Armed with a phase 2 win for its lead drug zilucoplan in rare disease myasthenia gravis (MG), Ra Pharma has pressed the button on a public funding round that it hopes could raise up to $115 million.

Cambridge, Massachusetts-based Ra Pharma has reported top-line results, saying that a daily subcutaneous dose of the complement C5 inhibitor drug results in a significant reduction in symptom scores in patients with MG compared to placebo.

MG is a long-term autoimmune neuromuscular condition that causes muscle weakness, particularly affecting the face, but can also extend to the arms legs and neck in more severe cases, known as generalized MG. It can cause difficulties with swallowing, speaking and breathing and in some cases these can become severe—known as a myasthenic crisis—and require hospitalization.

Ra Pharma’s trial involved 44 patients with the generalized form of the disease, a group it estimates numbers around 60,000 people in the U.S., and the big question now is how the drug compares with Alexion’s blockbuster Soliris (eculizumab), which was approved for gMG by the FDA last year.

Using the QMG score—a physician-administered assessment of MG-related muscle weakness—the study showed that achieved a mean reduction of 2.8 points versus placebo after 12 weeks, as well as a 2.3-point reduction compared to control in the MG Activities of Daily Living (MG-ADL) scale.

Both results just met the criteria for statistical significance with p values of 0.05 and 0.04, respectively, but were "clinically meaningful", according to the company.

"Based on these data, we plan to engage with regulatory agencies, including the FDA, in the first half of 2019 regarding the design of a potential phase 3 clinical trial evaluating zilucoplan versus placebo in patients with gMG," it said in an SEC filing.

Ra Pharma is quick to point out that while Soliris is delivered via a 45-minute intravenous infusion every 14 days, zilucoplan can be self-administered by patients in a few seconds each day. That could make it useful for a broader population of around 30,000 patients in the US alone, extending the use of complement inhibitor therapy into newly-diagnosed patients, as well as those who have failed other treatments like cholinesterase inhibitors, steroids and immunosuppressants.

It estimated that could allow zilucoplan to target 10 times as many as Alexion’s drug, which is currently reserved as a last-line therapy for treatment-refractory patients, according to the biotech. It also reckons its top-line phase 2 data suggest an efficacy edge over its rival.

The latest fundraising comes two years after Ra Pharma’s upsized IPO, which raised $92 million, and is intended to give the company the resources it needs to take zilucoplan into the phase 3 program in gMG as well as other indications such as paroxysmal nocturnal hemoglobinuria (PNH).

PNH is a rare life-threatening disorder where red blood cells are mistakenly attacked and destroyed by the complement system, and Ra Pharma presented positive top-line results in this indication in February.

It also has early-stage clinical data suggesting zilucoplan could have a role to play in complement-mediated kidney disease.

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