Adaptation of a human gut epithelial model in relation to the assessment of clinical pharmacokinetic parameters for selected tyrosine kinase inhibitors

The absorption, efflux and transport properties of two of the most commonly used tyrosine kinase inhibitors (TKIs), Erlotinib (E) and Gefitinib (G) were investigated using an adapted workable methodology of a 3-day Caco-2 cell monolayer transwell system, a standard model to test drug permeability and uptake of orally administered compounds. Monolayer integrity was tested using trans-epithelial electrical resistance (TEER) measurements, while drug concentrations were determined with a validated LC-MS/ MS technique. Addition of 5 % bovine serum albumin (BSA) maintained drug concentrations at 20 µM through the avoidance of chelate formation, (nevertheless, a reduced accumulative mass transport of the protein bound drug was observed). Investigation with Ko143 (a specific blocker of ABCG2) or NaN3 (a metabolic inhibitor) indicated an interplay between active transport and passive diffusion for gefitinib, while active transport proved to be absent for erlotinib (p < 0.05). The mechanism indicates that ABCG2 is partially involved with accumulation of gefitinib in the cell. This adapted methodology is well suited for absorption, efflux and transport studies and may be extended to investigate the dominant mechanism involved in the transport of TKIs

A chemo-enzymatically linked bispecific antibody retargets T cells to a sialylated epitope on CD43 in acute myeloid leukemia

Acute myeloid leukemia (AML) is a high-risk disease with a poor prognosis, particularly in elderly patients. Because current AML treatment relies primarily on untargeted therapies with severe side effects that limit patient eligibility, identification of novel therapeutic AML targets is highly desired. We recently described AT1413, an antibody produced by donor B cells of a patient with AML cured after allogeneic hematopoietic stem cell transplantation. AT1413 binds CD43s, a unique sialylated epitope on CD43, which is weakly expressed on normal myeloid cells and overexpressed on AML cells. Because of its selectivity for AML cells, we considered CD43s as a target for a bispecific T-cell-engaging antibody (bTCE) and generated a bTCE by coupling AT1413 to two T-cell-targeting fragments using chemo-enzymatic linkage. In vitro, AT1413 bTCE efficiently induced T-cell-mediated cytotoxicity toward differentAMLcell lines and patient-derivedAMLblasts, whereas endothelial cells with low binding capacity for AT1413 remained unaffected. In the presence of AML cells, AT1413 bTCE induced upregulation of T-cell activation markers, cytokine release, and T-cell proliferation. AT1413 bTCE was also effective in vivo. Mice either coinjected with human peripheral blood mononuclear cells or engrafted with human hematopoietic stem cells [human immune system (HIS) mice] were inoculated with an AML cell line or patient-derived primary AML blasts. AT1413 bTCE treatment strongly inhibited tumor growth and, in HIS mice, had minimal effects on normal human hematopoietic cells. Taken together, our results indicate that CD43s is a promising target for T-cell-engaging antibodies and that AT1413 holds therapeutic potential in a bTCE-format. Significance: These findings offer preclinical evidence for the therapeutic potential of a bTCE antibody that targets a sialylated epitope on CD43 in AML