A model-based analysis to guide gonadotropin-releasing hormone receptor antagonist use for management of endometriosis.

AIMS: To identify linzagolix doses, an oral GnRH receptor antagonist, that effectively lower oestradiol (E2) to relieve endometriosis-related pelvic pain without compromising bone health. METHODS: Integrated statistical, pharmacokinetic-pharmacodynamic and systems pharmacology models were developed from Phase 1 and 2 clinical trial data in healthy volunteers and patients, receiving linzagolix 25-200 mg daily or placebo, and analysed simultaneously. The main outcome measures were pelvic pain scores for dysmenorrhoea, nonmenstrual pelvic pain (NMPP), uterine bleeding and lumbar spine bone mineral density (BMD). RESULTS: Linzagolix pharmacokinetics were described by a 2-compartment model with sequential zero/first-order absorption process (CL/F: 0.422 L/h). E2 changes over time were well described as a function of linzagolix 24-hour AUC (AUC50 : 1.68 × 105 ng h/mL). For a Caucasian reference patient, a change in E2 from 50-20 pg/mL at 24 weeks increased the odds of relief of dysmenorrhoea 1.33-fold and NMPP 1.07-fold (95% CI: 1.22-1.47 and 1.02-1.12, respectively) and decreased bleeding days by 1.55 (95% CI: 1.39-1.72). A previously validated quantitative systems pharmacology BMD model was adjusted to the clinical data. The mean week 24 lumbar spine BMD change from baseline ranged from -0.092% in the 50 mg dose, -1.30% in the 100 mg dose group and -2.67% in the 200 mg dose group. DISCUSSION: The previously-reported E2 target range (20-50 pg/mL) to balance efficacy and safety endpoints was confirmed. Linzagolix once daily doses between 75-125 mg daily were expected to meet endometriosis-associated pain, efficacy, and BMD loss targets in Caucasian patients.

The mechanism of action of oxytocin antagonist nolasiban in ART in healthy female volunteers.

RESEARCH QUESTION: What are the effects of the oxytocin receptor (OTR) antagonist nolasiban on uterine contractions, endometrial perfusion and endometrial mRNA expression? DESIGN: Randomized, double-blind, parallel-group, mechanism-of-action study with nolasiban. Forty-five healthy, pre-menopausal women were treated with placebo, 900 mg or 1800 mg nolasiban on the day corresponding to blastocyst transfer. Ultrasonographic uterine contraction frequency and endometrial perfusion were assessed, and endometrial biopsies analysed by next-generation sequencing. RESULTS: Both doses of nolasiban showed decreased contraction frequency and increased endometrial perfusion depending on the time point assessed. At 1800 mg, 10 endometrial genes (DPP4, CNTNAP3, CNTN4, CXCL12, TNXB, CTSE, OLFM4, KRT5, KRT6A, IDO2) were significantly differentially expressed (adjusted P < 0.05). Of these, OLFM4, DPP4 and CXCL12 were regulated in the same direction as genes involved in implantation during the window of implantation. In addition, three genes (DPP4, CXCL12 and IDO2) were associated with decidualization and endometrial receptivity. CONCLUSIONS: These data expand our knowledge of the mechanism of action of nolasiban in increasing pregnancy rates after embryo transfer. The results suggest more marked effects of nolasiban 1800 mg compared with the 900 mg dose, supporting testing at higher doses in IVF patients.

Confirmation of the cardiac safety of nolasiban in a randomised cohort of healthy female volunteers.

Nolasiban is an orally active oxytocin receptor antagonist being developed to increase the efficiency of assisted reproductive technologies. This study evaluated the pharmacokinetics, pharmacodynamics, and cardiac safety of nolasiban in 45 healthy women of child-bearing age. Nolasiban was administered in a fasted state with a standardised lunch served 4.5 h post-dose. Concentration-effect modelling was used to assess the effect of two dosages of nolasiban (900 mg and 1800 mg) on QTc following single-dose administration. We found no significant change in QTc at all tested dosages. Two-sided 90% confidence intervals of geometric mean Cmax for estimated QTc effects of nolasiban were below the threshold of regulatory concern. The sensitivity of the assay to detect small changes in QTc was confirmed by a significant shortening of QTc between 2 and 4 h after consumption of a meal, which served to validate the model. Independent of the nolasiban assessment, this study also explored the effects of sex hormones on ECG parameters, especially QT subintervals. We found a significant relationship between JTpc and oestradiol. Heart rate was negatively correlated with progesterone. This study confirms the cardiovascular safety of nolasiban and describes relationships of sex hormones and ECG parameters.

