HER2 Extracellular Domain Research Articles

Optimizing hybrid LC-MS/MS binding conditions is critical: impact of biotransformation on quantification of trastuzumab.

Background: Hybrid ligand-binding (LB) LC-MS/MS protein quantitative assays involve a LB step for analyte enrichment that has less stringent requirements than the conventional LB assays. Results: Herceptin™(trastuzumab) binding to HER2 extracellular domain was evaluated using on-bead and off-bead capture formats. The two formats yielded significantly different trastuzumab concentrations in human and monkey serum pharmacokinetic samples. Biotransformations, including deamidation of asparagine and isomerization of aspartic acid near the complementarity-determining regions of trastuzumab, had a profound impact on the LB step for analyte enrichment and trastuzumab quantification. Conclusion: Quantitative measurements were profoundly impacted by LB conditions in a hybrid LB LC-MS/MS protein assay due to biotransformations. Therefore, similar to conventional LB assays, binding conditions should be carefully evaluated during assay development.

Association between HER2 germline mutation A270S and prognosis in patients with primary breast cancer

To investigate the association between the HER2 germline mutation Ala270Ser (A270S), located in HER2 extracellular domain, and survival in breast cancer patients. HER2 germline mutation A270S was identified in 5395 consecutive patients with operable primary breast cancer using direct Sanger sequencing analysis. Survival curves for patients with HER2 A270S mutation were compared using the Kaplan-Meier method with log-rank test. We identified that 31 cases carried HER2 germline mutation A270S in 5395 patients (0.6%, 31/5395). The HER2 A270S mutation was significantly associated with recurrence-free survival (RFS) and distant recurrence-free survival (DRFS) in the entire cohort of 5395 patients (RFS, unadjusted hazard ratio [HR] = 2.23; 95% confidence interval [CI] = 1.00-5.00; P= 0.045; DRFS, unadjusted HR = 2.80; 95% CI = 1.25-6.28; P= 0.009). Among the HER2-negative patients (n= 3825), those with the HER2 A270S mutation had a significantly worse RFS (unadjusted HR = 3.19; 95% CI = 1.42-7.16; P= 0.003) and DRFS (unadjusted HR = 3.98; 95% CI = 1.77-8.96; P< 0.001) than did those with wild type. Moreover, the A270S mutation remained an independent unfavorable factor for RFS and DRFS in the HER2-negative patients (RFS, HR = 3.30; 95% CI = 1.34-8.10; P= 0.009; DRFS, HR = 4.26; 95% CI = 1.73-10.47; P= 0.002). Breast cancer patients with the HER2 germline mutation A270S had a worse survival, especially in HER2-negative patients. Therefore, HER2-negative patients with a HER2 germline mutation A270S might be potential candidates for HER2-targeted therapy.

Portable detection of serum HER-2 in breast cancer by a pressure-based platform.

A high serum HER-2 extracellular domain (sHER-2 ECD) level has a reverse association with tumor behaviors. In this study, a portable platform for the disease biomarker sHER-2 ECD detection has been established using a pressure-based bioassay. The pressure bioassay consists of a monoclonal antibody immobilized on an eight-well strip, the analyte HER-2, and another monoclonal antibody labeled with the Pt nanoparticles (PtNPs), which have the catalytic ability to decompose H2O2 into H2O and O2(g). The increased pressure due to O2(g) generation is measured by a hand-held pressure meter. A total of 34 serum samples were collected to validate the performance of the pressure bioassay. The results showed that the pressure bioassay platform of HER-2 had a dynamic range from 2 to 50ng/mL with a limit of detection (LOD) of 2ng/mL, which was consistent with the ELISA result. In the real serum samples, there was a significant correlation between sHER-2 ECD level and several clinicopathological parameters, especially tissue HER-2 status. Furthermore, the sHER-2 ECD level was found to decrease after targeted therapy in a patient with tHER-2 positive. Overall, this bioassay can facilitate breast cancer diagnosis and prognosis in clinical scenarios and resource-limited areas.

Development of a novel anti-HER2 scFv by ribosome display and in silico evaluation of its 3D structure and interaction with HER2, alone and after fusion to LAMP2B.

