CLDN18.2 BiTE Engages Effector and Regulatory T Cells for Antitumor Immune Response in Preclinical Models of Pancreatic Cancer

BACKGROUND & AIMS

BiTE (bispecific T-cell engager) immune therapy has demonstrated clinical activity in multiple tumor indications, but its influence in the tumor microenvironment remains unclear. CLDN18.2 is overexpressed in solid tumors including gastric cancer (GC) and pancreatic ductal adenocarcinoma (PDAC), both of which are characterized by the presence of immunosuppressive cells, including regulatory T cells (Tregs) and few effector T cells (Teffs).

METHODS

We evaluated the activity of AMG 910, a CLDN18.2-targeted half-life extended (HLE) BiTE molecule, in GC and PDAC preclinical models and cocultured Tregs and Teffs in the presence of CLDN18.2-HLE-BiTE.

RESULTS

AMG 910 induced potent, specific cytotoxicity in GC and PDAC cell lines. In GSU and SNU-620 GC xenograft models, AMG 910 engaged human CD3+ T cells with tumor cells, resulting in significant antitumor activity. AMG 910 monotherapy, in combination with a programmed death-1 (PD-1) inhibitor, suppressed tumor growth and enhanced survival in an orthotopic Panc4.14 PDAC model. Moreover, Treg infusion enhanced the antitumor efficacy of AMG 910 in the Panc4.14 model. In syngeneic KPC models of PDAC, treatment with a mouse surrogate CLDN18.2-HLE-BiTE (muCLDN18.2-HLE-BiTE) or the combination with an anti-PD-1 antibody significantly inhibited tumor growth. Tregs isolated from mice bearing KPC tumors that were treated with muCLDN18.2-HLE-BiTE showed decreased T cell suppressive activity and enhanced Teff cytotoxic activity, associated with increased production of type I cytokines and expression of Teff gene signatures.

CONCLUSIONS

Our data suggest that BiTE molecule treatment converts Treg function from immunosuppressive to immune enhancing, leading to antitumor activity in immunologically "cold" tumors.

Characterization and root cause analysis of immunogenicity to pasotuxizumab (AMG 212), a prostate-specific membrane antigen-targeting bispecific T-cell engager therapy

Introduction

In oncology, anti-drug antibody (ADA) development that significantly curtails response durability has not historically risen to a level of concern. The relevance and attention ascribed to ADAs in oncology clinical studies have therefore been limited, and the extant literature on this subject scarce. In recent years, T cell engagers have gained preeminence within the prolific field of cancer immunotherapy. These drugs whose mode of action is expected to potently stimulate anti-tumor immunity, may potentially induce ADAs as an unintended corollary due to an overall augmentation of the immune response. ADA formation is therefore emerging as an important determinant in the successful clinical development of such biologics.

Methods

Here we describe the immunogenicity and its impact observed to pasotuxizumab (AMG 212), a prostate-specific membrane antigen (PSMA)-targeting bispecific T cell engager (BiTE®) molecule in NCT01723475, a first-in-human (FIH), multicenter, dose-escalation study in patients with metastatic castration-resistant prostate cancer (mCRPC). To explain the disparity in ADA incidence observed between the SC and CIV arms of the study, we interrogated other patient and product-specific factors that may have explained the difference beyond the route of administration.

Results

Treatment-emergent ADAs (TE-ADA) developed in all subjects treated with at least 1 cycle of AMG 212 in the subcutaneous (SC) arm. These ADAs were neutralizing and resulted in profound exposure loss that was associated with contemporaneous reversal of initial Prostate Surface Antigen (PSA) responses, curtailing durability of PSA response in patients. Pivoting from SC to a continuous intravenous (CIV) administration route remarkably yielded no subjects developing ADA to AMG 212. Through a series of stepwise functional assays, our investigation revealed that alongside a more historically immunogenic route of administration, non-tolerant T cell epitopes within the AMG 212 amino acid sequence were likely driving the high-titer, sustained ADA response observed in the SC arm.

Discussion

These mechanistic insights into the AMG 212 ADA response underscore the importance of performing preclinical immunogenicity risk evaluation as well as advocate for continuous iteration to better our biologics.

Abstract 5202: AMG 794, a Claudin 6-targeted half-life extended (HLE) bispecific T cell engager (BITE®) molecule for non-small cell lung cancer and epithelial ovarian cancer

