Abstract The major hurdles in the treatment of solid tumors with chimeric antigen receptor (CAR) T cell therapies are antigen heterogeneity and the immunosuppressive tumor microenvironment. To address these challenges, we developed a universal and switchable CAR T cell therapy platform (zCART) that utilizes cotinine, a pharmacologically inert hapten, as a molecular bridge between anti-cotinine CAR T cells and tumor cells via cotinine-conjugated affibodies. First, we generated two affibody switches targeting distinct tumor-associated antigens and one affibody switch targeting an immune-oncology molecule. In vitro studies demonstrated that all three cotinine-conjugated affibodies, when combined with anti-cotinine CAR T cells, induced potent, dose-dependent cytotoxicity against target-expressing tumor cells. The combination of distinct affibody switches resulted in enhanced anti-tumor activity. These results highlight that the cotinine-based, switchable CAR T cell therapy platform enables flexible, multi-target control of CAR T cell activity and effective elimination of heterogeneous solid tumors. By decoupling antigen recognition from CAR T cell activation, the zCART platform offers a safe, versatile, and next-generation approach to overcoming tumor antigen variability and the immunosuppressive microenvironment, positioning it as a promising strategy for solid-tumor immunotherapy. Citation Format: Ki Hyun Kim, Soohwan Kim, Eun-Hoe Lee, Soo-Youn Lim, Tack-Jin Yoo, Sung Min Kim, E-Young Kim, Ji-Hun Park, Hyun-Jong Lee, Seong Yeol Kim, Min Yoon, Youngha Lee, In-Sik Hwang, Yoon Lee, Jong-Hoon Kim, Jong-Seo Lee, Junho Chung. A universal and switchable CAR T cell therapy platform (zCART) targeting tumor antigens and the immunosuppressive microenvironment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 1533.

Abstract Metastatic castration-resistant prostate cancer (mCRPC) remains a fatal malignancy with limited responsiveness to current immunotherapies. To achieve tumor-restricted immune activation, we developed AM109, a bispecific antibody that links a PSMA-targeting humanized antibody to a CD137 (4-1BB) affibody, designed to activate T cells exclusively in the presence of PSMA-expressing tumor cells. AM109 elicited robust CD8+ T-cell activation and cytokine secretion (IFN-γ, IL-2, and Granzyme B) in PSMA+ LNCaP cells, but not in PSMA- MKN45 cells, confirming its target-dependent mode of action. Cytotoxicity assays demonstrated dose-dependent tumor cell killing that correlated with PSMA expression levels. In vivo efficacy was evaluated using human CD137 transgenic mice bearing hPSMA/MC38 tumors, where AM109 achieved complete tumor regression at doses of 0.1-0.3 mpk, exhibiting superior potency compared with the reference CD137 agonist utomilumab. Structural and functional stability were maintained for at least 12 weeks at 4-40 °C. Pharmacokinetic and single-dose toxicity studies in rodents revealed favorable systemic exposure and good tolerability. Collectively, these findings demonstrate that AM109 selectively activates T cells within the tumor microenvironment, eliciting potent and PSMA-dependent anti-tumor responses with an improved therapeutic window. AM109 therefore represents a promising next-generation immunotherapeutic candidate for the treatment of mCRPC. Citation Format: Dong-Wook Kim, Hyun-Jong Lee, Seong Yeol Kim, Min Yoon, Youngha Lee, In-Sik Hwang, Yoon Lee, Jong-Hoon Kim, Jong-Seo Lee, . AM109, a PSMA×CD137 bispecific antibody with target-dependent T cell activation and potent anti-tumor activity in prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 2628.

Globally, colorectal cancer is a significant health concern. In 2020, there were over 1.9 million new cases and more than 930,000 deaths attributed to this disease and 5 year survival rate for distant colorectal cancer is 14.7 percent. Cetuximab, an approved anti-EGFR antibody, is effective in treating metastatic colorectal cancer with wild-type KRAS, improving survival. However, about 80% of patients develop resistance, leading to disease recurrence. To address this high recurrence rate, ongoing research focuses on developing bispecific antibodies that can overcome this resistance, aiming to improve long-term outcomes in metastatic colorectal cancer patients.AM105, a novel T cell-engaging bispecific antibody comprising a newly developed monoclonal antibody (15E3) and an affibody targeting EGFR and 4-1BB respectively. Characterized by its 2+4 architecture, it enhances selective binding to cancer cells by creating a difference in affinity between TAA and 4-1BB. It includes four Affibodies targeting 4-1BB, thereby increasing the likelihood of binding with T cells. Additionally, by enhancing the “clustering of CD137” on T cells, the T cell response is significantly amplified. In addition, AM105 was found to efficiently induce tumor cell death in CRC cell lines, even at very low effector-to-target cell ratio, in a target expression dependent manner. In vivo experiment using humanized 4-1BB mice have demonstrated excellent tumor cell elimination effects, and this therapeutic effect was still observed after newly introduction of tumor cells even in the absence of AM105 in the blood, suggesting the induction of T-cell memory function. Taken together, these results strongly suggested that AM105, a novel 4-1BB based bispecific antibody, exhibits potent anti-tumor T cell activity and could be promising therapeutic agent. Hyun-Jong Lee, Dong-Wook Kim, Seong-Yeol Kim, Min Yoon, Young-ha Lee, In-Sik Hwang, Yoon Lee, Jong-Hoon Kim, Jong-Seo Lee. AM105, first-in-class T cell engaging bispecific antibody for metastatic colon cancer, demonstrates strong anti-tumor activity by both neutralizing EGFR activity and engaging T cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 3505.