HER2 is a member of epidermal factor receptor (EGFR) family which is overexpressed in breast cancer, ovarian cancer and gastric cancer. Development of new binders for cancer cell surface receptors and expressing them at the surface of exosomes would be a great approach in targeted cancer therapy. We found a high affinity scFv against HER2 using ribosome display with the approach of applying it as a targeting moiety at the surface of exosomes by fusion to lysosomal associated membrane protein 2B (LAMP2B). We also provide some structural information about the ribosome display selected scFv (scFv HFS2) through modeling the 3D structure of scFv HFS2 using RosettaAntibody and docked it at the extracellular domain of HER2. We also evaluated the structure of scFv HFS2 and its binding to HER2 after fusion to LAMP2B. Our results showed no significant change in 3D structure of scFv HFS2 when fused to LAMP2B (RMSD 1.3) and interaction analysis represented that scFv HFS2 binds HER2 domain III before and after fusion to LAMP2B. Although binding domain of scFv HFS2 on HER2 was the same at both state, residues involved in their interactions showed significant differences as it was probably due to the spatial hindrance of scFv HFS2 when fused to LAMP2B through a short linker and it should be considered before proceeding to experiment.

Abstract 362: EGFR signaling activates S100 gene expression in HER2-positive breast cancer cells

Abstract Introduction: Human Epidermal Growth Factor Receptor-2-positive (HER2+) breast cancer is one of the four major molecular types of breast cancer. HER2 is a classical receptor tyrosine kinase (RTK) and its kinase activity is stimulated by heterodimerization with other ligand bound HER family members, such as EGFR/HER1. Treatment for HER2+ breast cancer includes the use of Trastuzumab, a monoclonal antibody that binds to the HER2 extracellular domain and inhibits downstream signaling. Resistance to Trastuzumab involves several cellular and molecular alterations, including gain of function mutations in proteins that are downstream of HER2 activation. The purpose of this study is to examine EGFR signaling in HER2+ breast cancer cells to discover novel putative drug targets. Methods: HER2-positive breast cancer cell line (SKBR3) was used before and after EGF treatment. In order to determine whether EGFR signaling was activated, the levels of several proteins of interest were determined by western blot analysis. RNA-seq and ChIP-seq for H3K18ac and H3K27ac was conducted following an EGF time course in SKBR3 cells. Results: Treatment of SKBR3 cells with EGF resulted in a transient increase in pERK1/2 and pAKT, which returned to basal levels at 1h and 2h post-EGF treatment, respectively. This was surprising because pEGFR remained higher in treated cells compared to untreated cells throughout the 24h time course. Immediate early genes (IEGs) became activated in SKBR3 cells, as previously reported in other cell types, during the early phase of EGFR stimulation (&amp;lt;4h). Using mRNA-seq we determined expression patterns during a 24h period and found that SKBR3 cells treated with EGF resulted in the activation and repression by 2-fold or more of over 4000 transcripts. We examined the chromatin landscape following EGFR stimulation with chromatin immunoprecipitation for H3K18ac and H3K27ac followed by next generation sequencing (ChIP-seq). We determined that, regardless of transcript levels, H3K18ac and H3K27ac oscillated at all regulated genes and globally. A closer look at the genes that peaked in expression at 24h post-EGF treatment revealed that S100 genes steadily increased in expression. Moreover, the chromatin surrounding the locus that contains the majority of S100 genes increased in H3K18ac and H3K27ac 1h post-EGF treatment, suggesting that S100 genes are a direct target of EGFR/HER2 signaling. Summary: We hypothesize that S100 proteins, which act as Ca2+ sensors, could play a role in EGF induced tumor cell growth and metastasis, contribute to Herceptin resistance and are likely drug targets in HER2+ breast cancer. Citation Format: Miguel Nava, Nathan R. Zemke, Arnie Berk, Robin Farias-Eisner, Jay Vadgama, Yanyuan Wu. EGFR signaling activates S100 gene expression in HER2-positive breast cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 362.

Revealing the molecular interactions of aptamers that specifically bind to the extracellular domain of HER2 cancer biomarker protein: An in silico assessment

Single-stranded (ss) oligonucleotide aptamers are emerging as the promising substitutes for monoclonal antibodies because of their low production cost and good batch-to-batch consistency. Aptamers vividly bind to a variety of cellular targets and alter their functions with a remarkable degree of specificities. In this study, the positive clones of human epidermal growth factor receptor 2 (HER2) specific binding ssDNA aptamers which were previously identified by in vitro Systematic Evolution of Ligands by EXponential enrichment (SELEX) process, hitherto lacking the putative binding site information and residues crucial for aptamer recognition are studied. Primarily, four putative DNA binding regions present on the HER2 extracellular domain (ECD) were identified using prediction servers and electrostatic potential maps, which were further exploited to delineate the aptamer binding features. Molecular docking and molecular dynamics (MD) simulations revealed stable binding nature of three aptamers (H2>H1>H6), which chose Site 2a as preferred binding site present on the HER2(ECD) protein. Furthermore, amino acid residues viz. Asn37, Gln59, Arg81-Gln84, Asp88, and Lys128 of Site 2a were found to be crucial for high-affinity binding. This knowledge can be utilized as a benchmark for the future studies, in search for better and highly specific anti-HER2 aptamers as cancer therapeutics or as diagnostic agents.