AMG 794 is a half-life extended BiTE® immune therapy targeting the oncofetal antigen Claudin 6 (CLDN6). AMG 794 redirects T cells to kill CLDN6-expressing tumor cells and is being developed for the treatment of non-small cell lung cancer (NSCLC) and epithelial ovarian cancer (EOC). CLDN6 is a compelling tumor antigen that is expressed during embryonic and fetal development, transcriptionally silenced in adult tissues, and re-expressed on the surface of NSCLC and EOC cells. By immunohistochemistry, CLDN6 staining of the cell membrane was observed in 27% of non-squamous NSCLC (n = 63) and 69% of EOC (n = 92) samples, the majority of which were of the high-grade serous ovarian cancer subtype. Expression of CLDN6 protein was not detected in most normal adult tissues, with rare CLDN6 immunostaining limited to individual cells in the pituitary, pancreas, small intestine, kidney, and female reproductive organs. AMG 794 is a fully human BiTE® molecule that binds both human and cynomolgus monkey CLDN6 and CD3. AMG 794 binds human CLDN6 and CD3 with equilibrium dissociation constant (KD) of 13 nM and 36 nM, respectively. In vitro, AMG 794 redirects human T cells to kill CLDN6-expressing cancer cells with a half-maximal lysis concentration (EC50) of 2.6 ± 1.1 pM to 127.4 ± 53.4 pM. Consistent with the mechanism of action of BiTE® immune therapy, AMG 794 induces T cell activation and transient production of cytokines in co-cultures of T cells and CLDN6-expressing tumor cells. Remarkably, AMG 794 binding and cytotoxic activity is selective for CLDN6 over other claudin family proteins, despite high homology in the extracellular loops with CLDN9. Weekly dosing of AMG 794 significantly inhibited the growth of established lung and ovarian xenograft tumors in immunocompromised mice injected with human T cells. Anti-tumor activity was associated with an increase in tumor-infiltrating T cells. AMG 794 was well tolerated in a one-month repeat-dose toxicology study in cynomolgus monkey, with evidence for target engagement. The potent, selective activity of AMG 794 for CLDN6-expressing NSCLC and EOC cells, together with an acceptable nonclinical safety profile, supported the advancement of AMG 794 into clinical development. A first-in-human study to explore the safety, tolerability, pharmacokinetics, and anti-tumor activity of AMG 794 in patients with CLDN6-positive advanced/metastatic non-squamous NSCLC or EOC will be enrolling patients in March 2022.

Citation Format: Elizabeth Pham, Anja Henn, Beate Sable, Joachim Wahl, Kip Conner, Katja Matthes, Shivani Gupta, Rodolfo Yabut, Famke Aeffner, Kristin Lewis Wilson, Jonas Anlahr, Christoph Dahlhoff, Vijay Kale, Matthias Friedrich, Tobias Raum, Peter Kufer, Angela Coxon, Sabine Stienen, Julie M. Bailis. AMG 794, a Claudin 6-targeted half-life extended (HLE) bispecific T cell engager (BITE®) molecule for non-small cell lung cancer and epithelial ovarian cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5202.

Mesothelin/CD3 half-life extended bispecific T-cell engager molecule shows specific tumor uptake and distributes to mesothelin and CD3 expressing tissues

BiTE ® (bispecific T-cell engager) molecules exert antitumor activity by binding one arm to CD3 on cytotoxic T-cells and the other arm to a tumor-associated antigen. We generated a fully mouse cross-reactive mesothelin (MSLN)-targeted BiTE molecule that is genetically fused to a Fc-domain for half-life extension, and evaluated biodistribution and tumor targeting of a zirconium-89 (89Zr)-labeled MSLN HLE BiTE molecule in 4T1 breast cancer bearing syngeneic mice with positron emission tomography (PET). Biodistribution of 50 µg 89Zr-MLSN HLE BiTE was studied over time by PET imaging in BALB/c mice and revealed uptake in tumor and lymphoid tissues with an elimination half-life of 63.4 hours. Compared to a non-targeting 89Zr-control HLE BiTE, the 89Zr-MLSN HLE BiTE showed a 2-fold higher tumor uptake and higher uptake in lymphoid tissues. Uptake in the tumor colocalized with mesothelin expression, while uptake in the spleen colocalized with CD3 expression. Evaluation of the effect of protein doses on the biodistribution and tumor targeting of 89Zr-MSLN HLE BiTE revealed for all dose groups that uptake in the spleen was faster than in the tumor (day 1 vs day 5). The lowest dose of 10 µg 89Zr-MSLN HLE BiTE had higher spleen uptake and faster blood clearance compared to higher doses of 50 µg and 200 µg. 89Zr-MSLN HLE BiTE tumor uptake was similar at all doses. Conclusion: The MSLN HLE BiTE showed specific tumor uptake and both arms contributed to the biodistribution profile. These findings support the potential for clinical translation of HLE BiTE molecules.

Pasotuxizumab, a BiTE® immune therapy for castration-resistant prostate cancer: Phase I, dose-escalation study findings

Aim: We report results of a first-in-human study of pasotuxizumab, a PSMA bispecific T-cell engager (BiTE®) immune therapy mediating T-cell killing of tumor cells in patients with advanced castration-resistant prostate cancer. Patients & methods: We assessed once-daily subcutaneous (SC) pasotuxizumab. All SC patients developed antidrug antibodies; therefore, continuous intravenous (cIV) infusion was assessed. Results: A total of 47 patients received pasotuxizumab (SC: n = 31, 0.5-172 μg/d; cIV: n = 16, 5-80 μg/d). The SC maximum tolerated dose was 172.0 μg/d. A sponsor change stopped the cIV cohort early; maximum tolerated dose was not determined. PSA responders occurred (>50% PSA decline: SC, n = 9; cIV, n = 3), including two long-term responders. Conclusion: Data support pasotuxizumab safety in advanced castration-resistant prostate cancer and represent evidence of BiTE monotherapy efficacy in solid tumors. Clinical trial registration: NCT01723475 (ClinicalTrials.gov).

