Adeno-Associated Virus-Mediated Dorsal Root Ganglion Toxicity in the New Zealand White Rabbit

Recombinant adeno-associated virus (AAV)-mediated degeneration of sensory neurons in the dorsal root ganglia (DRG) and trigeminal ganglia (TG) has been observed in non-human primates (NHPs) following intravenous (IV) and intrathecal (IT) delivery. Administration of recombinant AAV encoding a human protein transgene via a single intra-cisterna magna (ICM) injection in New Zealand white rabbits resulted in histopathology changes very similar to NHPs: mononuclear cell infiltration, degeneration/necrosis of sensory neurons, and nerve fiber degeneration of sensory tracts in the spinal cord and of multiple nerves. AAV-associated clinical signs and incidence/severity of histologic findings indicated that rabbits were equally or more sensitive than NHPs to sensory neuron damage. Another study using human and rabbit transgene constructs of the same protein demonstrated comparable changes suggesting that the effects are not an immune response to the non-self protein transgene. Rabbit has not been characterized as a species for general toxicity testing of AAV gene therapies, but these studies suggest that it may be an alternative model to investigate mechanisms of AAV-mediated neurotoxicity and test novel AAV designs mitigating these adverse effects.

Genomic characterization of thymic epithelial tumors in a real-world dataset

BACKGROUND

Thymic epithelial tumors (TETs) are rare neoplasms arising in the mediastinum, including thymic carcinomas and thymomas. Due to their rarity, little is known about the genomic profiles of TETs. Herein, we investigated the genomic characteristics of TETs evaluated in a large comprehensive genomic profiling database in a real-world setting.

METHODS

We included data from two different cohorts: Foundation Medicine Inc. (FMI) in the United States and the Center for Cancer Genomics and Advanced Therapeutics (C-CAT) in Japan. Samples profiled were examined for all classes of alterations in 253 genes targeted across all assays. Tumor mutational burden (TMB) and microsatellite instability (MSI) were also evaluated.

RESULTS

A total of 794 patients were collected in our study, including 722 cases from FMI and 72 cases from C-CAT. In the FMI data, CDKN2A (39.9%), TP53 (30.2%) and CDKN2B (24.6%) were frequently altered in thymic carcinoma, versus TP53 (7.8%), DNMT3A (6.8%), and CDKN2A (5.8%) in thymoma. TMB-high (≥10 mutations/Mb) and MSI were present in 7.0% and 2.3% of thymic carcinomas, and 1.6% and 0.3% of thymomas, respectively. Within C-CAT data, CDKN2A (38.5%), TP53 (36.5%) and CDKN2B (30.8%) were also frequently altered in thymic carcinoma, while alterations of TSC1, SETD2 and LTK (20.0% each) were found in thymoma.

CONCLUSIONS

To the best of our knowledge, this is the largest cohort in which genomic alterations, TMB and MSI status of TETs were investigated. Potential targets for treatment previously unbeknownst in TETs are identified in this study, entailing newfound opportunities to advance therapeutic development.

First Evidence of Axial Shape Asymmetry and Configuration Coexistence in ^{74}Zn: Suggestion for a Northern Extension of the N=40 Island of Inversion

The excited states of N=44 ^{74}Zn were investigated via γ-ray spectroscopy following ^{74}Cu β decay. By exploiting γ-γ angular correlation analysis, the 2_{2}^{+}, 3_{1}^{+}, 0_{2}^{+}, and 2_{3}^{+} states in ^{74}Zn were firmly established. The γ-ray branching and E2/M1 mixing ratios for transitions deexciting the 2_{2}^{+}, 3_{1}^{+}, and 2_{3}^{+} states were measured, allowing for the extraction of relative B(E2) values. In particular, the 2_{3}^{+}→0_{2}^{+} and 2_{3}^{+}→4_{1}^{+} transitions were observed for the first time. The results show excellent agreement with new microscopic large-scale shell-model calculations, and are discussed in terms of underlying shapes, as well as the role of neutron excitations across the N=40 gap. Enhanced axial shape asymmetry (triaxiality) is suggested to characterize ^{74}Zn in its ground state. Furthermore, an excited K=0 band with a significantly larger softness in its shape is identified. A shore of the N=40 "island of inversion" appears to manifest above Z=26, previously thought as its northern limit in the chart of the nuclides.

Heart failure with improved ejection fraction (HFimpEF) in patients treated with sacubitril/valsartan (SV)

Introduction

Several studies demonstrated that patients with improvement of left ventricular ejection fraction (LVEF) and symptoms had good prognosis in heart failure with reduced ejection fraction (HFrEF). Based on these results, new classification of HF according to LVEF was currently proposed. Sacubitril/valsartan (SV) is recommended as one of the first-line therapy of HFrEF patients. SV reduced hospitalization for HF and cardiovascular mortality compared to enalapril in PARADIGM-HF trial. However, it is unclear that patients with improvement of LVEF also have better prognosis compared to patients without LVEF improvement among patients treated with SV.

Purpose

We aimed to evaluate the clinical characteristics and outcomes of heart failure with improved ejection fraction (HFimpEF) in heart failure with reduced ejection fraction (HFrEF) patients treated with SV.

Methods

We analyzed 230 patients with HFrEF taking SV in a multicenter retrospective cohort (RECORD-SV registry) from 2017 to 2019. Enrolled 230 patients were performed baseline and 1-year follow-up echocardiography. Based on 2 echocardiographic results, we defined “HFimpEF” as HF with a baseline LVEF ≤40%, ≥10% increase from baseline LVEF and a follow-up measurement of LVEF >40%. Others were defined as “Persistent HFrEF”. We analyzed and compared clinical characteristics and outcomes between two groups. Primary endpoint was a composite outcome of all-cause death and hospitalization for HF (HHF).

Results

From 230 patients, 65 patients with HFimpEF and 165 patients with Persistent HFrEF were analyzed. The median follow-up duration was 557 days (interquartile range 364 to 727 days). Patients with HFimpEF had a higher prevalence of female gender (50.8% vs. 30.3%) and de novo HF (44.6% vs. 21.2%). There were no significant differences for age, etiology (ischemic vs. non-ischemic), diabetes, atrial fibrillation, hypertension, and HF medications including SV dose between two groups. Patients with HFimpEF showed lower rate of all-cause death or HHF as a primary endpoint compared to patients with persistent HFrEF (6.2% vs. 22.4%; IPTW adjusted HR 0.24; 95% CI 0.13–0.46; p<0.001) (Table 1). It was also shown that HFimpEF patients had a reduced risk of primary endpoint in the Kaplan-Meier curves compared with persistent HFrEF (Log-rank p=0.045) (Figure 1). We demonstrated that Non-prior MI (adjusted OR 7.29; 95% CI 1.50–35.36; p=0.014) and de novo HF (adjusted OR 4.33; 95% CI 1.70–11.04; p=0.002) were independent prognostic factors of HFimpEF in HFrEF patients treated with SV.

