Pathological complete remission of relapsed tumor by photo-activating antibody-mimetic drug conjugate treatment.

Antibody-mimetic drug conjugate is a novel noncovalent conjugate consisting of an antibody-mimetic recognizing a target molecule on the cancer cell surface and low-molecular-weight payloads that kill the cancer cells. In this study, the efficacy of a photo-activating antibody-mimetic drug conjugate targeting HER2-expressing tumors was evaluated in mice, by using the affibody that recognize HER2 (ZHER2:342 ) as a target molecule and an axially substituted silicon phthalocyanine (a novel potent photo-activating compound) as a payload. The first treatment with the photo-activating antibody-mimetic drug conjugates reduced the size of all HER2-expressing KPL-4 xenograft tumors macroscopically. However, during the observation period, relapsed tumors gradually appeared in approximately 50% of the animals. To evaluate the efficacy of repeated antibody-mimetic drug conjugate treatment, animals with relapsed tumors were treated again with the same regimen. After the second observation period, the mouse tissues were examined histopathologically. Unexpectedly, all relapsed tumors were eradicated, and all animals were diagnosed with pathological complete remission. After the second treatment, skin wounds healed rapidly, and no significant side effects were observed in other organs, except for occasional microscopic granulomatous tissues beneath the serosa of the liver in a few mice. Repeated treatments seemed to be well tolerated. These results indicate the promising efficacy of the repeated photo-activating antibody-mimetic drug conjugate treatment against HER2-expressing tumors.

Antibody mimetic drug conjugate manufactured by high-yield Escherichia coli expression and non-covalent binding system.

Antibody-drug conjugates (ADCs) are a major therapeutic tool for the treatment of advanced cancer. Malignant cells in advanced cancer often display multiple genetic mutations and become resistant to monotherapy. Therefore, a therapeutic regimen that simultaneously targets multiple molecules with multiple payloads is desirable. However, the development of ADCs is hampered by issues in biopharmaceutical manufacturing and the complexity of the conjugation process of low-molecular-weight payloads to biologicals. Here, we report antibody mimetic-drug conjugates (AMDCs) developed by exploiting the non-covalent binding property of payloads based on high-affinity binding of mutated streptavidin and modified iminobiotin. Miniprotein antibodies were fused to a low immunogenic streptavidin variant, which was then expressed in Escherichia coli inclusion bodies, solubilized, and refolded into functional tetramers. The AMDC developed against human epidermal growth factor receptor 2 (HER2) effectively killed cultured cancer cells using bis-iminobiotin conjugated to photo-activating silicon phthalocyanine. The HER2-targeting AMDC was also effective in vivo against a mouse KPL-4 xenograft model. This AMDC platform provides rapid, stable, and high-yield therapeutics against multiple targets.

1-tert-butyl-3-[6-(3,5-dimethoxy-phenyl)-2-(4-diethylamino-butylamino)-pyrido[2,3-d]pyrimidin-7-yl]-urea (PD173074), a selective tyrosine kinase inhibitor of fibroblast growth factor receptor-3 (FGFR3), inhibits cell proliferation of bladder cancer carrying the FGFR3 gene mutation along with up-regulation of p27/Kip1 and G1/G0 arrest.

Activating mutation of the fibroblast growth factor receptor-3 (FGFR3) gene is known as a key molecular event in both oncogenesis and cell proliferation of low-grade noninvasive human bladder urothelial carcinoma (UC), which is characterized by frequent intravesical recurrence. In this study, we investigated the antitumor potentiality of 1-tert-butyl-3-[6-(3,5-dimethoxy-phenyl)-2-(4-diethylamino-butylamino)-pyrido[2,3-d]pyrimidin-7-yl]-urea (PD173074), a small-molecule FGFR3-selective tyrosine kinase inhibitor (TKI), as a therapeutic modality using eight UC cell lines. In our in vitro cell proliferation assay, PD173074 suppressed cell proliferation remarkably in two cell lines, namely, UM-UC-14 and MGHU3, which expressed mutated FGFR3 protein. In contrast, the other six cell lines expressing wild-type FGFR3 or without FGFR3 expression were resistant to PD173074 treatment. Cell cycle analysis revealed the growth inhibitory effect of PD173074 was associated with arrest at G(1)-S transition in a dose-depending manner. Furthermore, we observed an inverse relationship between Ki-67 and p27/Kip1 expression after PD173074 treatment, suggesting that up-regulation of p27 recruited UC cells harboring activating FGFR3 mutations in G(1) that was analogous with the other receptor TKIs acting on the epidermal growth factor receptors. In the mouse xenograft models using subcutaneously transplanted UM-UC-14 and MGHU3, orally administered PD173074 suppressed tumor growth and induced apoptotic changes comparable with the results of our in vitro assay. These findings elucidated the effectiveness of molecular targeted approach for bladder UC harboring FGFR3 mutations and the potential utility to decrease the intravesical recurrence of nonmuscle invasive bladder UC after transurethral surgical resection.

siRNA-mediated knockdown of the heme synthesis and degradation pathways: modulation of treatment effect of 5-aminolevulinic acid-based photodynamic therapy in urothelial cancer cell lines.

Photodynamic therapy mediated by 5-aminolevulinic acid (ALA-PDT) has been developed as a therapeutic modality for refractory superficial bladder cancers. Here, in experiments using urothelial cancer cell lines, we investigated the effects of siRNA modulating heme-synthetic and degradation pathways for ALA-PDT. Targeted knockdown of ferrochelatase (FECH) suppressed heme synthesis and significantly increased intracellular protoporphyrin IX (PpIX) accumulation, leading to enhanced phototoxicity in four of five cell lines. Heme oxygenase-1 (HO-1) is recognized as important for cytoprotection against oxidative stress such as PDT. Targeted knockdown of HO-1 leads to decreased intracellular PpIX accumulation, resulting in a failure to enhance ALA-PDT effect in four cell lines. Knockdown of HO-1 caused marked growth inhibition in UM-UC-2 overexpressing HO-1, whereas no inhibitory effect was observed in UM-UC-3 lacking HO-1 expression. Moreover, HO-1 protein levels and (GT)n repeat polymorphism of the HO-1 gene promoter region were examined with the implication that the constitutive expressions of HO-1 protein were associated with a shorter (GT)n repeat. Our results suggested that (1) FECH siRNA improved the phototoxicity of ALA-PDT, (2) overexpression of HO-1 was associated with shorter (GT)n repeat of the promoter region, and (3) siRNA-mediated knockdown of HO-1 could suppress the growth of bladder cancer cells overexpressing HO-1.