Abstract T cell engaging bispecific antibodies have emerged as promising treatments for hematologic malignancies. While most antibodies are CD3-based, offering therapeutic benefits, they are often associated with severe side effects and limited efficacy in solid tumors. To address these challenges, we present AM105, a groundbreaking anti 4-1BB affibodies based bispecific antibody designed to target EGFR. We carefully engineered AM105 with distinct binding affinities for EGFR (KD = 1.8 nM) and 4-1BB (KD = 60 nM), favoring EGFR binding. Affibody specificity was confirmed through a cross-reactivity test with proteins of TNF-receptor superfamily and 21 cell lines expressing 4-1BB or not. In cytotoxicity assays, AM105 exhibited superior tumor cell killing compared to cetuximab, particularly in EGFR-expressing cell lines. Notably, AM105 displayed remarkable efficacy in cell lines harboring RAS and/or BRAF mutations, traditionally unresponsive to EGFR-targeting treatments. In vivo experiments utilizing humanized 4-1BB mice demonstrated AM105's exceptional tumor cell elimination compared to cetuximab. The anti-tumor effects persisted even in the face of new tumor cell introductions, suggesting the induction of T cell memory function. Our findings collectively establish AM105 as a potent therapeutic agent with strong anti-tumor T cell activity. The unique 4-1BB based Affibodies (AffiMab format) of AM105 holds promise for addressing the limitations of current bispecific antibodies, positioning it as a potential breakthrough in cancer immunotherapy. Citation Format: Dong-Wook Kim, Hyun-Jong Lee, Seong Yeol Kim, Min Yoon, Youngha Lee, In-Sik Hwang, Yoon Lee, Jong-Hoon Kim, Jong-Seo Lee. AM105: A novel bispecific antibody with Anti 4-1BB affibodies and EGFR antibody [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6353.

Abstract Chimeric antigen receptor (CAR) T cells targeting CD19 or the B cell maturation antigen (BCMA) have demonstrated impressive initial clinical responses. However, on follow-up assessment, a notable fraction of the patients with significant initial clinical response eventually experienced relapse. CAR T cell therapies targeting solid tumors have shown an even lower rate of clinical response as well as shorter remission periods. A prior study has shown that re-injection of the anti-HER2 CAR T cells was effective in a rhabdomyosarcoma relapse patient (Cancer Res 79, LB147 (2019)), but the repeated production of CAR T cells is costly, thus raising questions about its feasibility in practice. Previously, we developed a cotinine-based CAR T cell system (zCART) comprised of a tumor antigen-specific affibody conjugated with cotinine and an anti-cotinine scFv CAR, and demonstrated the anti-tumor activity of an anti-HER2 zCART treatment in both in vitro and in vivo settings. In this study, we tested the efficacy of anti-HER2 zCART treatment in vivo using an intraperitoneal (IP) tumor model with a single infusion of zCART cells. The anti-HER2 switch was injected daily for 7 days. When the HER2 positive tumor relapsed, the mice were re-treated with the same dose of anti-HER2 switch treatment for an additional 7 days. We observed that re-injection of only the anti-HER2 switch and not combined with zCART cells effectively and potently inhibited relapse of HER2 positive tumors. Furthermore, the efficacy of the anti-HER2 switch re-injection treatment was maintained in one additional relapse. In summary, the zCART system has potential to treat cancer relapse following CAR T cell therapy without the need for an additional production round of CAR T cells. Citation Format: Ki Hyun Kim, Soohwan Kim, Eun-Hoe Lee, Soo-Yoon Lim, Sung Min Kim, E-Young Kim, Hyun-Jong Lee, Seong Yeol Kim, Min Yoon, Young-Ha Lee, In-Sik Hwang, Yoon Lee, Jong-Hoon Kim, Jong-Seo Lee, Junho Chung. Potent inhibition of tumor relapse after anti-HER2 affibody tagged with cotinine (switch) plus anti-cotinine switchable CAR T cell therapy by repeated re-injection of the switch [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6314.