Conclusions

HFimpEF patients had better clinical outcomes compared to those with persistent HFrEF in HFrEF patients treated with SV. Non-prior MI and de novo HF were independent predictors of HFimpEF in patients treated with SV.

Funding Acknowledgement

Type of funding sources: None.

AB0339 EFFICACY, PHARMACOKINETICS AND SAFETY BETWEEN CT-P13 AND CHINA-APPROVED INFLIXIMAB: 54 WEEK RESULT FROM A PHASE III RANDOMIZED CONTROLLED TRIAL IN CHINESE PATIENTS WITH ACTIVE RHEUMATOID ARTHRITIS

Background

CT-P13 is an approved biosimilar to EU-approved and US-licensed Infliximab (INX) for the indications of rheumatoid arthritis (RA), adult and paediatric Crohn’s disease, adult and paediatric ulcerative colitis, ankylosing spondylitis, psoriatic arthritis and psoriasis.

Objectives

The purpose of this study was to demonstrate equivalence of efficacy and compare PK and safety profiles of CT-P13 and China-approved INX.

Methods

In this randomized, double blinded, multicenter, parallel-group, phase III study, patients with active RA who had been responding inadequately to methotrexate for at least 3 months, were randomized to receive either CT-P13 or China-approved INX. Patients were treated with doses of 3 mg/kg at Weeks 0, 2, 6, then every 8 weeks up to Week 54. Prior to dosing at Week 30, patients randomized to China-approved INX underwent a second randomization either to continue China-approved INX or to switch to CT-P13 at Week 30. Results of patients who underwent transition to CT-P13 were included in the China-approved INX group. The primary efficacy endpoint was change in DAS28 (CRP) from baseline to Week 14, which was analyzed using an analysis of covariance. Equivalence was determined if the 90% CI for the estimate of treatment difference was entirely contained within the predefined equivalence margin of -0.6 to 0.6.

Results

270 patients were randomly assigned to 2 treatment groups in a 1:1 ratio (136 and 134 patients in the CT-P13 and China-approved INX groups, respectively) and 184 patients completed the study. The least square mean change (standard error) of DAS28 (CRP) from baseline to Week 14, -1.566 [0.1419] and -1.547 [0.1491], was similar between the CT-P13 and China-approved INX groups, respectively. The 90% CI for the estimate of treatment difference (-0.29, 0.25) was contained within the predefined equivalence margin, which demonstrated therapeutic equivalence between the groups. The mean actual values for DAS28 (CRP) decreased from baseline to Week 54 and were similar between the groups (Figure 1). Additional efficacy endpoints, including ACR responses (ACR20 at Week 14; 60.6%, 54.8% and at Week 54; 65.1%, 60.6% in the CT-P13 and China-approved INX groups, respectively), EULAR responses, CDAI, and SDAI, were similar between the groups, even after switching at Week 30. During the study, mean serum INX concentrations were similar between the groups. Between Weeks 14 and 22, mean (percent coefficient of variation) AUCτ were 11156333.615 (44.796) ng·h/mL and 11462884.280 (51.057) ng·h/mL, and Cmax,ss were 66577.2 (31.4) ng/mL and 66356.1 (21.0) ng/mL in the CT-P13 and China-approved INX groups, respectively, which were similar between the groups. Most treatment-emergent AEs were grade 1 or 2 in intensity. One malignancy was reported in the CT-P13 group and no deaths were reported. The proportions of patients with anti-drug antibodies were similar between the groups, even after switching at Week 30. The overall safety profile of CT-P13 was comparable to that of China-approved INX and no new safety issues were observed (Table 1).

Table 1.

Summary of Safety Results

Number of patients (%)CT-P13 (N=136)China-approved Infliximab (N=133)Treatment-emergent AEsTotal115 (84.6%)107 (80.5%)Related97 (71.3%)86 (64.7%)Treatment-emergent serious AEsTotal17 (12.5%)12 (9.0%)Related10 (7.4%)6 (4.5%)Infusion related reaction/ hypersensitivity/anaphylactic reactionsTotal(=Related)20 (14.7%)19 (14.3%)InfectionsTotal45 (33.1%)43 (32.3%)Related36 (26.5%)40 (30.1%)

Note: Summary is presented for the safety population who received at least 1 dose (full or partial) of study drug.

Conclusion

The study demonstrated that efficacy of CT-P13 is equivalent to that of China-approved INX. Also, the PK and safety profiles of CT-P13 were comparable to those of China-approved INX. No loss of efficacy or difference in safety or immunogenicity was observed after switching from China-approved INX to CT-P13 at Week 30.

Disclosure of Interests

Jonathan Kay Consultant of: Boehringer Ingelheim GmbH; Pfizer Inc.; Samsung Bioepis; Sandoz Inc., Grant/research support from: Pfizer Inc. (paid to UMass Chan Medical School), Xiaofeng Zeng Grant/research support from: Celltrion, Inc, Lin Chen Grant/research support from: Celltrion, Inc, Kaijiang Tang Grant/research support from: Celltrion, Inc, guixiu shi Grant/research support from: Celltrion, Inc, Lin Liu Grant/research support from: Celltrion, Inc, Lijun Wu Grant/research support from: Celltrion, Inc, Yi Liu Grant/research support from: Celltrion, Inc, Jiankang Hu Grant/research support from: Celltrion, Inc, Shengyun Liu Grant/research support from: Celltrion, Inc, Zheng Yi Grant/research support from: Celltrion, Inc, Sung Hyun Kim Employee of: Celltrion, Inc, YunJu Bae Employee of: Celltrion, Inc, JeeHye Suh Employee of: Celltrion, Inc, Seungjin Rhee Employee of: Celltrion, Inc, SeulGi Lee Employee of: Celltrion, Inc, Chankyoung Hwang Employee of: Celltrion, Inc

N-terminal serine/threonine motif has diverse and important effects on behavior of multiple AAV serotypes

Adeno-associated virus (AAV) is a promising gene therapy vector, but questions remain regarding mechanisms of basic viral functions. We previously showed that a serine/threonine (S/T) triplet motif and its flanking residues, located in the overlapping N-terminus of VP1/VP2 and highly conserved across most AAV serotypes, are critical for viral transcript production in vitro. Here we generate a panel of S/T triplet mutants in AAV serotypes 2, 4, and 9 and characterize their behaviors in vitro and in vivo using next generation sequencing. We show that S/T triplet mutations can significantly hinder some stages of transduction in a serotype-dependent manner in vitro. Interestingly, these defects are largely overcome in C57BL/6 mice, with only one mutant displaying altered behavior in vivo. Taken together, our results identify a short N-terminal capsid motif with diverse roles across several AAV serotypes which better informs engineering efforts to improve AAV as a vector for gene therapy.

