FDA approves intramuscular version of Biogen MS drug Plegridy

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The FDA's approval of an intramuscular formulation of Biogen’s multiple sclerosis drug Plegridy provides the company with a new version to push as it tries to return Plegridy to growth. (Biogen)

The FDA has approved an intramuscular formulation of Biogen’s multiple sclerosis drug Plegridy. Biogen is framing the formulation as a way for relapsing MS patients to treat their conditions without suffering the injection site reactions associated with subcutaneous administration.

Subcutaneous Plegridy won approval in 2014 and received a label that cited injection site reactions as an issue for users of the medicine. In clinical trials, the incidence of injection site reactions in the Plegridy group was 66%, versus 11% in the placebo cohort. The incidence of severe reactions was 3% among users of Plegridy. One of the 1,468 patients suffered injection site necrosis.

The case of injection site necrosis was resolved with standard medical treatment, but the FDA took the reactions seriously enough to list them in the warnings and precautions section of the label. The FDA advises patients who suffer necrosis to change injection site or discontinue treatment. 

Biogen’s intramuscular formulation presents patients with a third option. In a clinical trial, 14.4% of patients who used the intramuscular formulation experienced injection site reactions, compared to 32.1% of their peers on the subcutaneous product. With the trial finding the intramuscular version is bioequivalent and otherwise has a similar safety profile, the FDA granted it approval.

The approval, which comes weeks after the EU authorized the formulation, provides Biogen with a new version to push as it tries to return Plegridy to growth. Sales of Plegridy fell in every quarter of 2020, causing full-year product revenue to come in down 11.5% at $385.6 million. 

Plegridy sales began to fall before the pandemic, contributing to a fall in interferon revenues in 2019. The interferon franchise has suffered as patients have transitioned to oral therapies. The new formulation won’t stop that transition but may help keep some patients on Plegridy. Talking to investors last year, Biogen Chief Medical Officer Alfred Sandrock, M.D., Ph.D., said “tolerability, including injection site reactions, has been the leading cause of discontinuation.”