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.

Guidelines for clinical evaluation of anti-cancer drugs.

Clinical studies intended for regulatory approval must demonstrate the clinical benefits of the drug in a target population. Clinical development of a drug proceeds by stepwise clinical studies; after safety and pharmacokinetics are evaluated and the recommended dosage and administration are determined, efficacy and safety are evaluated in an exploratory manner, and finally clinical benefits are compared with conventional standard therapies. Guidelines for the clinical evaluation of anti-cancer drugs in Japan were established in 1991 and amended in 2006 after molecular-targeted drugs were introduced. Recent progress in the development of drugs acting on the immune system and cancer genomic medicine targeting rare but important molecular subtypes have altered the strategy for development of anti-cancer drugs. It is often difficult to conduct a confirmatory randomized controlled study using overall survival as the primary endpoint in rare molecular subtypes, and the primary evaluation of the efficacy of some drugs and subsequent approval is based on the tumor response. As conducting clinical studies for rare subtypes solely within Japan is difficult, drug development needs to be conducted within a global study. However, this requires robust monitoring to detect possible ethnic differences in pharmacokinetics and drug efficacy. Development using the conditional approval system for drugs enforced in 2020 may be considered, when clinical utility is evaluated based on surrogate endpoints. Because of these changes, we have revised the guidelines for the clinical evaluation of anti-cancer drugs in Japan. To promote global development of anti-cancer drugs involving Japan, the guidelines have been translated into English.

Durable Remission of Chemotherapy-Refractory Myeloid Sarcoma by Azacitidine.

Myeloid sarcoma is a rare disease entity of extramedullary myeloid neoplasm that can occur both as an initial isolated myeloid sarcoma without leukemic cell invasion in the peripheral blood and bone marrow, and as the secondary lesion of acute and chronic myeloid leukemias, myelodysplastic syndrome and chronic myeloproliferative neoplasms. Due to its rarity and its frequent emergence as the recurrent lesion after intensive systemic therapy, including allogeneic hematopoietic stem cell transplantation, the standard treatment has not been established for myeloid sarcoma. In this report, we presented an 84-year-old female patient with isolated myeloid sarcoma which progressed to myelodysplastic syndrome and systemic myeloid sarcoma despite various types of conventional anti-leukemic chemotherapies. However, the patient got a durable partial response by the monotherapy of azacitidine, a hypomethylating agent. She received thirteen courses of azacitidine therapy without progression. We discuss the possibility that hypomethylating agents are the novel effective and feasible therapeutic options for myeloid sarcoma, even in cases refractory to or relapsed after intensive systemic treatment. We also discuss the possible future development of hypomethylating agent-containing combinatory therapeutic strategy for myeloid sarcoma, given its direct anti-leukemic effect and immunomodulatory effect.

The study of rhenium pentacarbonyl complexes using single-atom chemistry in the gas phase.

A gas-phase chemical study of rhenium carbonyls was carried out using short-lived radioisotopes produced at a heavy-ion accelerator. The Re isotopes produced in the nuclear reactions of natGd(23Na,xn)172-177Re were pre-separated with a gas-filled recoil ion separator and their carbonyls were synthesized in a mixture of inert gas and carbon monoxide. Using a low temperature isothermal chromatography apparatus, the adsorption enthalpies of Re carbonyls were derived to be ΔHads = -42 ± 2 kJ mol-1 on a Teflon® surface by fitting the external chromatograms with a Monte Carlo simulation program. A chemical yield of 25% relative to that of the transport yield for Re by a He/KCl gas-jet was achieved. The laser-ablation time-of-flight mass-spectrometric technique was employed to identify the species of Re carbonyls produced in the gas phase. The most stable species was deduced to be Re(CO)5 based on the mass-spectrometric analysis as well as quantum chemistry calculations.

Gas-phase chemistry of ruthenium and rhodium carbonyl complexes.