Membrane-bound MMP-14 protease-activatable adeno-associated viral vectors for gene delivery to pancreatic tumors

Adeno-associated virus' (AAV) relatively simple structure makes it accommodating for engineering into controllable delivery platforms. Cancer, such as pancreatic ductal adenocarcinoma (PDAC), are often characterized by upregulation of membrane-bound proteins, such as MMP-14, that propagate survival integrin signaling. In order to target tumors, we have engineered an MMP-14 protease-activatable AAV vector that responds to both membrane-bound and extracellularly active MMPs. This "provector" was generated by inserting a tetra-aspartic acid inactivating motif flanked by the MMP-14 cleavage sequence IPESLRAG into the capsid subunits. The MMP-14 provector shows lower background transduction than previously developed provectors, leading to a 9.5-fold increase in transduction ability. In a murine model of PDAC, the MMP-14 provector shows increased delivery to an allograft tumor. This proof-of-concept study illustrates the possibilities of membrane-bound protease-activatable gene therapies to target tumors.

Frustration and Direct-Coupling Analyses to Predict Formation and Function of Adeno-Associated Virus

Adeno-associated virus (AAV) is a promising gene therapy vector because of its efficient gene delivery and relatively mild immunogenicity. To improve delivery target specificity, researchers use combinatorial and rational library design strategies to generate novel AAV capsid variants. These approaches frequently propose high proportions of nonforming or noninfective capsid protein sequences that reduce the effective depth of synthesized vector DNA libraries, thereby raising the discovery cost of novel vectors. We evaluated two computational techniques for their ability to estimate the impact of residue mutations on AAV capsid protein-protein interactions and thus predict changes in vector fitness, reasoning that these approaches might inform the design of functionally enriched AAV libraries and accelerate therapeutic candidate identification. The Frustratometer computes an energy function derived from the energy landscape theory of protein folding. Direct-coupling analysis (DCA) is a statistical framework that captures residue coevolution within proteins. We applied the Frustratometer to select candidate protein residues predicted to favor assembled or disassembled capsid states, then predicted mutation effects at these sites using the Frustratometer and DCA. Capsid mutants were experimentally assessed for changes in virus formation, stability, and transduction ability. The Frustratometer-based metric showed a counterintuitive correlation with viral stability, whereas a DCA-derived metric was highly correlated with virus transduction ability in the small population of residues studied. Our results suggest that coevolutionary models may be able to elucidate complex capsid residue-residue interaction networks essential for viral function, but further study is needed to understand the relationship between protein energy simulations and viral capsid metastability.

Constructing and evaluating caspase-activatable adeno-associated virus vector for gene delivery to the injured heart

Adeno-associated virus (AAV) is a promising vector for gene therapy, but its broad tropism can be detrimental if the transgene being delivered is harmful when expressed ubiquitously in the body, i.e. in non-target tissues. Delivering the transgene of interest to target cells at levels high enough to be therapeutically effective while maintaining safety by minimizing delivery to off-target cells is a prevalent challenge in the field of gene therapy. We have developed a protease activatable vector (provector) platform based on AAV9 that can be injected systemically to deliver therapeutic transgenes site-specifically to diseased cells by responding to extracellular proteases present at the disease site. The provector platform consists of a peptide insertion into the virus capsid which disrupts the virus' ability to bind to cell surface receptors. This peptide contains a blocking motif (aspartic acid residues) flanked on either side by cleavage sequences that are recognized by certain proteases. Exposure to proteases cleaves the peptides off the capsid, activating or "switching ON" the provector. In response to the activation, the provectors regain their ability to bind and transduce cells. Here, we have designed a provector that is activated by cysteine aspartic proteases (caspases), which have roles in inflammation and apoptosis and thus are elevated at sites of diseases such as heart failure, neurodegenerative diseases, and ischemic stroke. This provector demonstrates a 200-fold reduction in transduction ability in the OFF state compared to AAV9, reducing the virus' ability to transduce off-target healthy tissue. Following exposure to and proteolysis by caspase-3, the provector shows a 95-fold increase in transduction compared to the OFF state. The switchable transduction behavior was found to be a direct result of the peptide insertion ablating the ability of the virus to bind to cells. In vivo studies were conducted to characterize the biodistribution, blood circulation time, neutralizing antibody formation, and targeted delivery ability of the caspase-activatable provector in a model of heart failure.

Adeno-associated virus characterization for cargo discrimination through nanopore responsiveness

Solid-state nanopore (SSN)-based analytical methods have found abundant use in genomics and proteomics with fledgling contributions to virology - a clinically critical field with emphasis on both infectious and designer-drug carriers. Here we demonstrate the ability of SSN to successfully discriminate adeno-associated viruses (AAVs) based on their genetic cargo [double-stranded DNA (AAVdsDNA), single-stranded DNA (AAVssDNA) or none (AAVempty)], devoid of digestion steps, through nanopore-induced electro-deformation (characterized by relative current change; ΔI/I0). The deformation order was found to be AAVempty > AAVssDNA > AAVdsDNA. A deep learning algorithm was developed by integrating support vector machine with an existing neural network, which successfully classified AAVs from SSN resistive-pulses (characteristic of genetic cargo) with >95% accuracy - a potential tool for clinical and biomedical applications. Subsequently, the presence of AAVempty in spiked AAVdsDNA was flagged using the ΔI/I0 distribution characteristics of the two types for mixtures composed of ∼75 : 25% and ∼40 : 60% (in concentration) AAVempty : AAVdsDNA.

Display of Self-Peptide on Adeno-Associated Virus Capsid Decreases Phagocytic Uptake in Vitro

Adeno-associated virus (AAV) vectors are currently investigated as gene transfer agents for the treatment of a variety of diseases. However, activation of the host immune response upon vector administration limits the use of AAV in the clinical setting. To decrease host detection of AAVs, we tested the CD47-based "don't-eat-me" signal in the context of the AAV capsid. We genetically incorporated the bioactive region of CD47, named "self-peptide" (SP), onto the surface of the AAV2 capsid. AAV mutants were structurally and functionally characterized for vector production, SP and linker incorporation into the capsid, transduction efficiency, and phagocytic susceptibility. We demonstrate that utilizing linkers improves the AAV2 capsid's tolerance to SP insertion. Notably, the SP significantly decreases the phagocytic susceptibility of AAV2 in vitro. Collectively, these results suggest that display of the SP motif on the AAV capsid surface can inhibit phagocytosis of the vector in vitro via the "don't-eat-me" signaling.

