Dive Brief:

• While Wall Street holds its breath for highly anticipated data on Biogen's Alzheimer's candidate BAN2401 due Thursday, the big biotech reported another quarter with its spinal muscular atrophy drug Spinraza franchise serving as a the main growth driver.
• Third quarter Spinraza revenue reached $468 million, up 10% from the second quarter and almost 73% year over year. Biogen's total revenue from July through September was $3.44 billion, a 12% increase from the same period in 2017.
• Spinraza's approval in late 2016 made it the first and only SMA treatment with a Food and Drug Administration nod. But rival medicines are encroaching. AveXis, which Novartis recently bought for $8.7 billion, has a gene therapy for the rare muscular disorder that could hit the market next year. Meanwhile, Roche and partner PTC Therapeutics are developing an oral SMA medicine.

Dive Insight:

Biogen on its call dodged several questions about updated clinical results for BAN2401, asking analysts to be patient until they're released later this week at the annual Clinical Trials of Alzheimer's Disease conference.

The interest was expected, given that Alzheimer's is one of the biotech's two main therapeutic focuses, with the other being multiple sclerosis.

That focus has caused some investor concern as of late, with intensifying competition in the MS market and risky nature of Alzheimer's drug development. Spinraza (nusinersen), therefore, has become a source of relief and near-term growth.

The high expectations have brought with them some scrutiny, however. Last year, analysts appeared unnerved after Biogen reported that U.S. Spinraza sales were essentially flat between the second and third quarter despite rapid uptake of the drug. Spinraza sales would disappoint again in early 2018, as first quarter sales missed Wall Street expectations.

Company execs were quick to explain, both on previous earnings calls and Tuesday's, that while Spinraza sales have experienced periods of stagnation in the U.S., they're growing more rapidly elsewhere. CEO Michel Vounatsos said the drug is doing well in Japan and core European markets, and tapping in larger parts of the patient population in Latin America.

As for the U.S., Vounatsos highlighted how Spinraza rollout is gaining momentum among adult patients, which Biogen estimates comprise about 60% of the 9,000 SMA patients.

But the biotech may soon have competition.

Novartis intends to file AVXS-101 sometime this year, meaning it could launch in 2019 should it clear regulators' desks. The gene therapy aims to provide a functional copy of the defective gene responsible for SMA. In a small clinical trial, 11 of 12 patients treated with a higher dose of the therapy were able to sit without needing help.

Biogen is working on gene therapies too, but has run into some barriers. Earlier this year, the company said it received notice that the FDA placed its preclinical SMA gene therapy on hold. Execs declined to comment on interactions with regulators concerning the hold, but said the setback seems "program-specific" rather than reflective of Biogen's larger gene therapy research.

Roche and PTC could also put Spinraza sales at risk.

Just this month, the companies released data from a pair of Phase 2/3 studies showing their drug risdiplam helped with muscle strength and motor function among a variety of SMA patients. Additionally, risdiplam's oral dosage could prove advantageous compared to the intrathecally administered Spinraza.

"We're aware of the data that Roche and PTC have presented around their oral compound. We know that the field is very interested in the long-term safety and tolerability of that compound, as our we," Biogen said on the call, though the company noted far more patients — around 6,000 in total — have been treated with Spinraza versus other therapies.

Biogen execs also pointed to recently updated data from the open-label NURTURE study of Spinraza in presymptomatic SMA infants. As of May, 100% of study's 25 participants were able to sit independently, while 77% were able to walk independently

"We're very aware of the other competitive programs. It's early days in a lot of those, and like I mentioned we know the field is very interested in the long-term safety and tolerability of the orals," Vounatsos said Tuesday. "We know there are questions around the dose selection that will ultimately be used there and to date it's a relatively small number of patients, but we are certainly staying aware of it."