Short-lived ruthenium and rhodium isotopes were produced from a (252)Cf spontaneous fission (SF) source. Their volatile carbonyl complexes were formed in gas-phase reactions in situ with the carbon-monoxide containing gas. A gas-jet system was employed to transport the volatile carbonyls from the recoil chamber to the chemical separation apparatus. The gas-phase chemical behaviors of these carbonyl complexes were studied using an online low temperature isothermal chromatography (IC) technique. Long IC columns made up of FEP Teflon were used to obtain the chemical information of the high-volatile Ru and Rh carbonyls. By excluding the influence of precursor effects, short-lived isotopes of (109-110)Ru and (111-112)Rh were used to represent the chemical behaviours of Ru and Rh carbonyls. Relative chemical yields of about 75% and 20% were measured for Ru(CO)5 and Rh(CO)4, respectively, relative to the yields of KCl aerosols transported in Ar gas. The adsorption enthalpies of ruthenium and rhodium carbonyl complexes on a Teflon surface were determined to be around ΔHads = -33(+1)(-2) kJ mol(-1) and -36(+2)(-1) kJ mol(-1), respectively, by fitting the breakthrough curves of the corresponding carbonyl complexes with a Monte Carlo simulation program. Different from Mo and Tc carbonyls, a small amount of oxygen gas was found to be not effective for the chemical yields of ruthenium and rhodium carbonyl complexes. The general chemical behaviors of short-lived carbonyl complexes of group VI-IX elements were discussed, which can be used in the future study on the gas-phase chemistry of superheavy elements - Bh, Hs, and Mt carbonyls.

Gas-phase chemistry of technetium carbonyl complexes.

Gas-phase chemical behaviors of short-lived technetium carbonyl complexes were studied using a low temperature isothermal chromatograph (IC) coupled with a (252)Cf spontaneous fission (SF) source. Fission products recoiled from the (252)Cf SF source were thermalized in a mixed gas containing CO, and then technetium carbonyl complexes were formed from reactions between CO gas and various technetium isotopes. A gas-jet system was employed to transport the volatile carbonyl complexes from a recoil chamber to the IC. Short IC columns made of Fluorinated Ethylene Propylene (FEP) Teflon and quartz were used to obtain chemical information about the technetium carbonyl complexes. The results for the (104)Tc-(106)Tc carbonyl complexes were found to be strongly influenced by the precursors, and showed the chemical behaviors of (104)Mo-(106)Mo carbonyl complexes, respectively. However, (107)Tc and (108)Tc could represent the chemical information of the element technetium due to their high independent yields and the very short half-lives of their precursors (107)Mo and (108)Mo. An adsorption enthalpy of about ΔHads = -43 kJ mol(-1) was determined for the Tc carbonyl complexes on both the Teflon and quartz surfaces by fitting the breakthrough curves of the (107)Tc and (108)Tc carbonyl complexes with a Monte Carlo simulation program. Chemical yields of around 25% were measured for the Tc carbonyl complexes relative to the transport yields obtained with the gas-jet transport of KCl aerosol particles with Ar carrier gas. Furthermore, the influence of a small amount of O2 gas on the yields of the Mo and Tc carbonyl complexes was studied.

Production cross sections of samarium-153 and -145 via alpha-particle-induced reactions on natural neodymium.

Production cross sections of 153,145Sm via alpha-particle-induced reactions on natNd were measured up to 23 MeV. The stacked-foil activation technique and high-resolution gamma-ray spectrometry were adopted for the measurement. The obtained cross sections were compared with the literature data and the TENDL-2019 and TENDL-2021 values. Physical thick target yields of the two radionuclides were derived from the measured cross sections.

Pharmacodynamic characterization of nitric oxide-mediated vasodilatory activity in isolated perfused rat mesenteric artery bed.

