# RTW Investments, LP 13F holdings

> Latest reported SEC 13F equity book. Teaser: top 10 of 88 long-equity positions.
> CIK 1493215. Latest filing Q1 2026, as of quarter end 2026-03-31. Long-equity book $10.0B.

## Top holdings (teaser)

| # | Ticker | Issuer | Value | % of book | Change |
|---|--------|--------|-------|-----------|--------|
| 1 | MDGL | Madrigal Pharmaceuticals Inc | $1.0B | 10.4% | Held |
| 2 | INSM | Insmed Inc | $791.9M | 7.9% | Added |
| 3 | PTGX | Protagonist Therapeutics Inc | $533.2M | 5.3% | Held |
| 4 | PTCT | PTC Therapeutics Inc | $527.8M | 5.3% | Held |
| 5 | ARGX | Argenx SE | $518.1M | 5.2% | Added |
| 6 | CGON | CG Oncology Inc | $472.7M | 4.7% | Added |
| 7 | CELC | Celcuity Inc | $346.9M | 3.5% | Added |
| 8 | TNGX | Tango Therapeutics Inc | $278.2M | 2.8% | Added |
| 9 | ERAS | Erasca Inc | $261.4M | 2.6% | Added |
| 10 | NTRA | Natera Inc | $250.0M | 2.5% | Reduced |

## Latest moves

Bought: WAY, CADL, AKTS
Sold: NTRA, COGT, APLSUSD

Counts and totals reflect the 13F filers and securities Arkolith tracks, not the entire institutional universe. Option legs are excluded from the book above.

## Full data via the API and MCP

This page is a teaser. The complete book, full quarter-over-quarter history, and per-datapoint
provenance are available through the metered REST API and MCP server.

- Endpoint: https://arkolith.com/api/mcp (transport: streamable-http)
- Auth: Bearer API key. Mint one and copy a ready-to-paste command at https://arkolith.com/connect
- Claude Code: `claude mcp add --transport http arkolith https://arkolith.com/api/mcp --header "Authorization: Bearer YOUR_API_KEY"`
- Discovery: `tools/list` is free; `tools/call` is metered by credits.

### Machine-readable
- Tool catalog JSON: https://arkolith.com/api/mcp/catalog
- MCP descriptor: https://arkolith.com/.well-known/mcp.json
- OpenAPI 3.1 REST spec: https://arkolith.com/openapi.json
- Full LLM guide: https://arkolith.com/llms-full.txt
- Human docs: https://arkolith.com/docs

## Source and method

- Source: SEC EDGAR 13F-HR (public domain). Long-equity positions only (option legs excluded). Filed quarterly, about a 45-day lag.
- Primary source: https://www.sec.gov/Archives/edgar/data/1493215/000149321526000130/xslForm13F_X02/primary_doc.xml
- Human page: https://arkolith.com/fund/rtw-investments-lp-1493215
- Per-datapoint lineage: call the `provenance.get` MCP tool for the source URL and fetch history behind any figure.

Paid product with a one-time evaluation grant at signup (no card to evaluate). Most calls cost 1 credit (~$0.01); heavier point-in-time / cross-source tools cost more.

_Latest disclosed public filings. Data, not investment advice._