Effects of combined GnRH receptor antagonist linzagolix and hormonal add-back therapy on vaginal bleeding-delayed add-back onset does not improve bleeding pattern.

Linzagolix is a novel, oral GnRH receptor antagonist developed for the treatment of endometriosis and uterine fibroids. We assessed high-dose linzagolix safety and bleeding pattern effects in healthy women using combined versus delayed hormonal add-back therapy (ABT). This was a single-center, open-label, parallel-group study in 32 premenopausal women, who were randomized to daily linzagolix (200 mg)/ABT for 10 weeks ("Combined-ABT") or linzagolix (200 mg) for 4 weeks followed by linzagolix (200 mg)/ABT for 6 weeks ("Delayed-ABT"). Main outcome measures included bleeding records, trough estradiol (E2) concentrations and adverse events. Linzagolix alone promptly reduced bleeding, leading to amenorrhea in all women by week 5. When combined ABT was started (week 5), spotting (≤ 0.80 days/week/subject) and bleeding (≤ 0.53 days/week/subject) occurred; bleeding was markedly more frequent than after ABT start in the "Combined-ABT" group. In the "Combined-ABT" group, spotting (≤ 0.69 days/week/subject) and occasional bleeding (≤ 0.25 days/week/subject) occurred during the first half of treatment with a tendency to further decrease during the second half. Linzagolix alone rapidly reduced E2 reaching median week 4 levels of 4.1 pg/mL. Median E2 after combined linzagolix/ABT ranged between 35 and 42 pg/mL for the "Delayed-ABT" group (weeks 5-10) and between 24 and 32 pg/mL for the "Combined-ABT" group (weeks 1-10). Linzagolix was well tolerated. Most frequently reported adverse events were headache (32/156) and hot flushes (19/156). Hot flushes exclusively occurred in the "Delayed-ABT" group. In this study, treatment start with a combined linzagolix/ABT regimen resulted in better bleeding control, no hot flushes, and lower median E2 levels than a "Delayed-ABT" regimen. These results may help defining the linzagolix/ABT regimen to be adopted when treating sex-hormone-dependent diseases. Clinical Trial Registration Number-EudraCT Number: 2017-003822-34.

Efficient Design of Integrated and Adaptively Interlinked Protocols for Early-Phase Drug Development Programs.

BACKGROUND: Adaptive trial designs have the potential to address common challenges in drug development; they decrease timelines and costs of early drug development and efficiently create data that support future trials in target populations. While allowing for flexibility and evolution, adaptive strategies introduce some complexity to the design and implementation of trial protocols. Previously published work by the authors include a retrospective analysis of time savings using adaptive design and a systematic, 3- step methodology for writing early-phase adaptive integrated protocols. METHODS: This article builds on the authors' published work demonstrating the practical implementation of the adaptive protocol writing methodology and discussing the challenges and efficiencies. It describes the integration of an early development program of OBE022, a novel, oral, selective prostaglandin F2a receptor antagonist, intended as a treatment for preterm labor, using 2 interdependent, adaptive trial protocols. The program consisted of first-in-human single and multiple ascending dose parts with assessments of food effect, cardiac safety, proof of concept, and interactions of OBE022 with 4 standard of care medicines. RESULTS: The manuscript shows how the trials were tailored to OBE022's pharmacokinetic and pharmacodynamic characteristics and its therapeutic indication. The use of 2 large interdependent, adaptive protocols was facilitated by the United Kingdom's (UK's) regulatory environment and its acceptance of a rules-guided progression through the program. Changes to the planned trial conduct could be made without impacting on timelines, because they used predefined adaptive options within their authorized boundaries, and could therefore be made as nonsubstantial amendments. The program was successful and achieved its objectives. It was efficient and fast: it required a small number of participants (n=83) and completed from start of protocol writing to first draft of the clinical study report in just 11 months. CONCLUSIONS: This program included all key elements of early drug development in 2 interlinked protocols: the assessment of single and multiple ascending doses, food effect, cardiac safety and proof of concept. The approach described in this article demonstrates how early-phase programs can be designed to be performed, analyzed and reported time- and cost-efficiently.

