First-line nivolumab plus ipilimumab or chemotherapy versus chemotherapy alone in advanced esophageal squamous cell carcinoma: a Japanese subgroup analysis of open-label, phase 3 trial (CheckMate 648/ONO-4538-50).

BACKGROUND: Programmed cell death 1 (PD-1)-based treatments are approved for several cancers. CheckMate 648, a global, phase 3 trial, showed that first-line nivolumab (anti-PD-1 antibody) plus ipilimumab (NIVO + IPI) or nivolumab plus chemotherapy (NIVO + Chemo) significantly increased survival in advanced esophageal squamous cell carcinoma (ESCC) without new safety signals versus chemotherapy alone (Chemo). METHODS: We evaluated the Japanese subpopulation of CheckMate 648 (n = 394/970), randomized to receive first-line NIVO + IPI, NIVO + Chemo, or Chemo. Efficacy endpoints included overall survival (OS) and progression-free survival assessed by blinded independent central review in Japanese patients with tumor-cell programmed death-ligand 1 (PD-L1) expression ≥ 1% and in all randomized Japanese patients. RESULTS: In the Japanese population, 131, 126, and 137 patients were treated with NIVO + IPI, NIVO + Chemo, and Chemo, and 66, 62, and 65 patients had tumor-cell PD-L1 ≥ 1%, respectively. In patients with tumor-cell PD-L1 ≥ 1%, median OS was numerically longer with NIVO + IPI (20.2 months; hazard ratio [95% CI], 0.46 [0.30-0.71]) and NIVO + Chemo (17.3 months; 0.53 [0.35-0.82]) versus Chemo (9.0 months). In all randomized patients, median OS was numerically longer with NIVO + IPI (17.6 months; 0.68 [0.51-0.92]) and NIVO + Chemo (15.5 months; 0.73 [0.54-0.99]) versus Chemo (11.0 months). Grade 3-4 treatment-related adverse events were reported in 37%, 49%, and 36% of all patients in the NIVO + IPI, NIVO + Chemo, and Chemo arms, respectively. CONCLUSION: Survival benefits with acceptable tolerability observed for NIVO + IPI and NIVO + Chemo treatments strongly support their use as a new standard first-line treatment in Japanese patients with advanced ESCC. GOV ID: NCT03143153.

Platelet protein S limits venous but not arterial thrombosis propensity by controlling coagulation in the thrombus.

Anticoagulant protein S (PS) in platelets (PSplt) resembles plasma PS and is released on platelet activation, but its role in thrombosis has not been elucidated. Here we report that inactivation of PSplt expression using the Platelet factor 4 (Pf4)-Cre transgene (Pros1lox/loxPf4-Cre+) in mice promotes thrombus propensity in the vena cava, where shear rates are low, but not in the carotid artery, where shear rates are high. At a low shear rate, PSplt functions as a cofactor for both activated protein C and tissue factor pathway inhibitor, thereby limiting factor X activation and thrombin generation within the growing thrombus and ensuring that highly activated platelets and fibrin remain localized at the injury site. In the presence of high thrombin concentrations, clots from Pros1lox/loxPf4-Cre- mice contract, but not clots from Pros1lox/loxPf4-Cre+ mice, because of highly dense fibrin networks. Thus, PSplt controls platelet activation as well as coagulation in thrombi in large veins, but not in large arteries.

Barriers to antibody therapy in solid tumors, and their solutions.

Antibody drugs have become the mainstream of cancer treatment due to advances in cancer biology and Ab engineering. However, several barriers to Ab therapy have also been identified. These include various mechanisms for Ab drug resistance, such as heterogeneity of antigen expression in tumor cells and reduction in antitumor immunity due to expression diversity, polymorphism of Fc receptors (FcR) in effector cells, and reduced function of effector cells. Countermeasures to each resistance mechanism are being investigated. This review focuses on barriers that impede the delivery of Ab drugs due to features of the solid tumor microenvironment. Unlike hematological malignancies, in which the target tumor cells are in blood vessels, clinical solid tumors contain cancer stroma, which interferes with the delivery of Ab drugs. In addition, the cancer mass itself interferes with the penetration of Ab drugs. In this article, I will consider the etiology of cancer stroma and propose a new Ab drug development strategy for solid cancer treatment centering on cancer stromal targeting (CAST) therapy using anti-insoluble fibrin Ab-drug conjugate (ADC), which can overcome the cancer stroma barrier. The recent success of ADCs, chimeric antigen receptor T cells (CAR-Ts), and Bi-specific Abs is changing the category of Ab drugs from molecular-targeted drugs based on growth signal inhibition to cancer-specific targeted therapies. Therefore, at the end of this review, I argue that it is time to reorient the concept of Ab drug development.