7035 Background: All the FDA-approved CD19 CAR-T products are based on FMC63 scFv, which binds to the membrane-distal region of CD19. We developed a novel anti-CD19 antibody clone (1218) binding to a membrane-proximal epitope of CD19 with fast on/off kinetics. AT101 is an autologous CAR-T cell transduced with a lentiviral vector encoding CAR comprised of a humanized scFv of 1218, 4-1BB costimulatory, and CD3zeta domain. Methods: In the phase 1 trial, patients (n=3 per dose level; up to n=18 in total) are treated with AT101 in 3 dose-escalation cohorts based on a standard 3 + 3 design. Each patient received a single intravenous dose of AT101 at dose level (DL) 1 (0.2 x 10 6 cells/kg), DL2 (1.0 x 10 6 cells/kg), or DL3 (5.0 x 10 6 cells/kg). The primary objective is to determine the safety, the maximum tolerated dose, and the recommended phase 2 dose of AT101. Key eligibility criteria include patients aged ≥19 with histologically confirmed relapsed or refractory B-cell non-Hodgkin lymphoma (NHL). Tumor responses were evaluated using Lugano 2014 criteria at 4 weeks before AT101 infusion as well as at 4 weeks and 3, 6, 9, 12, and 18 months after AT101 infusion. Results: From March 2022 to December 2022, fourteen patients were enrolled and 12 patients were treated, who were their median age of 62.5 years (range 39 to 84) and received a median of three prior lines of therapy (range 2-9). Their subtypes were as follows: diffuse large B cell lymphoma (DLBCL; n=7, 58.3%), follicular lymphoma (FL; n=3, 25.0%), mantle cell lymphoma (MCL; n=1, 8.3%), or marginal zone lymphoma (MZL; n=1, 8.3%)). The data collection cut-off date was January 31, 2024. Based on the best overall response up to three months, eleven patients responded with an overall response rate (ORR) of 91.7%, and a complete response (CR) was observed in nine patients (75%). Remarkably, in DL2 and DL3 groups, the CR was 100.0%. Among nine patients who achieved CR, seven patients have remained in CR during the median follow-up of 13.6 months (1.6-22.3 months). One patient experienced relapse and another one died from septic shock. The median duration of response (DOR), progression-free survival (PFS), overall survival (OS), and event-free survival (EFS) were 19.5, 17.2, 18.9 and 17.2 months, respectively. The median DOR, PFS, OS and EFS were not reached. Conclusions: In this first-in-human phase 1 trial, AT101 was tolerable with limited and manageable toxicities. In comparison to current FMC63 scFv-based CD19 CAR-T therapies, AT101 exhibited potent and more enduring efficacy with a remarkable suppression of relapse after CR. A phase 2 clinical trial is currently under-going for DLBCL patients. Clinical trial information: NCT05338931 .

7522 Background: All the FDA-approved CD19 CAR-T products are based on FMC63 scFv, which binds to the membrane-distal region of CD19. We developed a novel anti-CD19 antibody clone (1218) that binds to a membrane-proximal epitope of CD19, thereby not competing with FMC63. AT101 is an autologous CAR T cell transduced with a lentiviral vector, including the CD19-CAR with a humanized scFv of 1218, 4-1BB costimulatory, and CD3zeta domain. Methods: In this phase 1 trial, patients (n = 3 per dose level; up to n = 18 in total) are treated with AT101 in 3 dose-escalation cohorts based on a standard 3 + 3 design. Each patient received a single intravenous dose of AT101 at dose level (DL) 1 (0.2 x 10 6 cells/kg), DL2 (1.0 x 10 6 cells/kg), or DL3 (5.0 x 10 6 cells/kg). The primary objective is to determine the safety, the maximum tolerated dose (MTD), and the recommended phase 2 dose (RP2D) of AT101. The secondary objective is to evaluate the pharmacokinetics of AT101 and the preliminary efficacy, such as overall response rate (ORR), duration of response (DOR), progression-free survival (PFS), event-free survival (EFS), and overall survival (OS). Key eligibility criteria include patients aged ≥19 with histologically confirmed relapsed or refractory B-cell non-Hodgkin lymphoma (NHL). Results: Fourteen patients were enrolled from March 2022 to December 2022, and nine were treated. The median age of treated patients was 61.6 years (ranged from 39 to 84) after a median of 4 prior lines of therapy (range 2-10). Their subtypes of NHL were as follows: diffuse large B cell lymphoma (n = 4), follicular lymphoma (n = 3), mantle cell lymphoma (n = 1), or marginal zone lymphoma (n = 1). The dosing of AT101 at DL1 and DL2 was completed. The dosing at DL3 is ongoing. Across cohorts 1 and 2, no grade 3 or higher cytokine release syndrome (CRS) was reported. Among the first three patients at DL1, one dose-limiting toxicity (DLT) of grade 4 neurotoxicity was observed but resolved in a week without sequelae. No other DLTs were observed in the additional three patients at the DL1 and three at the DL2 cohort. Another one at DL2 experienced grade 1 CRS with grade 1 neurotoxicity. Five patients experienced Grade ≥3 hematologic toxicities. An ORR is 66.7% (4/6) in cohort 1 and 100% (3/3) in cohort 2, including six complete responses (CR, 50.0% [3/6] in cohort 1 and 100% [3/3] in cohort 2). As of February 13, 2023, all six CRs are ongoing, including two patents exceeding six months after the treatments. Updated results will be presented at the meeting, including the cohort of DL3. Conclusions: In this phase I study, AT101 was well tolerated at the first two dose levels and showed promising efficacy in relapsed or refractory B-cell NHL patients. The majority of adverse effects were transient and manageable. The administrations of DL3 are currently ongoing, and updated results will be presented at the meeting. Clinical trial information: NCT05338931 .

