Human-in-the-loop assisted de novo molecular design

A de novo molecular design workflow can be used together with technologies such as reinforcement learning to navigate the chemical space. A bottleneck in the workflow that remains to be solved is how to integrate human feedback in the exploration of the chemical space to optimize molecules. A human drug designer still needs to design the goal, expressed as a scoring function for the molecules that captures the designer's implicit knowledge about the optimization task. Little support for this task exists and, consequently, a chemist usually resorts to iteratively building the objective function of multi-parameter optimization (MPO) in de novo design. We propose a principled approach to use human-in-the-loop machine learning to help the chemist to adapt the MPO scoring function to better match their goal. An advantage is that the method can learn the scoring function directly from the user's feedback while they browse the output of the molecule generator, instead of the current manual tuning of the scoring function with trial and error. The proposed method uses a probabilistic model that captures the user's idea and uncertainty about the scoring function, and it uses active learning to interact with the user. We present two case studies for this: In the first use-case, the parameters of an MPO are learned, and in the second use-case a non-parametric component of the scoring function to capture human domain knowledge is developed. The results show the effectiveness of the methods in two simulated example cases with an oracle, achieving significant improvement in less than 200 feedback queries, for the goals of a high QED score and identifying potent molecules for the DRD2 receptor, respectively. We further demonstrate the performance gains with a medicinal chemist interacting with the system.

DockStream: a docking wrapper to enhance de novo molecular design

Recently, we have released the de novo design platform REINVENT in version 2.0. This improved and extended iteration supports far more features and scoring function components, which allows bespoke and tailor-made protocols to maximize impact in small molecule drug discovery projects. A major obstacle of generative models is producing active compounds, in which predictive (QSAR) models have been applied to enrich target activity. However, QSAR models are inherently limited by their applicability domains. To overcome these limitations, we introduce a structure-based scoring component for REINVENT. DockStream is a flexible, stand-alone molecular docking wrapper that provides access to a collection of ligand embedders and docking backends. Using the benchmarking and analysis workflow provided in DockStream, execution and subsequent analysis of a variety of docking configurations can be automated. Docking algorithms vary greatly in performance depending on the target and the benchmarking and analysis workflow provides a streamlined solution to identifying productive docking configurations. We show that an informative docking configuration can inform the REINVENT agent to optimize towards improving docking scores using public data. With docking activated, REINVENT is able to retain key interactions in the binding site, discard molecules which do not fit the binding cavity, harness unused (sub-)pockets, and improve overall performance in the scaffold-hopping scenario. The code is freely available at https://github.com/MolecularAI/DockStream .

Discovery of Novel UDP-N-Acetylglucosamine Acyltransferase (LpxA) Inhibitors with Activity against Pseudomonas aeruginosa

This study describes a novel series of UDP-N-acetylglucosamine acyltransferase (LpxA) inhibitors that was identified through affinity-mediated selection from a DNA-encoded compound library. The original hit was a selective inhibitor of Pseudomonas aeruginosa LpxA with no activity against Escherichia coli LpxA. The biochemical potency of the series was optimized through an X-ray crystallography-supported medicinal chemistry program, resulting in compounds with nanomolar activity against P. aeruginosa LpxA (best half-maximal inhibitory concentration (IC₅₀) <5 nM) and cellular activity against P. aeruginosa (best minimal inhibitory concentration (MIC) of 4 μg/mL). Lack of activity against E. coli was maintained (IC₅₀ > 20 μM and MIC > 128 μg/mL). The mode of action of analogues was confirmed through genetic analyses. As expected, compounds were active against multidrug-resistant isolates. Further optimization of pharmacokinetics is needed before efficacy studies in mouse infection models can be attempted. To our knowledge, this is the first reported LpxA inhibitor series with selective activity against P. aeruginosa.

