GBT021601 improves red blood cell health and the pathophysiology of sickle cell disease in a murine model.

The pathophysiologic mechanism of sickle cell disease (SCD) involves polymerization of deoxygenated haemoglobin S (HbS), leading to red blood cell (RBC) sickling, decreased RBC deformability, microvascular obstruction, haemolysis, anaemia and downstream clinical complications. Pharmacological increase in the concentration of oxygenated HbS in RBCs has been shown to be a novel approach to inhibit HbS polymerization and reduce RBC sickling and haemolysis. We report that GBT021601, a small molecule that increases HbS-oxygen affinity, inhibits HbS polymerization and prevents RBC sickling in blood from patients with SCD.

Increased hemoglobin affinity for oxygen with GBT1118 improves hypoxia tolerance in sickle cell mice.

Therapeutic agents that increase the Hb affinity for oxygen (O) could, in theory, lead to decreased O release from Hb and impose a hypoxic risk to tissues. In this study, GBT1118, an allosteric modifier of Hb affinity for O, was used to assess the impact of increasing Hb affinity for O on brain tissue oxygenation, blood pressure, heart rate, O delivery, and tolerance to hypoxia in Townes transgenic sickle cell disease (SCD) mice. Brain oxygenation and O delivery were studied during normoxia and severe hypoxic challenges.

Impact of Pharmacologically Left Shifting the Oxygen-Hemoglobin Dissociation Curve on Arterial Blood Gases and Pulmonary Gas Exchange During Maximal Exercise in Hypoxia.

Stewart, Glenn M., Troy J. Cross, Michael J.

Effects of an allosteric hemoglobin affinity modulator on arterial blood gases and cardiopulmonary responses during normoxic and hypoxic low-intensity exercise.

Numerous pathophysiological conditions induce hypoxemia-related cardiopulmonary perturbations, decrements in exercise capacity, and debilitating symptoms. Accordingly, this study investigated the efficacy of an allosteric hemoglobin modulator (voxelotor) to enhance arterial oxygen saturation during low-intensity exercise in hypoxia. Eight normal healthy subjects (36 ± 7 yr; 73.

The effect of the antisickling compound GBT1118 on the permeability of red blood cells from patients with sickle cell anemia.

Sickle cell anemia (SCA) is one of the commonest severe inherited disorders. Nevertheless, effective treatments remain inadequate and novel ones are avidly sought. A promising advance has been the design of novel compounds which react with hemoglobin S (HbS) to increase oxygen (O ) affinity and reduce sickling.

A phase 1/2 ascending dose study and open-label extension study of voxelotor in patients with sickle cell disease.

New treatments directly targeting polymerization of sickle hemoglobin (HbS), the proximate event in the pathophysiology of sickle cell disease (SCD), are needed to address the severe morbidity and early mortality associated with the disease. Voxelotor (GBT440) is a first-in-class oral therapy specifically developed to treat SCD by modulating the affinity of hemoglobin (Hb) for oxygen, thus inhibiting HbS polymerization and downstream adverse effects of hemolytic anemia and vaso-occlusion. GBT440-001 was a phase 1/2 randomized, double-blind, placebo-controlled, single and multiple ascending dose study of voxelotor in adult healthy volunteers and patients with SCD, followed by a single-arm, open-label extension study.

GBT440 reverses sickling of sickled red blood cells under hypoxic conditions .

Sickle cell disease is characterized by hemolytic anemia, vasoocclusion and early mortality. Polymerization of hemoglobin S followed by red blood cell sickling and subsequent vascular injury are key events in the pathogenesis of sickle cell disease. Sickled red blood cells are major contributors to the abnormal blood rheology, poor microvascular blood flow and endothelial injury in sickle cell disease.

GBT440 improves red blood cell deformability and reduces viscosity of sickle cell blood under deoxygenated conditions.

Background: In sickle cell disease (SCD), polymerization of hemoglobin S (HbS) leads to the formation of rigid, non-deformable sickled RBCs. Loss of RBC deformability, sickling and irreversible membrane damage causes abnormal blood rheology, and increases viscosity which contributes to vasoocclusion and other SCD pathophysiology. GBT440 (generic name voxelotor) is a novel anti-polymerization and anti-sickling agent currently undergoing clinical evaluation for the treatment of SCD.

GBT1118, a potent allosteric modifier of hemoglobin O affinity, increases tolerance to severe hypoxia in mice.

Adaptation to hypoxia requires compensatory mechanisms that affect O transport and utilization. Decreased hemoglobin (Hb) O affinity is considered part of the physiological adaptive process to chronic hypoxia. However, this study explores the hypothesis that increased Hb O affinity can complement acute physiological responses to hypoxia by increasing O uptake and delivery compared with normal Hb O affinity during acute severe hypoxia.