Introduction: Anti-CD19 chimeric antigen receptor T-cell therapies (CART19) are highly efficacious against advanced B cell non-Hodgkin lymphoma (NHL) but the majority of patients (pts) ultimately fail. Several mechanisms contribute to CART19 failure, including CD19-neg escape and CART dysfunction. Notably, all four commercial CART19 products utilize the FMC63 single chain variable fragment (scFv) with high-avidity specificity to a CD19 membrane-distal epitope. Interestingly, loss of the FMC63-recognized epitope due to CD19 mutations ( Zhang Z, JITC, 2020) or epitope-masking (CAR19:CD19) ( Ruella M, Nat Med, 2018) has been described. We hypothesized that a novel anti-CD19 scFv that engages an alternative CD19 membrane-proximal epitope independent of FMC63 with low avidity could: 1. mitigate CD19 epitope loss; but also 2. enhance CART functions ( Fig. 1A) . Methods and results: We developed an autologous, CART19 product with 4-1BB co-stimulation using a novel humanized chicken antibody (h1218) specific to a membrane-proximal epitope of CD19 (amino acids T51,S53, E55,K59 and K63). We previously reported initial preclinical data ( Patel R., ASH, 2021 #2798) that demonstrated h1218-CART19 recognize and kill B-cell leukemia that aberrantly expresses the FMC63-CAR19. More recently, we demonstrated that differently than FMC63-based CART, h1218-CART19 could respond to and kill tumor cells expressing point mutations of CD19 (L174V and R163L). Of note, h1218-CART19 had enhanced control of CD19+ B-cell neoplasms as compared to FMC63-CART19 both in vitro and in vivo. Mechanistically, thanks to the lower avidity and faster on/off rate, h1218-CART19 had decreased T cell exhaustion and activation-induced cell death. Given the promising preclinical results, we tested the clinical h1218-CART19 product (AT101) in a first-in-human, multi-center, phase I/II, dose-escalation clinical trial for pts with histologically confirmed relapsed or refractory B cell NHL (NCT05338931). For the phase I study, pts were treated with a single intravenous infusion of AT101 (day 0) in three dose levels (DL) based on a standard 3+3 design: DL1 (0.2 x 10 6 cells/kg), DL2 (1.0 x 10 6 cells/kg), or DL3 (5.0 x 10 6 cells/kg). All pts received lymphodepletion with intravenous fludarabine (250 mg/m 2) and cyclophosphamide (25 mg/m 2) on days -4, -3, and -2. The primary objective was to determine the maximum tolerated dose (MTD) of AT101. The secondary objectives were to evaluate AT101 pharmacokinetics and preliminary efficacy. At the July 3, 2023 data cut, 12 pts (median age 62.5 years (range 39-84); diffuse large B cell lymphoma (DLBCL, n=7, 58.3%), follicular lymphoma (FL, n=3, 25.0%), mantle cell lymphoma (MCL, n=1, 8.3%), and marginal zone lymphoma (MZL, n=1, 8.3%)) received AT101 ( Fig. 1B). The median follow-up after AT101 was 6.5 months (1.5-13.7 months), the median number of previous lines of treatment 3 (range 1-8); no prior cellular therapies. Five pts (41.7%) had previous autologous stem cell transplantation. Two pts (16.7%) had refractory disease and two pts (16.7%) received bridging therapy. Three pts (2 pts at DL2 and 1 pt at DL3) developed a grade (G) 1 cytokine-release syndrome (CRS) and one pt at DL3 developed a G3 CRS that resolved within 24 hours. Three pts (1 pt at each DL) developed immune-cell-related neurotoxicity syndrome (ICANS), of which one G4 dose-limiting toxicity (DLT) was reported at DL1 that corrected within 6 days. One DL3 pt experienced G3 sepsis that promptly resolved; the same pt ultimately developed fatal neutropenic septic shock outside the DLT period. Four additional patients experienced ≥G3 neutropenia without evidence of infection. Complete response (CR) occurred in 8/12 pts (66.6%) and overall response (CR+partial response) in 83.3% (95%CI, 51.6-97.9) at day 28 post-AT101 infusion ( Fig. 1B). Remarkably, in DL2 and DL3, the CR rate was 100.0%. Of the 8 pts in CR none has relapsed (median follow-up 6.0 months). AT101 cells expanded (peak in DL3 113.6 ± 6.50 x10 4 CAR gene copies/ug DNA) and persisted in patients' blood. Conclusion: In this first-in-human phase I trial, AT101 was tolerable with limited and manageable toxicities. Notable preliminary efficacy was observed at the RP2D with no evidence of disease relapse after achieving a CR. These results warrant the pursuit of the planned phase II expansion cohort.

Background Commercial anti-CD19 chimeric antigen receptor T-cell therapies (CART19) are efficacious against advanced B-cell non-Hodgkin lymphoma (NHL); however, most patients ultimately relapse. Several mechanisms contribute to this failure, including CD19-negative escape and CAR T dysfunction. All four commercial CART19 products utilize the FMC63 single-chain variable fragment (scFv) specific to a CD19 membrane-distal epitope and characterized by slow association (on) and dissociation (off) rates. We hypothesized that a novel anti-CD19 scFv that engages an alternative CD19 membrane-proximal epitope independent of FMC63 and that is characterized by faster on- and off-rates could mitigate CART19 failure and improve clinical efficacy. Methods We developed an autologous CART19 product with 4-1BB co-stimulation using a novel humanized chicken antibody (h1218). This antibody is specific to a membrane-proximal CD19 epitope and harbors faster on/off rates compared to FMC63. We tested h1218-CART19 in vitro and in vivo using FMC63-CART19-resistant models. We conducted a first-in-human multi-center phase I clinical trial to test AT101 (clinical-grade h1218-CART19) in patients with relapsed or refractory (r/r) NHL. Results Preclinically, h1218- but not FMC63-CART19 were able to effectively eradicate lymphomas expressing CD19 point mutations (L174V and R163L) or co-expressing FMC63-CAR19 as found in patients relapsing after FMC63-CART19. Furthermore, h1218-CART19 exhibited enhanced killing of B-cell malignancies in vitro and in vivo compared with FMC63-CART19. Mechanistically, we found that h1218-CART19 had reduced activation-induced cell death (AICD) and enhanced expansion compared to FMC63-CART19 owing to faster on- and off-rates. Based on these preclinical results, we performed a phase I dose-escalation trial, testing three dose levels (DL) of AT101 (the GMP version of h1218) using a 3 + 3 design. In 12 treated patients (7 DLBCL, 3 FL, 1 MCL, and 1 MZL), AT101 showed a promising safety profile with 8.3% grade 3 CRS ( n = 1) and 8.3% grade 4 ICANS ( n = 1). In the whole cohort, the overall response rate was 91.7%, with a complete response rate of 75.0%, which improved to 100% in DL-2 and -3. AT101 expansion correlates with CR and B-cell aplasia. Conclusions We developed a novel, safe, and potent CART19 product that recognizes a membrane-proximal domain of CD19 with fast on- and off-rates and showed significant efficacy and promising safety in patients with relapsed B-cell NHL. Trial registration NCT05338931; Date: 2022–04-01.

