Almost looks like a standoff between buyers/holders and sellers
Volume is less than half of the 3-month daily average. There aren't many buyers at this price, but at the same time those who own ALNY and saw the huge bump in price on July 16th don't want to sell their shares either. If they don't sell afetr such a terrific pop in share price, how do they make a profit? Unless of course those holding shares are awaiting somespectacular news comes out of ALNY.
This stock is one good news or bad news away from a volatile swing in either direction.