Oxytocin Receptor Antagonists, Atosiban and Nolasiban, Inhibit Prostaglandin F2α-induced Contractions and Inflammatory Responses in Human Myometrium.

Oxytocin receptor antagonists (OTR-A) have been developed as tocolytics for the management of preterm labour due to the significant role of oxytocin (OT) in the onset of both term and preterm labour. Similar to OT, prostaglandins (PGs) play key roles in myometrial contractility and cervical ripening. Inhibition of PG synthesis/activity is used to delay preterm birth. Thus, targeting the PG pathway in combination with an OTR-A may be an effective strategy for delaying preterm delivery. In this study, we examined the effects of atosiban and nolasiban on PGF2α-induced contractions and pro-inflammatory responses in human pregnant myometrium. Both OTR-As, atosiban and nolasiban, inhibited PGF2α-induced contractions in a dose-dependent manner (p < 0.001 and p < 0.01, respectively). These inhibitory effects involved the suppression of PGF2α-mediated increase in intracellular calcium levels. In addition, the OTR-As significantly suppressed PGF2α-induced activation of pro-inflammatory pathways such as NF-κB and mitogen activated protein kinases (MAPKs), and the subsequent expression of contraction-associated-protein, COX-2. We have demonstrated that atosiban and nolasiban not only inhibit contractions elicited by OT, but also inhibit contractions and inflammation induced by PGF2α. This suggests a possible crosstalk between OTR and PG receptor signalling and highlights the importance of understanding G protein-coupled receptor interactions/crosstalk in the development of future tocolytics.

Coadministration of the prostaglandin F2α receptor antagonist preterm labour drug candidate OBE022 with magnesium sulfate, atosiban, nifedipine and betamethasone.

AIMS: To investigate presence or absence of clinically relevant drug interactions (pharmacokinetic and safety/tolerability) of OBE022 with standard-of-care medicines for preterm labour, enabling coadministration and further clinical development. METHODS: Part A: open-label, randomized, 3-period crossover assessing coadministration of single doses of OBE022 (1100 mg) and MgSO4 . Part B: open-label, single-sequence crossover assessing the interactions following administration of OBE022 (1000 mg/day) at steady state coadministered with single doses of atosiban, nifedipine and betamethasone. Twenty-five healthy nonpregnant women of reproductive age were enrolled (Part A: n = 12; Part B: n = 13). RESULTS: OBE022, alone or in combination with standard-of-care medications, was well tolerated. Headache and dizziness were the most frequently reported adverse events; dizziness occurred more often with the nifedipine/OBE022 combination. There were no clinically significant pharmacokinetic interactions when coadministered with MgSO4 . Co-administration had no notable effect on atosiban exposure. Atosiban reduced exposure to OBE002 (peak concentration [Cmax ] 22%, area under the concentration-time curve [AUC] 19%). Coadministration with betamethasone slightly increased betamethasone exposure (Cmax  + 18%, AUC +27%) and OBE002 exposure (Cmax  + 35%, AUC +15%). These changes were not considered clinically significant. Coadministration with nifedipine slightly increased OBE002 exposure (Cmax  + 29%, AUC +24%) and markedly increased nifedipine exposure (Cmax by 2-fold and AUC by 2-fold), which may be clinically significant. CONCLUSIONS: The use of OBE022, a PGF2α antagonist prodrug, in combination with standard-of-care medicines may provide new treatment alternatives for preterm labour. All tested combinations were well tolerated. Nifedipine doses could potentially be reduced or staggered when coadministered with OBE022.

Pharmacokinetics, safety and tolerability of OBE022, a selective prostaglandin F2α receptor antagonist tocolytic: A first-in-human trial in healthy postmenopausal women.

