Who Owns Your Doctor?

On October 13, Humana announced that BlackRock — through its HPS Investment Partners credit arm — would take a majority stake in a joint venture that owns nearly 150 of its CenterWell senior primary care clinics, in a transaction valued at roughly $2.8 billion. The world's largest asset manager now holds the controlling stake in a chain of doctors' offices serving Medicare patients, replacing the private equity firm Welsh, Carson, Anderson & Stowe, which built the position across two earlier joint ventures.

Four weeks before that deal was announced, six members of Congress introduced a bill that would drag exactly this kind of arrangement — and hundreds like it — into federal court.

The Stop Corporate Takeovers of Physicians Act (S. 5419 in the Senate, H.R. 10444 in the House), introduced on September 16 by Senators Ron Wyden, Jeff Merkley, and Elizabeth Warren alongside Representatives Val Hoyle, Alexandria Ocasio-Cortez, and Suhas Subramanyam, would create the first federal ban on the corporate practice of medicine in American history. The sponsors' case rests on one number: according to their fact sheet, more than 80 percent of U.S. physicians are now employed by corporate entities — hospitals, insurers, private equity-backed groups — up from 62 percent in 2019. The independent doctor's office, as a business model, is nearly extinct.

The quiet consolidation

No company illustrates the shift better than UnitedHealth Group. Its Optum arm counts roughly 90,000 physicians as employed or affiliated — the company's own investor-day figure — which works out to about one in ten American doctors. The great majority are affiliates in risk-sharing contracts rather than W-2 employees, a distinction that matters, because the bill goes after exactly that gray zone: control without formal ownership.

Most states have long had corporate-practice-of-medicine doctrines on the books. The workaround is equally old. A "friendly" physician nominally owns the professional corporation; a management services organization (MSO) — owned by the insurer, the private equity sponsor, or the telehealth platform — holds the management contract, the brand, the billing, and, through share-transfer agreements, effective control of the equity. The doctor owns the practice on paper. The MSO owns everything that matters.

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What the bill actually does

The federal bill, modeled on Oregon's SB 951 — signed by Governor Tina Kotek on June 9, 2025, and the strictest corporate-practice law in the nation — is aimed at the workaround, not just the headline ownership. Per the bill text and legal analyses of it:

• Majority physician ownership and control becomes mandatory. An entity not majority-owned and controlled by licensed clinicians — who must be licensed in-state and substantially engaged in actually delivering care — cannot own a medical practice, employ physicians, or practice medicine.
• The MSO toolkit gets dismantled. MSOs would be barred from controlling practice equity or assets, and from holding ultimate decision-making power over hiring and firing, staffing levels, physician schedules and compensation, time spent with patients, diagnostic coding, billing policy, prices, and payer contracts.
• Physician noncompetes and gag clauses are banned.
• Enforcement has teeth. Violations count as unfair or deceptive practices under the FTC Act, enforceable by the FTC, state attorneys general, and private plaintiffs — with exclusion from Medicare and Medicaid on the table.
• It reaches back. Unlike Oregon's law, which gave existing arrangements until 2029 to comply, the federal bill applies to existing MSO contracts after a one-year phase-in. Offending agreements become void and unenforceable.

One carve-out defines the political economy of the whole fight: hospitals and nonprofit health systems are exempt from the ownership ban. The largest employers of physicians in America keep their bid. The insurers, the private equity sponsors, and the asset managers lose theirs.

So the questions that matter for a portfolio: which listed companies actually carry this exposure, which supposed targets are quietly protected, and what do next week's midterms do to the odds?

The rest of this briefing is free — it just requires a free AlphaBriefing account: the ticker-by-ticker exposure map, the irony in the hospital exemption, and the three things to watch after November 3.

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