LibINVENT: Reaction-based Generative Scaffold Decoration for in Silico Library Design

Because of the strong relationship between the desired molecular activity and its structural core, the screening of focused, core-sharing chemical libraries is a key step in lead optimization. Despite the plethora of current research focused on in silico methods for molecule generation, to our knowledge, no tool capable of designing such libraries has been proposed. In this work, we present a novel tool for de novo drug design called LibINVENT. It is capable of rapidly proposing chemical libraries of compounds sharing the same core while maximizing a range of desirable properties. To further help the process of designing focused libraries, the user can list specific chemical reactions that can be used for the library creation. LibINVENT is therefore a flexible tool for generating virtual chemical libraries for lead optimization in a broad range of scenarios. Additionally, the shared core ensures that the compounds in the library are similar, possess desirable properties, and can also be synthesized under the same or similar conditions. The LibINVENT code is freely available in our public repository at https://github.com/MolecularAI/Lib-INVENT. The code necessary for data preprocessing is further available at: https://github.com/MolecularAI/Lib-INVENT-dataset.

De novo design with deep generative models based on 3D similarity scoring

We have demonstrated the utility of a 3D shape and pharmacophore similarity scoring component in molecular design with a deep generative model trained with reinforcement learning. Using Dopamine receptor type 2 (DRD2) as an example and its antagonist haloperidol 1 as a starting point in a ligand based design context, we have shown in a retrospective study that a 3D similarity enabled generative model can discover new leads in the absence of any other information. It can be efficiently used for scaffold hopping and generation of novel series. 3D similarity based models were compared against 2D QSAR based, indicating a significant degree of orthogonality of the generated outputs and with the former having a more diverse output. In addition, when the two scoring components are combined together for training of the generative model, it results in more efficient exploration of desirable chemical space compared to the individual components.

Interlimb Asymmetries: The Need for an Individual Approach to Data Analysis

ABSTRACT

Bishop, C, Lake, J, Loturco, I, Papadopoulos, K, Turner, A, and Read, P. Interlimb asymmetries: the need for an individual approach to data analysis. J Strength Cond Res 35(3): 695-701, 2021-It has been shown that the magnitude of interlimb asymmetries varies depending on the test selected; however, literature relating to whether asymmetries always favor the same limb is scarce. The aim of this study was to determine whether interlimb asymmetries always favored the same side for common metrics across unilateral strength and jumping-based tests. Twenty-eight recreational sport athletes performed unilateral isometric squats, single-leg countermovement jumps, and single-leg broad jumps with asymmetries in peak force compared across all tests, and eccentric and concentric impulse asymmetries compared between jumps. Mean asymmetries for all tests were low (≤-5.3%), and all interlimb differences for jump tests favored the left limb, whereas asymmetries during the isometric squat favored the right limb. Despite the low mean asymmetry values, individual data highlighted substantially greater differences. Levels of agreement for asymmetries were computed through the Kappa coefficient and ranged from slight to substantial (<0.01-0.79), although concentric impulse asymmetries for jump tests was the only comparison with result in substantial levels of agreement. With asymmetries rarely being present on the same side across tests, these results show that a more individual approach to reporting asymmetries is required, which should help practitioners when designing targeted training interventions for their reduction.

Global Constructive Work predicts left ventricular reverse remodeling one year after MitraClip implantation in patients with functional mitral regurgitation

Background

Percutaneous edge-to-edge mitral valve repair (PMVr) has recently been identified as an effective method for treating patients with functional mitral regurgitation. However, it is still unknown which patients will benefit by showing clinical improvement and left ventricular reverse remodeling.

Purpose

The purpose of this study is to analyze novel echocardiographic markers and identify markers of LV reverse remodeling after MitraClip implantation.

Methods

We retrospectively analyzed 58 high surgical risk (logistic EuroSCORE 23±15%) consecutive patients (aged 72±10yrs) with functional moderate-to-severe and severe mitral regurgitation (EROA 29±14mm2) and reduced LV contractility (EF 32±8%, GLS −8.6±3.7%). At baseline and 1-year after PMVr we assessed echocardiographic parameters such as MR severity, EF, Global Longitudinal Strain (GLS), Global Work Index (GWI), Global Constructive Work (GCW), Global Wasted Work (GWW) and Global Work Efficiency (GWE).

