Ralinepag Phase II Open-Label Extension Study in Patients with Pulmonary Arterial Hypertension.

INTRODUCTION: Ralinepag is a potent, titratable, orally administered prostacyclin (IP) receptor agonist to treat pulmonary arterial hypertension. A phase II randomized, double-blind, parallel-group, placebo-controlled, 22-week study of immediate-release (IR) ralinepag safety and efficacy met its primary endpoint, significantly reducing pulmonary vascular resistance (PVR) compared with placebo. This phase II open-label extension (OLE) study assessed long-term safety and tolerability of ralinepag. METHODS: Participants were eligible for the OLE if they completed the parent study or experienced a clinical worsening event while receiving placebo. Those previously receiving IR ralinepag remained on their current dose, and participants formerly administered placebo were titrated to the highest tolerated dose. Participants were transitioned to an extended-release ralinepag formulation toward the end of the OLE. The primary objective evaluated long-term safety and tolerability; secondary endpoints included changes in 6-min walk distance (6MWD), World Health Organization/New York Heart Association functional class, clinical worsening, and hemodynamic measures. RESULTS: In total, 45/61 participants enrolled in the OLE study, 30 from the IR ralinepag group and 15 from the placebo group. The most common adverse events (AEs) were known prostacyclin-related effects (e.g., headache, 64.4%; diarrhea, 37.8%; jaw pain, 33.3%). There was a notable decline in AEs after reaching and maintaining a stable dose. At month 24 after entering the OLE, 6MWD significantly increased by a mean of 36.3 m (P = 0.004) from OLE baseline, and most participants remained stable in their functional class (84.8%). Post-baseline PVR in 1 or 2 years decreased by a median of 52.2 dyn.s/cm5 and mean pulmonary arterial pressure decreased by a median of 2.0 mmHg (P = 0.05). CONCLUSION: Ralinepag produced sustained, durable improvements in 6MWD along with durable reductions in PVR and a manageable AE profile. Most participants continuing treatment with ralinepag maintained functional measures throughout the OLE and those switching from placebo to ralinepag often experienced functional improvements.

Pulmonary arterial hypertension is a rare disease caused by elevated pressure in the blood vessels connecting the heart to the lungs. A previous phase 2 study found that ralinepag significanlty reduced pulmonary vascular resistance (the force or resistance that blood encounters as it flows through the blood vessels in the lungs) compared with placebo. This clinical study of 45 patients investigated whether ralinepag was safe and effective for long-term use to treat people with pulmonary arterial hypertension. All participants received ralinepag twice daily until a new once daily pill was available later in the study. The primary endpoints were long-term safety and tolerability, and secondary endpoints included exercise capacity, impact on daily life (functional class), clinical worsening, and hemodynamic measures (metrics to measure how well the heart is working). The study found that ralinepag had a manageable side effect profile, with a decrease in side effects for patients who continued taking ralinepag over time. Moreover, the study showed that ralinepag improved the ability to exercise, maintained functional measures, and helped to reduce pressure in the blood vessels connecting the heart to the lungs over a 24-month period for participants with pulmonary arterial hypertension.

Pharmacokinetics of Oral Treprostinil in Children With Pulmonary Arterial Hypertension.

As part of a clinical trial, this study examined the pharmacokinetics (PK) of oral treprostinil (TRE) in children with pulmonary arterial hypertension. The trial consisted of the following 3 cohorts: transition from parenteral (cohort 1) or inhaled (cohort 2) TRE, or de novo addition (cohort 3). Oral TRE was dosed 3 times daily. PK samples were obtained before an oral TRE dose, and at 2, 4, 6, and 8 hours thereafter. The PK parameters were calculated using noncompartmental analysis. Thirty-two children (n = 10 in cohorts 1 and 2, n = 12 in cohort 3) were enrolled; the median age was 12 years (range 7-17 years), and the median weight was 42.2 kg (range 19.3-78 kg). The median oral TRE dose for all subjects was 3.8 mg (5.9, 3.5, and 4.0 mg for cohorts 1, 2, and 3, respectively). The TRE concentration versus time profile demonstrated a peak concentration at a median of 3.8 hours with wide variability. In cohort 1, oral dosing led to higher peak (5.9 ng/mL) and lower trough (1 ng/mL) concentrations than parenteral (peak 5.4 ng/mL and trough 4.2 ng/mL), but a lower mean concentration (3.61 vs. 4.46 ng/mL), likely due to variable metabolism and noncomparable dosing. Both the area under the curve and average concentration were linearly correlated with oral TRE dose and dose normalized to body weight, but not with weight or age alone. In pediatric patients, an increased oral TRE dose or dose frequency may be required to minimize PK variability and achieve greater correlation with parenteral dosing.

Oral treprostinil in transition or as add-on therapy in pediatric pulmonary arterial hypertension.

Treprostinil, a prostacyclin analogue, is approved for the treatment of pulmonary arterial hypertension (PAH) in adults. Transition from parenteral to oral treprostinil has been successfully accomplished in adults with PAH but not in children. In this multicenter study, pediatric patients treated with parenteral (Cohort 1) or inhaled (Cohort 2) treprostinil were transitioned to oral treprostinil. Prostacyclin-naïve individuals on background oral PAH therapy received oral treprostinil as add-on therapy (Cohort 3). Successful transition was oral treprostinil dose maintenance through week 24. Patients were monitored for adverse events (AEs), 6-min walk distance (6MWD), PAH symptoms, World Health Organization (WHO) Functional Class (FC), cardiac magnetic resonance imaging (cMRI), cardiopulmonary exercise testing (CPET), and quality of life through 24 weeks. A total of 32 patients were enrolled in the study; 23 (72%) were girls (mean age = 12.2 years). All patients were on background oral PAH therapy. Overall, patients (96.9%) maintained transition to oral treprostinil; one patient (Cohort 1) transitioned to oral treprostinil, then back to parenteral after experiencing syncope and WHO FC change from II to III. Cohorts 1, 2, and 3 received a final mean oral treprostinil dose of 5.6, 3.3, and 4.5 mg t.i.d., respectively. All cohorts had variable changes in 6MWD, cMRI, and CPET. Overall, 12 serious AEs were reported. All patients had drug-related AEs including headache (81%), diarrhea (69%), nausea (66%), vomiting (66%), and flushing (56%). Pediatric patients maintained transition to oral treprostinil with preservation of exercise capacity and WHO FC. Prostanoid-related AEs were most common and similar to those reported in adults.

