Hiroshi Umehara

KW-2449, a novel multikinase inhibitor, suppresses the growth of leukemia cells with FLT3 mutations or T315I-mutated BCR/ABL translocation.

KW-2449, a multikinase inhibitor of FLT3, ABL, ABL-T315I, and Aurora kinase, is under investigation to treat leukemia patients. In this study, we examined its possible modes of action for antileukemic effects on FLT3-activated, FLT3 wild-type, or imatinib-resistant leukemia cells. KW-2449 showed the potent growth inhibitory effects on leukemia cells with FLT3 mutations by inhibition of the FLT3 kinase, resulting in the down-regulation of phosphorylated-FLT3/STAT5, G(1) arrest, and apoptosis. Oral administration of KW-2449 showed dose-dependent and significant tumor growth inhibition in FLT3-mutated xenograft model with minimum bone marrow suppression. In FLT3 wild-type human leukemia, it induced the reduction of phosphorylated histone H3, G(2)/M arrest, and apoptosis. In imatinib-resistant leukemia, KW-2449 contributed to release of the resistance by the simultaneous down-regulation of BCR/ABL and Aurora kinases. Furthermore, the antiproliferative activity of KW-2449 was confirmed in primary samples from AML and imatinib-resistant patients. The inhibitory activity of KW-2449 is not affected by the presence of human plasma protein, such as alpha1-acid glycoprotein. These results indicate KW-2449 has potent growth inhibitory activity against various types of leukemia by several mechanisms of action. Our studies indicate KW-2449 has significant activity and warrants clinical study in leukemia patients with FLT3 mutations as well as imatinib-resistant mutations.

A Novel FLT3 Inhibitor FI-700 Selectively Suppresses the Growth of Leukemia Cells with FLT3 Mutations

Purpose: The aim of this study was to evaluate the antileukemia activity of a novel FLT3 kinase inhibitor, FI-700. Experimental Design: The antileukemia activity of FI-700 was evaluated in human leukemia cell lines, mutant or wild-type (Wt)-FLT3–expressing mouse myeloid precursor cell line, 32D and primary acute myeloid leukemia cells, and in xenograft or syngeneic mouse leukemia models. Results: FI-700 showed a potent IC50 value against FLT3 kinase at 20 nmol/L in an in vitro kinase assay. FI-700 showed selective growth inhibition against mutant FLT3-expressing leukemia cell lines and primary acute myeloid leukemia cells, whereas it did not affect the FLT3 ligand (FL)–driven growth of Wt-FLT3–expressing cells. These antileukemia activities were induced by the significant dephosphorylations of mutant FLT3 and STAT5, which resulted in G1 arrest of the cell cycle. Oral administration of FI-700 induced the regression of tumors in a s.c. tumor xenograft model and increased the survival of mice in an i.v. transplanted model. Furthermore, FI-700 treatment eradicated FLT3/ITD-expressing leukemia cells, both in the peripheral blood and in the bone marrow. In this experiment, the depletion of FLT3/ITD-expressing cells by FI-700 was more significant than that of Ara-C, whereas bone marrow suppression by FI-700 was lower than that by Ara-C. Conclusions: FI-700 is a novel and potent FLT3 inhibitor with promising antileukemia activity.

Novel and orally active 5-(1,3,4-oxadiazol-2-yl)pyrimidine derivatives as selective FLT3 inhibitors

5-(1,3,4-Oxadiazol-2-yl)pyrimidine derivative 1 was identified as a new class of FLT3 inhibitor from our compound library. With the aim of enhancement of antitumor activity of 2 prepared by minor modification of 1, structure optimization of side chains at the 2-, 4-, and 5-positions of the pyrimidine ring of 2 was performed to improve the metabolic stability. Introduction of polar substituents on the 1,3,4-oxadiazolyl group contributed to a significant increase in the metabolic stability. As a result, a series of compounds showed increased efficacy against MOLM-13 xenograft model in mice by oral administration.

Abstract 3605: KW-2450, a novel orally-active dual IGF1R/IR inhibitor: Antitumor effects in vitro and in vivo

Proceedings: AACR 102nd Annual Meeting 2011‐‐ Apr 2‐6, 2011; Orlando, FL KW-2450 is an orally active, multi-kinase inhibitor which inhibits both insulin-like growth factor receptor (IGF-1R) and insulin receptor (IR) with an IC50 of 7.39 nmol/L and 5.64 nmol/L, respectively. KW-2450 also exhibits inhibitory activities (>90% at 100 nmol/L) against several protein tyrosine kinases such as FAK, FLT1, FLT3, JAK2, KDR, TRKA, and Aurora A. KW-2450 inhibited the growth of various types of malignant cells, and the reduction of phosphorylated IGF-1R or IR and their downstream signalling such as phosphorylation of AKT and ERK were observed from 10 to 30 nmol/L in vitro. The PK/PD study of KW-2450 was conducted in a human colon cancer HT-29/GFP xenograft model. The plasma concentrations of KW-2450 were measured by LC/MS/MS method and the phosphorylation status of IGF-1R (P-IGF-1R) and AKT (P-AKT) in tumor tissue were examined by Western blotting. A single oral administration of KW-2450 showed inhibition of P-IGF-1R and P-AKT in tumor tissue in accordance with the increasing plasma concentration and peaked 2 hours after the administration of the drug at doses of 10 to 80 mg/kg. In this model, KW-2450 showed a statistically significant suppression of tumor growth by oral administration at a dose of 40 mg/kg once a day for 14 days. In addition, KW-2450 at a dose of 10 mg/kg showed a potent growth inhibitory activity against a human myeloma KMS-12-BM xenograft model, which is sensitive to the compound in vitro. In mice, KW-2450 induced an increase of plasma glucose levels at 20 mg/kg and higher in a dose-dependent manner. However, the increase in glucose was transient and it returned to normal levels within 2 hours at 20 mg/kg, 4 hours at 40 mg/kg and 8 hours at 80 mg/kg. A similar trend was seen in insulin levels which return to normal levels within 4 hours at 10 mg/kg, 8 hours at 20 and 40 mg/kg, and 24 hours at 80 mg/kg. In summary, these pharmacological studies revealed that KW-2450 could act as a potent and selective dual IGF-1R/IR inhibitor and exert antitumor effects on various types of malignant cells in vitro and in vivo, although this compound shows multi kinase inhibitory activity in a cell free system. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3605. doi:10.1158/1538-7445.AM2011-3605

