New Developments, Challenges in Treating NMOSD

Jim Kling

October 22, 2020

New developments in treatment of neuromyelitis optica spectrum disorder (NMOSD) have opened up options for disease treatment in pediatric patients, but have led to some uncertainty and confusion as well.

At the2020 CNS-ICNA Conjoint Meeting, held virtually this year, presenters discussed some of the challenges of differential diagnosis and treatment choice in pediatric NMOSD, which is easily confused with multiple sclerosis.

NMOSD used to be considered a monophasic disease restricted to the optic nerve and spinal cord, but is now known to affect other regions of the central nervous system and to relapse in some patients.

Diagnosis

The disease is often mediated by antibodies to the aquaporin-4 (AQP-4) water channel, but about 30% of adult patients lack the antibody, and AQP-4 seronegativity is more common in the pediatric population. Another common antibody found in 40%–50% of children with NMOSD targets myelin oligodendrocyte glycoprotein (MOG).

It is important to be aware that false negatives can occur in serology assays, and false positives are common, particularly in ELISA assays, Silvia N. Tenembaum, MD, said during her presentation. For those reasons, serology is not enough for a diagnosis. "Patients should also have compatible symptoms and MRI findings," said Tenembaum, director of the pediatric neuroimmunology program at National Pediatric Hospital in Buenos Aires.

According to international consensus criteria, to be diagnosed with NMOSD, AQP-4 seropositive patients should also have at least one core clinical symptom: optic neuritis, acute myelitis, area postrema syndrome, other acute brainstem syndrome, symptomatic narcolepsy or acute diencephalic clinical syndrome, or symptomatic cerebral syndrome. AQP-4 seronegative patients or with unknown status should have at least two core symptoms, one of which must be optic neuritis, acute myelitis, or area postrema syndrome. Both conventional MRI and advanced new techniques are important for achieving differential diagnosis.

The most common symptom in children is optic neuritis, which occurs in 50%-70% of patients. Cerebral syndromes with or without encephalopathy and large tumefactive white matter lesions are also common, according to Tenembaum.

There are many conditions that mimic the spinal cord and optic nerve symptoms of NMOSD, which must be ruled out. One example is optic myelopathy and vision loss from late-onset biotinylase deficiency. It is critical to rule that out because it is treatable with supplements. Optic neuropathy, papillitis, and papilledema can also resemble NMOSD.

It is critical to achieve an early diagnosis of NMOSD in children, because some MS drugs can worsen NMOSD, according to Thaís Armangue, MD, PhD, head of neuroimmunology at SJD Barcelona Children's Hospital, who also presented at the session. She pointed out that the MOG antibody, while common in children, is also associated with many demyelinating diseases. Some 50%-60% of children with acute disseminated encephalomyelitis (ADEM) have high titers of MOG antibodies. Although early studies suggested that persistent anti-MOG antibodies were associated with risk of developing MS, more recent studies show it predicts a non-MS disease course, particularly at titers greater than 1:1280, according to Tenembaum. Persistent anti-MOG antibodies are also associated with relapsing disease, but it is associated with other syndromes besides NMOSD. "The probability is that [MOG antibodies are] useful, but they cannot guide chronic immunotherapy, because even monophasic patients can last maybe 12 months before they become MOG negative, and we cannot wait so many months" to determine treatment course, said Tenembaum.

For monophasic ADEM or NMOSD, there is no need for chronic treatment. But children with MS and recurrent NMOSD require early chronic immunotherapy because specific therapies have been shown to improve prognosis.

Acute Treatment

When it comes to acute treatment of NMOSD, the goal is to suppress the inflammatory attack but also to minimize long-term damage and optimize long-term neurological function. "The potential for irreversible injury with an attack is very high, and cumulative disabilities in NMOSD can result directly from attacks," E. Ann Yeh, MD, director of the Pediatric MS and Neuroinflammatory Disorders Program at the Hospital for Sick Children at the University of Toronto, said during her talk.

IV steroids are generally the first choice, with a preference for methylprednisolone. Pediatric patients that are MOG antibody positive usually respond better and more quickly than do adults, with rapid daily improvements in mobility, vomiting, and eyesight. Yeh recommends weaning good responders off steroids because AQP-4 positive patients are likely to relapse without a steroid wean, and antibody testing may be unavailable or results may be delayed. The wean can range from 4 weeks to 4-6 months, depending on antibody status, likelihood of AQP-4 positivity, and clinical parameters.

