Izumi Sugo

Anti–Glypican 3 Antibody as a Potential Antitumor Agent for Human Liver Cancer

Human glypican 3 (GPC3) is preferentially expressed in the tumor tissues of liver cancer patients. In this study, we obtained a monoclonal antibody (mAb) against the COOH-terminal part of GPC3, which induced antibody-dependent cellular cytotoxicity (ADCC). The mAb, designated GC33, exhibited marked tumor growth inhibition of s.c. transplanted Hep G2 and HuH-7 xenografts that expressed GPC3 but did not inhibit growth of the SK-HEP-1 that was negative for GPC3. GC33 was efficacious even in an orthotopic model; it markedly reduced the blood alpha-fetoprotein levels of mice intrahepatically transplanted with Hep G2 cells. Humanized GC33 (hGC33) was as efficacious as GC33 against the Hep G2 xenograft, but hGC33 lacking carbohydrate moieties caused neither ADCC nor tumor growth inhibition. Depletion of CD56+ cells from human peripheral blood mononuclear cells markedly abrogated the ADCC caused by hGC33. The results show that the antitumor activity of hGC33 is mainly attributable to ADCC, and in human, natural killer cell-mediated ADCC is one possible mechanism of the antitumor effects by GC33. hGC33 will provide a novel treatment option for liver cancer patients with GPC3-positive tumors.

Generation of a humanized anti-glypican 3 antibody by CDR grafting and stability optimization.

Glypican 3 (GPC3), a glycosylphosphatidylinositol-anchored heparan sulfate proteoglycan, is expressed in a majority of hepatocellular carcinoma tissues. The murine monoclonal antibody GC33 that specifically binds to the COOH-terminal part of GPC3 causes strong antibody-dependent cellular cytotoxicity against hepatocellular carcinoma cells and exhibits strong antitumor activity in the xenograft models. To apply GC33 for clinical use, we generated a humanized GC33 from complementarity-determining region grafting with the aid of both the hybrid variable region and two-step design methods. The humanized antibody bound to GPC3 specifically and induced antibody-dependent cellular cytotoxicity as effectively as a chimeric GC33 antibody. To improve stability of the humanized GC33, we further optimized humanized GC33 by replacing the amino acid residues that may affect the structure of the variable region of a heavy chain. Substitution of Glu6 with Gln in the heavy chain significantly improved the stability under high temperatures. GC33 also has the risk of deamidation of the -Asn–Gly- sequence in the complementarity-determining region 1 of the light chain. As substitution of Asn diminished the antigen binding, we changed the neighboring Gly to Arg to avoid deamidation. The resulting humanized anti-GPC3 antibody was as efficacious as chimeric GC33 against the HepG2 xenograft and is now being evaluated in clinical trials.

N,N-disubstituted benzopyran-4-(N′-cyano)carboxamidines, cromakalim analogs with selective activity for guinea pig trachealis

N-Cyano-2,2-dimethyl-6-nitro-2H-1-benzopyran-4-carboxamidines have been synthesized. Some of these compounds exhibited selective activity for guinea pig trachealis.

Synthesis and antihypertensive activity of KC-399, a benzopyran K+ channel opener with long duration of action and less tachycardia

Abstract Synthesis and antihypertensive activity of KC-399 (5) have been described. KC-399 (5) showed a highly potent, slow and long-lasting antihypertensive effect with reduced reflex tachycardia.

Abstract 2426: Anti-Glypican3 antibody for treatment of human liver cancer

Glypican-3 (GPC3) is a member of the glypican family of heparan sulfate proteoglycans, which are linked to the cell surface through a glycosyl phosphatidyl inositol anchor. GPC3 has been reported to be highly expressed in the majority (70-100%) of HCC, and considered to play a role in the tumorigenesis of HCC. Although the molecular mechanism by which GPC3 functions in tumorigenesis has not been fully elucidated, the high prevalence in HCC has led to considerable interest in GPC3 as a diagnostic marker and therapeutic target. In this study, we obtained a monoclonal antibody (mAb) against the COOH-terminal part of GPC3, which induced antibody-dependent cellular cytotoxicity (ADCC). The mAb, designated mGC33, exhibited marked tumor growth inhibition of s.c. transplanted Hep G2 and HuH-7 xenografts that expressed GPC3 but did not inhibit growth of the SK-HEP-1 that was negative for GPC3. mGC33 was efficacious even in an orthotopic model; it markedly reduced the blood alpha-fetoprotein levels of mice intrahepatically transplanted with Hep G2 cells. To develop an antibody-based immunotherapy, we generated humanized GC33 (hGC33) by complementarily determining region (CDR) grafting. hGC33 was as efficacious as mGC33 against the Hep G2 xenograft, but hGC33 lacking carbohydrate moieties caused neither ADCC nor tumor growth inhibition. Depletion of CD56+ cells from human peripheral blood mononuclear cells markedly abrogated the ADCC caused by hGC33. The results show that the antitumor activity of hGC33 is mainly attributable to ADCC, and in human, natural killer cell-mediated ADCC is one possible mechanism of the antitumor effects by GC33. We also evaluated the antitumor activity of hGC33 combined with standard chemotherapy agent sorafenib. hGC33 and sorafenib combination was more potent in inhibiting tumor growth than sorafenib alone in the s.c. transplanted Hep G2 xenograft model. Administration of sorafenib alone did not change the GPC3 expression level in xenograft tumor. These suggest that this combination regimen may be clinically useful as an anti-liver cancer therapy. In careful examination of the safety of hGC33 in nonclinical studies, specific adverse findings on GPC3 expressed tissue or organs were not observed after repeated administration. Therefore hGC33 will provide a novel treatment option for liver cancer patients with GPC3-positive tumors. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2426.