A highly selective PI3Kδ inhibitor BGB-10188 shows superior preclinical anti-tumor activities and decreased on-target side effects on colon.

PI3Kδ is a key signal transduction molecule in normal and malignant B cells, as well as in T-regulatory cells, making it a promising target for treatment of hematologic malignancies through both direct killing and anti-tumor immunity regulation. BGB-10188 is a highly selective inhibitor of PI3Kδ, showing more than 3000 folds selectivity over other PI3K isoforms and no significant inhibition across tested kinases. BGB-10188 potently inhibited PI3Kδ with IC50s ranging from 1.7-16 nM through various in vitro assays and showed a long-lasting and strong target inhibition in mouse B cells in vivo. BGB-10188 showed significant antitumor effects in human B cell lymphoma xenograft models as single agent or in combination with the BTK inhibitor zanubrutinib. BGB-10188 showed significant Treg inhibition in blood but not in colon, along with less drug accumulation in colon compared with idelalisib, which is an approved PI3Kdelta inhibitor with high incidence of gastrointestinal side effects in clinic. In summary, BGB-10188 is a novel PI3Kδ inhibitor with high selectivity, potency and improved safety profile shown in preclinical studies, which is showing the potential as a best-in-class PI3Kδ inhibitor.

A Human Peripheral Blood Mononuclear Cell (PBMC) Engrafted Humanized Xenograft Model for Translational Immuno-oncology (I-O) Research.

The discovery and development of immuno-oncology (I-O) therapy in recent years represents a milestone in the treatment of cancer. However, treatment challenges persist. Robust and disease-relevant animal models are vital resources for continued preclinical research and development in order to address a range of additional immune checkpoints. Here, we describe a human peripheral blood mononuclear cell (PBMC) - based humanized xenograft model. BGB-A317 (Tislelizumab), an investigational humanized anti-PD-1 antibody in late-stage clinical development, is used as an example to discuss platform set-up, model characterization and drug efficacy evaluations. These humanized mice support the growth of most human tumors tested, thus allowing the assessment of I-O therapies in the context of both human immunity and human cancers. Once established, our model is comparatively time- and cost-effective, and usually yield highly reproducible results. We suggest that the protocol outlined in this article could serve as a general guideline for establishing mouse models reconstituted with human PBMC and tumors for I-O research.

The binding of an anti-PD-1 antibody to FcγRΙ has a profound impact on its biological functions.

Antibodies targeting PD-1 have been demonstrated durable anti-cancer activity in certain cancer types. However, the anti-PD-1 antibodies are less or not efficacious in many situations, which might be attributed to co-expression of multiple inhibitory receptors or presence of immunosuppressive cells in the tumor microenvironment. Most of the anti-PD-1 antibodies used in clinical studies are of IgG4 isotype with the S228P mutation (IgG4S228P). The functional impact by the interaction of anti-PD-1 IgG4S228P antibody with Fc gamma receptors (FcγRs) is poorly understood. To assess the effects, we generated a pair of anti-PD-1 antibodies: BGB-A317/IgG4S228P and BGB-A317/IgG4-variant (abbreviated as BGB-A317), with the same variable regions but two different IgG4 Fc-hinge sequences. There was no significant difference between these two antibodies in binding to PD-1. However, BGB-A317/IgG4S228P binds to human FcγRI with high affinity and mediates crosslinking between PD-1 and FcγRI. In contrast, BGB-A317 does neither. Further cell-based assays showed that such crosslinking could reverse the function of an anti-PD-1 antibody from blocking to activating. More importantly, the crosslinking induces FcγRI+ macrophages to phagocytose PD-1+ T cells. In a mouse model transplanted with allogeneic human cancer cells and PBMCs, BGB-A317 showed significant tumor growth inhibition, whereas BGB-A317/IgG4S228P had no such inhibition. Immunohistochemistry study revealed an inverse correlation between FcγRI+ murine macrophage infiltration and the density of CD8+PD-1+ human T cells within tumors in the BGB-A317/IgG4S228P-treated group. These evidences suggested that FcγRI+ binding and crosslinking had negative impact on the anti-PD-1 antibody-mediated anti-cancer activity.

Validation of Bevacizumab Therapy Effect on Colon Cancer Subtypes by Using Whole Body Imaging in Mice.

PURPOSE: Preclinical imaging offers a useful tool for monitoring cancer biological behavior and therapy in vivo without the necessity of animal surgery. The following paper describes our examination of tumor progress and anti-angiogenic therapy with Bevacizumab on colon cancer subtypes (SW480 and SW620) by using different non-invasive real-time in vivo imaging techniques. PROCEDURES: Color Doppler ultrasound imaging (CDUI) was used to observe the formation of new blood vessels; a homemade fluorescence reflectance imaging (FRI) apparatus was mainly used to test the difference in VEGFR2 expression between the tumor subtypes. Briefly, 15 Balb/c nude mice bearing subcutaneous SW480 and SW620 xenografts were randomly divided into Control and Drug groups. Bevacizumab treatment lasted for 3 weeks. All images were captured pre- and post-treatment. At the end of experiment, all mice were euthanized, and tumor tissue was collected and analyzed by immunohistochemical staining. RESULTS: Expression of VEGFR2 was found to be slightly (10 %) but significantly higher for the SW620 cells than for SW480 cells. In addition, SW620 has shown to be more vascularized than SW480 subtype. After 3-week Bevacizumab therapy, no blood vessels were found within 83 % of SW620, while it was 67 % in SW480; the increase of SW620 tumor volume post-treatment was only 3.17-fold compared with the tumor volume pre-treatment, and 4.51-fold higher in SW480. CONCLUSION: Our data suggest that SW480 and SW620 cell lines respond differently to Bevacizumab therapy in vivo. Because of higher vascularization, and subsequently higher reduction by drug of new blood vessels and tumor growth rate, xenografts derived from the metastatic SW620 cell line have a better chance of being successfully treated with Bevacizumab compared with those derived from the primary tumor SW480 cell line.

Doping hydroxylated cationic lipid into PEGylated cerasome boosts in vivo siRNA transfection efficacy.

The therapeutic application of small interfering RNA (siRNA) requires safe nanocarriers for specific and efficient delivery in vivo. Herein, PEGylated cationic cerasomes (PCCs) were fabricated by doping a cationic lipid with a hydroxyl group into nanohybrid cerasomes. Multiple properties of PCCs provide a solution to many of the limitations associated with current platforms for the delivery of siRNA. The polyorganosiloxane surface imparts PCCs with higher morphological stability than conventional liposomes. The PEGylation of the cationic cerasome could protect the cerasome nanoparticles from agglomeration and macrophage capture, reduce protein absorption, and consequently prolong the blood circulating time and enhance the siRNA delivery efficiency. In addition, incorporation of the lipid containing a hydroxyl group further facilitates endosome release. Moreover, PCCs were further used to transport siRNA into the cytosol primarily via endocytosis. When applied to systemic administration, PCCs have demonstrated effective delivery into the liver and preferential uptake by hepatocytes in mice, thereby leading to high siRNA gene-silencing activity. All these results show potential therapeutic applications of PCCs-mediated delivery of siRNA for liver diseases.