Fibrodysplasia ossificans progressiva (FOP) is an ultra-rare disorder, characterized by progressive heterotopic ossification (HO) and painful soft-tissue inflammatory flare-ups. This was a post-hoc analysis from a phase 2 (NCT03188666) trial in which adults with FOP received intravenous anti-activin A antibody garetosmab 10 mg/kg or placebo every 4 weeks over 28 weeks (Period 1), followed by a 28-week open-label treatment and extension (Period 2 and 3). Here we describe flare-ups, their relationship to new HO lesions, and the impact of garetosmab on flare-ups. Volume of new HO lesions was measured by computed tomography. Patient-reported flare-ups were defined by any two of: new onset of pain, swelling, joint stiffness, decrease in movement, or perceived presence of HO. Flare-ups were experienced by 71% (17/24) of placebo-treated patients, 59% (10/17) of whom developed a new HO lesion irrespective of flare-up location; 24% of flare-ups location-matched new HO lesions. Twenty-nine new HO lesions occurred in the placebo cohort by week 28, of which 12 (41%) occurred in the same location as new or ongoing flare-ups. A higher volume of newly formed heterotopic bone (week 28) occurred in placebo-treated patients who had experienced a prior flare-up versus those without (median [Q1:Q3] of 16.6 [12.0:31.1] cm3 versus 3.2 cm3). Garetosmab was previously shown to decrease patient-reported flare-up frequency in Period 1; here, garetosmab reduced the median (Q1:Q3) duration of patient reported flares (15.0 [6.0:82.0] versus 48.0 [15.0:1.00] days) and severity of flare-ups versus placebo. Frequency of corticosteroid use was numerically reduced in those treated with garetosmab (40.0%) versus placebo (58.3%). In this analysis, 71% of placebo-treated adults with FOP experienced flare-ups over 28 weeks, which were associated with an increased volume of newly formed heterotopic bone. Garetosmab reduced the severity and duration of flare-ups with effects sustained during the entire trial.
Fibrodysplasia ossificans progressiva (FOP) is a very rare genetic disorder caused by mutations in ACVR1, a gene that encodes for a receptor. In FOP, the mutated receptor is uniquely activated by activin A, a protein that binds ACVR1 (but does not normally activate it). When FOP-mutant ACVR1 is activated by activin A, this causes new bone to form in places where it does not usually develop. More specifically, in FOP, soft tissues (such as skeletal muscles) and connective tissues (such as tendons and ligaments) are gradually replaced by bone outside of the normal skeleton—a process referred to as heterotopic ossification (HO). In people with FOP, the build-up of bone impacts their mobility. Additionally, people with FOP also experience flare-ups, which are painful swellings of the soft tissues. This analysis investigated flare-up events, the relationship of flare-ups to new HO lesions, and the impact of garetosmab on flare-ups during a clinical trial that enrolled people with FOP. Garetosmab is a monoclonal antibody that binds to activin A and blocks it from activating the faulty receptor, hence stopping new heterotopic bone from forming. In this study, approximately half of the patients randomly received placebo and the other half randomly received garetosmab, the study drug. Of the people who received placebo, 71% experienced flare-ups and 59% percent of those who had flare-ups developed a new HO lesion irrespective of flare-up location. We previously reported that garetosmab decreases patient-reported flare-up frequency. In this study, we show that garetosmab also reduces the duration and severity of flare-ups, as well as the frequency of corticosteroid use with the treatment effect maintained for the entire trial.

Here, we report the clinical pharmacology data from LUMINA-1 (NCT03188666), a Phase 2 trial that evaluated garetosmab (a monoclonal antibody against activin A) in patients with fibrodysplasia ossificans progressiva. Forty-four patients were randomly assigned to intravenous 10 mg/kg of garetosmab or placebo every 4 weeks in a double-blind 28-week treatment period, followed by a 28-week open-label treatment period with garetosmab, and subsequent open-label extension. Serum samples were obtained to assess pharmacokinetics (PK), immunogenicity, and bone morphogenetic protein 9 (BMP9). Comparative exposure-response analyses for efficacy and safety were performed with trough concentrations (Ctrough ) of garetosmab prior to dosing. Steady-state PK was reached 12-16 weeks after the first dose of garetosmab, with mean (standard deviation) Ctrough of 105 ± 30.8 mg/L. Immunogenicity assessments showed anti-garetosmab antibody formation in 1 patient (1/43; 2.3%); titers were low, and did not affect PK or clinical efficacy. Median concentrations of BMP9 in serum were approximately 40 pg/mL at baseline. There were no meaningful differences in PK or BMP9 concentration-time profiles between patients who did and did not experience epistaxis or death. The comparative exposure-response analyses demonstrated no association between Ctrough and efficacy or safety. PK findings were consistent with prior data in healthy volunteers and were typical for a monoclonal antibody administered at doses sufficient to saturate target-mediated clearance. There were no trends that suggested patients with higher serum exposures to garetosmab were more likely to experience a reduction in heterotopic ossification or adverse events. Garetosmab is being further evaluated in the Phase 3 OPTIMA trial.