Results

In patients with MitraClip implantation there was a significant reduction of MR (3.7±0.4 vs 1.7±0.8, p&lt;0.001) one year after the intervention. The EF and GLS did not improve after the implantation (32±8 vs 33±10%, p=0.178 & −8.6±3.7 vs −8.6±3.7%, p=0.922 respectively) but Global Work Index (GWI) and Global Constructive Work (GCW) demonstrated significant improvement (607±282 vs 650±260mmHg%, p=0.04 & 854±288 vs 949±325mmHg%, p&lt;0.001 respectively). The baseline EF, GLS, GWI, GCW and EROA were the factors that were significantly associated with more than 20% reduction of LVEDV one year after intervention (p&lt;0.02 for all). To be more specific, left ventricles with better performance and contractility combined with worse mitral regurgitation were the ones that responded better. Further, baseline GCW was the only factor that was significantly associated with reduction of the LVESV. A ROC curve analysis identified a cut-off value of 846mmHg% (AUC 0.759, 95% CI: 0.588–0.930; p=0.007) to be associated with 10% reduction of LVESV, with a sensitivity and specificity of 79% and 74% respectively.

Conclusions

Transcatheter edge-to-edge repair is an effective method for treating patients with FMR and improves LV performance one year after intervention. A preserved baseline GCW seems to be a good predictor of LV reverse remodeling after MitraClip implantation.

Funding Acknowledgement

Type of funding source: None

REINVENT 2.0: An AI Tool for De Novo Drug Design

In the past few years, we have witnessed a renaissance of the field of molecular de novo drug design. The advancements in deep learning and artificial intelligence (AI) have triggered an avalanche of ideas on how to translate such techniques to a variety of domains including the field of drug design. A range of architectures have been devised to find the optimal way of generating chemical compounds by using either graph- or string (SMILES)-based representations. With this application note, we aim to offer the community a production-ready tool for de novo design, called REINVENT. It can be effectively applied on drug discovery projects that are striving to resolve either exploration or exploitation problems while navigating the chemical space. It can facilitate the idea generation process by bringing to the researcher's attention the most promising compounds. REINVENT's code is publicly available at https://github.com/MolecularAI/Reinvent.

P1757 Novel echocardiographic markers as predictors for left ventricular reverse remodeling one year after edge-to-edge mitral valve repair in patients with functional mitral regurgitation

Background

Percutaneous edge-to-edge mitral valve repair (PMVR) is a safe treatment option for high surgical risk patients with severe functional mitral regurgitation (FMR). Recent trials have proven this method’s efficiency but novel echocardiographic markers such as deformation imaging have never been analyzed in this subgroup of patients.

Purpose

The purpose of this study is to analyze novel echocardiographic parameters in patients treated for FMR and identify predictors of response in patients undergoing PMVR.

Methods

We retrospectively analyzed 79 consecutive high surgical risk patients (logistic EuroSCORE 21.8 ± 15.2%), with ischemic or dilated cardiomyopathy, reduced EF (31.0 ± 8.5%) and severe functional MR (FMR). Effective regurgitant orifice area (EROA) was measured at 28.8 ± 15.1mm2 and regurgitant volume (RV) at 41.7 ± 18.3ml. At baseline and 1-year after PMVR or optimal medical treatment (OMT) we assessed echocardiographic parameters such as LV global longitudinal strain (LVGLS) and peak left atrial longitudinal strain (PALS), LV end-systolic and end-diastolic volumes (LVESV, LVEDV), LA volume, MR severity along with BNP levels, NYHA class and 6 minute walking distance (6MWT).

