Rapid and recurrent neutrophil mobilization regulated by T134, a CXCR4 peptide antagonist.

The CXCR4/stromal cell-derived factor-1 (SDF-1) axis plays important roles in development, leukocyte trafficking, HIV infection, and tumorigenesis. Its critical function in bone marrow stem cell and hematopoietic progenitor cell retention, homing and release has been well-characterized by genetic and pharmacological analyses. However, its role in neutrophil retention and release is still poorly understood. In this study, we demonstrated that T134, a peptide antagonist of human CXCR4, is also a potent antagonist of mouse CXCR4. Treatment of C57BL/6 mice with T134 resulted in a rapid and time-dependent increase of white blood cells (WBC) and neutrophils, as well as hematopoietic stem and progenitor cells in peripheral blood. Interestingly, recurrent WBC and neutrophil mobilization was achieved by repeated T134 treatment, and the T134-mediated increase and subsequent retreat of WBC and neutrophils correlated with T134 activity in the peripheral blood. Kinetic analysis revealed that T134 binding to CXCR4 did not induce any significant cell-surface receptor downregulation, indicating that T134-induced WBC and neutrophil mobilization is likely due to direct blockage of the CXCR4/SDF-1 interaction. The results from this study support an important role of CXCR4/SDF-1 axis in neutrophil retention and release in the marrow.

Preclinical assessment of galunisertib (LY2157299 monohydrate), a first-in-class transforming growth factor-ß receptor type I inhibitor.

Transforming growth factor-ß (TGFß) is an important driver of tumor growth via intrinsic and extrinsic mechanisms, and is therefore an attractive target for developing cancer therapeutics. Using preclinical models, we characterized the anti-tumor activity of a small molecule inhibitor of TGFß receptor I (TGFßRI), galunisertib (LY2157299 monohydrate). Galunisertib demonstrated potent and selective inhibition of TGFßRI with corresponding inhibition of downstream signaling via inhibition of SMAD phosphorylation (pSMAD). Galunisertib also inhibited TGFß-induced pSMAD in vivo, which enabled a pharmacokinetic/pharmacodynamic profile in Calu6 and EMT6-LM2 tumors. Galunisertib demonstrated anti-tumor activity including inhibition of tumor cell migration and mesenchymal phenotype, reversal of TGFß-mediated immune-suppression, and tumor growth delay. A concentration-effect relationship was established with a dosing schedule to achieve the optimal level of target modulation. Finally, a rat model demonstrated a correlation between galunisertib-dependent inhibition of pSMAD in tumor tissues and in PBMCs, supporting the use of PBMCs for assessing pharmacodynamic effects. Galunisertib has been tested in several clinical studies with evidence of anti-tumor activity observed in subsets of patients. Here, we demonstrate that galunisertib inhibits a number of TGFß-dependent functions leading to anti-tumor activity. The enhanced understanding of galunisertib provides rationale for further informed clinical development of TGFß pathway inhibitors.