Digital twins and Bayesian dynamic borrowing: Two recent approaches for incorporating historical control data.

Recent years have seen an increasing interest in incorporating external control data for designing and evaluating randomized clinical trials (RCT). This may decrease costs and shorten inclusion times by reducing sample sizes. For small populations, with limited recruitment, this can be especially important. Bayesian dynamic borrowing (BDB) has been a popular choice as it claims to protect against potential prior data conflict. Digital twins (DT) has recently been proposed as another method to utilize historical data. DT, also known as PROCOVA™, is based on constructing a prognostic score from historical control data, typically using machine learning. This score is included in a pre-specified ANCOVA as the primary analysis of the RCT. The promise of this idea is power increase while guaranteeing strong type 1 error control. In this paper, we apply analytic derivations and simulations to analyze and discuss examples of these two approaches. We conclude that BDB and DT, although similar in scope, have fundamental differences which need be considered in the specific application. The inflation of the type 1 error is a serious issue for BDB, while more evidence is needed of a tangible value of DT for real RCTs.

Mortality risk reduction with budesonide/glycopyrrolate/formoterol fumarate versus fluticasone furoate/umeclidinium/vilanterol in COPD: a matching-adjusted indirect comparison based on ETHOS and IMPACT.

OBJECTIVE: Chronic obstructive pulmonary disease (COPD) is a leading cause of death worldwide. While two approved fixed-dose inhaled corticosteroid/long-acting muscarinic antagonist (LAMA)/long-acting ß2-agonist (LABA) triple therapies reduce all-cause mortality (ACM) versus dual LAMA/LABA therapy in patients with COPD, head-to-head studies have not compared the effects of these therapies on ACM. We compared ACM in adults with moderate-to-very severe COPD receiving budesonide/glycopyrrolate/formoterol fumarate (BGF) in ETHOS versus fluticasone furoate/umeclidinium/vilanterol (FF/UMEC/VI) in IMPACT using a matching-adjusted indirect comparison (MAIC). METHODS: A systematic literature review identified two studies (ETHOS [NCT02465567]; IMPACT [NCT02164513]) of ≥52 weeks reporting ACM as an efficacy endpoint in patients receiving triple therapy. As ETHOS and IMPACT lack a common comparator, an unanchored MAIC compared ACM between licensed doses of BGF (320/18/9.6 µg) from ETHOS and FF/UMEC/VI (100/62.5/25 µg) from IMPACT in patients with moderate-to-very severe COPD. Using on- and off-treatment data from the final retrieved datasets of the intention-to-treat populations, BGF data were adjusted according to aggregate FF/UMEC/VI data using 11 baseline covariates; a supplementary unadjusted indirect treatment comparison was also conducted. P-values for these post-hoc analyses are not adjusted for Type I error. RESULTS: ACM over 52 weeks was statistically significantly reduced by 39% for BGF versus FF/UMEC/VI in the MAIC (hazard ratio [HR] [95% CI]: 0.61 [0.38, 0.95], p = 0.030) and unadjusted analysis (HR [95% CI]: 0.61 [0.41, 0.92], p = 0.019). CONCLUSION: In this MAIC, which adjusted for population heterogeneity between ETHOS and IMPACT, ACM was significantly reduced with BGF versus FF/UMEC/VI in patients with moderate-to-very severe COPD.

Chronic obstructive pulmonary disease (known as COPD) is a leading cause of death worldwide, being responsible for over 3 million deaths in 2019. People living with COPD are more likely to die. Importantly, a sudden worsening of COPD symptoms (known as an exacerbation) is associated with a higher chance of death from heart-related and breathing-related problems. Therefore, reducing risk of death is an important treatment goal for COPD. Of the three medications approved for treating COPD that combine three drugs in a single-inhaler device, there are two­referred to generically as budesonide/glycopyrrolate/formoterol fumarate (BGF) and fluticasone furoate/umeclidinium/vilanterol (FF/UMEC/VI)­that can reduce the risk of death in people living with COPD compared with treatments that combine two drugs. However, no studies have directly compared the risk of death in people living with COPD treated with these medicines. We compared the risk of death in people living with moderate-to-very severe COPD who received either BGF during a clinical trial called ETHOS or FF/UMEC/VI during a clinical trial called IMPACT. To make this comparison, we used a method called "matching-adjusted indirect comparison", which used specific features (such as sex, breathing difficulty, and whether they were current smokers) to match patients from the two studies to ensure similar groups were examined. Our analysis showed a 39% decrease in the chance of death in patients who received BGF compared with patients who received FF/UMEC/VI. This finding may be important for doctors to improve patient health and reduce the risk of death in people living with COPD.

BRICHOS domain of Bri2 inhibits islet amyloid polypeptide (IAPP) fibril formation and toxicity in human beta cells.