AIMS: Preterm birth remains a significant risk for later disability. The selective inhibition of the prostaglandin F2α receptor has significant advantages for a tocolytic. The prodrug OBE022 and its metabolite OBE002 are novel prostaglandin F2α receptor antagonists under development for treating preterm labour. METHODS: We performed a prospective, first in human, Phase I, dose escalation, placebo-controlled, randomized trial at a clinical trial site in the UK. Placebo, single ascending doses of 10, 30, 100, 300, 1000 or 1300 mg, and multiple ascending doses over 7 days of 100, 300 or 1000 mg day-1 ; were administered to postmenopausal female volunteers. Food interaction was additionally evaluated. RESULTS: Subjects tolerated OBE022 well at all single and multiple doses. No clinically relevant changes in safety parameters were shown and there were no serious adverse events. Observations showed that prodrug OBE022 was readily absorbed and rapidly converted into its equally active stable metabolite OBE002. The plasma level of OBE002 rose with increasing doses, reaching exposure levels that were anticipated to be clinically relevant within 1 h following administration. There was no clinically significant food interaction, with peak exposures reduced to 80% and area under the curve staying bioequivalent. The mean half-life of OBE002 ranged between 8 and 11 h following administration of a single dose and 22-29 h after multiple doses. CONCLUSIONS: Administration of OBE022 was safe and had favourable pharmacokinetic characteristics and no clinically relevant interaction with food. Our results allow further investigation of OBE022 in preterm labour patients.

OBE022, an Oral and Selective Prostaglandin F2α Receptor Antagonist as an Effective and Safe Modality for the Treatment of Preterm Labor.

Preterm birth is the major challenge in obstetrics, affecting ∼10% of pregnancies. Pan-prostaglandin synthesis inhibitors [nonsteroidal anti-inflammatory drugs (NSAIDs)] prevent preterm labor and prolong pregnancy but raise concerns about fetal renal and cardiovascular safety. We conducted preclinical studies examining the tocolytic effect and fetal safety of the oral prodrug candidate OBE022 [(S)-2-amino-3-methyl-butyric acid (S)-3-{[(S)-3-(biphenyl-4-sulfonyl)-thiazolidine-2-carbonyl]-amino}-3-(4-fluoro-phenyl)-propyl ester] and its parent OBE002 [(S)-3-(biphenyl-4-sulfonyl)-thiazolidine-2-carboxylic acid [(S)-1-(4-fluoro-phenyl)-3-hydroxy-propyl]-amide], both potent and highly selective antagonist of the contractile prostaglandin F2α (PGF2α ) receptor (FP). Efficacy of OBE022 and OBE002, alone and in combination with other tocolytics, was assessed in human tissues and pregnant animal models for inhibition of uterine contraction and delay of parturition. Selective safety of OBE022 and/or OBE002, compared with NSAID indomethacin, was assessed on renal function, closure of the ductus arteriosus, and inhibition of platelet aggregation. In in vitro studies, OBE002 inhibited spontaneous, oxytocin- and PGF2α -induced human myometrial contractions alone and was more effective in combination with atosiban or nifedipine. In in vivo studies, OBE022 and OBE002 reduced spontaneous contractions in near-term pregnant rats. In pregnant mice, OBE022 delayed RU486 [(8S,11R,13S,14S,17S)-11-[4-(dimethylamino)phenyl]-17-hydroxy-13-methyl-17-prop-1-ynyl-1,2,6,7,8,11,12,14,15,16-decahydrocyclopenta[a]phenanthren-3-one] -induced parturition and exerted synergistic effects in combination with nifedipine. OBE022 and/or OBE002 did not show the fetal side effects of ductus arteriosus constriction, impairment of kidney function, or inhibition of platelet aggregation observed with indomethacin. Orally active OBE022 and OBE002 exhibits potent tocolytic effects on human tissues ex vivo and animal models in vivo without causing the adverse fetal side effects seen with indomethacin. Selectively targeting the FP receptor in combination with existing tocolytics may be an effective strategy for preventing or delaying preterm delivery.

Confirmation of the Cardiac Safety of PGF2α Receptor Antagonist OBE022 in a First-in-Human Study in Healthy Subjects, Using Intensive ECG Assessments.

OBE022, a new orally active prostaglandin F2α  receptor antagonist (OBE022) with myometrial selectivity is being developed to reduce uterine contractions during preterm labor. This first-in-human study evaluated the effect of OBE022 following multiple doses on the QT interval in 23 healthy postmenopausal women, using the effect of a meal on QTc to demonstrate assay sensitivity. We report the cardiac safety outcome performed during the multiple ascending part of this trial. OBE022 was administered after a standardized breakfast on day 1 and in the fasted state from day 3 to day 9 wth a standardized lunch 4 hours after administration. Concentration-effect modeling was used to assess the effect of prodrug OBE022 and parent OBE002 on QTc after a single dose (days 1 and 3) and multiple doses (day 9). The concentration-response analysis showed the absence of QTc prolongation at all doses tested. Two-sided 90% confidence intervals of the geometric mean Cmax  for estimated QTc effects of OBE022 and OBE002 of all dose groups were consistently below the threshold of regulatory concern. The sensitivity of this study to detect small changes in the QTc was confirmed by a significant shortening of the QTc on days 1, 3, and 9 after standardized meals. This study establishes that neither prodrug OBE022 nor parent OBE002 prolong the QTc interval. The observed food effect on the QT interval validated the assay on all assessment days. Both the change from predose, premeal and the change from premeal, postdose demonstrated the specificity of the method.