Results

One year after PMVR there was a significant reduction of MR (3.7 ± 0.4 vs 1.7 ± 0.8) and BNP levels (980 ± 1027pg/ml vs 420 ± 338pg/ml, p = 0.005), improvement of NYHA class (3.20 ± 0.55 to 2.0 ± 0.6, P &lt; 0.05) and increase of 6MWD (240 ± 137 to 298 ± 139m, P &lt; 0.01). LA volume and LVEDV were reduced (141 ± 79ml to 114 ± 74ml and 221 ± 74 to 193 ± 62ml respectively) (P &lt; 0.01 for all comparisons). On the other hand, patients treated with OMT didn’t have any change of their MR (3.4 ± 0.5 vs 3.4 ± 0.9), BNP levels (601 ± 652 vs 610 ± 748) or NYHA class status (2.6 ± 0.6 vs 2.4 ± 0.6). Additionally, LA and LV volumes were approximately the same (134 ± 69 vs 141 ± 61ml and 222 ± 64 vs 222 ± 56ml respectively) (p &lt; 0.05 for all comparisons). Baseline LVGLS slightly increased post intervention (-8.5 ± 4.1% vs -9.1 ± 3.7%, r = 0.76, P &lt; 0.01), and was associated with the absolute (r=-0.46, p = 0.01) and percentage difference in LVEDV (r= -0.61, P &lt; 0.01). ROC curve analysis identified a cut-off value for GLS of -7.45% (AUC 0.815, 95% CI: 0.647-0.983; p = 0.007) associated with more than 15% LV reverse remodeling, with a sensitivity and specificity of 71% and 75% respectively.

Conclusions

Edge-to-edge repair is a safe and effective method for treating patients with functional MR and has a positive clinical impact in patients at one year follow up. A preserved LVGLS seems to be a good predictor of LV reverse modeling post intervention.

P1758 Global left ventricular myocardial work efficiency as a prognostic marker for clinical responders one year after edge-to-edge mitral valve repair in patients with functional mitral regurgitation

Background

Percutaneous edge-to-edge mitral valve repair (PMVR) has been proven to be effective for treating patients with functional MR (FMR). However it remains to be answered which patients will benefit more from this method. Novel echocardiographic markers like myocardial work efficiency can be quantified non-invasively and have never been analyzed in this subgroup of patients before.

Purpose

The purpose of this study is to analyze the myocardial work efficiency in patients treated with PMVR for FMR and identify predictors of clinical response.

Methods

We retrospectively analyzed 22 high surgical risk (logistic EuroSCORE 28.9 ± 18.2%) consecutive patients (aged 72 ± 8yrs) with functional moderate-to-severe and severe mitral regurgitation (EROA 28.6 ± 14.6mm2, RV 41.7 ± 15.8ml) and reduced LV contractility (EF 32.7 ± 7.5%, GLS -8.8 ± 3.4%). At baseline and 1-year after PMVR or optimal medical treatment (OMT) we assessed echocardiographic parameters such as MR severity, Global Work Index (GWI), Global Constructive Work (GCW), Global Wasted Work (GWW) and Global Work Efficiency (GWE), along with BNP levels and NYHA class status.

Results

One year after PMVR there was a significant reduction of MR (3.6 ± 0.5 vs 1.8 ± 0.8, p = 0.009) and BNP levels (901 ± 610pg/ml vs 479 ± 385pg/ml, p &lt; 0.001) and significant improvement of NYHA class status (3.0 ± 0.6 to 2.2 ± 0.4, p &lt; 0.001). On the other hand, patients treated with OMT didn’t have any significant change of their MR (3.6 ± 0.5 vs 3.3 ± 1.0), BNP levels (296 ± 114 vs 241 ± 183pg/ml) or NYHA class status (2.6 ± 0.5 vs 2.4 ± 0.5). In device group, there was a preservation of GWI (572 ± 290 vs 609 ± 299mmHg%) and GCW (757 ± 310 vs 789 ± 316mmHg%) and non significant change of GWW and GWE (140 ± 70 vs 150 ± 73mmHg% and 79 ± 9 vs 79 ± 10% respectively, p &lt; 0.05 for all comparisons). On the other hand in medical treatment group there was a significant impairment of GWI (635 ± 263 vs 564 ± 267mmHg%, p = 0.08) and GWE (83 ± 9 vs 76 ± 11%, p = 0.03) and significant increase of GWW (123 ± 90 vs 162 ± 74mmHg%, p &lt; 0.001). Further, baseline GCW was reversely associated with the difference in BNP (r=-0.559, p = 0.038), NYHA class (r=-0.501, p = 0.06) and 6MWT (r=-0.577, p = 0.08) after PMVR, meaning that patients with worse energetics will respond better.

