Comparable stake leader
Madison Avenue Partners, LP
SEC ownership of ACELYRIN, Inc.
Top holders, 13D/G large-stake signals, insider positions, and transaction flow tied to CIK 0001962918.
Disclosed value leader
Westlake BioPartners Fund II, L.P.
Comparable rows
4/14
Latest evidence
21 May 2025
- Parsed ownership sources
-
13D/G and 3/4/5
Source: Parsed SEC ownership filingsUse: Compare filing families carefully
- Largest SEC-reported holder
-
Madison Avenue Partners, LP
Ranking: Comparable ownership first, then disclosed value
- Comparable ownership rows
-
4 of 14
Meaning: Rows with safely comparable ownership %
- Latest 13D/G holder
-
Madison Avenue Partners, LP
Source: Latest parsed Schedule 13D/G stake
- Latest parsed ownership date
-
21 May 2025
Freshness: Most recent filing date in this holder set
- Issuer CIK
- 0001962918
- Issuer location
- Agoura Hills, CA
Ownership snapshot
CIK-linked ownership evidence from parsed SEC filings.
3 signals
Issuer
Names, identifiers, and filing context for this profile.
2 identity fields
Ownership snapshot
Top shareholders of ACELYRIN, Inc. (13F + 13D/G + 3/4/5)
Grouped by holder across the latest SEC ownership disclosures. Start with comparable ownership when available, then verify the linked 13F, 13D/G, or 3/4/5 evidence.
Comparable stake leader
Madison Avenue Partners, LP
Disclosed value leader
Westlake BioPartners Fund...
Comparable rows
4/14
Latest evidence
21 May 2025
13D/G
3/4/5
Lead comparable stake: 5.1%
10 rows are not safely comparable across share classes.
13D/G row: Madison Avenue Partners, LP
Showing 1-8 of 14 holder rows.
Quick read
Madison Avenue Partners, LP leads the comparable SEC ownership view at 5.1%.
4 of 14 rows have a safely comparable ownership percentage. Use this as a filing-backed starting point, then open the detailed table for source links, reporting role, position value, share count, and filing date.
Open SEC evidence
Opens Madison Avenue Partners, LP's linked filing trail.
Comparable ownership
Top 4
Madison Avenue Partners, LP
5.1%
INTEGRATED CORE STRATEGIES (US) LLC
4.7%
T. Rowe Price Investment Manageme...
4.6%
CITADEL ADVISORS LLC
4.2%
Ownership % is shown only when SEC disclosures are safely comparable across share classes.
Detailed SEC evidence table Showing 1-8 of 14 holder rows
| Holder | Evidence | Ownership % | Position | 12M Net Δ | As of |
|---|---|---|---|---|---|
| Madison Avenue Partners, LP |
13D/G
|
5.1%
|
$12,468,687
5,089,260 shares
|
$0 | 29 Apr 2025 |
| INTEGRATED CORE STRATEGIES (US) LLC |
13D/G
|
4.7%
|
$11,550,285
4,714,402 shares
|
$0 | 31 Dec 2024 |
| T. Rowe Price Investment Management, Inc. |
13D/G
|
4.6%
|
$11,395,024
4,651,030 shares
|
-$20,141,680 | 28 Feb 2025 |
| CITADEL ADVISORS LLC |
13D/G
Kenneth Griffin
|
4.2%
|
$10,335,933
4,218,748 shares
|
$0 | 31 Dec 2024 |
| Westlake BioPartners Fund II, L.P. |
3/4/5
10%+ Owner
|
—
class O/S missing
|
$72,519,930
9,790,729 shares
|
— | 09 May 2023 |
| Shao-Lee Lin |
3/4/5
Chief Executive Officer, Director
|
—
mixed-class rows
|
$10,488,913
1,995,942 shares
mixed-class rows
|
— | 01 Apr 2024 |
| Paul Peloso |
3/4/5
Chief Medical Officer
|
—
class O/S missing
|
$1,189,890
160,644 shares
|
— | 04 Oct 2023 |
| Ronald Oyston |
3/4/5
Chief People Officer
|
—
mixed-class rows
|
$1,047,039
264,932 shares
mixed-class rows
|
— | 09 Jan 2024 |
How to read this table
Rows are grouped by holder and ranked first by SEC-reported ownership % when it is safely comparable, then by disclosed holdings value. — indicates unavailable or non-comparable values; "mixed-class rows" means the latest filing spans non-comparable classes.
Forms 3/4/5 flow
Insider trading overview
Insider buy and sell flow is broadly balanced over the last 12 months. No Buy or Sell transactions have been reported since 27 Jun 2025.
Buys
$0
Insiders: 0
Sells
$0
Insiders: 0
Net
$0
Shares: 0
Window
Last 12 months
4 rolling buckets
Buy value
Sell value
Shares: 0
Shares: 0
| Window (months) | Buy shares | Sell shares | Buy value | Sell value | Net value |
|---|---|---|---|---|---|
| 0-3 | 0 | 0 | $0 | $0 | $0 |
| 3-6 | 0 | 0 | $0 | $0 | $0 |
| 6-9 | 0 | 0 | $0 | $0 | $0 |
| 9-12 | 0 | 0 | $0 | $0 | $0 |
Reporting owners
Insider holders from Forms 3/4/5
Showing 1-20 of 20 reporting-owner rows connected to ACELYRIN, Inc.. Open a relationship link for the CIK-to-CIK filing trail.
Rows
20
Largest Forms 3/4/5 holder
Westlake BioPartners Fund II, L.P.
Net 12M change
$0
Latest report
21 May 2025
Recent insider transactions for ACELYRIN, Inc.
Showing up to 300 recent insider transactions from the last 12 months.
| Insider | Symbol | Class | Transaction | % | SEC-reported value | SEC-reported price | Shares | Shares owned | Date | Ownership |
|---|---|---|---|---|---|---|---|---|---|---|
| No insider transactions were found in the last 12 months for this issuer. | ||||||||||
* marks a reported price that did not pass the local price check.