Search

Emerging treatment options for hemophilia, including gene therapy, modified factor products, antibody-based products, and other nonreplacement therapies, are in development or on their way to marketing authorization. For proof of efficacy, annual bleeding rates (ABRs) have become an increasingly important endpoint in hemophilia trials. We hypothesized that ABR analyses differ substantially between and within medicinal product classes and that the ABR observation period constitutes a major bias. For ABR characterization, an internal factor VIII (FVIII) treatment database has been built based on confidential clinical trial data submitted to the Paul-Ehrlich-Institut (PEI). Furthermore, anonymized data from 46 trial protocols submitted for review to the PEI were analyzed (FVIII replacement, n = 27; antibody-based, n = 12; and gene therapy, n = 7) for methodology. Definitions of bleeding episodes and ABR observational periods differed substantially in clinical trials. In the initial observation phase, individual ABRs of patients, treated prophylactically for 1 year, vary by about 40% (P < 0.001), which finally led to a significant reduction of the ABR group mean by 20% (P < 0.05). Furthermore, the high variance in ABRs constitutes a major challenge in statistical analyses. In conclusion, considerable heterogeneity and bias in the ABR estimation in clinical trials was identified, which makes it substantially more difficult to compare the efficacy of different treatment regimens and products. Thus, awareness of the important pitfalls when using ABR as a clinical outcome is needed in the evaluation of hemophilia therapies for patients, physicians, regulators, and health technology assessment agencies.

Due to the outbreak of the coronavirus disease 2019 (COVID-19) pandemic, clinical trial (CT) research for efficacy and safety evaluation of convalescent plasma (CP) accelerated globally. In trial planning and approval, clinical researcher and regulatory agencies worldwide are challenged by limited evidence from the use of convalescent plasma in previous outbreaks of viral diseases and by different possible study approaches. We analyzed CT designs to identify potential opportunities for data aggregation and to facilitate generation of decision-relevant evidence.

There is a broad range of factor products approved in Germany for haemophilia A treatment. Since the introduction of recombinant coagulation factor VIII (FVIII) products in the 1990s, there has been substantial debate whether there is a difference in inhibitor incidence between single FVIII products or product classes. Neither haemophilia registries nor clinical studies, including a randomised controlled clinical trial, provided a consistent and definite answer. The reasons were mainly related to methodological challenges in conducting controlled studies in a rare disease. In this analysis, the most relevant epidemiological challenges and main problems were examined, including study bias, potential overlap of individual studies and advanced development of therapy and methods in the course of time. Meta-analyses on two levels showed that therapies using recombinant products resulted in different event rates when compared to plasma-derived products. These results are accompanied by substantial study heterogeneity evidenced by Cochran’s Q tests. Only three studies have been identified that meet the standards of current clinical guidance. To finally resolve this ongoing and disputable safety issue of replacement therapy, collaboration among registry owners, academia and regulators must be fostered.

Aims The benefit of the β1-adrenergic receptor (β1-AR) agonist dobutamine for treatment of acute heart failure in peripartum cardiomyopathy (PPCM) is controversial. Cardiac STAT3 expression is reduced in PPCM patients. Mice carrying a cardiomyocyte-restricted deletion of STAT3 (CKO) develop PPCM. We hypothesized that STAT3-dependent signalling networks may influence the response to β-AR agonist treatment in PPCM patients and analysed this hypothesis in CKO mice. Methods and results Follow-up analyses in 27 patients with severe PPCM (left ventricular ejection fraction ≤25%) revealed that 19 of 20 patients not obtaining dobutamine improved cardiac function. All seven patients obtaining dobutamine received heart transplantation (n = 4) or left ventricular assist devices (n = 3). They displayed diminished myocardial triglyceride, pyruvate, and lactate content compared with non-failing controls. The β-AR agonist isoproterenol (Iso) induced heart failure with high mortality in postpartum female, in non-pregnant female and in male CKO, but not in wild-type mice. Iso induced heart failure and high mortality in CKO mice by impairing fatty acid and glucose uptake, thereby generating a metabolic deficit. The latter was governed by disturbed STAT3-dependent signalling networks, microRNA-199a-5p, microRNA-7a-5p, insulin/glucose transporter-4, and neuregulin/ErbB signalling. The resulting cardiac energy depletion and oxidative stress promoted dysfunction and cardiomyocyte loss inducing irreversible heart failure, which could be attenuated by the β1-AR blocker metoprolol or glucose-uptake-promoting drugs perhexiline and etomoxir. Conclusions Iso impairs glucose uptake, induces energy depletion, oxidative stress, dysfunction, and death in STAT3-deficient cardiomyocytes mainly via β1-AR stimulation. These cellular alterations may underlie the dobutamine-induced irreversible heart failure progression in PPCM patients who frequently display reduced cardiac STAT3 expression.