Conclusions

PMVR is an effective method for treating patients with FMR and preserves myocardial work index after one year of FU in contrast to medically treated patients in whom deterioration is observed.

P1560 Acute changes of mitral annular dimensions after transcatheter egde-to-edge repair: an indirect annuloplasty method?

Background

Percutaneous edge-to-edge mitral valve repair (PMVR) is a safe and alternative method for treating high-risk patients with severe mitral regurgitation (DMR or FMR). This transcatheter treatment aims at reducing the MR with a so-called "Alfieri stitch" method. However the impact on mitral annular dimensions after the device implantation is not well defined. The purpose of this study is to recognize the acute changes of mitral annular dimensions after transcatheter edge-to-edge repair.

Methods

We retrospectively analyzed 20 consecutive patients (aged 74 ± 10yrs) with degenerative or functional moderate-to-severe and severe mitral regurgitation (EROA 40.8 ± 20.5mm2, RV 52.6 ± 17.5ml) and reduced ejection fraction (EF 36.9 ± 15.4%). These patients were at high surgical risk or even inoperable in certain cases (logistic EuroSCORE 28.9 ± 18.2%) and evaluated by a heart team as candidates for transcatheter repair. All intraoperative transoesophageal echo studies were post processed with EchoPac v.203 or QLAB 9.0. 3D views of the mitral valve before and after the implantation of the device were analyzed with 4D AutoMVQ (GE) or MVQ (Phillips) software.

Results

PMVR was effective in treating the MR at the end of the operation (from 3.8 ± 0.4 to 1.3 ± 0.5 after the implantation, p &lt; 0.05) in all patients. There was a significant reduction of the annulus area (from 12.25 ± 3.0cm2 to 10.18 ± 2.88cm2, p &lt; 0.001) and circumference (from 13.23 ± 1.4cm to 12.18 ± 1.57cm, p &lt; 0.001), in both DMR and FMR cases. The percentage reduction of annulus area and circumference after PMVR was 17.3 ± 0.8% and 8 ± 5% respectively and the number of the clips used for that purpose were 1.55 ± 0.6. Additionally, edge-to-edge repair significantly reduced the anterior-posterior diameter (from 3.49 ± 0.56cm to 3.02 ± 0.55cm, r = 0.86, p &lt; 0.001) and the posteromedial-anterolateral diameter (from 4.15 ± 0.58cm to 3.88 ± 0.60cm, r = 0.9, p &lt; 0.001). The number of the clips used did not play an important role in the percentage difference of the annulus dimensions (20% reduction with one clip vs 14.3 ± 7.6% with two or more, p &lt; 0.05) and one possible explanation could be that patients receiving one clip had smaller annulus area comparing to the patients receiving two or more (11.2 ± 2.9mm2 vs 13.3 ± 2.7mm2 respectively, p &lt; 0.05).

Conclusions

Transcatheter edge-to-edge repair is effective in treating MR in patients with DMR and FMR and has a direct impact on mitral annular dimensions acutely after the implantation.

P301Preserved global longitudinal strain predicts left ventricular reverse remodeling one year after edge-to-edge mitral valve repair in functional mitral regurgitation

Background

Percutaneous edge-to-edge mitral valve repair (PMVR) has emerged as an effective treatment modality for high surgical risk patients with severe functional mitral regurgitation (FMR). Novel echocardiographic parameters, such as deformation imaging and their predictive significance have not been analyzed in this group of patients.

Purpose

The purpose of this study is to identify echocardiographic predictors of response in patients with FMR undergoing PMVR.

Methods

We retrospectively analyzed 44 consecutive patients with ischemic or dilated cardiomyopathy, reduced ejection fraction and severe functional MR (FMR), aged 71±9 years, 71% males, LVEF 30.9±8.7%, mitral valve effective regurgitant orifice area (EROA)>20mm2, regurgitant volume (RV) >30ml and logistic EuroSCORE 22±14.7%. At baseline and 1-year after PMVR we assessed echocardiographic parameters such as LV longitudinal strain (LVGLS) and peak left atrial longitudinal strain (PALS) using speckle tracking echocardiography, LV end-systolic and end-diastolic volumes (LVESV, LVEDV), LA volume, MR severity by Doppler echocardiography along with BNP levels, NYHA class and 6 minute walking distance.

