A Phase I Trial Evaluating the Addition of Lenalidomide to Patients with Relapsed/Refractory Multiple Myeloma Progressing on Ruxolitinib and Methylprednisolone.

BACKGROUND: Ruxolitinib (RUX), an orally administered selective Janus kinase 1/2 inhibitor, has received approval for the treatment of myelofibrosis, polycythemia vera, and graft-versus-host disease. We have previously demonstrated the anti-multiple myeloma effects of RUX alone and in combination with the immunomodulatory agent lenalidomide (LEN) and glucocorticosteroids both pre-clinically and clinically. OBJECTIVE: This study aims to evaluate whether LEN can achieve clinical activity among patients with multiple myeloma progressing on the combination of RUX and methylprednisolone (MP). METHODS: In this part of a phase I, multicenter, open-label study, we evaluated the safety and efficacy of RUX and MP for patients with multiple myeloma with progressive disease who had previously received a proteasome inhibitor, LEN, glucocorticosteroids, and at least three prior regimens; we also determined the safety and efficacy of adding LEN at the time of disease progression from the initial doublet treatment. Initially, all subjects received oral RUX 15 mg twice daily and oral MP 40 mg every other day. Those patients who developed progressive disease according to the International Myeloma Working Group criteria then received LEN 10 mg once daily on days 1-21 within a 28-day cycle in addition to RUX and MP, which were administered at the same doses these patients were receiving at the time progressive disease developed. RESULTS: Twenty-nine subjects (median age 64 years; 18 [62%] male) were enrolled in this part of the study and initially received the two-drug combination of RUX and MP. The median number of prior therapies was six (range 3-12). The overall response rate from this two-drug combination was 31% and the clinical benefit rate was 34%. The best responses were 1 very good partial response, 8 partial responses, 1 minor response, 12 stable disease, and 7 progressive disease. The median progression-free survival was 3.5 months (range  0.5-36.2 months). The median time to response was 3.0 months. The median duration of response was 12.5 months (range 2.8-36.2 months). Twenty (69%) patients who showed progressive disease had LEN added to RUX and MP; all patients had prior exposure to LEN and all but one patient was refractory to their last LEN-containing regimen. After the addition of LEN, the overall response rate was 30% and the clinical benefit rate was 40%. The best responses of patients following the addition of LEN were 2 very good partial responses, 4 partial responses, 2 minor responses, 8 stable disease, and 4 progressive disease. The median time to response was 2.6 months (range 0.7-15.0 months). The median duration of response was not reached. The median progression-free survival following the addition of LEN was 3.5 months (range 0.3-25.9 months). CONCLUSIONS: For patients with multiple myeloma, treatment with RUX and MP is effective and well tolerated, and LEN can be used to extend the benefit of this RUX-based treatment. CLINICAL TRIAL REGISTRATION: This study is registered with ClinicalTrials.gov, NCT03110822, and is ongoing.

Preclinical and clinical evaluation of the Janus Kinase inhibitor ruxolitinib in multiple myeloma.

Multiple myeloma (MM) is the most common primary malignancy of the bone marrow. No established curative treatment is currently available for patients diagnosed with MM. In recent years, new and more effective drugs have become available for the treatment of this B-cell malignancy. These new drugs have often been evaluated together and in combination with older agents. However, even these novel combinations eventually become ineffective; and, thus, novel therapeutic approaches are necessary to help overcome resistance to these treatments. Recently, the Janus Kinase (JAK) family of tyrosine kinases, specifically JAK1 and JAK2, has been shown to have a role in the pathogenesis of MM. Preclinical studies have demonstrated a role for JAK signaling in direct and indirect growth of MM and downregulation of anti-tumor immune responses in these patients. Also, inhibition of JAK proteins enhances the anti-MM effects of other drugs used to treat MM. These findings have been confirmed in clinical studies which have further demonstrated the safety and efficacy of JAK inhibition as a means to overcome resistance to currently available anti-MM therapies. Additional studies will provide further support for this promising new therapeutic approach for treating patients with MM.

Human cerebellar organoids with functional Purkinje cells.