Aggregation of islet amyloid polypeptide (IAPP) into amyloid fibrils in islets of Langerhans is associated with type 2 diabetes, and formation of toxic IAPP species is believed to contribute to the loss of insulin-producing beta cells. The BRICHOS domain of integral membrane protein 2B (Bri2), a transmembrane protein expressed in several peripheral tissues and in the brain, has recently been shown to prevent fibril formation and toxicity of Aß42, an amyloid-forming peptide in Alzheimer disease. In this study, we demonstrate expression of Bri2 in human islets and in the human beta-cell line EndoC-ßH1. Bri2 colocalizes with IAPP intracellularly and is present in amyloid deposits in patients with type 2 diabetes. The BRICHOS domain of Bri2 effectively inhibits fibril formation in vitro and instead redirects IAPP into formation of amorphous aggregates. Reduction of endogenous Bri2 in EndoC-ßH1 cells with siRNA increases sensitivity to metabolic stress leading to cell death while a concomitant overexpression of Bri2 BRICHOS is protective. Also, coexpression of IAPP and Bri2 BRICHOS in lateral ventral neurons of Drosophila melanogaster results in an increased cell survival. IAPP is considered to be the most amyloidogenic peptide known, and described findings identify Bri2, or in particular its BRICHOS domain, as an important potential endogenous inhibitor of IAPP aggregation and toxicity, with the potential to be a possible target for the treatment of type 2 diabetes.

Dementia-related Bri2 BRICHOS is a versatile molecular chaperone that efficiently inhibits Aß42 toxicity in Drosophila.

Formation of fibrils of the amyloid-ß peptide (Aß) is suggested to play a central role in neurodegeneration in Alzheimer's disease (AD), for which no effective treatment exists. The BRICHOS domain is a part of several disease-related proproteins, the most studied ones being Bri2 associated with familial dementia and prosurfactant protein C (proSP-C) associated with lung amyloid. BRICHOS from proSP-C has been found to be an efficient inhibitor of Aß aggregation and toxicity, but its lung-specific expression makes it unsuited to target in AD. Bri2 is expressed in the brain, affects processing of Aß precursor protein, and increased levels of Bri2 are found in AD brain, but the specific role of its BRICHOS domain has not been studied in vivo Here, we find that transgenic expression of the Bri2 BRICHOS domain in the Drosophila central nervous system (CNS) or eyes efficiently inhibits Aß42 toxicity. In the presence of Bri2 BRICHOS, Aß42 is diffusely distributed throughout the mushroom bodies, a brain region involved in learning and memory, whereas Aß42 expressed alone or together with proSP-C BRICHOS forms punctuate deposits outside the mushroom bodies. Recombinant Bri2 BRICHOS domain efficiently prevents Aß42-induced reduction in γ-oscillations in hippocampal slices. Finally, Bri2 BRICHOS inhibits several steps in the Aß42 fibrillation pathway and prevents aggregation of heat-denatured proteins, indicating that it is a more versatile chaperone than proSP-C BRICHOS. These findings suggest that Bri2 BRICHOS can be a physiologically relevant chaperone for Aß in the CNS and needs to be further investigated for its potential in AD treatment.

Dissociation of a BRICHOS trimer into monomers leads to increased inhibitory effect on Aß42 fibril formation.

The BRICHOS domain is associated with human amyloid disease, and it efficiently prevents amyloid fibril formation of the amyloid ß-peptide (Aß) in vitro and in vivo. Recombinant human prosurfactant protein C (proSP-C) BRICHOS domain forms a homotrimer as observed by x-ray crystallography, analytical ultracentrifugation, native polyacrylamide gel electrophoresis, analytical size exclusion chromatography and electrospray mass spectrometry. It was hypothesized that the trimer is an inactive storage form, as a putative substrate-binding site identified in the monomer, is buried in the subunit interface of the trimer. We show here increased dissociation of the BRICHOS trimer into monomers, by addition of detergents or of bis-ANS, known to bind to the putative substrate-binding site, or by introducing a Ser to Arg mutation expected to interfere with trimer formation. This leads to increased capacity to delay Aß(42) fibril formation. Cross-linking of the BRICHOS trimer with glutaraldehyde, in contrast, renders it unable to affect Aß(42) fibril formation. Moreover, proSP-C BRICHOS expressed in HEK293 cells is mainly monomeric, as detected by proximity ligation assay. Finally, proteolytic cleavage of BRICHOS in a loop region that is cleaved during proSP-C biosynthesis results in increased capacity to delay Aß(42) fibril formation. These results indicate that modulation of the accessibility of the substrate-binding site is a means to regulate BRICHOS activity.

The chaperone domain BRICHOS prevents CNS toxicity of amyloid-ß peptide in Drosophila melanogaster.