Electron cryomicroscopy reveals the three-dimensional structure of F-actin at a resolution of 3.7 A in complex with tropomyosin at a resolution of 6.5 A; the stabilizing interactions and the effects of disease-causing mutants are also investigated. Filamentous actin (F-actin) — a main component of the cytoskeleton — is the major protein of thin filaments in the muscle. The binding of the motor protein myosin to F-actin is mediated by another protein called tropomyosin, which also binds to F-actin in smooth muscle and in non-muscle cells, stabilizing and regulating these filaments. Using electron cryomicroscopy, Stefan Raunser and colleagues have obtained the first high-resolution, three-dimensional structure of F-actin in complex with tropomyosin. The structure reveals the interactions that stabilize the F-actin and sheds light on the possible effect of prominent disease-causing mutations. Comparison of the F-actin structure with the crystal structure of monomeric (G)-actin reveals conformational changes associated with filament formation. Filamentous actin (F-actin) is the major protein of muscle thin filaments, and actin microfilaments are the main component of the eukaryotic cytoskeleton. Mutations in different actin isoforms lead to early-onset autosomal dominant non-syndromic hearing loss1, familial thoracic aortic aneurysms and dissections2, and multiple variations of myopathies3. In striated muscle fibres, the binding of myosin motors to actin filaments is mainly regulated by tropomyosin and troponin4,5. Tropomyosin also binds to F-actin in smooth muscle and in non-muscle cells and stabilizes and regulates the filaments there in the absence of troponin6. Although crystal structures for monomeric actin (G-actin) are available7, a high-resolution structure of F-actin is still missing, hampering our understanding of how disease-causing mutations affect the function of thin muscle filaments and microfilaments. Here we report the three-dimensional structure of F-actin at a resolution of 3.7 A in complex with tropomyosin at a resolution of 6.5 A, determined by electron cryomicroscopy. The structure reveals that the D-loop is ordered and acts as a central region for hydrophobic and electrostatic interactions that stabilize the F-actin filament. We clearly identify map density corresponding to ADP and Mg2+ and explain the possible effect of prominent disease-causing mutants. A comparison of F-actin with G-actin reveals the conformational changes during filament formation and identifies the D-loop as their key mediator. We also confirm that negatively charged tropomyosin interacts with a positively charged groove on F-actin. Comparison of the position of tropomyosin in F-actin–tropomyosin with its position in our previously determined F-actin–tropomyosin–myosin structure8 reveals a myosin-induced transition of tropomyosin. Our results allow us to understand the role of individual mutations in the genesis of actin- and tropomyosin-related diseases and will serve as a strong foundation for the targeted development of drugs.

Mutation-induced dysfunction or misfolding of heart muscle sarcomere components have been linked to dilated and hypertrophic cardiomyopathies. We have previously shown that the small molecule EMD57033 increases β-cardiac myosin activity and acts as a pharmacological chaperone that stabilizes and refolds the motor domain. Following up on this finding, we investigated whether metabolites such as fatty acids can have a similar effect on β-cardiac myosin. Arachidonic acid (AA) was previously reported as an activator of smooth muscle myosin. We found that among all fatty acids tested, AA induced the largest effect on actin-activated ATPase activity of β-cardiac myosin. Closer characterization revealed a 13-fold increase in β-cardiac myosins affinity for actin in the presence of ATP and a 7-fold increase in the rate of phosphate release. We further aimed to elucidate the effect of AA-induced myosin activation in the context of a reconstituted human cardiac actin-troponin-tropomyosin complex. Both, assays monitoring ATPase and in vitro motility showed a significant increase in activity over a wide range of Ca2+ concentrations. Similar to the effect of EMD57033, the addition of AA increases the stability of myosin and reverses the loss of myosin activity caused by temperature stress. The refolding reaction can be monitored by the recovery of the intrinsic protein fluorescence signal that is associated with ATP binding and active turnover. Alternatively, we followed the clear reduction in the number of immobile filaments following the addition of AA.