Cancer-associated cachexia (CAC) is a complex syndrome of progressive muscle wasting and adipose loss with metabolic dysfunction, severely increasing the morbidity and mortality risk in cancer patients. However, there are limited studies focused on the underlying mechanisms of the progression of CAC due to the complexity of this syndrome and the lack of preclinical models that mimics its stagewise progression.
We characterized the initiation and progression of CAC in transgenic female mice with ovarian tumours. We measured proposed CAC biomarkers (activin A, GDF15, IL-6, IL-1β, and TNF-α) in sera (n = 6) of this mouse model. The changes of activin A and GDF15 (n = 6) were correlated with the decline of bodyweight over time. Morphometry and signalling markers of muscle atrophy (n ≥ 6) and adipose tissue wasting (n ≥ 7) were assessed during CAC progression.
Cancer-associated cachexia symptoms of the transgenic mice model used in this study mimic the progression of CAC seen in humans, including drastic body weight loss, skeletal muscle atrophy, and adipose tissue wasting. Serum levels of two cachexia biomarkers, activin A and GDF15, increased significantly during cachexia progression (76-folds and 10-folds, respectively). Overactivation of proteolytic activity was detected in skeletal muscle through up-regulating muscle-specific E3 ligases Atrogin-1 and Murf-1 (16-folds and 14-folds, respectively) with decreasing cross-sectional area of muscle fibres (P < 0.001). Muscle wasting mechanisms related with p-p38 MAPK, FOXO3, and p-AMPKα were highly activated in concurrence with an elevation in serum activin A. Dramatic fat loss was also observed in this mouse model with decreased fat mass (n ≥ 6) and white adipocytes sizes (n = 6) (P < 0.0001). The adipose tissue wasting was based on thermogenesis, supported by the up-regulation of uncoupling protein 1 (UCP1). Fibrosis in adipose tissue was also observed in concurrence with adipose tissue loss (n ≥ 13) (p < 0.0001).
Our novel preclinical CAC mouse model mimics human CAC phenotypes and serum biomarkers. The mouse model in this study showed proteolysis in muscle atrophy, browning in adipose tissue wasting, elevation of serum activin A and GDF15, and atrophy of pancreas and liver. This mouse line would be the best preclinical model to aid in clarifying molecular mediators of CAC and dissecting metabolic dysfunction and tissue atrophy during the progression of CAC.

Disruption of normal intrauterine brain development is a significant consequence of premature birth and may lead to serious complications, such as neonatal brain injury (NBI). This prospective case-control longitudinal study aimed at determining the levels and prognostic value of serum activin A during the first three days of life in human premature neonates which later developed NBI. It was conducted in a single tertiary hospital and eligible participants were live-born premature (<34 weeks) neonates. Each case (n = 29) developed NBI in the form of an intraventricular haemorrhage, or periventricular leukomalacia, and was matched according to birth weight and gestational age to one neonate with normal head ultrasound scans. Serum activin A levels in both groups showed a stable concentration during the first three days of life as no difference was observed within the two groups from the first to the third day. Neonates diagnosed with NBI had significantly higher activin A levels during the first two days of life compared to control neonates and its levels correlated to the severity of NBI during the second and third day of life. Although serum activin A on the second day was the best predictor for neonates at risk to develop NBI, the overall predictive value was marginally fair (area under the ROC-curve 69.2%). Activin A, in combination with other biomarkers, may provide the first clinically useful panel for the early detection of premature neonates at high risk of NBI.

