PharmatrophiX (United States)

Abstract Background: Antibody-drug conjugates (ADCs) have shown clinical success, but resistance, often driven by the payload, can limit long-term efficacy. To address this, Hexagon Bio is mining its natural product library to discover new payloads suitable for mono- or dual-payload ADCs. We report on a ribosome assembly inhibitor (RAI) with strong antitumor activity when conjugated to the anti-TROP2 antibody sacituzumab, both as a mono payload and in combination with the topoisomerase inhibitor Dxd (dual payload). The RAI also shows promise when conjugated to other antibodies, including those targeting low-abundance antigens. Materials and methods: By mining small molecules produced by Hexagon Bio’s 120,000-strain microbial library, several potent cytotoxic compounds were identified. The lead RAI was evaluated as a free agent in cell-free translation assays and as an ADC. It was conjugated to sacituzumab at drug-to-antibody ratios (DARs) of 4 and 8 and tested in:In vitro cytotoxicity (CellTiter-Glo, 120 hrs) and immunogenic cell death (ICD) assays (detection of hallmarks of ICD: extracellular ATP, secreted high mobility group box 1 and cell surface calreticulin, 120-168 hrs)In vivo efficacy models (KPL4, NCI-N87, HT1376)Pharmacokinetics/pharmacodynamic (PK/PD) studiesRodent tolerability studiesTo assess broader applicability, the RAI was also conjugated to other antibodies (anti-HER3, -Nectin4, -ITGB6, -B7H3, -B7H4), and cytotoxicity was evaluated. A dual-payload ADC combining the RAI on sacituzumab was also generated and tested. Results: As a free agent, the RAI potently inhibited protein translation in cell-free assays (EC50∼ 15 nM). When conjugated to sacituzumab, the ADC exhibited strong in vitro cytotoxicity (sub- to single-digit nM) across TROP2-expressing cell lines, including those that have low antigen levels and are resistant to Dxd. The ADC also induced hallmarks of ICD, suggesting it may combine well with checkpoint inhibitors. In vivo, RAI-based ADCs delivered complete responses at ≥ 5 mg/kg (DAR 4) in both Dxd-sensitive (KPL4, NCI-N87) and Dxd-resistant (HT1376) models, outperforming sacituzumab-Dxd (DAR 8). PK profiles were favorable, with circulating t1/2 in line with that of naked sacituzumab. In preliminary tolerability studies, the DAR 4 ADC was well tolerated in mice and rats, suggesting a reasonable therapeutic index.RAI-conjugated ADCs remained cytotoxic when paired with other antibodies, including those targeting antigens expressed as low as 20 K receptors per cell, supporting its translatability. The dual-payload ADC (RAI + Dxd) outperformed the Dxd-only ADC in vitro, including in Dxd-resistant cell lines, demonstrating its potential to broaden efficacy and overcome resistance. Conclusions: Our findings highlight the promise of a novel RAI as a versatile ADC payload, demonstrating potent antitumor activity alone or in combination with Dxd. Its compatibility with diverse antibodies, and favorable PK/tolerability profiles support its further evaluation as an approach to overcome resistance and improve patient outcomes. Citation Format: Tara L. Arvedson. Disrupting ribosome assembly to block protein translation: A novel ADC payload with strong antitumor activity in mono- and dual-payload formats [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics; 2025 Oct 22-26; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2025;24(10 Suppl):Abstract nr A106.

IntroductionElectrographic flow (EGF) mapping is an FDA 510(k)-cleared method for visualizing atrial activation wavefronts in atrial fibrillation (AF). Its clinical efficacy was demonstrated in the FLOW-AF randomized controlled trial, and its fundamental principles have been previously described. However, the underlying machine learning strategy used to develop and refine the EGF algorithm has not yet been detailed. Here, we present how our EGF Model—trained on procedural outcomes from 199 fully anonymized retrospective patient datasets—identifies clinically significant sources of AF and how this machine learning–driven hyperparameter optimization underlies its clinical effectiveness. We also examine the statistical characteristics of the identified sources and their impact on cycle length variability, offering insights into potential pathophysiological mechanisms.Methods and resultsUnipolar electrograms were recorded from patients with persistent or long-standing persistent AF using 64-electrode basket catheters. The EGF Model processes these recordings to reconstruct divergent wavefront propagation patterns and quantify their temporal prevalence. We included 399 retrospective patients in total: 199 for training and optimizing 24 model hyperparameters, and 200 for subsequent analyses of source prevalence and characteristics. Our machine learning approach established an activity threshold, above which divergent wavefront patterns—termed “significant sources”—predicted AF recurrence. This threshold was validated in 85 prospective patients from the published FLOW-AF trial. Significant sources persisting post-procedure were associated with significantly higher recurrence rates than those successfully ablated. Notably, the majority of significant sources were not continuously active; however, when these sources switched “ON,” the spatial variability of AF cycle lengths in the respective atrium decreased by more than 50%, suggesting an entraining effect.ConclusionsBy systematically optimizing the EGF Model's hyperparameters based on clinical outcomes, we reliably detect and target key AF sources that, when ablated, improve procedural success. These findings, supported by the FLOW-AF trial, underscore the usefulness of clinical outcome-based machine learning to improve the efficacy of algorithm based medical diagnostics.