Abstract Background and Preliminary Data: All the FDA-approved CD19 CAR-T cell therapies are based on an antigen-binding domain (scFv) based on the FMC63 antibody which binds to the membrane-distal region of CD19 to an epitope encoded by exons 3 and 4 (Klesmith JR, Biochemistry, 2019; Zhang Z, JITC, 2020). While these CART19 products are very effective in the clinic, the majority of patients still do not respond or eventually relapse due to several mechanisms of resistance, including T cell dysfunction and epitope CD19-negative escape. Novel strategies to enhance the activity of CART cells and reduce escape are critically needed. We recently demonstrated that modifications of the binding region of the CAR (scFv) (Singh N., Nat Med, 2021) can drastically change the interaction between the CAR T cell and the cancer cells, potentially improving the anti-tumor effect. To this goal, we developed a novel anti-CD19 antibody clone (1218) that binds to a membrane-proximal epitope of CD19 (exon 2 region K59-K63) thereby not competing with FMC63. We developed a novel CART19, called AT101, using a humanized 1218 scFv along with 4-1BB costimulatory and CD3zeta domain in a lentiviral backbone. In preclinical models, AT101 showed more potent in vitro cytotoxicity against CD19-positive B lymphoma cells in a long-term killing assay and in a B-ALL (NALM6) in vivo model as compared to the control of FMC63 based CAR-T cells. In addition, differently than FMC63-based CART, AT101 could target tumor cells expressing point mutations of CD19 that are associated with relapse post-CART19 (FMC63) (Zhang Z, JITC, 2020) and leukemic blasts aberrantly expressing FMC63 CAR19 on their surface (Ruella M, Nat Med, 2018). Based on the preclinical efficacy and safety, a phase 1 clinical trial testing autologous AT101 was started for patients with relapsed and refractory B-cell non-Hodgkin lymphoma. Trial Design and Methods: This open-label, multi-center, first-in-human Phase 1 study will assess the safety and feasibility of AT101 in patients with relapsed or refractory B cell non-Hodgkin lymphoma. Key eligibility criteria include patients aged ≥19 years of age with histologically confirmed relapsed or refractory aggressive B-cell non-Hodgkin lymphoma. In this phase 1 trial, patients (n=3 per dose level; up to n=18 in total) are treated with AT101 in 3 dose-escalation cohorts based on a standard 3 + 3 design. CART doses are 2.0 × 105, 1.0 × 106, or 5.0 × 106 CAR+T cells/kg. The primary objective is to determine the safety, the maximum tolerated dose (MTD), and the recommended phase 2 dose (RP2D) of AT101 in participants following lymphodepletion with cyclophosphamide and fludarabine (250 mg/m2 and 25 mg/m2). The secondary objective is to evaluate the preliminary efficacy assessments (overall response rate (ORR), duration of response (DOR), progression-free survival (PFS), overall survival (OS), event-free survival (EFS), and pharmacokinetics of AT101. Exploratory objectives include assessment of CD19 expression and cytokines in the blood. Patients will be followed for safety for at least 60 months post AT101 infusion. Clinical trial registry number: NCT05338931. As of January 11, 2023, AT101 has been infused to six patients in cohort 1 and three patients in cohort 2. Detailed results will be presented at the meeting. Citation Format: Yunlin Zhang, Ki Hyun Kim, Dok Hyun Yoon, Ruchi P. Patel, Jae-Cheol Jo, Hyungwoo Cho, Jong-Ho Lee, Hyun-Jong Lee, Lei-Guang Cui, In-Sik Hwang, Young Ha Lee, Jong-Hoon Kim, Yong Gu Lee, Puneeth Guruprasad, Jong-Seo Lee, Junho Chung, Marco Ruella. An open label, dose escalation, phase 1 study of AT101, a novel CD19-directed CAR-T cell therapy targeting a membrane-proximal epitope of CD19, in patients with relapsed or refractory B cell non-Hodgkin lymphoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr CT130.

The generation of human oligodendrocyte progenitor cells (OPCs) may be therapeutically valuable for human demyelinating diseases such as multiple sclerosis. Here, we report the direct reprogramming of human somatic cells into expandable induced OPCs (iOPCs) using a combination of OCT4 and a small molecule cocktail. This method enables generation of A2B5 + (an early marker for OPCs) iOPCs within 2 weeks retaining the ability to differentiate into MBP-positive mature oligodendrocytes. RNA-seq analysis revealed that the transcriptome of O4 + iOPCs was similar to that of O4 + OPCs and ChIP-seq analysis revealed that putative OCT4-binding regions were detected in the regulatory elements of CNS development-related genes. Notably, engrafted iOPCs remyelinated the brains of adult shiverer mice and experimental autoimmune encephalomyelitis mice with MOG-induced 14 weeks after transplantation. In conclusion, our study may contribute to the development of therapeutic approaches for neurological disorders, as well as facilitate the understanding of the molecular mechanisms underlying glial development.