Abstract 2769: PET imaging shows dose-dependent pharmacokinetics of a 89Zr-labeled mesothelin/CD3 half-life extended bispecific T-cell engager molecule in a syngeneic mouse model

BiTE® (bispecific T cell engager) immune therapy consists of two connected single-chain variable fragments, one targeting T-cells via CD3, and one targeting the tumor via a tumor-associated antigen. Given their short half-life, these molecules are administered by continuous intravenous (iv) infusion to ensure tumor accumulation. To extend plasma half-life, they are conjugated to an Fc domain, resulting in a molecule with an extended pharmacokinetic profile. To evaluate their biodistribution in a syngeneic mouse model, a molecule targeting murine mesothelin and murine CD3 (muMSLN HLE BiTE®), and a non-targeting control HLE BiTE® molecule were radiolabeled with the positron emission tomography (PET) isotope zirconium-89 (89Zr).

METHODS: The control and muMSLN HLE BiTE® were labeled with 89Zr. Immunocompetent BALB/c mice were engrafted in the lower mammary fat pad with mesothelin-positive murine mammary carcinoma cell line 4T1. PET imaging was performed at 1, 3, 5, 7 and 9 days after 50 µg 89Zr-muMSLN HLE BiTE® was administered by iv infusion (n = 8). Next, biodistribution of 10 µg (n = 6), 50 µg (n = 6) and 200 µg 89Zr-muMSLN HLE BiTE® (n = 5) and 50 µg 89Zr-control HLE BiTE® (n = 6) was compared via PET imaging on day 1, 3 and 5. PET-scans were quantified by mean standardized uptake value (SUVmean). Tracer injections were 4 MBq. To compare uptake in multiple groups, an analysis of variance followed by a post-hoc Tukey's multiple comparison test was performed. Values are expressed as mean ± standard deviation.

RESULTS: PET imaging following 50 µg 89Zr-muMSLN HLE BiTE® dosed iv revealed a blood elimination half-life of 63.4 hours. Uptake in tumor, spleen, thymus and liver were visible from 3 days post injection (pi). On day 5, tumor uptake was highest (SUVmean = 1.50 ± 0.2) with a tumor to blood ratio of 1.9 ± 0.3 and a spleen to blood of 1.7 ± 0.2. Heart SUVmean 5 days pi revealed that 10 μg 89Zr-muMSLN HLE cleared faster from the blood (0.5 ± 0.1) than the 50 μg (0.8 ± 0.1, P < 0.01) and the 200 μg dose group (0.8 ± 0.1, P < 0.01). Tumor SUVmean was higher in 50 µg (1.5 ± 0.2) than the 10 µg dose group (1.2 ± 0.1, P < 0.01), but similar to the 200 μg dose group (1.3 ± 0.1, P = 0.28). Spleen uptake 5 days pi was dose-dependent (SUVmean: 10 µg = 1.6 ± 0.2; 50 µg = 1.3 ± 0.1; 200 µg = 0.8 ± 0.1, P < 0.01). Spleen and tumor SUVmean 5 days pi of 50 µg 89Zr-muMSLN HLE BiTE® were higher than 50 µg 89Zr-control HLE BiTE® (spleen = 0.5 ± 0.1, P < 0.01; tumor = 0.8 ± 0.1, P < 0.01), while blood SUVmean of 50 µg 89Zr-control HLE BiTE® was similar (0.6 ± 0.1, P = 0.12).

CONCLUSION: PET imaging with a 89Zr-labeled muMSLN HLE BiTE® in a tumor-bearing syngeneic mouse model revealed a long blood half-life, specific uptake in tumor and spleen, and dose-dependent pharmacokinetics. Taken together, the HLE BiTE® molecule demonstrates an extended pharmacokinetic profile over previously evaluated small, canonical, BiTE® molecules.

Citation Format: Frans V. Suurs, Grit Lorenczewski, Julie M. Bailis, Sabine Stienen, Matthias Friedrich, Elisabeth G.E. de Vries, Derk Jan A. de Groot, Marjolijn N. Lub-de Hooge. PET imaging shows dose-dependent pharmacokinetics of a 89Zr-labeled mesothelin/CD3 half-life extended bispecific T-cell engager molecule in a syngeneic mouse model [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2769.

The Biodistribution of a CD3 and EpCAM Bispecific T-Cell Engager Is Driven by the CD3 Arm

Bispecific T-cell engager (BiTE) molecules are designed to engage and activate cytotoxic T cells to kill tumor cells. Little is known about their biodistribution in immunocompetent settings. Methods: To explore their pharmacokinetics and the role of the immune cells, BiTE molecules were radiolabeled with the PET isotope ⁸⁹Zr and studied in immunocompetent and immunodeficient mouse models. Results: PET images and ex vivo biodistribution in immunocompetent mice with [⁸⁹Zr]Zr-DFO-N-suc-muS110, targeting mouse CD3 (dissociation constant [K_D], 2.9 nM) and mouse epithelial cell adhesion molecule (EpCAM; K_D, 21 nM), and with [⁸⁹Zr]Zr-DFO-N-suc-hyS110, targeting only mouse CD3 (K_D, 2.9 nM), showed uptake in the tumor, spleen, and other lymphoid organs, whereas the human-specific control BiTE [⁸⁹Zr]Zr-DFO-N-suc-AMG 110 showed similar tumor uptake but lacked spleen uptake. [⁸⁹Zr]Zr-DFO-N-suc-muS110 spleen uptake was lower in immunodeficient than in immunocompetent mice. After repeated administration of nonradiolabeled muS110 to immunocompetent mice, ⁸⁹Zr-muS110 uptake in the spleen and other lymphoid tissues decreased and was comparable to uptake in immunodeficient mice, indicating saturation of CD3 binding sites. Autoradiography and immunohistochemistry demonstrated colocalization of [⁸⁹Zr]Zr-DFO-N-suc-muS110 and [⁸⁹Zr]Zr-DFO-N-suc-hyS110 with CD3-positive T cells in the tumor and spleen but not with EpCAM expression. Also, uptake in the duodenum correlated with a high incidence of T cells. Conclusion: [⁸⁹Zr]Zr-DFO-N-suc-muS110 biodistribution is dependent mainly on the T-cell-targeting arm, with a limited contribution from its second arm, targeting EpCAM. These findings highlight the need for extensive biodistribution studies of novel bispecific constructs, as the results might have implications for their respective drug development and clinical translation.