Aptamer based fluorescent probe for serum HER2-ECD detection: The clinical utility in breast cancer

The transmembrane protein HER2 is overexpressed in approximately 30% of breast cancer patients. HER2-positive breast cancers tend to spread more aggressively, which result in increased mortality in women. Nowadays, the real-time monitoring of HER2 status is important in clinical diagnosis and treatment for HER2-positive patients. Although IHC and FISH assay are standard methods to evaluate the tissue HER2 status, both approaches which required high quality tissue samples and are not suitable for monitoring the status of HER2 in real time. Since extracellular domain (ECD) of the HER2 receptor can be shed into the circulation, the serum test of HER2 ECD has been developed as an additional approach to probe HER2 overexpression. The serum test will be able to monitor the dynamic changes of HER2 status. In this paper, we detected serum HER2 ECD using Cy5-labeled HB5 aptamer as a result of its specific binding ability to HER2 ECD. This aptamer-based fluorescent probe is easily synthesized and modified and as sensitive as anti-HER2 antibodies. We believe that Cy5-HB5 may have application potentials in serum HER2 test for clinical utility of breast cancer, such as recurrence and metastases.

Immunization with HER2 extracellular subdomain proteins induces cellular response and tumor growth inhibition in mice.

We investigated cellular and protective immune responses in mice vaccinated with recombinant HER2 extracellular subdomains. Balb/C mice were immunized with recombinant full HER2 extracellular domain and subdomain proteins. Humoral and cellular immune response and antitumor effect was evaluated using a syngeneic mice tumor model. All recombinant proteins induced secretion of IL-4 and particularly IFN-γ and IL-17 cytokines. Challenging of immunized mice with stable 4T1-HER2 transfected cells resulted in partial but significant tumor growth inhibition in all groups of mice particularly those immunized with fHER2-ECD together with CPG. Our results suggest that the recombinant HER2-ECD subdomains induce mainly Th1 and Th17 responses, which seem to contribute to tumor growth inhibition in syngeneic mice.

Site-Specific Photoconjugation of Beta-Lactamase Fragments to Monoclonal Antibodies Enables Sensitive Analyte Detection via Split-Enzyme Complementation.

Protein fragment complementation assays (PCA) rely on a proximity-driven reconstitution of a split reporter protein activity, typically via interaction between bait and prey units separately fused to the reporter protein halves. The PCA principle can also be formatted for use in immunossays for analyte detection, e.g., via the use of small immunoglobulin binding proteins (IgBp) as fusion partners to split-reporter protein fragments for conversion of pairs of antibodies into split-protein half-probes. However, the non-covalent binding between IgBp and antibodies is not ideal for development of robust assays. Here, the authors describe how split-enzyme reporter halves can be both site-specifically and covalently photoconjugated at antibody Fc-parts for use in homogeneous dual-antibody in vitro immunoassays based on analyte-dependent split-enzyme fragment complementation. The half-probes consist of parts of a beta-lactamase split-protein reporter fused to an immunoglobulin Fc binding domain equipped with a unique cysteine residue at which a photoactivable maleimide benzophenone group (MBP) is attached. Using such antibody conjugates the authors obtain an analyte-driven complementation of the reporter enzyme fragments monitored via conversion of a chromogenic substrate. Results from detection of human interferon-gamma and the extracellular domain of HER2 is shown. The described principles for site-specific conjugation of proteins to antibodies should be broadly applicable.