Autologous T cells engineered to express a chimeric antigen receptor (CAR-T cells) have shown impressive outcomes in hematologic malignancies. However, safety concerns derived from the inability to control CAR-T cells in vivo remain a significant challenge to expand the application of CAR-T cell therapy. Switchable CAR-T cells can allow for turning on and off the activation and cytotoxicity of CAR-T cells in vivo, potentially increasing the safety of next-generation CART products. To this goal, CAR constructs targeting non-tumor antigens, e.g., haptens and peptide tags, can be designed and combined with tumor-targeting units that are fused to the hapten or peptide tag. In this study, we developed a novel switchable CAR-T system using cotinine as the hapten and an anti-cotinine CAR-T cell product. Of note, cotinine is physiologically absent in human and pharmacologically inert. A mouse antibody to cotinine was developed and successfully humanized. The anti-cotinine CAR confirmed to be displayed on T-cell surface. We first tested this approach to target epidermal growth factor receptor 2 (HER2) in ovarian cancer. To target HER2, we developed an affibody-based antigen binding domain characterized by high stability, broad spectrum of specificity, and feasibility of large scale chemical synthesis. In in vitro cytotoxicity and cytokine release assays, the activity of CAR-T cells was controlled by cotinine-tagged anti-HER2 affibody in a HER2-specific and dose-dependent manner. We synthesized the cotinine-tagged HER2 affibodies using single isoform cotinine and selected the optimal cotinine-tagged anti-HER2 affibody at the cotinine-based switchable CAR-T system. In an orthotopic ovarian cancer model using NSG mice engrafted with SKOV3, tumor regression was observed only when CAR-T cells were administered in combination with the cotinine-tagged HER2 affibody. In subsequent studies, we demonstrated that the cotinine-based switchable CAR-T system can be applied to other tumor targets such as mesothelin and epidermal growth factor receptor (EGFR). Additional studies are ongoing to determine the kinetics of the on and off CAR-T activation of this system and define the optimal dosing strategy to ensure anti-tumor effect or to interrupt toxicity. In conclusion, we have developed a novel switchable cotinine-based CAR-T system to control CAR-T function in vivo and that could be broadly applicable to wide variety of tumors.

Abstract CD19-directed chimeric antigen receptor T (CART19) cell therapies have shown impressive clinical outcomes in CD19+ B cell malignancies. All the FDA-approved CART19, including tisagenlecleucel, axicabtagene ciloleucel, and brexucabtagene autoleucel use anti-CD19 single-chain variable fragments (scFv) that bind to the same CD19 epitope. This epitope is located at the membrane-distal portion of CD19. We aimed to develop an anti-CD19 CAR that binds to a membrane-proximal domain. To this goal, we screened a chicken immune scFv library against the CD19 extracellular domain. We selected an scFv clone (1218) that was not competing with FMC63 for CD19 binding in competition enzyme immunoassay and real-time interaction analysis. Subsequent mutagenesis assay by replacing several residues with monkey residues showed that, as compared to FMC63, the epitope of the 1218 scFv is localized in a membrane-proximal location at three-dimensional modeling (Teplyakov A., Proteins, 2018). The chicken 1218 scFv was humanized by CDR-grafting to human germline genes and backmutations (h1218 scFv) and was confirmed to be specific for CD19 in cell microarray assays and flow cytometry analysis. We, therefore, designed a CAR construct using the h1218 scFv, 41-BB costimulatory domain in a lentiviral backbone. CAR-T cells were successfully generated using the Myltenyi Prodigy platform. In vitro cytotoxicity and interferon release assays showed potent effector functions of h1218 CAR-T cells that compared positively with FMC63-based CART19. Our group recently described the occurrence of a B-cell leukemia relapse characterized by the expression of the CAR19 itself on the cell surface due to accidental transduction during manufacturing (Ruella M., Nat Med, 2018). Interestingly, h1218 but not FMC63 CART19 were able to recognize and kill FMC63 CAR19-expressing tumor cells. In vivo, h1218 CART19 cells led to complete tumor regressions in both Raji (CD19+ B-cell lymphoma) and Nalm-6 (B-cell leukemia) xenograft models. Currently, h1218 CART19 is under advanced preclinical development and will be tested in a phase I-II clinical trial for relapsed and refractory B-cell lymphoma patients. Citation Format: Ki-Hyun Kim, Ruchi P. Patel, Yong Gu Lee, Soohwan Kim, Ji-Hyeon Choi, Sung-Min Kim, Gae-Baik Kim, Jong-Ho Lee, Hyun-Jong Lee, Ji-Ho Park, Guewha Lee, LeiGuang Cui, Min Yoon, Ki Hyun Kim, Soohyun Kim, In-Sik Hwang, Youngha Lee, Bong-Kook Ko, Jong-Seo Lee, Junho Chung, Marco Ruella. A novel anti-CD19 chimeric antigen receptor T cell product targeting a membrane-proximal domain of CD19 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr LB030.

