The takeaway
Sensei Biotherapeutics Inc shows a pronounced seasonal pattern over 5 years of data — strongest in December (+0.9%) and softest in October (−9.0%).
Right now
In July, the stock has fallen 40% of years, averaging −5.8%, roughly 8.0 pts behind the S&P 500.
The full picture
Sensei Biotherapeutics Inc's most dependable month has been December, higher in 3 of 5 years; October has been its least reliable, up just 0% of the time.
| Year | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Win rate % | ||||||||||||
| Median return % | ||||||||||||
| 2025 | ||||||||||||
| 2024 | ||||||||||||
| 2023 | ||||||||||||
| 2022 | ||||||||||||
| 2021 | — |
Month by month
Across the year the stock has stayed close to the S&P 500 — no single month stands out as a real edge.
“vs S&P” is Sensei Biotherapeutics Inc’s average for a month minus the S&P 500’s average for that same month — isolating Sensei Biotherapeutics Inc’s own seasonal edge from broad market drift.
Reality check
Over the last 5 years, December has closed higher 60% of the time versus 60% across the last 5 years — the pattern is holding.
Figures are the typical (median) December return and how often it rose — the last 5 years versus the last 5(the heatmap’s default window). This verdict stays anchored to that 5-year window even if you zoom the chart, so it never disagrees with the badges above.
In plain English
The year leans December's way without overwhelming the rest of it: the stock has closed higher in 3 of 5 Decembers, its most dependable month if not a dominant one.
Its average (+0.9%) and median (+0.3%) land within a hair of each other — the tell of steady, year-after-year gains rather than one outlier doing the work. That reliability comes with real swings, mind — even December ranges by 14.4% from year to year, so any single year can land far from the average. Set against the S&P 500, mind, December is close to a wash — the gain mirrors the market more than it beats it.
On the other side of the ledger, October has been the soft spot — the weakest of 11 months that average a loss (−9.0%), and the edge isn't year-round — the stock has trailed the S&P 500 in May, October, and March. Its roughest month on record was a −41.3% May in 2024 — a reminder of how hard even a seasonal name can fall.
Treat it as a tendency rather than a rule — seasonality describes the past, not a promise. With a short 5-year record and returns that swing hard year to year, the signal is best held loosely.
Short answers on the stock's best month (December), its worst (October), and whether it really trades seasonally.
Yes, to a pronounced degree. Since 2021 its best month (December, +0.9%) has run well ahead of its worst (October, −9.0%) — the heatmap above shows how steady that gap has been year to year.
December has been the strongest, averaging +0.9% and closing higher in 3 of 5 years since 2021.
It's the weakest, averaging −9.0% — historically a soft spot, though it still varies from year to year.
Explore
These names have the strongest July track records on record — a starting point for comparison.
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