Abstract P2-09-07: Low levels of HER2 extracellular domain (ECD) compared to intracelluar domain (ICD) in NeoALTTO may segregate benefit from lapatinib and trastuzumab in breast cancer

Abstract Background: Preclinical models suggest that in some HER2 overexpressed breast cancer cases, the extracellular domain of HER2, containing the binding region for trastuzumab (T) is not present due to proteolytic cleavage. Previous measurement of HER2 ECD and ICD in HeCOG 10/05 suggested that breast cancer cases that have low levels of ECD show decreased benefit from adjuvant T therapy (Carvajal et al, 2015). These cases may be more likely to show benefit from lapatinib(L), a small molecular tyrosine kinase inhibitor. NeoALTTO, an international multi-institutional trial comparing pre-surgical treatment with L vs T vs both, showed that pCR rates were around 25-30% for L or T but increased to 50% for both. This cohort allows us to test the hypothesis that patients with low ECD may benefit more from L than T. Methods: ECD and ICD were measured 382 cases using quantitative immunofluorescence (QIF) with domain specific antibodies (SP3, Spring biosciences for ECD and CB11, Biocare for ICD). Slides were stained and scanned, then measured using the AQUA method of QIF. All fields of view were scored and FOVs were averaged to generate a QIF score for each case. Index TMAs were used to standardize all autostainer runs and to define the QIF score cut-point that is equivalent to the clinical cut-point for the index TMA cases. Each case was then assigned to one of three groups; 1) High ECD and ICD, 2) Low ECD but High ICD, and 3) low ICD. Results: In the lapatinib arm, both group 1 and 2 showed a pCR rate of 25% (p&amp;gt;0.99), but in the trastuzumab arm, Group 1 pCR rate was 34% compared to 19% for group 2 (p=0.38). In the combination arm, group 1 showed a pCR rate of 59% compared to 29% for group 2 (p=0.046). In a logistic regression model for pCR, after adjustment for treatment arm and HR status the ECD/ICD status shows a significant predictive value (p = 0.002). Although this study is not powered for event free survival (EFS), at 6 years of follow up we found that patients in group 2 on the lapatinib arm show 92% EFS compared to 69% EFS in group 1 (p=0.17). The opposite trend is seen in both trastuzumab arms where EFS for group 1 on T showed 70% vs 62% for group 2 (p=0.57) and 77% vs 71% on the T+L arm (p=0.74). In a Cox regression model for EFS after adjustment for treatment arm and HR status, the ECD/ICD status is not significant (p=0.88) Conclusions: Cases with low levels of ECD compared to ICD appear benefit less than those with high levels of both ECD and ICD as assessed by pCR from treatments containing T. In contrast, those same patients also appear to benefit more, as assessed by EFS, on the L arm. These observations are consistent with the hypothesis that this assay could stratify benefit from L vs T based on the status of the ECD. Further assessment using this assay on the ALTTO cases is currently underway and may help confirm this observation. Citation Format: Rimm DL, Carvajal-Hausdorf D, Harbeck N, Fumagalli D, Rodrik-Outmezguine V, delaPena L, deAzambuja E, Huober J, Baselga J, Piccart M, Holmes E, Pusztai L. Low levels of HER2 extracellular domain (ECD) compared to intracelluar domain (ICD) in NeoALTTO may segregate benefit from lapatinib and trastuzumab in breast cancer [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P2-09-07.

Abstract P2-09-18: Multiplexed (18-Plex) measurement of protein targets in trastuzumab-treated patients using imaging mass cytometry

