=Biogen (BIIB) reported earnings on Tue 25 July 2017 (b/o)

• Ionis Pharmaceuticals (IONS) -- Biogen's partner on the spinal drug

Biogen (BIIB) clung to gains early Tuesday after its Ionis Pharmaceuticals (IONS)-partnered spinal drug nearly tripled expectations in the second quarter, leading to a 4% guidance boost.

Sales of Spinraza, the Biogen-Ionis drug used to treat spinal muscular atrophy, came in at $203 million, obliterating analyst views for $70 million, Evercore analyst Umer Raffat wrote in a note to clients. Revenue from that drug grew 328% quarter over quarter.

U.S. sales comprised $195 million. Biogen has also built up $30 million in inventory. Raffat cautioned not to read through too far on Spinraza sales which are front-loaded. The first eight weeks cost $500,000 per patient with $250,000 over the next 32 weeks.

For the second quarter ended June 30, Biogen reported adjusted income of $5.04 per share on revenue of $3.1 billion, topping consensus views for $4.41 a share on $2.81 billion in sales. On a year-over-year basis, revenue grew 6% though profits sank 3.3%.

In afternoon trading on the stock market today, Biogen ticked up 10 cents to 284.80, after gaining as much as 4.3% before the open. Shares hit their highest point since April 25 while biotech stocks were generally flat early Tuesday.