Chugai preps filings for IL-6 drug in rare disease, chasing Soliris

Chugai has the positive phase 3 data it needs to file IL-6-targeting antibody satralizumab for approval in neuromyelitis optica spectrum disorder (NMOSD), a rare autoimmune disease, next year.

The Japanese drugmaker now has two positive phase 3 studies backing the efficacy and safety of the antibody in the disorder, which causes inflammation of the optic nerves and spinal cord and leads to progressive deterioration in vision and motor function that in some cases can be fatal.

Despite treatment with immunosuppressants, sometimes in conjunction with steroids, patients with NMOSD typically suffer frequent relapses that exacerbate symptoms and can lead to them going blind and becoming wheelchair-bound.

There are no approved treatments for the disease, which is estimated to affect up to four people per 100,000, and it is sometimes misdiagnosed as multiple sclerosis.

The latest SAkuraStar data—reported at the ECTRIMS conference in Berlin—showed satralizumab as a monotherapy met the primary objective of significantly extending the time to first-relapse compared to placebo, and also reduced the overall risk of relapse. Chugai isn’t revealing the full data set just yet but says it will do so at the future medical conference.

The results back up the SAkuraSKY trial data reported in October that showed adding satralizumab (SA237) to standard therapy reduced the risk of these relapses by 62% compared to standard therapy plus placebo. After 48 weeks, almost 89% of patients on the drug were relapse-free, compared to 78% of the placebo group, and after 96 weeks the proportions were 66% and 59%, respectively.

The new data are also good news for Chugai’s strategic alliance partner Roche, which licensed worldwide satralizumab rights two years ago, with the exception of Japan, South Korea and Taiwan, China.

Chugai’s co-head of project and life cycle management, Yasushi Ito, said the company will "work diligently to prepare for regulatory filing so that we can offer a new treatment option to patients with NMOSD as soon as possible." It’s estimated that the market for NMOSD drugs could be worth about $500 million a year.

Satralizumab may not be able to reach the market for NMOSD first, however, as Alexion is also in the final stages of developing its blockbuster anti-complement C5 drug Soliris (eculizumab) after a positive phase 3 trial, and said in September it was preparing to file for approval.

That lead may not prove decisive, however. Soliris’ data set has been generated exclusively in patients with anti-aquaporin-4 (AQP4) auto antibody-positive NMOSD, while Chugai’s monotherapy trial showed a benefit in both AQP4-positive and negative subjects. The Japanese company’s drug is also easier to administer, given as a monthly subcutaneous injection after an initial loading phase, while Soliris is administered every two weeks intravenously.

Meanwhile, other competition is waiting in the wings. AstraZeneca’s Medimmune division has a CD19-targeting drug called MEDI-551 (inebilizumab) in phase 2/3 testing for NMOSD with results due next summer. The trial is testing an IV dose of the drug at baseline and after two weeks, then every 26 weeks thereafter.

It's worth noting that the window of opportunity for all the drugs in development for NMOSD may also be fairly short, as Soliris is heading for patent expiries in the U.S. and EU in 2021 and 2020, respectively, after which cheaper biosimilars could reach the market.

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