The CDC estimates that sickle cell disease affects well over 100,000 Americans, with the disease occurring most often in African Americans. September has been designated as National Sickle Cell Awareness month designed to focus attention on the ongoing research in this field and the need for new treatments. The sector can certainly point to the significant progress that has taken place during the past few years, with new medicines reaching the market and several novel therapeutics with new mechanisms of action advancing in the pipeline.
Ted Love, president and CEO of Global Blood Therapeutics Inc. (GBT), said 2019 was “a landmark year” with the FDA approval of two new novel therapies to treat sickle cell disease. He was speaking at the virtual annual Sickle Cell Disease (SCD) Therapeutics Conference this week. His company, together with the Sickle Cell Disease Association of America, was hosting the one-day event featuring discussions on the latest advances and future trends.
The key manifestation of the inherited blood disorder is that red blood cells (RBCs) are abnormally shaped (crescent), which restricts their flow in blood vessels and limits oxygen delivery to the body’s tissues, leading to severe pain and organ damage. The condition is also characterized by severe chronic inflammation that results in vaso-occlusive crisis (VOC) where patients experience episodes of extreme pain and organ damage.
Late November, GBT gained accelerated approval for its Oxbryta (voxelotor) tablets for the treatment SCD in adults and pediatric patients 12 and older. The agency’s green light came less than two weeks after it gave the go-ahead to Novartis AG for Adakveo (crizanlizumab) to reduce the frequency of VOCs in adult and pediatric patients ages 16 and older with SCD.
According to Love, Oxbryta is a new class of therapy binding to hemoglobin and stabilizing RBCs in an oxygenated state and inhibiting deoxygenated sickle hemoglobin polymerization, making cells less likely to bind together and form the distinctive sickle shape.
The launch of the drug has gone well since it was approved, he said in the company’s second-quarter financial report and business update, despite the impact of COVID-19. Net sales in the period reached $31.5 million, well ahead of the Street’s expectations. Going forward, the company is planning to expand the potential use of Oxbryta for the treatment of SCD in children as young as 4 years old and also seek marketing authorization in Europe for Oxbryta to treat hemolytic anemia in SCD patients ages 12 and older with a marketing authorization application being submitted to the EMA by the middle of next year.
Cambridge, Mass.-based Agios Pharmaceuticals Inc. is working on mitapivat (AG-348), an investigational, oral, small-molecule allosteric activator of wild-type and a variety of mutated pyruvate kinase-R (PKR) enzymes, in patients with SCD. The compound has been shown to decrease 2,3-diphosphoglycerate (2,3-DPG) and increase adenosine triphosphate (ATP), and through that mechanism, it may reduce hemoglobin (Hb) S polymerization and red blood cell sickling. In June, the company reported that clinical proof of concept had been established based on a preliminary analysis in a phase I trial being conducted in collaboration with the U.S. NIH as part of a cooperative research and development agreement.
The ongoing study had enrolled nine patients, with eight completing all planned dose levels of mitapivat. Seven of eight patients who completed all dose levels experienced a Hb increase, with five of eight patients (63%) achieving a hemoglobin increase of ≥1 g/dL from baseline (range 1-2.7 g/dL). All five patients who achieved a hemoglobin increase of ≥1 g/dL did so at doses of 50 mg BID or lower. Decreases in 2,3-DPG and increases in ATP levels were observed, consistent with the proposed mechanism of action and comparable to that observed in healthy volunteer studies with mitapivat.
The company said it expects to report data from ACTIVATE and ACTIVATE-T, its two global pivotal trials for mitapivat in adults with pyruvate kinase deficiency, between the end of 2020 and mid-2021.
Watertown, Mass.-based Forma Therapeutics Holdings Inc., which made its public debut this year, also has a selective RBC pyruvate kinase-R activator in its pipeline for treating SCD. FT-4202 is being evaluated in a phase I trial in SCD patients ages 12 and older and has been granted fast track, rare pediatric and orphan drug designations. The compound is a potent activator of pyruvate kinase-R designed to improve RBC metabolism, function and survival by decreasing 2,3 DPG and increasing ATP, potentially resulting in both increased hemoglobin levels and reduced VOCs.