Gonadotropin-Releasing Hormone Receptor Antagonist Mono- and Combination Therapy With Estradiol/Norethindrone Acetate Add-Back: Pharmacodynamics and Safety of OBE2109.

Context: OBE2109 is a potent, oral gonadotropin-releasing hormone receptor antagonist being developed for the treatment of sex-hormone-dependent diseases in women. Objective: We assessed the pharmacodynamics and safety of OBE2109 alone and combined with estradiol (E2)/norethindrone acetate (NETA) add-back therapy on E2 levels and vaginal bleeding. Design, Setting, and Participants: This was a single-center, open-label, randomized, parallel-group study in 76 healthy premenopausal women. Interventions: Women were randomly assigned to take the following doses (in milligrams) once daily for 6 weeks: OBE2109, 100 or 200; or OBE2109/E2/NETA, 100/0.5/0.1, or 100/1.0/0.5, or 200/1.0/0.5. Main Outcome Measures: E2 concentrations, bleeding pattern, exploratory bone metabolism biomarkers, and adverse events. Results: OBE2109 100 mg and 200 mg alone reduced E2 levels to reach median levels of 19.5 and 3.2 pg/mL, respectively, at week 4. Median E2 levels after combined OBE2109/add-back therapy ranged between 25 and 40 pg/mL. OBE2109 100 mg or 200 mg alone induced amenorrhea. By day 15, >85% of women had no vaginal bleeding during the last 4 weeks of treatment. Add-back therapy partially impaired bleeding control: The highest amenorrhea rate (53%) was observed with OBE2109 100 mg/1.0 mg/0.5 mg. The addition of E2/NETA, particularly at 1 mg/0.5 mg, mitigated the increase of two bone markers induced by OBE2109 200 mg. Conclusion: OBE2109 promptly lowered E2 levels. Add-back therapy may be required to prevent adverse effects on bone in women treated with the 200-mg dose (at 100 mg in some women). These results provide a basis for OBE2109 regimen selection to treat sex-hormone-dependent diseases.

Differential Effects of Oxytocin Receptor Antagonists, Atosiban and Nolasiban, on Oxytocin Receptor-Mediated Signaling in Human Amnion and Myometrium.

One of the most established roles of oxytocin (OT) is in inducing uterine contractions and labor. Apart from inducing contractions, our recent studies showed that OT can also activate proinflammatory pathways in both human myometrial and amnion cells, which suggests that the proinflammatory role of OT should be taken into account when developing tocolytics targeting the OT/oxytocin receptor (OTR) system. The OTR antagonist, atosiban, is currently used therapeutically for the treatment of preterm labor. We previously showed that atosiban fails to inhibit the proinflammatory effects of OT in human amnion; atosiban alone activates nuclear factor-κB (NF-κB) and mitogen activated protein kinases, thus upregulating downstream prolabor genes. In contrast with our findings with atosiban, the presence of the orally active OTR antagonist, nolasiban, reduced the effect of OT on NF-κB and p38 kinase activation in both myometrial and amnion cells. Consistent with the activation of these inflammatory mediators, OT led to increases in the expression of cyclooxygenase-2 and phosphorylated cytosolic phospholipase A2, which was reflected in prostaglandin E2 synthesis. Inhibition of NF-κB activation by nolasiban also translated to suppression of downstream prolabor gene expression, such as cyclooxygenase-2, C-C motif chemokine ligand 2, interleukin-6, and interleukin-8. We also demonstrated that nolasiban treatment alone has no significant stimulatory effect on both the myometrium and amnion. In conclusion, our findings indicate that nolasiban possesses promising potential as a novel tocolytic agent for both acute and maintenance therapy, as it inhibits both myometrial contractions and the proinflammatory effects of OT without the biased agonist effects.