Phase I study of pasotuxizumab (AMG 212/BAY 2010112), a PSMA-targeting BiTE (Bispecific T-cell Engager) immune therapy for metastatic castration-resistant prostate cancer (mCRPC)

124

Background: mCRPC has a poor prognosis and immunotherapies are largely ineffective. PSMA is a promising therapeutic target in mCRPC. Pasotuxizumab is a PSMA x CD3 BiTE immune therapy that mediates killing of tumor cells by T cells. Methods: NCT01723475 was a first-in-human, multicenter, dose-escalation study in patients (pts) with mCRPC refractory to standard therapy. Pts received continuous IV infusion of pasotuxizumab in cohorts of 3–4 pts. Dose-escalation followed a continuous reassessment methodology. The primary objective was to determine safety and maximum tolerated dose (MTD); secondary objectives included pharmacokinetics, biomarkers, and tumor response. Results: 16 pts were enrolled into 5 dosing cohorts (5 µg/d, n=3; 10 µg/d, n=4; 20 µg/d, n=3; 40 µg/d, n=4; 80 µg/d, n=2). All pts had ≥1 AE of any grade; most common were fever (94%), chills (69%), and fatigue (50%). 13 pts (81%) had ≥1 AE of grade ≥3; most common were decreased lymphocytes and infections (both 44%). No grade 5 AE occurred. A serious drug-related AE was reported for 1 pt (fatigue, 20 µg/d). No antidrug antibodies were observed. Recruitment was stopped before MTD was reached to allow initiation of a new study sponsored by Amgen. Antitumor activity as indicated by PSA serum level decline was dose dependent, with a mean best PSA change per dosing cohort vs baseline of +0.74% (5 µg/d), −17.9% (10 µg/d), −37.4% (20 µg/d), −42.5% (40 µg/d) and −54.9% (80 µg/d). PSA decreases ≥50% occurred in 3 pts (n=1 each in 20 µg/d, 40 µg/d, 80 µg/d cohorts). One long-term PSA responder was treated for 14 months (40 µg/d) and one for 19.4 months (80 µg/d). The latter pt showed a complete regression of soft-tissue metastases and marked regression of bone metastases by PSMA-PET/CT, >90% reduction in PSA and alkaline phosphatase, and a significant and durable improvement in disease related symptoms. Conclusions: Pasotuxizumab had an acceptable safety profile and dose-dependent clinical activity in mCRPC pts. There were two long term responders in the dose escalation. This is the first clinical study showing that a BiTE immune therapy can be efficacious in solid tumors. Clinical trial information: NCT01723475.

Abstract 1134: PET-imaging of 89Zr-labeled bispecific T-cell engagers in syngeneic tumor bearing mice

BACKGROUND Bispecific T-cell engagers (BiTE®) harness the immune system against cancer. BiTE® antibody constructs are small proteins of ~53 kDa existing of two connected single-chain variable fragments. MuS110, a BiTE® with affinity for murine CD3 (KD= 2.9 nM) and murine EpCAM (KD= 21 nM), was radiolabeled with positron emission tomography (PET) isotope zirconium-89 (89Zr) to study its pharmacokinetics and involvement of the immune system in an immunocompetent mouse model bearing a syngeneic tumor.

METHODS MuS110 and two control BiTE® antibody constructs (hyS110 and AMG110) were radiolabeled with 89Zr. HyS110 has affinity for murine CD3 and human EpCAM, AMG110 for human CD3 and human EpCAM. The human and murine variants of EpCAM and CD3 are not cross-reactive. Either immunocompetent BALB/c or immunodeficient nude BALB/c mice were all orthotopically engrafted in the lower mammary fat pad with EpCAM-positive murine breast cancer cell line 4T1. PET-imaging was performed at 0.5, 3, 6, 24, 48 and 72 h after intravenous (iv) administration of 10 µg 89Zr-muS110. Distribution of 10 µg 89Zr-muS110, 89Zr-hyS110 and 89Zr-AMG110 was assessed 24 h after administration in BALB/c and nude BALB/c mice with PET-imaging and ex-vivo biodistribution. In addition, a group of BALB/c mice received 10 µg muS110 iv daily for 5 days followed by 10 µg 89Zr-muS110 or 10 µg 89Zr-AMG110 and PET-imaging 24 h after tracer administration. Values are expressed as median (interquartile range).

