Thyroid function in patients with selenium deficiency exhibits high free T4 to T3 ratio.

Selenium, one of the essential trace minerals, is present in vivo in form of selenoproteins. Iodothyronine deiodinase, a selenoprotein, is involved in the activation and inactivation of thyroid hormone. Therefore, patients with selenium deficiency may present changes in thyroid hormone levels due to inhibition of T4 to T3 conversion; however, this assumption is still under debate. In the present study, we retrospectively investigated the thyroid function in 22 patients with selenium deficiency. Thyroid stimulating hormone (TSH) and free T4 (FT4) levels were increased in 3 (14%) and 5 (23%) patients, respectively, and free T3 (FT3) levels were decreased in 6 (27%) patients. The FT4/FT3 ratio was significantly higher in patients with selenium deficiency than that in the control group. There appeared to be a positive correlation between the decreased rate of selenium levels and FT4/FT3 ratio, thereby indicating that patients with severe selenium deficiency also exhibited abnormal thyroid hormone levels. Furthermore, when selenium was supplemented in seven patients with abnormal thyroid hormone levels, the TSH, FT4, and FT4/FT3 ratio were significantly decreased and FT3 levels were increased. Collectively, patients with selenium deficiency could present the characteristics of not only low FT3 but also high FT4 and FT4/FT3 ratio.

Emicizumab Improves Ex Vivo Clotting Function in Patients with Mild/Moderate Hemophilia A.

BACKGROUND: Emicizumab prophylaxis is a promising treatment that reduces bleeding events in severely affected patients with hemophilia A (PwHA). It is anticipated that emicizumab could be similarly effective in mild/moderate PwHA (PwMHA) although this effect has not been investigated. AIM: We evaluated ex vivo coagulant effects of emicizumabin PwMHA. METHODS: Clot waveform analysis (CWA) triggered by prothrombin time/activated partial prothrombin time-mixed reagents was utilized to examine coagulant effects of emicizumabin factor (F)VIII-deficient plasma mixed with recombinant (r)FVIIIand in native plasmas from 16 PwMHA. The CWA parameter, adjusted-|min1| (Ad|min1|), was used. Increases in Ad|min1| (ΔAd|min1|) mediated by emicizumab were calculated from the slopes of regression lines in the presence of rFVIII. RESULTS: Ad|min1| in FVIII-deficient plasma with various concentrations of rFVIII negatively correlated with ΔAd|min1|by adding emicizumab, and these data were defined as standard reference values. Ad|min1| (4.57 ± 0.50) in 16 PwMHA increased to 5.05 ± 0.54 and 5.37 ± 0.60 by adding emicizumab at 50 and 100 µg/mL, respectively, but remained lower than the normal range (7.22 ± 0.21). ΔAd|min1| levels were 1.5 to 2-fold higher in five cases and 0.4 to 0.6-fold lower in four cases, compared with reference values determined by rFVIII. In some cases, genetic analyses suggested that specific point mutations could have contributed to these findings. Further studies using rFVIII mutants indicated, however, that the differences in ΔAd|min1| were not related to individual FVIII gene defects. CONCLUSION: Emicizumab enhances coagulation potential in PwMHA. Assessment of ex vivo coagulant activity of emicizumab could be helpful for predicting coagulant potentials prior to treatment in these patients.

[Emicizumab, a bispecific antibody mimicking factor VIII: a novel alternative therapy for hemophilia A with inhibitors].

Regular prophylaxis using factor (F) VIII products to prevent bleeding in patients with hemophilia A (PWHAs) results in markedly suppressed onset of arthropathy and greatly contributes to improved quality of life. However, some issues remain with the use of clotting factor replacement therapy. The need for multiple intravenous infusions is associated with substantial mental and physical burden, and the inhibitor development results in difficulty of hemostatic management. To overcome these unmet needs, a recombinant humanized anti-FIXa/FX bispecific antibody mimicking FVIIIa function (emicizumab) was created. In phase 1/2 clinical studies, Japanese patients with PWHAs were treated with once-weekly subcutaneous administration of emicizumab. The annual bleeding rates were markedly reduced, irrespective of inhibitor use. A phase 3 global study for PWHA with inhibitor demonstrated a statistically significant efficacy, whereas thrombotic microangiopathy and thromboembolism were reported in 5 patients treated with emicizumab concomitantly with multiple infusions of activated prothrombin complex concentrates. In Japan, emicizumab (HEMLIBRA®) was approved for treatment of PWHAs with inhibitor on March 2018. In conclusion, emicizumab has promising features. Its subcutaneous bioavailability and long half-life (T1/2; approximately 30 days) enable effective bleeding prophylactic treatment at inhibitor status. Additional studies are warranted to establish clinical data on its safety and to define suitable assays for hemostatic monitoring.

