The incredible story of United Therapeutics

United Therapeutics should not exist. On paper it is an unlikely company: a biotechnology firm worth north of $20 billion whose entire commercial engine runs, more or less, on a single molecule the world’s largest drug companies judged not worth developing. It was founded by Martine Rothblatt, who had no pharmaceutical background and entered the industry for the most personal reason imaginable, to keep her own daughter alive.

The line that best captures Rothblatt’s mindset is one she absorbed at UCLA’s Anderson School: “identify the corridors of indifference and run like hell down them.” Pulmonary arterial hypertension in the mid-1990s was exactly that, a disease so rare and lethal that the incumbents had already decided the market was too small to fight over.

Here is the thing worth noting before the story even starts: United Therapeutics is not, at heart, a drug-discovery company. The molecule at its center had already been discovered and shelved before UTHR existed. What Rothblatt brought was a different appetite for a disease most had written off as too small to matter: pulmonary arterial hypertension.

PAH occurs when the small pulmonary arteries progressively remodel. The intima and media proliferate, and in advanced disease the arterioles develop the hallmark plexiform lesions. Pulmonary vascular resistance rises until the chronically pressure-overloaded right ventricle decompensates and fails. When Jenesis Rothblatt, Martine’s daughter, was diagnosed in the early 1990s, none of this was treatable. Median survival was roughly three years from diagnosis, and the only pharmacologic option was high-dose calcium channel blockers, which benefit only the ~10% with acute vasoreactivity on right heart catheterization. Otherwise, the only definitive option was lung or heart-lung transplantation.

Modern PAH therapy is built almost entirely on three molecular pathways: prostacyclin, endothelin, and nitric oxide. The prostacyclin pathway is deficient, and is addressed by prostacyclin itself (epoprostenol), by its analogues (treprostinil and iloprost), and by oral receptor agonists (selexipag). The endothelin pathway is overactive, driven by excess endothelin-1, and is blocked by the endothelin receptor antagonists (bosentan, ambrisentan and macitentan). The nitric oxide pathway is underactive, leaving its second messenger cGMP too low, which can be restored either by blocking cGMP breakdown with PDE5 inhibitors (sildenafil, tadalafil) or by stimulating its production with the soluble guanylate cyclase stimulator (riociguat).

Rewind to 1994, and the field looks very different. There is essentially one drug in trials: epoprostenol, a synthetic prostacyclin that works but is also one of the most demanding medicines in cardiology. Prostacyclin is hydrolytically unstable, with a plasma half-life of only a few minutes, so it can be neither given orally nor dosed intermittently. It has to be delivered as a continuous infusion through a central venous catheter, reconstituted daily and kept cold. Any interruption, a kinked line or a pump failure risks rebound pulmonary hypertension and hemodynamic collapse. This was the life that awaited Jenesis Rothblatt.

The thing to understand about Martine Rothblatt is that she had already done the impossible once: she’d built a satellite-radio company, the one that became SiriusXM, from nothing. So she is not the kind of parent who waits. Instead she read everything she can get her hands on, starts a foundation, and builds a list of the world’s leading pulmonary hypertension specialists. One name keeps coming up: Robyn Barst at Columbia, whose pivotal trial had just won Flolan (epoprostenol) its FDA approval. Rothblatt brings Jenesis to her, and Barst drops the tip that becomes the whole company: there is a better molecule. Someone had built a more stable version of prostacyclin, and then shelved it.

The shelved molecule was real, and good. It came out of Burroughs Wellcome, the same lab where prostacyclin had been discovered in 1976. Its chemists had engineered out the labile enol-ether oxygen in its bicyclic ring and replaced it with a metabolically stable, all-carbon benzindene ring system. The resulting molecule, treprostinil, was stable at room temperature, with a half-life of roughly four hours instead of minutes. That stability is what unlocked everything that followed: a molecule you could deliver subcutaneously, by inhalation, or orally.

So why is a molecule this good sitting in a drawer? Portfolio math. Burroughs Wellcome had developed it and then merged into Glaxo in 1995 but Glaxo already owned Flolan. Building a second prostacyclin for an orphan disease, meant spending money to cannibalize a franchise it already controlled, for a market of a few thousand patients. Glaxo, after much convincing, licenses the rights to Rothblatt in exchange for payments plus a royalty on sales, keeping a risk-free claim on any upside without spending another dollar. And as Remodulin scaled into the hundreds of millions of dollars in sales and that royalty paid out for years.

Glaxo failed to see the value themselves. Instead it took someone whose return on investment was her own daughter’s life to price it differently. To turn the ‘baggie of white powder’ into a drug, Rothblatt recruited James Crow, the Burroughs scientist who had run the program. United Therapeutics is incorporated in 1996 with Crow as its co-founder and president. Rothblatt pulls worldwide rights to the molecule, now called treprostinil, and then buys Synquest, the firm that can manufacture the active ingredient, so that she has secured every link in the chain: the rights, the chemist and the API.