Radioimmunotherapy with an 211 At-labeled anti-tissue factor antibody protected by sodium ascorbate.

Tissue factor (TF), the trigger protein of the extrinsic blood coagulation cascade, is abundantly expressed in various cancers including gastric cancer. Anti-TF monoclonal antibodies (mAbs) capable of targeting cancers have been successfully applied to armed antibodies such as antibody-drug conjugates (ADCs) and molecular imaging probes. We prepared an anti-TF mAb, clone 1084, labeled with astatine-211 (211 At), as a promising alpha emitter for cancer treatment. Alpha particles are characterized by high linear energy transfer and a range of 50-100 µm in tissue. Therefore, selective and efficient tumor accumulation of alpha emitters results in potent antitumor activities against cancer cells with minor effects on normal cells adjacent to the tumor. Although the 211 At-conjugated clone 1084 (211 At-anti-TF mAb) was disrupted by an 211 At-induced radiochemical reaction, we demonstrated that astatinated anti-TF mAbs eluted in 0.6% or 1.2% sodium ascorbate (SA) solution were protected from antibody denaturation, which contributed to the maintenance of cellular binding activities and cytocidal effects of this immunoconjugate. Although body weight loss was observed in mice administered a 1.2% SA solution, the loss was transient and the radioprotectant seemed to be tolerable in vivo. In a high TF-expressing gastric cancer xenograft model, 211 At-anti-TF mAb in 1.2% SA exerted a significantly greater antitumor effect than nonprotected 211 At-anti-TF mAb. Moreover, the antitumor activities of the protected immunoconjugate in gastric cancer xenograft models were dependent on the level of TF in cancer cells. These findings suggest the clinical availability of the radioprotectant and applicability of clone 1084 to 211 At-radioimmunotherapy.

High expression of TMEM180, a novel tumour marker, is associated with poor survival in stage III colorectal cancer.

BACKGROUND: Transmembrane protein 180 (TMEM180) is a newly identified colorectal cancer (CRC)-specific molecule that is expressed very rarely in normal tissue and up-regulated under hypoxic conditions. We developed a monoclonal antibody (mAb) against TMEM180 and decided to examine the medical significance using the mAb. METHODS: A total of 157 patients (86 men and 71 women; median age 63.0 years) with stage III CRC who underwent curative surgery were analyzed for TMEM180 expression as a retrospective cohort design. Immunohistochemistry with anti-TMEM180 mAb was conducted on frozen sections, and the data were evaluated for any correlation with clinicopathological indices or prognosis. SW480 CRC cells were examined to investigate the relationship between the expression of TMEM180 and tumourigenesis of xenografts. RESULTS: In total, 92 cases had low TMEM expression and 65 had high TMEM180 expression. For disease-free survival, hazard ratio in high-TMEM180 cases was 1.449 (95% confidential interval = 0.802-2.619) higher than in low-TMEM180 cases, but the difference was not significant (p = 0.219). For cancer specific survival, hazard ratio in high-TMEM180 cases was 3.302 (95% confidential interval = 1.088-10.020), significantly higher than in low-TMEM180 cases (p = 0.035). In an assay examining in vitro colony-forming activity in soft agar, SW480-WT cells clearly formed colonies, but neither KD1 nor KD2 cells did. The in vivo tumour-initiating activity of SW480 cell lines was positively correlated with the level of TMEM180 expression. CONCLUSION: These results indicate that TMEM180 is a useful marker for clinical prognosis in patients with CRC. We believe that these fundamental data warrant further basic and translational studies of TMEM180, and its mAb, for development of therapeutics against CRC.

Five-year follow-up of nivolumab treatment in Japanese patients with esophageal squamous-cell carcinoma (ATTRACTION-1/ONO-4538-07).