Results

One year after edge-to-edge repair there was a significant reduction of MR (74.2% had mild to moderate MR, 22.6% moderate-to-severe MR and 3.2% severe MR) and BNP levels (933±943pg/ml to 669±824pg/ml), improvement of NYHA class (3.11±0.55 to 2.0±0.6, P<0.05) and increase of the 6 minute walking distance (251±141 to 296±148m, P<0.05). LA volume was reduced (132.5±62.1ml to 115.2±57.7ml) and PALS was improved (6.89±3.47 to 7.94±5.27) (P<0.05 for all comparisons). Baseline LVGLS did not change significantly post intervention (−8.8±4.1 vs. −8.8±3.9, P=0.7) but the baseline value predicted the percentage difference in LVEDV (r=−0.61, P<0.01), LVESV (r=−0.47, P=0.03), BNP (r=0.45, P=0.04) and NYHA class (r=0.63, P<0.01). The best reverse LV remodeling was found in patients with GLS better than −10% and the trend was that the better the GLS the greater the LVEDV and LVESV reduction post-intervention. Additionally, patients with GLS between −10% and −5% had the largest improvement in BNP (P<0.05) and NYHA class (P=0.005).

Conclusions

Edge-to-edge repair is effective in reducing MR in patients with severe functional MR and has a positive impact in patients' clinical status at one year follow up. A preserved LVGLS seems to be a good predictor of reverse modeling and clinical improvement post intervention.

Ferrite based antennae for launching Alfvén waves

Whistler and Alfvén waves are known to scatter mirror-trapped electrons and protons into the loss cone of the earth's dipole magnetic field. An array of satellites with properly phased antennas can be used to artificially reduce the flux of energetic particles from regions where their flux has been naturally or artificially pumped. In any space based system, the power required to drive antennas is at a premium. We present here experimental evidence that the efficiency of an antenna can be greatly enhanced with the use of ferrite cores with high relative magnetic permeability μ. Ferrite-based antennas were constructed to launch Alfvén waves in a magnetized plasma. The wave magnetic field of shear Alfvén waves launched with a ferrite core was by the magnetization factor μ larger than that of a similar antenna without a ferrite. Combining multiple ferrite antennas allowed control of the injected perpendicular wavelength. This novel technique can be used to efficiently launch low frequency waves with amplitude above the threshold required for nonlinear triggering.

TAVR facilitated by high-pressure balloon post-dilatation to fracture the ring of the small dysfunctional aortic Mosaic bioprosthesis

Treatment of a failing aortic bioprosthesis by transcatheter valve-in-valve (ViV) therapy has become an alternative to redo surgery. However, the ViV technique may be less effective in small surgical valves because of patient/prosthesis mismatch (PPM). Here we will discuss the bioprosthetic valve fracture/remodelling (BVF) procedure and the most important issues regarding this promising new technique.

Acute and chronic effects of foam rolling vs eccentric exercise on ROM and force output of the plantar flexors

Foam rolling and eccentric exercise interventions have been demonstrated to improve range of motion (ROM). However, these two modalities have not been directly compared. Twenty-three academy soccer players (age: 18 ± 1; height: 1.74 ± 0.08 m; body mass: 69.3 ± 7.5 kg) were randomly allocated to either a foam rolling (FR) or eccentric exercise intervention designed to improve dorsiflexion ROM. Participants performed the intervention daily for a duration of four weeks. Measurements of dorsiflexion ROM, isometric plantar flexion torque and drop jump reactive strength index were taken at baseline (pre-intervention) and at three subsequent time-points (30-min post, 24-hours post and 4-weeks post). A significant time x group interaction effect was observed for dorsiflexion (P = 0.036), but not for torque or reactive strength index. For dorsiflexion, there was a significant increase in both acute (30-min; P < 0.001) and chronic (4-week; P < 0.001) ROM for the eccentric group, whilst FR exhibited only an acute improvement (P < 0.001). Eccentric training would appear a more efficacious modality than foam rolling for improving dorsiflexion ROM in elite academy soccer players.