Inadequate responses are usually pretty evident. If there is only light perception by day 4 or 5, or paralyzed patients are nonambulatory and achieve only twitchy movements by that time, second-line therapies should be considered, including therapeutic plasma exchange (TPE) with 5-7 exchanges or intravenous immunoglobulins (IVIg).

Yeh called for quick treatment. Whatever you do, "please do it sooner rather than later if you think there's no response [to steroids]," Yeh said.

TPE is the first choice, according to Yeh. "There seems to be a fair amount of information that suggests that if you're having difficulty getting a response to steroids, TPE can make a difference in these patients," she said. But in some cases TPE may not be available, and IVIg can be attempted first. If it achieves no or only marginal improvement, TPE can be attempted later, but it must be kept in mind that TPE conducted too soon could wash out IVIg. Patients who get much better on IVIg can undergo a steroid wean, and then be evaluated for prophylactic therapy, said Yeh.

The evidence for IVIg is limited, reflecting the difficulty of studying treatments in rare populations. Still, when TPE is not available and the patient is quite impaired, IVIg makes sense to try. "Absence of evidence does not mean that the therapy doesn't work, and I don't think we should throw out the baby with the bath water," said Yeh.

Although IVIg treatment is generally well tolerated, there have been a few serious adverse events, such as anaphylactic shock and aseptic meningitis, according to Andrea Savransky, MD, a pediatrician at National Pediatric Hospital in Buenos Aires, who also spoke at the session. "I think it is important to weigh the benefits against the risk," Savransky said. She noted that TPE should not be taken lightly. One study showed more complications in pediatric patients than in adult patients, and it must be performed in specialized centers.

Emerging Treaments

Tanuja Chitnis, MD, director of the Partners Pediatric MS Center at Massachusetts General Hospital, Boston, discussed some of the emerging treatments for pediatric NMOSD. Rituximab has been associated with success in some retrospective studies, but dosing should be personalized. Chitnis reported that B cells can return before 6 months, so she monitors B cells beginning 2 months after induction, redosing after 4 or 5 months rather than 6 if B cells return.

Nevertheless, relapses can still occur after rituximab therapy. "There is room for additional therapies to address this gap," said Chitnis. Three new antibodies have received approval for treatment of NMOSD in adults. These include the complement inhibitor eculizumab, the IL-6 receptor antibody satralizumab, and the anti-CD19 antibody inebilizumab. Phase 3 clinical trials in children have been conducted for eculizumab and are in the planning stage for inebilizumab, and pediatric patients were included in pivotal trials for satralizumab.

Eculizumab treatment resulted in a 94.2% reduction in relapse risk in AQP4-positive adults. Satralizumab showed a 79% reduction in relapse risk among AQP-4 positive subjects with NMOSD or neuromyelitis optica and a 34% reduction in those who were AQP-4 negative. The pediatric subgroup had similar levels of response to adults, though the numbers were too small for a subgroup analysis.

In AQP-4 positive patients, inebilizumab treatment yielded a 77% reduction in relapse rate. In all patients, there was a 73% reduction.

For MOG antibody-positive patients with AQP-4 negative disease, novel therapies are at earlier stages of development. Typical MS therapies such as interferon beta and glatiramer acetate don't seem to be effective. Some that have shown signs of efficacy include azathioprine, mycophenylate mofetil, rituximab, and IVIg infusion, but the state of the field is not encouraging. "This is an observation now being studied in larger cohorts, but in general I have not found that there's a very strong response to any of these therapies, possibly with the exception of IVIg," said Chitnis.

Tenembaum has no relevant financial disclosures. Armangue has received speaking honoraria from Novartis and travel expenses for scientific meetings from Merck, Biogen, and Roche. Yeh is on the scientific advisory board of Juno Therapeutics and has received research support from Biogen. Chitnis advises Biogen-Idec, Novartis, and Alexion, serves on clinical trial advisory boards for Novartis and Sanofi Aventis, and has received research support from Verily, EMD Serono, and Novartis. Savransky has received honoraria from Genzyme de Argentina SA.

This article originally appeared on MDedge.com, part of the Medscape Professional Network.

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