Abstract Introduction: Recent studies have shown that the molecular heterogeneity of HER2 intracellular (ICD) and extracellular (ECD) domains, as well as overall immune infiltration, are associated with response to adjuvant trastuzumab. Traditional strategies for in situ measurement in the tumor microenvironment allow the combination of up to 6 targets, limiting our capability for in-depth interrogation of tissues. Imaging Mass Cytometry (IMC) uses metal-conjugated antibodies to provide multidimensional, objective measurement of protein targets. We used this high-throughput multiplexing platform to perform an 18-plex assessment of HER2 ICD/ECD, cytotoxic T cell infiltration and other structural and signaling proteins in a cohort of patients treated with trastuzumab. Methods: An antibody panel for detection of 18 targets (Pancytokeratin, HER2 ICD, HER2 ECD, CD8, vimentin, cytokeratin 7, beta-catenin, HER3, MET, EGFR, ERK 1-2, MEK 1-2, PTEN, PI3K p110 alpha, Akt, mTOR, Ki67 and Histone H3) was conjugated to unique metals for detection in an IMC instrument (Fluidigm). All assays were objectively standardized and validated using quantitative immunofluoresce (QIF). Finally, the IMC technique was validated against HER2 single marker assays by QIF. We used a collection of trastuzumab-treated patients from the HeCOG 10/05 trial (n=180), and identified a case:control series using 5-year recurrence events (n=19), which were matched to controls (n=41) by age and TNM stage. Formalin-fixed, paraffin embedded tissues in tissue microarray format were ablated in the IMC attachment to the CyTOF flow cytometer for simultaneous detection of markers. Image visualization was conducted using MCD Viewer (Fluidigm). Statistical analyses were performed using a range of platforms. Results: Patients that recurred after adjuvant treatment with trastuzumab showed a decreased fraction of HER2 ECD pixels over threshold in a compartment determined by CK and HER2 ICD compared to cases without recurrence (p=0.057). After exclusion of the lowest HER2 expressers (that would have fallen below the threshold for positive by current HER2 assays), 5-year recurrence events where associated with reduced total ECD/ ICD ratio intensity in tumor (p=0.044). Patients below the median for total ECD/ICD ratio showed a trend for decreased benefit from trastuzumab (p=0.066). Levels of cytotoxic T cell infiltration, depicted by total CD8 intensity, were lower in patients with recurrences (p=0.05). Conclusion: Objective measurement of highly multiplexed protein targets in routine, fixed breast cancer tissues shows that a decreased ratio of HER2 ECD/ ICD is associated with 5-year recurrence after trastuzumab treatment. This observation is consistent with our previous work using QIF but represents the first time this has been done on identical cell content (on a single tissue section). Additionally, on the same section we found that lower levels of overall cytotoxic T cell infiltration were associated with worse outcome. Further analysis of the multiplexed data, including both correlative and distance-based analyses are underway. Citation Format: Carvajal-Hausdorf DE, Stanton KP, Patsenker J, Villarroel-Espindola F, Esch A, Montgomery RR, Psyrri A, Kalogeras KT, Kotoula V, Fountzilas G, Schalper KA, Kluger Y, Rimm DL. Multiplexed (18-Plex) measurement of protein targets in trastuzumab-treated patients using imaging mass cytometry [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P2-09-18.

Design of cyclic and d-amino acids containing peptidomimetics for inhibition of protein-protein interactions of HER2-HER3.

HER2 receptors are surface proteins belonging to the epidermal growth factor family of receptors. Their numbers are elevated in breast, lung, and ovarian cancers. HER2-positive cancers are aggressive, have higher mortality rate, and have a poor prognosis. We have designed peptidomimetics that bind to HER2 and block the HER2-mediated dimerization of epidermal growth factor family of receptors. Among these, a symmetrical cyclic peptidomimetic (compound 18) exhibited antiproliferative activity in HER2-overexpressing lung cancer cell lines with IC50 values in the nanomolar concentration range. To improve the stability of the peptidomimetic, d-amino acids were introduced into the peptidomimetic, and several analogs of compound 18 were designed. Among the analogs of compound 18, compound 32, a cyclic, d-amino acid-containing peptidomimetic, was found to have an IC50 value in the nanomolar range in HER2-overexpressing cancer cell lines. The antiproliferative activity of compound 32 was also measured by using a 3D cell culture model that mimics the in vivo conditions. The binding of compound 32 to the HER2 protein was studied by surface plasmon resonance. In vitro stability studies indicated that compound 32 was stable in serum for 48hours and intact peptide was detectable in vivo for 12hours. Results from our studies indicated that 1 of the d-amino acid analogs of 18, compound 32, binds to the HER2 extracellular domain, inhibiting the phosphorylation of kinase of HER2.

Serum HER-2 extracellular domain for breast cancer patients

Serum HER-2 extracellular domain for breast cancer patients

A peptidomimetic with a chiral switch is an inhibitor of epidermal growth factor receptor heterodimerization.

Among different types of EGFR dimers, EGFR-HER2 and HER2-HER3 are well known in different types of cancers. Targeting dimerization of EGFR will have a significant impact on cancer therapies. A symmetric peptidomimetic was designed to inhibit the protein-protein interaction of EGFR. The peptidomimetic (Cyclo(1,10)PpR (R) Anapa-FDDF-(R)-Anapa)R, compound 18) was shown to exhibit antiproliferative activity with an IC50 of 194 nM in HER2-expressing breast cancer cell lines and 18 nM in lung cancer cell lines. The peptidomimetic has a Pro-Pro sequence in the structure to stabilize the β-turn and a β-amino acid, amino napthyl propionic acid. To investigate the effect of the chirality of β-amino acid on the structure of the peptide and its antiproliferative activity, diastereoisomers of compound 18 were designed and synthesized. Structure-activity relationships of these compounds indicated that there is a chiral switch at β-amino acid in the designed compound. The peptidomimetic with R configuration at β-amino acid and with a L-Pro-D-Pro sequence was the most active compound (18). Using enzyme complement fragmentation assay and proximity ligation assay, we show that compound 18 inhibits HER2:HER3 and EGFR:HER2 dimerization. Surface plasmon resonance studies suggested that compound 18 binds to the HER2 extracellular domain and in particular to domain IV. The anticancer activity of compound 18 was evaluated using a xenograft model of breast cancer in mice; compound 18 suppressed the tumor growth in mice compared to control. Compound 18 was also shown to have a synergistic effect with erlotinib on EGFR mutated lung cancer cell lines.