Vasodilation profiles following a short-term infusion of nitric oxide (NO), acetylcholine (ACh), and sodium nitroprusside (SNP) into an isolated perfused mesenteric artery bed were analyzed in rats to examine their vasodilatory efficacy under physiological conditions. These compounds commonly increase the intracellular NO concentration to exert vasodilatory activity. In an experiment with exogenous NO infusion where 100 µl of 1 : 300 diluted NO-saturated solution (approx. 53 pmol of NO) was applied, the infusion caused transient vasodilation in a dose-dependent manner, with the peak vasodilation value being 74.7% of the maximum relaxation value. In experiments with ACh, the peak vasodilation value was 81.5% of the maximum at a dose of 60 pmol. The vasodilation profile of ACh was similar to that of NO infusion, but the ACh-induced vasodilation reduced at a slower rate than that induced by NO infusion. The vasodilatory activity of SNP was less potent than that of ACh, and its peak value was 62.8% of the maximum at a dose of 2000 pmol. However, SNP activity was augmented by removing the vascular endothelia of the mesenteric artery bed, and the peak value reached 67.3% of the maximum at a dose of 60 pmol. Pharmacodynamic analysis indicated that NO and ACh are equivalent regarding their vasodilatory efficacy, while the efficacy of SNP was less than 1% of theirs, as the arterial vascular endothelium impeded intracellular SNP-related NO generation, by which 95% of SNP's vasodilatory efficacy was negated. These findings will be helpful to understand factors influencing the therapeutic efficacy of vasodilators.

Activation cross section measurement of alpha-particle induced reactions on natural neodymium.

Excitation functions of alpha-particle induced reactions on natNd up to 50 MeV were measured at the RIKEN AVF cyclotron. To derive cross sections activation method, stacked target technique and gamma-ray spectrometry were adopted. Formations of 153,145Sm, 151,150,149,148m,148g,144,143Pm, and 149,147Nd were investigated. The results were compared with the previous experimental data and the TENDL-2019 data. Discrepancies among most of them were found.

Production cross sections of 45Ti in the deuteron-induced reaction on 45Sc up to 24 MeV.

Activation cross sections of the medically interesting radionuclide 45Ti were investigated in the deuteron-induced reaction on 45Sc. 45Ti can be produced in a radioactive-contamination-free form in the 45Sc(d,2n)45Ti reaction below 15 MeV deuteron energy. The stacked foil activation technique and γ-ray spectrometry were used to determine the cross sections. The physical yield of 45Ti was deduced from the measured cross sections.

Stabilization of an 211At-Labeled Antibody with Sodium Ascorbate.

211At, an α-particle emitter, has recently attracted attention for radioimmunotherapy of intractable cancers. However, our sodium dodecyl sulfate polyacrylamide gel electrophoresis and flow cytometry analyses revealed that 211At-labeled immunoconjugates are easily disrupted. Luminol assay revealed that reactive oxygen species generated from radiolysis of water caused the disruption of 211At-labeled immunoconjugates. To retain their functions, we explored methods to protect 211At-immunoconjugates from oxidation and enhance their stability. Among several other reducing agents, sodium ascorbate most safely and successfully protected 211At-labeled trastuzumab from oxidative stress and retained the stability of the 211At-labeled antibody and its cytotoxicity against antigen-expressing cells for several days.

Co-precipitation behaviour of single atoms of rutherfordium in basic solutions.

All superheavy elements (SHEs), with atomic numbers (Z) ≥104, have been artificially synthesized one atom at a time and their chemical properties are largely unknown. Because these heavy nuclei have short lifetimes as well as extremely low production rates, chemical experiments need to be carried out on single atoms and have mostly been limited to adsorption and extraction. We have now investigated the precipitation properties of the SHE Rf (Z = 104). A co-precipitation method with samarium hydroxide had previously established that the co-precipitation behaviour of a range of elements reflected these elements' tendency to form hydroxide precipitates and/or ammine complex ions. Here we investigated co-precipitation of Rf in basic solutions containing NH3 or NaOH. Comparisons between the behaviour of Rf with that of Zr and Hf (lighter homologues of Rf) and actinide Th (a pseudo-homologue of Rf) showed that Rf does not coordinate strongly with NH3, but forms a hydroxide (co)precipitate that is expected to be Rf(OH)4.