THU0186 CLINICAL EVALUATION OF THE IMMUNOGENICITY TO CT-P13 FOR SUBCUTANEOUS USE IN PATIENTS WITH ACTIVE RHEUMATOID ARTHRITIS: 1-YEAR CLINICAL RESULTS FROM A MULTICENTER, RANDOMIZED CONTROLLED PIVOTAL TRIAL

Background:

Novel subcutaneous infliximab (CT-P13 SC) was developed to augment the flexibility in therapeutic use of infliximab and noninferiority (NI) of CT-P13 SC versus CT-P13 intravenous (IV) was demonstrated for efficacy in patients with rheumatoid arthritis (RA) [1]. CT-P13 SC 120mg biweekly showed consistent higher therapeutic trough levels during the treatment period, which helps in maintaining efficacy over time. Since immunogenicity has clinical importance in patients using anti-TNF alpha agents and there is a general presumption that SC route is more immunogenic than IV route, this needs careful assessment.

Objectives:

Immunogenicity assessment of CT-P13 SC with further impact analysis has been performed on the pivotal data set [1] to determine whether there was any correlation between the magnitude of anti-drug antibody (ADA) positivity and clinical outcomes in RA patients.

Methods:

The immune response against CT-P13 in human serum was detected using an electrochemiluminescence (ECL) platform with an Affinity Capture Elution (ACE) step. An ADA ECL ACE assay showed ability to detect ADA at low levels in all samples regardless of residual drug in serum (25 ng/mL ADA in the presence of 80 μg/mL of CT-P13 in RA serum). To investigate the impact of ADA titer on PK, efficacy and safety, key clinical parameters were assessed by visit based ADA titer quartile. All patients who had ‘Positive’ ADA status result at each visit were included in the analysis and categorized into 4 groups using the 25th, 50th, 75th percentiles of ADA titer result, respectively.

Results:

The four subgroups categorized by quartiles at each visit from week 22 to week 54 were: 1st (ADA titer ≤ 3), 2nd (3 < ADA titer ≤ 9), 3rd (9 < ADA titer ≤ 27) and 4th (27 < ADA titer). There was a trend for pre-dose concentration to decrease as ADA titer increases for both CT-P13 SC and CT-P13 IV arms as expected (Figure 1). Patients in the 1st and 2nd subgroup maintained the sufficient therapeutic drug concentration level. Figure 2 shows the correlation between ADA titer and efficacy outcomes where the change from baseline of DAS28 (CRP) and the proportion of patients achieving ACR20 were lower in the 3rd and 4th subgroups. The ADA impact was especially apparent in the 4th subgroup where the mean pre-dose concentration of the patients was below the therapeutic drug concentration level (1 μg/mL), which led to worse efficacy outcomes in both arms, IV as well as SC. Nevertheless, no impact of ADA on safety profile in both arms was observed. A neutralizing antibody (NAb) method with enhanced drug tolerance but limited performance was also developed and clinical consequences of NAb titer in terms of PK, efficacy and safety were not different from the results with ADA.

Conclusion:

The analysis of both ADA positivity and titer is clinically meaningful in the prediction of PK profile and clinical response. CT-P13 SC administration did not result in a greater incidence of ADA compared to the CT-P13 IV and there were no clinical differences depending on the formulation.

References:

[1]Westhovens R, et al. Annals of the Rheumatic Diseases 2019;78:1158-1159.

Disclosure of Interests:

Rene Westhovens Grant/research support from: Celltrion Inc, Galapagos, Gilead, Consultant of: Celltrion Inc, Galapagos, Gilead, Speakers bureau: Celltrion Inc, Galapagos, Gilead, DaeHyun Yoo Grant/research support from: Celltrion, Inc, Consultant of: Celltrion, Inc, Speakers bureau: Celltrion Healthcare, Inc, Piotr Wiland Grant/research support from: Celltrion, Inc, Speakers bureau: Novartis, Pfizer, Abbvie, Gedeon-Richter, Lilly, Roche, Sandoz, Marek Zawadzki Grant/research support from: Celltrion, Inc, Delina Ivanova Grant/research support from: Celltrion, Inc, Alfredo Berrocal Grant/research support from: Celltrion, Inc, Speakers bureau: Pfizer, Elias Chalouhi Grant/research support from: Celltrion, Inc, Éva Balázs Grant/research support from: Celltrion, Inc, Consultant of: Amgen, Sergii Shevchuk Grant/research support from: Celltrion, Inc, Sang Joon Lee Shareholder of: Celltrion, Inc, Employee of: Celltrion, Inc, Sung Hyun Kim Shareholder of: Celltrion, Inc, Employee of: Celltrion, Inc, JeeHye Suh Employee of: Celltrion, Inc, Chankyoung Hwang Employee of: Celltrion, Inc, Dae Seok Choi Shareholder of: Celltrion, Inc, Employee of: Celltrion, Inc

Site-Specific Post-translational Surface Modification of Adeno-Associated Virus Vectors Using Leucine Zippers

Adeno-associated virus (AAV) is widely favored as a gene therapy vector, tested in over 200 clinical trials internationally. To improve targeted delivery a variety of genetic capsid modifications, such as insertion of targeting proteins/peptides into the capsid shell, have been explored with some success but larger insertions often have unpredictable deleterious impacts on capsid formation and gene delivery. Here, we demonstrate a modular platform for the integration of exogenous peptides and proteins onto the AAV capsid post-translationally while preserving vector functionality. We decorated the AAV capsid with leucine-zipper coiled-coil binding motifs that exhibit specific noncovalent heterodimerization. AAV capsids successfully display hexahistidine tagged-peptides using this approach, as demonstrated through nickel column affinity. This protein display platform may facilitate the incorporation of biological moieties on the AAV surface, expanding possibilities for vector enhancement and engineering.

Recurrent hyperactive ESR1 fusion proteins in endocrine therapy-resistant breast cancer

Background

Estrogen receptor-positive (ER-positive) metastatic breast cancer is often intractable due to endocrine therapy resistance. Although ESR1 promoter switching events have been associated with endocrine-therapy resistance, recurrent ESR1 fusion proteins have yet to be identified in advanced breast cancer.

Patients and methods

To identify genomic structural rearrangements (REs) including gene fusions in acquired resistance, we undertook a multimodal sequencing effort in three breast cancer patient cohorts: (i) mate-pair and/or RNAseq in 6 patient-matched primary-metastatic tumors and 51 metastases, (ii) high coverage (>500×) comprehensive genomic profiling of 287-395 cancer-related genes across 9542 solid tumors (5216 from metastatic disease), and (iii) ultra-high coverage (>5000×) genomic profiling of 62 cancer-related genes in 254 ctDNA samples. In addition to traditional gene fusion detection methods (i.e. discordant reads, split reads), ESR1 REs were detected from targeted sequencing data by applying a novel algorithm (copyshift) that identifies major copy number shifts at rearrangement hotspots.

