according to trial results published in the Lancet Neurology.
Dr. Anthony Traboulsee
The findings help confirm the role of interleukin-6 in the pathobiology of aquaporin-4 autoantibody (AQP4-IgG)–seropositive disease. For patients who are AQP4-IgG seronegative, however, “there is insufficient evidence to indicate a risk reduction” with this drug, the investigators wrote. In addition, satralizumab did not significantly affect pain or fatigue.
“The limitations of the study include the relatively small group sizes and low number of relapses. Despite these limitations, a significant treatment benefit was observed with satralizumab, compared with placebo in the study population, with efficacy and safety comparable to satralizumab used in combination with immunosuppressants,” reported lead author Anthony Traboulsee, MD, professor of neurology at the University of British Columbia, Vancouver, and colleagues.
Satralizumab is a humanized monoclonal antibody targeting the IL-6 receptor. A prior phase 3 study, SakuraSky, found that the drug reduces the risk of NMOSD relapse when added to immunosuppressant therapy. To assess the safety and efficacy of satralizumab monotherapy, Dr. Traboulsee and colleagues conducted SakuraStar, a randomized, double-blind, placebo-controlled trial.
Evaluating drug as monotherapy
The phase 3 trial enrolled 95 patients aged 18-74 years at 44 sites in 13 countries. The investigators included patients with AQP4-IgG–seropositive or –seronegative neuromyelitis optica using the 2006 Wingerchuk criteria or with AQP4-IgG–seropositive NMOSD with at least one event of longitudinally extensive myelitis or optic neuritis. The researchers limited the number of AQP4-IgG–seronegative patients to about 30% of the study population. Eligible participants had at least one NMOSD attack or relapse in the past 12 months and a score of 6.5 or less on the Expanded Disability Status Scale (EDSS). The investigators excluded patients with a clinical relapse in the 30 days before study baseline. Participants were randomly assigned 2:1 to receive satralizumab 120 mg or placebo subcutaneously at weeks 0, 2, 4, and every 4 weeks thereafter. Concomitant immunosuppressant use was prohibited, although corticosteroids and intravenous immunoglobulin were permitted as rescue therapy for the treatment of relapse.
The primary endpoint was time to first relapse, and the trial was designed to continue until 44 relapses occurred or for 1.5 years after the last patient entered the trial, whichever occurred first.
“Because even one NMOSD attack can have serious neurological consequences, this design allowed patients who had an attack on placebo to enter the open-label phase and receive the active drug,” the researchers wrote. “The trial design used unequal randomization to minimize exposure to placebo; because patients were not permitted to receive concomitant immunosuppressant treatment in this trial, the design limited the number of patients not receiving any treatment for the disorder. Placebo was selected with the consideration that no drugs were approved for the treatment of NMOSD when the trial was designed.” Recent trials of eculizumab, inebilizumab, and satralizumab have found that the agents are effective treatments for NMOSD. In 2019, the Food and Drug Administration approved eculizumab, a complement inhibitor, for the treatment of AQP4-IgG–seropositive NMOSD.
For the primary endpoint of SakuraStar, the researchers defined relapses as new or worsening objective neurologic symptoms with at least one of the following:
- Increase of 1 or more EDSS points from a baseline EDSS score of more than 0, or increase of 2 or more EDSS points from a baseline EDSS score of 0
- Increase of 2 or more points on at least one appropriate symptom-specific functional system score for pyramidal, cerebellar, brain stem, sensory, bowel or bladder, or a single eye
- Increase of 1 or more points on more than one symptom-specific functional system score with a baseline of at least 1
- Increase of 1 or more points on a single-eye symptom-specific functional system score with a baseline score of at least 1
In addition, symptoms had to be attributable to NMOSD; persist for more than 24 hours; and not be attributable to confounding clinical factors such as fever, infection, injury, change in mood, or adverse reactions to medications. Researchers assessed EDSS and functional system scores within 7 days of a patient reporting symptoms.
The double-blind treatment period ended 1.5 years after the last enrolled patient was assigned to satralizumab or placebo. More than 80% of the participants were women, including 73% of the satralizumab group and 97% of the placebo group. In all, 95 participants were assigned to a treatment between 2014 and 2017 – 63 to satralizumab and 32 to placebo. Relapses occurred in 19 patients receiving satralizumab (30%) and 16 receiving placebo (50%). The hazard ratio was 0.45.
“Patients treated with placebo showed a shorter time to relapse and a higher withdrawal rate than did patients treated with satralizumab,” wrote Dr. Traboulsee and colleagues. The Kaplan-Meier method suggested that 76% of patients on satralizumab had not relapsed at 48 weeks, compared with 62% of patients on placebo. And at 96 weeks, 72% of patients on satralizumab had not relapsed, compared with 51% of patients on placebo.