Aggregation of the amyloid-ß peptide (Aß) into toxic oligomers and amyloid fibrils is linked to the development of Alzheimer's disease (AD). Mutations of the BRICHOS chaperone domain are associated with amyloid disease and recent in vitro data show that BRICHOS efficiently delays Aß42 oligomerization and fibril formation. We have generated transgenic Drosophila melanogaster flies that express the Aß42 peptide and the BRICHOS domain in the central nervous system (CNS). Co-expression of Aß42 and BRICHOS resulted in delayed Aß42 aggregation and dramatic improvements of both lifespan and locomotor function compared with flies expressing Aß42 alone. Moreover, BRICHOS increased the ratio of soluble:insoluble Aß42 and bound to deposits of Aß42 in the fly brain. Our results show that the BRICHOS domain efficiently reduces the neurotoxic effects of Aß42, although significant Aß42 aggregation is taking place. We propose that BRICHOS-based approaches should be explored with an aim towards the future prevention and treatment of AD.

High-resolution structure of a BRICHOS domain and its implications for anti-amyloid chaperone activity on lung surfactant protein C.

BRICHOS domains are encoded in > 30 human genes, which are associated with cancer, neurodegeneration, and interstitial lung disease (ILD). The BRICHOS domain from lung surfactant protein C proprotein (proSP-C) is required for membrane insertion of SP-C and has anti-amyloid activity in vitro. Here, we report the 2.1 Å crystal structure of the human proSP-C BRICHOS domain, which, together with molecular dynamics simulations and hydrogen-deuterium exchange mass spectrometry, reveals how BRICHOS domains may mediate chaperone activity. Observation of amyloid deposits composed of mature SP-C in lung tissue samples from ILD patients with mutations in the BRICHOS domain or in its peptide-binding linker region supports the in vivo relevance of the proposed mechanism. The results indicate that ILD mutations interfering with proSP-C BRICHOS activity cause amyloid disease secondary to intramolecular chaperone malfunction.

BRICHOS domain associated with lung fibrosis, dementia and cancer--a chaperone that prevents amyloid fibril formation?

The BRICHOS domain was initially defined from sequence alignments of the Bri protein associated with familial dementia, chondromodulin associated with chondrosarcoma and surfactant protein C precursor (proSP-C) associated with respiratory distress syndrome and interstitial lung disease (ILD). Today BRICHOS has been found in 12 protein families. Mutations in the Bri2 and proSP-C genes result in familial dementia and ILD, respectively, and both these conditions are associated with amyloid formation. Amyloid is of great medical relevance as it is found in several major incurable diseases, like Alzheimer's and Parkinson's disease and diabetes mellitus. Work on recombinant BRICHOS domains and transfected cells indicate that BRICHOS is a chaperone domain that, during biosynthesis, binds to precursor protein regions with high ß-sheet propensities, thereby preventing them from amyloid formation. Regions prone to form ß-sheets are present in all BRICHOS-containing precursor proteins and are probably eventually released by proteolytic cleavage, generating different peptides with largely unknown bioactivities. Recombinant BRICHOS domains from Bri2 and proSP-C have been found to efficiently prevent SP-C, the amyloid ß-peptide associated with Alzheimer's disease, and medin, found in aortic amyloid, from forming amyloid fibrils. The data collected so far on BRICHOS raise several interesting topics for further research: (a) amyloid formation is a potential threat for many more proteins than the ones recognized so far in amyloid diseases; (b) amyloid formation of widely different peptides involves intermediate(s) that are recognized by the BRICHOS domain, suggesting that they have distinct structural similarities; and (c) the BRICHOS domain might be harnessed in therapeutic strategies against amyloid diseases.

Heparan sulfate/heparin promotes transthyretin fibrillization through selective binding to a basic motif in the protein.

Transthyretin (TTR) is a homotetrameric protein that transports thyroxine and retinol. Tetramer destabilization and misfolding of the released monomers result in TTR aggregation, leading to its deposition as amyloid primarily in the heart and peripheral nervous system. Over 100 mutations of TTR have been linked to familial forms of TTR amyloidosis. Considerable effort has been devoted to the study of TTR aggregation of these mutants, although the majority of TTR-related amyloidosis is represented by sporadic cases due to the aggregation and deposition of the otherwise stable wild-type (WT) protein. Heparan sulfate (HS) has been found as a pertinent component in a number of amyloid deposits, suggesting its participation in amyloidogenesis. This study aimed to investigate possible roles of HS in TTR aggregation. Examination of heart tissue from an elderly cardiomyopathic patient revealed substantial accumulation of HS associated with the TTR amyloid deposits. Studies demonstrated that heparin/HS promoted TTR fibrillization through selective interaction with a basic motif of TTR. The importance of HS for TTR fibrillization was illustrated in a cell model; TTR incubated with WT Chinese hamster ovary cells resulted in fibrillization of the protein, but not with HS-deficient cells (pgsD-677). The effect of heparin on TTR fibril formation was further demonstrated in a Drosophila model that overexpresses TTR. Heparin was colocalized with TTR deposits in the head of the flies reared on heparin-supplemented medium, whereas no heparin was detected in the nontreated flies. Heparin of low molecular weight (Klexane) did not demonstrate this effect.