ALNY·Alnylam Pharmaceuticals, Inc.

Realized volatility (21d)

42.2% 46th pct

Below its peak

-51.2%

vs 200-day average

-23.5%

Up days (1y)

48%

Alnylam Pharmaceuticals, Inc. is currently running 42.2% annualised volatility over the last 21 sessions. Measured against ALNY's own 13 years of daily returns rather than a market-wide average, that is the 46th percentile — close to its own typical level, against a typical reading of 43.6%. The distinction matters because a number that looks calm for one stock is turbulent for another, and the absolute figure on its own tells you neither.

ALNY is trading -51.2% below its running peak. Across 12 full years on file, its median worst-drawdown-in-a-year was -30.6%, and the deepest was -66.9% in 2016. The current drawdown is already deeper than this stock's typical annual low point, which puts it in the part of its range where past recoveries began — and where past declines also continued.

Price sits -23.5% from its 200-day moving average. Against every other day in its history, that gap ranks at the 10th percentile — a narrower gap than it typically runs. Over the past year ALNY closed higher on 48% of sessions, and it is currently 1 session into a falling streak.

On September specifically: over 13 years of records, ALNY finished the month higher 5 of 13 times, with a median return of -1.8% and an average of -0.3%. Its strongest month historically has been August at +9.6% on average, its weakest October at -5.4%. Seasonality is a weak signal on its own — a decade is a small sample and regimes change — but it is a real distribution rather than a rule of thumb.

Overnight risk is measurable too: ALNY has opened more than 2% away from the prior close in 240 of 3,266 sessions (7.3% of the time), with the largest gaps running +40.9% and -18.6%. For anyone holding through an event, that rate is a better guide to overnight exposure than the intraday range.

Across the last 3 dated reports on file, ALNY moved an average of 3.3% in the session after earnings, closing higher 1 of those 3 times, with a median move of -0.8% and a largest of -5.6%.

All figures computed from 3,267 daily closes between 2013-09-19 and 2026-09-18, split-adjusted, recomputed daily. Percentiles are against ALNY's own 13-year history, not a peer group or index.