Among patients who were AQP4-IgG seropositive, the proportion with protocol-defined relapse was 22% in the satralizumab group versus 57% in the placebo group. Among patients who were AQP4-IgG seronegative, the proportion with a protocol-defined relapse was 46% in the satralizumab group versus 33% in the placebo group.
The most common adverse events were urinary tract infection and upper respiratory tract infection, and most adverse events were mild to moderate. A higher rate of severe adverse events was reported in the satralizumab group than in the placebo group (32.1 vs. 9.9 events per 100 patient-years). The investigators considered most of the severe adverse events unrelated to the study treatment. “None of the severe adverse events led to discontinuation of the study drug except one severe event of pneumonia in the satralizumab group,” the researchers wrote.
Data confirm efficacy of IL-6 blockade
“Satralizumab was well tolerated and no meaningful adverse effects from the drug were reported and no deaths occurred,” said Michael Levy, MD, PhD, director of the NMO clinic and research laboratory at Massachusetts General Hospital, Boston, in an accompanying editorial. “This trial of satralizumab was done shortly after the completion of a parallel trial of satralizumab in patients with NMOSD in which the same dose of satralizumab reduced the risk of relapse by 62%, compared with placebo. The main difference between these two trials is that, in the first published study, participants were permitted to use background immunotherapy; otherwise, the trial designs were nearly identical, and the enrolled participants are comparable. Together, the findings from these studies suggest that background therapy seems to provide only a small additional benefit to satralizumab alone.”
Dr. Levy also discussed findings from a phase 2 study of tocilizumab for the prevention of relapse in patients with NMOSD published in the same issue of the Lancet Neurology. The satralizumab and tocilizumab data have “confirmed that IL-6 blockade reduces the risk of relapse in patients with NMOSD,” Dr. Levy said. “IL-6 is a crucial component of the immune system, but when IL-6 production is altered during autoimmune attacks and sepsis, there can be severe consequences.”
The phase 2 trial of tocilizumab, which was described at the 2019 annual congress of the European Committee for Treatment and Research in Multiple Sclerosis, included 118 patients, 87% of whom were AQP4-IgG seropositive. Patients received intravenous tocilizumab or oral azathioprine for up to 60 weeks. Overall, 14% of patients in the tocilizumab group relapsed, compared with 47% of patients in the azathioprine group.
“The main differences between this trial of tocilizumab and the two satralizumab trials are that the tocilizumab was administered intravenously, rather than subcutaneously, the study duration was approximately 1 year, and the investigators were not masked to the treatment allocation,” Dr. Levy said. “Similar to satralizumab, adverse effects with tocilizumab were mild, including asymptomatic elevations in liver enzymes and an increased incidence of respiratory and urinary infections, with no significant differences identified between the tocilizumab and azathioprine groups.”
Various immunopathologic mechanisms may influence outcomes in NMOSD. While satralizumab and tocilizumab target IL-6, eculizumab is a C5 complement inhibitor and inebilizumab is a CD19 B-cell depleting monoclonal antibody, Dr. Levy said. “The safety concerns regarding these approaches are all substantially outweighed by the benefit of preventing NMOSD relapses.”
A need to understand AQP4-IgG–seronegative disease
SakuraStar “provides convincing data for the efficacy of satralizumab monotherapy in NMOSD with subgroup analysis showing that the benefit was seen in AQP4-IgG seropositive patients,” commented Dean M. Wingerchuk, MD, director of the division of multiple sclerosis and autoimmune neurology at the Mayo Clinic in Phoenix. “The results help confirm the key role of IL-6 in the pathobiology of AQP4-IgG–seropositive disease.”
Questions about AQP4-IgG seronegative disease remain. “The results are quite similar to the SakuraSky trial, in which satralizumab was used in conjunction with other background immunosuppressive therapies, suggesting that the primary benefit may be derived primarily from satralizumab. Both trials also showed that satralizumab did not benefit the NMOSD without AQP4-IgG subgroup though the subject numbers are rather small. We need to know more about the clinical and laboratory characteristics of the seronegative patients as they likely comprise a heterogeneous group. For example, did any of them have other autoantibodies such as MOG-IgG? Depending on the results, those details may help us understand the relative role of IL-6 in AQP4-IgG–seronegative subgroups, an important area of further study.”
SakuraStar was funded by Chugai Pharmaceutical, a member of the Roche group. Dr. Traboulsee reported grants, personal fees, and nonfinancial support from Chugai Pharmaceutical during the study, and several coauthors were employees of Chugai Pharmaceutical. Additional coauthors reported personal fees from Chugai, Roche, and other companies. Dr. Levy has received consulting fees from Alexion, Viela Bio, Chugai Pharmaceutical, Quest Diagnostics, and UCB Pharmaceuticals.
SOURCE: Traboulsee A et al. Lancet Neurol. 2020;19(5):402-12.