FDA Approves ENDARI®, A New Treatment for Sickle Cell Disease

SUMMARY: The FDA on July 7, 2017 approved ENDARI® (L-Glutamine oral powder) for patients age five years and older with Sickle Cell disease to reduce severe complications associated with the blood disorder. Sickle cell disease or Sickle Cell anemia is an Autosomal Recessive disorder and affects approximately 100,000 Americans. It is estimated that it affects 1 out of every 365 African-American births and 1 out of every 16,300 Hispanic-American births. The average life expectancy for patients with Sickle Cell disease in the United States is approximately 40 to 60 years.

HbSS disease or Sickle Cell anemia is the most common Sickle Cell disease genotype and is associated with the most severe manifestations. HbSS disease is caused by a mutation substituting thymine for adenine in the sixth codon of the beta-globin chain gene. This in turn affects the hemoglobin’s ability to carry oxygen and causes it to polymerize. This results in decreased solubility thereby distorting the shape of the red blood cells, increasing their rigidity and resulting in red blood cells that are sickle shaped rather than biconcave. These sickle shaped red blood cells limit oxygen delivery to the tissues by restricting the flow in blood vessels, leading to severe pain and organ damage (vaso-occlusive crises). Oxidative stress is an important contributing factor to hemoglobin polymerization with polymer formation occurring only in the deoxy state. HbS/b-0 thalassemia (double heterozygote for HbS and b-0 thalassemia) is clinically indistinguishable from HbSS disease.

L-glutamine is a precursor for the synthesis of essential metabolic Oxidation-Reduction cofactors including Nicotinamide Adenine Dinucleotide (NAD). It has been shown in previous studies that there is higher L-glutamine utilization in Sickle Cell Anemia resulting in its depletion and thereby contributing to oxidative stress. Based on a phase II study showing favorable outcomes with ENDARI® compared with placebo, a phase III, randomized trial was conducted, in which the safety and efficacy of ENDARI® was studied in 230 Sickle Cell disease or beta-0 thalassemia patients, who had at least two episodes of painful crises during the 12 months before screening. Patients were randomized in a 2:1 ratio to receive ENDARI® (N=152) or placebo (N=78). Enrolled patients were 5-58 yrs old and ENDARI® was administered orally at 0.3 mg/kg/day for 48 weeks followed by a 3 week tapering period. Two thirds of the patients were on Hydroxyurea. The effect of treatment was evaluated over 48 weeks.

Patients who were treated with ENDARI® experienced fewer hospital visits for Sickle Cell crises pain management with parenteral narcotics or Ketorolac compared to those who received a placebo, fewer hospitalizations for Sickle Cell pain , and fewer days in the hospital (median 6.5 days versus median 11 days) compared to those on placebo. Further, patients who received ENDARI® also had fewer occurrences of acute chest syndrome (a life-threatening complication of sickle cell disease), compared with patients who received a placebo (8.6% versus 23.1%). The common side effects of ENDARI® included, nausea, constipation, headache, abdominal pain, cough, pain in the extremities, back pain and chest pain.

It was concluded that the benefit with ENDARI® for patients with Sickle Cell disease, was seen in all age groups and there was a consistent advantage with ENDARI® regardless of whether the patient was on Hydroxyurea or not. ENDARI® is the first treatment approved for patients with Sickle Cell disease in almost 20 years. Phase 3 Study of L-Glutamine Therapy in Sickle Cell Anemia and Sickle ß0-Thalassemia Subgroup Analyses Show Consistent Clinical Improvement. Niihara Y, Viswanathan K, Miller ST, et al. Abstarct#1318. Presented at ASH 58th Annual Meeting & Exposition, San Diego, CA. December 3-6, 2016