AAV9:PKP2 improves heart function and survival in a Pkp2-deficient mouse model of arrhythmogenic right ventricular cardiomyopathy.

BACKGROUND: Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a familial cardiac disease associated with ventricular arrhythmias and an increased risk of sudden cardiac death. Currently, there are no approved treatments that address the underlying genetic cause of this disease, representing a significant unmet need. Mutations in Plakophilin-2 (PKP2), encoding a desmosomal protein, account for approximately 40% of ARVC cases and result in reduced gene expression. METHODS: Our goal is to examine the feasibility and the efficacy of adeno-associated virus 9 (AAV9)-mediated restoration of PKP2 expression in a cardiac specific knock-out mouse model of Pkp2. RESULTS: We show that a single dose of AAV9:PKP2 gene delivery prevents disease development before the onset of cardiomyopathy and attenuates disease progression after overt cardiomyopathy. Restoration of PKP2 expression leads to a significant extension of lifespan by restoring cellular structures of desmosomes and gap junctions, preventing or halting decline in left ventricular ejection fraction, preventing or reversing dilation of the right ventricle, ameliorating ventricular arrhythmia event frequency and severity, and preventing adverse fibrotic remodeling. RNA sequencing analyses show that restoration of PKP2 expression leads to highly coordinated and durable correction of PKP2-associated transcriptional networks beyond desmosomes, revealing a broad spectrum of biological perturbances behind ARVC disease etiology. CONCLUSIONS: We identify fundamental mechanisms of PKP2-associated ARVC beyond disruption of desmosome function. The observed PKP2 dose-function relationship indicates that cardiac-selective AAV9:PKP2 gene therapy may be a promising therapeutic approach to treat ARVC patients with PKP2 mutations.

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a heart disease that leads to abnormal heartbeats and a higher risk of sudden cardiac death. ARVC is often caused by changes in a gene called PKP2, that then makes less PKP2 protein. PKP2 protein is important for the normal structure and function of the heart. Human ARVC characteristics can be mimicked in a mouse model missing this gene. Given no therapeutic option, our goal was to test if adding a working copy of PKP2 gene in the heart of this mouse model, using a technique called gene therapy that can deliver genes to cells, could improve heart function. Here, we show that a single dose of PKP2 gene therapy can improve heart function and heartbeats as well as extend lifespan in mice. PKP2 gene therapy may be a promising approach to treat ARVC patients with PKP2 mutations.

Decoding the small size challenges of mini-tablets for enhanced dose flexibility and micro-dosing.

Mini-tablets are an age appropriate dosage form for oral administration to pediatric and geriatric patients, either as individual mini-tablets or as composite dosage units. Smaller size mini-tablets than the commonly used 2 mm or larger size would offer more tailored micro-dose delivery of investigational drugs. This work demonstrated drug substance particle size, drug loading and mini-tablet size ranges to achieve acceptable quality attributes of mini-tablets. A platform formulation with 60, 80, and 100 µm (particle size D6,3) ibuprofen at 3, 14, and 25% loadings were directly compressed into 1.2, 1.5, 2, and 2.5 mm diameter mini-tablets. With an enhanced weight control approach, all the mini-tablet batches except the 1.2 mm diameter mini-tablets with 100 µm ibuprofen at 3% loading would achieve acceptable content uniformity as individual mini-tablets (USP <905> L2 criteria) and as composite dosage units of five or more mini-tablets (USP <905> L1 criteria). A dissolution method was developed and successfully utilized to evaluate the formulations herein. Small size mini-tablets, small ibuprofen particle size, and low dose (or low ibuprofen loading) enhanced the dissolution performance. In addition, hypothetical scenarios of potential dose flexibility, dose range, dose titration, and excipient burden were discussed. The results of this study provide guidance for development of smaller size mini-tablets that enable dosing as a single or composite dosage unit, reduce excipient burden and leverage dispensing technology to achieve enhanced dosing flexibility and micro-dosing.

Pan-PIM kinase inhibition provides a novel therapy for treating hematologic cancers.

PURPOSE: PIM kinases have been shown to act as oncogenes in mice, with each family member being able to drive progression of hematologic cancers. Consistent with this, we found that PIMs are highly expressed in human hematologic cancers and show that each isoform has a distinct expression pattern among disease subtypes. This suggests that inhibitors of all three PIMs would be effective in treating multiple hematologic malignancies. EXPERIMENTAL DESIGN: Pan-PIM inhibitors have proven difficult to develop because PIM2 has a low Km for ATP and, thus, requires a very potent inhibitor to effectively block the kinase activity at the ATP levels in cells. We developed a potent and specific pan-PIM inhibitor, LGB321, which is active on PIM2 in the cellular context. RESULTS: LGB321 is active on PIM2-dependent multiple myeloma cell lines, where it inhibits proliferation, mTOR-C1 signaling and phosphorylation of BAD. Broad cancer cell line profiling of LGB321 demonstrates limited activity in cell lines derived from solid tumors. In contrast, significant activity in cell lines derived from diverse hematological lineages was observed, including acute lymphoblastic leukemia (ALL), acute myelogenous leukemia (AML), multiple myeloma and non-Hodgkin lymphoma (NHL). Furthermore, we demonstrate LGB321 activity in the KG-1 AML xenograft model, in which modulation of pharmacodynamics markers is predictive of efficacy. Finally, we demonstrate that LGB321 synergizes with cytarabine in this model. CONCLUSIONS: We have developed a potent and selective pan-PIM inhibitor with single-agent antiproliferative activity and show that it synergizes with cytarabine in an AML xenograft model. Our results strongly support the development of Pan-PIM inhibitors to treat hematologic malignancies.