Discovery of GBT440, an Orally Bioavailable R-State Stabilizer of Sickle Cell Hemoglobin.

We report the discovery of a new potent allosteric effector of sickle cell hemoglobin, GBT440 (), that increases the affinity of hemoglobin for oxygen and consequently inhibits its polymerization when subjected to hypoxic conditions. Unlike earlier allosteric activators that bind covalently to hemoglobin in a 2:1 stoichiometry, binds with a 1:1 stoichiometry. Compound is orally bioavailable and partitions highly and favorably into the red blood cell with a RBC/plasma ratio of ∼150.

GBT440 Inhibits Sickling of Sickle Cell Trait Blood Under Conditions Mimicking Strenuous Exercise.

In sickle cell trait (SCT), hemoglobin A (HbA) and S (HbS) are co-expressed in each red blood cell (RBC). While homozygous expression of HbS (HbSS) leads to polymerization and sickling of RBCs resulting in sickle cell disease (SCD) characterized by hemolytic anemia, painful vaso-occlusive episodes and shortened life-span, SCT is considered a benign condition usually with minor or no complications related to sickling. However, physical activities that cause increased tissue oxygen demand, dehydration and/or metabolic acidosis leads to increased HbS polymerization and life-threatening complications including death.

Increased hemoglobin-oxygen affinity ameliorates bleomycin-induced hypoxemia and pulmonary fibrosis.

Although exertional dyspnea and worsening hypoxia are hallmark clinical features of idiopathic pulmonary fibrosis (IPF), no drug currently available could treat them. GBT1118 is a novel orally bioavailable small molecule that binds to hemoglobin and produces a concentration-dependent left shift of the oxygen-hemoglobin dissociation curve with subsequent increase in hemoglobin-oxygen affinity and arterial oxygen loading. To assess whether pharmacological modification of hemoglobin-oxygen affinity could ameliorate hypoxemia associated with lung fibrosis, we evaluated GBT1118 in a bleomycin-induced mouse model of hypoxemia and fibrosis.

GBT440 increases haemoglobin oxygen affinity, reduces sickling and prolongs RBC half-life in a murine model of sickle cell disease.

A major driver of the pathophysiology of sickle cell disease (SCD) is polymerization of deoxygenated haemoglobin S (HbS), which leads to sickling and destruction of red blood cells (RBCs) and end-organ damage. Pharmacologically increasing the proportion of oxygenated HbS in RBCs may inhibit polymerization, prevent sickling and provide long term disease modification. We report that GBT440, a small molecule which binds to the N-terminal α chain of Hb, increases HbS affinity for oxygen, delays in vitro HbS polymerization and prevents sickling of RBCs.

The proteins PDIP3 and ZC11A associate with the human TREX complex in an ATP-dependent manner and function in mRNA export.

The conserved TREX complex, which contains UAP56, Aly, CIP29, and the multi-subunit THO complex, functions in mRNA export. Recently, several putative new components of the human TREX complex were identified by mass spectrometry. Here, we investigated the function of two of these, PDIP3 and ZC11A.

A role for TREX components in the release of spliced mRNA from nuclear speckle domains.

The TREX complex, which functions in mRNA export, is recruited to mRNA during splicing. Both the splicing machinery and the TREX complex are concentrated in 20-50 discrete foci known as nuclear speckle domains. In this study, we use a model system where DNA constructs are microinjected into HeLa cell nuclei, to follow the fates of the transcripts.

ATP is required for interactions between UAP56 and two conserved mRNA export proteins, Aly and CIP29, to assemble the TREX complex.

The conserved TREX mRNA export complex is known to contain UAP56, Aly, Tex1, and the THO complex. Here, we carried out proteomic analysis of immunopurified human TREX complex and identified the protein CIP29 as the only new component with a clear yeast relative (known as Tho1). Tho1 is known to function in mRNA export, and we provide evidence that CIP29 likewise functions in this process.

Human mRNA export machinery recruited to the 5' end of mRNA.

Pre-mRNAs undergo splicing to remove introns, and the spliced mRNA is exported to the cytoplasm for translation. Here we investigated the mechanism for recruitment of the conserved mRNA export machinery (TREX complex) to mRNA. We show that the human TREX complex is recruited to a region near the 5' end of mRNA, with the TREX component Aly bound closest to the 5' cap.

Functional coupling of RNAP II transcription to spliceosome assembly.

The pathway of gene expression in higher eukaryotes involves a highly complex network of physical and functional interactions among the different machines involved in each step of the pathway. Here we established an efficient in vitro system to determine how RNA polymerase II (RNAP II) transcription is functionally coupled to pre-mRNA splicing. Strikingly, our data show that nascent pre-messenger RNA (pre-mRNA) synthesized by RNAP II is immediately and quantitatively directed into the spliceosome assembly pathway.