This Investor Sold $5 Million of a Biotech Stock Up 118% in a Year, but Here's Why It Still Seems Bullish on Shares

On February 17, 2026, OrbiMed Advisors reported selling 143,304 shares of Sionna Therapeutics (NASDAQ:SION), an estimated $5.43 million trade based on quarterly average pricing.

What happened

According to a Securities and Exchange Commission (SEC) filing dated February 17, 2026, OrbiMed Advisors reduced its Sionna Therapeutics position by 143,304 shares during the fourth quarter. The estimated transaction value is $5.43 million, calculated using the mean unadjusted closing price for the quarter. The quarter-end position value increased by $37.56 million, reflecting both trading activity and price appreciation.

What else to know

• OrbiMed Advisors’ Sionna Therapeutics holding now constitutes 2.99% of its 13F reportable AUM following the sale.
• Top holdings after the filing:
  • NASDAQ: EWTX: $385,091,379 (7.9% of AUM)
  • NYSE: LLY: $323,693,616 (6.7% of AUM)
  • NYSE: BSX: $230,680,255 (4.7% of AUM)
  • NASDAQ: SVA: $184,466,170 (3.8% of AUM)
  • NYSE: EW: $157,107,225 (3.2% of AUM)
• As of Friday, SION shares were priced at $37.32, up 118% over the past year and vastly outperforming the S&P 500’s roughly 20% gain in the same period.

Company overview

Company snapshot

• Sionna Therapeutics develops biopharmaceutical products focused on treatments for cystic fibrosis, targeting normalization of cystic fibrosis transmembrane conductance regulator (CFTR) function.
• The firm operates a research-driven business model, generating value through the discovery and clinical development of novel therapies, with revenue potential primarily from future product approvals and licensing.
• It serves healthcare providers, specialty clinics, and patients affected by cystic fibrosis, with a primary focus on the rare disease and biotechnology markets.

Sionna Therapeutics, Inc. is a biotechnology company specializing in the development of innovative therapies for cystic fibrosis. The company's strategy centers on advancing medicines that address the underlying cause of the disease by targeting CFTR protein dysfunction.

What this transaction means for investors

When a clinical-stage biotech stock more than doubles in a year, trimming a position can simply reflect risk management rather than fading conviction. That dynamic often appears in healthcare-focused portfolios, where investors balance high-upside drug development bets with more stable holdings across the broader healthcare ecosystem.

Sionna Therapeutics seems to fit squarely in that high-risk, high-reward category. The company is developing therapies designed to restore function of the CFTR protein, the underlying cause of cystic fibrosis. Unlike many biotech firms still searching for capital, Sionna is entering its next phase of clinical development with financial flexibility. The company ended 2025 with about $310 million in cash, cash equivalents, and marketable securities, which management expects will fund operations into 2028.

The pipeline is also progressing. A Phase 2a proof-of-concept trial evaluating its NBD1 stabilizer SION-719 is underway, while another early-stage trial studying combination therapies is expected to produce topline data in mid-2026. With the firm still commanding a nearly $150 million position within this portfolio, it really seems like this wasn’t a conviction call at all.

Jonathan Ponciano has no position in any of the stocks mentioned. The Motley Fool has positions in and recommends Edwards Lifesciences. The Motley Fool has a disclosure policy.