SHC014748M, a Novel Selective Inhibitor of PI3Kδ, Demonstrates Promising Pre-Clinical Antitumor Activity in B Cell Lymphomas and CLL

Introduction: PI3Kδ, one of the class I PI3Ks, is found expressed primarily in leukocytes and plays an essential role in B-cell development and function. Here, we comprehensively evaluated the in vitro and in vivo antitumor activity and the underlying mechanism of SHC014748M, an oral selective inhibitor of PI3Kδ under Phase I clinical evaluation.

Methods: Biochemical and cell-based assays were used to measure compound potency and selectivity in lymphoma cell lines as well as primary CLL cells, and PI3K/AKT pathway was measured by Western blot assay, Alphalisa and Elisa. Xenograft model was carried out to validate in-vivo antitumor potency of the compound. Besides, chemokines and cytokines derived from blood samples of patients were also detected.

Results: SHC014748M was 125- to 306-fold more selective for PI3Kδ inhibition relative to other class I PI3K enzymes and showed in vitro activity in most of 23 B lymphoma cell lines. We identified that SHC014748M treatment resulted in a 3.1- to 5.5-fold increase in annexin V/7-ADD staining, indicating a significant apoptosis induction. SHC014748M inhibited phosphorylation of AKT, targets downstream of PI3Kδ, in lymphoma cells. Among the 15 primary CLL cells, the 50% inhibitory concentration (IC₅₀) of SHC014748M varies from 850 nM to 37040 nM respectively and expression of phosphorylation AKT decreased to the normal levels in the presence of SHC014748M or positive control, Idelalisib. In-vivo study revealed that SHC014748M significantly reduced lymphoma cell growth in the treatment group compared with control mice. CCL4, CCL17, CCL22 and CXCL13 derived from patients decreased sharply after SHC014748M treatment.

Conclusion: According to the results, SHC014748M appeared to be a novel promising compound in the treatment of B cell lymphomas and CLL.