RESULTS PET-imaging revealed fast renal clearance of 89Zr-muS110 in the BALB/c mice resulting in a blood half-life of 0.93 h (one-phase decay). Tumor- and spleen-to-blood ratios increased to 3.7 (3.0 to 4.5) and 9.3 (7.5 to 11.1) after 72 h. Ex-vivo biodistribution 24 h after tracer administration showed 89Zr-muS110 and 89Zr-hyS110 accumulation in the spleen with 8.2 % injected dose per gram (ID/g) and 8.7 %ID/g, in comparison to 89Zr-AMG110 (2.3 %ID/g; vs 89Zr-muS110 P<0.05, vs 89Zr-hyS110 P<0.05). In mesenteric lymph nodes (mesLNs), 89Zr-muS110 and 89Zr-hyS110 resulted in a higher uptake (3.5 and 6.4 %ID/g) than 89Zr-AMG110 (2.0 %ID/g; vs 89Zr-muS110 P<0.05, vs 89Zr-hyS110 P<0.05). Tumor uptake did not differ for 89Zr-muS110 and 89Zr-AMG110 (2.6 vs 2.2 %ID/g, P>0.05). In nude BALB/c mice spleen and mesLN uptake of 89Zr-muS110 was lower than in BALB/c mice (spleen: 3.4 vs 8.2 %ID/g, P<0.05; mesLNs: 1.7 vs 3.5, P<0.05). In addition, in nude BALB/c mice, tumor uptake was the same for 89Zr-muS110 and 89Zr-AMG110 (1.5 vs 1.7 %ID/g, P>0.05). 89Zr-muS110 uptake was lower in spleen and mesLNs following 5 days of 10 µg muS110 iv compared to control mice

(spleen: 4.2 vs 8.2 %ID/g, P<0.01; mesLNs: 1.9 vs 3.5, P<0.01), likely representing target saturation.

CONCLUSION Distribution of BiTE® 89Zr-muS110 is predominantly mediated by the affinity for CD3, resulting in uptake in lymphoid tissues.

Citation Format: Frans V. Suurs, Derk J. de Groot, Urszula M. Domanska, Grit Lorenczewski, Sabine Stienen, Matthias Friedrich, Elisabeth G. de Vries, Marjolijn N. Lub-de Hooge. PET-imaging of 89Zr-labeled bispecific T-cell engagers in syngeneic tumor bearing mice [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1134.

Abstract 1561: Evaluation of mesothelin BiTE® antibody constructs in models of pancreatic ductal adenocarcinoma

Bispecific T cell engager (BiTE®) antibody constructs are designed to redirect T cells to induce lysis of tumor cells through simultaneous binding to CD3 on T cells and to a tumor associated antigen. BiTE® antibody constructs have previously been shown to be effective at depleting blood and tissue targets in B cell malignancies, suggesting a therapeutic potential for BiTE® antibody constructs in solid tumors. Pancreatic ductal adenocarcinoma (PDA) is a devastating malignant disease with a dismal prognosis even with currently available therapies. The tumor differentiation antigen mesothelin (MSLN) is highly expressed in over 80% of pancreatic tumors. Expression of MSLN is restricted in normal tissue implicating MSLN as an attractive target for BiTE® targeted therapy in PDA. In this study, we report the preclinical characterization of an anti-MSLN/CD3 BiTE® antibody construct with half-life extension (MSLN HLE BiTE®) in xenograft models of PDA. Previously the MSLN HLE BiTE® was found to bind CD3 and MSLN with low nanomolar affinity and have low picomolar cytotoxic activity against MSLN-positive cells in vitro. Moreover, the MSLN HLE BiTE® can mediate redirected lysis of cancer cell lines resistant to chemotherapy. Our study examines the efficacy of the highly potent and specific MSLN HLE BiTE® antibody construct in vivo by utilizing the orthotopic implantation of human AsPC-1 luciferase expressing PDA cells in immunocompromised NOD-Prkdcscid IL2rgnull (NSG) mice. We found that mice receiving the MSLN HLE BiTE® antibody construct survived significantly longer and had significantly reduced tumor burden comparing to control mice. Moreover, tumor bearing mice were given fluorescently labeled human T cells to measure T cell localization. Using live animal fluorescent imaging, we found mice treated with the MLSN HLE BiTE® antibody construct had significantly increased T cell localization and retention to the PDA tumor area compared to control. Mice receiving orthotopic implantation of MSLN knock out human AsPC-1 tumors treated with the MSLN HLE BiTE® did not show increased survival, reduction of tumor burden or increased T cell localization, confirming the BiTE® specificity for the tumor target MSLN. Furthermore, using the KPC mouse model of PDA, which develops cancer spontaneously upon conditional pancreatic expression of KRASG12D and TP53R172H mutations, we tested if a mouse-specific surrogate MSLN HLE BiTE® antibody construct could localize to a naturally formed dense tumor microenvironment. We found that mice treated with a murine MSLN HLE BiTE® labeled with CW800 demonstrated strong localization of the MSLN HLE BiTE® through the dense microenvironment to the PDA tumor. Taken together, these results suggest that a MSLN HLE BiTE® may be a unique targeted immunotherapy for PDA patients.

