

Abstract Background: KN026 is a novel bispecific HER2-targeted antibody. Fully humanized, IgG1-like antibody binds to two distinct HER2 epitopes, the same domains as trastuzumab and pertuzumab. Preliminary safety and efficacy results (data as of Aug 18, 2022) were presented at SABCs 2022(PD18-08), showed promising efficacy and tolerability. Herein, we update the 2.5-year follow-up results. Methods: Eligible subjects with recurrent/metastatic breast cancer, HER-2 positive and treatment-naive were enrolled. Subjects received KN026 30 mg/kg combined with docetaxel 75 mg/m2 Q3W until disease progression, unacceptable toxicity, or other reasons. The primary endpoints were ORR and DoR. The secondary endpoints included safety, PFS and OS. Results: As of data cut-off date (Sep 15, 2023), 57 subjects were enrolled, the median age was 52 years (min:30, max:67), 100% were female, and 91.2 % (52/57) were stage IV. There were 34 and 23 subjects with and without visceral metastasis, respectively. 48 subjects with high HER2 expression (IHC 3+), and the other 9 subjects with HER2 expression 2+ or 1+. The confirmed ORR within 55 evaluable subjects was 76.4% (42/55). The DoR was not reached yet with a median follow-up of 27.0 mons (95% CI: 26.28, 28.98). The median study follow-up was 30.6 mons (95% CI: 29.11, 31.77). The mPFS was 27.7 mons (95% CI:17.97, NE) and the mOS was not reached. The OS rates at 12m, 24m and 30m were 93.0% (95% CI: 82.37, 97.31), 84.2% (95% CI: 71.85, 91.45) and 78.5% (95% CI: 65.25, 87.21). The mPFS of subjects with or without visceral metastasis were 23.6 mons and not reached. The mPFS of subjects with or without brain metastasis were 13.7 mons and 28.1 mons, respectively. The mPFS of 48 subjects with high HER2 expression (3+) was 28.1 months. The incidence of KN026-related Grade≥3 TRAE was 43.9% (25/57), including neutrophil count decreased 24.6% (14/57), white blood cell count decreased 12.3% (7/57), hypokalaemia 7.0% (4/57), diarrhoea 3.5% (2/57) and others less than 2%. The incidence of serious adverse events related to KN026 was 12.3% (7/57). There was no KN026 -related death. Conclusions: KN026 in combination with docetaxel is well tolerated and has shown promising clinical benefit as 1L treatment for HER2-positive BC. After 2.5 years follow-up, mPFS was 27.7 mons and the 24-months OS rate was 84.2%, which is very promising. No new safety signals were observed. Robustness of efficacy and safety results will be further confirmed in an ongoing randomized phase 3 clinical trial with PTH as control. Citation Format: Qingyuan Zhang, Jingxuan Wang, Quchang Ouyang, Xiaojia Wang, Jingfen Wang, Lu Gan, Daren Lin, Zhong Ouyang, Ting Xu, Yilan Liu, Yuan Lv. Two and a half years follow-up data of HER2-targeted bispecific antibody KN026 combined with docetaxel as first-line treatment for HER2-positive recurrent/metastatic breast cancer [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO1-29-02.