A licensed powder is not a drug. To put a medicine in her daughter’s hands, she has to run the registration trial. And the endpoint she has to beat is strikingly modest. PAH has no elegant biomarker; instead efficacy is measured by the six-minute walk distance: you put a patient in a corridor with a stopwatch and measure how far they get in six minutes. The trial involved 470 patients over twelve weeks and was double-blind measuring continuous subcutaneous treprostinil against placebo. And then the data comes in, and it barely works. The placebo-corrected improvement in six-minute walk distance is sixteen meters. Sixteen. Real, statistically significant, but nobody’s idea of a miracle.

There is a catch, too, and it matters. The drug that frees you from a line still has to go in somewhere, and subcutaneous treprostinil hurts: roughly 85% of patients report infusion-site pain, against 27% on placebo, sometimes badly enough to force discontinuation. The molecule is more stable and more portable. It is not yet comfortable.

However, in an orphan condition with a brutal natural history and almost nothing on the shelf, “small but real” is approvable. In May 2002 treprostinil becomes Remodulin, UTHR’s first product, and the first new prostacyclin for PAH since Flolan. A small market can also be a strength, offering structural pricing powder, in this case a tiny, identifiable population, chronic, lifelong use; high annual cost per patient and speciality distribution that other competitors cannot easily replicate.

Over the next two decade, UTHR created additional value for the stability and portability of treprostinil: subcutaneous and intravenous (Remodulin), inhaled (Tyvaso, first as a nebulized solution, then as a dry-powder inhaler, Tyvaso DPI), and oral (Orenitram). Each new route resets two clocks at once. It opens a fresh patent estate, method-of-administration and device patents that run years past the original composition of matter, with one Tyvaso DPI patent extending into the late 2030s and it earns new regulatory exclusivity, with the dry-powder form carrying a three-year exclusivity of its own.

On top of that, UTHR keeps enlarging the addressable disease: the inhaled form moved beyond PAH into pulmonary hypertension associated with interstitial lung disease (the INCREASE trial), and idiopathic pulmonary fibrosis (the TETON program). The moat was orphan exclusivity, a controlled supply chain, formulation-and-device IP, and serial indication expansion.

None of which makes the story bulletproof. This is a single-molecule franchise; the Tyvaso line alone is now a majority of revenue, which is concentration risk by any definition. And the moat is being tested in real time. Liquidia’s Yutrepia a competing inhaled treprostinil dry powder built on a different particle-engineering platform won final FDA approval in May 2025. But Martine Rothblatt appears to be going back to her organizing principle, one of finding the corridors of indifference and running. It now points at the largest unmet market in medicine: the supply of organs themselves.

More than 100,000 Americans sit on the transplant waitlist; roughly 90,000 of them need a kidney, and on the order of a dozen die each day waiting for one. Behind them are some 800,000 people with end-stage renal disease, most of whom will never reach the list. Their alternative is dialysis, which costs roughly $90,000 to $100,000 per patient per year, consumes more than $30 billion of Medicare spending annually, and carries a prognosis worse than many cancers: about one in five patients dies within the first year, and median survival from the start of dialysis is around three years, almost exactly the prognosis untreated PAH carried in the 1990s. The demand has never been the problem but the supply is.

Xenotransplantation, moving an organ from one species into another, is an old idea that failed for a specific, brutal reason. Human blood carries preformed antibodies against a sugar, galactose-α-1,3-galactose, that coats pig cells. Transplant an unmodified pig organ and those antibodies bind within minutes, the complement cascade fires, and the graft is destroyed in hyperacute rejection before it can do any work. Behind HAR are also concerns about porcine endogenous retroviruses woven into the pig genome, which might cross into humans, and porcine cytomegalovirus, implicated in the failure of the earliest attempts.

CRISPR changed the arithmetic. Gene editing made it possible to knock out the pig genes that trigger HAR and to add human genes that tell the recipient's immune system to stand down.

United Therapeutics has been at this longer than almost anyone. It acquired Revivicor, a gene-editing pig company, in 2011, and has run three organ programs since: the UKidney, the UHeart, and the UThymoKidney. When the first gene-edited pig hearts were transplanted into living people, at the University of Maryland, into David Bennett in 2022 and Lawrence Faucette in 2023, the hearts came from Revivicor's pigs. Both men died within weeks to a couple of months, but each heart worked for a time, which had never happened before. At NYU, Robert Montgomery's team used Revivicor kidneys, including one given to Towana Looney in late 2024 that functioned for 130 days, until her doctors lowering her immunosuppression to treat an unrelated infection, triggered the acute rejection that forced the kidney's removal in April 2025.

If we step back, a familiar pattern emerges. Xenotransplantation is exactly what epoprostenol was in 1994: real, fragile, and not yet a product. United Therapeutics has spent its entire existence in the gap between ‘this can work’ and ‘this is a dream’ and Rothblatt has crossed that gap before. Whether she can cross it again, on the widest unmet market in medicine, is the question worth real money. That's the deep dive I'll do next.