The CEO of Alnylam Pharmaceuticals saw his compensation drop precipitously in 2016 as the Cambridge biotech lost about half of its market value, according to a federal filing.

John Maraganore received about $1.7 million in total compensation in 2016, down from nearly $8.3 million in 2015, a decrease of nearly 80 percent, according to the filing on Friday. The pay cut was driven largely by a sharp decrease in his option awards, which fell from $7.1 million to approximately $621,000 last year.

The…