Abstract 1646: Highly cytotoxic, completely human constructs targeting HER2 and containing the immuno-oncology payload granzyme B

Abstract Recent immunotherapeutic approaches designed to augment T- and B-cell mediated killing of tumor cells has met with clinical success suggesting that immuno-oncology (IO) approaches have tremendous potential for treatment in a broad spectrum of tumor types. After complex recognition of target cells by T and B cells, delivery of the serine protease granzyme B (GrB) to tumor cells comprises the cytotoxic insult resulting in a well-characterized, multimodal apoptotic cascade. We designed a recombinant fusion construct composed of a human anti-Her2 scFv fused to active GrB for recognition and delivery of GrB to tumor cells simulating T and B-cell therapy. The GrB-Fc-4D5 dimeric construct (mw 160 kDa) was generated and expressed in stably-transfected CHO-S cells at ~60 mg/L and purified to homogeneity. The enzymatic activity of the fusion construct was similar to commercially-available GrB and the affinity of the construct for purified Her2 extracellular domain (ECD) was 0.328 nM, comparable to that of Herceptin (0.150 nM). The GrB-Fc-4D5 construct was highly cytotoxic to Her2-positive cells such as SKBR3, MCF7 and MDA-MB-231 with IC50 values of 56, 99 and 27 nM respectively. Using immunofluorescence, the fusion construct internalized rapidly into target (SKBR3 or SKOV3) cells within 1 h of exposure, rapidly delivering GrB to the cytoplasmic compartment in a similar manner to that of immune T and B-cell targeting but without the action of the transmembrane pore-forming agent perforin. Against a large panel of various tumor types, GrB-Fc-4D5 was highly cytotoxic to virtually all cells regardless of natural expression levels of the nominal endogenous GrB inhibitor PI-9. Contemporaneous studies with Kadcyla demonstrate similar levels of in vitro activity against virtually all HER2-positive cells tested. GrB-Fc-4D5 demonstrated activity against both log-phase and confluent tumor cells. In keeping with its relatively high molecular weight (~160 kDa), the construct demonstrated a terminal-phase half-life of 13.6 hrs. In vivo efficacy studies are currently ongoing in several orthotopic xenograft models. Also ongoing are pre-IND toxicology, histopathology and clinical chemistry studies. Research conducted, in part, by the Clayton Foundation for Research. Citation Format: Lawrence H. Cheung, Yunli Zhao, Khalid A. Mohamedali, Ana Alvarez-Cienfuegos, Walter N. Hittelman, Michael G. Rosenblum. Highly cytotoxic, completely human constructs targeting HER2 and containing the immuno-oncology payload granzyme B [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 1646. doi:10.1158/1538-7445.AM2017-1646

Molecular and hydrodynamic properties of human epidermal growth factor receptor HER2 extracellular domain and its homodimer: Experiments and multi-scale simulations

BackgroundIn a broad range of human carcinomas gene amplification leads to HER2 overexpression, which has been proposed to cause spontaneous dimerization and activation in the absence of ligand. This makes HER2 attractive as a therapeutic target. However, the HER2 homodimerization mechanism remains unexplored. It has been suggested that the “back-to-back” homodimer does not form in solution. Notwithstanding, very recently the crystal structure of the HER2 extracellular domain homodimer formed with a “back-to-head” interaction has been resolved. We intend to explore the existence of such interactions. MethodsA combination of experiments, molecular dynamics and hydrodynamic modeling were used to monitor the transport properties of HER2 in solution. Results & conclusionsWe have detected the HER2 extracellular domain homodimer in solution. The results show a high degree of molecular flexibility, which ultimately leads to quite higher values of the intrinsic viscosity and lower values of diffusion coefficient than those corresponding to globular proteins. This flexibility obeys to the open conformation of the receptor and to the large fluctuations of the different domains. We also report that for obtaining the correct hydrodynamic constants from the modeling one must consider the glycosylation of the systems. General significanceConformational features of epidermal growth factor receptors regulate their hydrodynamic properties and control their activity. It is essential to understand the dynamics of these systems and the role of the specific domains involved. To find biophysical correlations between dynamics and macroscopic transport properties is of general interest for researches working in this area. This article is part of a Special Issue entitled “Biochemistry of Synthetic Biology - Recent Developments” Guest Editor: Dr. Ilka Heinemann and Dr. Patrick O'Donoghue.