Production cross sections of 68Ga and radioactive by-products in deuteron-induced reactions on natural zinc.

Activation cross sections of the deuteron-induced reactions on natural zinc are studied for the production of the medical radionuclide 68Ga. The stacked foil activation method and the γ-ray spectrometry were used. Co-produced radionuclides 65,66,67Ga, 63,65,69mZn, 61Cu, and 58Co are also investigated to evaluate amounts of impurities for practical use of 68Ga. Physical yields of the radionuclides were deduced from the measured cross sections.

Efficacy of peritoneal dialysis of tolbutamide in rats under conditions of the plasma unbound fraction being increased.

Peritoneal dialysis of a highly protein-bound compound, tolbutamide, was examined in rats to clarify whether the efficacy of the peritoneal dialysis of such compounds increases proportionally as their unbound fractions increase. As expected, it was shown that the tolbutamide concentration of the peritoneal dialysate rose as the unbound fraction of tolbutamide increased. However, the efficacy of peritoneal dialysis of tolbutamide was proportionally elevated only when the unbound fraction was slightly increased by sulfamethoxazole treatment. When the unbound fraction of tolbutamide was increased 7.8 times by sulfadimethoxine treatment, the dialysis efficacy was increased to only 58% of that expected. This discrepancy between the observed and expected values regarding dialysis efficacy was more marked when experiments were performed in rats with experimentally induced acute renal failure. Pharmacokinetic analysis indicated that the intrinsic dialysis clearance of tolbutamide decreased when its unbound fraction was greatly increased. These findings suggest that peritoneal dialysis may be mediated not only by passive diffusion, but also by concentration-dependent processes. The efficacy of the peritoneal dialysis of therapeutic compounds may be overestimated if the estimation is based only on their unbound fraction measured under control conditions.

Production cross sections of ytterbium and thulium radioisotopes in alpha-induced nuclear reactions on natural erbium.

Activation cross sections of alpha-induced reactions on natural erbium were measured using a 50.9-MeV alpha-beam at the RIKEN AVF cyclotron. Well-established methods for the measurements, the stacked-foil activation technique and gamma-ray spectrometry, were used. Production cross sections of 166,169Yb and 165,166,167,168,170,173Tm were determined. This is the first measurement of the cross sections of 166,170Tm. The integral yield of the medical radionuclide 169Yb was derived from the measured excitation function.

Capsaicin-induced increase of intestinal cefazolin absorption in rats.

The effect of capsaicin on intestinal cefazolin absorption was examined by means of an in situ closed loop method in rats to clarify whether the vanilloid receptor (TRPV1) is involved in drug absorption driven by passive diffusion. In control experiments with 1 mg/mL cefazolin, the amount of cefazolin absorbed from the closed loop was 15.3+/-1.5 microg/cm in the rat jejunum. The absorption amount was increased to 22.8+/-0.9 and 23.4+/-2.4 microg/cm when capsaicin was applied with cefazolin at concentrations of 10 and 400 microM, respectively. The enhancing effect of capsaicin on cefazolin absorption was suppressed when ruthenium red, a non-selective inhibitor of transient receptor potential (TRP) cation channels, was intravenously infused into the rat during the experiment. Cefazolin accumulation in the intestinal tissue was not altered in the presence of capsaicin. Collectively, the mechanism accounting for the capsaicin-induced increase in the intestinal cefazolin absorption is probably that capsaicin associating with TRPV1 increases the intrinsic permeability of cefazolin in intestine.

Alteration of therapeutic efficacy of lipid microspheres incorporating prostaglandin E1 by mixing with aqueous solution.

