** Biogen BIIB.O said on Thursday it would move its experimental Alzheimer's drug diranersen into late-stage development though it missed the main goal in a mid-stage study.

QUESTIONS REMAIN

** Cantor Fitzgerald ("overweight," PT: $206) says it is "amongst those who are skeptical" of BIIB's decision to advance its Alzheimer's program, calling it a risky move based on hard-to-interpret mid-stage data

** BMO Capital Markets ("market perform," PT: $196) says the lack of clarity does little to assure investors; adds questions around the driver of lack of a dose response and the magnitude of cognitive benefits remain unanswered

** J.P. Morgan ("neutral") says it needs full mid-stage data, expected in July, to better assess the drug's profile and understand the unclear or negative dose-response seen in the study

** Bernstein ("market perform," PT: $200) says it is skeptical that no quantitative results were disclosed in the topline update, calling the lack of numbers unusual