Citation Format: Noelle R. Jurcak, MacKenzie Zarecki, Fei Lee, Noah Rozich, Stephen Muth, Elizabeth Jaffee, Sabine Stienen, Julie Bailis, Lei Zheng. Evaluation of mesothelin BiTE® antibody constructs in models of pancreatic ductal adenocarcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1561.

Novel anti-EGFRvIII bispecific T cell engager (BiTE) antibody construct in glioblastoma (GBM): Trial in progress of AMG 596 in patients with recurrent or newly diagnosed disease

TPS2071

Background: GBM is the most aggressive primary brain tumor in adults and is extremely difficult to treat. Patients with GBM tend to progress rapidly within weeks or months. Median overall survival is only 12–15 months despite aggressive treatment, and less than 5% of patients survive 5 years. GBM also severely impacts quality of life and cognitive function. Approximately 50% of GBM tumors test positive for amplification or mutation of the epidermal growth factor receptor (EGFR), the most common of which is the EGFRvIII gain-of-function mutation. AMG 596 is a bispecific T cell engager (BiTE®) antibody construct designed to crosslink and engage CD3-positive T cells to EGFRvIII-positive tumor cells, inducing tumor cell lysis and T cell proliferation. A clinical trial is being conducted for this novel immunotherapy agent in patients with EGFRvIII-positive GBM. Methods: NCT03296696 is a phase 1, first-in-human, open-label, sequential dose-escalation and dose-expansion study evaluating the safety, tolerability, and pharmacokinetics and pharmacodynamics (PK/PD) of AMG 596 in patients with EGFRvIII-positive GBM. AMG 596 is administered via continuous intravenous infusion. The study is expected to enroll approximately 82 patients total and comprises two groups (Group 1: patients with recurrent GBM; Group 2: patients with newly diagnosed GBM in the maintenance treatment phase after standard of care). Key inclusion criteria include: male or female; ≥ 18 years of age; with pathologically documented and diagnosed grade IV GBM; Eastern Cooperative Oncology Group performance status ≤ 1; life expectancy ≥ 3 months per study investigator; and acceptable renal, hematological, and hepatic function. The primary endpoint evaluates the safety and tolerability of AMG 596 via collection of treatment-emergent adverse events. Additional endpoints include objective response rate per modified Response Assessment in Neuro-Oncology Criteria and PK/PD analyses of AMG 596 in serum. The study began enrolling patients in April 2018 and enrollment is ongoing. For more information, please contact Amgen Medical Information: medinfo@amgen.com. Clinical trial information: NCT03296696.

Phase 1 study of pasotuxizumab (BAY 2010112), a PSMA-targeting Bispecific T cell Engager (BiTE) immunotherapy for metastatic castration-resistant prostate cancer (mCRPC)

5034

Background: mCRPC has a poor prognosis and immunotherapies are largely ineffective. PSMA is a promising therapeutic target in mCRPC, and pasotuxizumab is a PSMA x CD3 BiTE that mediates tumor cell killing. Methods: NCT01723475 was a first-in-human, multicenter, dose-escalation study in patients (pts) with mCRPC refractory to standard therapy. Pts received pasotuxizumab as a continuous intravenous infusion in cohorts of 3–4 pts. Dose-escalation followed a continuous reassessment methodology design. The primary objective was to determine safety and maximum tolerated dose (MTD); secondary objectives included pharmacokinetics, biomarkers, and tumor response. Results: 16 pts were enrolled into 5 dosing cohorts (5 µg/d, n = 3; 10 µg/d, n = 4; 20 µg/d, n = 3; 40 µg/d, n = 4; 80 µg/d, n = 2). All pts had ≥1 AE of any grade; most common were fever (94%), chills (69%), and fatigue (50%). 13 pts (81%) had ≥1 AE of grade ≥3; most common were decreased lymphocytes and infections (both 44%). No grade 5 AE occurred. A serious AE related to study drug was reported for 1 pt (fatigue, 20 µg/d). No anti-drug antibodies were observed. Recruitment was stopped before MTD was reached to facilitate initiation of a new study sponsored by Amgen. Antitumor activity as indicated by PSA serum level decline was dose dependent, with a mean best PSA change per dosing cohort versus baseline of +0.74% (5 µg/d), –17.9% (10 µg/d), –37.4% (20 µg/d), –42.5% (40 µg/d) and –54.9% (80 µg/d). PSA decreases of ≥50% occurred in 3 pts (n = 1 each in 20 µg/d, 40 µg/d, and 80 µg/d cohorts). One long-term PSA responder was treated for 14 months (40 µg/d) and one for 19.4 months (80 µg/d). The latter pt showed a complete regression of soft-tissue metastases and marked regression of bone metastases as assessed by PSMA-PET/CT, > 90% reduction in PSA and alkaline phosphatase, and a significant and durable improvement in disease related symptoms. Conclusions: Pasotuxizumab had an acceptable safety profile and dose-dependent clinical activity in mCRPC pts. There were two long term responders in the dose escalation. This is the first clinical study showing that a BiTE immunotherapy can be efficacious in solid tumors. Clinical trial information: NCT01723475.