Results

We identify 88 ESR1 REs across 83 unique patients with direct confirmation of 9 ESR1 fusion proteins (including 2 via immunoblot). ESR1 REs are highly enriched in ER-positive, metastatic disease and co-occur with known ESR1 missense alterations, suggestive of polyclonal resistance. Importantly, all fusions result from a breakpoint in or near ESR1 intron 6 and therefore lack an intact ligand binding domain (LBD). In vitro characterization of three fusions reveals ligand-independence and hyperactivity dependent upon the 3' partner gene. Our lower-bound estimate of ESR1 fusions is at least 1% of metastatic solid breast cancers, the prevalence in ctDNA is at least 10× enriched. We postulate this enrichment may represent secondary resistance to more aggressive endocrine therapies applied to patients with ESR1 LBD missense alterations.

Conclusions

Collectively, these data indicate that N-terminal ESR1 fusions involving exons 6-7 are a recurrent driver of endocrine therapy resistance and are impervious to ER-targeted therapies.

P6445Stress hyperglycemia and in-hospital mortality in patients with ST-segment elevation myocardial infarction

Introduction

Stress hyperglycemia is common in acute ill patients and associated with poor clinical outcomes. Some studies demonstrated the association of stress hyperglycemia and poor outcomes in acute MI. However, current results for the impact of stress hyperglycemia on mortality in acute MI who underwent PCI are insufficient.

Purpose

We aimed to evaluate the impact of stress hyperglycemia on clinical outcomes of patients with STEMI underwent primary PCI in large scale multi-center registry.

Methods

From 2007 to 2014, in 1,538 patients of the INTERSTELLAR (Incheon-Bucheon Cohort of Patients Undergoing Primary PCI for Acute ST-Elevation Myocardial Infarction) cohort, 997 patients without diabetes who underwent primary PCI for STEMI were retrospectively analyzed. We defined random glucose more than 200mg/dl at admission without diabetic history or results of HbA1C more than 6.5% as stress hyperglycemia. The primary endpoint was in-hospital all-cause death and the secondary endpoint was all-cause death within 1 year after index PCI.

Results

From 997 nondiabetic cohort population, 117 patients with stress hyperglycemia and 880 patients without stress hyperglycemia were enrolled. Baseline characteristics including age, sex, hypertension, hyperlipidemia, atrial fibrillation, left main disease, and multivessel disease were not significantly different between two groups. However, systolic blood pressure was lower (111.2±39.2 vs. 125.5±28.1, p<0.001) and hypoxic liver injury was frequent (31.0% vs. 20.1%, p=0.007) in stress hyperglycemia. In-hospital and 1-year all-cause mortality were higher in stress hyperglycemia (13.7% vs. 2.7%, p<0.001; 15.4% vs. 3.8%, p<0.001, respectively). However, there is no significant difference in post-discharge mortality rate. Stress hyperglycemia was a significant independent predictor of in-hospital death (adjusted OR: 5.67, 95% CI: 2.40–13.39; p<0.001). Hypotension (defined less than 90mmHg) and left ventricular dysfunction (defined less than 40% of LVEF on echocardiography) were significantly associated with stress hyperglycemia (adjusted OR: 5.72, 95% CI: 3.33–9.82; p<0.001; adjusted OR: 2.38, 95% CI: 1.49–3.82; p<0.001, respectively).

Landmark analysis of all-cause death

Conclusions

In nondiabetic patients who underwent primary PCI for STEMI, stress hyperglycemia is significantly associated with an increased in-hospital all-cause mortality but did not increase post-discharge mortality within 1 year.

A pipeline for rapidly generating genetically engineered mouse models of pancreatic cancer using in vivo CRISPR-Cas9-mediated somatic recombination

Genetically engineered mouse models (GEMMs) that recapitulate the major genetic drivers in pancreatic ductal adenocarcinoma (PDAC) have provided unprecedented insights into the pathogenesis of this lethal neoplasm. Nonetheless, generating an autochthonous model is an expensive, time consuming and labor intensive process, particularly when tissue specific expression or deletion of compound alleles are involved. In addition, many of the current PDAC GEMMs cause embryonic, pancreas-wide activation or loss of driver alleles, neither of which reflects the cognate human disease scenario. The advent of CRISPR/Cas9 based gene editing can potentially circumvent many of the aforementioned shortcomings of conventional breeding schema, but ensuring the efficiency of gene editing in vivo remains a challenge. Here we have developed a pipeline for generating PDAC GEMMs of complex genotypes with high efficiency using a single "workhorse" mouse strain expressing Cas9 in the adult pancreas under a p48 promoter. Using adeno-associated virus (AAV) mediated delivery of multiplexed guide RNAs (sgRNAs) to the adult murine pancreas of p48-Cre; LSL-Cas9 mice, we confirm our ability to express an oncogenic Kras G12D allele through homology-directed repair (HDR), in conjunction with CRISPR-induced disruption of cooperating alleles (Trp53, Lkb1 and Arid1A). The resulting GEMMs demonstrate a spectrum of precursor lesions (pancreatic intraepithelial neoplasia [PanIN] or Intraductal papillary mucinous neoplasm [IPMN] with eventual progression to PDAC. Next generation sequencing of the resulting murine PDAC confirms HDR of oncogenic KrasG12D allele at the endogenous locus, and insertion deletion ("indel") and frameshift mutations of targeted tumor suppressor alleles. By using a single "workhorse" mouse strain and optimal AAV serotype for in vivo gene editing with combination of driver alleles, we present a facile autochthonous platform for interrogation of the PDAC genome.

Reducing off target viral delivery in ovarian cancer gene therapy using a protease-activated AAV2 vector platform

Gene therapy is a promising strategy for treating metastatic epithelial ovarian cancer (EOC). However, efficient vector targeting to tumors is difficult and off-target effects can be severely detrimental. Most vector targeting approaches rely on surface receptors overexpressed on some subpopulation of cancer cells. Unfortunately, there is no universally expressed cell surface biomarker for tumor cells. As an alternative, we developed an adeno-associated virus (AAV) based "Provector" whose cellular transduction can be activated by extracellular proteases, such as matrix metalloproteinases (MMP) that are overexpressed in the tumor microenvironments of the most aggressive forms of EOC. In a non-tumor bearing mouse model, the Provector demonstrates efficient de-targeting of healthy tissues, especially the liver, where viral delivery is <1% of AAV2. In an orthotopic HeyA8 tumor model of EOC, the Provector maintains decreased off-target delivery in the liver and other tissues but with no loss in tumor delivery. Notably, approximately 10% of the injected Provector is still detected in the blood at 24 h while >99% of injected AAV2 has been cleared from the blood by 1 h. Furthermore, mouse serum raised against the Provector is 16-fold less able to neutralize Provector transduction compared to AAV2 serum neutralizing AAV2 transduction (1:200 vs 1:3200 serum dilution, respectively). Thus, the Provector appears to generate less neutralizing antibodies than AAV2. Importantly, serum against AAV2 does not neutralize the Provector as well as AAV2, suggesting that pre-existing antibodies against AAV2 would not negate the clinical application of Provectors. Taken together, we present an EOC gene delivery vector platform based on AAV with decreased off-target delivery without loss of on-target specificity, and greater immunological stealth over the traditional AAV2 gene delivery vector.