To clarify whether the therapeutic efficacy of lipid microspheres incorporating prostaglandin E(1) (lipo-PGE(1)) is altered when mixed and coinfused with clinical solutions, the original lipo-PGE(1) solution (20 microg/mL) was mixed with three clinical infusion solutions: 0.9% sodium chloride solution, Hartmann's solution, and fat emulsion for parenteral nutrition. These diluted lipo-PGE(1) (2 microg/mL) solutions were administered to rats, and their hemodynamic and antiplatelet effects were examined. Peripheral blood flow was increased by 76 +/- 4% from the control level when the lipo-PGE(1) solution diluted with the fat emulsion was administered, while it was increased by 43 +/- 6% and 36 +/- 7%, respectively, when the lipo-PGE(1) solutions diluted with 0.9% sodium chloride and Hartmann's solution were administered. As for the antiplatelet effects of the lipo-PGE(1) solutions, the progression of digit gangrene in thromboangiitis obliterans (TAO) rats was significantly suppressed by the administration of lipo-PGE(1) solution diluted with the fat emulsion, but it was not suppressed by lipo-PGE(1) solution diluted with 0.9% sodium chloride. These findings indicate that the therapeutic efficacy of lipo-PGE(1) is decreased when it is mixed with an aqueous solution such as 0.9% sodium chloride.

Evaluation of intramuscular lateral distribution profile of topically administered acetaminophen in rats.

To clarify to what extent topically administered drug molecules horizontally permeate into tissues surrounding the administration site, the intramuscular lateral concentration profile of acetaminophen was investigated in vivo using the microdialysis method in rats. When acetaminophen was intramuscularly administered for 6 h in a pinpoint manner at a constant rate of 3 microg/min, it was clearly detected in the muscle surrounding the administration site, being 17.5 microg/ml when measured at a 2 mm distance from the administration site. The concentration in the muscle was decreased as the distance increased, and those measured at 5 mm and 40 mm were 0.35 microg/ml and 0.09 microg/ml, respectively. In addition, it was shown that the concentration in the muscle at 40 mm reflected the compound's concentration in plasma, but not the compound's horizontal permeation from the administration site. With these observations, the intramuscular distribution profile of acetaminophen was numerically characterized according to Fick's law. As a result, it was revealed that horizontal permeation is the primary process accountable for the increased intramuscular concentration only in the area adjacent to the administration site, and the radius of the adjacent area was calculated to be 5.80 mm for acetaminophen.

Peritoneal dialysis alters tolbutamide pharmacokinetics in rats with experimental acute renal failure.

The plasma concentration profile of the antidiabetic agent tolbutamide was investigated in glycerol-induced acute renal failure (ARF) rats receiving or not receiving peritoneal dialysis (PD) to assess the impact of performing dialysis on tolbutamide pharmacokinetics. It was revealed that the plasma concentration of tolbutamide was decreased by 23.4% by performing PD in ARF rats, while it was not changed by PD in normal rats. The decrease in the plasma concentration of tolbutamide was nearly proportional to the increase in its volume of distribution. To clarify the mechanisms responsible for the decreased tolbutamide concentration caused by PD, the plasma protein binding of tolbutamide was examined in normal and ARF rats. The plasma unbound fraction of tolbutamide was higher in ARF rats than in normal rats, and the dissociation constants were 3.5+/-0.7 and 5.5+/-0.2 microg in normal and ARF rats, respectively. These results indicated that the unbound fraction of tolbutamide was increased in ARF rats because of its protein binding being suppressed. It is therefore likely that since a measurable amount of tolbutamide can distribute in peritoneal dialysate in ARF rats, but not in normal rats, the plasma concentration of tolbutamide was decreased by performing PD only in ARF rats. These findings suggest that diabetes medication with tolbutamide should be carefully performed in patients receiving dialysis treatment.