Evaluation of Protein Kinase cAMP-Activated Catalytic Subunit Alpha as a Therapeutic Target for Fibrolamellar Carcinoma

Background and Aims: Fibrolamellar carcinoma (FLC) is a rare, difficult-to-treat liver cancer primarily affecting pediatric and adolescent patients, and for which precision medicine approaches have historically not been possible. The DNAJB1-PRKACA gene fusion was identified as a driver of FLC pathogenesis. We aimed to assess whether FLC tumors maintain dependency on this gene fusion and determine if PRKACA is a viable therapeutic target. Methods: FLC patient-derived xenograft (PDX) shRNA cell lines were implanted subcutaneously into female NOD-SCID mice and tumors were allowed to develop prior to randomization to doxycycline (to induce knockdown) or control groups. Tumor development was assessed every 2 days. To assess the effect of treatment with novel selective PRKACA small molecule kinase inhibitors, BLU0588 and BLU2864, FLC PDX tumor cells were implanted subcutaneously into NOD-SCID mice and tumors allowed to develop. Mice were randomized to treatment (BLU0588 and BLU2864, orally, once daily) or control groups and tumor size determined as previously. Results: Knockdown of DNAJB1-PRKACA reversed a FLC-specific gene signature and reduced PDX tumor growth in mice compared to the control group. Furthermore, FLC PDX tumor growth was significantly reduced with BLU0588 and BLU2864 treatment vs control (P = .003 and P = .0005, respectively). Conclusion: We demonstrated, using an inducible knockdown and small molecule approaches, that FLC PDX tumors were dependent upon DNAJB1-PRKACA fusion activity. In addition, this study serves as a proof-of-concept that PRKACA is a viable therapeutic target for FLC and warrants further investigation

A precision therapy against cancers driven by KIT/PDGFRA mutations

Targeting oncogenic kinase drivers with small-molecule inhibitors can have marked therapeutic benefit, especially when administered to an appropriate genomically defined patient population. Cancer genomics and mechanistic studies have revealed that heterogeneous mutations within a single kinase can result in various mechanisms of kinase activation. Therapeutic benefit to patients can best be optimized through an in-depth understanding of the disease-driving mutations combined with the ability to match these insights to tailored highly selective drugs. This rationale is presented for BLU-285, a clinical stage inhibitor of oncogenic KIT and PDGFRA alterations, including activation loop mutants that are ineffectively treated by current therapies. BLU-285, designed to preferentially interact with the active conformation of KIT and PDGFRA, potently inhibits activation loop mutants KIT D816V and PDGFRA D842V with subnanomolar potency and also inhibits other well-characterized disease-driving KIT mutants both in vitro and in vivo in preclinical models. Early clinical evaluation of BLU-285 in a phase 1 study has demonstrated marked activity in patients with diseases associated with KIT (aggressive systemic mastocytosis and gastrointestinal stromal tumor) and PDGFRA (gastrointestinal stromal tumor) activation loop mutations.status: publishe

Antibody Fab‐Fc properties outperform titer in predictive models of SIV vaccine‐induced protection

Abstract Characterizing the antigen‐binding and innate immune‐recruiting properties of the humoral response offers the chance to obtain deeper insights into mechanisms of protection than revealed by measuring only overall antibody titer. Here, a high‐throughput, multiplexed Fab‐Fc Array was employed to profile rhesus macaques vaccinated with a gp120‐CD4 fusion protein in combination with different genetically encoded adjuvants, and subsequently subjected to multiple heterologous simian immunodeficiency virus (SIV) challenges. Systems analyses modeling protection and adjuvant differences using Fab‐Fc Array measurements revealed a set of correlates yielding strong and robust predictive performance, while models based on measurements of response magnitude alone exhibited significantly inferior performance. At the same time, rendering Fab‐Fc measurements mathematically independent of titer had relatively little impact on predictive performance. Similar analyses for a distinct SIV vaccine study also showed that Fab‐Fc measurements performed significantly better than titer. These results suggest that predictive modeling with measurements of antibody properties can provide detailed correlates with robust predictive power, suggest directions for vaccine improvement, and potentially enable discovery of mechanistic associations

Characterization of the KRN Cell Transfer Model of Rheumatoid Arthritis (KRN-CTM), a Chronic Yet Synchronized Version of the K/BxN Mouse

In this study, a chronic yet synchronized version of the K/BxN mouse, the KRN-cell transfer model (KRN-CTM), was developed and extensively characterized. The transfer of purified splenic KRN T cells into T cell-deficient B6.TCR.Cα−/−H-2b/g7 mice induced anti-glucose 6-phosphate isomerase antibody-dependent chronic arthritis in 100% of the mice with uniform onset of disease 7 days after T cell transfer. Cellular infiltrations were assessed by whole-ankle transcript microarray, cytokine and chemokine levels, and microscopic and immunohistochemical analyses 7 through 42 days after T cell transfer. Transcripts identified an influx of monocytes/macrophages and neutrophils into the ankles and identified temporal progression of cartilage damage and bone resorption. In both serum and ankle tissue there was a significant elevation in interleukin-6, whereas macrophage inflammatory protein-1 α and monocyte chemotactic protein-1 were only elevated in tissue. Microscopic and immunohistochemical analyses revealed a time course for edema, synovial hypertrophy and hyperplasia, infiltration of F4/80-positive monocytes/macrophages and myeloperoxidase-positive neutrophils, destruction of articular cartilage, pannus invasion, bone resorption, extra-articular fibroplasia, and joint ankylosis. The KRN cell transfer model replicates many features of chronic rheumatoid arthritis in humans in a synchronized manner and lends itself to manipulation of adoptively transferred T cells and characterizing specific genes and T cell subsets responsible for rheumatoid arthritis pathogenesis and progression