Quantification of Circulating Cancer Biomarkers via Sensitive Topographic Measurements on Single Binder Nanoarrays.

Early detection of cancer plays a crucial role in disease prognosis. It requires the recognition and quantification of low amounts of specific molecular biomarkers, either free or transported inside nanovesicles, through the development of novel sensitive diagnostic technologies. In this context, we have developed a nanoarray platform for the noninvasive quantification of cancer biomarkers circulating in the bloodstream. The assay is based on molecular manipulation to create functional spots of surface-immobilized binders and differential topography measurements. It is label-free and requires just a single binder per antigen, and when it is implemented with fluorescence labeling/readout, it can be used for epitope mapping. As a benchmark, we focused on the plasma release of Her2 extracellular domain (ECD), a proposed biomarker for the progression of Her2-positive tumors and response to anticancer therapies. By employing robust, easily engineered camelid nanobodies as binders, we measured ECD-Her2 concentrations in the range of the actual clinical cutoff value for Her2-positive breast cancer. The specificity for Her2 detection was preserved when it was measured in parallel with other potential biomarkers, demonstrating a forthcoming implementation of this approach for multiplexing analysis. Prospectively, this nanorarray platform may be customized to allow for the detection of promising new classes of circulating biomarkers, such as exosomes and microvesicles.

Antibody Response to Human Extracellular HER2 Subdomain Proteins in Mice.

In addition to passive immunotherapy using anti-HER2 monoclonal antibodies, active immunotherapy via HER2 targeting is an interesting approach to inducing specific anti-tumor immune responses. We have recently reported the immunogenicity of HER2 subdomains following DNA immunization and HER2 protein boosting. In the present study, we evaluated the immunogenicity of different HER2 extracellular subdomains for the induction of anti-HER2 antibody response in BALB/c mice. To investigate and characterize antibody responses to human recombinant proteins of HER2 extracellular subdomains in immunized mice. Four subdomains of HER2 extracellular domain were expressed in E.coli; subsequently, purified recombinant proteins were intraperitoneally injected in BALB/c mice with Freund's adjuvant. The anti-HER2 antibody response was detected by ELISA, immunoblotting and flow cytometry. All the four HER2 subdomains along with the full extracellular domain (fECD) were able to induce specific anti-HER2 antibodies. Although anti-HER2 subdomains antibodies could not react with eukaryotic recombinant fECD protein by ELISA, they were able to recognize this protein by immunoblotting under both reduced and non-reduced conditions. Furthermore, only the sera of mice immunized with fECD protein could recognize native HER2 on HER2 overexpressing tumor cells (>99%) by flow cytometry. Moreover, fECD immunized mice sera inhibited the proliferation of tumor cells by XTT assay. The prokaryotic recombinant proteins of HER2 extracellular subdomains are immunogenic, yet the induced specific antibodies do not react with the native HER2 protein due to the paucity of post-translation modifications and /or distortion of the native conformation of isolated HER2 extracellular subdomains which might be potentially effective for induction of cell mediated immune response against HER2.

Phase 1 dose escalation of ZW25, a HER2-targeted bispecific antibody, in patients (pts) with HER2-expressing cancers.