Introduction: CD19-directed chimeric antigen receptor T (CART19) cell therapies have shown impressive clinical outcomes in CD19+ B-cell malignancies. All the FDA-approved CART19, including tisagenlecleucel, axicabtagene ciloleucel, brexucabtagene autoleucel, and lisocabtagene maraucel use an anti-CD19 single-chain variable fragments (scFv) derived from the FMC63 antibody that binds to a CD19 epitope that is located in the membrane-distal portion of CD19. While this CART19 products are very effective in the clinic, the majority of patients still fails treatment or eventually relapses due to several mechanisms of resistance, including CAR T cell dysfunction in the immunosuppressive microenvironment. Novel strategies to enhance the activity of CART cells are critically needed. We and others recently demonstrated that modifications of the binding region of the CAR (scFv) (Singh N., Nat Med, 2021) can drastically change the interaction between the CAR T cell and the cancer cells, potentially improving the anti-tumor effect. In this study, we aimed to develop a novel anti-CD19 CAR that binds to a membrane-proximal domain of CD19 with the goal of improving CART functions. Moreover, we hypothesized that such a CART product would be active against B-cell acute lymphoblastic leukemia (B-ALL) blasts that present aberrant expression of the CAR19(FMC63) on the surface as we described in two pediatric B-ALL patients relapsed after CART19 (CTL019) at our Institution (Ruella M., Nat Med, 2018).

Autologous T cells engineered to express a chimeric antigen receptor (CAR-T cells) have shown impressive outcomes in hematologic malignancies. However, safety concerns derived from the inability to control CAR-T cells in vivo remain a significant challenge to expand the application of CAR-T cell therapy. Switchable CAR-T cells can allow for turning on and off the activation and cytotoxicity of CAR-T cells in vivo, potentially increasing the safety of next-generation CART products. To this goal, CAR constructs targeting non-tumor antigens, e.g., haptens and peptide tags, can be designed and combined with tumor-targeting units that are fused to the hapten or peptide tag. In this study, we developed a novel switchable CAR-T system using cotinine as the hapten and an anti-cotinine CART cell product. Of note, cotinine is physiologically absent in human and pharmacologically inert. A mouse antibody to cotinine was developed and successfully humanized. The anti-cotinine CAR confirmed to be displayed on T-cell surface. We first tested this approach to target epidermal growth factor receptor 2 (HER2) in ovarian cancer. To target HER2, we developed an affibody-based antigen binding domain characterized by high stability, broad spectrum of specificity, and feasibility of large scale chemical synthesis. In in vitro cytotoxicity and cytokine release assays, the activity of CAR-T cells was controlled by cotinine-tagged anti-HER2 affibody in a HER2-specific and dose-dependent manner. In an orthotopic ovarian cancer model using NSG mice engrafted with SKOV3, tumor regression was observed only when CAR-T cells were administered in combination with the cotinine-tagged HER2 affibody. In subsequent studies, we demonstrated that the cotinine-based switchable CAR-T system can be applied to other tumor targets such as mesothelin and epidermal growth factor receptor (EGFR). Additional studies are ongoing to determine the kinetics of the on and off CART activation of this system and define the optimal dosing strategy to ensure anti-tumor effect or to interrupt toxicity. In conclusion, we have developed a novel switchable cotinine-based CART system to control CART function in vivo and that could be broadly applicable to wide variety of tumors. Citation Format: Ki-Hyun Kim, Soohwan Kim, Ji-Hyeon Choi, Sung-Min Kim, Gae-Baik Kim, Jong-Ho Lee, Hyun-Jong Lee, Sang-Ho Ahn, Guewha Lee, LeiGuang Cui, Seong Yeol Kim, Min Yoon, Ki Hyun Kim, Soohyun Kim, Juwon Lee, Youngjin Han, Youngha Lee, In-Sik Hwang, Bong-Kook Ko, Jong-Seo Lee, Yong Sang Song, Marco Ruella, Junho Chung. A novel cotinine-based system for switchable chimeric antigen receptor T cell immunotherapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr LB149.

Cancer stem cells (CSCs) have been implicated in the growth and progression of several types of human cancer. The technology to derive and establish CSCs in vitro could be a critical tool for understanding cancer and developing new therapeutic targets. In this study, we derived expandable CD15+ induced CSCs (iCSCs) from immortalised 293FT human epithelial cells by co-culture with human bone marrow-derived mesenchymal stem cells (BM-MSCs) as feeder cells in vitro. The iCSCs converted through an epithelial-mesenchymal transition program acquired mesenchymal traits, the expression of stem cell markers, and epigenetic changes. Moreover, the iCSCs not only efficiently formed tumorspheres in vitro but also initiated tumours in immunocompromised mice injected with only 10 of the iCSCs. Furthermore, we showed that the expression of the chemokine CXCL12 and its receptor CXCR4 by the iCSCs resulted in the activation of the Fut4 gene through CXCR4/ERK/ELK-1-signalling pathways and the maintenance of the iCSCs in the undifferentiated state through CXCR4/AKT/STAT3-signalling. These findings suggest that immortalised 293FT cells may acquire potential oncogenicity through molecular and cellular alteration processes in microenvironments using BM-MSCs, and could represent a valuable in vitro model as a cancer stem cell surrogate for studying the pathophysiological properties of CSCs.

