Monitor for actual sale execution on Form 4 and any subsequent insider selling patterns. The large block from a pre-IPO holder could signal reduced conviction ahead of upcoming catalysts or data readouts.
Price Chart
Executive Summary
RA Capital Healthcare Fund LP, a 10% stockholder of Sionna Therapeutics, filed a Form 144 on September 17, 2026, indicating intent to sell up to 3,448,811 shares of common stock. The filing does not disclose the proposed sale price or dollar value, but the share count represents a material portion of the fund's reported holdings.
Key Facts
- RA Capital Healthcare Fund LP filed Form 144 to sell up to 3,448,811 shares of Sionna Therapeutics common stock.
- RA Capital is a 10% stockholder and director of the company.
- The shares were acquired through private transactions in February 2022, March 2024, and the IPO in February 2025.
- The filing does not specify the proposed sale price or total dollar value.
- The sale is planned for the open market via Goldman Sachs & Co.
Financial Impact
3,448,811 shares proposed for sale; dollar value not disclosed in filing.
Risk Factors
- Insider selling by a major holder may pressure the stock near-term.
- Form 144 is an intent to sell; the sale may not occur, but the filing itself signals the insider considered selling.
Investment Themes
Documents Analyzed
This report is based on 3 SEC documents filed with EDGAR.
| Document | Accession Number |
|---|---|
| 144 Filing (Primary) | 0001315082-26-000002 |
| Document: 0001315082-26-000002-index.html | 0001315082-26-000002 |
| Document: 0001315082-26-000002.txt | 0001315082-26-000002 |
Filters
| Type | Now | ||||
|---|---|---|---|---|---|
Sep 22, 2026 5w ago | Institutional Cluster | $6.02 $5.15 | ▼ −14.45% | ▼ −13.26% | $3.87 (−35.71%) |
Sep 21, 2026 5w ago | SC 13D/A | $6.02 $5.15 | ▲ +14.45% | ▲ +13.26% | $3.87 (+35.71%) |
Sep 17, 2026 6w ago | 144 | $5.96 $5.23 | ▲ +12.25% | ▲ +13.52% | $3.87 (+35.07%) |
Aug 10, 2026 11w ago | 8-K | $4.50 $5.91 | ▼ −31.33% | ▼ −31.38% | $3.87 (+14.00%) |
Aug 6, 2026 12w ago | 8-K | $49.61 $6.54 | ▼ −86.82% | ▼ −88.03% | $3.87 (−92.20%) |
Jul 9, 2026 16w ago | Insider Cluster | $45.29 $45.29 | · 0.00% | ▲ +0.56% | $3.87 (−91.46%) |
Jul 9, 2026 16w ago | Insider Cluster | $45.29 $45.29 | · 0.00% | ▼ −0.56% | $3.87 (+91.46%) |
Jul 7, 2026 16w ago | Insider Cluster | $44.00 $42.59 | ▲ +3.20% | ▲ +4.07% | $3.87 (+91.20%) |
Jul 2, 2026 17w ago | Insider Cluster | $43.12 $43.95 | ▲ +1.92% | ▲ +2.21% | $3.87 (−91.03%) |
Jun 11, 2026 20w ago | Institutional Cluster | $36.05 $36.73 | ▲ +1.89% | ▲ +1.45% | $3.87 (−89.26%) |
US Market Status
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