Inferring the Chemotactic Strategy of P. putida and E. coli Using Modified Kramers-Moyal Coefficients.

Many bacteria perform a run-and-tumble random walk to explore their surrounding and to perform chemotaxis. In this article we present a novel method to infer the relevant parameters of bacterial motion from experimental trajectories including the tumbling events. We introduce a stochastic model for the orientation angle, where a shot-noise process initiates tumbles, and analytically calculate conditional moments, reminiscent of Kramers-Moyal coefficients. Matching them with the moments calculated from experimental trajectories of the bacteria E. coli and Pseudomonas putida, we are able to infer their respective tumble rates, the rotational diffusion constants, and the distributions of tumble angles in good agreement with results from conventional tumble recognizers. We also define a novel tumble recognizer, which explicitly quantifies the error in recognizing tumbles. In the presence of a chemical gradient we condition the moments on the bacterial direction of motion and thereby explore the chemotaxis strategy. For both bacteria we recover and quantify the classical chemotactic strategy, where the tumble rate is smallest along the chemical gradient. In addition, for E. coli we detect some cells, which bias their mean tumble angle towards smaller values. Our findings are supported by a scaling analysis of appropriate ratios of conditional moments, which are directly calculated from experimental data.

Active Brownian particles and run-and-tumble particles separate inside a maze.

A diverse range of natural and artificial self-propelled particles are known and are used nowadays. Among them, active Brownian particles (ABPs) and run-and-tumble particles (RTPs) are two important classes. We numerically study non-interacting ABPs and RTPs strongly confined to different maze geometries in two dimensions. We demonstrate that by means of geometrical confinement alone, ABPs are separable from RTPs. By investigating Matryoshka-like mazes with nested shells, we show that a circular maze has the best filtration efficiency. Results on the mean first-passage time reveal that ABPs escape faster from the center of the maze, while RTPs reach the center from the rim more easily. According to our simulations and a rate theory, which we developed, ABPs in steady state accumulate in the outermost region of the Matryoshka-like mazes, while RTPs occupy all locations within the maze with nearly equal probability. These results suggest a novel technique for separating different types of self-propelled particles by designing appropriate confining geometries without using chemical or biological agents.

Effects of the Oral Oxytocin Receptor Antagonist Tocolytic OBE001 on Reproduction in Rats.

BACKGROUND: OBE001 is a novel, orally active nonpeptide oxytocin receptor antagonist under development for the treatment of preterm labor and improvement in embryo implantation and pregnancy rate in assisted reproductive technology (ART). The reproductive safety of OBE001 was evaluated in customized fertility embryonic development (FER)/early embryonic development (EED) and fetal development (FD) and pre/postnatal development (PPN) studies mimicking clinical exposure scenarios. METHODS: Oral OBE001 was evaluated at doses of 37.5, 75, and 125 mg/kg/d in female rats during a FER/EED study (from premating to implantation) and throughout FD during a FD/PPN study. RESULTS: No OBE001 effects were observed during the FER/EED study. The FD/PPN study did not result in adverse OBE001 effects in females allowed to litter, their offspring, and second-generation fetuses. Females at 125 mg/kg/d who underwent cesarean section before term had slight reductions in body weights and food consumption, and associated fetuses had slightly delayed ossification of skull bones, which was not adverse in the absence of effects on live offspring. CONCLUSION: OBE001 at up to 125 mg/kg/d had no effects on EED and no adverse effects on FD and postnatal development of rats. These results constitute an important step toward the development of OBE001 in preterm labor and ART indications.

Emergence of collective changes in travel direction of starling flocks from individual birds' fluctuations.

One of the most impressive features of moving animal groups is their ability to perform sudden coherent changes in travel direction. While this collective decision can be a response to an external alarm cue, directional switching can also emerge from the intrinsic fluctuations in individual behaviour. However, the cause and the mechanism by which such collective changes of direction occur are not fully understood yet. Here, we present an experimental study of spontaneous collective turns in natural flocks of starlings. We employ a recently developed tracking algorithm to reconstruct three-dimensional trajectories of each individual bird in the flock for the whole duration of a turning event. Our approach enables us to analyse changes in the individual behaviour of every group member and reveal the emergent dynamics of turning. We show that spontaneous turns start from individuals located at the elongated tips of the flocks, and then propagate through the group. We find that birds on the tips deviate from the mean direction of motion much more frequently than other individuals, indicating that persistent localized fluctuations are the crucial ingredient for triggering a collective directional change. Finally, we quantitatively verify that birds follow equal-radius paths during turning, the effects of which are a change of the flock's orientation and a redistribution of individual locations in the group.

