Attendees at the 2015

ASH Annual Meeting

Photo courtesy of ASH

ORLANDO, FL—A monoclonal antibody (mAb) targeting interferon-gamma (IFNγ) has shown promise for treating hemophagocytic lymphohistiocytosis (HLH), according to a late-breaking abstract presented at the 2015 ASH Annual Meeting.

Results of an ongoing phase 2 study suggest the mAb, NI-0501, may be a feasible treatment option for patients with HLH who have demonstrated an unsatisfactory response to, or cannot tolerate, conventional therapy.

Nine of 13 evaluable patients achieved a “satisfactory response” to NI-0501, and no safety concerns were identified, said Michael Jordan, MD, of Cincinnati Children’s Hospital Medical Center in Ohio.

Dr Jordan presented these results at ASH as LBA-3.* The trial was sponsored by Novimmune.

“Treatment of HLH remains very challenging,” Dr Jordan noted. “Initial therapy is directed at trying to suppress the out-of-control immune response. In children that are at risk for recurrent episodes of HLH, they proceed to hematopoietic cell transplantation and, hopefully, this allows long-term survival.”

“First-line therapy has been defined in international trials and involves etoposide and dexamethasone. This regimen, as you might imagine, in children that present already with cytopenias, is myelosuppressive. It’s also broadly immune-suppressive. And although this does allow long-term survival in these children, there’s plenty of room for improvement in results.”

“[T]here is no standard of care for second-line therapy. Though there are no prospective data, children are increasingly treated with T-cell-depleting agents such as alemtuzumab and ATG, but this produces profound and long-lasting immune suppression. Though survival is not well-defined in these patients, it’s thought to be poor.”

In hopes of finding a new treatment option for HLH, Dr Jordan and his colleagues attempted to determine what drives the disease process. In preclinical studies, they identified IFNγ as a rational target in HLH. Blockade of IFNγ led to improved survival in mouse models.

The researchers also found elevated levels of IFNγ in patients with HLH. These preclinical and clinical data led to the development of NI-0501, a fully human, high affinity, anti-IFNγ mAb that binds to and neutralizes IFNγ.

Patients and treatment

In their phase 2 trial, Dr Jordan and his colleagues assessed NI-0501 in 16 patients—8 males and 8 females. Their median age was 1.2 years (range, 0.2-13). Twelve patients had causative mutations—FHL2 (n=4), FHL3 (n=2), FHL4 (n=1), GS-2 (n=3), XLP-1 (n=1), and XLP-2 (n=1). And 4 patients had central nervous system (CNS) involvement.

Two patients were receiving NI-0501 as first-line treatment, and the rest were receiving the mAb as second-line treatment. Patients had previously received dexamethasone (n=13), methylprednisone (n=2), etoposide (n=13), ATG (n=4), cyclosporine A (n=6), and “other” therapy (n=4).

NI-0501 was given at a starting dose of 1 mg/kg every 3 days, with possible dose increases guided by pharmacokinetic data and/or clinical response in each patient. The mAb was administered with dexamethasone at a dose of 5mg/m² to 10 mg/m², but dexamethasone could be tapered during the treatment course.

The treatment duration ranged from 4 weeks to 8 weeks, and the follow-up period was 4 weeks.

Response and survival

One patient was excluded from the analysis due to a lymphoma diagnosis after enrollment. Two patients are still receiving treatment, and 13 have completed treatment.

Among the patients who completed therapy, 4 had an insufficient response. Two of these patients died, and 2 proceeded to allogeneic hematopoietic stem cell transplant (HSCT) after receiving additional agents to control their disease.

Nine patients achieved a favorable response to NI-0501. Seven of these patients proceeded to HSCT, and 2 are awaiting HSCT with their disease well-controlled.

Post-transplant follow-up is still early for most patients, but 2 patients have follow-up greater than 1 year. One child died of graft-vs-host disease around day 45, but the remaining patients who went on to HSCT are still alive.

Characteristics of response

For some patients, response to NI-0501 included a significant improvement in neutrophil count (8/10, P<0.001), platelet count (7/12, P<0.001), and ferritin level (P=0.0025). The median serum ferritin level was 4142 ng/mL at baseline and 1648 ng/mL at the end of treatment.

Both patients who were febrile at the start of treatment experienced rapid normalization of fever. Six of 7 patients with palpable spleen or liver at the start of treatment had an improvement in organomegaly. And 3 of 4 patients had resolution or improvement of CNS involvement.

Overall, there was a significant decrease in glucocorticoid dose. The median dose at baseline was 10.0 mg/m². At the end of treatment, the median dose was 4.0 mg/m² (P=0.023).

“One pharmacodynamic readout that’s useful for understanding IFNγ biology in vivo is CXCL9,” Dr Jordan noted. “This is secreted by mononuclear phagocytes in response to IFNγ. And most patients had a very clear fall in CXCL9 while receiving NI-0501.”

Adverse events and death

No off-target effects of NI-0501 have been observed, and none of the patients have withdrawn from the study for safety reasons.

There have been 14 serious adverse events in 8 patients, but only 1 of these events was considered treatment-related. The patient had necrotizing fasciitis following P aeruginosa skin infection, which resolved. This event was considered treatment-related by an investigator but not by the data monitoring committee or the sponsor.

In all, 3 patients have died, but none of the deaths were related to NI-0501. Two patients died of HLH/multi-organ failure, and 1 died of graft-vs-host disease.

Infections

“[NI-0501 provides] a targeted form of immune suppression, so we can expect that most concerns will be related to infection,” Dr Jordan said. “The effects of IFNγ on immune defense are actually predictable, and they’re predictable because of 2 patient populations.”

“First are the rare patients who are born with IFNγ-receptor deficiency, and second are individuals that develop neutralizing autoantibodies against IFNγ. Both patient populations experience infections with atypical mycobacteria, tuberculosis, Salmonella, and so forth.”

There were 10 infections already present at the start of the study—St epidermidis (n=1), C difficile (n=1), E coli (n=1, gram-positive), cytomegalovirus (n=1), Epstein-Barr virus (n=4), and parvovirus (n=1). All of these infections resolved with treatment.

Fourteen infections arose during the study course—St epidermidis (n=1), C difficile (n=1), P aeruginosa (n=1), K pneumoniae (n=1), E coli (1 gram-positive, 1 gram-negative), adenovirus (n=1), cytomegalovirus (n=2), Epstein-Barr virus (1 reactivation), parvovirus (1 reactivation), parainfluenza T3 (n=1), influenza A (n=1), and Candida (n=1).

Most of these infections resolved. The exceptions were the case of adenovirus, 1 case of cytomegalovirus (although there was improvement), the Epstein-Barr virus reactivation, the parvovirus reactivation (though improved), and the case of influenza A.

The researchers did not know if the parainfluenza T3 infection resolved. The patient’s viral status was not reassessed prior to death.

“So, in conclusion, NI-0501 has shown the potential to improve or resolve clinical and laboratory abnormalities of HLH, including CNS signs and symptoms,” Dr Jordan said. “The response to this agent appears to be independent of the underlying causative mutation. It’s also independent of the presence and type of infectious trigger.”

“NI-0501 was very well-tolerated. No safety concerns have emerged to date, and no infections known to be caused by deficiency of IFNγ have been observed. The neutralization of IFNγ by NI-0501 can offer an innovative and targeted approach to the management of HLH.”

*Data in the abstract differ from data presented at the meeting.

mAb could provide targeted approach to HLH treatment