EC 10246−2707: an eclipsing subdwarf B + M dwarf binary★

We announce the discovery of a new eclipsing hot subdwarf B + M dwarf binary, EC 10246-2707, and present multi-colour photometric and spectroscopic observations of this system. Similar to other HW Vir-type binaries, the light curve shows both primary and secondary eclipses, along with a strong reflection effect from the M dwarf; no intrinsic light contribution is detected from the cool companion. The orbital period is 0.118 507 993 6 ± 0.000 000 000 9 days, or about three hours. Analysis of our time- series spectroscopy reveals a velocity semi-amplitude of K1 = 71.6 ± 1.7 km s−1 for the sdB and best-fitting atmospheric parameters of Teff = 28900 ± 500 K, log g = 5.64 ± 0.06, and log N(He)/N(H) = -2.5 ± 0.2. Although we cannot claim a unique solution from modeling the light curve, the best–fitting model has an sdB mass of 0.45 M⊙ and a cool companion mass of 0.12 M⊙. These results are roughly consistent with a canonical–mass sdB and M dwarf separated by a ∼ 0.84 R⊙. We find no evidence of pulsations in the light curve and limit the amplitude of rapid photometric oscillations to 7.2×10−12. If EC 10246- 2707 evolves into a cataclysmic variable, its period should fall below the famous CV period gap

EC 10246-2707: a new eclipsing sdB + M dwarf binary⋆

We announce the discovery of a new eclipsing hot subdwarf B + M dwarf binary, EC 10246-2707, and present multi-colour photometric and spectroscopic observations of this system. Similar to other HW Vir-type binaries, the light curve shows both primary and secondary eclipses, along with a strong reflection effect from the M dwarf; no intrinsic light contribution is detected from the cool companion. The orbital period is 0.118 507 993 6 ± 0.000 000 000 9 days, or about three hours. Analysis of our time- series spectroscopy reveals a velocity semi-amplitude of K1 = 71.6 ± 1.7 km s−1 for the sdB and best-fitting atmospheric parameters of Teff = 28900 ± 500 K, log g = 5.64 ± 0.06, and log N(He)/N(H) = -2.5 ± 0.2. Although we cannot claim a unique solution from modeling the light curve, the best–fitting model has an sdB mass of 0.45 M⊙ and a cool companion mass of 0.12 M⊙. These results are roughly consistent with a canonical–mass sdB and M dwarf separated by a ∼ 0.84 R⊙. We find no evidence of pulsations in the light curve and limit the amplitude of rapid photometric oscillations to < 0.08%. Using 15 years of eclipse timings, we construct an O-C diagram but find no statistically significant period changes; we rule out | ˙P | > 7.2×10−12. If EC 10246- 2707 evolves into a cataclysmic variable, its period should fall below the famous CV period gap.Web of Scienc

Evidence for Diffuse Central Retinal Edema In Vivo in Diabetic Male Sprague Dawley Rats

Background: Investigations into the mechanism of diffuse retinal edema in diabetic subjects have been limited by a lack of animal models and techniques that co-localized retinal thickness and hydration in vivo. In this study we test the hypothesis that a previously reported supernormal central retinal thickness on MRI measured in experimental diabetic retinopathy in vivo represents a persistent and diffuse edema. Methodology/Principal Findings: In diabetic and age-matched control rats, and in rats experiencing dilutional hyponatremia (as a positive edema control), whole central retinal thickness, intraretinal water content and apparent diffusion coefficients (ADC, ‘water mobility’) were measured in vivo using quantitative MRI methods. Glycated hemoglobin and retinal thickness ex vivo (histology) were also measured in control and diabetic groups. In the dilutional hyponatremia model, central retinal thickness and water content were supernormal by quantitative MRI, and intraretinal water mobility profiles changed in a manner consistent with intracellular edema. Groups of diabetic (2, 3, 4, 6, and 9 mo of diabetes), and age-matched controls were then investigated with MRI and all diabetic rats showed supernormal whole central retinal thickness. In a separate study in 4 mo diabetic rats (and controls), MRI retinal thickness and water content metrics were significantly greater than normal, and ADC was subnormal in the outer retina; the increase in retinal thickness was not detected histologically on sections of fixed and dehydrated retinas from these rats

Comparative Analysis of Bispecific Antibody and Streptavidin-Targeted Radioimmunotherapy for B-cell Cancers