Molecular Imaging of Radiolabeled Bispecific T-Cell Engager 89Zr-AMG211 Targeting CEA-Positive Tumors

Purpose: AMG 211, a bispecific T-cell engager (BiTE) antibody construct, targets carcinoembryonic antigen (CEA) and the CD3 epsilon subunit of the human T-cell receptor. AMG 211 was labeled with zirconium-89 (⁸⁹Zr) or fluorescent dye to evaluate the tumor-targeting properties.Experimental Design: ⁸⁹Zr-AMG211 was administered to mice bearing CEA-positive xenograft tumors of LS174T colorectal adenocarcinoma or BT474 breast cancer cells, as well as CEA-negative HL-60 promyelocytic leukemia xenografts. Biodistribution studies with 2- to 10-μg ⁸⁹Zr-AMG211 supplemented with unlabeled AMG 211 up to 500-μg protein dose were performed. A BiTE that does not bind CEA, ⁸⁹Zr-Mec14, served as a negative control. ⁸⁹Zr-AMG211 integrity was determined in tumor lysates ex vivo Intratumoral distribution was studied with IRDye800CW-AMG211. Moreover, ⁸⁹Zr-AMG211 was manufactured according to Good Manufacturing Practice (GMP) guidelines for clinical trial NCT02760199Results: ⁸⁹Zr-AMG211 demonstrated dose-dependent tumor uptake at 6 hours. The highest tumor uptake was observed with a 2-μg dose, and the lowest tumor uptake was observed with a 500-μg dose. After 24 hours, higher uptake of 10-μg ⁸⁹Zr-AMG211 occurred in CEA-positive xenografts, compared with CEA-negative xenografts. Although the blood half-life of ⁸⁹Zr-AMG211 was approximately 1 hour, tumor retention persisted for at least 24 hours. ⁸⁹Zr-Mec14 showed no tumor accumulation beyond background level. Ex vivo autoradiography revealed time-dependent disintegration of ⁸⁹Zr-AMG211. 800CW-AMG211 was specifically localized in CEA-expressing viable tumor tissue. GMP-manufactured ⁸⁹Zr-AMG211 fulfilled release specifications.Conclusions: ⁸⁹Zr-AMG211 showed dose-dependent CEA-specific tumor targeting and localization in viable tumor tissue. Our data enabled its use to clinically evaluate AMG 211 in vivo behavior. Clin Cancer Res; 24(20); 4988-96. ©2018 AACR.

A multicenter phase 1 study of solitomab (MT110, AMG 110), a bispecific EpCAM/CD3 T-cell engager (BiTE®) antibody construct, in patients with refractory solid tumors

We assessed the tolerability and antitumor activity of solitomab, a bispecific T-cell engager (BiTE®) antibody construct targeting epithelial cell adhesion molecule (EpCAM). Patients with relapsed/refractory solid tumors not amenable to standard therapy received solitomab as continuous IV infusion in a phase 1 dose-escalation study with six different dosing schedules. The primary endpoint was frequency and severity of adverse events (AEs). Secondary endpoints included pharmacokinetics, pharmacodynamics, immunogenicity, and antitumor activity. Sixty-five patients received solitomab at doses between 1 and 96 µg/day for ≥28 days. Fifteen patients had dose-limiting toxicities (DLTs): eight had transient abnormal liver parameters shortly after infusion start or dose escalation (grade 3, n = 4; grade 4, n = 4), and one had supraventricular tachycardia (grade 3); all events resolved with solitomab discontinuation. Six patients had a DLT of diarrhea: four events resolved (grade 3, n = 3; grade 4, n = 1), one (grade 3) was ongoing at the time of treatment-unrelated death, and one (grade 3) progressed to grade 5 after solitomab discontinuation. The maximum tolerated dose was 24 µg/day. Overall, 95% of patients had grade ≥3 treatment-related AEs, primarily diarrhea, elevated liver parameters, and elevated lipase. Solitomab half-life was 4.5 hours; serum levels plateaued within 24 hours. One unconfirmed partial response was observed. In this study of a BiTE® antibody construct targeting solid tumors, treatment of relapsed/refractory EpCAM-positive solid tumors with solitomab was associated with DLTs, including severe diarrhea and increased liver enzymes, which precluded dose escalation to potentially therapeutic levels.

Abstract 3630: Preclinical evaluation of a BiTE® antibody construct with extended half-life that targets the tumor differentiation marker mesothelin

Bispecific T cell engager (BiTE®) antibody constructs redirect T cells to induce lysis of tumor cells. The anti-CD19/CD3 BiTE® Blincyto® can deplete target cells in both the blood and tissue compartment in B cell malignancies, suggesting that the BiTE® mechanism of action will also be effective against solid tumors. The tumor differentiation antigen mesothelin (MSLN) is an attractive target for the BiTE® approach. MSLN is highly expressed in >80% of ovarian and pancreatic tumors and mesothelioma. Expression of MSLN in normal tissues appears restricted to mesothelial cell surfaces such as the pleural, pericardial, and peritoneal layer.

Here, we report the preclinical characterization of an anti-MSLN/CD3 BiTE® antibody construct with extended half-life. The BiTE® antibody construct binds MSLN and CD3 with low nM affinity and has low pM cytotoxic activity against MSLN-positive ovarian, pancreatic and lung cancer cell lines in vitro. Activity of the anti-MSLN/CD3 BiTE® antibody construct is observed at low effector to target cell ratios, and in cancer cells that express low levels of MSLN. This BiTE® antibody construct is also cytotoxic to cell lines that are resistant to chemotherapy. In mice, significant tumor growth inhibition of an established ovarian tumor xenograft model was achieved by IV dosing of the anti-MSLN/CD3 BiTE® antibody construct every 5 days. Pharmacokinetic evaluation of the anti-MSLN/CD3 BiTE® antibody construct in non-human primates demonstrated a half-life of 4-10 days. The potency and specificity of the anti-MSLN/CD3 BiTE® antibody construct, together with projected ability to dose once a week IV in humans, supports development of this BiTE® for treatment of MSLN-positive tumors.