Neural stem cell differentiation is dictated by distinct actions of nuclear receptor corepressors and histone deacetylases.

Signaling factors including retinoic acid (RA) and thyroid hormone (T3) promote neuronal, oligodendrocyte, and astrocyte differentiation of cortical neural stem cells (NSCs). However, the functional specificity of transcriptional repressor checkpoints controlling these differentiation programs remains unclear. Here, we show by genome-wide analysis that histone deacetylase (HDAC)2 and HDAC3 show overlapping and distinct promoter occupancy at neuronal and oligodendrocyte-related genes in NSCs. The absence of HDAC3, but not HDAC2, initiated a neuronal differentiation pathway in NSCs. The ablation of the corepressor NCOR or HDAC2, in conjunction with T3 treatment, resulted in increased expression of oligodendrocyte genes, revealing a direct HDAC2-mediated repression of Sox8 and Sox10 expression. Interestingly, Sox10 was required also for maintaining the more differentiated state by repression of stem cell programming factors such as Sox2 and Sox9. Distinct and nonredundant actions of NCORs and HDACs are thus critical for control of lineage progression and differentiation programs in neural progenitors.

SMRT-mediated repression of an H3K27 demethylase in progression from neural stem cell to neuron.

A series of transcription factors critical for maintenance of the neural stem cell state have been identified, but the role of functionally important corepressors in maintenance of the neural stem cell state and early neurogenesis remains unclear. Previous studies have characterized the expression of both SMRT (also known as NCoR2, nuclear receptor co-repressor 2) and NCoR in a variety of developmental systems; however, the specific role of the SMRT corepressor in neurogenesis is still to be determined. Here we report a critical role for SMRT in forebrain development and in maintenance of the neural stem cell state. Analysis of a series of markers in SMRT-gene-deleted mice revealed the functional requirement of SMRT in the actions of both retinoic-acid-dependent and Notch-dependent forebrain development. In isolated cortical progenitor cells, SMRT was critical for preventing retinoic-acid-receptor-dependent induction of differentiation along a neuronal pathway in the absence of any ligand. Our data reveal that SMRT represses expression of the jumonji-domain containing gene JMJD3, a direct retinoic-acid-receptor target that functions as a histone H3 trimethyl K27 demethylase and which is capable of activating specific components of the neurogenic program.

Activating the PARP-1 sensor component of the groucho/ TLE1 corepressor complex mediates a CaMKinase IIdelta-dependent neurogenic gene activation pathway.

Switching specific patterns of gene repression and activation in response to precise temporal/spatial signals is critical for normal development. Here we report a pathway in which induction of CaMKIIdelta triggers an unexpected switch in the function of the HES1 transcription factor from a TLE-dependent repressor to an activator required for neuronal differentiation. These events are based on activation of the poly(ADP-ribose) polymerase1 (PARP-1) sensor component of the groucho/TLE-corepressor complex mediating dismissal of the corepressor complex from HES1-regulated promoters. In parallel, CaMKIIdelta mediates a required phosphorylation of HES1 to permit neurogenic gene activation, revealing the ability of a specific signaling pathway to modulate both the derepression and the subsequent coactivator recruitment events required for transcriptional activation of a neurogenic program. The identification of PARP-1 as a regulated promoter-specific exchange factor required for activation of specific neurogenic gene programs is likely to be prototypic of similar molecular mechanisms.

Estrogen regulates the development of brain-derived neurotrophic factor mRNA and protein in the rat hippocampus.

During development, estrogen has a variety of effects on morphological and electrophysiological properties of hippocampal neurons. Brain-derived neurotrophic factor (BDNF) also plays an important role in the survival and differentiation of neurons during development. We examined the effects of gonadectomy with and without estrogen replacement on the mRNA and protein of BDNF and its receptor, trkB, during early postnatal development of the rat hippocampus. We used immunocytochemistry to demonstrate that estrogen receptor alpha (ERalpha) and BDNF were localized to the same cells within the developing hippocampus. BDNF and ERalpha were colocalized in pyramidal cells of the CA3 subregion and to a lesser extent in CA1. To determine whether BDNF mRNA was regulated by estrogen during development, we gonadectomized male rat pups at postnatal day 0 (P0) and examined mRNA and protein levels from P0 to P25 using real-time reverse transcription-PCR and Western blot analysis. After gonadectomy, BDNF mRNA levels are significantly reduced on P7, but after treatment of gonadectomized animals with estradiol benzoate on P0, levels at all ages were similar to those in intact animals. BDNF mRNA changes after gonadectomy are accompanied by an increase in the levels of BDNF protein, which were reduced by estrogen treatment at P0. We also examined the effect of postnatal estrogen treatment on trkB. There were no significant changes in trkB mRNA or protein in gonadectomized or estrogen-replaced animals. These results suggest that a direct interaction may exist between ERalpha and BDNF to alter hippocampal physiology during development in the rat.