Politan Exits Masimo: $826M Cashed Out at $180 in SC 13D/A

The Activist Who Won Masimo Just Took His Stake to Zero

Politan Capital Management reported 0 shares and 0.0% ownership of Masimo on June 11, 2026, one day after its 4,590,873 shares converted into roughly $826 million in cash. Amendment No. 17 to Politan’s Schedule 13D is the closing entry of one of the most watched activist campaigns in healthcare, and NexusAlert flagged it the same day it hit EDGAR.

What Happened

Danaher’s $9.9 billion acquisition of Masimo closed on June 10, 2026. Every outstanding share of $MASI common stock was cancelled and converted into the right to receive $180.00 in cash, a 38.3% premium to the $130.15 close on the last trading day before the deal was announced on February 17, 2026. Masimo is now a wholly owned Danaher subsidiary and the stock is leaving Nasdaq.

One day after the close, Politan Capital Management and its founder Quentin Koffey filed Amendment No. 17 to their Schedule 13D. The fund’s 4,590,873 shares converted into cash at closing, worth approximately $826 million. Even Koffey’s 1,119 restricted share units from his board service were cancelled and paid out at the same $180.00 per share. The reporting persons now hold zero shares and no voting power.

Four Years From First Stake to Zero

Politan disclosed its Masimo position in 2022 and spent the next two years in open conflict with founder and CEO Joe Kiani. Koffey and Michelle Brennan won two board seats in the June 2023 proxy contest. In September 2024, shareholders sided with Politan a second time and Kiani exited the company he founded. The board was rebuilt, and in February 2026 the refreshed company agreed to sell itself to Danaher.

To consumers, Masimo is best known as the medical device maker whose patent fight forced Apple to disable the Apple Watch blood oxygen feature in the United States. To filing readers, it has been the defining activist battleground in healthcare for three years running.

Is an Activist Exit a Sell Signal?

Not here, and the distinction matters. The filing carries an insider sell flag, and a screen that counts dispositions will read Amendment No. 17 as an $826 million insider sale. But nothing hit the open market. The shares were cancelled and converted into merger consideration at closing, at a fixed $180.00 that shareholders approved. An exit at merger close is the scoreboard, not a trade.

That is the misconception worth fixing. A 13D amendment going to zero can mean an activist is dumping a position, or it can mean the campaign is over and the fund is collecting in cash. The transaction code, the timing and the merger context tell you which one you are looking at. Here, every signal says completed campaign.

Activists don’t ring a bell at the top. They file Amendment No. 17.

The Bigger Pattern: Campaigns Live in 13D Amendments

The entire arc of the Politan campaign, from first stake through two proxy wars to the final $826 million payout, is written in one filing chain: a Schedule 13D and its seventeen amendments. The headlines covered the drama. The amendments carried the positions, the agreements and the exit, usually a day or more before the stories were written.

NexusAlert flagged this 13D/A as high severity with merger completion, insider sell and ownership change flags on June 11, the same day it was filed. If you track activist names, watching the amendment chain is how you see campaigns start, escalate and cash out before the write-ups land.

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Sources

• Danaher To Acquire Masimo Corporation (Danaher Investor Relations, February 17, 2026)
• Danaher To Acquire Masimo Corporation (PR Newswire)
• Masimo SC 13D/A Amendment No. 17 summary (StockTitan)
• Masimo Completes Cash Merger and Plans Nasdaq Delisting (TipRanks)
• Danaher’s $9.9B Masimo Deal Marks One of 2026’s Largest Medtech Buyouts (24/7 Wall St.)
• Masimo Corp filings on SEC EDGAR (CIK 0000937556)