The Predictive Value of the Syntax Score in Patients With Chronic Coronary Artery Disease Undergoing Percutaneous Coronary Intervention or Coronary Artery Bypass Grafting: A Pilot Study

Objectives:

To evaluate the usefulness of the SYNTAX score (SS) in predicting 1-year clinical outcomes in a population of patients with chronic coronary artery disease (CAD) undergoing percutaneous coronary intervention (PCI) or coronary artery bypass grafting (CABG).

Background:

Despite the proven prognostic value of the SS in patients with multivessel and/or left main (LM) CAD, its usefulness in other patient subsets remains uncertain.

Methods:

This was a prospective single centre cohort study conducted from September 2012 to November 2014 at the Nicosia General Hospital, Cyprus. Patients (n=140; 94% men and 6% women) with chronic CAD undergoing revascularization with either PCI or CABG were evaluated.

Results:

At 1-year, angina occurred in 20 patients (14.3%), myocardial infarction (MI) in 3 patients (2.1%), repeat revascularization procedures in 9 patients (6.4%) and death in 12 patients (8.6%). The SS independently predicted angina (p=0.024) but was not predictive of MI (p=0.964), death (p=0.292) or repeat revascularization (p=0.069).

Conclusion:

In this patient population, the SS predicted angina in the year following revascularization but was not predictive of MI, death or repeat revascularization.

Abstract P3-03-01: Intracranial PDX models of breast cancer metastasis

Background: Overexpression of the human epidermal growth factor receptor 2 (HER2) in breast cancer is an independent factor for development of brain metastases. Up to 37% of patients with HER2 positive disease relapse intracranially despite control of extra-cranial metastatic disease. Inability of anti-cancer agents to cross an intact blood-brain barrier (BBB) is a possible explanation for the increased incidence of brain metastases.

Subcutaneous (SQ) patient-derived xenograft (PDX) models are increasingly used for efficacy studies in drug development. However, orthotopic PDX models may confer a translational advantage as the patient tumor microenvironment is more closely mimicked. Especially when targeting brain tumors, the major impact of the BBB on drug bioavailability must be taken into consideration. The aim of this study was therefore to develop a panel of intracranial PDX models of breast cancer brain metastases for pre-clinical efficacy studies of new anticancer drugs.

Methods: SQ tumors from three different HER2 positive PDX breast cancer models designated ST340, ST1339 and ST1616B were enzymatically digested and used for intracranial stereotactic injection in nude mice. Contrast-enhanced T1- and T2-weighted Magnetic Resonance Imaging (MRI) were used to determine tumor take. Intracranial tumor growth was monitored using MRI and positron emission tomography (PET) in conjunction with the amino acid radio tracer 18F-FET.

Results: MRI confirmed tumor take in one model as early as 2 weeks after intracranial implantation. Increased 18F-FET uptake was detected in all models. MRI could be effectively used to monitor tumor growth and the corresponding 18F-FET PET images demonstrated increased 18F-FET uptake over time.

Conclusion: Three different HER2 positive intracranial PDX breast metastases models were established from low passage SQ PDX models. We suggest, that using these intracranial PDX models of brain metastases, new drugs for advanced breast cancer can be evaluated in preclinical models that more closely mimic the microenvironment and the BBB in patients. In addition, translational imaging techniques can be evaluated during preclinical testing and the potential of tracers like 18F-FET as imaging biomarkers of therapeutic response can be assessed. Together, the established SQ and orthotopic PDX models of breast cancer and brain metastases can be used as a relevant translational platform for testing of new drugs.

Citation Format: Nielsen CH, Nedergaard MK, Wick MJ, Papadopoulos K, Tolcher AW, Kjaer A. Intracranial PDX models of breast cancer metastasis. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P3-03-01.