Sensei Biotherapeutics Inc. (SNSE) had quite the evening Thursday, rocketing 62.88% to $17.20 in after-hours trading. That's the kind of move that makes retail traders check their screens twice.

The stock had already closed the regular session at $10.56, up a respectable 21.38%. So we're looking at back-to-back momentum here, not just a random spike.

What's Behind the Move?

The action appears tied to regulatory filings from one of the company's major investors. On Thursday, Cambrian BioPharma Inc., which holds a 10% stake in Sensei, submitted two Form 144 filings with the Securities and Exchange Commission. These forms basically tell the SEC that someone intends to sell restricted shares.

The filings show Cambrian plans to sell 27,066 common shares valued at roughly $235,744. Both transactions will go through Fidelity Brokerage Services LLC.

Here's the context: those shares come from a total of 1.26 million common shares outstanding. So we're talking about a relatively small slice of the overall pie.

Recent Performance Trends

The Maryland-based clinical-stage biotechnology company has been on something of a run lately. Year to date, the stock is up 2.52%, which sounds modest until you zoom out. Over the past six months, Sensei has gained 46.26%.

The company carries a market capitalization of just $13.32 million, putting it firmly in micro-cap territory. Over the past 52 weeks, shares have traded in a wide range between $5 and $18.35.

According to market data, SNSE's momentum ranks in the 48th percentile, showing strong long-term gains alongside stable short and medium-term performance. Not exactly top-tier momentum, but respectable given the volatility typical of small biotech names.