The aim of the present study was to investigate serum and urine levels of activin A in different moments of gestation, in primigravidae and in multigravidae, to understand whether these variables (biological sample and first gestation) affect activin A as a biomarker in pregnancy. We prospectively included 43 pairs of serum and urine samples from 25 women examined at different gestational ages (range 45 to 268 days). In the group of primigravidae (n = 16 samples from 9 participants), there was no significant change in serum activin A levels across gestation. Conversely, the group of multigravidae (n = 27 samples from 16 women) had higher serum activin A levels in the third trimester (2676 ± 840 pg/ml) compared to the first (583 ± 408 pg/ml) and second (1040 ± 384) trimesters (p = .025). Urine activin A concentrations did not differ between the two groups and did not change according to the gestation phase. There was no correlation between serum and urinary levels of activin A (r = 0.149, p = .359). These data suggest that activin A secretion may vary less during the first pregnancy, while urine activin A is unlikely to be a surrogate for the systemic levels of this hormone in pregnant women.

We describe outcomes from the first-in-human study of garetosmab (a fully human monoclonal antibody that inhibits activin A) under development for the treatment of fibrodysplasia ossificans progressiva (FOP). In a double-blind, placebo-controlled phase 1 study, 40 healthy women of nonchildbearing potential were randomized to receive a single dose of intravenous garetosmab 0.3, 1, 3, or 10 mg/kg; subcutaneous garetosmab 300 mg; or placebo. Serum concentrations of functional garetosmab (with ≥1 arm free to bind to target), total activin A, and antidrug antibodies were measured predose and up to 113 days post-first dose. Garetosmab demonstrated an acceptable safety profile with no dose-limiting toxicities. Garetosmab displayed nonlinear pharmacokinetics with target-mediated elimination. With increasing doses of intravenous garetosmab, mean peak concentration increased in a dose-proportional manner; mean steady-state estimates ranged from 41.4 to 47.8 mL/kg. A greater than dose-proportional increase in mean area under the concentration-time curve from time zero extrapolated to infinity (range, 72.2-7520 mg*day/L) was observed, consistent with decreasing mean clearance (range, 4.35-1.34 mL/day/kg). Following administration of intravenous garetosmab, mean concentrations of total activin A increased in a dose-dependent manner. At 10 mg/kg, total activin A levels reached a state of little or no change between weeks 4 and 12, suggesting saturation of the target-mediated pathway. No safety signals were seen in this study to preclude investigation in patients. Following intravenous administration, garetosmab concentrations decreased quickly, then decreased over time (reflecting linear elimination), and finally decreased in a nonlinear phase, reflecting target-mediated elimination. Results here support further investigation. Garetosmab 10 mg/kg every 4 weeks intravenously is being evaluated in patients with FOP (NCT03188666).

Inflammation, reflected by high plasma interleukin-6 concentration, is associated with acute kidney injury (AKI) in septic patients. Neutrophil activation has pathophysiological significance in experimental septic AKI. We hypothesized that neutrophil activation is associated with AKI in critically ill sepsis patients.
We measured plasma (n = 182) and urine (n = 118) activin A (a rapidly released cytosolic neutrophil protein), interleukin-8 (a chemotactic factor for neutrophils), myeloperoxidase (a neutrophil biomarker released in tissues), and interleukin-6 on intensive care unit admission (plasma and urine) and 24 hours later (plasma) in sepsis patients manifesting their first organ dysfunction between 24 hours preceding admission and the second calendar day in intensive care unit. AKI was defined by the Kidney Disease: Improving Global Outcomes criteria.
Plasma admission interleukin-8 (240 [60-971] vs 50 [19-164] pg/mL, P < .001) and activin A (845 [554-1895] vs 469 [285-862] pg/mL, P < .001) were but myeloperoxidase (169 [111-300] vs 144 [88-215] ng/mL, P = .059) was not higher among patients with AKI compared with those without. Urine admission interleukin-8 (50.4 [19.8-145.3] vs 9.5 [2.7-28.7] ng/mL, P < .001) and myeloperoxidase (7.7 [1.5-12.6] vs 1.9 [0.4-6.9] ng/mL, P < .001) were but activin A (9.7 [1.4-42.6] vs 4.0 [0.0-33.0] ng/mL, P = .064) was not higher in AKI than non-AKI patients. Urine myeloperoxidase correlated with urine interleukin-8 (R = .627, P < .001) but not with plasma myeloperoxidase (R = .131, P = .158).
Interleukin-8 in plasma and urine was associated with septic AKI. Elevated plasma activin A indicates intravascular neutrophil activation in septic AKI. Concomitant plasma and urine myeloperoxidase measurements suggest neutrophil accumulation into injured kidneys.