UV-induced skin damage is involved in ROS overproduction and the overexpression of matrix metalloproteinases (MMPs), which are inhibited by TIMPs (tissue inhibitor of neural stem cells (NSCs)). These proteins may be associated with skin regeneration through the activation of TIMP proteins, but there have been no reports of treatment of skin photodamage using NSCs and their secreted proteins TIMP-1 and TIMP-2. Here we investigated the photoprotective role of NSCs and their TIMP proteins for the inhibition of UVB-irradiation damage in fibroblasts in SKH-1 mice. SKH-1 hairless mice were divided into three groups (n = 4 per group): normal, treatment, and control groups. The latter two groups were dorsally exposed to UVB irradiation for 12 weeks. After UVB irradiation, treatments with NSC-CM and its secreted factors TIMP-1 and TIMP-2, markedly ameliorated the photodamage triggered by the increase in MMP expression and activity through ROS production, and the subsequent activation of the NF-κB pathway in UVB-irradiated fibroblasts and the treatment mouse group. In addition, the topical application of NSC-CM to mice in the treatment group after irradiation clearly inhibited the expression of γ-H2AX, a DNA damage marker, through the activation of the DNA repair enzyme Rad50. These results demonstrate that NSC-CM or TIMPs proteins can ameliorate skin photodamage induced by UVB-irradiation in in vitro and in vivo systems.

Pluripotent stem cells (PSCs) can serve as an unlimited cell source for transplantation therapies for treating various devastating diseases, such as cardiovascular diseases, diabetes, and Parkinson's disease. However, PSC transplantation has some associated risks, including teratoma formation from the remaining undifferentiated PSCs. Thus, for successful clinical application, it is essential to ablate the proliferative PSCs before or after transplantation. In this study, neural stem cell-derived conditioned medium (NSC-CM) inhibited the proliferation of PSCs and PSC-derived neural precursor (NP) cells without influencing the potential of PSC-NP cells to differentiate into neurons in vitro and prevented teratoma growth in vivo. Moreover, we found that the NSC-CM remarkably decreased the expression levels of Oct4 and cyclin D1 that Oct4 directly binds to and increased the cleaved-caspase 3-positive cell death through the DNA damage response in PSCs and PSC-NPs. Interestingly, we found that NSCs distinctly secreted the tissue inhibitor of metalloproteinase (TIMP)-1 and TIMP-2 proteins. These proteins suppressed not only the proliferation of PSCs in cell culture but also teratoma growth in mice transplanted with PSCs through inhibition of matrix metalloproteinase (MMP)-2 and MMP-9 activity. Taken together, these results suggest that the TIMP proteins may improve the efficacy and safety of the PSC-based transplantation therapy.

PURPOSE:Tumor-associated macrophages (TAMs) are activated macrophages associated with tumor progression in various cancers. TAMs can polarize M1 or M2 type. M1 has a pro-inflammatory function and kills pathogens. Conversely, M2 shows immunosuppressive action and promotes tumor growth. There are various markers of TAMs. CD11c is considered as a specific marker of M1. CD163 is an optimal marker for M2. CD68 is known as a pan-macrophage marker. We evaluated the relationship between the clinicopathological parameters and immunohistochemical expressions of CD11c, CD163, and CD68 in invasive breast cancer (IBC), and the prognostic value of macrophage localization within the tumor stroma (TS) and tumor nest (TN).METHODS:Immunohistochemistry of CD68, CD11c, and CD163 was analyzed on tissue microarrays of 367 IBCs. The number of CD68+, CD11c+, or CD163+ macrophages in TN vs. TS was counted by 2 pathologists. The correlations between the degree of macrophage (CD68+, CD11c+, or CD163+) infiltration and the clinicopathological parameters were analyzed. We also assessed the impact of macrophages (CD68+, CD11c+, or CD163+) on disease free survival (DFS) and overall survival (OS).RESULTS:High numbers of macrophages (CD68+, CD11c+, or CD163+) were associated with higher histologic grade, higher Ki-67 proliferating index, estrogen receptor negativity, and progesterone receptor negativity. High numbers of macrophages (CD11c+ or CD163+) in TS were associated with a larger tumor size. Furthermore, CD163+ macrophages in TN were an independent prognostic marker of reduced OS and DFS. Conversely, CD11c+ macrophages in TS were an independent prognostic marker for higher OS and DFS.CONCLUSION:TAMs, including M2 type, are associated with tumor progression in IBC. They can also act as a significant unfavorable or favorable prognostic factor. In addition to simply analyzing the degree of TAM infiltration, it is also important to analyze the location of TAMs.

The pigment molecule, melanin, is produced from melanosomes of melanocytes through melanogenesis, which is a complex process involving a combination of chemical and enzymatically catalyzed reactions. The synthesis of melanin is primarily influenced by tyrosinase (TYR), which has attracted interest as a target molecule for the regulation of pigmentation or depigmentation in skin. Thus, direct inhibitors of TYR activity have been sought from various natural and synthetic materials. However, due to issues with these inhibitors, such as weak or permanent ability for depigmentation, allergy, irritant dermatitis and rapid oxidation, in vitro and in vivo, the development of new materials that inhibit melanin production is essential. A conditioned medium (CM) derived from stem cells contains many cell-secreted factors, such as cytokines, chemokines, growth factors and extracellular vesicles including exosomes. In addition, the secreted factors could negatively regulate melanin production through stimulation of a microenvironment of skin tissue in a paracrine manner, which allows the neural stem cell CM to be explored as a new material for skin depigmentation. In this review, we will summarize the current knowledge regulating depigmentation, and discuss the potential of neural stem cells and their derivatives, as a new material for skin depigmentation.