Protease-Activatable Adeno-Associated Virus Vector for Gene Delivery to Damaged Heart Tissue

Adeno-associated virus (AAV) has emerged as a promising gene delivery vector because of its non-pathogenicity, simple structure and genome, and low immunogenicity compared to other viruses. However, its adoption as a safe and effective delivery vector for certain diseases relies on altering its tropism to deliver transgenes to desired cell populations. To this end, we have developed a protease-activatable AAV vector, named provector, that responds to elevated extracellular protease activity commonly found in diseased tissue microenvironments. The AAV9-based provector is initially inactive, but then it can be switched on by matrix metalloproteinases (MMP)-2 and -9. Cryo-electron microscopy and image reconstruction reveal that the provector capsid is structurally similar to that of AAV9, with a flexible peptide insertion at the top of the 3-fold protrusions. In an in vivo model of myocardial infarction (MI), the provector is able to deliver transgenes site specifically to high-MMP-activity regions of the damaged heart, with concomitant decreased delivery to many off-target organs, including the liver. The AAV provector may be useful in the future for enhanced delivery of transgenes to sites of cardiac damage.

Longer Inactivating Sequence in Peptide Lock Improves Performance of Synthetic Protease-Activatable Adeno-Associated Virus

Adeno-associated viruses (AAVs) are promising gene therapy vectors but may exhibit off-target delivery due to broad tissue tropism. We recently developed a synthetic protease-activatable AAV vector, named provector, that transduces cells preferentially in environments rich in matrix metalloproteinases (MMPs) which are elevated in a variety of diseases, including various cancers and heart diseases. The provector displays peptide locks made up of MMP recognition sites flanking an inactivating sequence (IS) composed of four aspartic acid residues (D4). When present, the IS prevents AAV from binding cell receptors and no transduction occurs (OFF state). High levels of MMPs cleave the recognition sequences and release the IS from the capsid surface, restoring cell receptor binding (ON state). The AAV9 provector prototype is not optimal as it displays baseline OFF transduction at 5-10% of that of the wild-type capsid, which can lead to off-target delivery. We hypothesized that changes to the IS may decrease OFF state transduction. We created a provector panel with IS of lengths 0 (D0) to 10 (D10) aspartic acid residues and characterized this panel in vitro. Notably, we find that the D10 provector has an OFF transduction of less than 1% of wild-type capsid and an ON/OFF transduction ratio of 27, the best outcome achieved for any provector thus far. In summary, our results enable us to define new design rules for the provector platform, specifically that (1) the IS is necessary for provector locking and (2) increasing the number of aspartic acid residues in this sequence improves locking.

Physical, chemical, and synthetic virology: Reprogramming viruses as controllable nanodevices

The fields of physical, chemical, and synthetic virology work in partnership to reprogram viruses as controllable nanodevices. Physical virology provides the fundamental biophysical understanding of how virus capsids assemble, disassemble, display metastability, and assume various configurations. Chemical virology considers the virus capsid as a chemically addressable structure, providing chemical pathways to modify the capsid exterior, interior, and subunit interfaces. Synthetic virology takes an engineering approach, modifying the virus capsid through rational, combinatorial, and bioinformatics-driven design strategies. Advances in these three subfields of virology aim to develop virus-based materials and tools that can be applied to solve critical problems in biomedicine and biotechnology, including applications in gene therapy and drug delivery, diagnostics, and immunotherapy. Examples discussed include mammalian viruses, such as adeno-associated virus (AAV), plant viruses, such as cowpea mosaic virus (CPMV), and bacterial viruses, such as Qβ bacteriophage. Importantly, research efforts in physical, chemical, and synthetic virology have further unraveled the design principles foundational to the form and function of viruses. This article is categorized under: Diagnostic Tools > Diagnostic Nanodevices Biology-Inspired Nanomaterials > Protein and Virus-Based Structures.

Reverse transduction can improve efficiency of AAV vectors in transduction-resistant cells

Reverse transduction, also known as substrate-mediated gene delivery, is a strategy in which viral vectors are first coated onto a surface that subsequently comes into contact with mammalian cells. The cells internalize the surface-attached vectors, resulting in transgene expression. We hypothesized that forcing the interaction between cells and adeno-associated virus (AAV) vectors through a reverse transduction format would increase in vitro gene delivery efficiencies of the vectors in transduction-resistant cells. We tested this hypothesis by comparing the gene delivery efficiencies of three AAV serotypes using either standard or reverse transduction approaches. Our study reveals reverse transduction of AAV7 and AAV9 can significantly improve their delivery efficiencies. In contrast, AAV2 does not perform better under the reverse transduction format. Interestingly, increased vector uptake by cells does not provide a complete explanation for the increased transduction efficiency. Our findings offer a simple and practical method for improving transduction outcomes in vitro in cell types less permissive to a particular AAV vector.

Adeno-Associated Virus (AAV) Vectors: Rational Design Strategies for Capsid Engineering

Adeno-associated virus (AAV) consists of a simple genome, infects mammalian cells, displays nonpathogenicity in humans, and spans an array of serotypes and variants bearing distinct tissue tropisms. These attributes lend AAV tremendous promise as a gene delivery vector, further substantiated by its extensive testing in human clinical trials. Rational design approaches to capsid engineering leverage current scientific knowledge of AAV to further modulate, enhance and optimize the performance of the vectors. Capsid modification strategies include amino acid point mutations, peptide domain insertions, and chemical biology approaches. Through such efforts, insights regarding AAV capsid sequence-structure-function relationships can be learned. Developments over the last 5 years in rational design-based capsid engineering approaches will be presented and discussed.

Comprehensive genomic profiles of metastatic and relapsed salivary gland carcinomas are associated with tumor type and reveal new routes to targeted therapies

Background

Relapsed/metastatic salivary gland carcinomas (SGCs) have a wide diversity of histologic subtypes associated with variable clinical aggressiveness and response to local and systemic therapies. We queried whether comprehensive genomic profiling could define the tumor subtypes and uncover clinically relevant genomic alterations, revealing new routes to targeted therapies for patients with relapsed and metastatic disease.

Patients and methods

From a series of 85 686 clinical cases, DNA was extracted from 40 µm of formalin-fixed paraffin embedded (FFPE) sections for 623 consecutive SGC. CGP was carried out on hybridization-captured, adaptor ligation-based libraries (mean coverage depth, >500×) for up to 315 cancer-related genes. Tumor mutational burden was determined on 1.1 Mb of sequenced DNA. All classes of alterations, base substitutions, short insertions/deletions, copy number changes, and rearrangements/fusions were determined simultaneously.

