FDA OKs First Treatment Specifically for Primary Hemophagocytic Lymphohistiocytosis

Officials with the FDA have approved emapalumab-lzsg (Gamifant) for the treatment of pediatric and adult patients with primary hemophagocytic lymphohistiocytosis (HLH), making it the first FDA-approved drug specifically indicated for this disease, according to a press release.

HLH is a rare, life-threatening condition in which the body produces too many activated immune cells. The disease, which typically affects children, can cause symptoms such as fever, enlarged liver or spleen, decreased number of blood cells, and neurological abnormalities. It can be inherited, which is known as primary HLH, or have non-inherited causes.

Emapalumab is indicated to treat both adults and children (newborn and older) who have refractory, recurrent, or progressive disease or intolerance with conventional HLH therapy, in combination with dexamethasone through intravenous infusion over 1 hour twice per week until hematopoietic stem cell transplant.

The approval was based on results from a phase 2/3 clinical study, which included 34 patients with primary HLH. The efficacy of emapalumab was evaluated in a cohort of 27 patients with refractory, recurrent, or progressive disease during conventional HLH therapy or who were intolerant to conventional HLH therapy. Patients received emapalumab-lzsg concomitantly with dexamethasone. Of the patients in the study, 82% had a genetically confirmed primary HLH diagnosis.

According to the data, 63% of patients demonstrated an overall response at the end of the treatment, defined as the achievement of either a complete or partial response, or HLH improvement. The study also showed that 70% of patients were able to proceed to hematopoietic stem cell transplant.

"HLH is a disorder of immune regulation in which many cytokines are deranged, but interferon gamma appears to play a critical role. While we have long understood the pivotal role of this cytokine in HLH, until emapalumab's approval we did not have a medicine that could specifically hit this target," primary study investigator Michael Jordan, MD, a physician-scientist in the division of Bone Marrow Transplantation and Immune Deficiency at Cincinnati Children's Hospital Medical Center HLH Center of Excellence, said in a statement. "Emapalumab represents an entirely new approach to treating primary HLH and helping these very sick patients reach hematopoietic stem cell transplant."

Adverse effects commonly reported in the trial by patients receiving emapalumab included infections, hypertension, infusion-related reactions, low potassium, and fever. Patients being treated with emapalumab should not be given any live vaccines and should be tested for latent tuberculosis, according to the press release.

“Primary HLH is a rare and life-threatening condition typically affecting children and this approval fills an unmet medical need for these patients,” said Richard Pazdur, MD, director of the FDA’s Oncology Center of Excellence and acting director of the Office of Hematology and Oncology Products in the FDA’s Center for Drug Evaluation and Research, in a statement. “We are committed to continuing to expedite the development and review of therapies that offer meaningful treatment options for patients with rare conditions.”

The FDA previously granted this application Priority Review, Breakthrough Therapy designation and Orphan Drug designation. The treatment is expected to be available for administration in treatment centers across the United States in the first quarter of 2019.

Emapalumab-lzsg was developed and submitted for approval to the FDA by Novimmune SA. Sobi acquired the global rights to Gamifant from Novimmune SA through an exclusive licensing agreement announced in July 2018, according to a Sobi press release.

References

1. FDA approves first treatment specifically for patients with rare and life-threatening type of immune disease [news release]. FDA’s website. https://www.fda.gov/NewsEvents/Newsroom/PressAnnouncements/ucm626263.htm. Accessed November 20, 2018.

2. FDA Approves Gamifant (emapalumab), the first and only treatment for primary hemophagocytic lymphohistiocytosis [news release]. Sobi's website. https://www.sobi.com/en/investors/fda-approves-gamifantr-emapalumab-first-and-only-treatment-primary-haemophagocytic. Accessed November 20, 2018.