Future prospects of hemostatic treatment for hemophilia patients.

In the treatment of hemophilia patients, factor (F) VIII or FIX product prophylaxis results in arthropathy prevention and quality of life (QOL) improvement. Serious issues concerning hemostatic treatment of hemophilia include frequent intravenous administration of products, inhibitor development, and hemostatic treatment of patients with inhibitors. To overcome these challenges, products with extended half-life were developed. Furthermore, alternative products based on new concepts of hemostatic therapy were developed. Regarding ACE910, a bispecific antibody recognizing FIX and FX, a clinical extension 1/2 study in Japan and an international phase 3 study are ongoing. Phase 1 results demonstrated that there were few severe ACE910-related adverse events. The t1/2 was approximately 30 days, and bleeding events were significantly reduced upon weekly subcutaneous administration in severe hemophilia A patients, independent of inhibitors. Two therapies, namely si-RNA anti-antithrombin therapy and anti-TFPI antibody therapy, aimed at rebalancing coagulation, are also under development. In addition, a gene therapy for hemophilia B has been developed by improving the vector. These new therapies could further improve the QOL of hemophilia patients.

A bispecific antibody mimicking factor VIII in hemophilia A therapy.

Serious issues in current hemostatic treatment of hemophilia A are the requirement for frequent intravenous administrations of factor (F) VIII, FVIII inhibitor development, and hemostatic treatment for patients with this inhibitor. For the purpose of overcoming these challenges, the FVIIIa-substituting bispecific antibody against FIXa/FX (ACE910, INN emicizumab) was produced. Emicizumab demonstrated marked hemostatic effects on both ongoing and spontaneous joint bleeding in the acquired hemophilia A primate model. The clinical phase 1 study designed to assess the pharmacokinetics, pharmacodynamics and safety of emicizumab has been initiated. Severe emicizumab-related adverse events were minimal. The t1/2 was approximately 30 days, and bleeding events were significantly decreased by weekly subcutaneous administration in severe hemophilia A patients, independently of the presence of the inhibitor. Currently, the phase 1/2 extension study is ongoing. We anticipate that emicizumab will show the benefits of prophylactic efficacy with subcutaneous administration at a much lower frequency.

Heparin-induced inhibitory effects of a prothrombin complex concentrate on global tests of haemostasis.

Prothrombin complex concentrates (PCC) have been used as bypassing agents for the treatment of haemophilia A patients with inhibitor as well as for replacement therapy in congenital and acquired deficiencies of vitamin-K-dependent clotting factors. The efficacy of PCC is variable, however, especially during long-term and high-dose use, and all currently available products of this nature contain heparin. We have examined the haemostatic properties of PCC using reconstituted whole blood made by mixing coagulation-factor-deficient plasma and washed blood cells. In rotation thromboelastometry (ROTEM), the recommended therapeutic dose of Proplex ST corrected the abnormal patterns. At higher concentrations, however, the ROTEM patterns regressed. In addition, specific assays of coagulation factors appeared unreliable in the presence of 2.5 U/ml Proplex ST; the abnormalities were corrected when protamine sulfate was added. The findings suggest that the presence of heparin in PCC might have a greater effect on global haemostasis. Careful attention to the anticoagulant effect as well as thrombogenicity of PCC is required. Monitoring therapy using such as ROTEM analysis could be highly informative.

pH-dependent association of factor VIII chains: enhancement of affinity at physiological pH by Cu2+.

Reconstitution of factor VIII from isolated heavy chain (HC) and light chain (LC) shows pH-dependence. In the presence of Ca2+, up to 80% of native factor VIII activity was recovered over a wide range of pH. In contrast, affinity of HC and LC was maximal at pH 6.5-6.75 (Kd approximately 4 nM), whereas a Kd approximately 20 nM was observed at physiological pH (7.25). The effect of Cu2+ (0.5 microM total Cu2+) on maximal activity regenerated was negligible at pH 6.25-8.0. However, this level of Cu2+ increased the inter-chain affinity by approximately 5-fold at pH 7.25. This effect resulted from an approximately 1.5-fold increased association rate constant (k(on)) and an approximately 3-fold reduced dissociation rate constant (k(off)). High affinity (Kd=5.3 fM) of the factor VIII heterodimer for Cu2+ was estimated by increases in cofactor activity. No significant increase in inter-chain affinity was observed when either isolated chain was reacted with Cu2+ followed by addition of the complementary chain. Together, these results suggest that the protonation state of specific residues modulates inter-chain affinity. Furthermore, copper ion contributes to the maintenance of the heterodimer at physiologic pH by a mechanism consistent with bridging the two chains.