BACKGROUND: In the phase II ATTRACTION-1 study, nivolumab demonstrated a promising antitumor activity among Japanese patients with treatment-refractory advanced esophageal cancer. Here, we report the follow-up results of ATTRACTION-1 of > 5 years. METHODS: We enrolled patients with esophageal cancer that was refractory or intolerant to a standard chemotherapy. Then, nivolumab (3 mg/kg) was administered every 2 weeks. The primary endpoint was a centrally assessed objective response rate. RESULTS: Nivolumab was administered to 65 patients with esophageal squamous-cell carcinoma (ESCC). The centrally assessed objective response rate was 17.2%. The overall survival rates at 3 and 5 years were 10.9% and 6.3%, respectively. Three-year survivors tended to have more reduced target lesions. A total of 63.1% of the patients exhibited treatment-related adverse events, and no new safety signal was observed. Patients with select adverse events tended to have better overall survival than those without. No apparent chronological order was observed between the first response and the onset of select adverse events. CONCLUSION: Our follow-up analysis of more than 5 years is currently the longest and is the first to demonstrate that nivolumab has long-term efficacy and safety for advanced ESCC.

Targeting anticoagulant protein S to improve hemostasis in hemophilia.

Improved treatments are needed for hemophilia A and B, bleeding disorders affecting 400 000 people worldwide. We investigated whether targeting protein S could promote hemostasis in hemophilia by rebalancing coagulation. Protein S (PS) is an anticoagulant acting as cofactor for activated protein C and tissue factor pathway inhibitor (TFPI). This dual role makes PS a key regulator of thrombin generation. Here, we report that targeting PS rebalances coagulation in hemophilia. PS gene targeting in hemophilic mice protected them against bleeding, especially when intra-articular. Mechanistically, these mice displayed increased thrombin generation, resistance to activated protein C and TFPI, and improved fibrin network. Blocking PS in plasma of hemophilia patients normalized in vitro thrombin generation. Both PS and TFPIα were detected in hemophilic mice joints. PS and TFPI expression was stronger in the joints of hemophilia A patients than in those of hemophilia B patients when receiving on-demand therapy, for example, during a bleeding episode. In contrast, PS and TFPI expression was decreased in hemophilia A patients receiving prophylaxis with coagulation factor concentrates, comparable to osteoarthritis patients. These results establish PS inhibition as both controller of coagulation and potential therapeutic target in hemophilia. The murine PS silencing RNA approach that we successfully used in hemophilic mice might constitute a new therapeutic concept for hemophilic patients.

Evaluation of the antitumor mechanism of antibody-drug conjugates against tissue factor in stroma-rich allograft models.

Tissue factor (TF) is known to be overexpressed in various cancers including pancreatic cancer. The upregulation of TF expression has been observed not only in tumor cells, but also in tumor stromal cells. Because of the potential of TF as a delivery target, several studies investigated the effectiveness of Ab-drug conjugates (ADCs) against TF for cancer therapy. However, it is still unclear whether anti-TF ADC can exert toxicity against both tumor cells and tumor stromal cells. Here, we prepared ADC using a rat anti-mouse TF mAb (clone.1157) and 2 types of in vivo murine pancreatic cancer models, one s.c. and other orthotopic with an abundant tumor stroma. We also compared the feasibility of bis-alkylating conjugation (bisAlk) with that of conventional maleimide-based conjugation (MC). In the s.c. models, anti-TF ADC showed greater antitumor effects than control ADC. The results also indicated that the bisAlk linker might be more suitable than the MC linker for cancer treatments. In the orthotopic model, anti-TF ADC showed greater in vivo efficacy and more extended survival time control ADC. Treatment with anti-TF ADC (20 mg/kg, three times a week) did not affect mouse body weight changes in any in vivo experiment. Furthermore, immunofluorescence staining indicated that anti-TF ADC delivered agents not only to TF-positive tumor cells, but also to TF-positive tumor vascular endothelial cells and other tumor stromal cells. We conclude that anti-TF ADC should be a selective and potent drug for pancreatic cancer therapy.

Significant antitumor effect of an antibody against TMEM180, a new colorectal cancer-specific molecule.

