Shinichi Yaguchi

Antitumor activity of MST-16, a novel derivative of bis(2,6-dioxopiperazine), in murine tumor models

SummaryWe studied the antitumor activity of newly synthesized bis(1-acyloxymethyl) derivatives of 4,4′-(1,2-ethanediyl)bis(2,6-piperazinedione) using i.p.-i.p. models of P388 leukemia and B16 melanoma. As a result, we found 4,4′-(1,2-ethanediyl)bis(1-isobutoxycarbonyloxymethyl-2,6-piperazinedione) (MST-16) to possess considerable therapeutic activity. MST-16 showed not only marked life-prolonging effects in both P388 leukemia- and B16 melanoma-bearing mice but also a greater therapeutic ratio than did its parent compounds, ICRF-154 and ICRF-159. Further studies revealed that MST-16 has considerable therapeutic activity against a number of other tumors such as ascitic forms of L1210 leukemia, colon 26 adenocarcinoma, and MH-134 hepatoma and solid forms of B16 melanoma, Lewis lung carcinoma, colon 38 adenocarcinoma, and M5076 fibrosarcoma. These results suggest that MST-16 is very promising as an antitumor agent.

Antitumor activities and schedule dependence of orally administered MST-16, a novel derivative of bis(2,6-dioxopiperazine)

SummaryWe studied bioavailability, treatment schedule dependence, and therapeutic efficacy of orally administered MST-16, a novel derivative of bis(2,6-dioxopiperazine), against murine tumors and human tumor xenografts. The rate of its intestinal absorption was about 50%, and it was immediately metabolized to its parent compound, ICRF-154. Therapeutic efficacy of MST-16 was heavily dependent on the treatment schedule: 9 daily oral administrations and treatment every 4 h on day 1 only were much more effective against s.c.-implanted L1210 leukemia than a single dose or five daily administrations giving the same total dose. Orally administered MST-16 showed potent lifeprolonging effects (196%, 219% and 148%) in mice inoculated i.p. with P388, L1210 leukemia, and C-26 colon adenocarcinoma, respectively, but had no effect on B16 melanoma inoculated in the same way. MST-16 inhibited more than 80% growth of Lewis lung carcinoma, B16 melanoma, and C-38 colon adenocarcinoma implanted s.c., but had only a minor effect on M5076 fibrosarcoma. Lung metastasis of Lewis lung carcinoma was also effectively suppressed. Furthermore, MST-16 significantly inhibited growth of human colon, lung and breast cancers implanted s.c. in nude mice. We also made a kinetic analysis of the in vitro cell-killing effect by ICRF-154, the active form of MST-16 in vivo. It demonstrated a cell cycle phase-specific and time-dependent action, providing a reasonable explanation for the schedule-dependent therapeutic effect of MST-16.

Inhibitory effects of ZSTK474, a phosphatidylinositol 3-kinase inhibitor, on adjuvant-induced arthritis in rats.

ObjectiveWe examined the effects of ZSTK474, a phosphatidylinositol 3-kinase (PI3K) inhibitor, on adjuvant-induced arthritis (AIA).MethodsAIA was induced in Lewis rats by subcutaneous administration of Freund’s complete adjuvant at the base of the tail on day 0. ZSTK474 was orally administered once daily from day 10. The severity of AIA was assessed by measuring the hind paw volume. The number of lymphocytes in inguinal lymph nodes (ILN) was determined by flow cytometry. The in vitro effects of ZSTK474 on the cell proliferation, and the cytokines and prostaglandin E2 (PGE2) production were evaluated by BrdU method, ELISA and cytometric beads array.ResultsZSTK474 ameliorated the progression of AIA. The temporary increases in the number of T cells in ILN, which occurred along with the appearance of arthritis, were inhibited in the ZSTK474-treated groups. In vitro studies revealed that ZSTK474 inhibited the production of IFNγ and IL-17 in concanavalin A-activated T cells. In vitro studies further revealed that ZSTK474 inhibited the proliferation and PGE2 production by fibroblast-like synovial cells (FLS).ConclusionZSTK474 demonstrated prophylactic efficacy in a rat model of rheumatoid arthritis (RA) through inhibition of T cell and FLS functions. It was suggested that the inhibitors of PI3K have therapeutic potential for RA.

Effectiveness of combined treatment using X-rays and a phosphoinositide 3-kinase inhibitor, ZSTK474, on proliferation of HeLa cells in vitro and in vivo.

ZSTK474 is a novel orally applicable phosphoinositide 3‐kinase‐specific inhibitor that strongly inhibits cancer cell proliferation. To further explore the antitumor effect of ZSTK474 for future clinical usage, we studied its combined effects with radiation. The proliferation of HeLa cells was inhibited by treatment with X‐rays alone or ZSTK474 alone. Combination treatment using X‐rays then ZSTK474 given orally for 8 days, starting 24 h post‐irradiation, significantly enhanced cell growth inhibition. The combined effect was also observed for clonogenic survival with continuous ZSTK474 treatment. Western blot analysis showed enhanced phosphorylation of Akt and GSK‐3β by X‐irradiation, whereas phosphorylation was inhibited by ZSTK474 treatment alone. Treatment with ZSTK474 after X‐irradiation also inhibited phosphorylation, and remarkably inhibited xenograft tumor growth. Combined treatment with X‐rays and ZSTK474 has greater therapeutic potential than radiation or drug therapy alone, both in vitro and in vivo. (Cancer Sci 2011; 102: 1176–1180)

Antitumor profile of the PI3K inhibitor ZSTK474 in human sarcoma cell lines

Treatment of patients with advanced sarcoma remains challenging due to lack of effective medicine, with the development of novel drugs being of keen interest. A pan-PI3K inhibitor, ZSTK474, has been evaluated in clinical trials against a range of advanced solid tumors, with clinical benefit shown in sarcoma patients. In the present study, we developed a panel of 14 human sarcoma cell lines and investigated the antitumor effect of 24 anticancer agents including ZSTK474, other PI3K inhibitors, and those clinically used for sarcoma treatment. ZSTK474 exhibited a similar antiproliferative profile to other PI3K inhibitors but was clearly different from the other drugs examined. Indeed, ZSTK474 inhibited PI3K-downstream pathways, in parallel to growth inhibition, in all cell lines examined, showing proof-of-concept of PI3K inhibition. In addition, ZSTK474 induced apoptosis selectively in Ewings sarcoma (RD-ES and A673), alveolar rhabdomyosarcoma (SJCRH30) and synovial sarcoma (SYO-1, Aska-SS and Yamato-SS) cell lines, all of which harbor chromosomal translocation and resulting oncogenic fusion genes, EWSR1-FLI1, PAX3-FOXO1 and SS18-SSX, respectively. Finally, animal experiments confirmed the antitumor activity of ZSTK474 in vivo, with superior efficacy observed in translocation-positive cells. These results suggest that ZSTK474 could be a promising drug candidate for treating sarcomas, especially those harboring chromosomal translocation.