Research on human cerebellar development and disease has been hampered by the need for a human cell-based system that recapitulates the human cerebellum's cellular diversity and functional features. Here, we report a human organoid model (human cerebellar organoids [hCerOs]) capable of developing the complex cellular diversity of the fetal cerebellum, including a human-specific rhombic lip progenitor population that have never been generated in vitro prior to this study. 2-month-old hCerOs form distinct cytoarchitectural features, including laminar organized layering, and create functional connections between inhibitory and excitatory neurons that display coordinated network activity. Long-term culture of hCerOs allows healthy survival and maturation of Purkinje cells that display molecular and electrophysiological hallmarks of their in vivo counterparts, addressing a long-standing challenge in the field. This study therefore provides a physiologically relevant, all-human model system to elucidate the cell-type-specific mechanisms governing cerebellar development and disease.

Non-synaptic function of the autism spectrum disorder-associated gene SYNGAP1 in cortical neurogenesis.

Genes involved in synaptic function are enriched among those with autism spectrum disorder (ASD)-associated rare genetic variants. Dysregulated cortical neurogenesis has been implicated as a convergent mechanism in ASD pathophysiology, yet it remains unknown how 'synaptic' ASD risk genes contribute to these phenotypes, which arise before synaptogenesis. Here, we show that the synaptic Ras GTPase-activating (RASGAP) protein 1 (SYNGAP1, a top ASD risk gene) is expressed within the apical domain of human radial glia cells (hRGCs). In a human cortical organoid model of SYNGAP1 haploinsufficiency, we find dysregulated cytoskeletal dynamics that impair the scaffolding and division plane of hRGCs, resulting in disrupted lamination and accelerated maturation of cortical projection neurons. Additionally, we confirmed an imbalance in the ratio of progenitors to neurons in a mouse model of Syngap1 haploinsufficiency. Thus, SYNGAP1-related brain disorders may arise through non-synaptic mechanisms, highlighting the need to study genes associated with neurodevelopmental disorders (NDDs) in diverse human cell types and developmental stages.

Present and Future Modeling of Human Psychiatric Connectopathies With Brain Organoids.

Brain organoids derived from human pluripotent stem cells are emerging as a powerful tool to model cellular aspects of neuropsychiatric disorders, including alterations in cell proliferation, differentiation, migration, and lineage trajectory. To date, most contributions in the field have focused on modeling cellular impairment of the cerebral cortex, with few studies probing dysfunction in local network connectivity. However, it is increasingly more apparent that these psychiatric disorders are connectopathies involving multiple brain structures and the connections between them. Therefore, the lack of reproducible anatomical features in these 3-dimensional cultures represents a major bottleneck for effectively modeling brain connectivity at the micro(cellular) level and at the macroscale level between brain regions. In this perspective, we review the use of current organoid protocols to model neuropsychiatric disorders with a specific emphasis on the potential and limitations of the current strategies to model impairments in functional connectivity. Finally, we discuss the importance of adopting interdisciplinary strategies to establish next-generation, multiregional organoids that can model, with higher fidelity, the dysfunction in the development and functionality of long-range connections within the brain of patients affected by psychiatric disorders.

Nests of dividing neuroblasts sustain interneuron production for the developing human brain.

The human cortex contains inhibitory interneurons derived from the medial ganglionic eminence (MGE), a germinal zone in the embryonic ventral forebrain. How this germinal zone generates sufficient interneurons for the human brain remains unclear. We found that the human MGE (hMGE) contains nests of proliferative neuroblasts with ultrastructural and transcriptomic features that distinguish them from other progenitors in the hMGE. When dissociated hMGE cells are transplanted into the neonatal mouse brain, they reform into nests containing proliferating neuroblasts that generate young neurons that migrate extensively into the mouse forebrain and mature into different subtypes of functional interneurons. Together, these results indicate that the nest organization and sustained proliferation of neuroblasts in the hMGE provide a mechanism for the extended production of interneurons for the human forebrain.

Upgrading the Physiological Relevance of Human Brain Organoids.

The recent advent of human pluripotent stem cell (PSC)-derived 3D brain organoids has opened a window into aspects of human brain development that were not accessible before, allowing tractable monitoring and assessment of early developmental processes. However, their broad and effective use for modeling later stages of human brain development and disease is hampered by the lack of a stereotypic anatomical organization, which limits maturation processes dependent upon formation of unique cellular interactions and short- and long-range network connectivity. Emerging methods and technologies aimed at tighter regulatory control through bioengineering approaches, along with newer unbiased organoid analysis readouts, should resolve several of the current limitations. Here, we review recent advances in brain organoid generation and characterization with a focus on highlighting future directions utilizing interdisciplinary strategies that will be important for improving the physiological relevance of this model system.