The present state of therapy for colorectal cancer (CRC) is far from satisfactory, highlighting the need for new targets for this disease. We identified a new CRC-specific molecule, TMEM180, a predicted 11-pass transmembrane protein that apparently functions as a cation symporter. We developed an anti-TMEM180 mAb and then succeeded in humanizing the mAb. Immunohistochemistry (IHC) in CRC with the mAb showed a similar positivity rate as compared with anti-epidermal growth factor receptor mAb, and IHC with anti-TMEM180 mAb did not show staining in major organs used in this study. Immune electron microscopy clearly indicated that TMEM180 was present on the tumor exosome. The TMEM180 promoter region contains 10 hypoxia-responsive element consensus sequences; accordingly, SW480 cells upregulated TMEM180 under low-oxygen conditions. Anti-TMEM180 mAb has in vitro antibody-dependent cell-mediated cytotoxicity and complement-dependent cytotoxicity activity, and SW480 CRC xenografts were eradicated by the mAb. These data indicate that TMEM180 may be a new CRC marker and that a mAb against this protein could be used as antibody-based therapy against CRC.

Topological analysis of TMEM180, a newly identified membrane protein that is highly expressed in colorectal cancer cells.

New target molecules for diagnosis of and drug development for colorectal cancer (CRC) are always in great demand. Previously, we identified a new colorectal cancer-specific protein, TMEM180, and successfully developed an anti-TMEM180 monoclonal antibody (mAb) for the diagnosis and treatment of CRC. Although TMEM180 is classified as a member of the cation symporter family and multi-pass membrane protein, little is known about its function. In this study, we examined topology of this membrane protein and analyzed its function. Using a homology model of human TMEM180, we experimentally determined that the protein has 12 transmembrane domains, and that its N-terminal and C-termini are exposed extracellularly. Moreover, we found that the putative cation-binding site of TMEM180 is conserved among orthologs, and that its position is similar to that of melibiose transporter MelB. These results suggest that TMEM180 acts as a cation symporter. Our topological analysis based on the homology model provides insight into functional and structural roles of TMEM180 that may help to elucidate the pathology of CRC.

Characterization of Antibody Products Obtained through Enzymatic and Nonenzymatic Glycosylation Reactions with a Glycan Oxazoline and Preparation of a Homogeneous Antibody-Drug Conjugate via Fc N-Glycan.

Glycan engineering of antibodies has received considerable attention. Although various endo-ß- N-acetylglucosaminidase mutants have been developed for glycan remodeling, a side reaction has been reported between glycan oxazoline and amino groups. In this study, we performed a detailed characterization for antibody products obtained through enzymatic and nonenzymatic reactions with the aim of maximizing the efficiency of the glycosylation reaction with fewer side products. The reactions were monitored by an ultraperformance liquid chromatography system using an amide-based wide-pore column. The products were characterized by liquid chromatography coupled with tandem mass spectrometry. The side reactions were suppressed by adding glycan oxazoline in a stepwise manner under slightly acidic conditions. Through a combination of an azide-carrying glycan transfer reaction under optimized conditions and a bio-orthogonal reaction, a potent cytotoxic agent monomethyl auristatin E was site-specifically conjugated at N-glycosylated Asn297 with a drug-to-antibody ratio of 4. The prepared antibody-drug conjugate exhibited cytotoxicity against HER2-expressing cells.

Collagen type I induces EGFR-TKI resistance in EGFR-mutated cancer cells by mTOR activation through Akt-independent pathway.

Primary resistance to epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) is a serious problem in lung adenocarcinoma patients harboring EGFR mutations. The aim of this study was to examine whether and how collagen type I (Col I), the most abundantly deposited matrix in tumor stroma, affects EGFR-TKI sensitivity in EGFR-mutant cells. We evaluated the EGFR-TKI sensitivity of EGFR-mutated cancer cells cultured with Col I. Changes in the activation of downstream signaling molecules of EGFR were analyzed. We also examined the association between the Col I expression in tumor stroma in surgical specimens and EGFR-TKI response of postoperative recurrence patients with EGFR mutations. Compared to cancer cells without Col I, the survival rate of cancer cells cultured with Col I was significantly higher after EGFR-TKI treatment. In cancer cells cultured with and without Col I, EGFR-TKI suppressed the levels of phosphorylated (p-)EGFR, p-ERK1/2, and p-Akt. When compared to cancer cells without Col I, expression of p-P70S6K, a hallmark of mTOR activation, was dramatically upregulated in cancer cells with Col I. This activation was maintained even after EGFR-TKI treatment. Simultaneous treatment with EGFR-TKI and mTOR inhibitor abrogated Col I-induced resistance to EGFR-TKI. Patients with Col I-rich stroma had a significantly shorter progression-free survival time after EGFR-TKI therapy (238 days vs 404 days; P < .05). Collagen type I induces mTOR activation through an Akt-independent pathway, which results in EGFR-TKI resistance. Combination therapy using EGFR-TKI and mTOR inhibitor could be a possible strategy to combat this resistance.