Citation Format: Alexander Sternjak, Fei Lee, Joachim Wahl, Dan Rock, Oliver Thomas, Sabine Stienen, Ralf Lutterbuese, Patrick Hoffmann, Tobias Raum, Peter Kufer, Benno Rattel, Angela Coxon, Matthias Friedrich, Julie Bailis. Preclinical evaluation of a BiTE® antibody construct with extended half-life that targets the tumor differentiation marker mesothelin [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3630. doi:10.1158/1538-7445.AM2017-3630

Harnessing T cells to fight cancer with BiTE® antibody constructs--past developments and future directions

Bispecific T-cell engager (BiTE(®)) antibody constructs represent a novel immunotherapy that bridges cytotoxic T cells to tumor cells, thereby inducing target cell-dependent polyclonal T-cell activation and proliferation, and leading to apoptosis of bound tumor cells. Anti-CD19 BiTE(®) blinatumomab has demonstrated clinical activity in Philadelphia chromosome (Ph)-negative relapsed or refractory (r/r) acute lymphoblastic leukemia (ALL) eventually resulting in conditional approval by the U.S. Food and Drug Administration in 2014. This drug is currently further developed in pediatric and Ph(+) r/r, as well as in minimal residual disease-positive ALL, and might also offer clinical benefit for patients with non-Hodgkin's lymphoma, especially for those with aggressive forms like diffuse large B-cell lymphoma. Another BiTE(®) antibody construct in hemato-oncology designated AMG 330 targets CD33 on acute myeloid leukemia blast cells. After showing promising ex vivo activity, this drug candidate has recently entered phase 1 clinical development, and has further indicated potential for combination with checkpoint inhibitors. In solid tumor indications, three BiTE(®) antibody constructs have been tested in phase 1 studies so far: anti-EpCAM BiTE(®) AMG 110, anti-CEA BiTE(®) MEDI-565/AMG 211, and anti-PSMA BiTE(®) BAY2010112/AMG 212. Pertinent questions comprise how to maximize BiTE(®) penetration and T-cell infiltration of the tumor while simultaneously minimizing any adverse events, which is currently explored by a continuous intravenous infusion approach. Thus, BiTE(®) antibody constructs will hopefully provide new treatment options for patients in several indications with high unmet medical need.

Visualization of spin dynamics in single nanosized magnetic elements

The design of future spintronic devices requires a quantitative understanding of the microscopic linear and nonlinear spin relaxation processes governing the magnetization reversal in nanometer-scale ferromagnetic systems. Ferromagnetic resonance is the method of choice for a quantitative analysis of relaxation rates, magnetic anisotropy and susceptibility in a single experiment. The approach offers the possibility of coherent control and manipulation of nanoscaled structures by microwave irradiation. Here, we analyze the different excitation modes in a single nanometer-sized ferromagnetic stripe. Measurements are performed using a microresonator set-up which offers a sensitivity to quantitatively analyze the dynamic and static magnetic properties of single nanomagnets with volumes of (100 nm)(3). Uniform as well as non-uniform volume modes of the spin wave excitation spectrum are identified and found to be in excellent agreement with the results of micromagnetic simulations which allow the visualization of the spatial distribution of these modes in the nanostructures.

Magnetism of single-crystalline Fe nanostructures

The quantitative investigation of magnetic nanostructures by means of ferromagnetic resonance is demonstrated for single-crystalline iron nanostructures. It is shown that the single-crystalline nature leads to effects not being present in polycrystalline ones and helps to quantitatively interpret the results. First a method is presented that enables one to fabricate epitaxial Fe nanowires starting from a thin film of Fe grown under ultrahigh vacuum conditions on GaAs (110). The system allows, due to the combination of cubic and twofold magnetic anisotropy, to prepare wires whose easy axis in remanence is oriented perpendicular to the wires axis. This unique feature is only achievable in epitaxial systems. Furthermore, nearly perfect Fe nanocubes with 13.6 nm edge length prepared by wet-chemical methods are studied. While the shell of the particles is composed of either Fe3O4 or gamma-Fe2O3, the core consists of metallic Fe. Oxygen and hydrogen plasma are used to remove the ligand system and the oxide shell. The single-crystalline nature of the cubes enables one to quantitatively determine the magnetic properties of the individual particle by means of ferromagnetic resonance measurements on an ensemble together with a model based on the Landau-Lifshitz equation. The measurements reveal a magneto-crystalline anisotropy of K4 = 4.8. 10(4) J/m3 being equal to bulk value and a saturation magnetization which is reduced to M(5K) = (1.2 +/- 0.12). 10(6) A/m (70% of bulk value). The effective damping parameter alpha = 0.03 is increased by one order of magnitude with respect to bulk Fe, showing that magnetic damping in nanostructures differs from the bulk.