Preclinical and phase I clinical studies of KW-2450, a dual IGF-1R/IR tyrosine kinase inhibitor, in combination with lapatinib and letrozole

Background: KW-2450 is an oral dual insulin-like growth factor-1 receptor/insulin receptor tyrosine kinase inhibitor. We investigated the in vitro and in vivo preclinical activity of KW-2450 plus lapatinib and letrozole and conducted a phase I trial of the triple-drug combination in one male and 10 postmenopausal female patients with advanced/metastatic hormone receptor-positive, human epidermal growth factor receptor 2 (HER2)-positive breast cancer. Methods: A series of in vitro and in vivo animal studies was undertaken of KW-2450 in combination with lapatinib and hormonal agents. The phase I trial was conducted to establish the safety, tolerability, and recommended phase II dose (RP2D) of KW-2450 administered in combination with lapatinib and letrozole. Results: Preclinical studies showed KW-2450 and lapatinib act synergistically to induce in vitro apoptosis and inhibit growth of HER2-positive MDA-MB-361 and BT-474 breast cancer cell lines. This combined effect was confirmed in vivo using the MDA-MB-361 xenograft model. KW-2450 showed synergistic in vitro growth inhibition with letrozole and 4-hydroxytamoxifen in ER-positive MCF-7 breast cancer cells and MCF-7-Ac1 aromatase-transfected MCF-7 cells. In the phase I study, dose-limiting toxicity (DLT; grade 3 rash and grade 3 hyperglycemia, respectively) occurred in two of three patients at the dose of KW-2450 25 mg/day plus lapatinib 1500 mg/day and letrozole 2.5 mg/day. The RP2D of the triple-drug combination was established as KW-2450 25 mg/day, lapatinib 1250 mg/day, and letrozole 2.5 mg/day with no DLT at this dose level. Conclusions: The proposed phase II study of the RP2D for the triple-drug combination did not progress because of anticipated difficulty in patient enrollment and further clinical development of KW-2450 was terminated.

Abstract 920: KW-2450, a novel IGF-1R/IR inhibitor, enhances the antitumor effect of lapatinib, letrozole or 4-hydroxy-tamoxifen in breast cancer cells.

[Background] Both the insulin-like growth factor-1 receptor (IGF-1R) and insulin receptors (IR) have been found to be promising targets for breast cancer therapy because their activation has been associated with breast cancer development, progression and drug resistance. KW-2450, a potent inhibitor of both IGF-1R and IR, is currently in clinical development in combination with lapatinib and letrozole for HER2-positive advanced or metastatic breast cancer. To support the rationale for evaluating this combination, we examined the combined effects of KW-2450 and lapatinib, a HER2/EGFR inhibitor, in a HER2/IGF-1R-expressing breast cancer cell line, and the combined effects of KW-2450 and either letrozole or 4-hydroxy-tamoxifen in a hormone-dependent breast cancer cell line. [Results] KW-2450 and lapatinib showed a strong synergistic effect against the HER2/IGF-1R double-positive cell line, MDA-MB-361, probably caused by enhanced caspase-3/7 activation, compared to the treatment with lapatinib alone. In this setting, KW-2450 completely inhibited the phosphorylation of IGF-1R/IR, whereas lapatinib mostly inhibited the phosphorylation of HER2. Interestingly, neither KW-2450 nor lapatinib inhibited Akt phosphorylation, however, the combined treatment showed a remarkable inhibition of Akt phosphorylation. In fact, KW-2450 showed a potent combined anti-tumor effect in vivo. Furthermore, a microarray analysis identified other biomarkers, such as Ki67, survivin and TIMP3, whose expression levels were changed by the combined treatment with KW-2450 and lapatinib. In an aromatase-dependent cell line, MCF-7-Ac1, the combination of KW-2450 and letrozole showed a strong synergistic effect. Moreover, the combination of KW-2450 and 4-hydroxy-tamoxifen showed a synergistic effect in an estrogen-dependent cell line, MCF-7. [Conclusions] Our results suggest that the combination of KW-2450 and lapatinib in HER2/IGF-1R double-positive breast cancers and that of KW-2450 and anti-hormone agents in hormone-dependent breast cancers are highly effective, exhibiting a synergistic anti-cancer activity. Therefore, KW-2450 may be a promising platform for carrying out combination therapy for breast cancer. Citation Format: Hiroshi Umehara, Fumito Koizumi, Yoshimi Maekawa, Makiko Shimizu, Hiroaki Nakamura, Toshio Ota, Shinji Nara, Takeshi Takahashi, Yutaka Kanda, Norihiko Shiraishi, Shiro Akinaga, Yukimasa Shiotsu, Shiro Soga. KW-2450, a novel IGF-1R/IR inhibitor, enhances the antitumor effect of lapatinib, letrozole or 4-hydroxy-tamoxifen in breast cancer cells. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 920. doi:10.1158/1538-7445.AM2013-920