Spatial regulation of the KH domain RNA-binding protein Rnc1 mediated by a Crm1-independent nuclear export system in Schizosaccharomyces pombe.

RNA-binding proteins (RBPs) play important roles in the posttranscriptional regulation of gene expression, including mRNA stability, transport and translation. Fission yeast rnc1+ encodes a K Homology (KH)-type RBP, which binds and stabilizes the Pmp1 MAPK phosphatase mRNA thereby suppressing the Cl- hypersensitivity of calcineurin deletion and MAPK signaling mutants. Here, we analyzed the spatial regulation of Rnc1 and discovered a putative nuclear export signal (NES)Rnc1 , which dictates the cytoplasmic localization of Rnc1 in a Crm1-independent manner. Notably, mutations in the NESRnc1 altered nucleocytoplasmic distribution of Rnc1 and abolished its function to suppress calcineurin deletion, although the Rnc1 NES mutant maintains the ability to bind Pmp1 mRNA. Intriguingly, the Rnc1 NES mutant destabilized Pmp1 mRNA, suggesting the functional importance of the Rnc1 cytoplasmic localization. Mutation in Rae1, but not Mex67 deletion or overproduction, induced Rnc1 accumulation in the nucleus, suggesting that Rnc1 is exported from the nucleus to the cytoplasm via the mRNA export pathway involving Rae1. Importantly, mutations in the Rnc1 KH-domains abolished the mRNA-binding ability and induced nuclear localization, suggesting that Rnc1 may be exported from the nucleus together with its target mRNAs. Collectively, the functional Rae1-dependent mRNA export system may influence the cytoplasmic localization and function of Rnc1.

Tuned Density of Anti-Tissue Factor Antibody Fragment onto siRNA-Loaded Polyion Complex Micelles for Optimizing Targetability into Pancreatic Cancer Cells.

Antibody fragment (Fab')-installed polyion complex (PIC) micelles were constructed to improve targetability of small interfering RNA (siRNA) delivery to pancreatic cancer cells. To this end, we synthesized a block copolymer of azide-functionalized poly(ethylene glycol) and poly(l-lysine) and prepared PIC micelles with siRNA. Then, a dibenzylcyclooctyne (DBCO)-modified antihuman tissue factor (TF) Fab' was conjugated to azido groups on the micellar surface. A fluorescence correlation spectroscopic analysis revealed that 1, 2, or 3 molecule(s) of Fab'(s) were installed onto one micellar nanoparticle according to the feeding ratio of Fab' (or DBCO) to micelle (or azide). The resulting micelles exhibited ∼40 nm in hydrodynamic diameter, similar to that of the parent micelles before Fab' conjugation. Flow cytometric analysis showed that three molecules of Fab'-installed PIC micelles (3(Fab')-micelles) had the highest binding affinity to cultured pancreatic cancer BxPC3 cells, which are known to overexpress TF on their surface. The 3(Fab')-micelles also exhibited the most efficient gene silencing activity against polo-like kinase 1 mRNA in the cultured cancer cells. Furthermore, the 3(Fab')-micelles exhibited high penetrability and the highest cellular internalization amounts in BxPC3 spheroids compared with one or two molecule(s) of Fab'-installed PIC micelles. These results demonstrate the potential of anti-TF Fab'-installed PIC micelles for active targeting of stroma-rich pancreatic tumors.

Association study of CREBRF missense variant (rs373863828:G > A; p.Arg457Gln) with levels of serum lipid profile in the Pacific populations.