Olinciguat, an oral guanylate cyclase (sGC) stimulator, being developed by Cyclerion Therapeutics Inc., has completed the treatment period in its STRONG-SCD study with a total of 70 patients randomized. The placebo-controlled, dose-ranging study is designed to evaluate safety, tolerability and pharmacokinetics, as well as to explore effects on daily symptoms and biomarkers of disease activity when dosed over a 12-week treatment period. Top-line results are expected this year. Olinciguat is a compound that aims to stimulate sGC production, leading to the production of a signaling molecule called cyclic guanosine monophosphate (cGMP). High levels of cGMP help reduce inflammation in blood vessels, decrease adhesion between RBCs, and allow for improved blood flow by increasing the availability of nitric oxide.
Boston-based Imara Inc. is developing IMR-687, a small-molecule inhibitor of PDE9 that degrades cyclic guanosine monophosphate (cGMP), an active signaling molecule that plays a role in vascular biology. The company said that lower levels of cGMP are often found in people with SCD and beta-thalassemia and are associated with impaired blood flow, increased inflammation, greater cell adhesion and reduced nitric oxide-mediated vasodilation. Blocking PDE9 acts to increase cGMP levels, which are associated with reactivation of fetal hemoglobin.
In August, the company dosed the first patient in its Ardent phase IIb trial of IMR-687 for adult patients with SCD. The planned primary efficacy objective is to evaluate the proportion of all patients with fetal hemoglobin (HbF) response, defined as an increase of 3% in HbF from baseline to week 24, compared to placebo.
Gene therapy/gene editing
Since SCD is a monogenic disease condition, researchers believe that it would be a good candidate for gene therapy therapeutic approaches. For example, significant progress is being made by Cambridge, Mass.-based Bluebird Bio Inc. with lentiglobin, its lentiviral-based gene therapy that inserts an anti-sickling beta-globin variant into CD34-positive cells, progenitors of red blood cells.
At the virtual European Hematology Association (EHA) meeting in June, it reported new data from its ongoing phase I/II study involving adult and adolescent patients with SCD that showed a near-complete reduction of serious VOCs and acute chest syndrome. The company expects to submit a BLA to the FDA for the gene therapy next year.
Crispr Therapeutics AG and Vertex Pharmaceuticals Inc. are progressing CTX-001, an investigational, autologous, CRISPR/Cas9 gene-edited hematopoietic stem cell therapy being evaluated for patients suffering from severe hemoglobinopathies. At EHA, the companies reported that in the phase I/II Climb-121 study, at nine months after CTX-001 infusion, the first treated patient was free of VOCs, was transfusion independent and had total hemoglobin levels of 11.8 g/dL, 46.1% fetal hemoglobin and F-cells (erythrocytes expressing fetal hemoglobin) of 99.7%.
Last month, Cambridge, Mass.-based Editas Medicine Inc., a genome editing company, reported that the FDA had granted rare pediatric disease designation for EDIT-301, an experimental, autologous cell medicine, being developed as a potentially best-in-class, durable medicine for SCD. The company plans to file an investigational new drug application for EDIT-301 by the end of this year. EDIT-301 comprises sickle patient CD34+ cells genetically modified using a hCRISPR/Cas12a (also known as Cpf1) ribonucleoprotein to edit the HBG1/2 promoter region in the beta-globin locus. Red blood cells derived from EDIT-301 CD34+ cells demonstrate a sustained increase in fetal hemoglobin (HbF) production.
In its second-quarter financial report and business update, Beam Therapeutics Inc. announced the nomination of its first two adenine base editing development candidates, BEAM-101, targeting patients with hereditary persistence of fetal hemoglobin, and BEAM-102 (Makassar variant), both aimed at correcting SCD.
The NIH, which reports it spends approximately $100 million on sickle cell disease research, announced that is has launched The Cure Sickle Cell Initiative designed to speed the development of cures for the disease. It will take advantage of the latest genetic discoveries and technological advances to progress the most promising genetic-based curative therapies safely into clinical trials within five to 10 years.
Aided by research partners, the initiative will establish a national data warehouse of genetic therapies for sickle cell disease and conduct comparative analyses of therapeutic approaches to assess both clinical and cost effectiveness. National networks will also be created to make it easier for patients and providers to interact with the research, clinical trials, and other activities.