US regulators have approved Swedish Orphan Biovitrum (Sobi) and Novimmune’s Gamifant as the first treatment for the rare disorder primary haemophagocytic lymphohistiocytosis.

The condition, an orphan disease for which there is currently no treatment, is a clinical syndrome of hyperinflammation driven by high interferon gamma production and characterised by severe hyperferritinemia, fever, severe cytopenia, coagulation defects and organomegaly.

HLH occurs as a familial autosomal recessive disorder or as an acquired, reactive condition. The former typically presents in paediatric patients, is lethal if untreated, and has a 40 percent mortality rate with current best available care.

The secondary form of the disease typically arises later in life, and is also linked with significant mortality.

Gamifant (emapalumab) is a fully human, anti-interferon-gamma monoclonal antibody discovered and developed by Novimmune, which neutralises the biological activity of IFNγ, and thus offers the first targeted therapy for this disease.

US regulators have approved the drug for the treatment of paediatric (new born and older) and adult patients with primary HLH with refractory, recurrent or progressive disease or intolerance to conventional HLH therapy.

Clearance was based on data from a Phase II/III trial in which a clinically meaningful and statistically significant proportion of patients demonstrated an overall response at the end of treatment. Also, 70% of patients proceeded to haematopoietic stem-cell transplantation (HSCT).

“Primary HLH is a very rare disease with significant morbidity and mortality. The approval of Gamifant as the first treatment for primary HLH is a significant step in our journey of helping these patients,” noted Milan Zdravkovic, chief medical officer and head of R&D at Sobi.

“Emapalumab represents an entirely new approach to treating primary HLH and helping these very sick patients reach haematopoietic stem cell transplant,” added Michael Jordan, a physician-scientist in the division of Bone Marrow Transplantation and Immune Deficiency at Cincinnati Children's Hospital Medical Center HLH Center of Excellence, and primary investigator in the emapalumab clinical trial.

The therapy, to which Sobi picked up exclusive rights from Novimmune in July this year, is also currently under review in Europe.