BACKGROUND: A missense variant (rs373863828:G > A; p.Arg457Gln) of the CREBRF gene is strongly associated with a higher body mass index (BMI; kg/m2) in Polynesian populations. This variant has also been reported to be associated with lower total cholesterol in Samoans. AIM: The aim of this study is to examine the association of rs373863828:G > A with levels of serum lipids in four Pacific populations. METHODS: A total of 613 adult subjects were recruited from Tonga (Polynesians) and the Solomon Islands (Melanesians and Micronesians). Multiple regression analyses adjusted for age and sex were performed to examine the association of rs373863828 with levels of serum lipids in each population. RESULTS: A significant association of rs373863828:G > A with lower level of HDL-cholesterol was detected in the Tonga population (ß = -3.32 and p-value = 0.030). The expected change in HDL-cholesterol with respect to a single copy of the rs373863828-A allele was 3.32 mg/dL. However, the association between rs373863828-A and lower levels of HDL-cholesterol was not significant after further adjustment for BMI in the Tonga population (ß = -2.32 and p-value = 0.13). CONCLUSIONS: The rs373863828-A allele may not directly affect the level of serum HDL-cholesterol independent of BMI. To confirm the present findings, association studies with large sample sizes and functional analyses are required.

A missense variant, rs373863828-A (p.Arg457Gln), of CREBRF and body mass index in Oceanic populations.

It has been suggested that a 'thrifty' genotype hypothesis can account for high prevalence of obesity in the island populations of Oceania. A recent genome-wide association study revealed that a missense variant, rs373863828-A (p.Arg457Gln), of the CREBRF gene (encoding CREB3 regulatory factor) was associated with an excessive increase in body mass index (BMI) in Samoans. In the present study, the association of rs373863828-A with an increase in BMI was examined in four Austronesian (AN)-speaking populations in Oceania. We found that rs373863828-A was frequently observed (frequency of 0.15) in Tongans (Polynesians), and was strongly associated with higher BMI (P=6.1 × 10-4). A single copy of the rs373863828-A allele increased BMI by 3.09 kg m-2 after adjustment of age and sex. No significant association was detected in the other three AN-speaking populations (Melanesians and Micronesians) living in Solomon Islands. This was probably due to the low allele frequency (0.02-0.06) of rs373863828-A as well as small sample size. The rs373863828-A allele was not found in both AN-speaking and non-AN-speaking Melanesians living in Papua New Guinea. Our results suggest that rs373863828-A of CREBRF, a promising thrifty variant, arose in recent ancestors of AN-speaking Polynesians.

Development of polymeric micelles for targeting intractable cancers.

In relation to recent advances in nanobiotechnologies, cancer-targeted therapy using nano-scaled drug carriers (nanocarriers) has been attracting enormous attention with success in clinical studies. Polymeric micelles, core-shell-type nanoparticles formed through the self-assembly of block copolymers, are one of the most promising nanocarrier, because their critical features such as size, stability, and drug incorporation efficiency and release rate can be modulated by designing the constituent block copolymers. The utilities of polymeric micelles have been reported not only in experimental tumor models in mice but also in clinical studies. In this article, we aim to explain the rationale of designing polymeric micelles for targeting intractable cancers such as pancreatic cancer, glioblastoma, and metastases. Also, we review recent progress in clinical studies on polymeric micelles incorporating anticancer drugs. In addition, we introduce the next generation of polymeric micelles as the platform integrated with smart functionalities such as targetability, environmental sensitivity, and imaging properties. Thus, polymeric micelles can realize safe and effective cancer therapy, and offer tailor-made medicines for individual patients.

Utility of epirubicin-incorporating micelles tagged with anti-tissue factor antibody clone with no anticoagulant effect.