Streptavidin (SA)-biotin pretargeted radioimmunotherapy (PRIT) that targets CD20 in non-Hodgkin lymphoma (NHL) exhibits remarkable efficacy in model systems, but SA immunogenicity and interference by endogenous biotin may complicate clinical translation of this approach. In this study, we engineered a bispecific fusion protein (FP) that evades the limitations imposed by this system. Briefly, one arm of the FP was an anti-human CD20 antibody (2H7), with the other arm of the FP an anti-chelated radiometal trap for a radiolabeled ligand (yttrium[Y]-DOTA) captured by a very high-affinity anti-Y-DOTA scFv antibody (C825). Head-to-head biodistribution experiments comparing SA-biotin and bispecific FP (2H7-Fc-C825) PRIT in murine subjects bearing human lymphoma xenografts demonstrated nearly identical tumor targeting by each modality at 24 hours. However, residual radioactivity in the blood and normal organs was consistently higher following administration of 1F5-SA compared with 2H7-Fc-C825. Consequently, tumor-to-normal tissue ratios of distribution were superior for 2H7-Fc-C825 (P < 0.0001). Therapy studies in subjects bearing either Ramos or Granta subcutaneous lymphomas demonstrated that 2H7-Fc-C825 PRIT is highly effective and significantly less myelosuppressive than 1F5-SA (P < 0.0001). All animals receiving optimal doses of 2H7-Fc-C825 followed by 90Y-DOTA were cured by 150 days, whereas the growth of tumors in control animals progressed rapidly with complete morbidity by 25 days. In addition to demonstrating reduced risk of immunogenicity and an absence of endogenous biotin interference, our findings offer a preclinical proof of concept for the preferred use of bispecific PRIT in future clinical trials, due to a slightly superior biodistribution profile, less myelosuppression, and superior efficacy

Therapy of Myeloid Leukemia using Novel Bispecific Fusion Proteins Targeting CD45 and 90 Y-DOTA

© 2020 American Association for Cancer Research. Pretargeted radioimmunotherapy (PRIT) has been investigated as a multi-step approach to decrease relapse and toxicity for high-risk acute myeloid leukemia (AML). Relevant factors including endogenous biotin and immunogenicity, however, have limited the use of PRIT with an anti-CD45 antibody streptavidin conjugate and radiolabeled DOTA-biotin. To overcome these limitations we designed anti-murine and anti-human CD45 bispecific antibody constructs using 30F11 and BC8 antibodies, respectively, combined with an anti-yttrium (Y)-DOTA single-chain variable fragment (C825) to capture a radiolabeled ligand. The bispecific construct targeting human CD45 (BC8-Fc-C825) had high uptake in leukemia HEL xenografts [7.8 = 0.02% percent injected dose/gram of tissue (% ID/g)]. Therapy studies showed that 70% of mice with HEL human xenografts treated with BC8-Fc-C825 followed by 44.4 MBq (1,200 mCi) of 90Y-DOTA-biotin survived at least 170 days after therapy, while all nontreated controls required euthanasia because of tumor progression by day 32. High uptake at sites of leukemia (spleen and bone marrow) was also seen with 30F11-IgG1-C825 in a syngeneic disseminated SJL murine leukemia model (spleen, 9.0 = 1.5% ID/g and bone marrow, 8.1 = 1.2% ID/g), with minimal uptake in all other normal organs (<0.5% ID/g) at 24 hours after 90Y-DOTA injections. SJL leukemia mice treated with the bispecific 30F11-IgG1-C825 and 29.6 MBq (800 mCi) of 90Y-DOTA-biotin had a survival advantage compared with untreated leukemic mice (median, 43 vs. 30 days, respectively; P < 0.0001). These data suggest bispecific antibody–mediated PRIT may be highly effective for leukemia therapy and translation to human studies

A Novel Bispecific CD38 Antibody Eradicates Multiple Myeloma in a Mouse Model Following Yttrium-90-DOTA Capture

