The results showed that the cytotoxicity of both conjugates 1 and 2 (IC50 = 1.3 and 2.2 uM, respectively), as well as the free Dox (IC50 = 1.5 uM) on MDA-MB-231 breast cancer cell line, were in the low micromolar range (Figure 4). For the breast cancer cell line MDA-MB-468, the free Dox (IC50 = 0.35 uM) was slightly more toxic compared to conjugates 1 (4.7 uM) and 2 (1.2 uM). For the non-cancerous cell line MCF 10A, the free Dox was highly toxic (IC50 = 0.24 uM) whereas conjugates 1 and 2 displayed much-reduced toxicity (IC50 = 38.6 and 15.1 uM, respectively).

Several PDCs have been prepared with peptide 18-4 and doxorubicin (Dox) using different linker chemistries such as ester, amide, succinimidyl thioether, or acyl hydrazone. In vitro results showed that these PDCs were highly specific toward breast cancer cells. PDCs displayed similar toxicity as free Dox toward the breast cancer cells and several-fold (7-40 times) less toxicity toward the non-cancerous cells such as MCF-10A and human umbilical vein endothelial cells (HUVECs). A peptide 18-4-Dox conjugate with amide/succinimidyl thioether linkage showed high selective toxicity toward triple negative breast cancer (TNBC) cell lines, i.e., MDA-MB-231 cells (IC50 1.3 ± 0.2 uM) and MDA-MB-468 cells (IC50 4.7 ± 0.3 uM) compared to the normal breast MCF10A cells (IC50 38.6 ± 1.1 uM). The linkage between the drug and the peptide was stable as the degradation half-life of peptide 18-4-Dox conjugate in the presence of human serum was found to be ˜18 h. Herein, we describe the first in vivo evidence for improved efficacy of this PDC targeting K1 receptor in an orthotopic TNBC mouse model. We also show a higher accumulation of PDC in TNBC tumors in mice, in accord with K1 overexpression in tumor over non-tumor tissues in MDA-MB-231 xenografted mice.

The results showed that the cytotoxicity of both conjugates 1 and 2 (IC50 = 1.3 and 2.2 uM, respectively), as well as the free Dox (IC50 = 1.5 uM) on MDA-MB-231 breast cancer cell line, were in the low micromolar range (Figure 4). For the breast cancer cell line MDA-MB-468, the free Dox (IC50 = 0.35 uM) was slightly more toxic compared to conjugates 1 (4.7 uM) and 2 (1.2 uM). For the non-cancerous cell line MCF 10A, the free Dox was highly toxic (IC50 = 0.24 uM) whereas conjugates 1 and 2 displayed much-reduced toxicity (IC50 = 38.6 and 15.1 uM, respectively).

Several PDCs have been prepared with peptide 18-4 and doxorubicin (Dox) using different linker chemistries such as ester, amide, succinimidyl thioether, or acyl hydrazone. In vitro results showed that these PDCs were highly specific toward breast cancer cells. PDCs displayed similar toxicity as free Dox toward the breast cancer cells and several-fold (7-40 times) less toxicity toward the non-cancerous cells such as MCF-10A and human umbilical vein endothelial cells (HUVECs). A peptide 18-4-Dox conjugate with amide/succinimidyl thioether linkage showed high selective toxicity toward triple negative breast cancer (TNBC) cell lines, i.e., MDA-MB-231 cells (IC50 1.3 ± 0.2 uM) and MDA-MB-468 cells (IC50 4.7 ± 0.3 uM) compared to the normal breast MCF10A cells (IC50 38.6 ± 1.1 uM). The linkage between the drug and the peptide was stable as the degradation half-life of peptide 18-4-Dox conjugate in the presence of human serum was found to be ˜18 h. Herein, we describe the first in vivo evidence for improved efficacy of this PDC targeting K1 receptor in an orthotopic TNBC mouse model. We also show a higher accumulation of PDC in TNBC tumors in mice, in accord with K1 overexpression in tumor over non-tumor tissues in MDA-MB-231 xenografted mice.

The results showed that the cytotoxicity of both conjugates 1 and 2 (IC50 = 1.3 and 2.2 uM, respectively), as well as the free Dox (IC50 = 1.5 uM) on MDA-MB-231 breast cancer cell line, were in the low micromolar range (Figure 4). For the breast cancer cell line MDA-MB-468, the free Dox (IC50 = 0.35 uM) was slightly more toxic compared to conjugates 1 (4.7 uM) and 2 (1.2 uM). For the non-cancerous cell line MCF 10A, the free Dox was highly toxic (IC50 = 0.24 uM) whereas conjugates 1 and 2 displayed much-reduced toxicity (IC50 = 38.6 and 15.1 uM, respectively).

Several PDCs have been prepared with peptide 18-4 and doxorubicin (Dox) using different linker chemistries such as ester, amide, succinimidyl thioether, or acyl hydrazone. In vitro results showed that these PDCs were highly specific toward breast cancer cells. PDCs displayed similar toxicity as free Dox toward the breast cancer cells and several-fold (7-40 times) less toxicity toward the non-cancerous cells such as MCF-10A and human umbilical vein endothelial cells (HUVECs). A peptide 18-4-Dox conjugate with amide/succinimidyl thioether linkage showed high selective toxicity toward triple negative breast cancer (TNBC) cell lines, i.e., MDA-MB-231 cells (IC50 1.3 ± 0.2 uM) and MDA-MB-468 cells (IC50 4.7 ± 0.3 uM) compared to the normal breast MCF10A cells (IC50 38.6 ± 1.1 uM). The linkage between the drug and the peptide was stable as the degradation half-life of peptide 18-4-Dox conjugate in the presence of human serum was found to be ˜18 h. Herein, we describe the first in vivo evidence for improved efficacy of this PDC targeting K1 receptor in an orthotopic TNBC mouse model. We also show a higher accumulation of PDC in TNBC tumors in mice, in accord with K1 overexpression in tumor over non-tumor tissues in MDA-MB-231 xenografted mice.