Tissue factor (TF), an initiator of the extrinsic blood coagulation cascade, is overexpressed in different types of cancer. Tissue factor overexpression is also known as a poor prognostic factor in pancreatic cancer. We recently developed anti-TF antibody (clone1849)-conjugated epirubicin-incorporating micelles (NC-6300), and reported that this anti-TF1849-NC-6300 showed enhanced antitumor activity against TF-high expressed human pancreatic cancer cells, when compared with NC-6300 alone. However, clone 1849 antibody inhibited TF-associated blood coagulation activity. We studied another anti-TF antibody, clone 1859, which had no effect on blood coagulation and prepared anti-TF1859-NC-6300. In addition, to determine the optimum size of the antibody fragment to conjugate with NC-6300, three forms of the 1859 antibody (whole IgG, F[ab']2 , and Fab') were conjugated to NC-6300. The antitumor effect of each anti-TF1859-NC-6300 was studied in vitro and in vivo, using two human pancreatic cancer cell lines, BxPC3 with high-expressed TF, and SUIT2 with low levels of TF. In vitro, all forms of anti-TF1859-NC-6300 showed higher cytocidal effects than NC-6300 in BxPC3, whereas this enhanced effect was not observed in SUIT2. Likewise, all forms of anti-TF1859-NC-6300 significantly suppressed tumor growth when compared to NC-6300 in the BxPC3, but not in the SUIT2, xenograft model. Among the three forms of conjugates, anti-TF1859-IgG-NC-6300 had a higher antitumor tendency in TF-high expressed cells. Thus, we have confirmed an enhanced antitumor effect of anti-TF1859-NC-6300 in a TF-high expressing tumor; anti-TF1859-IgG-NC-6300 could be used to simplify the manufacturing process of the antibody-micelle conjugation for future clinical studies.

Phase I study of NK105, a nanomicellar paclitaxel formulation, administered on a weekly schedule in patients with solid tumors.

Previous studies have established the rationale for NK105, a nanomicellar formulation of paclitaxel, administered every 3 weeks. The aim of this phase I study was to determine the recommended dose and pharmacokinetics of weekly administered NK105. NK105 was administered by a 30-min infusion once weekly for three consecutive weeks in each 4-week cycle. In the dose-escalation phase, three to seven patients with solid tumors were enrolled to each of the four dose levels (50-100 mg/m2; n = 16). At a dose level of 100 mg/m2, predefined dose-limiting toxicity (DLT) manifested in only one out of six evaluable patients, whereas a dose delay due to neutropenia during the first course occurred two patients. None of the three patients given 80 mg/m2 had a dose reduction, while a dose delay occurred in two. NK105 exhibited linear pharmacokinetics at doses of 50-100 mg/m2, and approximately 5 % of total paclitaxel was released from micelles. Thus, the recommended dose was set at 80 mg/m2, and an additional 10 advanced breast cancer (ABC) patients were given this dose in the dose-expansion phase. DLT manifested in two patients, and grade ≥ 3 neutropenia was found in eight patients. Among the nine patients who completed the first cycle, four had a dose reduction, mostly because of neutropenia. Of the 10 patients, six achieved partial response (PR), and four achieved stable disease (SD) status. Overall, weekly NK105 was well tolerated and had a desirable antitumor activity profile. Further investigations of NK105 in ABC patients are currently underway.

Antitumor effect of antitissue factor antibody-MMAE conjugate in human pancreatic tumor xenografts.

Tissue factor (TF) triggers the extrinsic blood coagulation cascade and is highly expressed in various types of cancer. In this study, we investigated the antitumor effect of an antibody-drug conjugate (ADC) consisting of an anti-TF monoclonal antibody and monomethyl auristatin E (MMAE). MMAE was conjugated to an anti-human TF or anti-mouse TF antibody using a valine-citrulline linker that could be potentially hydrolyzed by cathepsin B in the acidic environment of the lysosome. The cytotoxic and antitumor effects of the ADCs against four pancreatic cancer cell lines were analyzed. Both the ADC with the anti-human TF antibody and that with the anti-mouse TF antibody were stable under physiological conditions. The anti-human ADC was internalized in TF-expressing human tumor cell lines, followed by effective MMAE release. The half maximal inhibitory concentration (IC50 ) of MMAE was approximately 1 nM for all of the cell lines used. Meanwhile, the IC50 of anti-human ADC was 1.15 nM in the cell lines showing high TF expression, while exceeding 100 nM in the cells showing low TF expression levels. Anti-human ADC with passive and active targeting ability exerted significant suppression of tumor growth as compared to that observed in the saline group (p < 0.01). Also significant tumor growth suppressions were seen at the anti-mouse ADC and control ADC groups compared to the saline group (p < 0.01) due to EPR effect. Because various clinical human cancers express highly amount of TF, this new anti-TF ADC may deserve a clinical evaluation.