Abstract BackgroundLong‐term maintenance of synaptic adaptations, assessed by long‐term potentiation (LTP), relies on gene induction, and can be impaired by pathological forms of tau protein in Alzheimer’s disease and related dementias (ADRD). We have previously shown that alterations in activity‐dependent gene expression profiles present in tauopathy mice are normalized by LM11A‐31 (C31), a small molecule p75 neurotrophin receptor (NTR) signaling modulator. However, altered gene expression levels represent only part of the complexity of the activity‐regulated transcriptional program. Since neuronal stimulation regulates alternative splicing of a number of activity‐regulated transcripts, and its disruption is associated with dysfunctional changes in ADRD, we aim to identify potential alternative splicing events related to tau‐mediated synaptic dysfunction and whether such alterations are influenced by treatment with a p75 NTR modulator.MethodPS19 (P301S) and wildtype mice were treated with vehicle (Veh) or C31 by oral gavage at 6 months of age for 3 consecutive months. Gene translation‐ and protein synthesis‐dependent synaptic plasticity was induced by applying three events of theta burst stimulation (TBS). RNA sequencing on stimulated [(+) TBS] slices was used to generate activity‐related profiles of alternative splicing events at the isoform level.ResultWe identified axon guidance, glutamatergic synapse, long‐term potentiation and calcium signaling KEGG pathways among the top significant pathways with isoforms down‐regulated in (+) TBS PS19 relative to (+) WT slices. This isoform downregulation was substantially mitigated in (+) TBS slices from PS19 mice treated with C31 (see figure). For example, CACNA1H‐202, a splice‐variant that encodes a voltage‐gated calcium channel protein required for proper synaptic function, is found among the splice variants down‐regulated in Veh and up‐regulated in C31‐treated (+) TBS PS19 slices. Conversely, Prickle2‐204 isoform, associated with the formation of glutamatergic synapses, is up‐regulated in Veh and down‐regulated in C31‐treated (+) TBS PS19 slices. Currently, we are validating and examining the roles of these key C31‐modulated isoforms in neuronal function and synaptic strength as candidate molecular mechanisms involved in activity‐related effects contributing to tau‐induced neurodegeneration.ConclusionWe identified neuronal activity‐related mRNA isoform modulation by C31, indicating that p75NTR signaling might influence alternative splicing events that compromise synapse function in ADRD.

The Parachute(®) (Cardiokinetix, Inc., Menlo Park, California) is a catheter-based device intended to reverse left ventricular (LV) remodeling after antero-apical myocardial infarction. When deployed, the device partitions the LV into upper and lower chambers. To simulate its mechanical effects, we created a finite element LV model based on computed tomography (CT) images from a patient before and 6 months after Parachute(®) implantation. Acute mechanical effects were determined by in silico device implantation (VIRTUAL-Parachute). Chronic effects of the device were determined by adjusting the diastolic and systolic material parameters to better match the 6-month post-implantation CT data and LV pressure data at end-diastole (ED) (POST-OP). Regional myofiber stress and pump function were calculated in each case. The principal finding is that VIRTUAL-Parachute was associated with a 61.2 % reduction in the lower chamber myofiber stress at ED. The POST-OP model was associated with a decrease in LV diastolic stiffness and a larger reduction in myofiber stress at the upper (27.1%) and lower chamber (78.4%) at ED. Myofiber stress at end-systole and stroke volume was little changed in the POST-OP case. These results suggest that the primary mechanism of Parachute(®) is a reduction in ED myofiber stress, which may reverse eccentric post-infarct LV hypertrophy.