RA Capital Healthcare Fund LP 4

What Happened
RA Capital Management, L.P. (reported as a 10% owner) acquired 6,060,606 shares of Acumen Pharmaceuticals, Inc. (ABOS) on 2026-03-16 via a grant/award (transaction code A). The shares were priced at $3.30 each, for a total reported value of $20,000,000. This is an acquisition (purchase/award) rather than a sale.

Key Details

• Transaction date: 2026-03-16; filing date: 2026-03-18 (filed within typical Form 4 timing).
• Price and amount: 6,060,606 shares @ $3.30 per share = $20,000,000.
• Transaction type: A (Grant, award or other acquisition).
• Shares owned after transaction: Not specified in the excerpt provided.
• Footnotes: Shares are held directly by RA Capital Healthcare Fund, L.P.; other related vehicles include RA Capital Nexus Fund II, L.P. and a separately managed account. The adviser (RA Capital Management, L.P.), its GP, and certain individuals disclaim beneficial ownership except to the extent of pecuniary interest.
• Remark: Laura Stoppel, a Principal of the Adviser, serves on Acumen’s board of directors.

Context
This filing reports an institutional-level acquisition by RA Capital’s funds/adviser — not an individual executive buy/sell. Institutional grants or acquisitions can reflect fund investment activity (financing, allocation, or compensation) rather than personal trading by company insiders. The presence of a fund principal on Acumen’s board is disclosed; the filing’s footnotes clarify how ownership and control are structured.