Last updated on December 2019

Safety Tolerability Pharmacokinetics and Pharmacodynamics of Escalating Multiple Oral Doses of AG-348 in Subjects With Stable Sickle Cell Disease


Brief description of study

Background

Sickle Cell Disease (SCD) is an inherited blood disorder. People with SCD have abnormal hemoglobin in their red blood cells. Researchers are investigating the safety and efficacy of an investigational medicine called AG-348 (mitapivat sulfate) o determine if it will help people with SCD.

Objective

To test the tolerability and safety of AG-348 in people with SCD.

Eligibility

People ages 18 and older with SCD.

Design

Participants will have 7 visits over approximately 14 weeks. At the first visit

participants will be screened with a medical history; a physical exam; and blood, urine, and heart tests. At the following 4 visits participants will stay at the clinic for up to 2 nights. Participants will take study drug in increasing doses for 6 weeks, after which the drug will be tapered off. All visits will include physical exam, blood, and urine tests. The last visit will occur 4 weeks after stopping the drug and also includes a heart test. Participants will provide DNA from the blood samples they provide. The DNA will be tested for an inherited gene that can cause differences in response to the study drug. Researchers may also test other genes to see if they can find any genes that interact with SCD.

Detailed Study Description

Sickle cell disease (SCD) is a multisystem disorder associated with episodes of acute clinical events and progressive organ damage. Episodic pain, triggered by micro-vasoocclusion induced by sickled red blood cells, is the most common acute complication and the leading cause of hospitalization. Management strategies for SCD have evolved very slowly, and treatment of acute pain is still limited to supportive therapy with opioid medication. Until recently in 2017, the only approved therapy for SCD was hydroxyurea (HU), indicated to reduce frequency of acute painful crises but not universally effective. In addition to HU, transfusions with normal red blood cells are widely used to treat severe sickle crises, but this strategy has limitations (not uniformly accessible, accompanied by risks of alloimmunization, hemolytic transfusion reactions and transfusional iron overload). The only curative treatment is bone marrow transplantation, but this option carries significant risks and is limited by the availability of histocompatible donors.

As the root cause of SCD is polymerization of deoxy-HbS, there is a strong rationale for exploring agents that could inhibit/reduce the polymerization process itself. HbS polymerizes only when deoxygenated, its oxygenation is influenced by a few factors, one key factor being the 2,3- diphosphoglycerate (2,3-DPG) concentration in the red blood cell. Increased intracellular 2,3-DPG decreases oxygen binding and stabilizes the deoxygenated form (T form) of hemoglobin. In addition, increased 2,3-DPG concentration decreases intracellular red cell pH further promoting HbS polymerization. 2,3-DPG is an intermediate substrate in the glycolytic pathway, the only source of ATP production in red blood cells. Pyruvate kinase (PK) is a key enzyme in the final step of glycolysis; PK converts phosphoenolpyruvate to pyruvate, creating 50% of the total red cell ATP that is essential for maintaining integrity of the red cell membrane. Reduced PK activity leads to accumulation of the upstream enzyme substrates, including 2,3- DPG, that favours polymerization of deoxy-HbS. In humans with SCD, and even in sickle carriers who are generally asymptomatic, reduced oxygen affinity will favour deoxygenation of HbS and its polymerisation, and thus sickling. Indeed, the combination of PK deficiency and sickle cell trait causing an acute sickling syndrome has been previously reported in two cases.

Current approaches to reduce HbS polymerization include fetal haemoglobin induction via multiple strategies and drugs that targets HbS polymerization through increasing affinity of hemoglobin for oxygen (eg. Voxelotor / GBT440). Increasing red cell PK (PK-R) activity, leading to a decrease in intracellular 2,3-DPG concentration, presents a potentially attractive therapeutic target for thwarting HbS polymerization and acute sickle pain. AG-348 is a novel, orally bioavailable, small molecule allosteric activator of PK-R, that is currently in Phase II/III clinical trials in humans with PK deficiency (NCT02476916, NCT03548220 / AG348-C-006; NCT03559699 / AG348-C-007). Overview of the preclinical AG-348 data and other data support dose-dependent changes in blood glycolytic intermediates consistent with glycolytic pathway activation at all multiple ascending doses tested, supporting the potential role of AG-348 in the treatment of sickle cell disease. The overall objective of the present study is to determine the clinical safety and tolerability of AG-348 in subjects with SCD.

Clinical Study Identifier: NCT04000165

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