Self-phoretic active particles interacting by diffusiophoresis: A numerical study of the collapsed state and dynamic clustering.

Self-phoretic active colloids move and orient along self-generated chemical gradients by diffusiophoresis, a mechanism reminiscent of bacterial chemotaxis. In combination with the activity of the colloids, this creates effective repulsive and attractive interactions between particles depending on the sign of the translational and rotational diffusiophoretic parameters. A delicate balance of these interactions causes dynamic clustering and for overall strong effective attraction the particles collapse to one single cluster. Using Langevin dynamics simulations, we extend the state diagram of our earlier work (Phys. Rev. Lett. 112, 238303 (2014)) to regions with translational phoretic repulsion. With increasing repulsive strength, the collapsed cluster first starts to fluctuate strongly, then oscillates between a compact form and a colloidal cloud, and ultimately the colloidal cloud becomes static. The oscillations disappear if the phoretic interactions within compact clusters are not screened. We also study dynamic clustering at larger area fractions by exploiting cluster size distributions and mean cluster sizes. In particular, we identify the dynamic clustering 2 state as a signature of phoretic interactions. We analyze fusion and fission rate functions to quantify the kinetics of cluster formation and identify them as local signatures of phoretic interactions, since they can be measured on single clusters.

The clinical pharmacology and pharmacokinetics of ulipristal acetate for the treatment of uterine fibroids.

Uterine fibroids are benign hormone-sensitive tumors of uterine smooth muscle cells leading to heavy menstrual bleeding and pelvic pain. Ulipristal acetate (UPA) is an emerging medical treatment of fibroids with the potential to be used for long-term treatment. In this context, the present article summarizes UPA's main clinical pharmacology and pharmacokinetic (PK) properties. Ulipristal acetate has good oral bioavailability and a half-life allowing one single oral administration per day for the management of fibroids. As a steroid, UPA is a substrate for cytochrome P450 (CYP) 3A4 but does not act as an inducer or inhibitor of the CYP system or transporter proteins. With the exception of drugs modulating CYP3A4 activity, risks of drug-drug interactions with UPA are unlikely. In conclusion, besides its pharmacodynamic characteristics, UPA shows favorable PK properties that contribute to a good efficacy-safety ratio for the long-term management of uterine fibroids in clinical practice.

Finite-size scaling as a way to probe near-criticality in natural swarms.

Collective behavior in biological systems is often accompanied by strong correlations. The question has therefore arisen of whether correlation is amplified by the vicinity to some critical point in the parameters space. Biological systems, though, are typically quite far from the thermodynamic limit, so that the value of the control parameter at which correlation and susceptibility peak depend on size. Hence, a system would need to readjust its control parameter according to its size in order to be maximally correlated. This readjustment, though, has never been observed experimentally. By gathering three-dimensional data on swarms of midges in the field we find that swarms tune their control parameter and size so as to maintain a scaling behavior of the correlation function. As a consequence, correlation length and susceptibility scale with the system's size and swarms exhibit a near-maximal degree of correlation at all sizes.

Information transfer and behavioural inertia in starling flocks.

Collective decision-making in biological systems requires all individuals in the group to go through a behavioural change of state. During this transition fast and robust transfer of information is essential to prevent cohesion loss. The mechanism by which natural groups achieve such robustness, though, is not clear. Here we present an experimental study of starling flocks performing collective turns. We find that information about direction changes propagates across the flock with a linear dispersion law and negligible attenuation, hence minimizing group decoherence. These results contrast starkly with current models of collective motion, which predict diffusive transport of information. Building on spontaneous symmetry breaking and conservation laws arguments, we formulate a new theory that correctly reproduces linear and undamped propagation. Essential to the new framework is the inclusion of the birds' behavioural inertia. The new theory not only explains the data, but also predicts that information transfer must be faster the stronger the group's orientational order, a prediction accurately verified by the data. Our results suggest that swift decision-making may be the adaptive drive for the strong behavioural polarization observed in many living groups.