Results

The clinically more indolent SGC including adenoid cystic carcinoma, acinic cell carcinoma, polymorphous low-grade adenocarcinoma, mammary analog secretory carcinoma, and epithelial-myoepithelial carcinomas have significantly fewer genomic alterations, TP53 mutations, and lower tumor mutational burden than the typically more aggressive SGCs including mucoepidermoid carcinoma, salivary duct carcinoma, adenocarcinoma, not otherwise specified, carcinoma NOS, and carcinoma ex pleomorphic adenoma. The more aggressive SGCs are commonly driven by ERBB2 PI3K pathway genomic alterations. Additional targetable GAs are frequently seen.

Conclusions

Genomic profiling of SGCs demonstrates important differences between traditionally indolent and aggressive cancers. These differences may provide therapeutic options in the future.

Reprogramming the Activatable Peptide Display Function of Adeno-Associated Virus Nanoparticles

We harnessed an intrinsic activatable peptide display behavior shared by several parvoviruses, including the adeno-associated virus (AAV), in order to design protein-based nanodevices that can carry out an exogenous functional output in response to stimulus detection. Specifically, we generated truncated viral capsid subunits that, when combined with native capsid components into mosaic capsids, can perform robust activatable peptide display. By modulating the ratio of subunits in the mosaic capsid, properties of the activatable peptide display function can be optimized. Interestingly, the truncated subunits can form homomeric capsids not observed in nature, but at the price of losing the ability to carry out activatable peptide display. Collectively, our results demonstrate the importance of capsid mosaicism when activatable peptide display is desired and help explain why the wild-type AAV capsid exists as a mosaic of different subunits. This proof-of-concept study illustrates a strategy for reprogramming a particular conformational output behavior of AAV in pursuit of the long-term vision of creating stimulus-responsive nanodevices.

Abstract P3-05-03: Metaplastic breast cancers: Genomic profile, mutational burden and TILs

Background: Metaplastic breast cancers (MPBC) are rare, typically triple negative aggressive tumors composed of both, adenocarcinoma and metaplastic elements. Recent evidence that TNBC and MPBC can respond vigorously to immune checkpoint inhibitor therapy (Adams et al, ASCO 2017 and npj Breast Cancer 2017) has prompted the following comprehensive genomic profiling (CGP) and histopathologic assessment of tumor infiltrating lymphocytes (TIL) designed to uncover potential biomarkers of immunotherapy response for MPBC, including mutational burden, Microsatellite Instability (MSI) status and gene amplification of 9p21.4 (or CD274, which includes the PD-L1 locus).

Methods: 12,214 locally aggressive, relapsed and metastatic breast malignancies (mBM) were subjected to CGP using DNA extracted from 40 µm of FFPE sections and adaptor ligation-based libraries to a mean coverage depth &gt;650X for up to 315 cancer-related genes. The results were analyzed for all classes of genomic alterations (GA) including base substitutions, insertions and deletions, select rearrangements, and copy number changes. Tumor mutational burden (TMB) was determined on 1.1 Mbp of sequenced DNA. MSI status was determined by an algorithm based on the sequencing results. TIL were assessed on archived H&E tumor sections and enumerated per guidelines established by the TIL Working Group (Salgado, Ann Oncol 2015) in a subset of MPBC with the highest TMB and compared with low TMBC cases.

Results: 165 of mBM cases were MPBC (1.4%) and are included in this study. All patients were female with a median age of 60 (range 24-86). 165 of the MPBC cases (100%) harbored a wide variety of GA involving more than 100 individual genes. The most common GA were identified in TP53 (65%), followed by PIK3CA (37%). No cases of MSI hi status (0/103) and only one case with amplification of 9p21.4 (1/165, 0.6%) were observed. Most MPBC had a low mutational burden, with a median TMB of 2.7 mutations/Mb (range 0-39.6). Only 11/165 tumors (6.7%) were found to have a TMB over 10 mutations/Mb, including 3 cases (1.8%) with TMB &gt;20. Tumor sections were available for TIL review from 9/11 cases with highest TMB, as well as 11 control cases with lowest TMB. TIL were more frequently observed in high versus low TMB MPBC, with median TIL percentage of 40 and 20 (range 10-80 and range 10-60), respectively, although this difference was not statistically significant (Wilcoxon rank-sum test, p=0.15).

Conclusions: Genomic profiling in the largest cohort of MPBC reported to date confirms that MPBC is enriched for TP53 and PIK3CA mutations and many tumors harbor targetable GA. The frequently observed tumoral PD-L1 expression in MPBC is not based on gene amplification as amplification of 9p21.4 is rare. Most tumors had a low mutation burden, and no significant association of TIL with TMB was observed, suggesting additional processes underlying MPBC immunogenicity.

Citation Format: Taff J, Suh J, Singh B, Denkert C, Troxel AB, Ross JS, Adams S. Metaplastic breast cancers: Genomic profile, mutational burden and TILs [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 P3-05-03.

Abstract P5-21-20: Integrating comprehensive genomic profiling with treatment decisions – Experience gained while treating 139 advanced breast carcinomas

Background: Comprehensive Genomic Profiling (CGP) using next-generation sequencing (NGS) technology can provide insight into potentially clinically relevant genomic alterations (CRGA) within a patient's breast cancer. For example, HER2 amplification status and targetable short variants (SV), acquired ESR1 or BRCA1/2 resistance mutations, and the presence of targetable alterations in the PI3K kinase. We retrospectively reviewed CGP results and subsequent outcomes at one cancer center to illustrate the experience of using molecular subtyping to inform treatment decisions.

Methods: DNA extracted from FFPE tumor tissue or blood samples obtained during routine clinical care for patients (n=139) with predominantly relapsed, refractory or metastatic breast cancer was analyzed by hybrid-capture, NGS for all classes of GA: 1. base substitutions, 2. insertion and deletions, 3. rearrangements, and 4. copy number changes. Treatment decisions based on comprehensive genomic profiles were captured retrospectively. Tumor mutational burden (TMB), scored as mutations (mut)/Mb, was calculated on 0.8-1.2 Mb of sequenced DNA. Alterations affecting the ERBB family included amplification of or oncogenic mutations in ERBB2 (HER2), ERBB3, and EGFR.