Hypertension is an important risk factor for cardiovascular disease. Activin A, a member of the transforming growth factor-β cytokine family, has been shown to regulate blood pressure through the renin-angiotensin system. However, the relationship between activin A and blood pressure remains uncertain. The objective of this study was to determine whether serum activin A levels are associated with blood pressure.
A total of 470 participants of I-Lan longitudinal Aging Study (ILAS) were eligible for this study. Serum levels of activin A were assessed by enzyme-linked immunosorbent assay. Cross-sectional analyses were performed, including comparisons of demographic characteristics, hypertensive status, and activin A levels.
Among the study participants (50% men, mean age, 69 years), 236 (50.2%) were hypertensive and 234 (49.8%) were normotensive. Hypertensive patients had significantly higher serum activin A levels than normotensives (normotensive vs. hypertensive: 507 ± 169 vs. 554 ± 176 pg/ml, mean ± SD, P < 0.001). All subjects were divided into 3 tertiles on the basis of serum activin A levels. Increasing tertiles of activin A were associated with higher systolic blood pressure (SBP), diastolic blood pressure and pulse pressure (PP) (all P < 0.001). After adjusting for all the potential confounding factors, serum activin A concentration was still significantly associated with SBP (P = 0.02) and PP (P = 0.03).
Serum activin A level was associated with SBP and PP. Further studies are required to assess their causal relationship and the clinical relevance.

Fibrodysplasia Ossificans Progressiva (FOP) is a rare inherited disease characterized by progressive heterotopic ossification. Disease onset, severity and symptoms vary between FOP patients, as does the frequency and activity of so-called flare-ups, during which tendons, ligaments, muscle and soft tissue are replaced by bone. Traumata, infections or other stressors are known inducers of flare-ups, and the hormone Activin A may be involved in disease activity; however, reliable biomarkers for FOP activity are missing, and the basal trace element and inflammatory state of patients are unknown. We hypothesized that FOP patients develop characteristic deficiencies in inflammation-related trace elements and display a chronically increased inflammatory cytokine level, collectively aggravating disease course and flare-up risk. Serum samples from 15 FOP patients and 25 relatives were collected under highest quality standards. Concentrations of Cu, Se and Zn were determined by total reflection X-ray fluorescence, and 27 cytokines along with Activin A by specific antibody-based techniques. Data were tested for normal distribution and analyzed by parametric or non-parametric tests. Concentrations of Se and Cu were not different between the groups, while Zn levels were slightly higher in FOP as compared to controls (1110±251 vs. 970±176ng/ml, P=0.04). The average concentrations of cytokines and Activin A were not different. When focusing on the two patients with self-reported flare-ups, again no obvious differences were noted. The cytokines Eotaxin, G-CSF, hbFGF and TNF-α were within the upper half of measured concentrations, and may warrant further longitudinal analyses. Our data do not support the hypothesis that FOP patients display a characteristic pattern of trace elements or have a generally increased tone of pro-inflammatory cytokines.

The deregulation of activin expression is often observed in various malignancies. Previous studies indicate that activin A plays a protumourigenic role in malignant pleural mesothelioma (MPM). The aim of the study was to evaluate circulating activin A level as a biomarker in MPM.
Plasma samples were collected from 129 MPM patients in four institutions at the time of diagnosis or before surgical resection. Samples from 45 healthy individuals and from 16 patients with non-malignant pleural diseases served as controls. Circulating activin A was measured by enzyme-linked immunosorbent assay and correlated to clinicopathological variables.
Plasma activin A level was significantly elevated in MPM patients (862 ± 83 pg/ml) when compared to healthy controls (391 ± 21 pg/ml; P < 0.0001). Patients with pleuritis or fibrosis only showed a modest increase (versus controls; 625 ± 95 pg/ml; P = 0.0067). Sarcomatoid (n = 10, 1629 ± 202 pg/ml, P = 0.0019) and biphasic (n = 23, 1164 ± 233 pg/ml, P = 0.0188) morphology were associated with high activin A levels when compared to epithelioid histology (n = 94, 712 ± 75 pg/ml). The tumour volume showed a positive correlation with increased circulating activin A levels. MPM patients with below median activin A levels had a significantly longer overall survival when compared to those with high activin A levels (median survival 735 versus 365 d, P < 0.0001). Importantly, circulating activin A levels were exclusively prognostic in epithelioid MPM.
Our findings suggest that the measurement of circulating activin A may support the histological classification of MPM and at the same time help to identify epithelioid MPM patients with poor prognosis.