1035 Background: The HER2 receptor is expressed across a range of cancers (ca) although expression and heterogeneity vary greatly within and between tumors. FDA approved HER2-targeted therapies (tx) have shown clinical benefit only in HER2 high (IHC3+ or IHC2+/FISH+) breast and gastric ca. ZW25, built on the Azymetric™ platform which utilizes unique Fc mutations to create IgG1-like bispecific antibodies, binds to the same extracellular domains of HER2 as trastuzumab (T) and pertuzumab (P) with increased binding and internalization compared to T alone. In preclinical studies ZW25 was well tolerated and active in models of HER2 low to high ca. Methods: Eligible pts (HER2 IHC 1-3+, progression after standard of care (SOC) tx, normal LVEF) were enrolled in a 3+3 dose escalation study of ZW25 (5, 10 or 15 mg/kg) IV weekly in 4 week cycles. Assessments included adverse events (AEs), LVEF, tumor response and PK. Results: 9 pts have received ZW25 at 5 (n = 3) or 10 mg/kg (n = 6); 15 mg/kg is ongoing. All pts were HER2 high (breast = 4; gastric/GEJ = 4; adnexal = 1). Prior tx included T in all pts; P and T-DM1 in 4 and lapatinib (L) in 3 of 4 breast pts. The most common AEs (all Gr 1/2) were infusion reaction (IR) (5/9), diarrhea (4/9), and fatigue (3/9), with no DLTs and one related Gr 3 AE of hypophosphatemia. The IRs occurred only with 1st dose and did not recur with prophylactic tx (primarily acetaminophen and diphenhydramine; steroids included for 2 pts). At 5 mg/kg, peak drug levels after C1D1 = ~100 ug/ml, accumulating ~50% higher by dose 4. Best response in 8 pts (1 too early): 2 PR (both breast ca with prior T, P, T-DM1, and L; 10 mg/kg, 55% and 33% target lesion decrease, respectively, after 2 cycles), 1 SD (breast ca, 5 mg/kg, ongoing after 4 cycles), and 5 PD. 5 pts currently active; includes 1 gastric pt (10 mg/kg) with PD (new nodal lesions) and clinical benefit with decrease in target lesions and CEA (33 to 1.5 ng/ml). Conclusions: ZW25 has been well tolerated with promising anti-tumor activity in pts with HER2-expressing ca progressing after SOC therapy. These early signs of activity support the therapeutic potential for bispecific antibodies using the Azymetric platform. Development of ZW25 is ongoing, including in lower HER2-expressing ca. Clinical trial information: NCT02892123.

Association of autologous AdHER2 dendritic cell vaccination with antitumor activity and number of circulating tumor cells.

3089 Background: We achieved cure of large established tumors in syngeneic BALB/c mice using an adenoviral vector vaccine expressing rodent HER2 extracellular (EC) and transmembrane (TM) domains mediated by the induction of anti-HER2 antibodies. We report clinical translation utilizing an autologous adenoviral- transduced dendritic cell (DC) vaccine expressing human HER2 EC and TM domains (AdHER2ECTM) in adults with advanced metastatic tumors with 1-3+ HER2 expression. Methods: In this two-part phase I study (NCT01730118) subjects with HER2+ metastatic solid tumors naïve to HER2-targeted therapies (Part 1) or HER2+ treatment-experienced breast cancer (Part 2) received 5 doses of vaccine at Weeks 0, 4, 8, 16 and 24. Part 1 dose escalation involved 3 cohorts of 6 patients utilizing 5x106, 10x106 and 20x106 viable DCs per dose, respectively. With no DLTs or evidence of cardiac toxicity, dose escalation to 40x106 viable DCs per dose was allowed in the Part 1 Expansion Cohort and Part 2 treatment was begun at a starting dose of 20x106 viable DCs per vaccine. Adjuvant muscle-invasive bladder cancer patients were allowed to enroll with safety documented out to 12 weeks in &gt; 10 treated patients. Re-staging was assessed using immune-related response criteria (irRC). Remaining study accrual: Part 1 (N = 9), Part 2 (N = 24). Results: A total of 27 cancer patients (7 colon, 6 breast, 5 ovarian, 3 bladder, 6 other) have received &gt; 2 vaccine doses (median 4): 19F, 8M, median age 60 yrs, median 3 prior treatment regimens (range 1-11); HER2 IHC 1+ N = 6, 2+ N = 9, 3+ N = 12. Of metastatic patients receiving 10x106viable DCs per dose or higher, 7 of 19 (37%) had evidence of response by irRC: 1 CR (ongoing at 100 weeks), 1 PR (-71% lasting 44 weeks) and 5 SD (median duration 24 weeks, range 8 to 48 weeks). Two adjuvant bladder cancer patients remain without disease at 100 weeks. Adverse events were limited to local injection site reactions &lt; G2. Of patients with paired baseline samples, 40% (8/20), 83% (5/6) and 100% (2/2) exhibited decreases in circulating tumor cells at 12, 28 and 48 weeks, respectively. Conclusions: AdHER2 DC vaccination is safe and is associated with evidence of clinical benefit and anti-tumor activity. Clinical trial information: NCT01730118.