Biogen has plans to launch a global Phase IV clinical trial to assess the clinical benefit and safety of Spinraza (nusinersen) in infants and children with spinal muscular atrophy (SMA).

Named RESPOND, the study will involve patients with unmet clinical needs after treatment with Novartis’ gene therapy Zolgensma (onasemnogene abeparvovec).

SMA patients do not generate the required amount of survival motor neuron (SMN) protein, which is involved in maintaining motor neurons that support sitting, walking, and the basic functions of life.

The RESPOND trial will explore if Spinraza, which previously demonstrated efficacy, and its continuous SMN protein production, would also benefit patients who were previously on gene therapy.

To date, more than 10,000 SMA patients have been treated with Spinraza globally.

Biogen chief medical officer Maha Radhakrishnan said: “Available data now show that some patients in the long-term study of Zolgensma have moved on to treatment with Spinraza.

“We believe that, for certain patients, motor neurons may be insufficiently treated by this gene therapy, and we plan to initiate this study to understand the extent to which Spinraza may potentially improve outcomes.”

In a long-term study of Zolgensma, four out of ten patients have been subsequently treated with Spinraza, noted Biogen.

According to the planned study design, RESPOND will be performed as a two-year, open-label study to evaluate the safety and efficacy of Spinraza in patients previously treated with Zolgensma in order to further inform treatment decisions.

The primary study group will enrol 40 infants aged nine months or younger with two SMN2 copies and were treated with Zolgensma at six months old or younger.

A second group will involve 20 children and will capture data in patients with a broader age range.

Biogen intends to submit the study protocol to the regulatory authorities in the coming months and aims to start enrolment in the first quarter of next year.

In September last year, the company announced plans to evaluate a higher dose of its Spinraza (nusinersen) in a new Phase II/III study called DEVOTE.