BACKGROUND: Despite high rates of initial response to immunomodulatory agents and proteasome inhibitors, the vast majority patients living with multiple myeloma (MM) will ultimately die of progressive disease that is a function of persistent MM cell clones. The radiosensitivity of malignant plasma cells is well documented in clinical settings, and we have previously reported the therapeutic efficacy of a streptavidin-biotin (SAB) pretargeted radioimmunotherapy (PRIT) system delivering the β-emitter 90Y to CD38 antigen targets (Green, et al. Cancer Res. 2014). While SAB-PRIT is capable of disease eradication in mouse models, SA immunogenicity and interference by endogenous biotin may complicate clinical translation of these findings into human trials. METHODS: To prospectively address these potential limitations and to further enhance therapeutic efficacy of PRIT, we engineered an anti-human CD38 xanti-chelated radiometal fusion protein (FP) specifically designed to trap second-step radiolabeled ligand (Y-DOTA) using a very high affinity anti-Y-DOTA scFv (C825). The bispecific anti-CD38 FP construct (028Fc-C825) expressed in CHO cells was affinity purified, assessed by gel filtration chromatography and binding specificity to both CD38 and Y-DOTA was confirmed. In vivo experiments showed the absence of toxicity of the bispecific construct at a dose range of 0.14-2.8 nmol per mouse (n=5/group). Biodistribution studies were performed in athymic nude mice (n=5/group) bearing s.c. luciferase transduced NCI-H929Luc human MM xenograft tumors. Animals received 2.8 nmol (420 µg) of either 028-Fc-C825 (anti-CD38 FP) or an irrelevant matched negative control bi-specific FP 2H7-Fc-C825 (anti-CD20 FP) with the same modular IgG-scFv structure (NCI-H929Luc are CD20 negative). The bispecific FP was administered 23 hours prior to a synthetic DOTAY-Dextran clearing agent (CA; 5 µg) and 24 hours prior to administration of trace labeled 90Y-DOTA (2 µg). In therapy studies, athymic nude mice (n=10/group) bearing s.c. NCI-H929Luc human MM xenograft tumors received 2.8 nmol of either 028-Fc-C825 (anti-CD38 FP) or 2H7-Fc-C825 (anti-CD20 FP) 23 hours prior to synthetic DOTAY-Dextran CA and 24 hrs prior to 90Y-DOTA (2 µg; 1200 µCi per mouse). An activity range of 800 µCi to 1200 µCi was previously identified as optimal in a MM xenograft model using the high energy beta particle emitter 90Y (t1/2 = 64 hours) [Green, et al. Cancer Res. 2014]. RESULTS: Selective tumor targeting of 90Y ligand to CD38+ xenografts was observed following administration of the bispecific anti-CD38 FP. Blood, tumor and nonspecific organ uptakes of 028-Fc-C825 demonstrated tumor-to-normal organ absorbed ratios that were 15:1; 17:1; 9:1; and 13:1, respectively for blood, lung, liver and kidney; compared to 0.7:1; 1:1; 1:1 and 0.5:1, respectively, in mice pretargeted with 2H7-Fc-C825 (control). The bispecific anti-CD38 FP also resulted in tumor-to-normal organ ratios of absorbed radioactivity that were superior to those measured in animals receiving anti-CD38 SAB-PRIT (OKT10-SA chemical conjugate) in the same study (5:1; 8:1; 5:1 and 2:1 for blood, lung, liver and kidney respectively). In therapy studies, no animal in any group lost >7% of initial body weight and by day 11 anti-CD38 bispecific FP treated animals were 102.4% ± 3.4% of baseline weight. All mice in the control bispecific FP group experienced exponential MM tumor growth and 100% of these control animals required euthanasia within 27 days. All mice pretargeted with 028-Fc-C825 (anti-CD38 bispecific FP) demonstrated tumor response by day 6. After 45 days, 100% of the anti-CD38 bispecific FP treated animals remained alive (Figure A) and objective remissions were observed within 18 days in 100% of the mice treated with 028-Fc-C825 followed by 1200 µCi of 90Y-DOTA, including 90% complete remissions (no detectable tumor in 028Fc-C825 treated mice) compared to tumors that were 2040 ± 1389% of initial tumor volume [p CONCLUSION: Biodistribution studies demonstrate MM tumor specific targeting after anti-CD38 xanti-chelated radiometal FP with minimal levels of yttrium-90 radioactivity detected in normal organs. Tumor responses are very encouraging in this MM xenograft model and results support clinical evaluation of bispecific anti-CD38 FP PRIT in MM. Disclosures No relevant conflicts of interest to declare