Results: From Jan 2013 to May 2017, FFPE tissue samples for 136 patients with advanced breast cancer were analyzed by CGP and 3 additional patients had circulating tumor DNA analyzed for alterations; 11 patients received profiling on multiple biopsies. Tumors analyzed were carcinomas (Ca) NOS (n=84), invasive ductal Ca (n=46), invasive lobular Ca (n=7), a neuroendocrine Ca, and a phyllodes tumor. In total, 118/139 (84.9%) samples harbored CRGA in a targetable pathway: PI3K/MTOR (n=67; 48.2%), CDK cell-cycle (n=40; 28.8%), ERBB family (n=24; 17.3%), FGFR (n=24; 17.3%), ESR1 (n=16; 11.5%), homologous repair (HRD)( n=14; 10.1%), and RAS/RAF/MEK (n=11; 7.9%). Targetable alterations in other cancer-related kinases were found in 10 (7.2%) samples and 10 (7.2%) samples were TMB high (≥20 mut/Mb) or had CD274 (PD-L1) amplification. There were 3 patients (2.1%) with HER2 short variants detected in the absence of ERBB2 amplification; these patients may respond to HER2-targeted therapies but would be HER2-negative by IHC. Many samples had alterations in ≥1 pathway, and overlap is particularly high for the CDK and FGFR pathways (12 samples). Alterations in pathways targeted by MTOR inhibitors, HER2-targeted therapies, or the CDK inhibitors were found in 93/136 (66.9%) tumors. Evaluation of outcomes for these 139 patients is ongoing and will be presented.

Conclusions: Genomic profiling of breast carcinomas, using either tissue or liquid biopsies, provides potentially actionable information to guide treatment decisions. Overall, 84.9% of patient samples harbored oncogenic alterations in a targetable pathway, with two-thirds of tumors having alterations in pathways targeted by therapies with FDA approval for breast cancer and 7.2% of patients having high levels of TMB or amplification of PD-L1, suggesting that checkpoint inhibitors may be relevant options.

Citation Format: Mahtani R, Gay LM, Chung J, Hartmaier R, Sokol E, Elvin JA, Daniel S, Ramkissoon S, Severson E, Suh J, Vergilio J-A, Stephens PJ, Ross JS. Integrating comprehensive genomic profiling with treatment decisions – Experience gained while treating 139 advanced breast carcinomas [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 P5-21-20.

Abstract PD8-01: CDH1 mutated classic and pleomorphic invasive lobular breast carcinomas differ in genomic signatures and opportunities for targeted and immunotherapies

Background: Typically defined by negative IHC staining for E-cadherin, classic (CILC) and pleomorphic (PILC) are often combined as a single breast cancer subtype. We queried whether patients with relapsed metastatic disease, mCILC and mPILC, would harbor contrasting genomic alterations (GA)and that molecular information could further differentiate the 2 tumor types and thereby influence therapy selection.

Methods: DNA was extracted from 40 µm of FFPE sections of 10,784 invasive breast carcinomas. 454 (4%) CDH1 mutated mILC were selected including 428 classic mCILC (94%) and 26 mPLIC (6%) subtypes. Comprehensive genomic profiling (CGP) was performed on hybridization-captured, adaptor ligation-based libraries to a mean coverage depth &gt;600X for up to 315 cancer-related genes. Tumor mutational burden (TMB) was determined on 1.1 Mbp of sequenced DNA.

Results: mCILC and mPILC patients featured a median age of 63 years (Table). Slide based ER+ status and HER2+ status was significantly different in both groups (P&lt;0.0001). The frequency of base substitutions in ESR1 was significantly higher in mCILC, and this difference was also significantly higher in mCILC metastasis biopsies exposed to hormonal therapy than in pre-treatment primary tumors (P&lt;0.0001). ERBB2 (HER2) GA (amp + non-amp) detected by CGP were higher in mPILC than mCILC in both pre-and post-treatment samples (P&lt;0.0001 for both). The ERBB2 GA frequency was nearly twice as high after hormonal therapy in both mCILC and mPILC. ESR1 and ERBB2 GA were mutually exclusive overall and especially in the mCILC group. PIK3CA GA were the most frequent GA in both mCILC and mPILC. TP53 GA were significantly more frequent in mPILC than mCILC. At 19%, the frequency of TMB &gt; 15 mutations/MB in mPILC was more than twice as frequent than in mCILC (P=0.046). All (100%) of both the CILC and PILC groups were negative for mis-match repair deficiency or MSI high status. mCILC and mPILC patients with post primary therapy associated ESR1 and ERBB2 GA responding to targeted and immunotherapies will be presented.

Contrasting Clinical and Genomic Features of CILC and PILC Classic CILC (428 cases)Pleomorphic PILC (26 cases)Median Age6363*ER+98%74%*HER2 IHC/FISH+12 (3%)6 (22%)ESR1 GA Primary Pre-Rx6%0%ESR1 GA Metastatic Post-Rx17%0%ERBB2 GA Primary Pre-Rx7%18%ERBB2 GA Metastatic Post-Rx12%34%Other Significant GAPIK3CA (55%), CCND1 (21%), TP53 (17%), ARID1A, AKT3, MDM4, PTEN (all 11%)PIK3CA (58%), TP53 (30%), AKT1 22%), FGFR4, CCND1, PTEN (all 17%)TMB median (mut/Mb)2.73.6TMB &gt; 15%8%19%*when clinical status available

Conclusions: CGP of mCILC and mPILC reveals significant differences in the panorama of GA both in pre-treatment primary and metastatic disease lesions especially in therapy-impacting GA in ESR1 and ERBB2. mCILC is more often driven by ESR1 GA and mPILC by ERBB2 GA. Although both mCILC and mPILC feature subsets of tumors with high TMB, this is more frequent for mPILC likely indicating different potentials for immunotherapies to benefit these patients.

Citation Format: Ross JS, Chung J, Elvin JE, Vergilio J-A, Ramkissoon S, Suh J, Severson E, Daniel S, Frampton GM, Fabrizio D, Hartmaier RJ, Albacker LA, Ali SM, Schrock AB, Miller VA, Stephens PJ, Gay LM. CDH1 mutated classic and pleomorphic invasive lobular breast carcinomas differ in genomic signatures and opportunities for targeted and immunotherapies [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 PD8-01.

Stimulus-responsive viral vectors for controlled delivery of therapeutics

Virus-based therapies have gained momentum as the next generation of treatments for a variety of serious diseases. In order to make these therapies more controllable, stimulus-responsive viral vectors capable of sensing and responding to specific environmental inputs are currently being developed. A number of viruses naturally respond to endogenous stimuli, such as pH, redox, and proteases, which are present at different concentrations in diseases and at different organ and organelle sites. Additionally, rather than relying on natural viral properties, efforts are underway to engineer viruses to respond to endogenous stimuli in new ways as well as to exogenous stimuli, such as temperature, magnetic field, and optical light. Viruses with stimulus-responsive capabilities, either nature-evolved or human-engineered, will be reviewed to capture the current state of the field. Stimulus-responsive viral vector design considerations as well as gaps in current research efforts will be identified.